*Geochemical data of selected gypsum samples of the Fat'ha Formation in Sheikh Ibrahim section.*

**269**

sum rocks.

*Ibrahim section.*

**Figure 14.**

**5. Discussion and conclusions**

*Middle Miocene Evaporites from Northern Iraq: Petrography, Geochemistry, and Cap Rock…*

**Sample Description Porosity (%)** K1 Pure anhydrite 0.25 K2 Anhydrite with impurities 4.0 K3 Limestone 17 T1 Surface gypsum sample 0.9

gypsum beds. This gypsum beds may represent seal or cap rocks of the Fat'ha Formation (**Figure 14**). Permeability data show that it is low in the studied gyp

*Core and field images showing (A) core from Kirkuk well illustrates the nature of contact between the porous bitumen-rich limestone in the lower part and compact pore-free anhydrite bed; note some early disseminated hydrocarbons in the host materials (arrows). (B) Bed of nodular gypsum hosting brown hydrocarbon-rich matrix, Sheikh Ibrahim section. (C) Bitumen-rich limestone overlaid by hydrocarbon-free gypsum bed, Sheikh* 

Evaporites are indicative for arid continental environments [29], and their formation in sedimentary basins depends mostly on the connection of this basin with oceanic or sea water. Where this connection is periodically interrupted within


*DOI: http://dx.doi.org/10.5772/intechopen.92566*

**Table 2.**

*Porosity data for selected samples.*

*Middle Miocene Evaporites from Northern Iraq: Petrography, Geochemistry, and Cap Rock… DOI: http://dx.doi.org/10.5772/intechopen.92566*


**Table 2.**

*Geochemistry*

**268**

**Gypsum** 

**SiO2 (%)**

**Al O (%) 2**

**TiO2 (%)**

**MnO (%)**

**MgO (%)**

**CaO (%)**

**K O (%) 2**

**Na O (%) 2**

**Fe**

**O2 3 (%)**

**P O2 5 (%)**

**SO3 (%)**

**Ba** 

**Sr ppm**

**ppm**

**type**

Nodular Laminated

Massive Gypsumanhydrite

1.8

1.4

0.01

0.01

0.3

18.4

0.01

0.08

0.03

0.03

47

4.6

615

mosaic

Brown

2.2

0.7

0.03

0.01

0.7

18.2

0.02

0.2

0.04

0.03

48

4.5

201

massive

Wispy Selenite

**Table 1.**

2.4

0.7

0.03 *Geochemical data of selected gypsum samples of the Fat'ha Formation in Sheikh Ibrahim section.*

0.01

0.7

18.6

0.03

0.2

0.05

0.03

48

1.8

83

2.9

0.9

0.03

0.01

1.8

19

0.07

0.1

0.11

0.03

46

1.2

113

1.6

0.5

0.02

0.01

0.4

18.2

0.01

0.14

0.02

0.03

48

0.6

245

3.0

0.9

0.03

0.01

1.9

19.5

0.08

0.1

0.1

0.03

46

1.4

110

1.4

0.4

0.02

0.01

0.2

18

0.01

0.1

0.02

0.03

48

2.8

246

*Porosity data for selected samples.*

#### **Figure 14.**

*Core and field images showing (A) core from Kirkuk well illustrates the nature of contact between the porous bitumen-rich limestone in the lower part and compact pore-free anhydrite bed; note some early disseminated hydrocarbons in the host materials (arrows). (B) Bed of nodular gypsum hosting brown hydrocarbon-rich matrix, Sheikh Ibrahim section. (C) Bitumen-rich limestone overlaid by hydrocarbon-free gypsum bed, Sheikh Ibrahim section.*

gypsum beds. This gypsum beds may represent seal or cap rocks of the Fat'ha Formation (**Figure 14**). Permeability data show that it is low in the studied gypsum rocks.

#### **5. Discussion and conclusions**

Evaporites are indicative for arid continental environments [29], and their formation in sedimentary basins depends mostly on the connection of this basin with oceanic or sea water. Where this connection is periodically interrupted within arid settings, this may led to high evaporation of the basin and cyclic deposition of evaporitic successions in the sedimentary basins [31].

Lithofacies analysis of the studied evaporates revealed the presence of nodular and massive gypsum/anhydrite, laminated gypsum and secondary selenite, and satin spar lithofacies with several sublithofacies; these are representative of relict basin evaporate deposition based on their tectonic setting which they deposited during closure periods of the Neo-Tethys basin on the northern Arabian Plate passive margins [32].

Due to wide distribution of the Fat'ha Formation, several ideas have been proposed for the depositional cycles of gypsum formation. Semi-restricted lagoonal environments such as lakes which were connected to the open sea through narrow channels coincide with the brine-filled basin model suggested by [33, 34], while sabkha or supratidal flat depositional setting and coastal or inland sabkhas with semiarid shallow lagoon were favored by [18, 32], respectively. These models could be comparable with the Messinian basin evaporites of the Mediterranean [35] and Middle Miocene (Badenian) basin-marginal evaporites of the Carpathian Foredeep basin of western Ukraine [36].

Petrographic investigation of the gypsum and anhydritic rocks of the Middle Miocene Fat'ha Formation has revealed that nodular gypsum is the dominant type and is composed of granular integrated gypsum texture with evidence of recrystallization, whereas alabastrine texture is the common type in the laminated gypsum. Secondary gypsum of selenite and satin spar shows alabastrine, fine to coarse fibrous, and porphyroblastic textures with the alabastrine type being predominant.

Nodular gypsum was deposited in a very shallow, arid, and semi-restricted lagoonal environment which has undergone influx and reflux processes, while laminated gypsum may represent pulses of freshwater into the lagoonal basin of Fat'ha Formation.

The chemical composition of selected nodular, laminated, and secondary (selenite) and mosaic gypsum shows low values of strontium (Sr) in the secondary and laminated types due to their secondary origin by the hydration from the original anhydrite through which Sr. in the original anhydrite was expelled. The impoverishment in Sr. commonly occurs in secondary-type gypsum as compared with primary ones [37]. High values in some of gypsum types (see **Table 1**) may be attributed to diagenetic processes and the sea salinity.

Hydrocarbons present mainly in the limestone beds underlie gypsum beds and in materials hosting gypsum nodules. Porous granular texture of these materials allowed hydrocarbon inclusion, later on, during compaction and growth of nodular to compound mosaic due to recrystallization resulted in prevent hydrocarbon dissemination, then these materials were locked in these materials and partly in accompanied gypsum nodules. These results were revealed by low porosity and permeability of the studied gypsum nodules as compared to those of the limestone beds.

**271**

**Author details**

Ali I. Al-Juboury1

\*, Rana A. Mahmood2

\*Address all correspondence to: alialjubory@yahoo.com

provided the original work is properly cited.

1 Department of Geology, College of Sciences, University of Mosul, Mosul, Iraq

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

2 College of Electrical Engineering, Ninevah University, Mosul, Iraq

and Abulaziz M. Al-Hamdani1

*Middle Miocene Evaporites from Northern Iraq: Petrography, Geochemistry, and Cap Rock…*

*DOI: http://dx.doi.org/10.5772/intechopen.92566*

*Middle Miocene Evaporites from Northern Iraq: Petrography, Geochemistry, and Cap Rock… DOI: http://dx.doi.org/10.5772/intechopen.92566*

#### **Author details**

*Geochemistry*

sive margins [32].

Fat'ha Formation.

basin of western Ukraine [36].

diagenetic processes and the sea salinity.

arid settings, this may led to high evaporation of the basin and cyclic deposition of

Due to wide distribution of the Fat'ha Formation, several ideas have been proposed for the depositional cycles of gypsum formation. Semi-restricted lagoonal environments such as lakes which were connected to the open sea through narrow channels coincide with the brine-filled basin model suggested by [33, 34], while sabkha or supratidal flat depositional setting and coastal or inland sabkhas with semiarid shallow lagoon were favored by [18, 32], respectively. These models could be comparable with the Messinian basin evaporites of the Mediterranean [35] and Middle Miocene (Badenian) basin-marginal evaporites of the Carpathian Foredeep

Petrographic investigation of the gypsum and anhydritic rocks of the Middle Miocene Fat'ha Formation has revealed that nodular gypsum is the dominant type and is composed of granular integrated gypsum texture with evidence of recrystallization, whereas alabastrine texture is the common type in the laminated gypsum. Secondary gypsum of selenite and satin spar shows alabastrine, fine to coarse fibrous, and porphyroblastic textures with the alabastrine type being predominant. Nodular gypsum was deposited in a very shallow, arid, and semi-restricted lagoonal environment which has undergone influx and reflux processes, while laminated gypsum may represent pulses of freshwater into the lagoonal basin of

The chemical composition of selected nodular, laminated, and secondary (selenite) and mosaic gypsum shows low values of strontium (Sr) in the secondary and laminated types due to their secondary origin by the hydration from the original anhydrite through which Sr. in the original anhydrite was expelled. The impoverishment in Sr. commonly occurs in secondary-type gypsum as compared with primary ones [37]. High values in some of gypsum types (see **Table 1**) may be attributed to

Hydrocarbons present mainly in the limestone beds underlie gypsum beds and in materials hosting gypsum nodules. Porous granular texture of these materials allowed hydrocarbon inclusion, later on, during compaction and growth of nodular to compound mosaic due to recrystallization resulted in prevent hydrocarbon dissemination, then these materials were locked in these materials and partly in accompanied gypsum nodules. These results were revealed by low porosity and permeability of the studied gypsum nodules as compared to those of the lime-

Lithofacies analysis of the studied evaporates revealed the presence of nodular and massive gypsum/anhydrite, laminated gypsum and secondary selenite, and satin spar lithofacies with several sublithofacies; these are representative of relict basin evaporate deposition based on their tectonic setting which they deposited during closure periods of the Neo-Tethys basin on the northern Arabian Plate pas-

evaporitic successions in the sedimentary basins [31].

**270**

stone beds.

Ali I. Al-Juboury1 \*, Rana A. Mahmood2 and Abulaziz M. Al-Hamdani1

1 Department of Geology, College of Sciences, University of Mosul, Mosul, Iraq

2 College of Electrical Engineering, Ninevah University, Mosul, Iraq

\*Address all correspondence to: alialjubory@yahoo.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **References**

[1] Yi-gang Z. Cool shallow origin of petroleum-microbial genesis and subsequent degradation. Journal of Petroleum Geology. 1981;**3**:427-444

[2] Warren JK. Evaporite Sedimentology: Importance in Hydrocarbon Accumulation. Englewood Cliffs: Prentice Hall; 2014. p. 285

[3] Al-Juboury AI, McCann T. The middle Miocene Fat'ha (lower Fars) Formation of Iraq. GeoArabia. 2008;**13**(3):141-174

[4] Dunnington HV. Generation, accumulation and dissipation of oil in northern Iraq. In: Weeks LG, editor. Habitat of Oil. USA: American Association of Petroleum Geologists; 1958. pp. 1194-1251

[5] Buday T. The regional of Iraq. In: Stratigraphy and Palaeogeography. Vol. 1. Baghdad, Iraq: State Organization for Minerals; 1980. p. 445

[6] Goff JC, Jones RW, Horbury AD. Cenozoic basin evolution of the northern part of the Arabian Plate and its control on hydrocarbon habitat. In: Al-Husseini MI, editor. Middle East Petroleum Geosciences Conference, GEO'94. Vol. 1. Bahrain: Gulf PetroLink; 1995. pp. 402-412

[7] Numan NMS. A plate tectonic scenario for the Phanerozoic succession in Iraq. Journal of the Geological Society of Iraq. 1997;**30**:85-110

[8] Al-Juboury AI, Al-Naqib SQ, Al-Juboury AMS. Sedimentology, mineralogy and depositional environments of the clastic units, Fat'ha Formation (middle Miocene), south of Mosul, Iraq. Dirasat, Pure Sciences, Jordan. 2001;**28**:80-105

[9] Van Bellen RC, Dunnington H, Wetzel R, Morton DM. Lexique Stratigraphique International. Paris: Centre National Recherché Scientifique, Fasc 10a, Iraq; 1959. p. 333

[10] Metwalli MH, Philip G, Moussly MM. Petroleum-bearing formations in northeastern Syria and northern Iraq. American Association of Petroleum Geologists Bulletin. 1974;**58**:1781-1796

[11] Beydoun ZR. Arabian plate hydrocarbon geology and potential: A plate tectonic approach. American Association of Petroleum Geologists, Studies in Geology. 1991;**33**:1-77

[12] Sharland PR, Archer R, Casey DM, Davies RB, Hall SH, Heward AP, et al. Arabian Plate Sequence Stratigraphy. Bahrain: GeoArabia Special Publication 2, Gulf PetroLink; 2001. p. 371

[13] Buday T, Jassim SZ. The Regional Geology of Iraq, Tectonism, Magmatism and Metamorphism. Baghdad, Iraq: Publication of the Geological Survey of Iraq; 1987. p. 352

[14] Al-Sharhan AS, Nairn AEM. Sedimentary Basins and Petroleum Geology of the Middle East. Amsterdam: Elsevier; 1997. p. 843

[15] Jordan TE. Thrust loads and foreland basin evolution, cretaceous, western United States. Bulletin of the American Association of Petroleum Geologists. 1981;**65**:2506-2520

[16] Allen PA, Homewood P, Williams GD. Foreland basins: An introduction. In: Allen PA, Homewood P, editors. Foreland Basins. Vol. 8. International Association of Sedimentologists, Special Publication. Berlin, New York: Springer; 1986. pp. 3-12

[17] Al-Sawaf FDS. Sulfate reduction and sulfur deposition in the lower Fars formation, northern Iraq. Economic Geology. 1977;**72**:608-618

[18] Shawkat MG, Tucker ME. 1978. Stromatolites and sabkha cycles from the lower Fars formation (Miocene)

**273**

*Middle Miocene Evaporites from Northern Iraq: Petrography, Geochemistry, and Cap Rock…*

[29] Boggs SJ. Principles of Sedimentology and Stratigraphy. New Jersey: Pearson

[30] Shearman DJ, Fuller JG. Anhydrite diagenesis, calcitization and organic laminates, Winnipegosis formation, middle Devonian, Saskatchewan. Bulletin the Canadian Petroleum

Prentice-Hall; 2006. p. 662

Geology. 1969;**17**:496-525

[Unpublished]

p. 175 [Unpublished]

and Mining. 2019;**8**:241-261

[35] Rouchy JM, Taberner C, Blanc-Valleron MM, Sprovieri R, Russell M, Pierre C, et al. Sedimentary

and diagenetic markers of the

[31] Nichols G. Sedimentology and Stratigraphy. Oxford: Blackwell Scientific Publications; 1999. p. 355

[32] Mustafa AAM. Sedimentological studies of the lower fars formation in the Sinjar Basin, Iraq [MSc thesis]. Iraq: Mosul University; 1980; p. 243

[33] Sulayman MD. Geochemistry, petrology, origin and diagenesis of gypsum rocks of lower fars formation at Butma West area, northern Iraq [MSc thesis]. Iraq: Mosul University; 1990;

[34] Jassim RZ. Gypsum deposits in Iraq: An overview. Iraqi Bulletin of Geology

restriction in a marine basin: The Lorca Basin (SE Spain) during the Messinian. Sedimentary Geology. 1998;**121**:23-55

[36] Peryt TM. Gypsum facies transitions in basin-marginal evaporites: Middle Miocene (Badenian) of West Ukraine. Sedimentology. 2001;**48**:1103-1119

[37] Playa E, Orti F, Rosell FL. Marine to non-marine sedimentation in the upper Miocene evaporites of the eastern Betics, SE Spain: Sedimentological and geochemical evidence. Sedimentary Geology. 2000;133(1-2):135-166

*DOI: http://dx.doi.org/10.5772/intechopen.92566*

of Iraq. Geologische Rundschau.

[19] Holliday DW. Origin of lower Eocene gypsum-anhydrite rocks, south eastern St Andrew, Jamaica. Applied Earth Science. 1971;**80**:305-315

[20] Maiklem WR, Bebout DC, Glaister RP. Classification of anhydrite—A practical approach. Bulletin of Canadian Petroleum Geology. 1969;**17**:194-233

Edu\_Classif\_Evahtml

[21] Meyer FO. Anhydrite Classification According to Structure. 2005. Available from: http://www.crienterprises.com/

[22] Sarg JF. Petrology of the carbonateevaporite facies transition of the seven Rivers formation (Guadalupian, Permian), Southeast New Mexico. Journal of Sedimentary Petrology. 1981;**51**:73-93

[23] Paz JDS, Rossetti DF. Petrography of gypsum-bearing facies of the Codo formation (late Aptian), northern Brazil. Annals of the Brazilian Academy

of Science. 2006;**78**(3):557-572

Geology. 2007;**33**(2):249-260

Geologica. 2003;**XL**(2):59-66

diagenesis of gypsum and anhydrite. Journal of Sedimentray Research.

[27] Warren JK. Evaporites: Sediments, Resources and Hydrocarbons. Berlin, New York: Springer; 2006. p. 1035

[28] Blatt H, Middeleton G, Murray R. Origin of Sedimentary Rocks. New Jersey: Prentice-Hall Inc.; 1972. p. 634

[26] Murray RC. Origin and

1964;**34**(3):512-523

[24] Orti F, Rosell L. The Ninyerola gypsum unit: An example of cyclic, lacustrine sedimentation (middle Miocene, E Spain). Journal of Iberian

[25] Bedelean H. Considerations on the parent material in the soil developed on the evaporate deposits from Stana.

1978;**67**:1-14

*Middle Miocene Evaporites from Northern Iraq: Petrography, Geochemistry, and Cap Rock… DOI: http://dx.doi.org/10.5772/intechopen.92566*

of Iraq. Geologische Rundschau. 1978;**67**:1-14

[19] Holliday DW. Origin of lower Eocene gypsum-anhydrite rocks, south eastern St Andrew, Jamaica. Applied Earth Science. 1971;**80**:305-315

[20] Maiklem WR, Bebout DC, Glaister RP. Classification of anhydrite—A practical approach. Bulletin of Canadian Petroleum Geology. 1969;**17**:194-233

[21] Meyer FO. Anhydrite Classification According to Structure. 2005. Available from: http://www.crienterprises.com/ Edu\_Classif\_Evahtml

[22] Sarg JF. Petrology of the carbonateevaporite facies transition of the seven Rivers formation (Guadalupian, Permian), Southeast New Mexico. Journal of Sedimentary Petrology. 1981;**51**:73-93

[23] Paz JDS, Rossetti DF. Petrography of gypsum-bearing facies of the Codo formation (late Aptian), northern Brazil. Annals of the Brazilian Academy of Science. 2006;**78**(3):557-572

[24] Orti F, Rosell L. The Ninyerola gypsum unit: An example of cyclic, lacustrine sedimentation (middle Miocene, E Spain). Journal of Iberian Geology. 2007;**33**(2):249-260

[25] Bedelean H. Considerations on the parent material in the soil developed on the evaporate deposits from Stana. Geologica. 2003;**XL**(2):59-66

[26] Murray RC. Origin and diagenesis of gypsum and anhydrite. Journal of Sedimentray Research. 1964;**34**(3):512-523

[27] Warren JK. Evaporites: Sediments, Resources and Hydrocarbons. Berlin, New York: Springer; 2006. p. 1035

[28] Blatt H, Middeleton G, Murray R. Origin of Sedimentary Rocks. New Jersey: Prentice-Hall Inc.; 1972. p. 634

[29] Boggs SJ. Principles of Sedimentology and Stratigraphy. New Jersey: Pearson Prentice-Hall; 2006. p. 662

[30] Shearman DJ, Fuller JG. Anhydrite diagenesis, calcitization and organic laminates, Winnipegosis formation, middle Devonian, Saskatchewan. Bulletin the Canadian Petroleum Geology. 1969;**17**:496-525

[31] Nichols G. Sedimentology and Stratigraphy. Oxford: Blackwell Scientific Publications; 1999. p. 355

[32] Mustafa AAM. Sedimentological studies of the lower fars formation in the Sinjar Basin, Iraq [MSc thesis]. Iraq: Mosul University; 1980; p. 243 [Unpublished]

[33] Sulayman MD. Geochemistry, petrology, origin and diagenesis of gypsum rocks of lower fars formation at Butma West area, northern Iraq [MSc thesis]. Iraq: Mosul University; 1990; p. 175 [Unpublished]

[34] Jassim RZ. Gypsum deposits in Iraq: An overview. Iraqi Bulletin of Geology and Mining. 2019;**8**:241-261

[35] Rouchy JM, Taberner C, Blanc-Valleron MM, Sprovieri R, Russell M, Pierre C, et al. Sedimentary and diagenetic markers of the restriction in a marine basin: The Lorca Basin (SE Spain) during the Messinian. Sedimentary Geology. 1998;**121**:23-55

[36] Peryt TM. Gypsum facies transitions in basin-marginal evaporites: Middle Miocene (Badenian) of West Ukraine. Sedimentology. 2001;**48**:1103-1119

[37] Playa E, Orti F, Rosell FL. Marine to non-marine sedimentation in the upper Miocene evaporites of the eastern Betics, SE Spain: Sedimentological and geochemical evidence. Sedimentary Geology. 2000;133(1-2):135-166

**272**

*Geochemistry*

**References**

[1] Yi-gang Z. Cool shallow origin of petroleum-microbial genesis and subsequent degradation. Journal of Petroleum Geology. 1981;**3**:427-444

Importance in Hydrocarbon Accumulation. Englewood Cliffs:

[3] Al-Juboury AI, McCann T. The middle Miocene Fat'ha (lower Fars) Formation of Iraq. GeoArabia.

[4] Dunnington HV. Generation, accumulation and dissipation of oil in northern Iraq. In: Weeks LG, editor. Habitat of Oil. USA: American Association of Petroleum Geologists;

[5] Buday T. The regional of Iraq. In: Stratigraphy and Palaeogeography. Vol. 1. Baghdad, Iraq: State Organization for

[6] Goff JC, Jones RW, Horbury AD. Cenozoic basin evolution of the northern part of the Arabian Plate and its control on hydrocarbon habitat. In: Al-Husseini MI, editor. Middle East Petroleum Geosciences Conference, GEO'94. Vol. 1. Bahrain: Gulf PetroLink;

[7] Numan NMS. A plate tectonic scenario for the Phanerozoic succession in Iraq. Journal of the Geological Society

[8] Al-Juboury AI, Al-Naqib SQ, Al-Juboury AMS. Sedimentology, mineralogy and depositional

[9] Van Bellen RC, Dunnington H, Wetzel R, Morton DM. Lexique Stratigraphique International. Paris:

environments of the clastic units, Fat'ha Formation (middle Miocene), south of Mosul, Iraq. Dirasat, Pure Sciences,

Prentice Hall; 2014. p. 285

2008;**13**(3):141-174

1958. pp. 1194-1251

Minerals; 1980. p. 445

1995. pp. 402-412

of Iraq. 1997;**30**:85-110

Jordan. 2001;**28**:80-105

[2] Warren JK. Evaporite Sedimentology:

Centre National Recherché Scientifique,

[10] Metwalli MH, Philip G, Moussly MM.

[12] Sharland PR, Archer R, Casey DM, Davies RB, Hall SH, Heward AP, et al. Arabian Plate Sequence Stratigraphy. Bahrain: GeoArabia Special Publication

[13] Buday T, Jassim SZ. The Regional Geology of Iraq, Tectonism, Magmatism and Metamorphism. Baghdad, Iraq: Publication of the Geological Survey of

Fasc 10a, Iraq; 1959. p. 333

Petroleum-bearing formations in northeastern Syria and northern Iraq. American Association of Petroleum Geologists Bulletin. 1974;**58**:1781-1796

[11] Beydoun ZR. Arabian plate hydrocarbon geology and potential: A plate tectonic approach. American Association of Petroleum Geologists, Studies in Geology. 1991;**33**:1-77

2, Gulf PetroLink; 2001. p. 371

[14] Al-Sharhan AS, Nairn AEM. Sedimentary Basins and Petroleum Geology of the Middle East. Amsterdam: Elsevier; 1997. p. 843

[15] Jordan TE. Thrust loads and foreland basin evolution, cretaceous, western United States. Bulletin of the American Association of Petroleum Geologists. 1981;**65**:2506-2520

[16] Allen PA, Homewood P, Williams GD. Foreland basins: An introduction. In: Allen PA, Homewood P, editors. Foreland Basins. Vol. 8. International Association of Sedimentologists, Special Publication. Berlin, New York: Springer; 1986. pp. 3-12

[17] Al-Sawaf FDS. Sulfate reduction and sulfur deposition in the lower Fars formation, northern Iraq. Economic

[18] Shawkat MG, Tucker ME. 1978. Stromatolites and sabkha cycles from the lower Fars formation (Miocene)

Geology. 1977;**72**:608-618

Iraq; 1987. p. 352

**275**

**1. Introduction**

**Chapter 14**

Bioclastic Deposits in the NW

Tyrrhenian Sea, Italy): A Focus

on New Sedimentological and

Stratigraphic Data around the

Bioclastic deposits in the Gulf of Naples have been studied and compared based on new sedimentological and stratigraphic data, particularly referring to the rhodolith layers. They represent detrital facies deriving mainly from in situ rearrangement processes of organogenic material on rocky sea bottoms. These deposits are composed of medium-coarse-grained sands and bioclastic gravels in a scarce pelitic matrix and crop out at the sea bottom in a portion of the inner shelf located at water depths between −20 m and −50 m. Below water depths of −30 m the bioclastic deposits are rhodolith, characterized by gravels and lithoclastic sands. Rhodolith deposits are often found near the *Posidonia oceanica* meadows and/or in protected areas near the rocky outcrops. The Ischia Bank represents an excellent natural laboratory for studying the rhodolith layers. On the Ischia Bank, below the *Posidonia oceanica* meadow, both bioclastic sands immersed in a muddy matrix and volcaniclastic gravels were sampled. Both the Mollusk shells and the volcaniclastic fragments, where the contribution of the silty and sandy fractions is lower than 20%, were colonized by some species of red algae, while in the marine areas with a

**Keywords:** bioclastic deposits, rhodolith layers, *Posidonia oceanica* meadow,

Rhodolith or maërl deposits consist of either alive or dead aggregations of coralline algae, which blanket wide coastal zones in the present-day oceans [1–3] and represent shared facies in carbonate platform settings. In some cases, the rhodolith layers indicate the transition from bioclastic-to-rocky sea bottoms, but they can form also on mobile sea bottoms [3–5]. The rhodoliths are the main components of the rhodalgal skeletal assemblage that characterizes the carbonate production in the oligophotic zone of Cenozoic and modern carbonate platforms [4, 6–10]. In

Gulf of Naples (Southern

Island of Ischia

low gradient a maërl facies was deposited.

sedimentological analyses, Gulf of Naples

*Gemma Aiello*

**Abstract**

#### **Chapter 14**

Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New Sedimentological and Stratigraphic Data around the Island of Ischia

*Gemma Aiello*

### **Abstract**

Bioclastic deposits in the Gulf of Naples have been studied and compared based on new sedimentological and stratigraphic data, particularly referring to the rhodolith layers. They represent detrital facies deriving mainly from in situ rearrangement processes of organogenic material on rocky sea bottoms. These deposits are composed of medium-coarse-grained sands and bioclastic gravels in a scarce pelitic matrix and crop out at the sea bottom in a portion of the inner shelf located at water depths between −20 m and −50 m. Below water depths of −30 m the bioclastic deposits are rhodolith, characterized by gravels and lithoclastic sands. Rhodolith deposits are often found near the *Posidonia oceanica* meadows and/or in protected areas near the rocky outcrops. The Ischia Bank represents an excellent natural laboratory for studying the rhodolith layers. On the Ischia Bank, below the *Posidonia oceanica* meadow, both bioclastic sands immersed in a muddy matrix and volcaniclastic gravels were sampled. Both the Mollusk shells and the volcaniclastic fragments, where the contribution of the silty and sandy fractions is lower than 20%, were colonized by some species of red algae, while in the marine areas with a low gradient a maërl facies was deposited.

**Keywords:** bioclastic deposits, rhodolith layers, *Posidonia oceanica* meadow, sedimentological analyses, Gulf of Naples

#### **1. Introduction**

Rhodolith or maërl deposits consist of either alive or dead aggregations of coralline algae, which blanket wide coastal zones in the present-day oceans [1–3] and represent shared facies in carbonate platform settings. In some cases, the rhodolith layers indicate the transition from bioclastic-to-rocky sea bottoms, but they can form also on mobile sea bottoms [3–5]. The rhodoliths are the main components of the rhodalgal skeletal assemblage that characterizes the carbonate production in the oligophotic zone of Cenozoic and modern carbonate platforms [4, 6–10]. In

contrast with the chloralgal and molechfor assemblages, respectively characterized by the lacking of hermatipic corals and by benthic foraminifers, mollusks, echinoids and bryozoans the rhodalgal assemblage is mainly composed of coralline algae [4]. The zonation of benthic assemblages of the Mediterranean sea performed by Peres and Picard [11] has improved the knowledge on lithology and facies interpretation of rhodolith layers (**Figure 1**). In the Mediterranean sea the bioclastic deposits occur at water depths ranging between – 40 m and – 100 m ("Détritique Cotier" of Peres and Picard; **Figure 1**) [11]. In particular, the rhodolith layers are concentrated in the marine sectors exposed to strong current regimes, such as the top of plateaus or banks. The main components of the "Détritique Cotier" are composed of the reworking and deposition of benthic communities on both mobile sea bottoms (biocoenosis of the "Détritique Cotier") and on hard sea bottoms (biocoenosis of the "Détritique Du Large"), more than the assemblages of *Posidonia oceanica* meadows and maërl deposits. As a consequence of the Holocene sea level rise the deep seafloor was covered by relict and drowned sediments ("Détritique Du Large"; **Figure 1**), characterized by low rates of sedimentation and by the occurrence of glauconite.

The global dominance of coralline algae forming the rhodalgal lithofacies from the Burdigalian to the Early Tortonian has been demonstrated based on stratigraphic data [12]. In particular, during this time interval the rhodalgal lithofacies has reached peak abundance, replacing the coral reef deposits. The prevalence of coralline algae over coral reefs was suggested as being controlled by the enhancement of the trophic resources and associated with an increase of biological productivity to a global scale [12]. This evidence was shown by geochemical data computed on carbon isotopes. During the Middle Miocene the rhodalgal lithofacies increased its extension, due to the upwelling triggered by the establishment of East Antarctic Ice Sheet led to enhanced. These stratigraphic studies performed to a global scale have confirmed the importance of rhodolith deposits as proxies of past oceanographic conditions [12].

This chapter provides new sedimentological and stratigraphic data on the bioclastic deposits and in particular on the rhodolith deposits, occurring in the offshore island of Ischia (Gulf of Naples, Italy); it is based on data coming from sea bottom samples collected during the CARG project aimed at the realization and informatization of the marine geological cartography of the geological sheet No. 464 [13]. The island of Ischia represents the emerged part of a large volcanic field, which extends from the island of Procida to the submerged volcanoes of the western offshore of Ischia [13–17].

The occurrence of rodolith deposits in the Gulf of Naples has been suggested by several studies [18–29]. The sedimentological analysis of the sea bottom samples,

#### **Figure 1.**

*Sketch diagram showing the main biocenosis of mobile sea bottoms (modified after Carannante et al. [4]).*

**277**

subtropical seagrass meadows.

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New…*

Previous studies focused on rhodolith deposits in the marine areas of the Gulf of Naples, in particular Nisida-Posillipo (Nisida Bank and La Cavallara saddle) and the Gulf of Pozzuoli (Miseno Bank), while only a single sample came from the Ischia Bank [29]. Otherwise the present work is based on a dense network of samples collected in the Ischia offshore. Moreover, the recognition of bioclastic deposits on some Sparker seismic profiles let us to perform a qualitative calibration of data

together with the realization of geological cartography at the 1: 10.000 scale has allowed to study the bioclastic deposits and in particular, the rhodolith deposits occurring in the Ischia offshore. Moreover, the seismo-stratigraphic data have allowed for the calibration of the rhodalgal deposits on previously interpreted

Rhodolith deposits have previously been reported in the offshore of Ischia [29–31]. In particular, Toscano et al. [29] have shown the variability of the rhodalgal facies in the Gulfs of Naples and Pozzuoli, which is closely connected with the location of the platform, with the morpho-bathymetric structure, with the morphology of the sea bottom and with the hydrodynamic conditions on the submerged volcanic banks (Nisida, Miseno and Pentapalummo Banks; Ischia Bank). The top of these submerged volcanic banks is located at water depths of −28/−30 m and is overlain by the *Posidonia oceanica* meadow, growing up to water depths of −35/−40 m. In the marine areas where the *Posidonia meadow* is lacking, the action of the currents has

The rhodolith deposits form well-developed layers. They often lie on a sandygravelly sea bottom formed by both the shells of mollusks that live in the meadow and by the abundant pyroclastic granules, that derive from the erosion of sea bottoms on which the *Posidonia* meadow grows up [32–34]. Brandano and Civitelli [33] have analyzed the interactions between carbonate and siliciclastic sedimentation on the Pontinian shelf of the Tyrrhenian sea focusing on the relationships between the carbonate deposits and the *Posidonia* meadow. Six sedimentary facies and ten microfacies have been identified using the component analysis, the grain-size percentage, the sorting, the carbonate content and the rate of authigenic mineralization. The maërl deposits and the skeletal sands are located in the circalittoral zone (82 m to 112 m of water depth), also displaying relict facies. These authors have highlighted that the *Posidonia* meadows represent the main facies of the mobile infra-littoral substratum. In the area surrounding the Pontinian islands the *Posidonia* meadows, ranging at water depths between 30 m and 40 m water depth show a rich epiphytic flora and fauna, living on the seagrass leaves and rhizomes. The unattached coralline algal branches gravel facies indicates the environment representing the highest carbonate production rate. This facies consists of red algae (rhodalgal association) that are the main carbonate-producing biota in the Mediterranean. Brandano et al. [34] have highlighted that the seagrasses represent important carbonate factories, being characterized by important carbonate producing biota, as epiphytes on the leaves and infaunal forms. These authors have determined the skeletal assemblage of both modern (Maldivian and western Mediterranean) and fossil seagrass examples (Eocene; Apula and Oman carbonate platforms and Oligocene; Malta platform). In both Maldivian and western Mediterranean the bioclastic deposits are mainly composed of calcareous algae and foraminifera. As a difference, in the tropical setting they are represented by green algae (*Halimeda*), while in the Mediterranean they consist of red algae [34]. The performed stratigraphic study has shown that the green algae–foralgal assemblage is typical of tropical seagrass meadows. On the contrary, the red algae-foralgal assemblage is typical of tropical to

controlled the formation of large fields of sandy ripples [32].

*DOI: http://dx.doi.org/10.5772/intechopen.95083*

seismic Sparker profiles [15].

coming from sampling.

together with the realization of geological cartography at the 1: 10.000 scale has allowed to study the bioclastic deposits and in particular, the rhodolith deposits occurring in the Ischia offshore. Moreover, the seismo-stratigraphic data have allowed for the calibration of the rhodalgal deposits on previously interpreted seismic Sparker profiles [15].

Previous studies focused on rhodolith deposits in the marine areas of the Gulf of Naples, in particular Nisida-Posillipo (Nisida Bank and La Cavallara saddle) and the Gulf of Pozzuoli (Miseno Bank), while only a single sample came from the Ischia Bank [29]. Otherwise the present work is based on a dense network of samples collected in the Ischia offshore. Moreover, the recognition of bioclastic deposits on some Sparker seismic profiles let us to perform a qualitative calibration of data coming from sampling.

Rhodolith deposits have previously been reported in the offshore of Ischia [29–31]. In particular, Toscano et al. [29] have shown the variability of the rhodalgal facies in the Gulfs of Naples and Pozzuoli, which is closely connected with the location of the platform, with the morpho-bathymetric structure, with the morphology of the sea bottom and with the hydrodynamic conditions on the submerged volcanic banks (Nisida, Miseno and Pentapalummo Banks; Ischia Bank). The top of these submerged volcanic banks is located at water depths of −28/−30 m and is overlain by the *Posidonia oceanica* meadow, growing up to water depths of −35/−40 m. In the marine areas where the *Posidonia meadow* is lacking, the action of the currents has controlled the formation of large fields of sandy ripples [32].

The rhodolith deposits form well-developed layers. They often lie on a sandygravelly sea bottom formed by both the shells of mollusks that live in the meadow and by the abundant pyroclastic granules, that derive from the erosion of sea bottoms on which the *Posidonia* meadow grows up [32–34]. Brandano and Civitelli [33] have analyzed the interactions between carbonate and siliciclastic sedimentation on the Pontinian shelf of the Tyrrhenian sea focusing on the relationships between the carbonate deposits and the *Posidonia* meadow. Six sedimentary facies and ten microfacies have been identified using the component analysis, the grain-size percentage, the sorting, the carbonate content and the rate of authigenic mineralization. The maërl deposits and the skeletal sands are located in the circalittoral zone (82 m to 112 m of water depth), also displaying relict facies. These authors have highlighted that the *Posidonia* meadows represent the main facies of the mobile infra-littoral substratum. In the area surrounding the Pontinian islands the *Posidonia* meadows, ranging at water depths between 30 m and 40 m water depth show a rich epiphytic flora and fauna, living on the seagrass leaves and rhizomes. The unattached coralline algal branches gravel facies indicates the environment representing the highest carbonate production rate. This facies consists of red algae (rhodalgal association) that are the main carbonate-producing biota in the Mediterranean. Brandano et al. [34] have highlighted that the seagrasses represent important carbonate factories, being characterized by important carbonate producing biota, as epiphytes on the leaves and infaunal forms. These authors have determined the skeletal assemblage of both modern (Maldivian and western Mediterranean) and fossil seagrass examples (Eocene; Apula and Oman carbonate platforms and Oligocene; Malta platform). In both Maldivian and western Mediterranean the bioclastic deposits are mainly composed of calcareous algae and foraminifera. As a difference, in the tropical setting they are represented by green algae (*Halimeda*), while in the Mediterranean they consist of red algae [34]. The performed stratigraphic study has shown that the green algae–foralgal assemblage is typical of tropical seagrass meadows. On the contrary, the red algae-foralgal assemblage is typical of tropical to subtropical seagrass meadows.

*Geochemistry*

glauconite.

graphic conditions [12].

offshore of Ischia [13–17].

contrast with the chloralgal and molechfor assemblages, respectively characterized by the lacking of hermatipic corals and by benthic foraminifers, mollusks, echinoids and bryozoans the rhodalgal assemblage is mainly composed of coralline algae [4]. The zonation of benthic assemblages of the Mediterranean sea performed by Peres and Picard [11] has improved the knowledge on lithology and facies interpretation of rhodolith layers (**Figure 1**). In the Mediterranean sea the bioclastic deposits occur at water depths ranging between – 40 m and – 100 m ("Détritique Cotier" of Peres and Picard; **Figure 1**) [11]. In particular, the rhodolith layers are concentrated in the marine sectors exposed to strong current regimes, such as the top of plateaus or banks. The main components of the "Détritique Cotier" are composed of the reworking and deposition of benthic communities on both mobile sea bottoms (biocoenosis of the "Détritique Cotier") and on hard sea bottoms (biocoenosis of the "Détritique Du Large"), more than the assemblages of *Posidonia oceanica* meadows and maërl deposits. As a consequence of the Holocene sea level rise the deep seafloor was covered by relict and drowned sediments ("Détritique Du Large"; **Figure 1**), characterized by low rates of sedimentation and by the occurrence of

The global dominance of coralline algae forming the rhodalgal lithofacies from

the Burdigalian to the Early Tortonian has been demonstrated based on stratigraphic data [12]. In particular, during this time interval the rhodalgal lithofacies has reached peak abundance, replacing the coral reef deposits. The prevalence of coralline algae over coral reefs was suggested as being controlled by the enhancement of the trophic resources and associated with an increase of biological productivity to a global scale [12]. This evidence was shown by geochemical data computed on carbon isotopes. During the Middle Miocene the rhodalgal lithofacies increased its extension, due to the upwelling triggered by the establishment of East Antarctic Ice Sheet led to enhanced. These stratigraphic studies performed to a global scale have confirmed the importance of rhodolith deposits as proxies of past oceano-

This chapter provides new sedimentological and stratigraphic data on the bioclastic deposits and in particular on the rhodolith deposits, occurring in the offshore island of Ischia (Gulf of Naples, Italy); it is based on data coming from sea bottom samples collected during the CARG project aimed at the realization and informatization of the marine geological cartography of the geological sheet No. 464 [13]. The island of Ischia represents the emerged part of a large volcanic field, which extends from the island of Procida to the submerged volcanoes of the western

The occurrence of rodolith deposits in the Gulf of Naples has been suggested by several studies [18–29]. The sedimentological analysis of the sea bottom samples,

*Sketch diagram showing the main biocenosis of mobile sea bottoms (modified after Carannante et al. [4]).*

**276**

**Figure 1.**

In the Gulf of Naples the red algae are widespread especially in the marine areas where the currents removing fine-grained fraction from soft sea bottom leave in place and the abundant coarse grains (lapilli in origin) become an important substratum for the growth of the coralline algae. The red algae are well developed along the western side of the Ischia bank, forming thick deposits near the tributary channel which joins the head of the Magnaghi canyon [29].

The rhodalgal deposits have their optimum bathymetric distribution between −30 m and −44 m of water depth, where a maximum biodiversity has been observed. Furthermore, Babbini et al. [30] have reported the occurrence of a maërl facies in the coastal area of Ischia, in particular in the north-western sector of Ischia, in the area between Punta Imperatore and the town of Forio and between Forio and Punta Caruso (S. Francesco). The studied sampling transects have been carried out at three different water depths (− 50 m, − 65 m, − 80 m). The taxonomic analysis of the macro-phyto-benthic component of the red coral algae has revealed well-pigmented thalli, with a various growth-form (crusty, lumpy, mammellate, arborescent). The free living branches of coralline algae have been attributed to the maërl facies [11], consisting of alive and dead thalli belonging to the species *Lithothamnion corallioides* and *Phymatolithon calcareum*.

Furthermore, the filming carried out with ROV has shown that there are areas of accumulation of calcareous algae in the ripples concavities [30]. In the same area, Gambi et al. [31] have evidenced the occurrence of rhodolith deposits between −50 m and −80 m of water depth, while the maërl facies was found in three samples, in a well-defined belt about one nautical mile long ("the pink mile") [31], located between −50 m and −65 of water depth. The identified zoo-benthic species are typical of the "détritique còtier" of Peres & Picard [11] and of muddy sea bottoms, and the rhodolith deposits of the offshore of Ischia show a very rich and diverse benthic flora and fauna, especially in the maërl facies [31].

#### **2. Materials and methods**

The geological and geophysical data were acquired in the framework of the realization of the geological map n. 464 "Ischia Island" at the 1:10.000 scale [13, 17, 35]. Detailed geological maps, showing the distribution of sea bottom sediments, were built on the basis of the previous geological survey. Furthermore, the new sedimentological analyses of sea bottom samples collected during oceanographic cruises in 2002 and in 2006 have allowed to reconstruct the facies distribution of the sea bottom and to compare the obtained sedimentological and geological results with the previous ones [29, 36]. The stratigraphic framework of the investigated area is based on both high resolution seismic profiles calibrated by cores and on high resolution sequence stratigraphy. Geological and geomorphological data collected at the 1: 10.000 and 1: 5000 scales have been reported on the 1:10.000 geological maps of Campania [35] in order to later produce national geological maps at the 1: 50.000 scale. The previously interpreted Sparker seismic profiles available around Ischia [15, 17, 35], were the subject of a new detailed interpretation focused on the Ischia Bank and Ischia Channel areas, aimed at the identification of bioclastic deposits and at the definition of their stratigraphic relationships with the volcanic and other sedimentary seismic units detected in the offshore of Ischia. The location of the samples analyzed to highlight the rhodolith deposits in the Ischia offshore was superimposed on the Ischia Digital Elevation Model (DEM; **Figure 2**).

During a first work phase, the Multibeam data processing let us to realize bathymetric maps with contour isobaths and shaded-relief maps for the geological

**279**

including their description.

**3.1 Marine and coastal geology**

debris avalanche deposits on land and in the sea [16].

**3. Results**

**Figure 2.**

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New…*

interpretation of the morpho-structural features. During a second phase of work, granulometric analyses were carried out on the sea bottom samples accordingly with the Folk classification. The geological interpretation was based on the identification of the acoustic facies, performed with the integrated interpretation of the multibeam and sidescan sonar data and through the calibration of the acoustic facies in lithological terms, using the results obtained from the granulometric analyses of the sea bottom samples (**Figure 2**; **Table 1**). The sedimentological analyses were performed at the sedimentology laboratory of the CNR-ISMAR in Naples, Italy, using a laser granulometer. The list of analyzed samples is reported in **Table 1**,

The sedimentological data come from samples collected from sea bottoms located between −30 and – 200 m of water depth; they were placed in the framework of the marine geological survey at the 1: 10.000 scale (**Figure 3**). The morphobathymetric characteristics of the different sectors of Ischia, covered by geological survey, are highly variable (eastern, western, southern and northern offshore). The eastern offshore of Ischia, which includes the Ischia Channel, is characterized by sea bottoms with low gradients, locally interrupted by relict volcanic edifices ("I Ruommoli"; "La Catena"; "Vivara ants"). The southern offshore of Ischia is characterized by a narrow continental shelf, cut by submarine canyons and their tributary channels. Its physiography is strongly controlled by the onshore topography, characterized by alternating rocky promontories and inlets. The northern and western offshore of Ischia are characterized by a rough topography, genetically linked to the volcano-tectonic evolution of the island and to the emplacement of the

*DOI: http://dx.doi.org/10.5772/intechopen.95083*

*Onshore-offshore DEM of Ischia reporting the sample location.*

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New… DOI: http://dx.doi.org/10.5772/intechopen.95083*

**Figure 2.** *Onshore-offshore DEM of Ischia reporting the sample location.*

interpretation of the morpho-structural features. During a second phase of work, granulometric analyses were carried out on the sea bottom samples accordingly with the Folk classification. The geological interpretation was based on the identification of the acoustic facies, performed with the integrated interpretation of the multibeam and sidescan sonar data and through the calibration of the acoustic facies in lithological terms, using the results obtained from the granulometric analyses of the sea bottom samples (**Figure 2**; **Table 1**). The sedimentological analyses were performed at the sedimentology laboratory of the CNR-ISMAR in Naples, Italy, using a laser granulometer. The list of analyzed samples is reported in **Table 1**, including their description.

#### **3. Results**

*Geochemistry*

In the Gulf of Naples the red algae are widespread especially in the marine areas

The rhodalgal deposits have their optimum bathymetric distribution between

observed. Furthermore, Babbini et al. [30] have reported the occurrence of a maërl facies in the coastal area of Ischia, in particular in the north-western sector of Ischia, in the area between Punta Imperatore and the town of Forio and between Forio and Punta Caruso (S. Francesco). The studied sampling transects have been carried out at three different water depths (− 50 m, − 65 m, − 80 m). The taxonomic analysis of the macro-phyto-benthic component of the red coral algae has revealed well-pigmented thalli, with a various growth-form (crusty, lumpy, mammellate, arborescent). The free living branches of coralline algae have been attributed to the maërl facies [11], consisting of alive and dead thalli belonging to

Furthermore, the filming carried out with ROV has shown that there are areas of accumulation of calcareous algae in the ripples concavities [30]. In the same area, Gambi et al. [31] have evidenced the occurrence of rhodolith deposits between −50 m and −80 m of water depth, while the maërl facies was found in three samples, in a well-defined belt about one nautical mile long ("the pink mile") [31], located between −50 m and −65 of water depth. The identified zoo-benthic species are typical of the "détritique còtier" of Peres & Picard [11] and of muddy sea bottoms, and the rhodolith deposits of the offshore of Ischia show a very rich and

The geological and geophysical data were acquired in the framework of the realization of the geological map n. 464 "Ischia Island" at the 1:10.000 scale [13, 17, 35]. Detailed geological maps, showing the distribution of sea bottom sediments, were built on the basis of the previous geological survey. Furthermore,

the new sedimentological analyses of sea bottom samples collected during oceanographic cruises in 2002 and in 2006 have allowed to reconstruct the facies distribution of the sea bottom and to compare the obtained sedimentological and geological results with the previous ones [29, 36]. The stratigraphic framework of the investigated area is based on both high resolution seismic profiles calibrated by cores and on high resolution sequence stratigraphy. Geological and geomorphological data collected at the 1: 10.000 and 1: 5000 scales have been reported on the 1:10.000 geological maps of Campania [35] in order to later produce national geological maps at the 1: 50.000 scale. The previously interpreted Sparker seismic profiles available around Ischia [15, 17, 35], were the subject of a new detailed interpretation focused on the Ischia Bank and Ischia Channel areas, aimed at the identification of bioclastic deposits and at the definition of their stratigraphic relationships with the volcanic and other sedimentary seismic units detected in the offshore of Ischia. The location of the samples analyzed to highlight the rhodolith deposits in the Ischia offshore was superimposed on the Ischia Digital Elevation

During a first work phase, the Multibeam data processing let us to realize bathymetric maps with contour isobaths and shaded-relief maps for the geological

where the currents removing fine-grained fraction from soft sea bottom leave in place and the abundant coarse grains (lapilli in origin) become an important substratum for the growth of the coralline algae. The red algae are well developed along the western side of the Ischia bank, forming thick deposits near the tributary

−30 m and −44 m of water depth, where a maximum biodiversity has been

the species *Lithothamnion corallioides* and *Phymatolithon calcareum*.

diverse benthic flora and fauna, especially in the maërl facies [31].

**2. Materials and methods**

channel which joins the head of the Magnaghi canyon [29].

**278**

Model (DEM; **Figure 2**).

#### **3.1 Marine and coastal geology**

The sedimentological data come from samples collected from sea bottoms located between −30 and – 200 m of water depth; they were placed in the framework of the marine geological survey at the 1: 10.000 scale (**Figure 3**). The morphobathymetric characteristics of the different sectors of Ischia, covered by geological survey, are highly variable (eastern, western, southern and northern offshore). The eastern offshore of Ischia, which includes the Ischia Channel, is characterized by sea bottoms with low gradients, locally interrupted by relict volcanic edifices ("I Ruommoli"; "La Catena"; "Vivara ants"). The southern offshore of Ischia is characterized by a narrow continental shelf, cut by submarine canyons and their tributary channels. Its physiography is strongly controlled by the onshore topography, characterized by alternating rocky promontories and inlets. The northern and western offshore of Ischia are characterized by a rough topography, genetically linked to the volcano-tectonic evolution of the island and to the emplacement of the debris avalanche deposits on land and in the sea [16].


**281**

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New…*

**depth**

B1798 Sandy silts Ischia Bank −74 m Clay with a dark green sandy fraction.

**Description**

−30 m Coarse-grained sand with a silty matrix.

veil, slightly oxidized.

−24 m Coarse-grained sand with a silty matrix.

−18 m Bioclastic medium-coarse-grained sand

−99 m Gravelly mud ("Détritique Cotier"). The

and tuff fragments.

−38 m Sands with a silty-muddy matrix. The

of marine organisms.

−36 m Coarse-to-middle grained litho-bioclastic sand with a scarce muddy matrix.

−30 m Bioclastic medium-grained sand with a

−73.2 m Bioclastic coarse-grained sand on a silty

and branched bryozoans.

pebbles.

Ischia Channel −63 m Compact mud with medium-fine-grained

Ischia −70 m Gravelly mud ("Détritique Cotier").

−34 m Sands with a silty matrix, overlying

Occurrence of small bivalves and live worms. Small lithic fragments.

Occurrence of bivalves, rhizomes of *Posidonia oceanica*, gastropods and echinoids. Volcanic lithics, small pumice and remains of coal. Yellow superficial

coarse-grained bioclastic sands. Fragments of bivalves, small lamellibranch, red algae, small gastropods, rhizomes of *Posidonia oceanica*, branched bryozoans.

Occurrence of shell fragments, small regular echinoids and scarce lithics.

in a scarce muddy matrix. Occurrence of *Posidonia oceanica* and lamellibranchs.

sandy fraction, consisting of bioclasts, small pumiceous clasts and lithics. Very residual of *Posidonia oceanica* in the first subfloor with masses of rhizomes.

Occurrence of lamellibranchs, red algae, single corals and pumiceous clasts.

gravelly fraction is composed of pumice

sandy fraction consists of lithoclasts and bioclasts. Living organisms (small crabs and lamellibranchs). Occurrence of tuff

towards the bottom mud. Occurrence of a bioclastic component composed of shells

silty matrix. Occurrence of bivalves and fragments of lamellibranch shells.

matrix. Color 5y4/2. Occurrence of small bivalves, fragments of calcareous algae

*DOI: http://dx.doi.org/10.5772/intechopen.95083*

B1796 Silty

B1800 Sands and

B1802 Sands and

B1804 Sands and

B1806 Silty

B1808 Silty

B1810 Silty

B1818 Sands and

gravelly sands

B1084 Sands Northern

B1088 Silts Northern

gravelly sands

gravelly sands

gravelly sands

sands

sands

sands

B1815 Sands Forio-

sands

**Sample Lithology Location Water** 

Ischia Bank

Ischia Channel

Ischia Bank

Vivara (Procida)

Ischia harbor-Casamicciola

Casamicciola

Western Ischia offshore (Citara)

Ischia (Punta Cornacchia promontory)

Ischia

B1816bis Sandy silts Forio Bank −159 m Superficial veil saturated with water,

B1820 Sandy silts Maronti −96 m Mud with rare sedentary polychaetes.


*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New… DOI: http://dx.doi.org/10.5772/intechopen.95083*

*Geochemistry*

B1082 Silty

B1085 Sandy

sands

muds

B1090 Sandy silts North-western

B1094 Sands South-western

B1096 Sands South-western

B1098 Sandy silts Western

B1101 Silts Northern

sands

sands

B1107 Sandy silts South-western

B1103 Silty

B1105 Silty

B1111 Silty

B1794 Sands and

sands

gravelly sands

**Sample Lithology Location Water** 

Northern Ischia; M.te Vico promontory

Northern Ischia; Punta La Scrofa promontory

Ischia – Punta Caruso promontory

Ischia – Punta Imperatore promontory

Ischia – Citara beach

Ischia – Punta del Soccorso promontory

South-western Ischia – Punta dello Schiavo promontory

South-western Ischia – Capo Negro promontory

Ischia – Punta del Chiarito promontory

Northern Ischia

Ischia – Monte Vico promontory **depth**

**Description**

Small pumices.

−65 m Heterometric bioclastic sand

1 cm.

−57 m Middle-grained sand in a silty matrix.

−149 m Silty mud. Color 5y4/2. Occurrence of

−27 m Coarse-grained volcanic sand. Scattered pebbles encrusted with worms. Fragments of calcareous algae. Small complete bivalves. Agglutinating worm

−38 m Medium-grained volcanic sand.

fragments.

tube. Pumice.

−100 m Fine-grained sand. *Posidonia oceanica*

−95.6 m Sandy silt with fragments of bioclasts.

−88 m Bioclastic sands in a fine-grained

−74 m Concretions of red algae, having

echinoids.

Ischia Bank −27 m Description lacking

−168 m Slightly sandy silt. Color 5y4/2. Reworked *Posidonia oceanica*.

−42 m Bioclastic medium-grained sand with

a silty matrix. Occurrence of bivalves, gastropods and bryozoan fragments.

scales. Small bivalves, gastropods. Occurrence of superficial veil, thick 1 cm, composed of oxidized, fine-grained silt.

Color 5y 4/3. Lamellibranch valves, corals, bryozoans fragments. Occurrence of superficial veil composed of silty clay.

sandy matrix. Red algae, annelids, lamellibranch valves. *Posidonia oceanica* rhizomes. The superficial veil is covered by a net made of *Posidonia oceanica* flakes.

dimensions in the order of 7–10 cm, overlying fine-grained sands. Tubes of worms, bryozoans, corals. Occurrence of a superficial veil, composed of finegrained sand, *Posidonia oceanica* leaves, gastropods (*Turritella*), lamellibranchs, rounded pumice clasts and fragments of

Color 5y4/2.*Posidonia oceanic* leaves, lamellibranch fragments and valves.

in a silty matrix. Fragments of gastropods,bivalves,calcareous algae. Occurrence of superficial silt veil.

superficial silt veil, oxidized, thick about

Fragments of echinoids, whole irregular echinoids, lamellibranch shells. Lithic

**280**


**283**

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New…*

**depth**

**Description**

Ischia Channel −63 m Compact mud with medium-fine-grained

Ischia −67 m Gravelly mud ("Détritique Cotier").

−18 m Bioclastic medium-coarse-grained sand

−99 m Gravelly mud ("Détritique Cotier"). The

and tuff fragments.

−38 m Sands with a silty-muddy matrix. The

pebbles.

−40 m Volcanic rocky substratum with

−53 m Coarse-grained bioclastic sands.

by red algae.

dimensions.

Ischia Bank −30 m Medium-coarse-grained sand with shell

B1801 Sands Ischia Channel −39 m Bioclastic sands, medium-coarse-grained.

−32 m Rocky substratum. Occurrence of

grained sandy matrix.

bryozoans and red algae.

−37 m Bioclastic sand in a silty matrix.

bryozoans.

Ischia Channel −16 m *Posidonia oceanica* on a coarse-grained

Ischia harbor −24 m Living *Posidonia oceanica* on a dark sandy

in a scarce muddy matrix. Occurrence of *Posidonia oceanica* and lamellibranchs.

sandy fraction, consisting of bioclasts, small pumiceous clasts and lithics. Very residual of *Posidonia oceanica* in the first subfloor with masses of rhizomes.

Occurrence of lamellibranchs, red algae, single corals and pumiceous clasts.

gravelly fraction is composed of pumice

sandy fraction consists of lithoclasts and bioclasts. Living organisms (small crabs and lamellibranchs). Occurrence of tuff

superficial algal incrustations colonized

Occurrence of bryozoans, bivalves and calcareous algae fragments. Occurrence of rocky fragments of centimeter

volcanic blocks, immersed in a matrix composed of medium-coarse-grained bioclastic sands. Occurrence of branched bryozoans, lamellibranch valves and calcareous algae fragments.

fragments overlain by *Posidonia oceanica* meadow. Occurrence of a poor fine-

Occurrence of glass fragments, branched

Occurrence of red algae and branched

sandy bottom, with red algae. Occurrence of shell fragments in the sandy part.

ground with a muddy matrix. Occurrence of lamellibranch valves, fragments of lamellibranchs, live rhodoliths, bryozoans and echinoids.

*DOI: http://dx.doi.org/10.5772/intechopen.95083*

B1804 Sands and

B1806 Silty

B1808 Silty

B1810 Silty

B1097 Silty

B1110 Silty

B1795 Sands and

B1797 Sands and

B1803 Sands and

B1805 Sands and

gravelly sands

sands

sands

sands

B1815 Sands Forio-

sands

sands

B1112 Sands Northern

gravelly sands

gravelly sands

gravelly sands

gravelly sands

**Sample Lithology Location Water** 

Vivara (Procida)

Ischia harbor-Casamicciola

Casamicciola

South-western Ischia – Citara beach

North-western Ischia – Monte Vico promontory

Ischia - Casamicciola

Parasitic vent of the Ischia Bank

**Sample Lithology Location Water depth Description** B1804 Sands and gravelly sands Vivara (Procida) −18 m Bioclastic medium-coarse-grained sand in a scarce muddy matrix. Occurrence of *Posidonia oceanica* and lamellibranchs. B1806 Silty sands Ischia Channel −63 m Compact mud with medium-fine-grained sandy fraction, consisting of bioclasts, small pumiceous clasts and lithics. Very residual of *Posidonia oceanica* in the first subfloor with masses of rhizomes. B1808 Silty sands Ischia −67 m Gravelly mud ("Détritique Cotier"). Occurrence of lamellibranchs, red algae, single corals and pumiceous clasts. B1810 Silty sands Ischia harbor-Casamicciola −99 m Gravelly mud ("Détritique Cotier"). The gravelly fraction is composed of pumice and tuff fragments. B1815 Sands Forio-Casamicciola −38 m Sands with a silty-muddy matrix. The sandy fraction consists of lithoclasts and bioclasts. Living organisms (small crabs and lamellibranchs). Occurrence of tuff pebbles. B1097 Silty sands South-western Ischia – Citara beach −40 m Volcanic rocky substratum with superficial algal incrustations colonized by red algae. B1110 Silty sands North-western Ischia – Monte Vico promontory −53 m Coarse-grained bioclastic sands. Occurrence of bryozoans, bivalves and calcareous algae fragments. Occurrence of rocky fragments of centimeter dimensions. B1112 Sands Northern Ischia - Casamicciola −32 m Rocky substratum. Occurrence of volcanic blocks, immersed in a matrix composed of medium-coarse-grained bioclastic sands. Occurrence of branched bryozoans, lamellibranch valves and calcareous algae fragments. B1795 Sands and gravelly sands Ischia Bank −30 m Medium-coarse-grained sand with shell fragments overlain by *Posidonia oceanica* meadow. Occurrence of a poor finegrained sandy matrix. B1797 Sands and gravelly sands Parasitic vent of the Ischia Bank −37 m Bioclastic sand in a silty matrix. Occurrence of glass fragments, branched bryozoans and red algae. B1801 Sands Ischia Channel −39 m Bioclastic sands, medium-coarse-grained. Occurrence of red algae and branched bryozoans. B1803 Sands and gravelly sands Ischia Channel −16 m *Posidonia oceanica* on a coarse-grained sandy bottom, with red algae. Occurrence of shell fragments in the sandy part. B1805 Sands and gravelly sands Ischia harbor −24 m Living *Posidonia oceanica* on a dark sandy ground with a muddy matrix. Occurrence of lamellibranch valves, fragments of lamellibranchs, live rhodoliths, bryozoans and echinoids.

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New… DOI: http://dx.doi.org/10.5772/intechopen.95083*

*Geochemistry*

**Sample Lithology Location Water** 

Ischia – Punta Caruso promontory

South-western Ischia – Punta Imperatore Promontory

South-western Ischia – Citara beach

Ischia –Citara beach

Ischia – Monte Vico promontory

Ischia – Chianare di Spadera

South-western Ischia – Punta del Chiarito promontory

Ischia – Punta del Chiarito promontory

Ischia Bank Not

recorded in the navigation data

B1798 Sandy silts Ischia Bank −74 m Clay with a dark green sandy fraction.

B1092 Silts Northern

sands

sands

B1100 Sandy silts South-western

B1102 Silts Northern

B1104 Sandy silts South-western

B1107 Sandy silts South-western

B1106 Sands and

B1796 Silty

B1800 Sands and

B1802 Sands and

gravelly sands

gravelly sands

Ischia Bank

gravelly sands

sands

B1095 Silty

B1097 Silty

**depth**

**Description**

−133 m Superficial veil composed of oxidized silt

−71 m Centimetric pebbles in a sandy matrix composed of fine-grained sand. Occurrence of lamellibranch and

pectinidae valves.

−40 m Volcanic rocky substratum with

−100 m Fine-grained sand. Occurrence of

thick, oxidized, silty.

−109 m Fine-grained sand with a silty matrix.

−40 m Medium-coarse-grained volcanic sand.

lamellibranch fragments.

−168 m Slightly sandy silt. Color 5y4/2. Reworked *Posidonia oceanica*.

−136 m Towards the base clay. Color 5y4/1.

Color 5y 4/3.

by red algae.

of about 1 cm in thickness. Proceeding downwards plastic clay. Color 5y4/2.

superficial algal incrustations colonized

fragments of calcareous algae and reworked *Posidonia oceanica* flakes. Occurrence of surface veil, about ½ cm

Superficial veil composed of silty mud.

Occurrence of *Posidonia oceanica* flakes.

Occurrence of red algae, gastropods and

Coarse-grained sand with a silty matrix. Occurrence of small bivalves and live worms. Small lithic fragments

Occurrence of bivalves, rhizomes of *Posidonia oceanica*, gastropods and echinoids. Volcanic lithics, small pumice and remains of coal. Yellow superficial

coarse-grained bioclastic sands. Fragments of bivalves, small lamellibranch, red algae, small gastropods, rhizomes of *Posidonia oceanica*, branched bryozoans.

Occurrence of shell fragments, small regular echinoids and scarce lithics.

veil, slightly oxidized.

−24 m Coarse-grained sand with a silty matrix.

Ischia Channel −34 m Sands with a silty matrix, overlying

**282**


#### **Table 1.**

*List of sea bottom samples and their lithology based on grain-size analysis. Location, water depths and description of sea bottom samples are indicated.*

Marine geological survey on a scale of 1: 10.000 has allowed to map the Late Quaternary depositional sequence, which includes the TST-HST deposits (slope deposits) and the HST deposits (submerged beach deposits; inner and outer shelf deposits, either bioclastic or epiclastic in origin). This sequence covers significant accumulations of debris avalanche/debris flow deposits, which are located both in the northern offshore of Ischia between Lacco Ameno and Casamicciola and in the western offshore of Ischia, between the promontories of Punta del Soccorso and Punta Imperatore. These debris are composed of heterometric blocks and accumulations of blocks and lavas immersed in a coarse-to-fine grained matrix. Furthermore, significant outcrops of undifferentiated volcanic substratum have been recognized, whose precise attribution in the volcanic deposits of Ischia is problematic, due to the lacking of direct sampling.

The Section 40 at a 1:10.000 scale, located in the northern offshore of Ischia (promontory of Punta La Scrofa; **Figure 3**) has shown textures that include sands, pelitic sands and sandy pelites. The Late Quaternary marine deposits unconformably overlie the deposits of the northern debris avalanche and the undifferentiated volcanic substratum. Here the rhodolith deposits are represented by bioclastic detrital sands, the elements of which are composed of fragments of calcareous algae, bryozoans, mollusks and echinoids. These bioclastic sands, from a few decimeters to a few centimeters thick, cover pelitic drapes. The inner shelf deposits

**285**

pelites.

fine-grained sands.

**Figure 3.**

bioclasts and rhizomes of *Posidonia oceanica*.

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New…*

are composed of medium-coarse-grained sands and fine-grained pelitic sands. The outer shelf deposits are characterized by pelites with variable fractions of medium-

*Sketch frame of some cartographic sections of the Ischia marine geological survey (scale 1:10.000).*

The Section 60 at the 1: 10.000 scale is located in the western offshore of Ischia, outside the promontory of Punta del Soccorso (**Figure 3**), and sands, pelitic sands, sandy and pelitic muds have been mapped. The Late Quaternary marine deposits unconformably overlie the deposits of the western debris avalanche and the undifferentiated volcanic substratum. The Forio Bank has been mapped as a tuff cone, the top of which is found at a water depth of −38 m. At the top of the tuff cone of the Forio Bank rhodolith deposits have been found, represented by bioclastic sands in a scarce pelitic matrix. Furthermore, the outer shelf deposits are composed of pelites with variable fractions of medium-fine-grained sands, with volcaniclasts,

The Section 70 at the 1:10.000 scale is located in the western offshore of Ischia between the promontories of Punta del Soccorso and Punta Imperatore (**Figure 3**). A large area of the sea bottom between the two promontories is characterized by the outcropping deposits of the western debris avalanche of Ischia. The submerged beach deposits are composed of well-sorted sands and pebbles, made up of volcanic lithic elements, from rounded to sub-rounded, with a scarce pelitic matrix and subordinately by bioclasts. The rhodolith deposits crop out on the Forio Bank and are composed of coarse-grained bioclastic sands and bioclastic gravels, similar to those ones found on the Ischia Bank. The inner shelf deposits are characterized by medium-coarse-grained sands and fine-grained pelitic sands. The outer shelf deposits are composed of pelites with variable fractions of medium-finegrained sands, with volcaniclasts and bioclasts and subordinately, with rhizomes of *Posidonia oceanica*. Finally, the slope deposits are formed by pelites and sandy

In the Ischia offshore the inner shelf deposits, Holocene in age, are composed of four lithologic associations. The first lithologic association is characterized by

*DOI: http://dx.doi.org/10.5772/intechopen.95083*

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New… DOI: http://dx.doi.org/10.5772/intechopen.95083*

**Figure 3.**

*Geochemistry*

B1809 Muddy

B1813 Sands and

sands

gravelly sands

B1816 Sandy silts Forio Bank

B1817 Sandy silts Western

*description of sea bottom samples are indicated.*

**Sample Lithology Location Water** 

Ischia harbor

Base of the volcanic edifice

Ischia offshore (Citara)

**depth**

B1807 Sandy silts Ischia Channel −53 m Silt with fine-grained sands. Occurrence

**Description**

of reworked *Posidonia oceanica* and lamellibranchs. Oxidized surface veil.

veil. Below bioclastic sands in an abundant muddy matrix with living worms and fragments of mollusks.

veil. Below bioclastic sands in abundant muddy matrix with living worms and

−51 m Slightly oxidized superficial silty-sandy

fragments of mollusks.

−179 m Compact oxidized surface mud with rare sub-rounded pumice.

> the sediment is full of valves of large lamellibranchs, colonized by single corals. Rare tufaceous pebbles, many

a poor muddy matrix. Presence of glass, slag, tufaceous granules; worms and fragments of gastropods and

−191 m Oxidized mud with gastropods.

polychaetes.

lamellibranchs.

Casamicciola −55 m Slightly oxidized superficial silty-sandy

**284**

**Table 1.**

Marine geological survey on a scale of 1: 10.000 has allowed to map the Late Quaternary depositional sequence, which includes the TST-HST deposits (slope deposits) and the HST deposits (submerged beach deposits; inner and outer shelf deposits, either bioclastic or epiclastic in origin). This sequence covers significant accumulations of debris avalanche/debris flow deposits, which are located both in the northern offshore of Ischia between Lacco Ameno and Casamicciola and in the western offshore of Ischia, between the promontories of Punta del Soccorso and Punta Imperatore. These debris are composed of heterometric blocks and accumulations of blocks and lavas immersed in a coarse-to-fine grained matrix. Furthermore, significant outcrops of undifferentiated volcanic substratum have been recognized, whose precise attribution in the volcanic deposits of Ischia is

*List of sea bottom samples and their lithology based on grain-size analysis. Location, water depths and* 

B1819 Sandy silts Cava Grado −88 m Mud with fine-grained sand. Downwards

B1821 Sands Cava Grado −41 m Medium-grained lithoclastic sand with

The Section 40 at a 1:10.000 scale, located in the northern offshore of Ischia (promontory of Punta La Scrofa; **Figure 3**) has shown textures that include sands, pelitic sands and sandy pelites. The Late Quaternary marine deposits unconformably overlie the deposits of the northern debris avalanche and the undifferentiated volcanic substratum. Here the rhodolith deposits are represented by bioclastic detrital sands, the elements of which are composed of fragments of calcareous algae, bryozoans, mollusks and echinoids. These bioclastic sands, from a few decimeters to a few centimeters thick, cover pelitic drapes. The inner shelf deposits

problematic, due to the lacking of direct sampling.

*Sketch frame of some cartographic sections of the Ischia marine geological survey (scale 1:10.000).*

are composed of medium-coarse-grained sands and fine-grained pelitic sands. The outer shelf deposits are characterized by pelites with variable fractions of mediumfine-grained sands.

The Section 60 at the 1: 10.000 scale is located in the western offshore of Ischia, outside the promontory of Punta del Soccorso (**Figure 3**), and sands, pelitic sands, sandy and pelitic muds have been mapped. The Late Quaternary marine deposits unconformably overlie the deposits of the western debris avalanche and the undifferentiated volcanic substratum. The Forio Bank has been mapped as a tuff cone, the top of which is found at a water depth of −38 m. At the top of the tuff cone of the Forio Bank rhodolith deposits have been found, represented by bioclastic sands in a scarce pelitic matrix. Furthermore, the outer shelf deposits are composed of pelites with variable fractions of medium-fine-grained sands, with volcaniclasts, bioclasts and rhizomes of *Posidonia oceanica*.

The Section 70 at the 1:10.000 scale is located in the western offshore of Ischia between the promontories of Punta del Soccorso and Punta Imperatore (**Figure 3**). A large area of the sea bottom between the two promontories is characterized by the outcropping deposits of the western debris avalanche of Ischia. The submerged beach deposits are composed of well-sorted sands and pebbles, made up of volcanic lithic elements, from rounded to sub-rounded, with a scarce pelitic matrix and subordinately by bioclasts. The rhodolith deposits crop out on the Forio Bank and are composed of coarse-grained bioclastic sands and bioclastic gravels, similar to those ones found on the Ischia Bank. The inner shelf deposits are characterized by medium-coarse-grained sands and fine-grained pelitic sands. The outer shelf deposits are composed of pelites with variable fractions of medium-finegrained sands, with volcaniclasts and bioclasts and subordinately, with rhizomes of *Posidonia oceanica*. Finally, the slope deposits are formed by pelites and sandy pelites.

In the Ischia offshore the inner shelf deposits, Holocene in age, are composed of four lithologic associations. The first lithologic association is characterized by

heterometric blocks and pebbles, which come from the recent and current rearrangement of the adjacent deposits of debris avalanche/debris flow and crop out within depressed or protected areas.

The second lithologic association consists of medium-coarse-grained lithoclastic sands, sometimes pebbly, with scattered heterometric clasts and blocks, of pyroclastic composition (pumice, lithic and scoria) and lava, from rounded to subrounded, often immersed in a scarce sandy matrix, medium-fine-grained. Locally, a bioclastic component is present.

The third lithologic association is characterized by bio-lithoclastic sands, from medium-fine-grained to fine-grained, immersed in a scarce pelitic matrix, which include heterometric pebbles, from centimetric to pluri-centimetric, of lava and/ or pyroclastic composition. The main components are represented by volcaniclasts (pumice, lithic and scoria) and bioclasts, mainly composed of fragments of mollusks. This association extensively crops out in large sectors of the proximal inner shelf and indicates a low-energy sedimentation on flat sea bottoms.

The fourth lithologic association, ranging in age between the Late Pleistocene and the Early Holocene, includes the palimpsest deposits, composed of gravels and sandy gravels with a prevalent pyroclastic composition, from rounded to subrounded, immersed in a scarce sandy matrix, from medium-fine-grained to finegrained. In the offshore of Ischia this lithologic association is found in scattered outcrops in southern Ischia (La Guardiola), at water depths ranging between −12 m and −15 m and in western Ischia (Forio), at water depths of −30 m, where these deposits are associated with ancient shorelines.

#### **3.2 Sedimentological data**

Sedimentological analyses were performed with the aim of showing the main compositional and textural characters of sediments sampled at the sea bottom in Ischia. The sediment fractions recognized at the sea bottom based on particle size analyses include gravel sands, sands, silty sands, muddy sands, sandy silts and silts. Multibeam, Sidescan sonar and seismic data, together with samples, were acquired during the realization of sheet n. 464 "Ischia Island" of the new geological map of Italy [13].

Some textural classes have been identified on the basis of the integrated interpretation of geophysical and geological data. The recognized textures have provided additional information on the lithofacies associations, in order to identify the differences in the depositional elements that have been mapped. Moreover, ternary plots have been constructed for a better evaluation of different grain size (**Figure 4**), considering as variables respectively clay-sand-silt and gravel-sandsilt. The samples have been plotted in ternary diagrams subdividing them with respect to the oceanographic cruises GMS02\_01 (diagrams in the upper part of **Figure 4**) and GMS06\_03 (diagrams in the lower part of **Figure 4**).

In particular, the ternary diagram located in the upper left corner of **Figure 4** has considered as variables: clay, sand and silt. This plot has shown that the main lithologies are the clayey silts and the sandy silts (**Figure 4**). The ternary diagram located in the upper right corner of **Figure 4** has considered as variables: gravel, sand and silt. This plot has shown that the main lithologies are represented by silty sands and gravelly sands.

Moreover, the ternary diagram located in the lower left corner of **Figure 4** has considered as variables: clay, sand and silt. This plot has highlighted that the main lithologies are represented by sands and silty sands (**Figure 4**). The ternary diagram located in the lower right corner of **Figure 4** has considered as variables: gravel,

**287**

deposits.

**Figure 4.**

**3.3 Rhodolith deposits**

*Ternary plots of the processed sea-bottom samples.*

bryozoans (**Figure 5**).

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New…*

sand and silt. This plot has highlighted that the main lithologies are represented by

On the Ischia Bank, a large volcanic edifice located in the south-eastern offshore

The rhodolith deposits were also found on the parasitic vent, genetically connected to the main volcanic edifice of the Ischia Bank (sample B1797; **Figure 5**). Here bioclastic sands with glassy fragments, bryozoans and coralline algae have been found in a muddy lithoclastic matrix with a volcanic component. Rhodolith deposits were also found in sample B1799, located on the same adventitious cone, in which these deposits are associated with mollusk shells, small gastropods and scarce

of Ischia, an extensive meadow in *Posidonia oceanica* covers dark brown heterometric bioclastic sands (sample B1794; **Figure 5**) interpreted as rhodolith deposits due to the presence of living coralline algae. The sands cover a pebbly deposit consisting mainly of shells of mollusks, with fragments of echinoids, widespread on the *Posidonia oceanica* meadow. A low percentage of mud fraction occurs in these

sands and gravelly sands and subordinately, by sandy silts (**Figure 4**).

*DOI: http://dx.doi.org/10.5772/intechopen.95083*

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New… DOI: http://dx.doi.org/10.5772/intechopen.95083*

**Figure 4.** *Ternary plots of the processed sea-bottom samples.*

sand and silt. This plot has highlighted that the main lithologies are represented by sands and gravelly sands and subordinately, by sandy silts (**Figure 4**).

#### **3.3 Rhodolith deposits**

On the Ischia Bank, a large volcanic edifice located in the south-eastern offshore of Ischia, an extensive meadow in *Posidonia oceanica* covers dark brown heterometric bioclastic sands (sample B1794; **Figure 5**) interpreted as rhodolith deposits due to the presence of living coralline algae. The sands cover a pebbly deposit consisting mainly of shells of mollusks, with fragments of echinoids, widespread on the *Posidonia oceanica* meadow. A low percentage of mud fraction occurs in these deposits.

The rhodolith deposits were also found on the parasitic vent, genetically connected to the main volcanic edifice of the Ischia Bank (sample B1797; **Figure 5**). Here bioclastic sands with glassy fragments, bryozoans and coralline algae have been found in a muddy lithoclastic matrix with a volcanic component. Rhodolith deposits were also found in sample B1799, located on the same adventitious cone, in which these deposits are associated with mollusk shells, small gastropods and scarce bryozoans (**Figure 5**).

*Geochemistry*

within depressed or protected areas.

bioclastic component is present.

heterometric blocks and pebbles, which come from the recent and current rearrangement of the adjacent deposits of debris avalanche/debris flow and crop out

The second lithologic association consists of medium-coarse-grained lithoclastic sands, sometimes pebbly, with scattered heterometric clasts and blocks, of pyroclastic composition (pumice, lithic and scoria) and lava, from rounded to subrounded, often immersed in a scarce sandy matrix, medium-fine-grained. Locally, a

The third lithologic association is characterized by bio-lithoclastic sands, from medium-fine-grained to fine-grained, immersed in a scarce pelitic matrix, which include heterometric pebbles, from centimetric to pluri-centimetric, of lava and/ or pyroclastic composition. The main components are represented by volcaniclasts (pumice, lithic and scoria) and bioclasts, mainly composed of fragments of mollusks. This association extensively crops out in large sectors of the proximal inner

The fourth lithologic association, ranging in age between the Late Pleistocene and the Early Holocene, includes the palimpsest deposits, composed of gravels and sandy gravels with a prevalent pyroclastic composition, from rounded to subrounded, immersed in a scarce sandy matrix, from medium-fine-grained to finegrained. In the offshore of Ischia this lithologic association is found in scattered outcrops in southern Ischia (La Guardiola), at water depths ranging between −12 m and −15 m and in western Ischia (Forio), at water depths of −30 m, where these

Sedimentological analyses were performed with the aim of showing the main compositional and textural characters of sediments sampled at the sea bottom in Ischia. The sediment fractions recognized at the sea bottom based on particle size analyses include gravel sands, sands, silty sands, muddy sands, sandy silts and silts. Multibeam, Sidescan sonar and seismic data, together with samples, were acquired during the realization of sheet n. 464 "Ischia Island" of the new geological map of

Some textural classes have been identified on the basis of the integrated interpretation of geophysical and geological data. The recognized textures have provided additional information on the lithofacies associations, in order to identify the differences in the depositional elements that have been mapped. Moreover, ternary plots have been constructed for a better evaluation of different grain size (**Figure 4**), considering as variables respectively clay-sand-silt and gravel-sandsilt. The samples have been plotted in ternary diagrams subdividing them with respect to the oceanographic cruises GMS02\_01 (diagrams in the upper part of

In particular, the ternary diagram located in the upper left corner of **Figure 4** has considered as variables: clay, sand and silt. This plot has shown that the main lithologies are the clayey silts and the sandy silts (**Figure 4**). The ternary diagram located in the upper right corner of **Figure 4** has considered as variables: gravel, sand and silt. This plot has shown that the main lithologies are represented by silty

Moreover, the ternary diagram located in the lower left corner of **Figure 4** has considered as variables: clay, sand and silt. This plot has highlighted that the main lithologies are represented by sands and silty sands (**Figure 4**). The ternary diagram located in the lower right corner of **Figure 4** has considered as variables: gravel,

**Figure 4**) and GMS06\_03 (diagrams in the lower part of **Figure 4**).

shelf and indicates a low-energy sedimentation on flat sea bottoms.

deposits are associated with ancient shorelines.

**3.2 Sedimentological data**

sands and gravelly sands.

Italy [13].

**286**

**289**

**Figure 6.**

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New…*

Rhodolith deposits were also found in the offshore of Casamicciola (Ischia north; sample B1813; **Figure 5**). Here these deposits grade laterally to sandy and muddy sediments and to the debris avalanche deposits present in Casamicciola. In the western offshore of Ischia, rhodolith deposits are present at the top of the volcanic edifice of the Forio Bank, where they are characterized by coarse-grained sands and bioclastic pebbles in a scarce pelitic matrix. These deposits are completely analogous to those found on the Ischia Bank, given that the fundamental genetic

The sampling data on rhodolith deposits have allowed to review previous interpretations of seismic lines in the offshore of Ischia [15]. At Ischia, the occurrence of isolated volcanic bodies, which include intrusions, domes and volcanic chimneys, was particularly complex to apply seismic and sequence stratigraphy in the interpretation of seismic data [37–39]. Volcanic bodies, which include lava flows, volcanic domes and volcanic intrusions, cannot be investigated by reflection

*Detail of the seismic profile L57 (Ischia Bank), showing the seismic unit cropping out at the sea bottom,* 

*including the rhodolith deposits occurring at the top of the volcanic edifice.*

*DOI: http://dx.doi.org/10.5772/intechopen.95083*

analogy between the two volcanic edifices.

**3.4 Seismic stratigraphy**

**Figure 5.** *Sea bottom samples showing the occurrence of bioclastic deposits in the Ischia offshore.*

Rhodolith deposits were also found in the Ischia Channel, a morphological threshold located between the islands of Ischia and Procida, where they were sampled by sample B1800. Here the rhodolith deposits are covered by an extensive meadow in *Posidonia oceanica*. Coralline algae are associated with fragments of mollusks, small gastropods, rhizomes of *Posidonia oceanica* and branched bryozoans, as well as with small slags and volcanic glass (**Figure 5**).

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New… DOI: http://dx.doi.org/10.5772/intechopen.95083*

Rhodolith deposits were also found in the offshore of Casamicciola (Ischia north; sample B1813; **Figure 5**). Here these deposits grade laterally to sandy and muddy sediments and to the debris avalanche deposits present in Casamicciola.

In the western offshore of Ischia, rhodolith deposits are present at the top of the volcanic edifice of the Forio Bank, where they are characterized by coarse-grained sands and bioclastic pebbles in a scarce pelitic matrix. These deposits are completely analogous to those found on the Ischia Bank, given that the fundamental genetic analogy between the two volcanic edifices.

#### **3.4 Seismic stratigraphy**

*Geochemistry*

**288**

**Figure 5.**

Rhodolith deposits were also found in the Ischia Channel, a morphological threshold located between the islands of Ischia and Procida, where they were sampled by sample B1800. Here the rhodolith deposits are covered by an extensive meadow in *Posidonia oceanica*. Coralline algae are associated with fragments of mollusks, small gastropods, rhizomes of *Posidonia oceanica* and branched bryozoans, as

*Sea bottom samples showing the occurrence of bioclastic deposits in the Ischia offshore.*

well as with small slags and volcanic glass (**Figure 5**).

The sampling data on rhodolith deposits have allowed to review previous interpretations of seismic lines in the offshore of Ischia [15]. At Ischia, the occurrence of isolated volcanic bodies, which include intrusions, domes and volcanic chimneys, was particularly complex to apply seismic and sequence stratigraphy in the interpretation of seismic data [37–39]. Volcanic bodies, which include lava flows, volcanic domes and volcanic intrusions, cannot be investigated by reflection

#### **Figure 6.**

*Detail of the seismic profile L57 (Ischia Bank), showing the seismic unit cropping out at the sea bottom, including the rhodolith deposits occurring at the top of the volcanic edifice.*

*Geochemistry*

#### **Figure 7.**

*Detail of the seismic profile L57 (Ischia Channel), showing the highstand deposits, Holocenic in age, within which the rhodolith deposits are inter-layered.*

seismic data, except for their external geometry, since they are mainly acousticallytransparent. On the contrary, the seismic facies of pyroclastic edifices and buried pyroclastic deposits can be identified, thanks to the inner stratification of the pyroclastic deposits.

On the Ischia Bank, the rhodolith deposits are probably included within an extensive wedge-shaped unit located at the top of the volcanic edifice, which unconformably overlies the volcanic rocky substratum, which characterizes the bank (**Figure 6**). This unit crops out at the sea bottom and can be interpreted as a unit consisting of bioclastic and partially rhodolith deposits. The volcanic rocky substratum, which characterizes the main morpho-structure of the Ischia Bank, is characterized by an acoustically-transparent seismic facies, corresponding with lavas and pyroclastites (**Figure 6**). On the south-western and north-eastern slopes of the bank there are thick sedimentary wedges, which, accordingly to the geometries observed on the seismic line, are respectively interpreted as trangressive deposits (retrogradational) on the south-western slope and as forced regression

**291**

**Figure 8.**

*bioconstructions.*

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New…*

In the Ischia Channel the rhodalgal facies are probably inter-stratified in the highstand deposits, which unconformably overlie the volcanic unit of the Ischia Channel. This unit was identified on the north-eastern section of the L57 seismic line, which runs from the Ischia Bank to the continental platform of Procida, crossing, in the Ischia Channel, the relict volcanic edifice of "Il Pertuso" (**Figure 7**). The volcanic unit of the Ischia Channel has been correlated with pyroclastites and lavas

In the Casamicciola offshore, the rhodolith deposits are represented by convex bodies, acoustically transparent, rooted in the top part of the seismic units interpreted as debris avalanches deposits (**Figure 8**). The acoustic facies and the rounded

wedges (progradational) on the northeastern escarpment (**Figure 6**). These deposits are not coeval, since the forced regression deposits are older than the transgressive deposits, which on the south-western slope of the bank have not been

genetically connected with the relict volcanic edifices of the Ischia Channel.

*Detail of the seismic profile L27 (Casamicciola offshore), showing the debris avalanche deposits (H1 and H2), within which the rhodolith deposits are inter-layered, appearing as mounds, representing algal* 

external appearance make them similar to algal bioconstructions.

*DOI: http://dx.doi.org/10.5772/intechopen.95083*

preserved.

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New… DOI: http://dx.doi.org/10.5772/intechopen.95083*

wedges (progradational) on the northeastern escarpment (**Figure 6**). These deposits are not coeval, since the forced regression deposits are older than the transgressive deposits, which on the south-western slope of the bank have not been preserved.

In the Ischia Channel the rhodalgal facies are probably inter-stratified in the highstand deposits, which unconformably overlie the volcanic unit of the Ischia Channel. This unit was identified on the north-eastern section of the L57 seismic line, which runs from the Ischia Bank to the continental platform of Procida, crossing, in the Ischia Channel, the relict volcanic edifice of "Il Pertuso" (**Figure 7**). The volcanic unit of the Ischia Channel has been correlated with pyroclastites and lavas genetically connected with the relict volcanic edifices of the Ischia Channel.

In the Casamicciola offshore, the rhodolith deposits are represented by convex bodies, acoustically transparent, rooted in the top part of the seismic units interpreted as debris avalanches deposits (**Figure 8**). The acoustic facies and the rounded external appearance make them similar to algal bioconstructions.

#### **Figure 8.**

*Geochemistry*

**290**

pyroclastic deposits.

*which the rhodolith deposits are inter-layered.*

**Figure 7.**

seismic data, except for their external geometry, since they are mainly acousticallytransparent. On the contrary, the seismic facies of pyroclastic edifices and buried pyroclastic deposits can be identified, thanks to the inner stratification of the

*Detail of the seismic profile L57 (Ischia Channel), showing the highstand deposits, Holocenic in age, within* 

On the Ischia Bank, the rhodolith deposits are probably included within an extensive wedge-shaped unit located at the top of the volcanic edifice, which unconformably overlies the volcanic rocky substratum, which characterizes the bank (**Figure 6**). This unit crops out at the sea bottom and can be interpreted as a unit consisting of bioclastic and partially rhodolith deposits. The volcanic rocky substratum, which characterizes the main morpho-structure of the Ischia Bank, is characterized by an acoustically-transparent seismic facies, corresponding with lavas and pyroclastites (**Figure 6**). On the south-western and north-eastern slopes of the bank there are thick sedimentary wedges, which, accordingly to the geometries observed on the seismic line, are respectively interpreted as trangressive deposits (retrogradational) on the south-western slope and as forced regression

*Detail of the seismic profile L27 (Casamicciola offshore), showing the debris avalanche deposits (H1 and H2), within which the rhodolith deposits are inter-layered, appearing as mounds, representing algal bioconstructions.*

#### **4. Discussion**

The bioclastic deposits of Ischia are here discussed and compared with similar deposits that are found in adjacent marine areas, with particular reference to the rhodolith layers. They represent detrital facies deriving mainly from in situ rearrangement processes of organogenic material on rocky sea bottoms. These deposits are composed of medium-coarse-grained sands and bioclastic gravels in a scarce pelitic matrix and crop out at the sea bottom in a portion of the inner shelf located at water depths between −20 m and −50 m, characterized by a prevalent carbonate sedimentation. Other significant outcrops are found on the morphological thresholds (Ischia Channel) and at the top of relict volcanic edifices, both in Ischia (Ischia and Forio Banks) and in Procida (La Catena, Il Pertuso and Vivara ants). Below water depths of −30 m the bioclastic deposits are rhodolith, characterized by gravels and lithoclastic sands, the biological component of which is made up of fragments of shells of mollusks (gastropods and lamellibranchs), echinoids and corals. Rhodolith deposits are often found near the *Posidonia oceanica* meadows and/or in protected areas near the rocky outcrops.

In particular, the Ischia Bank represents an excellent natural laboratory for the study of rhodolith deposits. On the Ischia Bank, below the *Posidonia oceanica* meadow, both bioclastic sands immersed in a muddy matrix and volcaniclastic gravels were sampled. The type of bioclastic sedimentation present in this area is characteristic, since the most of the carbonate shells, which come from the overlying meadow, settle at the net limit between the meadow and the sea bottom, where sands and bioclastic gravels crop out. Both the mollusk shells and the volcaniclastic fragments, where the contribution of the silty and sandy fractions is lower than 20%, were colonized by some species of red algae, while in the marine areas with a low gradient a maërl facies was deposited.

The sedimentological results obtained on the rhodolith layers are in agreement with the previous data on rhodolith deposits in the Mediterranean area [40], with particular reference to the southern Tyrrhenian Sea [5, 40], and to the Gulf of Naples [18, 19, 29–31]. In the Mediterranean area the rhodoliths were found in the eastern and western sub-basins at water depths of −30 m to −75 m, but also extend to water depths greater than −75 m [40, 41]. Rhodolith layers were reported in the most of the coastal sections of the Mediterranean, while they are missing along the coasts of the eastern Adriatic sea, Egypt, Syria, Lebanon and the Black Sea [40, 41]. Rindi et al. [41] that in the Mediterranean sea these deposits have shown a high spatial and bathymetric extension, also if the biocostructions of coralline algae virtually occur in all seas. Moreover, these authors have addressed specific research issues in future works, including more detailed paleontological studies, a more accurate taxonomic reassessment, and the extension of the studies on the effects of the climate change and acidification on a wider set of species.

Bracchi & Basso [5] have discussed the occurrence of calcareous algae on the Tyrrhenian continental shelf (Pontine Islands), finding two different carbonate facies, namely the coralline algae facies and the carbonate matrix facies. These authors have highlighted that the Pontine Islands represent a mobile sea bottom of the littoral zone, accordingly with the classification proposed by Peres & Picard [11]. The corresponding biocenosis has been called "Détritique Cotier" and is typically composed of a mixture of sands, gravels and muds. Furthermore, a moderate variability of sedimentary facies, in particular of sands dominated by biogenic carbonates, has been suggested in this area [33]. In this area of the Tyrrhenian Sea, coralline algae represent the most important control factor in the production of carbonate sediments and are typically found in a depth range between −40 m to −70 m. These

**293**

ric data.

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New…*

water depths are consistent with the depths of the rhodolith deposits found in the

In the marine area of the Nisida inlet and Posillipo offshore (Nisida Bank; Cavallara saddle), previously reported by Walther [18] as an area of massive discovery of rhodolith deposits on the rocky outcrops and on the surrounding sea bottom, pyroclastic gravels are frequently mixed with rhodolith deposits characterized by living red algae. The rhodalgal facies is mainly composed of dead, fallen or transported thalli from submerged rocky outcrops, which are colonized in a variable way. In addition, the biogenic fraction is composed of sandy skeletal assemblages, forming variable types of deposits, which have undergone an intense mechanical

Various types of rhodalgal facies have been found in the Miseno Bank area (Gulf of Pozzuoli). In correspondence with the rocky outcrops, live thalli were found, difficult to sample. On the surrounding sea bottom, characterized by gravels and bioclastic sands, palimpsest deposits were sampled, formed by bioclastic sands. In particular, the presence of a palimpsest drapes, consisting of fragments of algal

On the Ischia Bank, whose top is found at water depths between −28 m and −30 m, there is a living *Posidonia oceanica* meadow, extending down to −40 m of water depth. In correspondence with the channellised areas, where the *Posidonia oceanica* meadow is lacking, there are extensive fields of sandy ripples. Rhodolith deposits were found below the *Posidonia oceanica* meadow, characterized by living coralline algae (*Phymatolithon calcareum*, *Lithotamnion corallioides*, *Lithotamnion minervae*, *Lythophyllum racemes*) [29]. The rhodolith layers are well developed,

The geological and sedimentological data have shown that around the Ischia island the rhodolith deposits have been controlled by different geomorphological and hydrological settings, which have influenced the variable structure of the coralline algae. Among these control factors, the most important one is represented by the topography of the seafloor, deeply influencing the stratigraphic architecture of the rhodolith deposits. Based on the studied data these deposits mainly occur next to the relict volcanic edifices, to the morphological thresholds and to the rough morphologies occurring at the sea bottom corresponding with the outcrops of

In the Ischia offshore the best developed rhodalgal carbonate factory has been found on the outermost bank (Ischia Bank), lacking of the fine-grained fraction and subjected to an intense action of the currents at the head of the adjacent tributary channel, where a part of the biogenic sands are locally transported towards the head of the Magnaghi canyon. Palimpsest deposits or partially remobilized deposits have been found on some other banks (Miseno and Nisida - La Cavallara), where the fine-grained fraction or the geomorphological characteristics have prevented the formation of an active carbonate production by red algae. The Forio Bank, located in the western offshore of Ischia, has shown rhodolith deposits similar to those ones found on the Ischia Bank, but to a smaller scale, having more limited dimensions with respect to the Ischia Bank, as suggested by Multibeam bathymet-

In the northern sector of Ischia (Casamicciola) the seismic data have suggested

that the rhodolith deposits and, as a general rule, the bioclastic deposits have rounded-shaped morphologies, corresponding with algal bioconstructions and are rooted within the seismic units of debris avalanches. Further data on these deposits in the northern sector of Ischia have been highlighted by Babbini et al. [30] and Gambi et al. [31]. These authors have reported the occurrence of a maërl facies in

*DOI: http://dx.doi.org/10.5772/intechopen.95083*

Ischia offshore and discussed in this work.

thalli and invertebrate shells has been reported.

debris avalanche deposits [42].

covering a gravelly sea bottom, formed by mollusk shells.

degradation.

#### *Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New… DOI: http://dx.doi.org/10.5772/intechopen.95083*

water depths are consistent with the depths of the rhodolith deposits found in the Ischia offshore and discussed in this work.

In the marine area of the Nisida inlet and Posillipo offshore (Nisida Bank; Cavallara saddle), previously reported by Walther [18] as an area of massive discovery of rhodolith deposits on the rocky outcrops and on the surrounding sea bottom, pyroclastic gravels are frequently mixed with rhodolith deposits characterized by living red algae. The rhodalgal facies is mainly composed of dead, fallen or transported thalli from submerged rocky outcrops, which are colonized in a variable way. In addition, the biogenic fraction is composed of sandy skeletal assemblages, forming variable types of deposits, which have undergone an intense mechanical degradation.

Various types of rhodalgal facies have been found in the Miseno Bank area (Gulf of Pozzuoli). In correspondence with the rocky outcrops, live thalli were found, difficult to sample. On the surrounding sea bottom, characterized by gravels and bioclastic sands, palimpsest deposits were sampled, formed by bioclastic sands. In particular, the presence of a palimpsest drapes, consisting of fragments of algal thalli and invertebrate shells has been reported.

On the Ischia Bank, whose top is found at water depths between −28 m and −30 m, there is a living *Posidonia oceanica* meadow, extending down to −40 m of water depth. In correspondence with the channellised areas, where the *Posidonia oceanica* meadow is lacking, there are extensive fields of sandy ripples. Rhodolith deposits were found below the *Posidonia oceanica* meadow, characterized by living coralline algae (*Phymatolithon calcareum*, *Lithotamnion corallioides*, *Lithotamnion minervae*, *Lythophyllum racemes*) [29]. The rhodolith layers are well developed, covering a gravelly sea bottom, formed by mollusk shells.

The geological and sedimentological data have shown that around the Ischia island the rhodolith deposits have been controlled by different geomorphological and hydrological settings, which have influenced the variable structure of the coralline algae. Among these control factors, the most important one is represented by the topography of the seafloor, deeply influencing the stratigraphic architecture of the rhodolith deposits. Based on the studied data these deposits mainly occur next to the relict volcanic edifices, to the morphological thresholds and to the rough morphologies occurring at the sea bottom corresponding with the outcrops of debris avalanche deposits [42].

In the Ischia offshore the best developed rhodalgal carbonate factory has been found on the outermost bank (Ischia Bank), lacking of the fine-grained fraction and subjected to an intense action of the currents at the head of the adjacent tributary channel, where a part of the biogenic sands are locally transported towards the head of the Magnaghi canyon. Palimpsest deposits or partially remobilized deposits have been found on some other banks (Miseno and Nisida - La Cavallara), where the fine-grained fraction or the geomorphological characteristics have prevented the formation of an active carbonate production by red algae. The Forio Bank, located in the western offshore of Ischia, has shown rhodolith deposits similar to those ones found on the Ischia Bank, but to a smaller scale, having more limited dimensions with respect to the Ischia Bank, as suggested by Multibeam bathymetric data.

In the northern sector of Ischia (Casamicciola) the seismic data have suggested that the rhodolith deposits and, as a general rule, the bioclastic deposits have rounded-shaped morphologies, corresponding with algal bioconstructions and are rooted within the seismic units of debris avalanches. Further data on these deposits in the northern sector of Ischia have been highlighted by Babbini et al. [30] and Gambi et al. [31]. These authors have reported the occurrence of a maërl facies in

*Geochemistry*

**4. Discussion**

The bioclastic deposits of Ischia are here discussed and compared with similar deposits that are found in adjacent marine areas, with particular reference to the rhodolith layers. They represent detrital facies deriving mainly from in situ rearrangement processes of organogenic material on rocky sea bottoms. These deposits are composed of medium-coarse-grained sands and bioclastic gravels in a scarce pelitic matrix and crop out at the sea bottom in a portion of the inner shelf located at water depths between −20 m and −50 m, characterized by a prevalent carbonate sedimentation. Other significant outcrops are found on the morphological thresholds (Ischia Channel) and at the top of relict volcanic edifices, both in Ischia (Ischia and Forio Banks) and in Procida (La Catena, Il Pertuso and Vivara ants). Below water depths of −30 m the bioclastic deposits are rhodolith, characterized by gravels and lithoclastic sands, the biological component of which is made up of fragments of shells of mollusks (gastropods and lamellibranchs), echinoids and corals. Rhodolith deposits are often found near the *Posidonia oceanica* meadows

In particular, the Ischia Bank represents an excellent natural laboratory for the study of rhodolith deposits. On the Ischia Bank, below the *Posidonia oceanica* meadow, both bioclastic sands immersed in a muddy matrix and volcaniclastic gravels were sampled. The type of bioclastic sedimentation present in this area is characteristic, since the most of the carbonate shells, which come from the overlying meadow, settle at the net limit between the meadow and the sea bottom, where sands and bioclastic gravels crop out. Both the mollusk shells and the volcaniclastic fragments, where the contribution of the silty and sandy fractions is lower than 20%, were colonized by some species of red algae, while in the marine areas with a

The sedimentological results obtained on the rhodolith layers are in agreement with the previous data on rhodolith deposits in the Mediterranean area [40], with particular reference to the southern Tyrrhenian Sea [5, 40], and to the Gulf of Naples [18, 19, 29–31]. In the Mediterranean area the rhodoliths were found in the eastern and western sub-basins at water depths of −30 m to −75 m, but also extend to water depths greater than −75 m [40, 41]. Rhodolith layers were reported in the most of the coastal sections of the Mediterranean, while they are missing along the coasts of the eastern Adriatic sea, Egypt, Syria, Lebanon and the Black Sea [40, 41]. Rindi et al. [41] that in the Mediterranean sea these deposits have shown a high spatial and bathymetric extension, also if the biocostructions of coralline algae virtually occur in all seas. Moreover, these authors have addressed specific research issues in future works, including more detailed paleontological studies, a more accurate taxonomic reassessment, and the extension of the studies on the effects of

Bracchi & Basso [5] have discussed the occurrence of calcareous algae on the Tyrrhenian continental shelf (Pontine Islands), finding two different carbonate facies, namely the coralline algae facies and the carbonate matrix facies. These authors have highlighted that the Pontine Islands represent a mobile sea bottom of the littoral zone, accordingly with the classification proposed by Peres & Picard [11]. The corresponding biocenosis has been called "Détritique Cotier" and is typically composed of a mixture of sands, gravels and muds. Furthermore, a moderate variability of sedimentary facies, in particular of sands dominated by biogenic carbonates, has been suggested in this area [33]. In this area of the Tyrrhenian Sea, coralline algae represent the most important control factor in the production of carbonate sediments and are typically found in a depth range between −40 m to −70 m. These

and/or in protected areas near the rocky outcrops.

low gradient a maërl facies was deposited.

the climate change and acidification on a wider set of species.

**292**

the north-western sector of Ischia and in particular, in the offshore of Forio and in the San Francesco area on the basis of samples carried out at water depths between −50 m and −80 m. The microscopic characterization of these deposits has shown the occurrence of well-pigmented thalli and of variable morphologies (crusty, lumpy, mammellate, arborescent). The maërl facies looks like an accumulation of whole thalli of calcareous algae or fragments of calcareous algae, which often accumulate within the concavities of the rocky substratum. Furthermore, the ROV images collected in the Forio area (western offshore of Ischia) have shown the occurrence of important algal accumulations within the concavities of the ripple marks, occurring on the sandy bottoms [30]. Assemblages of very well diversified benthic organisms are associated with this facies [31], typical of the "Détritique Cotier" and "Détritique Du Large" biocenosis.

Moreover the obtained results have been compared with the distribution and characterization of rhodolith beds off the Campania region [43]. In the Gulf of Naples these authors have studied and described four selected sites, represented by Capri, Punta Campanella, Secchitiello, and Ischia. In particular, regarding Ischia, the authors have correlated their results with the data previously obtained by Babbini et al. [30] and Gambi et al. [31], which have singled out the occurrence of three morpho-types of rhodoliths, with a prevalence of unattached branches of *Phymatolithon calcareum* and *Lithothamnion corallioides*. In addition, Rendina et al. [43] have underlined a high percentage of dead thalli of red algae, accompanying the alive rhodoliths, suggesting that this percentage has been controlled by a high fraction of fine-grained sediments, triggering the burial of the rhodolith deposits.

The importance of the geomorphological and topographic control factors in controlling the stratigraphic architecture of the rhodolith deposits has been recently highlighted for extra-Mediterranean examples (Udo Island, Korea) [44], suggesting that the distribution of the rhodolith deposits is strongly affected by both the topography of the sea bottom and related physical energy and by different types of surface sediments. In particular, these authors have suggested that a bedrock exposed area is covered by alive rhodoliths (water depths up to – 10 m), where a rough topography of the sea bottom has prevented for a continuous growth of rhodoliths. An active growth area of alive rhodoliths and a sand dune area with dead rhodoliths have been suggested at water depths ranging between – 10 m and – 15 m. While the first area provides stable conditions for the growth of the rhodoliths, the second one represents an adverse environment for the development of rhodoliths. The seagrass covered area with alive rhodoliths develops at water depths greater than – 15 m, where various sizes of rhodoliths have been found.

#### **5. Concluding remarks**

The Ischia Bank is characterized by an active carbonate factory dominated by coralline algae, which have colonized an area where suitable environmental conditions have been established for the deposition of native and living rhodalgal deposits. The rhodalgal deposits are locally abundant and are mostly deposited in situ with a centimeter thickness.

Although in the Ischia offshore the investigated deposits were found in a similar bathymetric range, these deposits have shown how in different geomorphological and hydrological environment the coralline algae facies have different structures. Moreover, the topography of the sea bottom has controlled the stratigraphic architecture of these deposits (relict volcanic edifices, morphological tresholds, rough topographies controlled by the development of debris avalanche deposits).

**295**

**Author details**

Gemma Aiello

Procida.

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New…*

Although qualitatively, the correlation between the sampling data and the interpretation of seismic profiles, previously interpreted and reviewed here, has suggested that the rhodolith deposits are inter-stratified within large seismic units, cropping out at the sea bottom or sub-surficial. In particular, on the Ischia Bank these deposits are inter-layered in a wedge-shaped unit located at the top of the volcanic bank. This unit unconformably overlies the acoustic rocky substratum, representing the main stratigraphic bulk of the bank. Although not documented by the seismic profiles, but only through sea bottom samples, the rhodolith deposits were also found at the top of the parasitic vent, genetically connected to the main

In the Ischia Channel the rhodolith deposits are presumably inter-layered with the highstand deposits, represented by a thick seismic unit partly cropping out at the sea bottom. This unit overlies volcanic seismic units of a probable pyroclastic nature, which are deposited within depressed palaeo-morphologies and which are probably correlated with the yellow tuffs of Solchiaro, cropping out onshore in

Istituto di Scienze Marine (ISMAR), Consiglio Nazionale delle Ricerche (CNR),

\*Address all correspondence to: gemma.aiello@cnr.it; gemmaiello@virgilio.it

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Calata Porta di Massa, Porto di Napoli, 80133, Napoli, Italy

provided the original work is properly cited.

*DOI: http://dx.doi.org/10.5772/intechopen.95083*

building of the Ischia Bank volcanic edifice.

#### *Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New… DOI: http://dx.doi.org/10.5772/intechopen.95083*

Although qualitatively, the correlation between the sampling data and the interpretation of seismic profiles, previously interpreted and reviewed here, has suggested that the rhodolith deposits are inter-stratified within large seismic units, cropping out at the sea bottom or sub-surficial. In particular, on the Ischia Bank these deposits are inter-layered in a wedge-shaped unit located at the top of the volcanic bank. This unit unconformably overlies the acoustic rocky substratum, representing the main stratigraphic bulk of the bank. Although not documented by the seismic profiles, but only through sea bottom samples, the rhodolith deposits were also found at the top of the parasitic vent, genetically connected to the main building of the Ischia Bank volcanic edifice.

In the Ischia Channel the rhodolith deposits are presumably inter-layered with the highstand deposits, represented by a thick seismic unit partly cropping out at the sea bottom. This unit overlies volcanic seismic units of a probable pyroclastic nature, which are deposited within depressed palaeo-morphologies and which are probably correlated with the yellow tuffs of Solchiaro, cropping out onshore in Procida.

### **Author details**

*Geochemistry*

the north-western sector of Ischia and in particular, in the offshore of Forio and in the San Francesco area on the basis of samples carried out at water depths between −50 m and −80 m. The microscopic characterization of these deposits has shown the occurrence of well-pigmented thalli and of variable morphologies (crusty, lumpy, mammellate, arborescent). The maërl facies looks like an accumulation of whole thalli of calcareous algae or fragments of calcareous algae, which often accumulate within the concavities of the rocky substratum. Furthermore, the ROV images collected in the Forio area (western offshore of Ischia) have shown the occurrence of important algal accumulations within the concavities of the ripple marks, occurring on the sandy bottoms [30]. Assemblages of very well diversified benthic organisms are associated with this facies [31], typical of the "Détritique

Moreover the obtained results have been compared with the distribution and characterization of rhodolith beds off the Campania region [43]. In the Gulf of Naples these authors have studied and described four selected sites, represented by Capri, Punta Campanella, Secchitiello, and Ischia. In particular, regarding Ischia, the authors have correlated their results with the data previously obtained by Babbini et al. [30] and Gambi et al. [31], which have singled out the occurrence of three morpho-types of rhodoliths, with a prevalence of unattached branches of *Phymatolithon calcareum* and *Lithothamnion corallioides*. In addition, Rendina et al. [43] have underlined a high percentage of dead thalli of red algae, accompanying the alive rhodoliths, suggesting that this percentage has been controlled by a high fraction of fine-grained sediments, triggering the burial of

The importance of the geomorphological and topographic control factors in controlling the stratigraphic architecture of the rhodolith deposits has been recently highlighted for extra-Mediterranean examples (Udo Island, Korea) [44], suggesting that the distribution of the rhodolith deposits is strongly affected by both the topography of the sea bottom and related physical energy and by different types of surface sediments. In particular, these authors have suggested that a bedrock exposed area is covered by alive rhodoliths (water depths up to – 10 m), where a rough topography of the sea bottom has prevented for a continuous growth of rhodoliths. An active growth area of alive rhodoliths and a sand dune area with dead rhodoliths have been suggested at water depths ranging between – 10 m and – 15 m. While the first area provides stable conditions for the growth of the rhodoliths, the second one represents an adverse environment for the development of rhodoliths. The seagrass covered area with alive rhodoliths develops at water depths greater

The Ischia Bank is characterized by an active carbonate factory dominated by coralline algae, which have colonized an area where suitable environmental conditions have been established for the deposition of native and living rhodalgal deposits. The rhodalgal deposits are locally abundant and are mostly deposited in

Although in the Ischia offshore the investigated deposits were found in a similar bathymetric range, these deposits have shown how in different geomorphological and hydrological environment the coralline algae facies have different structures. Moreover, the topography of the sea bottom has controlled the stratigraphic architecture of these deposits (relict volcanic edifices, morphological tresholds, rough topographies controlled by the development of debris avalanche deposits).

than – 15 m, where various sizes of rhodoliths have been found.

Cotier" and "Détritique Du Large" biocenosis.

the rhodolith deposits.

**5. Concluding remarks**

situ with a centimeter thickness.

**294**

Gemma Aiello Istituto di Scienze Marine (ISMAR), Consiglio Nazionale delle Ricerche (CNR), Calata Porta di Massa, Porto di Napoli, 80133, Napoli, Italy

\*Address all correspondence to: gemma.aiello@cnr.it; gemmaiello@virgilio.it

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

[1] Kamenos N A, Burdett H L, Darrenougue N Coralline Algae as Recorders of Past Climatic and Environmental Conditions. In: Riosmena-Rodriguez R, Nelson W, Aguirre J, editors. Rhodolith/Maerl Beds: A Global Perspective. Coastal Research Library, 2017; 15, p. 27-54.

[2] Martin S, Hall-Spencer J M Effects of Ocean Warming and Acidification of Rhodolith/Maerl Beds. In: Riosmena-Rodriguez R, Nelson W, Aguirre J, editors. Rhodolith/Maerl Beds: A Global Perspective. Coastal Research Library, 2017; 15, p. 55-86.

[3] Riosmena-Rodriguez R, Nelson W, Aguirre J, editors. Rhodolith/Maerl Beds: A Global Perspective. Coastal Research Library, 2017; 15, p. 1-359.

[4] Carannante G, Esteban M, Milliman J D, Simone L: Carbonate lithofacies as a paleolatitude indicators: problems and limitations. Sedimentary Geology. 1988; 60:333-346.

[5] Bracchi V A, Basso D: The contribution of calcareous algae to the biogenic carbonates of the continental shelf: Pontine Islands, Tyrrhenian Sea, Italy. Geodiversitas, 2012; 34 (1): 61-76.

[6] Pomar L: Types of carbonate platforms: a genetic approach. Basin Research, 2001; 13 (3): 313-334.

[7] Basso D, Morbioli C, Corselli C Rhodolith facies evolution and burial as a response to Holocene transgression at the Pontiane Islands shelf break. In: Pedley H M., Carannante G, editors, Cool-water carbonates: depositional systems and palaeoenvironmental control. Geological Society of London Special Publication, 2006; 255, p. 23-34.

[8] Pomar L, Baceta J I, Hallock P, Mateu-Vicens G, Basso D: Reef building and carbonate production modes in

the west-central Tethys during the Cenozoic. Marine and Petroleum Geology, 2017; 83: 261-304.

[9] Aguirre J, Braga J C, Bassi D Rhodolits and Rhodolith Beds in the Rock Record. In: Riosmena-Rodriguez R, Nelson W, Aguirre J, editors, Rhodolith/Maerl Beds: A Global Perspective. Coastal Research Library, 2017; 15, p. 105-138.

[10] Brandano M, Cornacchia I, Tomassetti L: Global versus regional influence on the carbonate factories of Oligo-Miocene carbonate platforms in the Mediterranean area. Marine and Petroleum Geology, 2017; 87: 188-202.

[11] Peres J M, Picard J Noveau manuel de bionomie marine benthique de la Mer Méditerranee. Recueil des Travaux de la Station Marine d'Endoume, 1964;

[12] Halfar J, Mutti M: Global dominance of coralline red-algal facies: A response to Miocene oceanographic events. Geology, 2005; 33 (6): 481-484; doi: 10.1130/G21462.1.

[13] Sbrana A, Toccaceli R M, Biagio G, Cubellis E, Faccenna C, Fedi M, Florio G, Fulignati P, Giordano F, Giudetti G, Grimaldi M, Italiano F, Luperini W, Marianelli P, Buia M C, Donadio C, Gambi M C, Putignano M L, Aiello G, Budillon F, Conforti A, D'Argenio B (2011) Geological sheet of Ischia, scale 1:10.000 – Geological sheet and explanatory notes. Region Campania, Sector of Soil Defense, Geothermics and Geotechnics, 2011; Naples, Italy.

[14] Bruno P P G, de Alteriis G, Florio G: The western undersea section of the Ischia volcanic complex (Italy, Tyrrhenian sea) inferred by marine geophysical data. Geophysical Research Letters, 2002; 29 (9): 1343, doi 10.1029/2001GL013904.

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[28] Pescatore T, Diplomatico G, Senatore M R, Tramutoli M, Mirabile L: Contributi allo studio del Golfo di Pozzuoli: aspetti stratigrafici e strutturali. Memorie della Società Geologica Italiana, 1984; 27: 133-149.

[29] Toscano F, Vigliotti M, Simone L Variety of coralline algal deposits (rhodalgal facies) from the Bays of Naples and Pozzuoli (northern Tyrrhenian sea, Italy). In: Pedley H M., Carannante G, editors, Cool-water carbonates: depositional systems and palaeoenvironmental control. Geological Society of London Special Publication, 2006; 255, p. 85-94.

[30] Babbini L, Bressan G,

[31] Gambi M C, Buia M C, Massa-Gallucci A, Cigliano M, Lattanzi L, Patti F P The "pink mile": benthic assemblages of Rhodolith and

Massa-Gallucci A, Buia M C, Gambi M C: Segnalazione di una facies a maërl (*Rodophyta, Corallinales*) lungo le coste dell'isola d'Ischia. Biologia Marina Mediterranea, 2006; 13 (1): 548-552.

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*DOI: http://dx.doi.org/10.5772/intechopen.95083*

[16] Sbrana A, Marianelli P, Pasquini G: Volcanology of Ischia (Italy). Journal of

[17] Aiello G: New insights on the Late Quaternary geologic evolution of the Ischia Island coastal belt based on high-resolution seismic profiles. Italian Journal of Geosciences, 2018a; 137 (1):

[18] Walther J: Le alghe calcarifere litoproduttrici del Golfo di Napoli e l'origine di certi calcarei compatti. Bollettino Regio Comitato Geologico

[19] Funk G: Die algenvegetation des Golf von Neapel. Pubblicazioni della Stazione Zoologica di Napoli, 1927;

[20] Funk G Beitrage zur kenntnis der meeresalgen von Neapel. Pubblicazioni della Stazione Zoologica di Napoli, 1955;

[21] Bacci G: Ricerche sulle zoocenosi bentoniche del Golfo di Napoli – La secca di Penta Palummo. Pubblicazioni della Stazione Zoologica di Napoli, 1947;

[22] Lewalle J: Determination macroscopique des algues rouges calcaires (Corallinaceae et

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[23] Segre A G: Geological map of Italy, Sheet n. 183-184. Ischia, Naples. Geological Survey of Italy, 1967; Rome,

[24] Segre A G: The bathymetric map of the Gulf of Pozzuoli. Hydrographic

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Suppl. 7: 1-507.

Suppl. 25: 1-178.

20: 158-178.

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87 106.

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*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New… DOI: http://dx.doi.org/10.5772/intechopen.95083*

[15] Aiello G, Marsella E, Passaro S: Stratigraphic and structural setting of the Ischia volcanic complex (Naples Bay, southern Italy) revealed by submarine seismic reflection data. Rendiconti Lincei, 2012; 23 (4): 387-408.

[16] Sbrana A, Marianelli P, Pasquini G: Volcanology of Ischia (Italy). Journal of Maps, 2018; 14 (2): 494-503.

[17] Aiello G: New insights on the Late Quaternary geologic evolution of the Ischia Island coastal belt based on high-resolution seismic profiles. Italian Journal of Geosciences, 2018a; 137 (1): 87 106.

[18] Walther J: Le alghe calcarifere litoproduttrici del Golfo di Napoli e l'origine di certi calcarei compatti. Bollettino Regio Comitato Geologico d'Italia, 1885; 16: 360-369.

[19] Funk G: Die algenvegetation des Golf von Neapel. Pubblicazioni della Stazione Zoologica di Napoli, 1927; Suppl. 7: 1-507.

[20] Funk G Beitrage zur kenntnis der meeresalgen von Neapel. Pubblicazioni della Stazione Zoologica di Napoli, 1955; Suppl. 25: 1-178.

[21] Bacci G: Ricerche sulle zoocenosi bentoniche del Golfo di Napoli – La secca di Penta Palummo. Pubblicazioni della Stazione Zoologica di Napoli, 1947; 20: 158-178.

[22] Lewalle J: Determination macroscopique des algues rouges calcaires (Corallinaceae et Squamarciacae partim) du Golfe de Naples. Pubblicazioni della Stazione Zoologica di Napoli, 1961; 32: 241-271.

[23] Segre A G: Geological map of Italy, Sheet n. 183-184. Ischia, Naples. Geological Survey of Italy, 1967; Rome, Italy.

[24] Segre A G: The bathymetric map of the Gulf of Pozzuoli. Hydrographic Institute of the Italian Navy, Genova, Italy, 1972; F.C., 1053, 1-12.

[25] Buccheri G, De Stefano E: Contributi allo studio del Golfo di Pozzuoli. Pteropodi e nannoplancton calcareo contenuti in tre carote: considerazioni ambientali e biostratigrafiche. Memorie della Società Geologica Italiana, 1984; 27: 181-193.

[26] De Pippo T, De Cara A, Guida M, Pescatore T, Renda P: Contributi allo studio del Golfo di Pozzuoli: lineamenti di geomorfologia. Memorie della Società Geologica Italiana, 1984; 27:151-159.

[27] Pennetta M, Pescatore T, Vecchione C: Contributi allo studio del Golfo di Pozzuoli: caratteristiche tessiturali dei sedimenti superficiali. Memorie della Società Geologica Italiana, 1984; 27: 161-169.

[28] Pescatore T, Diplomatico G, Senatore M R, Tramutoli M, Mirabile L: Contributi allo studio del Golfo di Pozzuoli: aspetti stratigrafici e strutturali. Memorie della Società Geologica Italiana, 1984; 27: 133-149.

[29] Toscano F, Vigliotti M, Simone L Variety of coralline algal deposits (rhodalgal facies) from the Bays of Naples and Pozzuoli (northern Tyrrhenian sea, Italy). In: Pedley H M., Carannante G, editors, Cool-water carbonates: depositional systems and palaeoenvironmental control. Geological Society of London Special Publication, 2006; 255, p. 85-94.

[30] Babbini L, Bressan G, Massa-Gallucci A, Buia M C, Gambi M C: Segnalazione di una facies a maërl (*Rodophyta, Corallinales*) lungo le coste dell'isola d'Ischia. Biologia Marina Mediterranea, 2006; 13 (1): 548-552.

[31] Gambi M C, Buia M C, Massa-Gallucci A, Cigliano M, Lattanzi L, Patti F P The "pink mile": benthic assemblages of Rhodolith and

**296**

*Geochemistry*

**References**

[1] Kamenos N A, Burdett H L, Darrenougue N Coralline Algae as Recorders of Past Climatic and Environmental Conditions. In: Riosmena-Rodriguez R, Nelson W, Aguirre J, editors. Rhodolith/Maerl Beds: A Global Perspective. Coastal Research Library, 2017; 15, p. 27-54. the west-central Tethys during the Cenozoic. Marine and Petroleum Geology, 2017; 83: 261-304.

[9] Aguirre J, Braga J C, Bassi D Rhodolits and Rhodolith Beds in the Rock Record. In: Riosmena-Rodriguez R, Nelson W, Aguirre J, editors, Rhodolith/Maerl Beds: A Global Perspective. Coastal Research Library, 2017; 15, p. 105-138.

[10] Brandano M, Cornacchia I, Tomassetti L: Global versus regional influence on the carbonate factories of Oligo-Miocene carbonate platforms in the Mediterranean area. Marine and Petroleum Geology, 2017; 87: 188-202.

[11] Peres J M, Picard J Noveau manuel

[12] Halfar J, Mutti M: Global dominance of coralline red-algal facies: A response to Miocene oceanographic events. Geology, 2005; 33 (6): 481-484; doi:

[13] Sbrana A, Toccaceli R M, Biagio G, Cubellis E, Faccenna C, Fedi M, Florio G, Fulignati P, Giordano F, Giudetti G, Grimaldi M, Italiano F, Luperini W, Marianelli P, Buia M C, Donadio C, Gambi M C, Putignano M L, Aiello G, Budillon F, Conforti A, D'Argenio B (2011) Geological sheet of Ischia, scale 1:10.000 – Geological sheet and explanatory notes. Region Campania, Sector of Soil Defense, Geothermics and

Geotechnics, 2011; Naples, Italy.

Letters, 2002; 29 (9): 1343, doi 10.1029/2001GL013904.

[14] Bruno P P G, de Alteriis G, Florio G: The western undersea section of the Ischia volcanic complex (Italy, Tyrrhenian sea) inferred by marine geophysical data. Geophysical Research

de bionomie marine benthique de la Mer Méditerranee. Recueil des Travaux de la Station Marine

d'Endoume, 1964;

10.1130/G21462.1.

[2] Martin S, Hall-Spencer J M Effects of Ocean Warming and Acidification

[3] Riosmena-Rodriguez R, Nelson W, Aguirre J, editors. Rhodolith/Maerl Beds: A Global Perspective. Coastal Research Library, 2017; 15, p. 1-359.

[4] Carannante G, Esteban M, Milliman J D, Simone L: Carbonate lithofacies as a paleolatitude indicators: problems and limitations. Sedimentary Geology. 1988;

contribution of calcareous algae to the biogenic carbonates of the continental shelf: Pontine Islands, Tyrrhenian Sea, Italy. Geodiversitas, 2012; 34 (1): 61-76.

[5] Bracchi V A, Basso D: The

[6] Pomar L: Types of carbonate platforms: a genetic approach. Basin Research, 2001; 13 (3): 313-334.

[7] Basso D, Morbioli C, Corselli C Rhodolith facies evolution and burial as a response to Holocene transgression at the Pontiane Islands shelf break. In: Pedley H M., Carannante G, editors, Cool-water carbonates: depositional systems and palaeoenvironmental control. Geological Society of London Special Publication, 2006; 255, p. 23-34.

[8] Pomar L, Baceta J I, Hallock P, Mateu-Vicens G, Basso D: Reef building and carbonate production modes in

60:333-346.

of Rhodolith/Maerl Beds. In: Riosmena-Rodriguez R, Nelson W, Aguirre J, editors. Rhodolith/Maerl Beds: A Global Perspective. Coastal Research Library, 2017; 15, p. 55-86.

Mäerl beds (Corallinales) off the island of Ischia (Tyrrhenian Sea). UNEP-MAP-RAC/SPA Proceedings of the 1st Mediterranean Symposium on the Coralligenous and other calcareous bioconcretions of the Mediterranean Sea, Tabarka, 15-16 January 2009, CAR/ASP publication, Tunisi, p. 197-200.

[32] Colantoni P, Gallignani P, Fresi E, Cinelli F: Patterns of Posidonia oceanica (L.) DELILE beds around of the Island of Ischia (Gulf of Naples) and in adjacent waters. Marine Ecology, 1982; 3, (1): 53-74.

[33] Brandano M, Civitelli G: Non sea-grass meadow sedimentary facies on the Pontian Islands, Tyrrhenian sea: a modern example of mixed carbonatesiliciclastic sedimentation. Sedimentary Geology, 2007; 201: 286-310.

[34] Brandano M, Tomassetti L, Mateu-Vicens G, Gagliano G: The seagrass skeletal assemblage from modern to fossil and from tropical to temperate: Insight from Maldivian and Mediterranean examples. Sedimentology, 2019; 66 (6): 2268-2296.

[35] Aiello G: Marine geological maps of the Campania Region (Southern Tyrrhenian sea, Italy): considerations and contributions to a different scale of geological survey. Journal of Geography and Cartography, 2018b; 1 (3), doi:10.24294/jgc.v1i3.507.

[36] Ferraro L, Molisso F Sedimenti ed associazioni a foraminiferi bentonici di settori selezionati della piattaforma continentale dell'Isola d'Ischia (Tirreno meridionale). In: Gambi M C, De Lauro M, Iannuzzi F, editors, Ambiente Marino Costiero e Territorio delle Isole Flegree (Ischia Procida Vivara – Golfo di Napoli). Risultati di uno studio multidisciplinare. Memorie Accademia Scienze Fisiche e Matematiche in Napoli, 2003; 5, p. 67-82.

[37] Vail P R, Mitchum R M, Todd R G, Widmier J M, Thompson S, Sangree J

B, Bubb J N Seismic stratigraphy and global change of sea level. In: Payton C E, editor, Seismic stratigraphy applications to hydrocarbon exploration, AAPG Memory, 1977; 26, p. 49-116.

[38] Mitchum J R, Vail P R, Sangree J B (1977) Stratigraphic interpretation of seismic reflection pattern in depositional sequences. In: Payton C E, editor, Seismic stratigraphy applications to hydrocarbon exploration, AAPG Memory, 1977; 26, p. 117-134.

[39] Catuneanu O, Galloway W E, Kendall C G, Miall A D, Posamentier H W, Strasser A, Tucker M E Sequence Stratigraphy: Methodology and Nomenclature. Newsletters on Stratigraphy, 2011; 44 (3): 173-245.

[40] Basso D, Babbini L, Ramos-Espla A A, Salomidi M Mediterranean Rhodolith Beds. In: Riosmena-Rodriguez R, Nelson W, Aguirre J, editors. Rhodolith/ Maerl Beds: A Global Perspective. Coastal Research Library, 2017; 15, p. 281-298.

[41] Rindi F, Braga J C, Martin S, Pena V, Le Gall L, Caragnano A, Aguirre J Coralline Algae in a Changing Mediterranean Sea: How Can We Predict Their Future, if We Do Not Know Their Present? Frontiers in Marine Sciences, 29 November 2019, https://doi. org/10.3389/fmars.2019.00723.

[42] Aiello G New sedimentological and coastal and marine geological data on the Quaternary marine deposits of the Ischia Island (Gulf of Naples, Southern Tyrrhenian Sea, Italy). Geomarine Letters, 2020, 40, p. 593-618.

#### [43] Rendina F, Kaleb S,

Caragnano A, Ferrigno F, Appolloni L, Donnarumma L, Russo G F, Sandulli R, Roviello V, Falace A Distribution and Characterization of Deep Rhodolith Beds of the Campania Coast (SW Italy,

**299**

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New…*

*DOI: http://dx.doi.org/10.5772/intechopen.95083*

Mediterranean Sea). Plants, 2020, 9, 985; doi:10.3390/plants9080985.

[44] Jeong J B, Kim S Y, Seo Y K, Shin J, Woo K S (2020) Influence of submarine topography and associated sedimentary processes on the distribution of live and dead rhodoliths near Udo Island, Korea. Geomarine Letters, 2020, 40, p. 35-51.

*Bioclastic Deposits in the NW Gulf of Naples (Southern Tyrrhenian Sea, Italy): A Focus on New… DOI: http://dx.doi.org/10.5772/intechopen.95083*

Mediterranean Sea). Plants, 2020, 9, 985; doi:10.3390/plants9080985.

*Geochemistry*

3, (1): 53-74.

Mäerl beds (Corallinales) off the island of Ischia (Tyrrhenian Sea). UNEP-MAP-RAC/SPA Proceedings of the 1st Mediterranean Symposium on the Coralligenous and other calcareous bioconcretions of the Mediterranean Sea, Tabarka, 15-16 January 2009, CAR/ASP B, Bubb J N Seismic stratigraphy and global change of sea level. In: Payton C E, editor, Seismic stratigraphy applications to hydrocarbon

exploration, AAPG Memory, 1977; 26,

[38] Mitchum J R, Vail P R, Sangree J B (1977) Stratigraphic interpretation of seismic reflection pattern in depositional sequences. In: Payton C E, editor, Seismic stratigraphy applications to hydrocarbon

exploration, AAPG Memory, 1977; 26,

[39] Catuneanu O, Galloway W E, Kendall C G, Miall A D, Posamentier

Sequence Stratigraphy: Methodology and Nomenclature. Newsletters on Stratigraphy, 2011; 44 (3): 173-245.

[40] Basso D, Babbini L, Ramos-Espla A A, Salomidi M Mediterranean Rhodolith

Beds. In: Riosmena-Rodriguez R, Nelson W, Aguirre J, editors. Rhodolith/ Maerl Beds: A Global Perspective. Coastal Research Library, 2017; 15, p.

[41] Rindi F, Braga J C, Martin S,

J Coralline Algae in a Changing

org/10.3389/fmars.2019.00723.

[43] Rendina F, Kaleb S,

Pena V, Le Gall L, Caragnano A, Aguirre

Mediterranean Sea: How Can We Predict Their Future, if We Do Not Know Their Present? Frontiers in Marine Sciences, 29 November 2019, https://doi.

[42] Aiello G New sedimentological and coastal and marine geological data on the Quaternary marine deposits of the Ischia Island (Gulf of Naples, Southern Tyrrhenian Sea, Italy). Geomarine Letters, 2020, 40, p. 593-618.

Caragnano A, Ferrigno F, Appolloni L, Donnarumma L, Russo G F, Sandulli R, Roviello V, Falace A Distribution and Characterization of Deep Rhodolith Beds of the Campania Coast (SW Italy,

H W, Strasser A, Tucker M E

p. 49-116.

p. 117-134.

281-298.

publication, Tunisi, p. 197-200.

[32] Colantoni P, Gallignani P, Fresi E, Cinelli F: Patterns of Posidonia oceanica (L.) DELILE beds around of the Island of Ischia (Gulf of Naples) and in adjacent waters. Marine Ecology, 1982;

[33] Brandano M, Civitelli G: Non sea-grass meadow sedimentary facies on the Pontian Islands, Tyrrhenian sea: a modern example of mixed carbonatesiliciclastic sedimentation. Sedimentary

Geology, 2007; 201: 286-310.

[34] Brandano M, Tomassetti L, Mateu-Vicens G, Gagliano G: The seagrass skeletal assemblage from modern to fossil and from tropical to temperate: Insight from Maldivian and Mediterranean examples.

Sedimentology, 2019; 66 (6): 2268-2296.

[35] Aiello G: Marine geological maps of the Campania Region (Southern Tyrrhenian sea, Italy): considerations and contributions to a different scale of geological survey. Journal of Geography

[36] Ferraro L, Molisso F Sedimenti ed associazioni a foraminiferi bentonici di settori selezionati della piattaforma continentale dell'Isola d'Ischia (Tirreno meridionale). In: Gambi M C, De Lauro M, Iannuzzi F, editors, Ambiente Marino Costiero e Territorio delle Isole Flegree (Ischia Procida Vivara – Golfo di Napoli). Risultati di uno studio multidisciplinare. Memorie Accademia Scienze Fisiche e Matematiche in

[37] Vail P R, Mitchum R M, Todd R G, Widmier J M, Thompson S, Sangree J

and Cartography, 2018b; 1 (3), doi:10.24294/jgc.v1i3.507.

Napoli, 2003; 5, p. 67-82.

**298**

[44] Jeong J B, Kim S Y, Seo Y K, Shin J, Woo K S (2020) Influence of submarine topography and associated sedimentary processes on the distribution of live and dead rhodoliths near Udo Island, Korea. Geomarine Letters, 2020, 40, p. 35-51.

### *Edited by Miloš René, Gemma Aiello and Gaafar El Bahariya*

Geochemistry includes new contributions to the field of granite rocks geochemistry, mineralogy, petrology and microstructure studies, geochemistry of radioactive isotopes, and geochronology. It contains detailed geochemical, mineralogical, petrological, sedimentological and geostructural studies from Europa, Asia, Africa, South America and Australia Chapters present geochemical exploration methods, isotopic studies, and macro- and microstructural analyses.

Published in London, UK © 2021 IntechOpen © pabkov / iStock

Geochemistry

Geochemistry

*Edited by Miloš René, Gemma Aiello and Gaafar El Bahariya*