**4. Examples of strike-slip basins**

The wide variability of strike-slip faults makes it difficult to develop a simple model of the formation of strike-slip basins and their sedimentary facies. Although the geometries of such basins depend on the amount of fault displacement, the angle and distance between overstep‐ ped faults, and the depth of detachment of the faults, the basins are generally elongate, narrow, and deep. Several representative examples of the strike-slip basins described in this section show a range of basin evolutionary paths and filling processes.

**Figure 7.** Typical geometry of termination areas of strike-slip faults. (A) If the block collides with a rigid continental crust, it shortens and is uplifted, accompanied by thrusts. At the opposite side to the uplift, upper crust is mechanically pulled away, leading to subsidence. (B) If the block extrudes with a rotational component into a weak oceanic crust (a transtensional setting), a sedimentary basin forms at the end of the strike-slip fault. Examples include the Yinggehai Basin, which is related to the extrusion of the Indochina Block, and the Gulf of California, which is related to the trans‐ tensional movement of the Baja California Peninsula. (C) The strike-slip fault diffuses its displacement through splayed extensional normal faults at its end [44]. An example is the Cerdanya clastic basin formed by late Miocene normal faulting at the termination of the La Tet strike-slip fault, Spain [51].

#### **4.1. Fault-bend basin: The Ridge Basin**

#### *4.1.1. Geology*

The Ridge Basin, which is one of the best-studied examples of a strike-slip basin [37, 55], is situated along the San Andreas Fault, a right-lateral plate-boundary transform fault between the Pacific and the North American plates, and along the San Gabriel Fault, a major strand of the San Andreas Fault (Figure 4B).

The San Gabriel Fault is a listric, ESE-dipping, oblique-slip fault rather than a subvertical, strike-slip fault [56]. The Ridge Basin is a type of fault-bend basin developed in front of a releasing bend on the San Gabriel Fault, along which the upper crust stretched and subsided to form a space in which sediments could be accommodated. The bottom of the basin is bounded by the subhorizontal San Gabriel Fault at a depth of ∼4 km.

The basin originated in the late Miocene as a narrow depression within the broad San Andreas transform belt in southern California. The basin has a length of 45 km and a width of 15 km; the length/width ratio of 3 is a typical value for pull-apart basins [2]. The strata are exposed as a northwest-dipping homoclinal sequence that becomes younger to the northwest. The exposed sediment thickness reaches ∼14 km, somewhat larger than the basin depth (∼4 km) [56].

*4.1.2. Basin filling processes*

depocenters [61]

The strata within the Ridge Basin are assigned to the Ridge Basin Group, which includes five formations: Castaic, Peace Valley, Violin Breccia, Ridge Route, and Hungry Valley (Figure 8A). Sedimentation began in the late Miocene (ca. 11 Ma) with deposition of the marine Castaic

**Figure 8.** (A) Simplified geological map showing formations in the Ridge Basin [58]. (B) Conceptual basin-filling proc‐ ess for the Ridge Basin [8]. Abbreviations: FMT, Frazier Mountain Thrusts; BMF, Bear Mountain Fault; CF, Canton Fault. (C) Cross-sectional profiles showing continuous axial sediment supply and migration of sediments with relatively fixed

Strike-Slip Basin – Its Configuration and Sedimentary Facies

http://dx.doi.org/10.5772/56593

37

**Figure 8.** (A) Simplified geological map showing formations in the Ridge Basin [58]. (B) Conceptual basin-filling proc‐ ess for the Ridge Basin [8]. Abbreviations: FMT, Frazier Mountain Thrusts; BMF, Bear Mountain Fault; CF, Canton Fault. (C) Cross-sectional profiles showing continuous axial sediment supply and migration of sediments with relatively fixed depocenters [61]

#### *4.1.2. Basin filling processes*

**4.1. Fault-bend basin: The Ridge Basin**

faulting at the termination of the La Tet strike-slip fault, Spain [51].

the San Andreas Fault (Figure 4B).

basin depth (∼4 km) [56].

The Ridge Basin, which is one of the best-studied examples of a strike-slip basin [37, 55], is situated along the San Andreas Fault, a right-lateral plate-boundary transform fault between the Pacific and the North American plates, and along the San Gabriel Fault, a major strand of

**Figure 7.** Typical geometry of termination areas of strike-slip faults. (A) If the block collides with a rigid continental crust, it shortens and is uplifted, accompanied by thrusts. At the opposite side to the uplift, upper crust is mechanically pulled away, leading to subsidence. (B) If the block extrudes with a rotational component into a weak oceanic crust (a transtensional setting), a sedimentary basin forms at the end of the strike-slip fault. Examples include the Yinggehai Basin, which is related to the extrusion of the Indochina Block, and the Gulf of California, which is related to the trans‐ tensional movement of the Baja California Peninsula. (C) The strike-slip fault diffuses its displacement through splayed extensional normal faults at its end [44]. An example is the Cerdanya clastic basin formed by late Miocene normal

36 Mechanism of Sedimentary Basin Formation - Multidisciplinary Approach on Active Plate Margins

The San Gabriel Fault is a listric, ESE-dipping, oblique-slip fault rather than a subvertical, strike-slip fault [56]. The Ridge Basin is a type of fault-bend basin developed in front of a releasing bend on the San Gabriel Fault, along which the upper crust stretched and subsided to form a space in which sediments could be accommodated. The bottom of the basin is

The basin originated in the late Miocene as a narrow depression within the broad San Andreas transform belt in southern California. The basin has a length of 45 km and a width of 15 km; the length/width ratio of 3 is a typical value for pull-apart basins [2]. The strata are exposed as a northwest-dipping homoclinal sequence that becomes younger to the northwest. The exposed sediment thickness reaches ∼14 km, somewhat larger than the

bounded by the subhorizontal San Gabriel Fault at a depth of ∼4 km.

*4.1.1. Geology*

The strata within the Ridge Basin are assigned to the Ridge Basin Group, which includes five formations: Castaic, Peace Valley, Violin Breccia, Ridge Route, and Hungry Valley (Figure 8A). Sedimentation began in the late Miocene (ca. 11 Ma) with deposition of the marine Castaic Formation. The younger Castaic Formation is interfingered with the older Violin Breccia, which consists of conglomerates adjacent to the San Gabriel Fault scarp [57].

slip basin in the system, and is partly overlain by a deep hypersaline lake located at Earth's

Strike-Slip Basin – Its Configuration and Sedimentary Facies

http://dx.doi.org/10.5772/56593

39

The Dead Sea Basin is 132 km long and 7–18 km wide, yielding a high length/width ratio (> 7). The basin is segmented into sequential sub-basins by deep transverse normal faults rather than by listric faults. The length of the basin is greater than the total offset length (∼105 km) of the

The basin has a cross-sectional asymmetry, with a steep eastern slope and a gentle western slope. Seismic refraction and gravity data indicate that the southern Dead Sea Basin is unusually deep, containing about 14 km of sedimentary fill [66]. Geophysical data suggest that the deep basin is probably bordered on all sides by vertical faults that cut deep into the basement [67]. The thick sediment accumulation yields a large negative Bouguer gravity anomaly (lower than –100 mGal) [64]. Given the depth of the basin, ductile deformation in the lower crust would be expected; however, the present-day heat flow in the Dead Sea Basin is low (∼40 mW m-2) [68], suggesting that the lower crust may still be cool and brittle, and that the Moho is not elevated beneath the basin. These inferences are consistent with seismic activity

The Dead Sea Basin has traditionally been considered a classic example of a stepover basin [2], but other interpretations have been proposed, including propagating basins [67], stretching basins [64], and sequential basins [63]. The sequential basin model, in which several active subbasins are delimited by boundary master faults and transverse faults, and simultaneously

**Figure 9.** The Dead Sea Basin developed in a transtensional domain of the Dead Sea Fault system. On the northern side of the basin, the Lebanon and Anti-Lebanon ranges were uplifted in a transpressional domain. The locations of faults are taken from [12]. Abbreviations: AmF, Amaziyahu Fault; ArF, Arava Fault; WIF, Western Intrabasinal Fault; EBF, Eastern Boundary Fault; WBF, Western Boundary Fault; MS, Mount Sedom; LD, Lisan Peninsula; LR, Lebanon Range; ALR, Anti-Lebanon Range; JR, Jordan River; SG, Sea of Galilee [69]; HV, Hula Valley [70]. Plate names: AR, Arabi‐

lowest continental elevation (418 m below sea level at the lake surface) [43, 62–64].

fault system, which is atypical of pull-apart basins [65].

at depths of 20–32 km.

an; NU, Nubian (African).

The main part of the Ridge Basin Group consists of the Peace Valley and Ridge Route forma‐ tions. The Peace Valley Formation consists mainly of sandstone and mudstone of lacustrine, fluvial, deltaic, and alluvial facies, accompanied by minor carbonaceous deposits. The Ridge Route Formation, which crops out in the northeastern part of the Basin, is composed of alluvial sandstone and conglomerate, and is interfingered with the Peace Valley Formation. Both the Peace Valley and Ridge Route formations are interfingered southwestward into the Violin Breccia. The uppermost unit of the Ridge Basin, the Hungry Valley Formation, conformably overlies the Peace Valley and Ridge Route formations. The deposition of this formation, including alluvial conglomerate, sandstone, and mudstone, ended at ca. 4 Ma.

The Ridge Basin Group presents a 14-km-thick stratigraphic section of gently (20–25°) northwest-dipping beds; it shows the dominance of axial sediment supply and migration of the deposits by dextral movement of the San Gabriel Fault (Figure 8B). The releasing bend may have a paired restraining bend on the northwestern side of the fault. Within the restraining bend, highlands were formed, which in turn provided sediment to be transported into the basin. Most of the sediment filling the basin was carried by rivers draining source areas located to the northeast. The sediments forming the Ridge Basin Group were deposited at a rate of about 2 m kyr-1.

The right-lateral displacement of the San Gabriel Fault carried the basin, together with the sediments, southeastward, resulting in a northwestward migration of the depocenter and successively younger beds onlapping onto the basin floor (Figure 8C) [58, 59]. Nearly constant values of vitrinite reflectance data (Ro = 0.5 ) throughout the group [60] support the continuous removal of sedimentary strata deposited in a relatively fixed depocenter and transported to the southeast along the San Gabriel Fault. More than 45 km of lateral displacement is estimated, based on the distribution of the Violin Breccia. This displacement, and basin migration, ended in the early Pliocene.

## **4.2. Stepover basin: The Dead Sea Basin**

## *4.2.1. Geology*

The Dead Sea Fault system is located along a plate-boundary transform zone that separates the Arabian Plate from the African Plate (Figures 4C and 9) [12]. Movement along the Dead Sea Fault commenced in the Miocene in response to the opening of the Red Sea. The very low rate of relative plate motion between Arabia and Africa (6–8 mm yr-1) has yielded only 30 km of displacement during the past 5 Myr, and about 105 km of total offset during the past 18 Myr.

The Dead Sea Fault system includes both transpressional and transtensional domains (Figure 9). Several strike-slip basins are developed along the steps of segmented faults in the trans‐ tensional domain, while the Lebanon and Anti-Lebanon ranges have been uplifted in the transpressional domain related to the restraining bend. The Dead Sea Basin is the largest strikeslip basin in the system, and is partly overlain by a deep hypersaline lake located at Earth's lowest continental elevation (418 m below sea level at the lake surface) [43, 62–64].

Formation. The younger Castaic Formation is interfingered with the older Violin Breccia,

The main part of the Ridge Basin Group consists of the Peace Valley and Ridge Route forma‐ tions. The Peace Valley Formation consists mainly of sandstone and mudstone of lacustrine, fluvial, deltaic, and alluvial facies, accompanied by minor carbonaceous deposits. The Ridge Route Formation, which crops out in the northeastern part of the Basin, is composed of alluvial sandstone and conglomerate, and is interfingered with the Peace Valley Formation. Both the Peace Valley and Ridge Route formations are interfingered southwestward into the Violin Breccia. The uppermost unit of the Ridge Basin, the Hungry Valley Formation, conformably overlies the Peace Valley and Ridge Route formations. The deposition of this formation,

The Ridge Basin Group presents a 14-km-thick stratigraphic section of gently (20–25°) northwest-dipping beds; it shows the dominance of axial sediment supply and migration of the deposits by dextral movement of the San Gabriel Fault (Figure 8B). The releasing bend may have a paired restraining bend on the northwestern side of the fault. Within the restraining bend, highlands were formed, which in turn provided sediment to be transported into the basin. Most of the sediment filling the basin was carried by rivers draining source areas located to the northeast. The sediments forming the Ridge Basin Group were deposited at a rate of

The right-lateral displacement of the San Gabriel Fault carried the basin, together with the sediments, southeastward, resulting in a northwestward migration of the depocenter and successively younger beds onlapping onto the basin floor (Figure 8C) [58, 59]. Nearly constant values of vitrinite reflectance data (Ro = 0.5 ) throughout the group [60] support the continuous removal of sedimentary strata deposited in a relatively fixed depocenter and transported to the southeast along the San Gabriel Fault. More than 45 km of lateral displacement is estimated, based on the distribution of the Violin Breccia. This displacement, and basin migration, ended

The Dead Sea Fault system is located along a plate-boundary transform zone that separates the Arabian Plate from the African Plate (Figures 4C and 9) [12]. Movement along the Dead Sea Fault commenced in the Miocene in response to the opening of the Red Sea. The very low rate of relative plate motion between Arabia and Africa (6–8 mm yr-1) has yielded only 30 km of displacement during the past 5 Myr, and about 105 km of total offset during the past 18 Myr.

The Dead Sea Fault system includes both transpressional and transtensional domains (Figure 9). Several strike-slip basins are developed along the steps of segmented faults in the trans‐ tensional domain, while the Lebanon and Anti-Lebanon ranges have been uplifted in the transpressional domain related to the restraining bend. The Dead Sea Basin is the largest strike-

which consists of conglomerates adjacent to the San Gabriel Fault scarp [57].

38 Mechanism of Sedimentary Basin Formation - Multidisciplinary Approach on Active Plate Margins

including alluvial conglomerate, sandstone, and mudstone, ended at ca. 4 Ma.

about 2 m kyr-1.

in the early Pliocene.

*4.2.1. Geology*

**4.2. Stepover basin: The Dead Sea Basin**

The Dead Sea Basin is 132 km long and 7–18 km wide, yielding a high length/width ratio (> 7). The basin is segmented into sequential sub-basins by deep transverse normal faults rather than by listric faults. The length of the basin is greater than the total offset length (∼105 km) of the fault system, which is atypical of pull-apart basins [65].

The basin has a cross-sectional asymmetry, with a steep eastern slope and a gentle western slope. Seismic refraction and gravity data indicate that the southern Dead Sea Basin is unusually deep, containing about 14 km of sedimentary fill [66]. Geophysical data suggest that the deep basin is probably bordered on all sides by vertical faults that cut deep into the basement [67]. The thick sediment accumulation yields a large negative Bouguer gravity anomaly (lower than –100 mGal) [64]. Given the depth of the basin, ductile deformation in the lower crust would be expected; however, the present-day heat flow in the Dead Sea Basin is low (∼40 mW m-2) [68], suggesting that the lower crust may still be cool and brittle, and that the Moho is not elevated beneath the basin. These inferences are consistent with seismic activity at depths of 20–32 km.

The Dead Sea Basin has traditionally been considered a classic example of a stepover basin [2], but other interpretations have been proposed, including propagating basins [67], stretching basins [64], and sequential basins [63]. The sequential basin model, in which several active subbasins are delimited by boundary master faults and transverse faults, and simultaneously

**Figure 9.** The Dead Sea Basin developed in a transtensional domain of the Dead Sea Fault system. On the northern side of the basin, the Lebanon and Anti-Lebanon ranges were uplifted in a transpressional domain. The locations of faults are taken from [12]. Abbreviations: AmF, Amaziyahu Fault; ArF, Arava Fault; WIF, Western Intrabasinal Fault; EBF, Eastern Boundary Fault; WBF, Western Boundary Fault; MS, Mount Sedom; LD, Lisan Peninsula; LR, Lebanon Range; ALR, Anti-Lebanon Range; JR, Jordan River; SG, Sea of Galilee [69]; HV, Hula Valley [70]. Plate names: AR, Arabi‐ an; NU, Nubian (African).

become larger and deeper as the master faults propagate, could explain why the Dead Sea Basin is longer than the total amount of slip along the Dead Sea Fault.

The RRFZ was a sinistral strike-slip fault in the first stage of its evolution (34–17 Ma), associated with ductile deformation [76] and the creation of an unconformity in the Gulf of Tonkin (the offshore part of the Hanoi depression [77]). After a quiescent stage from 17 to 5 Ma, due to a slowdown in the clockwise rotation of the Indochina Block [78], the movement along the RRFZ became dextral [45, 79, 80]. The right-lateral shearing is indicated by geomorphic fault traces and large river offsets [81–83], as well as GPS observations [80]. This change from a sinistral to a dextral sense of movement supports the basic tenets of the two-phase extrusion model; namely, the early, collision-driven escape of Indochina towards the SE, and the subsequent

Strike-Slip Basin – Its Configuration and Sedimentary Facies

http://dx.doi.org/10.5772/56593

41

change to accommodate the present-day escape of Tibet and South China [78, 84, 85].

The Yinggehai Basin, situated in the offshore extension of the RRFZ, is 500 km long and 50–60 km wide (*l*/*w* ≈ 10); it is oriented SE–NW and is located offshore between Hainan Island to the east and the Indosinian Peninsula to the west [73]. The basin formed originally as a sinistral strike-slip basin [77, 86], but developed into a dextral strike-slip basin after the change in the sense of fault displacement of the RRFZ [87, 88]. The basin subsided by simple shear on lowangle, detached normal faults of the upper crust and by pure shear of the lower crust [45, 87].

**Figure 10.** Geological setting of the Red River Fault zone (RRFZ) and the Yinggehai Basin. The RRFZ was originally a left-lateral strike-slip fault caused by the southeastern extrusion of the Indochina Block. The sense of displacement changed to right-lateral in response to the southeastward extrusion of the South China Block. Abbreviations: SMF, Song Ma Fault; HD, Hanoi Depression; GT, Gulf of Tonkin; YB, Yinggehai Basin; MB, Malay Basin; PB, Pattani Basin. The

thick blue line marks the cross-sectional profile displayed in Figure 11. Modified from [80, 89, 90].

#### *4.2.2. Basin-filling processes*

The depositional environments of the Dead Sea Basin are affected by the arid climatic condi‐ tions, with the area having an average annual rainfall of 50–75 mm. The modern sediments are transported to the basin mainly from the north by the Jordan River and from other directions by marginal tributaries. The mean annual discharges from the north, east, west, and south are 1100, 203, 4–5, and 4 mm, respectively [71].

In the middle to late Miocene, fluvial clastics of the Hazeva Formation were deposited in the southern sector of the basin (Figure 9). The formation consists of fluvial sandstones and conglomerates, including pre-Cretaceous components, transported from distant sources south and southeast of the Dead Sea Basin [43, 64]. During the Pliocene, the evaporitic Sedom Formation accumulated in estuarine–lagoonal environments in the Dead Sea basin; the formation consists mostly of lacustrine salts, gypsum, and carbonates interbedded with some clastics, and is found in the central sector of the basin. The 2–3 km thickness of this evaporitic formation may have formed in < 1 Myr; therefore, the sedimentation rate was probably higher than 2 m kyr-1.

In the Pleistocene and Holocene, fluvial and lacustrine deposits, alternating with evaporites and locally sourced clastics, accumulated in lakes that post-date the formation of the Sedom lagoon. The Amora, Lisan, and younger formations consist of laminated evaporitic (gypsum) and aragonite sediments that continue to accumulate in the modern Dead Sea in the northern sector of the basin. The average sedimentation rate in this stage reached 1–1.5 m kyr-1 [64]. On the whole, the depocenters have migrated northward since the Miocene.

The margins of the Dead Sea are dominated by alluvial fans. The modern basin margin environments consist of (1) talus slopes, (2) incised and confined stream channels, and (3) coarse-grained and relatively high-gradient alluvial fans. In contrast, sediments in the offshore environment are composed of thick sequences of evaporitic salt intercalated with thin beds of laminated aragonite and detrital silt [72].

#### **4.3. Fault-termination basin: The Yinggehai Basin**

#### *4.3.1. Geology*

The Yinggehai Basin (Song Hong Basin) is an example of a fault-termination basin, and is situated at the southeastern end of the Red River Fault zone (RRFZ) [73, 74]. The RRFZ, extending for some 1000 km, separates the South China Block to the north from the Indochina Block to the south (Figure 10), and is considered to be related to the continental collision between the Indian and Eurasian plates [e.g., 75]. The formation of the Yinggehai Basin was controlled by the successive clockwise extrusions of the Indochina Block and the South China Block.

The RRFZ was a sinistral strike-slip fault in the first stage of its evolution (34–17 Ma), associated with ductile deformation [76] and the creation of an unconformity in the Gulf of Tonkin (the offshore part of the Hanoi depression [77]). After a quiescent stage from 17 to 5 Ma, due to a slowdown in the clockwise rotation of the Indochina Block [78], the movement along the RRFZ became dextral [45, 79, 80]. The right-lateral shearing is indicated by geomorphic fault traces and large river offsets [81–83], as well as GPS observations [80]. This change from a sinistral to a dextral sense of movement supports the basic tenets of the two-phase extrusion model; namely, the early, collision-driven escape of Indochina towards the SE, and the subsequent change to accommodate the present-day escape of Tibet and South China [78, 84, 85].

become larger and deeper as the master faults propagate, could explain why the Dead Sea

The depositional environments of the Dead Sea Basin are affected by the arid climatic condi‐ tions, with the area having an average annual rainfall of 50–75 mm. The modern sediments are transported to the basin mainly from the north by the Jordan River and from other directions by marginal tributaries. The mean annual discharges from the north, east, west, and

In the middle to late Miocene, fluvial clastics of the Hazeva Formation were deposited in the southern sector of the basin (Figure 9). The formation consists of fluvial sandstones and conglomerates, including pre-Cretaceous components, transported from distant sources south and southeast of the Dead Sea Basin [43, 64]. During the Pliocene, the evaporitic Sedom Formation accumulated in estuarine–lagoonal environments in the Dead Sea basin; the formation consists mostly of lacustrine salts, gypsum, and carbonates interbedded with some clastics, and is found in the central sector of the basin. The 2–3 km thickness of this evaporitic formation may have formed in < 1 Myr; therefore, the sedimentation rate was probably higher

In the Pleistocene and Holocene, fluvial and lacustrine deposits, alternating with evaporites and locally sourced clastics, accumulated in lakes that post-date the formation of the Sedom lagoon. The Amora, Lisan, and younger formations consist of laminated evaporitic (gypsum) and aragonite sediments that continue to accumulate in the modern Dead Sea in the northern sector of the basin. The average sedimentation rate in this stage reached 1–1.5 m kyr-1 [64]. On

The margins of the Dead Sea are dominated by alluvial fans. The modern basin margin environments consist of (1) talus slopes, (2) incised and confined stream channels, and (3) coarse-grained and relatively high-gradient alluvial fans. In contrast, sediments in the offshore environment are composed of thick sequences of evaporitic salt intercalated with thin beds of

The Yinggehai Basin (Song Hong Basin) is an example of a fault-termination basin, and is situated at the southeastern end of the Red River Fault zone (RRFZ) [73, 74]. The RRFZ, extending for some 1000 km, separates the South China Block to the north from the Indochina Block to the south (Figure 10), and is considered to be related to the continental collision between the Indian and Eurasian plates [e.g., 75]. The formation of the Yinggehai Basin was controlled by the successive clockwise extrusions of the Indochina Block and the South China

the whole, the depocenters have migrated northward since the Miocene.

laminated aragonite and detrital silt [72].

**4.3. Fault-termination basin: The Yinggehai Basin**

Basin is longer than the total amount of slip along the Dead Sea Fault.

40 Mechanism of Sedimentary Basin Formation - Multidisciplinary Approach on Active Plate Margins

south are 1100, 203, 4–5, and 4 mm, respectively [71].

*4.2.2. Basin-filling processes*

than 2 m kyr-1.

*4.3.1. Geology*

Block.

The Yinggehai Basin, situated in the offshore extension of the RRFZ, is 500 km long and 50–60 km wide (*l*/*w* ≈ 10); it is oriented SE–NW and is located offshore between Hainan Island to the east and the Indosinian Peninsula to the west [73]. The basin formed originally as a sinistral strike-slip basin [77, 86], but developed into a dextral strike-slip basin after the change in the sense of fault displacement of the RRFZ [87, 88]. The basin subsided by simple shear on lowangle, detached normal faults of the upper crust and by pure shear of the lower crust [45, 87].

**Figure 10.** Geological setting of the Red River Fault zone (RRFZ) and the Yinggehai Basin. The RRFZ was originally a left-lateral strike-slip fault caused by the southeastern extrusion of the Indochina Block. The sense of displacement changed to right-lateral in response to the southeastward extrusion of the South China Block. Abbreviations: SMF, Song Ma Fault; HD, Hanoi Depression; GT, Gulf of Tonkin; YB, Yinggehai Basin; MB, Malay Basin; PB, Pattani Basin. The thick blue line marks the cross-sectional profile displayed in Figure 11. Modified from [80, 89, 90].

#### *4.3.2. Basin-filling processes*

The Yinggehai Basin is filled with 10–17-km-thick clastic deposits [45]. Basin sedimentation began in the late Eocene [45, 88]. During the Oligocene (> 21 Ma), clockwise rotation of the Indochina Block induced sinistral slip along the RRFZ and the basin rapidly subsided and started to fill. The depocenter was situated in the southern part of the basin during this synrift stage (Figure 11) [45, 91]. During the quiescent post-rift stage of the RRFZ, the rate of basin subsidence accordingly decreased and the depocenter gradually migrated northwestward [45]. The reactivation of the RRFZ with dextral movement triggered rapid subsidence [80] and enhanced the input of sediment [45]. The depocenter migrated from the center to the south‐ eastern end of the basin (Figure 11).

**4.4. Transpressional basin: The Aceh Basin**

with the data recently collected by [108–110].

Sumatra is a classic example of slip partitioning due to an obliquely subducting plate [14]. The Indian and Australian plates are subducting beneath the Sundaland Plate in southeastern Asia along the Java–Sumatra Trench (Figure 2), where oblique subduction is accompanied by trench-parallel forearc translation [21]. The subduction thrust and the trench-parallel strikeslip fault (Great Sumatra Fault) isolate a wedge of forearc in the form of a sliver plate (the Burma Plate). The Great Sumatra Fault extends along the entire length of Sumatra Island (>1900 km) [22] and finally joins the West Andaman Fault (WAF), which constitutes a series of transform faults and spreading centers in the Andaman Sea [102]. In the forearc sliver, outerarc uplift related to development of the accretionary prisms occurs on the trenchward side, and forearc basins (the Aceh and Simeulue basins) are developed on the landward side.

Strike-Slip Basin – Its Configuration and Sedimentary Facies

http://dx.doi.org/10.5772/56593

43

The Aceh Basin (Figures 12 and 13) is a wedge-shaped forearc basin with a long (> 200 km) and narrow (< 50 km) geometry (*l*/*w*> 4) bounded by the West Andaman Fault, a trench-linked strike-slip fault obliquely crossing the northward extension of the Great Sumatra Fault [103–

**Figure 12.** Physiographic map of the Sumatra region. Purple lines are strike-slip faults. Abbreviations: GSF, Great Su‐ matra Fault; AF, Aceh Fault; SF, Simeulue Fault; WAF, West Andaman Fault; AB, Aceh Basin; TR, Tuba Ridge; TB, Tuba Basin; SM, Simeulue Basin; WB, Weh Basin; BM, Barisan Mountain Range; AVG, Alas Valley Graben; OAH, outer-arc high; ST, Sumatra Trench; AS, Andaman Sea. The Weh Basin and Alas Valley graben are considered to be stepover pull-apart basins [22, 102]. The enclosed area is shown in Figure 13. Bathymetry is based on using SRTM and GEBCO

*4.4.1. Geology*

The infill of the Yinggehai Basin varies from alluvial, fluvial, and lacustrine deposits (before 21 Ma, the syn-rift stage) to marine sediments (after 21 Ma, the post-rift stage) [80]. Almost all the sediments in the basin are considered to have been derived from the Himalayas through the Red River drainage network [92]. Large mountain belts with high rates of sediment yield and along-fault transport networks were able to effectively supply huge volumes of detritus into the basin. Thick sediments and high sedimentation rates resulted in an over-pressured condition leading to mud diapirism [73], and also to depressed surface heat flow (∼80 mW m-2) [93]. The orientations of mud diapirs in the basin (Figure 13) indicate E–W extension related to right-lateral motion of the northeastern bounding fault [89, 90].

The Pattani and Malay basins in the Gulf of Thailand (inset map in Figure 10) are also considered to be fault-termination basins related to the continental collision of the Indian Plate [94, 95, 96]. Sediment supply into the basins is dominated by rivers flowing along the strikeslip faults [97, 98]. The Pattani and Malay basins contain thicknesses of sediment of more than 8 and 14 km, respectively. The subsidence of the basins was controlled at first by tectonic depression related to strike-slip deformation and then by thermal subsidence due to high surface heat flow (100–110 mW m-2) [46, 99–101].

**Figure 11.** Sediment thickness in the Yinggehai Basin along the profile line shown in Figure 10. Red arrows suggest depocenter migration based on the thickest parts of the sediments deposited in each period (shown by solid vertical lines). Modified from [45].
