Showing papers on "Pull apart basin published in 2003"

A flexural model for the Paradox Basin: implications for the tectonics of the Ancestral Rocky Mountains

Abstract: The Paradox Basin is a large (l90km x 265 km) asymmetric basin that developed along the southwestern flank of the basement-involved Uncompahgre uplift in Utah aod Colorado, USA during the Pennsylvaoian-Permian Ancestral Rocky Mountain (ARM) orogenic event. Previously interpreted as a pull-apart basin, the Paradox Basin more closely resembles intraforeland flexural basins such as those that developed between the basement-cored uplifts of the Late Cretaceous-Eocene Laramide orogeny in the western interior USA. The shape, subsidence history, facies architecture, and structural relationships of the Uncompahgre-Paradox system are exemplary of typical \\\'immobile\\\' foreland basin systems. Along the southwest-vergent Uncompahgre thrust, ~ 5km of coarse-grained syntectonic Desmoinesian-Wolfcampiao (mid-Pennsylvaniao to early Permian; -310-260 Ma) sediments were shed from the Uncompahgre uplift by alluvial fans and reworked by aeolian-modified fluvial megafan deposystems in the proximal Paradox Basin. The coeval rise of an uplift-parallel barrier -200 km southwest of the Uncompahgre front restricted reflux from the open ocean south and west of the basin, and promoted deposition of thick evaporite-shale and biohermal carbonate facies in the medial and distal submarine parts of the basin, respectively. Nearshore carbonate shoal and terrestrial siliciclastic deposystems overtopped the basin during the late stages of subsidence during the Missourian through Wolfcampian (-300-260 Ma) as sediment flux outpaced the rate of generation of accommodation space. Reconstruction of an end-Permian two-dimensional basin profile from seismic, borehole, and outcrop data depicts the relationship of these deposystems to the differential accommodation space generated by Pennsylvanian-Permian subsidence, highlighting the similarities between the Paradox basin-fill and that of other ancient and modern foreland basins. Flexural modeling of the restored basin profile indicates that the Paradox Basin can be described by flexural loading of a fully broken continental crust by a model Uncompahgre uplift and accompanying synorogenic sediments. Other thrust-bounded basins of the ARM have similar basin profiles and facies architectures to those of the Paradox Basin, suggesting that many ARM basins may share a flexural geodynamic mechanism. Therefore, plate tectonic models that attempt to explain the development of ARM uplifts need to incorporate a mechanism for the widespread generation of flexural basins.

Hierarchic three-dimensional structure and slip partitioning in the western Dead Sea pull-apart

Abstract: [1] Rifted basins are bounded by marginal belts with fault networks and flexures. We analyze the internal structure of such a belt, the western margins of the Dead Sea basin. This basin is 150 km long, 15–20 km wide with more than 10 km of sediment fill; and it is currently subsiding due to slip of the Dead Sea pull-apart. The western margin of the Dead Sea basin is an elongated N-S belt with an intricate three-dimensional (3-D) pattern of zigzag faults, flexures and joints. The dominant structures are four sets of oblique-normal faults, arranged in orthorhombic symmetry. The faults are steep with prevalent strike directions of NNW and NNE. Large flexures developed along and above these faults, forming tilted blocks and localized asymmetric folds. Two sets of subvertical joints that dominate the area trend NNE and NNW, subparallel to the strikes of the dominant fault sets. The parallel relations between these structures at all scales suggest that they formed during a single tectonic phase. Three-dimensional fault modeling reveals a 3-D strain field with a large vertical shortening, a minor horizontal shortening in N-S direction (belt-parallel) and a large horizontal E-W extension (basinward). The calculated stress fields associated with the zigzag fault segments are compatible with the observed fault-parallel flexures. Further, the calculations predict the formation of local tensile belts above the faults, and these tensile belts could explain the penecontemporaneous development of the two joint sets. Architecture similar to the western margins of the Dead Sea basin is likely to develop on rifted margins wherever 3-D deformation is required by the rifting kinematics.

The stratigraphic and structural evolution of the Dzereg Basin, western Mongolia: clastic sedimentation, transpressional faulting and basin destruction in an intraplate, intracontinental setting

Abstract: The Dzereg Basin is an actively evolving intracontinental basin in the Altai region of western Mongolia. The basin is sandwiched between two transpressional ranges, which occur at the termination zones of two regional-scale dextral strike-slip fault systems. The basin contains distinct Upper Mesozoic and Cenozoic stratigraphic sequences that are separated by an angular unconformity, which represents a regionally correlative peneplanation surface. Mesozoic strata are characterized by northwest and south–southeast-derived thick clast-supported conglomerates (Jurassic) overlain by fine-grained lacustrine and alluvial deposits containing few fluvial channels (Cretaceous). Cenozoic deposits consist of dominantly alluvial fan and fluvial sediments shed from adjacent mountain ranges during the Oligocene–Holocene. The basin is still receiving sediment today, but is actively deforming and closing. Outwardly propagating thrust faults bound the ranges, whereas within the basin, active folding and thrusting occurs within two marginal deforming belts. Consequently, active fan deposition has shifted towards the basin centre with time, and previously deposited sediment has been uplifted, eroded and redeposited, leading to complex facies architecture. The geometry of folds and faults within the basin and the distribution of Mesozoic sediments suggest that the basin formed as a series of extensional half-grabens in the Jurassic–Cretaceous which have been transpressionally reactivated by normal fault inversion in the Tertiary. Other clastic basins in the region may therefore also be inherited Mesozoic depocentres. The Dzereg Basin is a world class laboratory for studying competing processes of uplift, deformation, erosion, sedimentation and depocentre migration in an actively forming intracontinental transpressional basin.

Release faults, associated structures, and their control on petroleum trends in the Recôncavo rift, northeast Brazil

Abstract: Release faults are rift cross faults, which develop to accommodate the variable displacements of the hanging-wall block along the strike of normal faults. Release faults are nearly perpendicular or obliquely oriented to the strike of the normal fault they are related to. They have maximum throws adjacent to the parent normal fault and die out in the hanging wall away from it. They form to release the bending stresses in the hanging wall and do not reflect the orientation of the regional stress field in a basin. Commonly, they show normal-oblique displacements and are preferentially located along the strike ramps. Release faults may also act at the scale of an entire basin, reaching displacements of thousands of meters. Joints, shale, and salt diapirs may develop in association with release faults. Because all these structures represent domains of stress release, they may work as conduits for oil migration and oil traps in extensional basins. This is the case of the Reconcavo basin in northeastern Brazil, a Cretaceous failed rift, connected to the eastern Brazilian continental margin basins. In the Reconcavo basin, two large-scale release faults, with displacements in the order of 3 km, developed in the hanging wall of the rift border faults and control the location of the main oil fields.

Tectonic controls on spatio-temporal development of depositional systems and generation of fining-upward basin fills in a strike-slip setting: Kyokpori Formation (Cretaceous), south-west Korea

Abstract: The Kyokpori Formation (Cretaceous), south-west Korea, represents a small-scale lacustrine strike-slip basin and consists of an ≈ 290 m thick siliciclastic succession with abundant volcaniclasts. The succession can be organized into eight facies associations representing distinctive depositional environments: (I) subaqueous talus; (II) delta plain; (III) steep-gradient large-scale delta slope; (IV) base of delta slope to prodelta; (V) small-scale nested Gilbert-type delta; (VI) small-scale delta-lobe system; (VII) subaqueous fan; and (VIII) basin plain. Facies associations I, III and IV together constitute a large-scale steep-sloped delta system. Correlation of the sedimentary succession indicates that the formation comprises two depositional sequences: the lower coarsening- to fining-upward succession (up to 215 m thick) and the upper fining-upward succession (up to 75 m thick). Based on facies distribution, architecture and correlation of depositional sequences, three stages of basin evolution are reconstructed. Stage 1 is represented by thick coarse-grained deposits in the lower succession that form subaqueous breccia talus and steep-sloped gravelly delta systems along the northern and southern basin margins, respectively, and a sandy subaqueous fan system inside the basin, abutting against a basement high. This asymmetric facies distribution suggests a half-graben structure for the basin, and the thick accumulation of coarse-grained deposits most likely reflects rapid subsidence of the basin floor during the transtensional opening of the basin. Stage 2 is marked by sandy black shale deposits in the upper part of the lower succession. The black shale is readily correlated across the basin margins, indicating a basinwide transgression probably resulting from large-scale dip slip suppressing the lateral slip component on basin-bounding faults. Stage 3 is characterized by gravelly delta-lobe deposits in the upper succession that are smaller in dimension and located more basinward than the deposits of marginal systems of the lower succession. This lakeward shift of depocentre suggests a loss of accommodation in the basin margins and quiescence of fault movements. This basin evolution model suggests that the rate of dip-slip displacement on basin-margin faults can be regarded as the prime control for determining stacking patterns of such basin fills. The resultant basinwide fining-upward sequences deviate from the coarsening-upward cycles of other transtensional basins and reveal the variety of stratigraphic architecture in strike-slip basins controlled by the changes in relative sense and magnitude of fault movements at the basin margins.

The geometry of fan‐deltas and related turbidites in narrow linear basins

Abstract: The sediment distribution in three narrow, linear basins, two modern and one ancient, in Greece and Italy, was studied and related to changes in basin configuration The basins are the Plio-Quaternary Patras–Corinth graben, the Pliocene–Quaternary Reggio–Scilla graben and the middle Tertiary Mesohellenic piggy-back basin These basins were formed at different times and under different geodynamic conditions, but in each case, the tectonic evolution produced a narrow area in the basin where the water depth decreased dramatically, forming a strait with a sill This strait divided the basin into major and minor sub-basins, and the strait has a similar impact on sedimentary environments in all three basins, even though different depositional environments were formed along the initial basin axis Predictions for the development of depositional environments in the two modern basins, especially in their straits, are based on the studied ancient basin In the straits, powerful tidal flows will transport finer sediments to sub-basins and trapezoidal-type fan-deltas will gradually fill up and choke the strait through time In sub-basins, according to basin depth, either deltaic (in the shallow minor sub-basin) or turbiditic (in the deep major sub-basin) deposits may accumulate Moreover, an extensive shelf is likely to develop between the strait and major sub-basin This shelf will be cross-cut by canyons and characterized by thin fineto coarse-grained deposits These sediment models could be applied to analogous basin geometries around the world Copyright # 2003 John Wiley & Sons, Ltd

The Salina del Fraile pull-apart basin, northwest Argentina

Abstract: Abstract The Salina del Fraile in northwest Argentina is a Pliocene to Recent pull-apart basin developed at a releasing stepover along the NNE-SSW-trending El Fraile sinistral strike-slip fault. The basin is 35 km long and 12 km wide with a characteristic rhomboidal shape and is starved of synkinematic sediments thus providing unique 3D exposures. Prominent basin side-wall fault systems form scarps 700 m high and large tilted fault blocks form a terraced system along the southwest basin sidewall. A short-cut, basin-floor fault transects the pull-apart basin connecting the northwest strand of the El Fraile Fault to the southeast strand. An anticlinal positive flower structure in the northwest of the basin is a relict of early, segmented, fault growth typical of strike-slip fault evolution. Extension faults in the basin floor indicate a NE-SW intrabasinal extension direction during the Pliocene to Recent. The pull-apart basin accommodates an estimated 7.7 km of sinistral displacement along the El Fraile fault system. The morphology and fault architecture of the Salina del Fraile pull-apart can be directly compared to scaled sandbox models of strike-slip pull-apart basins. This first detailed analysis of the Salina del Fraile pull-apart basin provides a model for 3D architecture and evolution of similar pull-apart basins, and may serve as a template for the interpretation of other pull-apart systems.

Tectonic evolution of the north jiangsu-south yellow sea basin

Abstract: The North Jiangsu-South Yellow Sea Basin is a composite residual basin superimposed by multistage and multitype basins. They have similar geologic setting and alomost the same genetic evolution. Since the Lower Yangtze Plate was formed in the Proterozoic, the two basins have mainly experinced the Paleo-Mesozoic platform, the Mesozoic foreland basin and the strike-slip extensional basin periods as well as the Cenozoic fault basin and down-warped basin periods. During the Paleo-Mesozoic developing progress, they were a whole mass. In the Late Cretaceous, the differentiation appearred in the evolution of the two basins. Extensional basin groups were developed, and a series of listric fault depressions were formed superimposed on the Meso-Paleozoic basins. The development and distribution of listric fault depressions were apparently controlled by the thrust faults preexisting in the internal of the Paleozoic .

Synclinal-horst basins: examples from the southern Rio Grande rift and southern transition zone of southwestern New Mexico, USA

Abstract: In areas of broadly distributed extensional strain, the back-tilted edges of a wider than normal horst block may create a synclinal-horst basin. Three Neogene synclinal-horst basins are described from the southern Rio Grande rift and southern Transition Zone of southwestern New Mexico, USA. The late Miocene-Quaternary Uvas Valley basin developed between two fault blocks that dip 6-8° toward one another. Containing a maximum of 200 m of sediment, the Uvas Valley basin has a nearly symmetrical distribution of sediment thickness and appears to have been hydrologically closed throughout its history. The Miocene Gila Wilderness synclinal-horst basin is bordered on three sides by gently tilted (10°, 15°, 20°) fault blocks. Despite evidence of an axial drainage that may have exited the northern edge of the basin, 200-300 m of sediment accumulated in the basin, probably as a result of high sediment yields from the large, high-relief catchments. The Jornada del Muerto synclinal-horst basin is positioned between the east-tilted Caballo and west-tilted San Andres fault blocks. Despite uplift and probable tilting of the adjacent fault blocks in the latest Oligocene and Miocene time, sediment was transported off the horst and deposited in an adjacent basin to the south. Sediment only began to accumulate in the Jornada del Muerto basin in Pliocene and Quaternary time, when an east-dipping normal fault along the axis of the synclinc created a small half graben. Overall, synclinal-horst basins are rare, because horsts wide enough to develop broad synclines are uncommon in extensional terrains. Synclinal-horst basins may be most common along the margins of extensional terrains, where thicker, colder crust results in wider fault spacing.

Structural geology of the Neogene Maliau Basin, Sabah

Abstract: The Maliau Basin (Maliau outlier) is made up of about 7,500 metres thick sandstone and mudstone layers deposited in a deltaic-coastal environment, assigned the Kapilit Formation. The layers at the base of the basin consist mainly of mudstones reaching up to 2,000 metres thick. Near the rim of the basin, thick sandstone layers and coal seams occur. Towards the centre of the basin a series of sandstone-dominated and mudstone-dominated sequences of various thicknesses occur. The deposition took slight unconformity place during the Middle Miocene (10-15 million years ago). The basin sits with slight unconformity on older sedimentary rocks (Tanjong Formation), also comprising of thick layers of sandstone and mudstone. The orientation of bedding generally follows the semi-circular shape of the basin. The dip of bedding varies from 5-10 degrees at the centre to 45-50 degrees at the rim. Sub­ vertical to vertical fractures shows four main fracture orientations, NW-SE, NE-SW, NNW-SSE and WNW-ESE. Faulting is quite rare inside the basin. However, outside the basin, minor normal faults occur trending E-W and NE-SW. A sheared zone occurs at the southeastern part of the basin, possibly due to a major fault, the Lonod Fault. Based on regional and local structures the Maliau Basin is interpreted to have. developed initially in an extensional regime, whereby an enormous amount of sediments were deposited in a subsiding basin and later subjected to compression (inversion).

Interpretation of Potential Fields by Modern Data Processing and 3-dimensional gravity Modeling of the Dead Sea Pull-Apart Basin / Jordan Rift Valley (JRV)

Abstract: This work presents the analysis, 3D modeling and interpretation of gravity and aeromagnetic data of Jordan and Middle East. The potential field data delineate the location of the major faults, basins, swells, anticlines, synclines and domes in Jordan. The surface geology of Jordan and the immediate area east of the Rift is dominated by two large basins, the Al-Jafr basin in the south and the Al-Azraq-Wadi as Sirhan basin to the northeast. These two basins strike southeast-northwest and are separated by an anticlinal axis, the Kilwah-Bayir swell. The Karak Wadi El Fayha fault system occurs along the western flank of the swell. The Swaqa fault occurs on the southwest hinge of Al-Azraq basin and the Fuluq fault occurs on its northeast hinge. In the south west of Jordan, Wadi Utm-Quwaira and Disi-Mudawara fault zones are shown clearly in the aeromagnetic and gravity maps. The previous major faults are well correlated with the structural map of Jordan published by Bender (1968). 3D modeling of gravity data in the Dead Sea basin (DSB) was used together with existing geological and geophysical information to give a complete structural picture of the basin. The 3D models of the DSB show that the internal structure of the Dead Sea basin (DSB) is controlled by longitudinal faults and the basin is developed as a full graben bounded by sub-vertical faults along its long sides. In the northern planes of the 3D model, the accumulation of Quaternary (salt and marl) and Mesozoic (pre-rift) sediments are thinner than in the central and southern planes of the model. In the northern planes, the thickness of the Quaternary sediments is about 4 km, 5 km in the southern planes and it exceeds 8 km in the central planes of the DSR. The thickness of the pre-rift sediments reaches 10-12 km in the northern and southern planes and exceeds 15 km in the central planes of the DSR. The planes of the 3D models show that the depth to the crystalline basement under the eastern shoulders of the DSR is shallower than those beneath the western shoulders. It is about 3-5 km beneath the eastern shoulders and 7-9 km under the western shoulder of the DSR. The gravity anomaly maps of residual and first derivative gravity delineate the subsurface basins of widely varying size, shape, and depth along the Rift Valley. The basins are created by the combination of the lateral motion along a right-tending step over and normal faulting along the opposite sides. Al Bakura basin occupies the upper Jordanian River valley and extends into the southern Tiberias Lake. Bet Shean basin to the south of Al Bakura basin plunges asymmetrically toward the east. The Damia basin, comprising the central Jordan Valley and Jericho areas to the north of the Dead Sea is shallow basin (~600-800m deep). The Lisan basin is the deepest basin in the Rift. The 3D gravity models indicate a maximum of ~12 km of basin fill. Three basins are found in Wadi Araba area, Gharandal, Timna (Qa'-Taba) and Aqaba (Elat) basin. The three basins become successively wider and deeper to the south. The three regional gravity long E-W profiles (225 km) from the Mediterranean Sea crossing the Rift Valley to the east to the Saudi Arabia borders, show the positive correlation between topography and free air anomaly and strong negative Bouguer anomaly under the central part of the Dead Sea Basin (DSB) and normal regional Bouguer anomaly outside of the DSB in the transform valley. Depth to the top of the bedrock in the under ground of Jordan was calculated from potential field data. The basement crops out in the south west of Jordan and becomes deeper to northwards and eastwards to be about ~ 8 km below ground surface in the Risha area.

Structural Pattern and Structural Style of the Southern North China Basin

Abstract: Detailed studies indicate that southern North China basin is a Meso-Cenozoic basin intimately related to the Qinling-Dabie orogenic belt. The fault system of the basin is composed of NWW-EW,NE-NNE, and NS faults.Formation of subdepressions in the southern North China basin was controlled by NWW-EW and NE-NNE faults. The NS fault is a strike-slip fault with the function of transformation and adjustment.The structural styles of the southern North China Basin include thrust,basin and range,strike-slip,flower structure and inversion.

Contribution of bathymetry and geomorphology to the geodynamics of the East Indonesian Seas

Abstract: Southeastern Indonesia is located at a convergent triple junction of 3 plates : the Pacific (including the Caro-line and Philippines plates), the Australian and the Southeast Asian plates (fig. 1). The age of the different basins : the North Banda Sea (Sula Basin), the South Banda Sea (Wetar and Damar Basins) and the Weber Trough has been debated for a long time. Their great depth was a reason to interpret them as remnants of oceanic domains either of Indian or Pacific ocean affinities. It has now been demonstrated from geochronological studies that these basins have formed during the Neogene [Rehault et al. , 1994 ; Honthaas et al. , 1998]. The crust has been sampled only in the Sula Basin, where basalts or trachyandesites with back-arc geochemical signatures have been dredged. Their ages range from 11.4 ± 1.15 to 7.33 ± 0.18 Ma [Rehault et al. , 1994 ; Honthaas et al. , 1998]. The study of the magnetic anomaly pattern of these basins confirms this interpretation and defines an age between 12.5 and 7.15 Ma for the North Banda Basin and between 6.5 to 3.5 Ma for the South Banda Basin [Hinschberger et al. , 2000 ; Hinschberger et al. , 2001]. Furthermore, the existence of volcanic arcs linked to subducted slabs suggests that these basins resulted from back-arc spreading and subduction slab roll-back. Lastly, the Weber Trough which exceeds 7 300 m in depth and is one of the deepest non subduction basins in the world, remains enigmatic. A compilation of existing bathymetric data allows us to present a new bathymetric map of the region (fig. 2 and 3). A comparison with the previous published maps [Mammerickx et al. , 1976 ; Bowin et al. , 1982] shows numerous differences at a local scale. This is especially true for the Banda Ridges or in the Sula Basin where new tectonic directions are expressed. In the North Banda Basin, the Tampomas Ridge, which was striking NE-SW in the previous maps, is actually NW-SE parallel to the West Buru Fracture Zone and to the Hamilton Fault scarp (fig. 6). This NW-SE direction represents the initial direction of rifting and oceanic spreading. In this basin, only the southeastern rifted margin morphology is preserved along the Sinta Ridges. The basin is presently involved in an overall compressional motion and its buckled and fractured crust is subducted westwards beneath East Sulawesi (fig. 4a, 5 and 6). The northern border of the North Banda Basin is reactivated into sinistral transcurrent motion in the South Sula Fracture Zone continued into the Matano fault in Sulawesi. The South Banda Sea Basin is divided in two parts, the Wetar and Damar Basins with an eastward increase in depth. The Wetar and Damar Basins are separated by the NNW-SSE Gunung Api Ridge, characterized by volcanoes, a deep pull apart basin and active tectonics on its eastern flank (fig. 4b and 7). This ridge is interpreted as a large sinistral strike-slip fracture zone which continues across the Banda Ridges and bends towards NW south of Sinta Ridge. The Banda Ridges region, separating the North Banda Basin from the southern Banda Sea (fig. 5 and 7), is another place where many new morphological features are now documented. The Sinta Ridge to the north is separated from Buru island by the South Buru Basin which may constitute together with the West Buru Fracture Zone a large transcurrent lineament striking NW-SE. The central Rama Ridge is made of 2 narrow ridges striking NE-SW with an « en-echelon » pattern indicating sinistral strike slip comparable to the ENE-WSW strike-slip faulting evidenced by focal mechanisms in the northern border of the Damar Basin [Hinschberger, 2000]. Dredging of Triassic platform rocks and metamorphic basement on the Sinta and Rama Ridges suggests that they are fragments of a continental block [Silver et al. , 1985 ; Villeneuve et al. , 1994 ; Cornee et al. , 1998]. The Banda Ridges are fringed to the south by a volcanic arc well expressed in the morphology : the Nieuwerkerk-Emperor of China and the Lucipara volcanic chains whose andesites and arc basalts have been dated between 8 and 3.45 Ma [Honthaas et al. , 1998]. Eastern Indonesia deep oceanic basins are linked to the existence of 2 different subduction zones expressed by 2 different downgoing slabs and 2 volcanic arcs : the Banda arc and the Seram arc [Cardwell et Isacks, 1978 ; Milsom, 2001]. They correspond respectively to the termination of the Australian subduction and to the Bird’s head (Irian Jaya) subduction under Seram (fig. 5). Our bathymetric study helps to define the Seram volcanic arc which follows a trend parallel to the Seram Trench from Ambelau island southeast of Buru to the Banda Island (fig. 2 and 5). A new volcanic seamount discovered in the southeast of Buru (location of dredge 401 in figure 7) and a large volcano in the Pisang Ridge (location of dredge 403 in figure 7 and figure 8) have been surveyed with swath bathymetry. Both show a sub-aerial volcanic morphology and a further subsidence evidenced by the dredging of reefal limestones sampled at about 3000 m depth on their flank. We compare the mean basement depths corrected for sediment loading for the different basins (fig. 9). These depths are about 5 000 m in the Sula Basin, 4 800 m in the Wetar basin and 5 100 m in the Damar basin. These values plot about 1 000 m below the age-depth curve for the back-arc basins [Park et al. , 1990] and about 2000 m below the Parsons and Sclater’s curve for the oceanic crust [Parsons et Sclater, 1977]. More generally, eastern Indonesia is characterized by large vertical motions. Strong subsidence is observed in the deep basins and in the Banda Ridges. On the contrary, large uplifts characterize the islands with rates ranging between 20 to 250 cm/kyr [De Smet et al. , 1989a]. Excess subsidence in the back-arc basins has been attributed to large lateral heat loss due to their small size [Boerner et Sclater, 1989] or to the presence of cold subducting slabs. In eastern Indonesia, these mechanisms can explain only a part of the observed subsidence. It is likely that we have to take into account the tectonic forces linked to plate convergence. This is supported by the fact that uplift motions are clearly located in the area of active collision. In conclusion, the bathymetry and morphology of eastern Indonesian basins reveal a tectonically very active region where basins opened successively in back-arc, intra-arc and fore-arc situation in a continuous convergent geodynamic setting.

Tectonic subsidence and its control on hydrocarbon resources in the wan'an basin in the south china sea

Abstract: The Wan'an basin is a typical Cenozoic shearextensional basin in the southwest of the South China Sea. Inferred from the results of tectonic subsidence modeling for the seismic profiles across the basin and from the calculation of the faulting movement velocity in the basin, it has undergone four tectonic subsidence processes since early Eogene period, and most of the faults are growth ones coming from the basement. The faults were strongly active when the basin underwent shearextension and riftdepression subsidence from late Oligocene to early Miocene. The geological factors and processes for hydrocarbon formation, migration, accumulation and preservation were controlled by the tectonic subsidence stages.

Orogeny and coupled/decoupled basin developing:application in petroliferous basin analyses

Abstract: Chinese geologists had a correct understanding of some specific characteristics on petroliferous basins in China continent, and named them superimposed basin, composite one, reformed one, residual one, relict one, etc. The paper aimed to deepen our comprehensions on the basins' mechanics and features in the light of orogeny and coupled/decoupled basin developing. The creation of inheritance-type of superimposed basin, with the Junggar Basin being an example, was caused by a "basin"-"orogen"relation constituted in the Hercynian orogeny keeping on during Meso-Cenozoic, not decoupled so far. If a "basin"-"orogen"relation setting up in the Indosinian orogeny decoupled and a part of cratonic area locked in the Yanshanian or Himalayan movement, the part could be classified into alteration-type of superimposed basin. Taking the Sichuan, Ordos and Tarim Basins as an instance, the locked conditions were analysed thoroughly. The essence of basin superimposition should be a replacement of "basin"-"orogen"system. Some possibly complicated cases of replacement of "basin"-"orogen"system were discussed in the paper. Composite basin might occur in every stage of an orogenic process. Some so called "composite basin", for example, the Chuxiong Basin in Yunnan, might be a sediments' collage, which resulted from migration and collage of sediments originally in varied basins by multiple orogenies. Residual basin was different from relict basin which was a prototype one. To study a residual basin, the key problem might be mode or style of basin reformation, and then the conditions for secondary hydrocarbon generation in later period. A new leap of oil-gas exploration in China would depend on new progresses of understanding on the residual marine basins in age of Paleozoic and Early-Middle Triassic; and the leap of oil-gas exploration would carry on within a new theoretical frame. The orogeny and coupled/decoupled basin developing, dealing with a uniform kinematic process and geodynamic mechanics between "basin" and "orogen", would play an important role in the new leap.

Deep geological feature and dynamic evolution of the songliao basin

Abstract: The Songliao basin located in Northeast China is a large Mesozoic rift basin. A lot of work has been done on the geological characteristics, formation and evolution of the basin, as well as the accumulation regularity of oil and gas in this basin. However, the question about the formation of the basin is still a point at issue, and has attracted the great attention of many geologists. Various models have been proposed so far for the formation of the basin, such as continent rift, back arc rift, and pull apart models. Basing on deep seismic reflection data, this paper discusses the type of the basin and the geodynamic cause of its formation. Deep seismic reflection profiling has revealed that the crust of the Songliao basin is characterized by both layered and fault block structures. The crust can be divided into three layers: the upper crust, middle crust and lower crust. Parallel reflections in shallow layer and oblique reflections at above 6s twt represent the upper crust. The strong reflection belt below the upper crust represents the detachment zone between the upper and middle crust. Most of the faults in the upper crust terminate in this zone. The analysis shows that the faults in the upper crust are extensional syn sedimentary faults formed during late Jurassic to early Cretaceous and thrust system formed in late Paleozoic era. The middle crust at about 6~8s twt not only has a lot of discontinuous parallel reflections and rhombic reflections, but also a small quantity of "crocodile mouth" reflectors. The former represents extensional reformation formed in late Mesozoic era, and the later represents compressional structure formed in late Paleozoic era. The middle crust is also a low velocity and high conductivity layer. The lower crust is located at about 8～11s twt, and is characterized by rhombic reflection events. The Moho below the lower crust appears as a strong reflection belt, beneath which the layer is transparent. The reflection structure of the Songliao basin is similar to that of typical rift basin. Boundary faults between blocks were the passage of upward transferring of hot fluid from the middle lower crust or mantle to the basin. "Mushroom cloud" reflections at the deep part of the boundary faults might be the reflections of hot fluid diapir. Mirror symmetry between the down warped basin and mantle uplift is the main evidence for the rift origin of the Songliao basin. Deep seismic reflection data indicate that the main factor at depth that affected the subsidence of the basin was not only the uplift of the mantle, but also the "low velocity high conductivity" layer in the upper middle crust and hot fluid diapirs. The former caused the subsidence in later stage, while the later caused the subsidence in early stage. Regional geology and geophysical data indicate that this area is located in back arc formed by the subduction of the Kula pacific plate into the Eurasia plate in Mesozoic. Mesozoic volcanic rock system in this area is mainly of CA series, with a few exception of a small amount of A and Th type. Geochemical analysis reveals that the volcanic rocks here are characterized not only by high SiO 2 and K 2O contents and enrichment in LREE, but also by EMII type mantle, indicating back arc environment disturbed by plate subduction. However, seismic tomography data have revealed that the Songliao basin is located in disturbed area of continental mantle, rather than back arc area. It is suggested, therefore, that formation and evolution of the Songliao basin was the result of the subduction of Kula Pacific plate into the Eurasian plate. The plate subduction has led to the uplift and diapir of the mantle, and the detachment of the crust. Strong crust mantle interaction has led to the delimitation and extension of the crust, resulting in the formation of sandwich structure and large scale subsidence of the crust. It was the afore mentioned factors that caused the formation of mirror symmetry between the downwarping part of the basin and the uplifting part of the mantle, a

Cenozoic Dynamics of Baikal and Khubsugul Basins

Abstract: The Baikal and Khubsugul basins of the Baikal rift system are the largest lake basins of Siberia. Despite of the widespread opinion of close relationship between these lake basins, their structural position and the mode of geodynamical development have some considerable differences. The major similarities are: location on the boundaries between the Paleozoic tectonic blocks of a roughly similar strike; asymmetry of the cross-section (half-grabens); high-amplitude vertical movements along the boundary faults; the existence of domal uplift; high-value heat flow through the bottom of the basins. The main differences in geodynamical development of the basins are the following: different age of initiation of the basins; different dimensions and complexity of the basin structures; the two-stage volcanism in Hubsugul area and its absence in the Baikal basin; different mode of development of the state of paleostress; normal-fault type of displacements along active (Late Pleistocene-Holocene) faults for the Baikal basin and strike-slip type of it with a “passive” subsidence of blocks for the Khubsugul basin; relative homogeneity of the recent state of stress of the Earth’s crust of the Baikal basin (conditions of extension) and a spatial replacement of pure compression by the N-S extension for the Khubsugul basin; type of recent horizontal movements of the Earth’s crust – divergent for the Baikal basin and oblique-slip for the Khubsugul basin; high-rate sagging of the bottom of the Baikal basin and more than a moderate rate of it in the Khubsugul basin; high seismic activity of the Baikal basin, and relatively low- of the Khubsugul basin. The differences in geodynamical development of the basins are mainly determined by their position in relation to rather large lithospheric inhomogeneity of the Central Asia – the margin of the Siberian platform. The geodynamical setting determines the trend of the morphological development of the basins – proceeding deepening of the Baikal basin and slight subsidence of the northern part of the Khubsugul basin, which affects the mode of sedimentation and development of the organic world along with a different elevation of basins.

Contrasting basin fills in a strike-slip setting, Eumsung Basin (Cretaceous), Korea

Abstract: In a strike-slip setting, depositional history of marginal and central basins depends on the basin formation and basinal fault movements. The Eumsung Basin contains contrasting basin fills according to marginal settings. The southeastern part of the basin forms sequential development of alluvial/lacustrine systems along transform margin, and the southwestern part constitutes synchronous development of alluvial-to-lacustrine systems in pull-apart margin. Along the basin margins and toward the basin center, both sequential and synchronous developments of the alluvial and lacustrine systems have filled basinal accommodation spaces created by pull-apart opening. The formative processes of the basin were caused by the strike-slip fault movements and the accompanying changes in drainage network along the basin margin. The overall development patterns of the depositional systems conform to the sinistral strike-slip fault activation during the Early Cretaceous.

Subsidene and tectonic evolution of the beikang basin, the south china sea

Abstract: The Beikang basin lies in the middle of the Nansha sea area and its geotectonic location belongs to the southwest boundary of the Nansha massif.The north part of the basin is separated from Nanweixi and Nanweidong basins by faults,3 000 m isopach and island reefs,the Tingjia fault bounds the southwest of the basin,and the northwest edge fault of the Nansha Trough acts as the east boundary of the basin.The basin covers an area of 62×104 km2.Tectonic subsidence is determined and the relation between the tectonic evolution and the regional tectonic movements in the Beikang basin studied on the basis of the geologic tectonic features and by using the backstripping technique and 1D Airy isostasy correction The results show that the Beikang basin is an extensional basin that has experienced three phases of subsidence and three stages of tectonic evolution. Rapid subsidence in middle Eocene made up 28%～34% of the total subsidence with a subsidence rate of 234～325 m/Ma and the maximum extensional coefficient is 172. And it was associated with the collision of the Eurasia and Pacific plates. Tectonic subsidence during late Eoceneearly Oligocene was slower and associated with the strikeslip of the eastern VietnamWan'an fault. Rapid subsidence in PlioceneQuaternary made up 40% of the total subsidence and was controlled by the regional subsidence of the South China Sea influenced by subduction of the Pacific plate beneath the Eurasia plate.

The current activity of main faults in the joint area of Shanxi, Hebei and Inner Mongolia

Abstract: the current activity of 13 main faults in the joint area of Shanxi, Hebei and Inner Mongolia is analysed with levelling geodetic data. The results show that at all the segments that active faults passed have turnings and kicks in the profile of deformation. The current activity of faults is consistent with the inherited activity, but the velocity is not uniform, sometimes fast and sometimes low, sometimes even reverse; the motion in some segments is active but weak in other segments on the same fault. During 1983～1992, the most active faults that mean rate is over 2mm/a are the fault on north margin of Huaianzhen basin and the fault on north margin of Huaizhuo basin; the relative active faults that mean rate is 1.0-1.9 are the fault north Hengshan, south margin fault of Huaianzhen basin, the fault front Taibaishan, the west segment of south margin fault in Wei-Guang basin, the north margin fault of Yanfan basin, Zhangjiakou fault, north Wutaishan fault; the weak active faults that rate is lower than 1mm/a are the east segment of south margin fault in Wei-Guang basin, the fault south Hengshan, the fault north Liulengshan and the fault on the north margin of Yangyuan basin.

Geological model of the mugland basin -an identical example of basin evolution at the end of giant strike-slip faults

Abstract: The basin evolution at the end of giant Central African strike slip fault is closely related to the regional tectonic background. Evolution of the basin in the Early Cretaceous resulted from the seperation of Atlatic Ocean, and that in the Later Cretaceous from the northward movement of the India plate . The spreading of Red Sea in the Cenozoic have also influenced the evolution of the basin. Three stages of the structural evolution for the basin can be classified: Early Cretaceous, Late Cretaceous and Cenozoic. In the Early Cretaceous, owing to activity of the central African strike slip fault, the subsidence speed was enormous, in which the depositional and subsiding centers were not in the same position. In the Late Cretaceous, the basin was dominated by both rifting and sag, and the depositional center moved towards the southeast of the basin where was far away from the central African fault. In general scene, the structural evolution for the basin was transformed from the strike slip to the extensional system. Potential source rocks and reservoirs were developed along the central African fault in the early evolution of the basin. Under the structural compression in the late stage, some oil and gas pools could be destroyed, and resulted in hydrocarbon redistribution and formation of new accumulations. The difference in depositional and subsiding centers brought out the difficulty in exploration. In the southeast of the basin far away from the central African fault, the main source rocks were matured properly, and depositional and subsiding centers were in the same place, so many industrial oil and gas fields have been found.

Analysis of Origin of the Early Cretaceous Dasheng-Mazhan Basin in the North Part of Yi shu Fracture

Abstract: In order to analyze the origin of the Dasheng Mazhan basin in the north part of Yi Shu fracture, the spatial distribution regulation that suggests the depocenter of the basin migrated northerly is investigated The sedimentary structures in the basin indicate that the major boundary faults of the basin are left slip faults The collected fossils and the age of volcanic rocks determined in the basin illustrate that the basin developed in Early Cretaceous The Dasheng Mazhan basin is a typical sinistral pull apart basin, which suggests that the Tanlu fault zone underwent sinistral strike slip during Early Cretaceous

Physical experimentas on strike-slip fault and pull-apart basin

Abstract: According to the theory that plastic flow of the lower layer(including lower crust and upper mantle lithosphere)controls upper layer (upper crust)deformation in the multilayer lithosphere,the paper studies the physical experiments of strikeslip fault and pullapart basin adopted ductile/brittle doublelayers model. The experiment results show that strikeslip model developed sinistral rightstep fault zone which consisted of a lot of \!S\"type faults during sinistral strikeslip stage. The early fault zone was reconstructed and became dextral rightstep \!Z\"type fault during dextral strikeslip stage.There are threetype extensions in the strikeslip fault zone:(1)a lot of diamond basins formed with stretching of "S"type fault;(2)the "grabenhorst" structure appeared when the ends of adjacent "S"faults were sheared and connecting;(3)the pullapart basins formed along right steps of dextral faults during the second strikeslip stage. The stretching faults formed in the stage of uplifting limit the location and the direction of strikeslip faults.Strength of brittlelayer restricts the forming and the development of strikeslip faults,and the texture of brittlelayer influences coupling of brittleplastic layers and characters of strikealip faults.