**5. Late Pleistocene climate reconstruction based on δ18O and δ13C values**

Stable isotope ratios of δ18O and δ13C were measured from fossil shells of two species: *Helicopsis striata* and *Arianta arbustorum*. Modern European land snails are active in the +10 to +27°C temperature range and hibernate or become inactive at temperatures below +10°C [36, 37]. This implies that stable isotope ratios recorded in mollusk shells represent a warmer period when snails formed their shells. This period

**21**

*Pleistocene Climate Change in Central Europe DOI: http://dx.doi.org/10.5772/intechopen.93820*

of approx. -3‰ was approx. -8‰.

that spans from spring to fall can be 160–210 days long [38, 39] and it reflects an average growing season (AGS) temperature. The same principle can be applied on fossil snails. It is known that snails are active in building their shells during and immediately after the rain [40]. This information is crucial, because it provides a direct link from rainwater δ18O values and δ18O values that we measured in the mollusk shells. This complex relationship between the δ18O value of meteoric water and the values measured in land-snail shells has been studied for more than 40 years [15–17, 24, 41]. Today it is reliable and well established method often used for paleoclimate and paleoenvironmental research. Variations in land snail shell δ18O is a function of temperature, relative humidity, δ18O of water vapor, and δ18O of liquid water ingested by the snail [16, 27]. It is worth mentioning that intra-shell variation of values measured in snail shells from LGM ranges from 0‰ to −5.5‰ [18] in some studied areas.

To avoid errors and to obtain the average δ18O and δ13C values, whole snail shells were crushed and analyzed. The δ18O value in mollusk shells is enriched on average by 5‰ relative to equilibrium with ingested rainwater [16]. This means that a δ18O value of palaeo rainwater incorporated in a mollusk shell which displays a δ18O value

In order to compare climate conditions in the Upper Pleistocene with recent climate and to obtain relative temperature changes, it is necessary to know the δ18O values of recent meteoric water and recent AGS temperatures from the same or nearby region. The nearest measured δ18O value of rainwater to Zmajevac LPS is recorded in city of Zagreb, Croatia, which is located 250 km to the west from Zmajevac LPS. This δ18O value is −6.11‰ for summer months of June, July and August (JJA) and it is measured in the last two decades [18]. This values represent shorter periods than AGS, but it is the closest approximation as we can get. In the last two decades mean JJA temperature recorded in Zagreb was +19.7°C. If we compare δ18O values from Zmajevac LPS mollusk shells, enlarged for 5‰, we can clearly see that δ18O values of meteoric water in

the Upper Pleistocene ranged from approx. -7.45‰ to approx. -10.76‰.

If we compare these approximate and indirect δ18O values with δ18O value of −6.11‰ from present JJA measurements in Zagreb, it is clear that δ18O values were constantly lower/more negative. This means that AGS temperatures during the Upper Pleistocene in Baranj region were much lower than present temperature in city of Zagreb. The mean, annual δ18O value of rainwater for Zagreb is −8.33‰ [18] and mean annual temperature (MAT) for Zagreb in last two decades is +12°C. As most of the samples from Zmajevac LPS display more negative δ18O values than −8.33‰, we can say with some certainty that even the AGS temperatures (which represent the warmest period of the year) during the Upper Pleistocene were lower than the present MAT in Zagreb. It is hard to determine what was the absolute value of temperature in the Upper Pleistocene, but we can calculate relative values and compare them to present one.

Researchers [42] estimated the MAT for MIS 2 stage is in range from 6.2°C to 11.2°C. It was reconstructed from oxygen isotopes values measured in mammoth tooth enamel from sites in the Czech Republic and Slovakia [42]. This paleotemperature data represents climate conditions from part of the Central Europe that is quite north of Zmajevac LPS (more than 200 km). Still, it can serve as a marker if we assume that the decrease in temperature is indeed related with latitude increase. Other researchers [20] estimated temperatures of 6.7 C (based on MS values), 8.5 ± 0.6 C (based on XRF-1 values) and 8.9 ± 4.4 C (based on XRF-2 values) in Northern Hungary for the same period of the Upper Pleistocene (MIS 2 stage). Finally, researchers [43] calculated a MAT of 4.5 C in Central Europe using noble gas thermometry (NGT). This result displays significantly

lower MAT than other results, which is probably due to this specific method.

Results from our research show that δ18O values from Zmajevac LPS are in fair accordance with δ18O values from North America and other LPS's in Central Europe, but they are partly different from δ18O values from southern Europe (**Figure 4**).

#### *Pleistocene Climate Change in Central Europe DOI: http://dx.doi.org/10.5772/intechopen.93820*

*Pleistocene Archaeology - Migration, Technology, and Adaptation*

of Zmajevac and Irig LPS's at the southern slopes.

The Upper Pleistocene malacofaunal assemblages from the Petrovaradin loess profile in NW Serbia show colder and more humid conditions than in either the Irig or Zmajevac LPS [3, 32]. This is probably an effect of the palaeogeographic position at the northern slope of Fruška Gora Mt. [3, 32], which is opposite to the positions

The fauna from middle and upper loess horizons (L3, L2 and L1) of the Zmajevac LPS displays certain similarity also with Madaras loess section in South Hungary [33]. There are some differences present as well. Uppermost L1 loess horizon in the Zmajevac LPS differs from K L1 LL1 loess horizon in Madaras because *Helicopsis striata* and *Chondrula tridens* assemblages dominate here, while *Columella columella* and *Vallonia tenuilabris* species dominate in Madaras LPS. Also, oposite to Madaras LPS *Columella columella* species is scarce at Zmajevac LPS. L2 loess horizon from the Zmajevac LPS differs from K L1 LL2 loess horizon at Madaras section, because *Vallonia costata* and *Pupilla muscorum* species dominate in that LPS, while in the Zmajevac LPS *Pupilla muscorum* is present, but not dominant. Also, *Vallonia costata* species is not present at all. L3 loess horizon in the Zmajevac LPS and K L1 LL3 loess horizon from Madaras LPS

Described mollusk assemblages from Zmajevac LPS show small but important

Sedimentological and magnetic susceptibility (MS) data obtained from Zmajevac LPS show similarities with other LPS's in the Pannonian Basin that were described in last decade [2, 7, 8]. MS values are in the expected range, especially in loess horizons (**Figure 3**). MS values from four paleosols are comparable with those from Irig LPS in neighboring Vojvodina region [2]. The lowermost P4 paleosol from Zmajevac LPS displays significantly weaker signals, than the P2 paleosol, but it is stronger than signals from the overlying P3b paleosol horizon. The MS value of 58.3 × 10–6 SI in the P4 paleosol is lower than expected for a long, interglacial period in which favorable climatic conditions prevailed, thus enabling fully developed soil. Even though P4 is the oldest paleosol in Zmajevac LPS, a weaker signal than in the youngest F2 paleosol may indicate that the relatively low MS values are result of mineral leaching. Such a decrease in the MS signal in clayey horizons was also detected in LPS in Germany [34] and in Hungary [35], therefore, it is not a specificity of Zmajevac LPS. It is very likely that similar processes affected the P4 paleosol horizon in Zmajevac. In agreement with previous research of this area [7], the P4 horizon is correlated with the MIS 5e interglacial period. The pedo-complex forming paleosol horizons P3a and P3b is similar to a pedo-complex from the Vojvodina [2]. Reminiscent of synchronous horizon of Hungarian Sütto LPS [4], the signal from the P3 pedo-comlex is higher than the one measured in Vojvodina. Finally, the strongly increased MS value of 82.5 × 10–6 SI suggests that the uppermost paleosol P2 could represent an interglacial, rather than an

**5. Late Pleistocene climate reconstruction based on δ18O and δ13C values**

Stable isotope ratios of δ18O and δ13C were measured from fossil shells of two species: *Helicopsis striata* and *Arianta arbustorum*. Modern European land snails are active in the +10 to +27°C temperature range and hibernate or become inactive at temperatures below +10°C [36, 37]. This implies that stable isotope ratios recorded in mollusk shells represent a warmer period when snails formed their shells. This period

both contain *Helicopsis striata* assemblage and show the greatest similarity.

differences to other Pannonian Basin LPS's. It is especially noticeable in loess horizons L7, L6 and L3 of Zmajevac LPS. Results of malacofaunal assemblages from nearby loess profiles in Serbia and Hungary suggest that climate conditions that dominated in this part of Central Europe were similar, with some differences which

were a result of paleogeography and microclimate conditions driven by it.

**20**

interstadial phase.

that spans from spring to fall can be 160–210 days long [38, 39] and it reflects an average growing season (AGS) temperature. The same principle can be applied on fossil snails. It is known that snails are active in building their shells during and immediately after the rain [40]. This information is crucial, because it provides a direct link from rainwater δ18O values and δ18O values that we measured in the mollusk shells. This complex relationship between the δ18O value of meteoric water and the values measured in land-snail shells has been studied for more than 40 years [15–17, 24, 41]. Today it is reliable and well established method often used for paleoclimate and paleoenvironmental research. Variations in land snail shell δ18O is a function of temperature, relative humidity, δ18O of water vapor, and δ18O of liquid water ingested by the snail [16, 27]. It is worth mentioning that intra-shell variation of values measured in snail shells from LGM ranges from 0‰ to −5.5‰ [18] in some studied areas.

To avoid errors and to obtain the average δ18O and δ13C values, whole snail shells were crushed and analyzed. The δ18O value in mollusk shells is enriched on average by 5‰ relative to equilibrium with ingested rainwater [16]. This means that a δ18O value of palaeo rainwater incorporated in a mollusk shell which displays a δ18O value of approx. -3‰ was approx. -8‰.

In order to compare climate conditions in the Upper Pleistocene with recent climate and to obtain relative temperature changes, it is necessary to know the δ18O values of recent meteoric water and recent AGS temperatures from the same or nearby region. The nearest measured δ18O value of rainwater to Zmajevac LPS is recorded in city of Zagreb, Croatia, which is located 250 km to the west from Zmajevac LPS. This δ18O value is −6.11‰ for summer months of June, July and August (JJA) and it is measured in the last two decades [18]. This values represent shorter periods than AGS, but it is the closest approximation as we can get. In the last two decades mean JJA temperature recorded in Zagreb was +19.7°C. If we compare δ18O values from Zmajevac LPS mollusk shells, enlarged for 5‰, we can clearly see that δ18O values of meteoric water in the Upper Pleistocene ranged from approx. -7.45‰ to approx. -10.76‰.

If we compare these approximate and indirect δ18O values with δ18O value of −6.11‰ from present JJA measurements in Zagreb, it is clear that δ18O values were constantly lower/more negative. This means that AGS temperatures during the Upper Pleistocene in Baranj region were much lower than present temperature in city of Zagreb. The mean, annual δ18O value of rainwater for Zagreb is −8.33‰ [18] and mean annual temperature (MAT) for Zagreb in last two decades is +12°C. As most of the samples from Zmajevac LPS display more negative δ18O values than −8.33‰, we can say with some certainty that even the AGS temperatures (which represent the warmest period of the year) during the Upper Pleistocene were lower than the present MAT in Zagreb. It is hard to determine what was the absolute value of temperature in the Upper Pleistocene, but we can calculate relative values and compare them to present one.

Researchers [42] estimated the MAT for MIS 2 stage is in range from 6.2°C to 11.2°C. It was reconstructed from oxygen isotopes values measured in mammoth tooth enamel from sites in the Czech Republic and Slovakia [42]. This paleotemperature data represents climate conditions from part of the Central Europe that is quite north of Zmajevac LPS (more than 200 km). Still, it can serve as a marker if we assume that the decrease in temperature is indeed related with latitude increase. Other researchers [20] estimated temperatures of 6.7 C (based on MS values), 8.5 ± 0.6 C (based on XRF-1 values) and 8.9 ± 4.4 C (based on XRF-2 values) in Northern Hungary for the same period of the Upper Pleistocene (MIS 2 stage). Finally, researchers [43] calculated a MAT of 4.5 C in Central Europe using noble gas thermometry (NGT). This result displays significantly lower MAT than other results, which is probably due to this specific method.

Results from our research show that δ18O values from Zmajevac LPS are in fair accordance with δ18O values from North America and other LPS's in Central Europe, but they are partly different from δ18O values from southern Europe (**Figure 4**).

δ18O values measured in fossil shells indirectly reflect paleotemperature at a time when these fossil snails lived. This is useful if we want to reconstruct paleotemperature changes over longer period of time if we have enough data, that is, fossil findings. We know from previous research that if the δ18O value in the shell changes by 0.5‰ it reflects a paleotemperature change of approximately 2°C [24]. The formula for calculating AGS paleotemperature changes in the Zmajevac LPS, adjusted according to [24], is as proposed:

$$\mathbf{^0\Omega(^\circ C)} = \left(\\$\mathbf{i}\\$\mathbf{O}\mathbf{max}.-\\$\mathbf{i}\\$\mathbf{8}\mathbf{O}\mathbf{min}./\mathbf{o},\mathbf{j}\\$\mathbf{6}\mathbf{o}\right)\mathbf{X}\ 2^\circ \mathbf{C}\tag{1}$$

where:

Ω is: relative paleotemperature change

δ18 Omax. is: maximal δ18O value measured in a gastropod shell

δ18 Omin. is: minimal δ18O value measured in a gastropod shell

We used the δ18O values measured from Zmajevac LPS fossil shells and according to this formula AGS paleotemperature changes through entire Upper Pleistocene in Baranja region is: 13.2°C.

Other researchers propose different ratios and interdependence of δ18O values and paleotemperature. According to [26] if the δ18O value in shell changes by 0.35‰ it reflects a paleotemperature change of approximately 1°C. We can adjust the formula according to this research and then it is:

Ω(° =δ δ C 18Omax. – 18Omin. /0,35‰ X 1 C ) ( ) ° (2)

where:

Ω is: relative paleotemperature change

δ18 Omax. is: maximal δ18O value measured in a gastropod shell

δ18 Omin. is: minimal δ18O value measured in a gastropod shell

If we use the same δ18O values from Zmajevac LPS fossil shells in this formula, AGS paleotemperature changes through the Upper Pleistocene in Baranaj region is: 9.5°C.

If we compare these results with MAT temperatures for other Pannonian Basin LPS, it is plausible to conclude that the second formula and the range of 9.5°C are more accurate. Both of these values suggest strong and constant changes of paleotemperature during the Upper Pleistocene in the Baranja region.

It is worth mentioning that he δ18O values from Zmajevac LPS displays some deviation in regards to paleotemperatures or paleoclimate conditions determined by malacofaunal assemblages. These deviations are probably a result of complex fluxbalance model between the rainwater used by the fossil snails and their shell, which does not respond with the same intensity to palaeo temperature changes [27].

Climate changes during the glacial and interglacial periods are the main cause for changes in vegetation which are reflected in δ13C values of plants [44, 45]. Therefore, δ13C values from fossil shells can be used to determine the diet of land snails, which can then help in palaeoenvironmental reconstruction. The δ13C value of atmospheric CO does not affect the δ13C value of snail shells, so these values are a relevant and reliable indicator of fossil snail diet [27]. If the δ13C values are more negative, it is an indication that the mollusks consumed more C3 plants in their diet and that the climate was cooler and more humid [22, 25]. If the δ13C values are more positive, it is an indication that the snails consumed more C4 plants in their diet, which indicates a more arid environment [22, 46].

Research from central parts of Pannonian Basin (Hungary) [47] shows that relatively stable woodland-grassland ecotone was the dominant vegetation type in the Pannonian Basin between 140 ky and 16 ky. This is a time span which largely coincides with Upper Pleistocene period. Described woodland-grassland ecotone

**23**

**Figure 4.**

*LPS profiles from late Pleistocene.*

*Pleistocene Climate Change in Central Europe DOI: http://dx.doi.org/10.5772/intechopen.93820*

was preserved even during the strongest cooling, when a treeless steppe dominated the landscape of Pannonian Basin [47]. In this mixture of temperate, arctic and alpine ecosystems C3 plants typically dominate [48]. Soils formed in Tokaj region (southern Hungary) at the southern edge of the Pannonian Basin, display δ13C values in really narrow range from −24‰ to −25‰ [48]. This is typical for soils

*Comparison of results for MIS2 from Zmajevac LPS with ones recorded in other European and north American* 

The variation of δ13C values measured in fossil shells from Zmajevac LPS loess samples ranges from −8.83‰ to −6.84‰. Therefore, C4 vegetation as a diet source for these fossil snails obtained from Zmajevac LPS can be excluded. C4 plants display very different δ13C values, ranging from −8‰ to −16‰ [49] and this is contrary to our results from Baranja region. δ13C values measured in any fossil mollusk shells are enriched by 8–19‰ compared to the values of the plants that they ingested [50]. This means that δ13C values of plants that mollusk from Zmajevac LPS ingested, were approximately in the range from −14.84‰ to −16.83‰, if we use the minimal 8‰ enrichment approach. This is very close to the most negative margin for C4 plants. If we apply maximal 19‰ enrichment, these values are more negative and in range from −25.84‰ to −27.83‰. Results from nearby areas [2, 4, 47, 48] that were compared with the results from this study suggests that for the entire time span during which the Zmajevac LPS was accumulated, C3 plants have been the main vegetation type for analyzed fossil snails. This indicates that Upper Pleistocene climate in the Baranja region was similar to the paleoclimate in other regions in the Pannonian Basin. Certain differences in paleoclimate exist and they are probably an effect of local geomorphology and microclimate conditions.

**6. Impact of paleoclimate changes on Neanderthals and anatomically** 

The Balkan peninsula was likely the migration route of anatomically modern humans (AMH) into Europe [51], and the Danube valley which cuts the Pannonian Basin is one of the most important pathways of these population movements [52]. This region consists of vast lowlands associated with the middle Danube drainage basin and surrounded by the Carpathian Mountains, the Alps, Dinarides and the

**modern humans (AMH) in Central Europe**

developed under plants using the C3 photosynthetic pathway [49].

*Pleistocene Climate Change in Central Europe DOI: http://dx.doi.org/10.5772/intechopen.93820*

#### **Figure 4.**

*Pleistocene Archaeology - Migration, Technology, and Adaptation*

adjusted according to [24], is as proposed:

Ω is: relative paleotemperature change

the formula according to this research and then it is:

Ω is: relative paleotemperature change

which indicates a more arid environment [22, 46].

where:

where:

in Baranja region is: 13.2°C.

δ18O values measured in fossil shells indirectly reflect paleotemperature at a time when these fossil snails lived. This is useful if we want to reconstruct paleotemperature changes over longer period of time if we have enough data, that is, fossil findings. We know from previous research that if the δ18O value in the shell changes by 0.5‰ it reflects a paleotemperature change of approximately 2°C [24]. The formula for calculating AGS paleotemperature changes in the Zmajevac LPS,

δ18 Omax. is: maximal δ18O value measured in a gastropod shell δ18 Omin. is: minimal δ18O value measured in a gastropod shell

δ18 Omax. is: maximal δ18O value measured in a gastropod shell δ18 Omin. is: minimal δ18O value measured in a gastropod shell

temperature during the Upper Pleistocene in the Baranja region.

We used the δ18O values measured from Zmajevac LPS fossil shells and according to this formula AGS paleotemperature changes through entire Upper Pleistocene

Other researchers propose different ratios and interdependence of δ18O values

If we use the same δ18O values from Zmajevac LPS fossil shells in this formula, AGS paleotemperature changes through the Upper Pleistocene in Baranaj region is: 9.5°C. If we compare these results with MAT temperatures for other Pannonian Basin LPS, it is plausible to conclude that the second formula and the range of 9.5°C are more accurate. Both of these values suggest strong and constant changes of paleo-

It is worth mentioning that he δ18O values from Zmajevac LPS displays some deviation in regards to paleotemperatures or paleoclimate conditions determined by malacofaunal assemblages. These deviations are probably a result of complex fluxbalance model between the rainwater used by the fossil snails and their shell, which does not respond with the same intensity to palaeo temperature changes [27]. Climate changes during the glacial and interglacial periods are the main cause for changes in vegetation which are reflected in δ13C values of plants [44, 45]. Therefore, δ13C values from fossil shells can be used to determine the diet of land snails, which can then help in palaeoenvironmental reconstruction. The δ13C value of atmospheric CO does not affect the δ13C value of snail shells, so these values are a relevant and reliable indicator of fossil snail diet [27]. If the δ13C values are more negative, it is an indication that the mollusks consumed more C3 plants in their diet and that the climate was cooler and more humid [22, 25]. If the δ13C values are more positive, it is an indication that the snails consumed more C4 plants in their diet,

Research from central parts of Pannonian Basin (Hungary) [47] shows that relatively stable woodland-grassland ecotone was the dominant vegetation type in the Pannonian Basin between 140 ky and 16 ky. This is a time span which largely coincides with Upper Pleistocene period. Described woodland-grassland ecotone

and paleotemperature. According to [26] if the δ18O value in shell changes by 0.35‰ it reflects a paleotemperature change of approximately 1°C. We can adjust

Ω(° ° C 18Omax. – 18Omin. /0,5‰ X 2 C ) =δ δ ( ) (1)

Ω(° =δ δ C 18Omax. – 18Omin. /0,35‰ X 1 C ) ( ) ° (2)

**22**

*Comparison of results for MIS2 from Zmajevac LPS with ones recorded in other European and north American LPS profiles from late Pleistocene.*

was preserved even during the strongest cooling, when a treeless steppe dominated the landscape of Pannonian Basin [47]. In this mixture of temperate, arctic and alpine ecosystems C3 plants typically dominate [48]. Soils formed in Tokaj region (southern Hungary) at the southern edge of the Pannonian Basin, display δ13C values in really narrow range from −24‰ to −25‰ [48]. This is typical for soils developed under plants using the C3 photosynthetic pathway [49].

The variation of δ13C values measured in fossil shells from Zmajevac LPS loess samples ranges from −8.83‰ to −6.84‰. Therefore, C4 vegetation as a diet source for these fossil snails obtained from Zmajevac LPS can be excluded. C4 plants display very different δ13C values, ranging from −8‰ to −16‰ [49] and this is contrary to our results from Baranja region. δ13C values measured in any fossil mollusk shells are enriched by 8–19‰ compared to the values of the plants that they ingested [50]. This means that δ13C values of plants that mollusk from Zmajevac LPS ingested, were approximately in the range from −14.84‰ to −16.83‰, if we use the minimal 8‰ enrichment approach. This is very close to the most negative margin for C4 plants. If we apply maximal 19‰ enrichment, these values are more negative and in range from −25.84‰ to −27.83‰. Results from nearby areas [2, 4, 47, 48] that were compared with the results from this study suggests that for the entire time span during which the Zmajevac LPS was accumulated, C3 plants have been the main vegetation type for analyzed fossil snails. This indicates that Upper Pleistocene climate in the Baranja region was similar to the paleoclimate in other regions in the Pannonian Basin. Certain differences in paleoclimate exist and they are probably an effect of local geomorphology and microclimate conditions.
