首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Detailed field investigations do not support the existence of a ‘Gangdese thrust’ along the Yarlung Tsangpo suture zone in southern Tibet. A relationship where Lhasa terrane rocks are thrust southwards over components of this zone was not observed over 2000 km of the suture. On the contrary, at the type locality of this ‘Gangdese thrust’, Miocene conglomerates unconformably overlie an eroded surface of Lhasa terrane rocks. Interpretations that invoke Late Oligocene – Early Miocene south‐directed thrusting on a ‘Gangdese thrust’ as a mechanism for uplift of the Tibetan Plateau must therefore be reassessed.  相似文献   

2.
The Thakkhola–Mustang graben is located at the northern side of the Dhaulagiri and Annapurna ranges in North Central Nepal. The structural pattern is mainly characterised by the N020–040° Thakkhola Fault system responsible for the development of the half-graben. A detailed study of the substrate and the sedimentary fill in several outcrops indicates polyphased faulting:-pre-sedimentation faulting (Miocene), with a mainly NNW–SSE to N–S compressional stress expressed in the substratum by N020–040° and N180–N010° sinistral and N130–140° dextral conjugate strike-slip faults;-syn-sedimentation faulting (Pliocene–Pleistocene), characterised by a W–E to WNW–ESE extensional stress and tectonic subsidence of the half-graben during the Tetang period (Pliocene probably), followed by a doming of the Tetang deposits and a short period of erosion (cf. Pliocene planation surface and unconformity between the Tetang and Thakkhola Formations); the Thakkhola period (Pleistocene) is characterized by a W–E to WNW–ESE extensional stress and a major subsidence of the half graben;-post-sedimentation recurrent extensional faulting and N–S and NE–SW normal faults in the late Quaternary terrace formations.Geodynamic interpretation of the faulting is discussed in relation to the following:
  • 1.the geographic situation of the Thakkhola–Mustang half-graben in the southern part of Tibet and its setting in the Tethyan series above the South Tibetan Detachment System (STDS);
  • 2.the geodynamic conditions of the convergence between India and Eurasia and the dextral east–west shearing between the High Himalayas and south Tibet;
  • 3.the possible relations between the sinistral Thakkhola and the dextral Karakorum strike-slip faults in a N–S compressional stress regime during the Miocene.
  相似文献   

3.
《Sedimentary Geology》2005,173(1-4):373-408
The Alaşehir (Gediz) Graben exemplifies clastic sedimentation in a long-lived continental half-graben in a semi-arid setting, developed within relatively incompetent metamorphic rocks. Early Miocene to Recent rift-related sediments are exhumed on both flanks of the graben, allowing detailed three-dimensional study. During the Early Miocene, small fan-delta lobes were shed northwards from the rugged Menderes Metamorphic Massif into a bordering lacustrine basin. During Early to Mid-Miocene time, large alluvial fans prograded northwards into this basin. Through-drainage to the Aegean Sea was established as the basin widened and filled. Discrete lobes of coarse alluvial fan sediments of latest Miocene(?)–Pliocene age, also shedding northwards, are likely to have been climatically influenced. Quaternary alluvium party infills the modern Alaşehır rift basin.The sedimentary information can be used to test two alternative tectonic models for the Alaşehır Graben. In the first model, an E–W graben bounded by high-angle faults was active during latest Miocene(?)–Recent time, whereas earlier Miocene sedimentation was controlled by N–S faulting related to a N–S compressional stress regime. In the second hypothesis, the Alaşehır Graben was initiated much earlier, in the Early Miocene and was then either continuously or episodically active until Recent. Our results, especially facies and palaeocurrent data from alluvial sediments, indicate that clastic sedimentation was controlled by mainly E–W faulting in a N–S stress regime. Assuming the Early Miocene clastic sediments are correctly dated, this supports the second (long-lived extension) model. However, rather than steady-state extension for ca. 15 Ma, the sedimentary evidence and regional context are consistent with a pulsed extension model, whereby initial Early to Mid-Miocene extension and related clastic sedimentation was followed by a second phase of extension in latest Miocene(?)–Pliocene time. The driving force of initial, Early Miocene extension was probably gravity spreading towards a south-Aegean subduction zone, whereas the inferred second extension pulse is seen as being triggered by westward “tectonic escape” of Anatolia towards the extending Aegean back-arc region.  相似文献   

4.
《Geodinamica Acta》2001,14(1-3):45-55
Field studies on the Neogene successions in south of İzmir reveal that subsequent Neogene continental basins were developed in the region. Initially a vast lake basin was formed during the Early–Middle Miocene period. The lacustrine sediments underwent an approximately N–S shortening deformation to the end of Middle Miocene. A small portion of the basin fill was later trapped within the N–S-trending, fault-bounded graben basin, the Çubukludağ graben, opened during the Late Miocene. Oblique-slip normal faults with minor sinistral displacement are formed possibly under N–S extensional regime, and controlled the sediment deposition. Following this the region suffered a phase of denudation which produced a regionwide erosional surface suggesting that the extension interrupted to the end of Late Miocene–Early Pliocene period. After this event the E–W-trending major grabens and horsts of western Anatolia began to form. The graben bounding faults cut across the Upper Miocene–Pliocene lacustrine sediments and fragmented the erosional surface. The Çubukludağ graben began to work as a cross graben between the E–W grabens, since that period.  相似文献   

5.
The pre-Neogene Tauride fold-and-thrust belt, comprising Cretaceous ophiolites and metamorphic rocks and non-metamorphic carbonate thrust slices in southern Turkey, is flanked and overlain by Neogene sedimentary basins. These include poorly studied intra-montane basins including the Yalvaç Basin. In this paper, we study the stratigraphy, sedimentology and structure of the Yalvaç Basin, which has a Middle Miocene and younger stratigraphy. Our results show that the basin formed as a result of multi-directional extension, with NE–SW to E–W extension dominating over subordinate NW–SE to N–S extension. We show that faults bounding the modern basin also governed basin formation, with proximal facies close to the basin margins grading upwards and basinwards into lacustrine deposits representing the local depocentre. The Yalvac Basin was a local basin, but a similar, contemporaneous history recently reconstructed from the Alt?napa Basin, ~100 km to the south, shows that multi-directional extension dominated by E–W extension was a regional phenomenon. Extension is still active today, and we conclude that this tectonic regime in the study area has prevailed since Middle Miocene times. Previously documented E–W shortening in the Isparta Angle along the Aksu Thrust, ~100 km to the southwest of our study area, is synchronous with the extensional history documented here, and E–W extension to its east shows that Anatolian westwards push is likely not the cause. Synchronous E–W shortening in the heart and E–W extension in the east of the Isparta Angle may be explained by an eastwards-dipping subduction zone previously documented with seismic tomography and earthquake hypocentres. We suggest that this slab surfaces along the Aksu thrust and creates E–W overriding plate extension in the east of the Isparta Angle. Neogene and modern Anatolian geodynamics may thus have been driven by an Aegean, Antalya and Cyprus slab segment that each had their own specific evolution.  相似文献   

6.
Al Jabal Al Akhdar is a NE/SW- to ENE/WSW-trending mobile part in Northern Cyrenaica province and is considered a large sedimentary belt in northeast Libya. Ras Al Hilal-Al Athrun area is situated in the northern part of this belt and is covered by Upper Cretaceous–Tertiary sedimentary successions with small outcrops of Quaternary deposits. Unmappable and very restricted thin layers of Palaeocene rocks are also encountered, but still under debate whether they are formed in situ or represent allochthonous remnants of Palaeocene age. The Upper Cretaceous rocks form low-lying to unmappable exposures and occupy the core of a major WSW-plunging anticline. To the west, south, and southeast, they are flanked by high-relief Eocene, Oligocene, and Lower Miocene rocks. Detailed structural analyses indicated structural inversion during Late Cretaceous–Miocene times in response to a right lateral compressional shear. The structural pattern is themed by the development of an E–W major shear zone that confines inside a system of wrench tectonics proceeded elsewhere by transpression. The deformation within this system revealed three phases of consistent ductile and brittle structures (D1, D2, and D3) conformable with three main tectonic stages during Late Cretaceous, Eocene, and Oligocene–Early Miocene times. Quaternary deposits, however, showed at a local scale some of brittle structures accommodated with such deformation and thus reflect the continuity of wrenching post-the Miocene. D1 deformation is manifested, in Late Cretaceous, via pure wrenching to convergent wrenching and formation of common E- to ENE-plunging folds. These folds are minor, tight, overturned, upright, and recumbent. They are accompanied with WNW–ESE to E–W dextral and N–S sinistral strike-slip faults, reverse to thrust faults and pop-up or flower structures. D2 deformation initiated at the end of Lutetian (Middle Eocene) by wrenching and elsewhere transpression then enhanced by the development of minor ENE–WSW to E–W asymmetric, close, and, rarely, recumbent folds as well as rejuvenation of the Late Cretaceous strike-slip faults and formation of minor NNW–SSE normal faults. At the end of Eocene, D2 led to localization of the movement within E–W major shear zone, formation of the early stage of the WSW-plunging Ras Al Hilal major anticline, preservation of the contemporaneity (at a major scale) between the synthetic WNW–ESE to E–W and ENE–WSW strike-slip faults and antithetic N–S strike-slip faults, and continuity of the NW–SE normal faults. D3 deformation is continued, during the Oligocene-Early Miocene, with the appearance of a spectacular feature of the major anticline and reactivation along the E–W shear zone and the preexisting faults. Estimating stress directions assumed an acted principal horizontal stress from the NNW (N33°W) direction.  相似文献   

7.
Suture zones often archive complex geologic histories underscored by episodes of varying style of deformation associated with intercontinental collision. In the Lopukangri area of south-central Tibet (29°54′N, 84°24′E) field relationships between tectonic units juxtaposed by the India–Asia suture are well exposed, including Indian passive margin rocks (Tethyan Sedimentary Sequence), forearc deposits (Xigaze Group), magmatic arc rocks (Gangdese batholith and Linzizong Formation) and syncollision deposits (Eocene–Miocene conglomerates). To better understand the structural history of this area, we integrated geologic mapping with biotite 40Ar/39Ar thermochronology and zircon U–Pb geochronology. The first-order structure is a system of north-directed thrusts which are part of the Great Counter thrust (GCT) that places Indian passive margin rocks and forearc deposits on top of magmatic arc rocks and syn-tectonic conglomerates. We infer the south-directed Late Oligocene Gangdese Thrust (GT) exists at unexposed structural levels based on field mapping, cross sections, and regional correlations as it has been documented immediately to the east. A granite in the footwall has a U–Pb zircon age of 38.4 ± 0.4 Ma, interpreted to be the age of emplacement of the granite, and a younger 40Ar/39Ar biotite age of 19.7 ± 0.1 Ma. As the granite sample is situated immediately below a nonconformity with low grade greenschist facies rocks, we interpret the younger age to reflect Miocene resetting of the biotite Ar system. Syn-tectonic deposits in the Lopukangri area consist of three conglomerate units with a total thickness of ∼1.5 km. The lower two units consist of cobble gravel pebble conglomerates rich in volcanic and plutonic clasts, transitioning to conglomerates with only sedimentary clasts in the upper unit. We correlate the syncollision deposits to the Eocene–Oligocene Qiuwu Formation based on field relationships, stratigraphy and petrology. Petrology and clast composition suggest the lower two units of the Qiuwu Formation had a northern provenance (Lhasa block and magmatic arc) and the upper unit had a southern provenance (Tethyan Sedimentary Sequence). Our observations are consistent with paleocurrent data from other studies which suggest a predominant south-directed paleoflow for this formation. We propose a model in which: (1) granites intrude at 38.4 ± 0.4 Ma; (2) are exhumed by erosion; (3) and buried due to regional subsidence and initial deposition of a conglomerate unit; (4) exposed by the GT at ∼27–24 Ma to provide detritus; (5) buried a second time by hanging wall-derived sedimentary deposits and the GCT, then (6) exposed from a depth of ∼12–10 km by a blind thrust at ∼19 Ma. An alternate model describes: (1) intrusion of the granites at 38.4 ± 0.4 Ma, followed by (2) exhumation of the granites via normal faulting to provide detritus; (3) then burial by the GCT at ∼24 Ma, followed by (4) exhumation via regional erosional denudation at ∼19 Ma. Exposure of the GT west of Xigaze has not been confirmed. We suggest that shallower structural levels of the India-Asia suture zone are exposed to the west of the study area, compared to the east, where the GT has been previously documented. The GCT in the area is short-lived, as it is cut and offset by a Middle Miocene ∼N-striking W-dipping oblique normal fault system.  相似文献   

8.
Geologic mapping and U–Pb detrital zircon geochronologic studies of (meta)sedimentary rocks in the Damxung area (∼90 km north of Lhasa) of the southern Lhasa terrane in Tibet provide new insights into the history of deformation and clastic sedimentation prior to late Cenozoic extension. Cretaceous nonmarine clastic rocks ∼10 km southeast of Damxung are exposed as structural windows in the footwall of a thrust fault (the Damxung thrust) that carries Paleozoic strata in the hanging wall. To the north of Damxung in the southern part of the northern Nyainqentanglha Range (NNQTL), metaclastic rocks of previously inferred Paleozoic age are shown to range in depositional age from Late Cretaceous to Eocene. The metaclastic rocks regionally dip southward and are interpreted to have been structurally buried in the footwall of the Damxung thrust prior to being tectonized during late Cenozoic transtension. Along the northern flank of the NNQTL, Lower Eocene syncontractional redbeds were deposited in a triangle zone structural setting. All detrital zircon samples of Cretaceous–Eocene strata in the Damxung area include Early Cretaceous grains that were likely sourced from the Gangdese arc to the south. We suggest that the that newly recognized Late Cretaceous to Early Eocene (meta)clastic deposits and thrust faults represent the frontal and youngest part of a northward directed and propagating Gangdese retroarc thrust belt and foreland basin system that led to significant crustal thickening and elevation gain in southern Tibet prior to India-Asian collision.  相似文献   

9.
Marine turbidites, tuffs, black mudstones and conglomerates of the Cambro-Ordovician Clew Bay Group, were deposited in the E–W elongate transtensional Clew Bay Graben that is centred on Clew Bay, NW Ireland. The group is characterized by extensive sedimentary deformation and mass movement on slides; olistostromes, autoclastic breccias and course proximal turbidites are interbedded with apparently less disturbed but often overturned sediments. The Clew Bay Group lies structurally above serpentinized dunite/harzburgite breccias, schistose carbonate peridotites, and other basic and ultrabasic igneous rocks that have ophiolitic geochemical affinities; the sediments may have been in part deposited upon oceanic crust. Ophiolites and sediments that now rest on the Clew Bay Thrust abut Silurian shallow water strata in which the main tectonothermal history, associated with sinistral transcurrent faulting along the thrust zone, is dated at about 410 Ma. The sole thrust dips northward and coalesces with a major deep structure along the Fair Head-Clew Bay Line (FCL) that is the western continuation of the Highland Border Fault of Scotland. Blueschist relics in the Dalradian immediately to the north of the FCL indicate that subduction was active early in the history of the late Cambrian–early Ordovician Grampian orogeny. The Clew Bay Thrust was a sinistral, transpressional shear zone late in its history, but it probably originated as an obduction complex. The Clew Bay Group cannot be traced into sedimentary, metamorphic or structural continuity with the adjacent Dalradian to the north or Ordovician and Silurian rocks in the South Mayo Trough to the south. It should be considered as a distinct terrane (Clew bay Terrane) or a subterrane of Highland Border-type rocks along the southern margin of the Grampian Terrane.  相似文献   

10.
Cenozoic sedimentary deposits in central-southern Ningxia province, NW China are an important record of Tertiary tectonic events along the evolving Qinghai–Tibetan Plateau’s northeast margin. Shortly after the onset of the Indo-Eurasia collision to the south, a thrust belt and adjoining foreland basin began to form during 40–30 Ma. The Eocene Sikouzi Formation developed in a distal setting to this basin, in normal fault-bound basins that may have formed in a forebulge setting. Subsequent deposition of the Oligocene Qingshuiying Formation occurred during a phase of apparently less intense tectonism and the previous underfilled foreland basin became overfilled. During the Early Miocene, contractional deformation was mainly distributed to the west of the Liupan Shan. This resulted in deformation of the Qingshuiying Formation as indicated by an unconformity with the overlying Miocene Hongliugou Formation. The unconformity occurs proximal to the Haiyuan Fault suggesting that the Haiyuan Fault may have begun movement in the Early Miocene. In the Late Miocene, thrusting occurred west of the southern Helan Shan and an unconformity developed between the Hongliugou and Qingshuiying Formations proximal to the the Cha-Gu Fault. Relationships between the Miocene stratigraphy and major faults in the region imply that during the Late Miocene the deformation front of the Qinghai–Tibetan Plateau had migrated to the Cha-Gu Fault along the western Ordos Margin, and the Xiang Shan was uplifted. Central-southern Ningxia was then incorporated into the northeast propagating thrust wedge. The driving force for NE propagation of the thrust wedge was most likely pronounced uplift of the northeastern plateau at the same time. Analysis of the sedimentary record coupled with consideration of the topographic evolution of the region suggests that the evolving fold-and-thrust belt experienced both forward-breaking fold-and-thrust belt development, and out-of-sequence fault displacements as the thrust wedge evolved and the foreland basin became compartmentalised. The documented sedimentary facies and structural relationship also place constraints on the Miocene-Recent evolution of the Yellow River and its tributaries.  相似文献   

11.
藏北改则新生代早期逆冲推覆构造系统   总被引：2，自引：0，他引：2  
藏北改则及邻区新生代早期发育大型逆冲推覆构造系统,由不同方向的逆冲断层、不同时代的构造岩片、不同规模的飞来峰和构造窗、不同类型的褶皱构造组成。羌塘中部发育羌中薄皮推覆构造,石炭系板岩和二叠系白云质灰岩自北向南逆冲推覆于上白垩统与古近系红层之上,形成大型逆冲岩席和弧形逆冲断层,原地系统古近纪红层下伏三叠系—侏罗系海相烃源岩。羌塘南部发育南羌塘薄皮推覆构造,导致班公—怒江蛇绿岩、三叠系—侏罗系海相地层及侏罗纪混杂岩自北向南逆冲推覆于古近纪红层与下白垩统海相沉积岩层之上,形成三条蛇绿岩片带、大量飞来峰和厚度较大的构造片岩。中新世早期火山岩层和湖相沉积呈角度不整合覆盖逆冲断层、褶皱构造和逆冲岩席,不整合面上覆火山岩年龄为23.7～19.1Ma,指示中新世早期改则及邻区基本结束了强烈逆冲推覆构造运动。估算羌中逆冲推覆构造的推覆距离约100～115km,南羌塘逆冲推覆构造的推覆距离约82～110km;新生代早期改则逆冲推覆构造系统近南北方向逆冲推覆总距离为182～225km,对应地壳缩短率为(50.3±2.7)%。  相似文献   

12.
Tectonics and Topography of the Tibetan Plateau in Early Miocene   总被引：1，自引：0，他引：1  
Early Miocene stratigraphy, major structural systems, magmatic emplacement, volcanic eruption, vegetation change and paleo-elevation were analyzed for the Tibetan Plateau after regional geological mapping at a scale of 1:250,000 and related researches, revealing much more information for tectonic evolution and topographic change of the high plateau caused by Indian-Asian continental collision. Lacustrine deposits of dolostone, dolomite limestone, limestone, marl, sandstone and conglomerate of weak deformation formed extensively in the central Tibetan Plateau, indicating that vast lake complexes as large as 100,000–120,000 km2 existed in the central plateau during Early Miocene. Sporopollen assemblages contained in the lacustrine strata indicate the disappearance of most tropical-subtropical broad-leaved trees since Early Miocene and the flourishing of dark needleleaved trees during Early Miocene. Such vegetation changes adjusted for latitude and global climate variations demonstrate that the central Tibetan Plateau rose to ca. 4,000–4,500 m and the northeastern plateau uplifted to ca. 3,500–4,000 m before the Early Miocene. Intensive thrust and crustal thickening occurred in the areas surrounding central Tibetan Plateau in Early Miocene, formed Gangdise Thrust System(GTS) in the southern Lhasa block, Zedong-Renbu Thrust(ZRT) in the northern Himalaya block, Main Central Thrust(MCT) and Main Boundary Thrust(MBT) in the southern Himalaya block, and regional thrust systems in the Qaidam, Qilian, West Kunlun and Songpan-Ganzi blocks. Foreland basins formed in Early Miocene along major thrust systems, e.g. the Siwalik basin along MCT, Yalung-Zangbu Basin along GTS and ZRT, southwestern Tarim depression along West Kunlun Thrust, and large foreland basins along major thrust systems in the northeastern margin of the plateau. Intensive volcanic eruptions formed in the Qiangtang, Hoh-Xil and Kunlun blocks, porphyry granites and volcanic eruptions formed in the Nainqentanglha and Gangdise Mts., and leucogranites and granites formed in the Himalaya and Longmenshan Mts. in Early Miocene. The K2O weight percentages of Early Miocene magmatic rocks in the Gangdise and Himlayan Mts. are found to increase with distance from the MBT, indicating the genetic relationship between regional magmatism and subduction of Indian continental plate in Early Miocene.  相似文献   

13.
THE CENTRAL PAMIR—AN ALPINE COLLISION ZONE  相似文献   

14.
A succession of quartz-rich fluvial sandstones and siltstones derived from a mainly rhyolitic source and minor metamorphic rocks, located to the west, represent the first Upper Paleocene–Early Eocene deposits described in Chilean eastern central Patagonian Cordillera (46°45′S). This unit, exposed 25 km south of Chile Chico, south of lago General Carrera, is here defined as the Ligorio Márquez Formation. It overlies with an angular unconformity Lower Cretaceous shallow marine sedimentary rocks (Cerro Colorado Formation) and subaerial tuffs that have yielded K–Ar dates of 128, 125 and 123 Ma (Flamencos Tuffs, of the Divisadero Group). The Ligorio Márquez Formation includes flora indicative of a tropical/subtropical climate, and its deposition took place during the initial part of the Late Paleocene–Early Eocene Cenozoic optimum. The underlying Lower Cretaceous units exhibit folding and faulting, implying a pre-Paleocene–Lower Eocene contractional tectonism. Overlying Oligocene–Miocene marine and continental facies in the same area exhibit thrusts and normal faults indicative of post-Lower Miocene contractional tectonism.  相似文献   

15.
Dextral-slip in the Nyainqentangiha region of Tibet resulted in oblique underthrusting and granite generation in the Early to Middle Miocene, but by the end of the epoch uplift and extensional faulting dominated. The east-west dextral-slip Gangdise fault system merges eastward into the northeast-trending, southeast-dipping Nyainqentangiha thrust system that swings eastward farther north into the dextral-slip North Damxung shear zone and Jiali faults. These faults were took shape by the Early Miocene, and the large Nyainqentangiha granitic batholith formed along the thrust system in 18.3-11.0 Ma as the western block drove under the eastern one. The dextral-slip movement ended at -11 Ma and the batholith rose, as marked by gravitational shearing at 8.6-8.3 Ma, and a new fault system developed. Northwest-trending dextral-slip faults formed to the northwest of the raisen batholith, whereas the northeast-trending South Damxung thrust faults with some sinistral-slip formed to the southeast. The latter are replaced farther to the east by the west-northwest-trending Lhunzhub thrust faults with dextral-slip. This relatively local uplift that left adjacent Eocene and Miocene deposits preserved was followed by a regional uplift and the initiation of a system of generally north-south grabens in the Late Miocene at -6.5 Ma. The regional uplift of the southern Tibetan Plateau thus appears to have occurred between 8.3 Ma and 6.5 Ma. The Gulu, Damxung-Yangbajain and Angan graben systems that pass east of the Nyainqentangiha Mountains are locally controlled by the earlier northeast-trending faults. These grabens dominate the subsequent tectonic movement and are still very active as northwest-trending dextral-slip faults northwest of the mountains. The Miocene is a time of great tectonic change that ushered in the modern tectonic regime.  相似文献   

16.
《Geodinamica Acta》2013,26(3-4):239-253
The precise ages of the sedimentary successions within two prominent NE-SW-trending basins, the Gördes Basin and the Selendi Basin, are critical to an understanding of the Neogene evolutionary setting of western Turkey and associated calc-alkaline magmatism. Early radiometric dating was not always sufficiently precise to resolve alternative interpretations. During this study, high-precision Ar40-Ar39 radiometric ages were determined on single crystals of biotite and sanidine from silicic tuffs and associated intrusive rocks. Finegrained tuffaceous sediments near the top of the sedimentary succession in the Selendi Basin gave ages of 18.89 ± 0.58 Ma to 16.42 ± 0.09 Ma. Coarser-grained tuffaceous sediments near the top of the equivalent sedimentary succession in the Gördes Basin to the NW yielded ages of 18.78 ± 0.3 Ma to 17.04 ± 0.35 Ma. Associated intrusive rocks were dated at 20.86 ± 0.08 Ma to 17.62 ± 0.07 Ma. An andesitic body on the northern margin of the Gediz (Ala?ehir) Graben further south gave ages of 16.08 ± 10.91 to 14.65 ± 0.06 Ma.

Combined with published radiometric age data, these new results confirm an Early Miocene age for the clastic sedimentary fills of the Gördes and Selendi basins. The results from the Gediz Graben are consistent with its formation in Early Miocene time, earlier than the Late Miocene or Plio-Quaternary ages suggested in some interpretations.  相似文献   

17.
The main exhumation of the Menderes massif, western Turkey, occurred along an originally N‐dipping Datça–Kale main breakaway fault that controlled depositions in the Kale and the Gökova basins during the Oligocene – Early Miocene interval. The isostatically controlled upward bending of the main breakaway fault brings the lower plate rocks to the surface. In the Early Miocene, E–W‐trending N‐ and S‐dipping graben‐bounding faults fragmented the exhumed, dome‐shaped massif. The development of half grabens by rolling master fault hinges has allowed further exhumation of the central Menderes massif. After the Pliocene, high‐angle normal faults cut all of the previous structures. This model suggests that the Menderes massif is a single large metamorphic core complex that has experienced a two‐stage exhumation process.  相似文献   

18.
The Zuccale fault is a gently east‐dipping normal fault exposed on Elba. Its displacement of 7–8 km occurred from the mid‐Miocene to the Early Pliocene and the fault has been exhumed from a depth of 3–6 km. A complex hydrofracture system exposed in the footwall block consists of three orthogonal vein sets: two vertical sets trending N–S and E–W and one sub‐horizontal. The veins show a crack‐and‐seal texture and mutually cross‐cut each other. Throughout the period when the Zuccale fault was active, the regional stress field was extensional with the minimum principal stress oriented E–W, consistent only with the N–S trending set of vertical hydrofractures. We attribute the three sets of orthogonal fractures beneath the low‐permeability phyllosilicate‐rich fault core to switches in the minimum compressive stress direction induced by cyclic build‐up and release of overpressure.  相似文献   

19.
Abstract

Field studies on the Neogene successions in south of ?zmir reveal that subsequent Neogene continental basins were developed in the region. Initially a vast lake basin was formed during the early-Middle Miocene period. The lacustrine sediments underwent an approximately N-S shortening deformation to the end of Middle Miocene. A small portion of the basin fill was later trapped within the N-S-trending, fault-bounded graben basin, the Çubukluda? graben, opened during the Late Miocene. Oblique-slip normal faults with minor sinistral displacement are formed possibly under N–S extensional regime, and controlled the sediment deposition. Following this the region suffered a phase of denudation which produced a regionwide erosional surface suggesting that the extension interrupted to the end of Late Miocene–Early Pliocene period. After this event the E–W-trending major grabens and horsts of western Anatolia began to form. The graben bounding faults cut across the Upper Miocene–Pliocene lacustrine sediments and fragmented the erosional surface. The Çubukluda? graben began to work as a cross garden between the E–W grabens, since that period. © 2001 Éditions scientifiques et médicales Elsevier SAS  相似文献   

20.
The northern Austral basin from Patagonia is characterized by an Early Cretaceous (Barremian–Albian) coarse-grained regressive sequence. These littoral to continental deposits conform a 150 km long basin cropping out along the Southern Patagonian Andes between 47 and 48°S. The basin fill consist of basal deltaic sandstones with interbedded shales and limestones from the Río Belgrano Formation, topped by up to 350 m of fluvial conglomerates and reworked tuffs of the Río Tarde and Kachaike formations. This continental depocenter represent a major geodynamic and paleoenviromental change from the underling marine Río Mayer Formation. In this study we analyze the tectonic setting and provenance during deposition of the coarse-grained sequence using sedimentary petrography of 37 thin sections in four stratigraphic profiles covering the northern basin. Our dataset indicates mainly a recycled orogenic sandstones provenance, in agreement with potential surrounding basement sources.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号