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1.
The Xunhua, Guide and Tongren intermontane basin system in the NE Tibetan Plateau, situated near the Xining basin to the N and the Linxia basin to the E, is bounded by thrust fault‐controlled ranges. These include to the N, the Riyue Shan, Laji Shan and Jishi Shan ranges, and to the S the northern West Qinling Shan (NWQ). An integrated study of the structural geology, sedimentology and provenance of the Cenozoic Xunhua and Guide basins provides a detailed record of the growth of the NE Tibetan Plateau since the early Eocene. The Xining Group (ca. 52–21 Ma) is interpreted as consisting of unified foreland basin deposits which were controlled by the bounding thrust belt of the NWQ. The Xunhua, Guide and Xining subbasins were interconnected prior to later uplift and damming by the Laji Shan and Jishi Shan ranges. Their sediment source, the NWQ, is constrained by strong unidirectional paleocurrent trends towards the N, a northward fining lithology, distinct and recognizable clast types and detrital zircon ages. Collectively, formation of this mountain–basin system indicates that the Tibetan Plateau expanded into the NWQ at a time roughly coinciding with Eocene to earliest Miocene continental collision between India and Eurasia. The Guide Group (ca. 21–1.8 Ma) is inferred to have been deposited in the separate Xunhua, Guide and Tongren broken foreland basins. Each basin was filled by locally sourced alluvial fans, braided streams and deltaic‐lacustrine systems. Structural, paleogeographic, paleocurrent and provenance data indicate that thrust faulting in the NWQ stepped northward to the Laji Shan from ca. 21 to 16 Ma. This northward shift was accompanied by E–W shortening related to nearly N–S‐striking thrust faulting in Jishi Shan after 11–13 Ma. A lower Pleistocene conglomerate (1.8–1.7 Ma) was deposited by a through‐flowing river system in the overfilled and connected Guide and Xunhua basins following the termination of thrust activity. All of the basin–mountain zones developed along the Tibetan Plateau's NE margin since Indian–Tibetan continental collision may have been driven by collision‐induced basal drag of old slab remnants in the manner of N‐dipping and flat‐slab subduction, and their subsequent sinking into the deep mantle.  相似文献   

2.
Magnetostratigraphy of sedimentary rock deposited in the Chaka basin (north‐eastern Tibetan Plateau) indicates a late Miocene onset of basin formation and subsequent development of the adjacent Qinghai Nan Shan. Sedimentation in the basin initiated at ～11 Ma. In the lower part of the basin fill, a coarsening‐upward sequence starting at ～9 Ma, as well as rapid sedimentation rates, and northward paleocurrents, are consistent with continued growth of the Ela Shan to the south. In the upper section, several lines of evidence suggest that thrust faulting and topographic development of the Qinghai Nan Shan began at ～6.1 Ma. Paleocurrent indicators, preserved in the basin in the proximal footwall of the Qinghai Nan Shan, show a change from northward to southward flow between 6.5 and 3.8 Ma. At the same location, sediment derived from the Qinghai Nan Shan appears at 6.1 Ma. Finally, the initiation of progressively shallowing dips observed in deformed basin strata and a change to pebbly, fluvial deposits at 6.1 Ma provide a minimum age for the onset of slip on the thrust fault that dips north‐east beneath the Qinghai Nan Shan. We interpret a decrease in sediment accumulation rates since ～6 Ma to indicate a reduction in Chaka basin accommodation space due to active faulting and folding along the Qinghai Nan Shan and incorporation of the basin into the wedge‐top depozone. Declination anomalies indicate the beginning of counter‐clockwise rotation since 6.1 Ma, which we associate with local deformation, not regional block rotation. The emergence of the Qinghai Nan Shan near the end of the Miocene Epoch partitioned the once contiguous Chaka‐Gonghe and Qinghai basin complex. In a regional framework, our study adds to a growing body of evidence that points to widespread initiation and/or reactivation of fault networks during the late Miocene across the north‐eastern Tibetan Plateau.  相似文献   

3.
《Basin Research》2017,29(Z1):131-155
Intermontane basins are illuminating stratigraphic archives of uplift, denudation and environmental conditions within the heart of actively growing mountain ranges. Commonly, however, it is difficult to determine from the sedimentary record of an individual basin whether basin formation, aggradation and dissection were controlled primarily by climatic, tectonic or lithological changes and whether these drivers were local or regional in nature. By comparing the onset of deposition, sediment‐accumulation rates, incision, deformation, changes in fluvial connectivity and sediment provenance in two interrelated intermontane basins, we can identify diverse controls on basin evolution. Here, we focus on the Casa Grande basin and the adjacent Humahuaca basin along the eastern margin of the Puna Plateau in northwest Argentina. Underpinning this analysis is the robust temporal framework provided by U‐Pb geochronology of multiple volcanic ashes and our new magnetostratigraphical record in the Humahuaca basin. Between 3.8 and 0.8 Ma, ~120 m of fluvial and lacustrine sediments accumulated in the Casa Grande basin as the rate of uplift of the Sierra Alta, the bounding range to its east, outpaced fluvial incision by the Río Yacoraite, which presently flows eastward across the range into the Humahuaca basin. Detrital zircon provenance analysis indicates a progressive loss of fluvial connectivity from the Casa Grande basin to the downstream Humahuaca basin between 3 and 2.1 Ma, resulting in the isolation of the Casa Grande basin from 2.1 Ma to <1.7 Ma. This episode of basin isolation is attributed to aridification due to the uplift of the ranges to the east. Enhanced aridity decreased sediment supply to the Casa Grande basin to the point that aggradation could no longer keep pace with the rate of the surface uplift at the outlet of the basin. Synchronous events in the Casa Grande and Humahuaca basins suggest that both the initial onset of deposition above unconformities at ~3.8 Ma and the re‐establishment of fluvial connectivity at ~0.8 Ma were controlled by climatic and/or tectonic changes affecting both basins. Reintegration of the fluvial network allowed subsequent incision in the Humahuaca basin to propagate upstream into the Casa Grande basin.  相似文献   

4.
Lower Cretaceous early syn‐rift facies along the eastern flank of the Eastern Cordillera of Colombia, their provenance, and structural context, reveal the complex interactions between Cretaceous extension, spatio‐temporal trends in associated sedimentation, and subsequent inversion of the Cretaceous Guatiquía paleo‐rift. South of 4°30′N lat, early syn‐rift alluvial sequences in former extensional footwall areas were contemporaneous with fan‐delta deposits in shallow marine environments in adjacent hanging‐wall areas. In general, footwall erosion was more pronounced in the southern part of the paleorift. In contrast, early syn‐rift sequences in former footwall areas in the northern rift sectors mainly comprise shallow marine supratidal sabkha to intertidal strata, whereas hanging‐wall units display rapid transitions to open‐sea shales. In comparison with the southern paleo‐rift sector, fan‐delta deposits in the north are scarce, and provenance suggests negligible footwall erosion. The southern graben segment had longer, and less numerous normal faults, whereas the northern graben segment was characterized by shorter, rectilinear faults. To the east, the graben system was bounded by major basin‐margin faults with protracted activity and greater throw as compared with intrabasinal faults to the west. Intrabasinal structures grew through segment linkage and probably interacted kinematically with basin‐margin faults. Basin‐margin faults constitute a coherent fault system that was conditioned by pre‐existing basement fabrics. Structural mapping, analysis of present‐day topography, and balanced cross sections indicate that positive inversion of extensional structures was focused along basin‐bounding faults, whereas intrabasinal faults remained unaffected and were passively transported by motion along the basin‐bounding faults. Thus, zones of maximum subsidence in extension accommodated maximum elevation in contraction, and former topographic highs remained as elevated areas. This documents the role of basin‐bounding faults as multiphased, long‐lived features conditioned by basement discontinuities. Inversion of basin‐bounding faults was more efficient in the southern than in the northern graben segment, possibly documenting the inheritance and pivotal role of fault‐displacement gradients. Our observations highlight similarities between inversion features in orogenic belts and intra‐plate basins, emphasizing the importance of the observed phenomena as predictive tools in the spatiotemporal analysis of inversion histories in orogens, as well as in hydrocarbon and mineral deposits exploration.  相似文献   

5.
The Celtic Sea basins lie on the continental shelf between Ireland and northwest France and consist of a series of ENE–WSW trending elongate basins that extend from St George’s Channel Basin in the east to the Fastnet Basin in the west. The basins, which contain Triassic to Neogene stratigraphic sequences, evolved through a complex geological history that includes multiple Mesozoic rift stages and later Cenozoic inversion. The Mizen Basin represents the NW termination of the Celtic Sea basins and consists of two NE–SW-trending half-grabens developed as a result of the reactivation of Palaeozoic (Caledonian, Lower Carboniferous and Variscan) faults. The faults bounding the Mizen Basin were active as normal faults from Early Triassic to Late Cretaceous times. Most of the fault displacement took place during Berriasian to Hauterivian (Early Cretaceous) times, with a NW–SE direction of extension. A later phase of Aptian to Cenomanian (Early to Late Cretaceous) N–S-oriented extension gave rise to E–W-striking minor normal faults and reactivation of the pre-existing basin bounding faults that propagated upwards as left-stepping arrays of segmented normal faults. In common with most of the Celtic Sea basins, the Mizen Basin experienced a period of major erosion, attributed to tectonic uplift, during the Paleocene. Approximately N–S Alpine regional compression-causing basin inversion is dated as Middle Eocene to Miocene by a well-preserved syn-inversion stratigraphy. Reverse reactivation of the basin bounding faults was broadly synchronous with the formation of a set of near-orthogonal NW–SE dextral strike-slip faults so that compression was partitioned onto two fault sets, the geometrical configuration of which is partly inherited from Palaeozoic basement structure. The segmented character of the fault forming the southern boundary of the Mizen Basin was preserved during Alpine inversion so that Cenozoic reverse displacement distribution on syn-inversion horizons mirrors the earlier extensional displacements. Segmentation of normal faults therefore controls the geometry and location of inversion structures, including inversion anticlines and the back rotation of earlier relay ramps.  相似文献   

6.
The uplift and associated exhumation of the Tibetan Plateau has been widely considered a key control of Cenozoic global cooling. The south-central parts of this plateau experienced rapid exhumation during the Cretaceous–Palaeocene periods. When and how the northern part was exhumed, however, remains controversial. The Hoh Xil Basin (HXB) is the largest late Cretaceous–Cenozoic sedimentary basin in the northern part, and it preserves the archives of the exhumation history. We present detrital apatite and zircon (U-Th)/He data from late Cretaceous–Cenozoic sedimentary rocks of the western and eastern HXB. These data, combined with regional geological constraints and interpreted with inverse and forward model of sediment deposition and burial reheating, suggest that the occurrence of ca. 4–2.7 km and ca. 4–2.3 km of vertical exhumation initiated at ca. 30–25 Ma and 40–35 Ma in the eastern and western HXB respectively. The initial differential exhumation of the eastern HXB and the western HXB might be controlled by the oblique subduction of the Qaidam block beneath the HXB. The initial exhumation timing in the northern Tibetan Plateau is younger than that in the south-central parts. This reveals an episodic exhumation of the Tibetan Plateau compared to models of synchronous Miocene exhumation of the entire plateau and the early Eocene exhumation of the northern Tibetan Plateau shortly after the India–Asia collision. One possible mechanism to account for outward growth is crustal shortening. A simple model of uplift and exhumation would predict a maximum of 0.8 km of surface uplift after upper crustal shortening during 30–27 Ma, which is insufficient to explain the high elevations currently observed. One way to increase elevation without changing exhumation rates and to decouple uplift from upper crustal shortening is through the combined effects of continental subduction, mantle lithosphere removal and magmatic inflation.  相似文献   

7.
《Basin Research》2018,30(4):587-612
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8.
The upper Campanian–Lower Eocene synorogenic sedimentary wedge of the Ranchería Basin was deposited in an intraplate basin resting on a tilted continental crustal block that was deformed by collision and subsequent subduction of the Caribbean Plate. Upper Cretaceous–Lower Eocene strata rest unconformably upon Jurassic igneous rocks of the Santa Marta Massif, with no major thrust faults separating the Santa Marta Massif from the Ranchería Basin. The upper Campanian–Lower Eocene succession includes, from base to top: foraminifera‐rich calcareous mudstone, mixed carbonate–siliciclastic strata and mudstone, coal and immature fluvial sandstone beds. Diachronous collision and eastward tilting of the plate margin (Santa Marta Massif and Central Cordillera) favoured the generation of accommodation space in a continuous intraplate basin (Ranchería, Cesar and western Maracaibo) during the Maastrichtian to Late Palaeocene. Terrigenous detritus from the distal colliding margin filled the western segments of the continuous intraplate basin (Ranchería and Cesar Basins); in the Late Paleocene, continental depositional systems migrated eastwards as far as the western Maracaibo Basin. In Early Eocene time, reactivation of former extensional structures fragmented the intraplate basin into the Ranchería‐Cesar Basins to the west, and the western Maracaibo Basin and Palmar High to the East. This scenario of continent–oceanic arc collision, crustal‐scale tilting, intraplate basin generation and fault reactivation may apply for Upper Cretaceous–Palaeogene syntectonic basins in western Colombia and Ecuador, and should be considered in other settings where arc–continent collision is followed by subduction.  相似文献   

9.
Located at the southern edge of the eastern Himalayan syntaxis, the Central Myanmar Basin (CMB) is divided into several Tertiary sub‐basins that have been almost continuously filled since the Indo‐Asia collision. They are currently drained by the Irrawaddy River, which flows down the eastern Tibetan Plateau and the Sino‐Burman Ranges. Tracing sediment provenance from the CMB is thus critical for reconstructing the past denudation of the Himalayan‐Tibetan orogen; it is especially relevant since a popular drainage scenario involves the capture of the Tsangpo drainage system in Tibet by a precursor to the Irrawaddy River. Here, we document the provenance of sediment samples from the Minbu Sub‐Basin at the southern edge of the CMB, which is traversed by the modern stream of the Irrawaddy River. Samples ranging in age from middle Eocene to Pleistocene were investigated using Nd isotopes, trace element geochemistry and sandstone modal compositions. Our data provide no evidence of a dramatic provenance shift; however, sandstone petrography, trace element ratios and isotopic values display long‐term trends indicating a gradual decrease of the volcanic input and its replacement by a dominant supply from the Burmese basement. These trends are interpreted to reflect the progressive denudation of the Andean‐type volcanic arc that extended onto the Burmese margin, along the flank of the modern Sino‐Burman Ranges, where most of the post‐collisional deformation of central Myanmar is located. Though our results do not exclude an ephemeral or diluted contribution from a past Tsangpo‐Irrawaddy connection, sedimentation rates suggest that this hypothesis is unlikely before the development of a stable Tsangpo‐Brahmaputra River in the Miocene. These results thus suggest that the central Myanmar drainage basin has remained restricted to the Sino‐Burman Ranges since the beginning of the India‐Asia collision.  相似文献   

10.
We describe the tectono‐sedimentary evolution of a Middle Jurassic, rift‐related supra‐detachment basin of the ancient Alpine Tethys margin exposed in the Central Alps (SE Switzerland). Based on pre‐Alpine restoration, we demonstrate that the rift basin developed over a detachment system that is traced over more than 40 km from thinned continental crust to exhumed mantle. The detachment faults are overlain by extensional allochthons consisting of upper crustal rocks and pre‐rift sediments up to several kilometres long and several hundreds of metres thick, compartmentalizing the distal margin into sub‐basins. We mapped and restored one of these sub‐basins, the Samedan Basin. It consists of a V‐shape geometry in map view, which is confined by extensional allochthons and floored by a detachment fault. It can be restored over a minimum distance of 11 km along and about 4 km perpendicular to the basin axis. Its sedimentary infill can be subdivided into basal (initial), intermediate (widening) and top (post‐tectonic) facies tracts. These tracts document (1) formation of the basin initially bounded by high‐angle faults and developing into low‐angle detachment faults, (2) widening of the basin and (3) migration of deformation further outboard. The basal facies tract is made of locally derived, poorly sorted gravity flow deposits that show a progressive change from hangingwall to footwall‐derived lithologies. Upsection the sediments develop into turbidity current deposits that show retrogradation (intermediate facies tract) and starvation of the sedimentary system (post‐tectonic facies tract). On the scale of the distal margin, the syn‐tectonic record documents a thinning‐ and fining‐upward sequence related to the back stepping of the tectonically derived sediment source, progressive starvation of the sedimentary system and migration of deformation resulting in exhumation and progressive delamination of the thinned crust during final rifting. This study provides valuable insights into the tectono‐sedimentary evolution and stratigraphic architecture of a supra‐detachment basin formed over hyper‐extended crust.  相似文献   

11.
The Cenozoic geodynamics of the north‐eastern Mediterranean Basin have been dominated by the subduction of the African Plate under Eurasia. A trench‐parallel crustal‐scale thrust system (Misis–Kyrenia Thrust System) dissects the southern margin of the overriding plate and forms the structural grain and surface expression of northern Cyprus. Late Eocene to Miocene flysch of the Kythrea (De?irmenlik) Group is exposed throughout northern Cyprus, both at the hanging‐wall and foot‐wall of the thrust system, permitting access to an extensive Cenozoic sedimentary record of the basin. We report the results of a combined examination of detrital zircon and rutile U–Pb geochronology (572 concordant ages), coupled with Th/U ratios, Hf isotopic data and quantitative assessment of grain morphology of detrital zircon from four formations (5 samples) from the Kythrea flysch. These data provide a line of independent evidence for the existence of two different sediment transportation systems that discharged detritus into the basin between the late Eocene and late Miocene. Unique characteristics of each transport system are defined and a sediment unmixing calculation is demonstrated and explained. The first system transported almost exclusively North Gondwana‐type, Precambrian‐aged detrital zircon sourced from siliciclastic rock units in southern Anatolia. A different drainage system is revealed by the middle to late Miocene flysch sequence that is dominated by Late Cretaceous–Cenozoic‐aged detrital zircon, whose age range is consistent with the magmatic episodicity of southeast Anatolia, along the Arabia–Eurasia suture zone. Deposition of these late Miocene strata took place thereupon closure of the Tethyan Seaway and African–Eurasian faunal exchange, and overlap in time with a pronounced uplift of eastern Anatolia. Our analytical data indicate the onset of prominent suture‐parallel sediment transport from the collision zone of south‐eastern Anatolia into the Kyrenia Range of northern Cyprus, marking the drainage response to the continental collision between Arabia and Eurasia.  相似文献   

12.
The Colombian accretionary complex forms the active convergent margin of the North Andes block of South America beneath which the east Panama Basin of the Nazca plate is subducted at a rate of 50–64 km Myr?1. Multichannel seismic reflection data, collected as part of RRS Charles Darwin cruise CD40, image a series of well-developed forearc basins along the length of the margin, bounded on their oceanward side by an active accretionary complex and on their landward side by oceanward-dipping continental basement. Sedimentary sequences within the forearc basins indicate successive landward migration of the basin depocentre as the structural high bounding its oceanward edge is forced upward and landward by continued growth of the accretionary complex. Uplift beneath the oceanward side of the basins has resulted in progressive landward rotation of the older sedimentary sequences. Prominent seismic reflectors across the basins show a complex onlap–offlap relationship between successive sequences that reflects the interplay between tectonic uplift, sediment supply, differential sediment compaction and basement subsidence due to loading. A numerical model has been devised to investigate how Miocene to Recent forearc basin stratigraphy is controlled by progressive growth of the accretionary complex resulting in elevation of the outer-arc high and landward motion of the rear of the complex up the seaward-dipping backstop formed by the leading edge of the continental lithosphere. The effects of sediment accretion are modelled by treating the accretionary complex as a doubly vergent, noncohesive Coulomb wedge, where forces exerted by the proto- and retro-wedges must be balanced for the system to be in equilibrium. The model generates synthetic basin-fill architecture over a series of steps, each of which represents the deposition of individual sedimentary sequences and their subsequent deformation due to wedge growth. The model accounts for differential sediment compaction and the flexural response of the underlying lithosphere to changes in load distribution over time. Forearc basin evolution is simulated for various rates of sediment supply to the forearc and accretionary complex growth until the synthetic basin-fill geometry matches the observed geometry. The model enables either the rate of accretionary wedge growth or the rate of sediment supply to the forearc basin to be established. The technique is generally applicable to those convergent margins with forearc basins that have developed between an actively accreting wedge and a seaward-dipping backstop. Other examples include Peru, S. Chile, Sumatra and Barbados.  相似文献   

13.
P. Haughton 《Basin Research》2001,13(2):117-139
ABSTRACT The mechanisms driving subsidence in late orogenic basins are often not easily resolved on account of later fault reactivation and a rapidly changing stress field. Contained turbidites in such basins provide a unique opportunity of monitoring sea bed deformation and evolving bathymetry and hence patterns of subsidence during basin filling. A variety of interpretations have been proposed to explain subsidence in Neogene basins in SE Spain, including extensional, strike‐slip and thrust top mechanisms. Ponded turbidite sheets on the floor of the Neogene Sorbas Basin (SE Spain) were deposited by sand‐bearing currents which ran into enclosed bathymetric deeps where they underwent rapid suspension collapse. The structure and distribution of these sheets (and the thick mudstone caps which overlie them) act as a proxy for the containing sea bed bathymetry at the time of deposition. An analysis of the sheet architecture helps identify a trough‐axial zone of syndepositional faulting and reveals a westwards stepping of the ponding depocentre with time. Fault breaks at the sea bed influenced the position of flow arrest and the distribution of sandstone beds on the basin floor. Westward stepping of the deeper bathymetry was episodic and probably controlled by transverse faults. Re‐locations of the depocentre were accompanied by the destabilization of carbonate sand stores on the margins of the basin, resulting in the repeated emplacement of large‐volume carbonate megabeds and calciturbidites. The fill to the Sorbas Basin was shingled by the onset of compression in the east attributed to transfer of slip between intersecting strike‐slip fault strands. A sinistral fault (a splay of the Carboneras Fault System) propagated through the evolving basin fill from the east as the eastern part of the basin became inverted and the locus of subsidence migrated into the Tabernas area 20 km area to the west. The sedimentological analysis of the basin fill helps see through a late dextral overprint which ultimately juxtaposed basement rocks to the south against the inverted and upended basin, along a late slip‐modified unconformity. Conventional palaeostress analysis of fractures along the basin margin fails to see past this late dextral shearing event. Basin migration parallel to the E–W‐orientated basin axis, slip‐reversal (sinistral to dextral) and the active involvement of strike‐slip faults are now identified as important aspects of the evolution of the Sorbas Basin during the latestTortonian.  相似文献   

14.
The Miocene Waitemata Basin was deposited on a moving base provided by the Northland Allochthon, which was emplaced in the Late Oligocene, as a new convergent plate boundary was established in northern New Zealand. The basin experienced complex interaction between tectonic and gravity‐driven shallow deformation. Spectacular examples of the resulting structures exposed on eastern Whangaparaoa Peninsula 50 km north of Auckland provide a world‐class example of weak rock deformation, the neglected domain between soft‐sediment and hard rock deformation. Quartz‐poor turbidite sequences display a protracted sequence of deformations: D1, synsedimentary slumping; D2, large scale deeper‐seated sliding and extensional low‐angle shearing, associated with generation of boudinage and broken formation; D3, thrusting and folding, indicating transport mostly to the SE; D4, thrusting and folding in the opposite direction; D5, further folding, including sinistral shear; D6, steep faults. The deformation sequence suggests continuous or intermittent southeastward transport of units with increasing sedimentary and structural burial. By phase D3, the rocks had passed from the soft‐sediment state to low levels of consolidation. However, with a compressive strength of ～5 MPa they are weak rocks even today. Such weak‐rock deformation must be important in other sedimentary basins, especially those associated with active convergent plate boundaries and with immature source areas for their sediments.  相似文献   

15.
The continuous Cenozoic strata in the Xining Basin record the growth and evolution of the northeastern Qinghai–Tibetan Plateau. Here, the mechanisms and evolution of the Xining Basin during the Cenozoic were investigated by studying the sedimentary facies of 22 Cenozoic sections across the basin and detrital zircon U‐Pb ages of three Cenozoic sections located in the eastern, central and western basin, respectively. In the Eocene (ca. 50–44 Ma), the India‐Eurasia Collision affected the northeastern Qinghai–Tibetan Plateau. The Central Qilian Block rotated clockwise by ca. 24° to form the Xining Basin. The Triassic flysch sediments surrounding the basin were the primary sources of sediment. Between ca. 44–40 Ma, the basin enlarged and deepened, and sedimentation was dominated by saline lake sediments. Between ca. 40–25.5 Ma, the Xining Basin began to shrink and dry, resulting in the deposition of saline pan and saline mudflat sediments in the basin. After ca. 20 Ma, the Laji Shan to the south of the Xining Basin was uplifted due to the northward compression of the Guide Basin to the south. Clasts that eroded from this range dominated the sediments as the basin evolved from a lacustrine environment into a fluvial system. The Xining Basin was an extensional basin in the Early Cenozoic, but changed into a compressive one during the Late Cenozoic, it was not a foreland basin either to the Kunlun Shan or to the western Qinling Shan in the whole Cenozoic. The formation and deformation of the Xining Basin are the direct responses of the India‐Eurasia Collision and the growth of the Qinghai‐Tibetan Plateau.  相似文献   

16.
A series of analogue models are used to demonstrate how the multistage development of the Mid‐Polish Trough (MPT) could have been influenced by oblique basement strike–slip faults. Based on reinterpretation of palaeothickness, facies maps and published syntheses of the basin development, the following successive stages in the Mesozoic history of the south eastern part of the MPT were simulated in the models: (1) Oblique extension of the NW segment of the MPT connected with sinistral movement along the Holy Cross Fault (HCF, Early Triassic–latest Early Jurassic). (2) Oblique extension of both NW and SE segment of the MPT, parallel to the HCF (latest Early and Middle Jurassic). (3) Oblique extension of the SE segment of the MPT and much lesser extension of its NW segment connected with dextral movement along the HCF (Early Oxfordian–latest Early Kimmeridgian). (4) Oblique extension of the SE segment of the MPT and much lesser extension of its NW segment connected with dextral movement along the Zawiercie Fault (ZF, latest Early Kimmeridgian–Early Albian). (5) Oblique inversion of the NW segment of the MPT connected with dextral movement along the HCF (Early Albian–latest Cretaceous). (6) Oblique inversion of the SE segment of the MPT along the W–E direction (latest Cretaceous–Palaeogene). The different sense of movements of these two basement strike–slip faults (HCF and ZF) resulted in distinct segmentation of the basin and its SW margin by successive systems of extensional en‐echelon faults. The overall structure of this margin is controlled by the interference of the border normal faults with the en‐echelon fault systems related to successive stages of movement along the oblique strike–slip faults. This type of en‐echelon fault system is absent in the opposite NE‐margin of the basin, which was not affected by oblique strike–slip faults. The NE‐margin of the basin is outlined by a typical, steep and distinctly marked rift margin fault zone, dominated by normal and dip–slip/strike–slip faults parallel to its axis. Within the more extended segment of the basin, extensive intra‐rift faults and relay ramps develop, which produce topographic highs running across the basin. The change in the extension direction to less oblique relative to the basin axis resulted in restructuring of the fault systems. This change caused shifting of the basin depocentre to this margin. Diachronous inversion of the different segments of the basin in connection with movement along one of the oblique basement strike–slip faults resulted in formation of a pull‐apart sub‐basin in the uninverted SE‐segment of the basin. The results of the analogue models presented here inspire an overall kinematic model for the southeastern segment of the MPT as they provide a good explanation of the observed structures and the changes in the facies and palaeothickness patterns.  相似文献   

17.
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 syncline 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.  相似文献   

18.
The Adana Basin of southern Turkey, located at the SE margin of the Central Anatolian Plateau in the vicinity of the Arabia‐Eurasia collision zone, is ideally suited to record Neogene and Quaternary topographic and tectonic changes in the easternmost Mediterranean realm. On the basis of our correlation of 34 seismic reflection profiles with corresponding exposed units along the margins of the Adana Basin, we identify and characterize the seismic facies that corresponds to the upper part of the Messinian Handere Formation (ca. 5.45 to 5.33 Ma), which consists mainly of fluvial conglomerates and marls. The seismic reflection profiles indicate that ca. 1100 km3 of the Handere Formation upper sub‐unit is distributed over ca. 3000 km2, reflecting local sedimentation rates of up to 12.5 mm year?1. This indicates a major increase in both sediment supply and subsidence rates at ca. 5.45 Ma. Our provenance analysis of the Handere Formation upper sub‐unit based on clast counting and palaeocurrent measurements reveals that most of the sediment is derived from the Taurus Mountains at the SE margin of the Central Anatolian Plateau and regions farther north. A comparison of these results with the composition of recent fluvial conglomerates and the present‐day drainage basins indicates major changes between late Messinian and present‐day source areas. We suggest that these changes in drainage patterns and lithological characteristics result from uplift and ensuing erosion of the SE margin of the plateau. We interpret the tectonic evolution of the southern flank of the Anatolian Plateau and the coeval subsidence and sedimentation in the Adana Basin to be related to deep lithospheric processes, particularly lithospheric delamination and slab break‐off.  相似文献   

19.
晚新生代以来,青藏高原北东向扩展,致使祁连山地区遭受了强烈的构造隆升,造就了祁连山地区复杂的构造格局和急剧变化的构造地貌,其典型水系流域地貌特征揭示了该地区的新构造活动和地貌演化过程。庄浪河流域位于祁连山东段,作为青藏高原北东向扩展的前缘地区,庄浪河流域的地貌参数对构造活动非常敏感,提取庄浪河流域的地貌信息,有助于揭示祁连山东段庄浪河流域地貌对构造活动的响应,及系统探讨该区地貌发育特征及其所蕴含的构造意义。庄浪河流域内及边缘发育有庄浪河断裂、天祝盆地南缘断裂、疙瘩沟隐伏断裂以及金强河-毛毛山-老虎山断裂。晚新生代以来,这些断裂仍在活动,并且控制着流域内的构造变形、山体隆升和河流水系地貌发育。本研究采用ALOS DEM 12.5 m数据,基于ArcGIS空间分析技术,通过高程条带剖面、河流坡降指标体系（K,SL,SL/K）和Hack剖面、面积-高程积分值（HI）和积分曲线（HC）等方法,对庄浪河流域地貌特征进行了初步分析。结果表明,庄浪河地区地形起伏由北西向南东递减,构造活动存在东西分异的规律;庄浪河流域内部K值、SL、SL/K、HI值西侧高于东侧,Hack剖面西侧相比东侧上凸更明显;H...  相似文献   

20.
Unravelling early Cenozoic basin development in northern Tibetan Plateau remains crucial to understanding continental deformation mechanisms and to assessing models of plateau growth. We target coarse-grained red beds from the Cenozoic basal Lulehe Formation in the Qaidam basin by combining conglomerate clast compositions, paleocurrent determinations, sandstone petrography, heavy mineral analysis and detrital zircon U–Pb geochronology to characterize sediment provenance and the relationship between deformation and deposition. The red beds are dominated by matrix-supported, poorly sorted clastic rocks, implying low compositional and textural maturity and short transport distances. Although most sandstones have high (meta)sedimentary lithic fragment contents and abundant heavy minerals of metamorphic origin (e.g., garnet, epidote and chlorite), spatiotemporal differences in detrital compositions are evident. Detrital zircon grains mainly have Phanerozoic ages (210–280 Ma and 390–480 Ma), but Proterozoic ages (750–1000 Ma, 1700–2000 Ma and 2300–2500 Ma) are also prominent in some samples. Analysed strata display dissimilar (including south-, north- and west-directed) paleocurrent orientations. These results demonstrate that the Cenozoic basal deposits were derived from localized, spatially diverse sources with small drainage networks. We advocate that initial sedimentary filling in the northern Qaidam basin was fed by parent-rocks from the North Qaidam-South Qilian belts and the pre-Cenozoic basement within the Qaidam terrane interior, rather than southern distant Eastern Kunlun regions. Seismic and drilling well stratigraphic data indicate the presence of paleohighs and syn-sedimentary reverse faults and noteworthy diversity in sediment thickness of the Lulehe Formation, revealing that the Qaidam terrane exhibited as several isolated depocenters, rather than a coherent basin, in the early stage of the Cenozoic deposition. We suggest the Cenozoic Qaidam basin to have developed in a contractional deformation regime, which supports models with synchronous deformation throughout most of Tibet shortly after the India-Eurasia collision.  相似文献   

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