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1.
为了研究松辽盆地白垩纪裂后期沉降的动力机制,以松辽盆地南部长岭、十屋凹陷为例,用回剥法和应变速率反演方法对研究区钻井和地层剖面资料进行了研究。结果表明：观测得到的裂后沉降和模拟预测的理论裂后沉降结果存在较大差异,异常沉降量达160~800 m;并且异常沉降经历了两次沉降高峰期,分别出现在裂后期的泉头组及嫩江组沉积时期,平均沉降速率最大值出现在泉头组沉积时期,达16 m/Ma,同期地壳应变速率也达到裂后期最大值,约为6 Ga-1。该异常沉降除受到裂后期基底断裂和盆地小型正断层活动的小部分影响外,可能主要受控于中生代晚期Izanagi俯冲板片在松辽盆地深部的下拽作用及其诱发的深部地幔流动,属动力沉降。 相似文献
2.
根据岩心观察、重矿物特征、单井岩性剖面及相关指数的综合研究,认为早-中侏罗世期间,库车坳陷东部主要接受南天山物源区提供的碎屑物,而塔北隆起提供的碎屑物则比较有限。根据下-中侏罗统碎屑岩中重矿物和碎屑组分的差异,进一步将各期物源区在东西方向上划分成4个物源补给亚区。此外,从下侏罗统阿合组、阳霞组到中侏罗统克孜勒努尔组,南天山物源区逐渐向南天山造山带的腹部扩展,反映夷平作用进一步加强,构造活动性相对比较稳定。 相似文献
3.
Zhong-Xian Zhao 《地学前缘(英文版)》2021,12(6):223-235
Deep hot mantle upwelling is widely revealed around the Qiongdongnan Basin on the northwestern South China Sea margin.However,when and how it influenced the hyper-extended basin is unclear.To resolve these issues,a detailed analysis of the Cenozoic time-varying residual subsidence derived by subtracting the predicted subsidence from the backstripped subsidence was performed along a new seismic reflection line in the western Qiongdongnan Basin.For the first time,a method is proposed to cal-culate the time-varying strain rates constrained by the faults growth rates,on basis of which,the pre-dicted basement subsidence is obtained with a basin-and lithosphere-scale coupled finite extension model,and the backstripped subsidence is accurately recovered with a modified technique of backstrip-ping to eliminate the effects of later episodes of rifting on earlier sediment thickness.Results show no residual subsidence in 45-28.4 Ma.But after 28.4 Ma,negative residual subsidence occurred,reached and remained ca.-1000 m during 23-11.6 Ma,and reduced dramatically after 11.6 Ma.In the syn-rift period(45-23 Ma),the residual subsidence is ca.-1000 m,however in the post-rift period(23-0 Ma),it is positive of ca.300 to 1300 m increasing southeastwards.These results suggest that the syn-rift sub-sidence deficit commenced at 28.4 Ma,while the post-rift excess subsidence occurred after 11.6 Ma.Combined with previous studies,it is inferred that the opposite residual subsidence in the syn-and post-rift periods with similar large wavelengths(＞102 km)and km-scale amplitudes are the results of transient dynamic topography induced by deep mantle upwelling beneath the central QDNB,which started to influence the basin at ca.28.4 Ma,continued into the Middle Miocene,and decayed at ca.11.6 Ma.The initial mantle upwelling with significant dynamic uplift had precipitated considerable con-tinental extension and faulting in the Late Oligocene(28.4-23 Ma).After ca.11.6 Ma,strong mantle upwelling probably occurred beneath the Leizhou-Hainan area to form vast basaltic lava flow. 相似文献
4.
《地学前缘(英文版)》2022,13(3):101377
Tectonic transition from a syn-rift stage to subsequent post-rift stage is an important mechanism in the evolution of extensional basins. The sedimentary infill records the crustal response to this process. We have obtained new detrital zircon U-Pb and Lu-Hf signatures from the Lower Cretaceous stratigraphic successions encompassing the commonly accepted syn- to post-rift transition boundary, the T4 unconformity, in the Songliao Basin, NE China. These constrain the Songliao Basin’s evolution from its center to distal margins, providing insights into the sediment provenance and dispersal pattern over the tectonic transition. Analysis of zircons from the syn-rift (the Shahezi and Yingcheng formations) and immediate post-rift (the Lower and Middle Denglouku Formation) stages reveals Phanerozoic age populations with positive ?Hf(t) values, which were derived from the proximal juvenile mantle-derived melt origin bedrocks of the Songliao Block. In contrast, the overlying samples from the Upper Denglouku Formation deposited in the subsequent post-rift stage contain exotic and ancient zircon populations with ages of 2.5 Ga & 1.8 Ga and complex hafnium signatures, characteristic of a mixed origin. These are interpreted to be transported from distant cratonic terranes via larger drainage networks. It is obvious that the sediment dispersal pattern switched from being a local and hydrologically closed “intraregional” pattern to a “transcontinental” pattern during the transition. The time lag between the development of the T4 unconformity and the drainage reorganization also ensures a distinguishable ～3 Myr (106103 Ma, Late Albian) transition period of regional extent. During this transition stage, syn-rift faulting was replaced by post-rift thermal subsidence, exhibiting a uniform sag configuration. Our new findings are important for understanding other continental rift basins during syn- to post-rift transition, which often demonstrates a complex interaction between the linkage and integration of sub-basins, and the reorganization of fluvial drainages and catchment systems. 相似文献
5.
湘东南汝城盆地为一早侏罗世—中侏罗世初期的陆相盆地。下侏罗统心田门组和高家田组主要为内陆湖泊—沼泽相碎屑岩沉积,夹有明显受地壳混染并具低钾高钠特征的板内拉斑玄武岩,表明早侏罗世汝城盆地为同造山上隆伸展裂陷盆地。中侏罗统千佛岩组与下伏高家田组为平行不整合接触关系。千佛岩组下部具类磨拉石沉积特征,上部局部含高家田组玄武质火山碎屑,地层呈西倾单斜式,盆地西缘为逆断裂所压覆等,表明中侏罗世初期汝城盆地为挤压收缩盆地,形成于造山构造环境。结合中生代地质构造发展框架及燕山早期晚阶段后造山花岗岩的大量发育等,认为湘东南及湘粤赣边区早侏罗世—中侏罗世初期属陆内同造山构造环境,中侏罗世早期—晚侏罗世为后造山构造环境。汝城盆地性质的确定对深入研究华南地区中生代构造演化具有重要的启示意义。 相似文献
6.
Petrography of Middle Jurassic to Early Cretaceous sandstones in the Kutch Basin,western India:Implications on provenance and basin evolution 总被引：1，自引：0，他引：1
This paper investigates the provenance of Middle Jurassic to Early Cretaceous sediments in the Kutch Basin, western India, on the basis of mineralogical investigations of sandstones composition(Quartz-Feldspar-Lithic(QFL)fragment), Zircon-Tourmaline-Rutile(ZTR) index, and mineral chemistry of heavy detrital minerals of the framework.The study also examines the compositional variation of the sandstone in relation to the evolution of the Kutch Basin, which originated as a rift basin during the Late Triassic and evolved into a passive margin basin by the end Cretaceous. This study analyzes sandstone samples of Jhumara, Jhuran and Bhuj Formations of Middle Jurassic,Upper Jurassic and Lower Cretaceous, respectively, in the Kutch Mainland. Sandstones record a compositional evolution from arkosic to subarkosic as the feldspar content decreases from 68% in the Jhumara Formation to 27%in the Bhuj Formation with intermediate values in the Jhuran Formation. The QFL modal composition indicates basement uplifted and transitional continental settings at source. Heavy mineral content of these sandstones reveals the occurrence of zircon, tourmaline, rutile, garnet, apatite, monazite and opaque minerals. Sub-rounded to well-rounded zircon grains indicate a polycyclic origin. ZTR indices for samples in Jhumara, Jhuran and Bhuj Formations are 25%, 30% and 50% respectively. Chemistry of opaque minerals reveals the occurrence of detrital varieties such as ilmenite, rutile, hematite/magnetite and pyrite, in a decreasing order of abundances. Chemistry of ilmenites in the Jhumara Formation reveals its derivation from dual felsic igneous and metabasic source, while those in Jhuran and Bhuj Formations indicate a metabasic derivation. Chemistry of garnet reveals predominantly Fe-rich(almandine) variety of metabasic origin. X-ray microscopic study provides the percentage of heavy minerals ranging from 3% to 5.26%. QFL detrital modes reflect the evolution of the basin from an active rift to a passive margin basin during the Mesozoic. Integration of results from QFL modal composition of the sandstones, heavy mineral analysis and mineral chemistry, suggests sediment supply from both northern and eastern highlands during the Middle Jurassic. The uplift along the Kutch Mainland Fault in the Early Cretaceous results in curtailment of sediment input from north. 相似文献
7.
Backstripping analysis has been carried out on five boreholes and one outcrop section of the Ecca Group in the Main Karoo Basin of South Africa to determine the sedimentation rate and subsidence history of the basin. The result shows that the rate of sedimentation in the Prince Albert, Whitehill, Collingham, Ripon and Fort Brown Formations range between 0.003–0.03, 0.02–0.05, 0.01–0.05, 0.03–0.22, and 0.15–0.025 mm year?1, respectively. The backstripped subsidence curves that are constructed by removing the effects of decompaction to the water column and sediment loads show subsidence rates decreasing with time, resembling the typical thermal subsidence curves of passive continental margins. Three major subsidence episodes characterized the Ecca Group, namely, (1) rapid subsidence in an extensional regime, (2) slow subsidence in the middle of basin development and (3) another rapid subsidence in a compressional regime. The aforementioned subsidence episodes show that the southeastern Karoo Basin was located on a passive continental margin, suggesting that the subsidence was initiated and mainly controlled by mechanical (gravitational loading) or tectonic events, with little contribution of thermal events. The average rate of tectonic subsidence in the Prince Albert, Whitehill, Collingham, Ripon and Fort Brown Formations are 63, 28, 25, 215 and 180 m Ma?1, respectively. It is also inferred that the southeastern Karoo Basin evolved from a passive continental margin into an Andean-type continental foreland basin; thus, portraying a completely evolved post-rift setting along the southeastern Gondwana margin. 相似文献
8.
对大兴安岭北部漠河盆地中侏罗统漠河组砂岩进行了碎屑锆石LA-ICP-MS U-Pb年龄测试,获得的碎屑锆石U-Pb年龄为1425~170 Ma,反映了中侏罗时期漠河盆地源区的复杂性。该时期漠河盆地物源主要有:中元古代变质火山岩,碎屑锆石年龄1425~1064 Ma;新元古代变质侵入岩,碎屑锆石年龄888~550 Ma;寒武—奥陶纪变质表壳岩与深成侵入岩,碎屑锆石年龄517~441 Ma;石炭—二叠纪侵入岩,碎屑锆石年龄327~252 Ma;三叠纪—中侏罗世侵入岩,碎屑锆石年龄250~170 Ma。这一测试数据与盆地现在南缘分布的地质体的时代基本对应,说明盆地的物源主要来自南部的中元古代—中侏罗世地质体,碎屑锆石中最小年龄为170 Ma,反映漠河组沉积下限不早于中侏罗世早期。这一成果对研究漠河盆地源区的物质组成、盆地沉积年代和油气成藏条件提供了新的素材。 相似文献
9.
《Journal of African Earth Sciences》1999,28(2):443-463
Sediments of the Ordovician to Devonian Sinakumbe Group (∼210 m thick) and overlying Upper Carboniferous to Lower Jurassic Karoo Supergroup (∼4.5 km thick) were deposited in the mid-Zambezi Rift Valley Basin, southern Zambia.The Sinakumbe-Karoo succession represents deposition in a extensional fault-controlled basin of half-graben type. The basin-fill succession incorporates two major fining-upward cycles that resulted from major tectonic events, one event beginning with Sinakumbe Group sedimentation, possibly as early as Ordovician times, and the other beginning with Upper Karoo Group sedimentation near the Permo-Triassic boundary. Minor tectonic pulses occurred during deposition of the two major cycles. In the initial fault-controlled half-graben, a basin slope and alluvial fan system (Sikalamba Conglomerate Formation), draining southeastward, was apparently succeeded, without an intervening transitional facies, by a braided river system (Zongwe Sandstone Formation) draining southwestward, parallel to the basin margin. Glaciation followed by deglaciation resulted in glaciofluvial and glacio-lacustrine deposits of the Upper Carboniferous to Lower Permian Siankondobo Sandstone Formation of the Lower Karoo Group, and isostatic rebound eventually produced a broad flood plain on which the coal-bearing Lower Permian Gwembe Coal Formation was deposited. Fault-controlled maximum subsidence is represente by the lacustrine Upper Permian Madumabisa Mudstone Formation. Block-faulting and downwarping, probably due to the Gondwanide Orogeny, culminated with the introduction of large quantities of sediment through braided fluvial systems that overwhelmed and terminated Madumabisa Lake sedimentation, and is now represented by the Triassic Escarpment Grit and Interbedded Sandstone and Mudstone Formations of the Upper Karoo Group. Outpourings of basaltic flows in the Early Jurassic terminated Karoo sedimentation. 相似文献
10.
砂岩稀土元素地球化学特征在沉积物源区分析中的应用——以中国东北漠河盆地中侏罗统为例 总被引：2，自引：0，他引：2
详细取样分析显示,漠河盆地中侏罗统砂岩具有如下稀土元素地球化学特征:(1)绣峰组、额木尔河组和开库康组砂岩的稀土元素球粒陨石标准化配分模式均表现出轻稀土富集、重稀土亏损但具变化平缓和明显的Eu负异常特征;二十二站组虽呈现轻稀土富集、重稀土亏损但变化平缓的特征,但没有明显的Eu负异常特征,反映了砂岩形成时的物源有差别。(2)漠河盆地中侏罗统的物源主要来自于上地壳长英质源区,源岩可能为花岗岩、变质岩和沉积岩的混合;但二十二站组和额木尔河组时期还可能有来自下地壳或幔源的深部物质（基性岩）加入导致物源发生了变化。(3)漠河盆地中侏罗统物源区的构造背景为活动大陆边缘的岛弧环境。(4)Ce/Ce*和Ceanom指数显示漠河盆地中侏罗统的古环境为还原环境,对油气生成十分有利。 相似文献
11.
The subsidence history of the Soutpansberg Basin was reconstructed by a tectonic subsidence analysis coupled with backstripping calculations based on data of newly interpreted sequence boundaries. Furthermore,burial and time plots were constructed in order to understand the burial and thermal history of the basin. Input data were based on facies,lithostratigraphic models and tectonic interpretations. The studied succession is up to 1000 m and is underlain by the Achaean Limpopo Mobile Belt. The subsidence within the basin supports the primary graben system which must have been centred within the present basins,and later became a region of faulting. The subsidence and burial history curves suggests two phases of rapid subsidence during the Early-Late Permian(300–230 Ma) and Middle Triassic(215–230 Ma). The areas of greater extension subsided more rapidly during these intervals. Two slow subsidence phases are observed during the Late Triassic(215–198 Ma) and Early Jurassic(198–100 Ma). These intervals represent the post-rift thermal subsidence and are interpreted as slow flexural subsidence. Based on these observations on the subsidence curves,it is possible to infer that the first stage of positive inflexion(300 Ma) is therefore recognised as the first stage of the Soutpansberg Basin formation. 相似文献
12.
《地学前缘(英文版)》2023,14(3):101527
Songliao Basin, the largest Mesozoic intracontinental nonmarine basin in eastern China, initiated during the latest Jurassic as a backarc extensional basin; rifting failed and thermal cooling controlled subsidence through the early Late Cretaceous. Integrating 2-D and 3D reflection seismic and borehole data with regional geological studies, we interpret sedimentary sequence and structural patterns of the Coniacian-Maastrichtian fill of Songliao Basin as defining a retroforeland basin system developed after 88 Ma (marked by the T11 unconformity in the basin), including (1) significant increase in the thickness of the Nenjiang Formation eastward towards orogenic highlands of the Zhangguangcai Range and the convergent continental margin; (2) a shift of detrital provenance in the basin from north to southeast; and (3) propagation of E-W shortened structures, increasing eastward in amplitude, frequency, and degree of inversion toward the orogen. During latest Cretaceous, foreland basin fill progressively deformed, as the foredeep evolved to a wedge-top tectonic setting, marked by the basin-wide T04 unconformity within the upper Nenjiang Formation at 81.6 Ma. Much of the basin was brought into the orogenic wedge and eroded by the end of the Cretaceous. Late Jurassic/Early Cretaceous backarc rifting of uncratonized basement comprised of accreted terranes likely facilitated and localized the foreland. Synrift normal faults reactivated and extensively inverted as thrust faults are prominent in the eastern 1/3 of the basin, whereas folds developed above detachments in shaley early post-rift strata dominate the western 2/3 of the basin. Songliao foreland development likely was driven by changing plate dynamics and collision along the Pacific margin after 88 Ma. 相似文献
13.
《International Geology Review》2012,54(10):866-892
The stratigraphic and structural evolution of the Pattani Basin, the most prolific petroleum basin in Thailand, reflects the extensional tectonic regime of continental Southeast Asia. E-W extension resulting from the northward collision of India with Eurasia since the Early Tertiary resulted in the formation of a series of N-S-trending sedimentary basins, which include the Pattani Basin. The sedimentary succession in the Pattani Basin is divisible into synrift and post-rift sequences. Deposition of the synrift sequence accompanied rifting and extension, with episodic block faulting and rapid subsidence. The synrift sequence comprises three stratigraphic units: (1) Upper Eocene to Lower Oligocene alluvial-fan, braidedriver, and floodplain deposits; (2) Upper Oligocene to Lower Miocene floodplain and channel deposits; and (3) a Lower Miocene regressive package consisting of marine to nonmarine sediments. Post-rift succession comprises: (1) a Lower to Middle Miocene regressive package of shallow marine sediments through floodplain and channel deposits; (2) an upper Lower Miocene transgressive sequence; and (3) an Upper Miocene to Pleistocene transgressive succession. The post-rift phase is characterized by slower subsidence and decreased sediment influx. The present-day shallow-marine condition in the Gulf of Thailand is the continuation of this latest transgressive phase. The subsidence and thermal history of the Pattani Basin is consistent with a nonuniform lithospheric-stretching model. The amount of extension as well as surface heat flow generally increases from the margin to the basin center. The crustal stretching factor (β) varies from 1.3 at the basin margin to 2.8 in the center. The subcrustal stretching factor (5) ranges from 1.3 at the basin margin to more than 3.0 in the basin center. The stretching of the lithosphere may have extended the basement rocks by as much as 45 to 90 km and has led to passive upwelling of the aesthenosphere, resulting in high heat flow (1.9 to 2.5 Heat Flow Units [HFU]) and high geothermal gradient (45 to 60° C/km). The validity of nonuniform lithospheric stretching as a mechanism for the formation of the Pattani Basin is confirmed by the good agreement between the level of organic maturation modeled on the basis of the predicted heatflow history and measured vitrinite reflectance at various depths measured in some 30 boreholes. 相似文献
14.
Jurassic extensional basins developed along the northwestern margin of South America during the break-up of Pangea. Presently, these basins are dispersed in several tectonic blocks of the northern Andes and Mexico, hindering reconstruction of western equatorial Pangea before break-up. This is the case of the Cosinas Basin (Guajira block) and the Machiques Basin (Perijá Range), in northern Colombia, which are filled by Jurassic sedimentary and volcano-sedimentary successions. Autochthonous and para-autochthonous hypotheses on the origin of this basins have been proposed. The purpose of this research is to document the sedimentological evolution, depositional age (Sr-isotope + U-Pb geochronology), sediment provenance and paleogeography of the Cosinas and Machiques basins in order to constrain whether these basins formed within a single extensional margin or they formed as extensional basins in different tectonic blocks. Volcanic detrital zircon U-Pb ages documented in La Quinta Formation in the Machiques Basin and at the base of Rancho Grande Formation in the Cosinas Basin suggest that extensional basins were active in Early Jurassic time. However, a significant difference exists in their subsequent history. Whereas in the Machiques Basin dominates the accumulation of Lower and Middle Jurassic volcanoclastic deposits with abrupt lateral thickness changes, accumulation in the Cosinas Basin is dominantly of siliciclastic strata, with the record of two major marine incursions in Late Jurassic time. Integration of provenance results indicates that the Santander Massif supplied sediments to the Machiques Basin. In contrast, Middle to Upper Jurassic sandstones of the Cosinas Basin document unroofing of basement blocks that include metamorphic, sedimentary and plutonic rocks from the Guajira and Maya blocks. The similarity in age and composition of pre-Jurassic rocks in northwestern South America and the so-called peri-Gondwana blocks in the Mexican subcontinent (i.e., Maya and Oaxaquia blocks) challenge the use of detrital zircon population as an indicator of the autochthonous or para-autochthonous origin of the Guajira block. Large uncertainty of paleomagnetic results, and the lack of constraints for the time magnetization acquisition preclude estimating paleolatitudes for the Guajira block in Jurassic time but support previous interpretation of ca. 70°-90° clockwise rotation of the Guajira block relative to stable South America craton.Our preferred paleogeography considers that the Cosinas and Machiques basins were close to each other along the western continental margin of Pangea during the onset of extension in Early Jurassic time. The change from continental to marine depositional environments in Middle to Late Jurassic time along the Cosinas Basin, which have not been identified in the Machiques Basin or other autochthonous Jurassic basins in northwestern South America, allow us to propose that these blocks were separated during the Callovian - Tithonian interval, with the Cosinas Basin remaining closer to a conjugate Mexican margin, that we interpret as the Maya block. Collision of the Guajira block with the South American margin occurred near the Jurassic-Cretaceous boundary, as documented by deformation of Jurassic units previous to deposition of Berriasian strata in the Guajira block. 相似文献
15.
准噶尔盆地侏罗系西山窑组沉降中心的分布及其构造控制 总被引：7，自引：4，他引：3
以准噶尔盆地21条典型的地震剖面上的329个取数据点资料为基础,应用EBM盆地模拟系统,对侏罗系西山窑组地层进行了沉降史回剥分析。从回剥的结果来看,盆地的沉降速率在不同时期显示出显著的不均一变化,其中在西山窑二段地层沉积时期的沉降速率在盆地南缘平均为70~90m/Ma,北缘及腹部地区只有30m/Ma左右;在西山窑一段地层沉积时期,盆地南缘的沉降速率则达到了120m/Ma,北缘及腹部相比前一阶段则没有太大变化。由此可以确定玛湖凹陷、乌伦古坳陷和昌吉凹陷是盆地在西山窑组地层沉积时期的沉降中心,盆地南缘的昌吉凹陷则是最主要和最大的的沉降中心。进一步分析,这些沉降中心的形成明显受到了周缘山系逆冲推覆作用的构造负载和盆地基底构造的制约,使盆地形成了隆坳相间的古地貌格局。由于沉降中心是低位三角洲砂体发育的重要部位,从而为隐蔽油气藏的勘探提供了方向。 相似文献
16.
《Geodinamica Acta》2013,26(1-3):83-100
The Magura Basin domain developed in its initial stage as a Jurassic-Early Cretaceous rifted passive margin that faced the eastern parts of the oceanic Alpine Tethys. In the pre- and syn-orogenic evolution of the Magura Basin the following prominent periods can be distinguished: Middle Jurassic-Early Cretaceous syn-rift opening of basins (1) followed by Early Cretaceous post-rift thermal subsidence (2), latest Cretaceous–Paleocene syn-collisional inversion (3), Late Paleocene to Middle Eocene flexural subsidence (4) and Late Eocene - Early Miocene synorogenic closing of the basin (5). The driving forces of tectonic subsidence of the basin were syn-rift and thermal post-rift processes, as well as tectonic loads related to the emplacement of accretionary wedge. This process was initiated at the end of the Paleocene at the Pieniny Klippen Belt (PKB)/Magura Basin boundary and was completed during Late Oligocene in the northern part of the Magura Basin. During Early Miocene the Magura Basin was finally folded, thrusted and uplifted as the Magura Nappe. 相似文献
17.
《Journal of South American Earth Sciences》2009,27(4):369-382
Changes in the sedimentologic and stratigraphic characteristics of the coal-bearing middle Oligocene–late Miocene siliciclastic Amagá Formation, northwestern Colombia, reflect major fluctuations in the stratigraphic base level within the Amagá Basin, which paralleled three major stages of evolution of the middle Cenozoic Andean Orogeny. These stages, which are also traceable by the changes in the compositional modes of sandstones, controlled the occurrence of important coal deposits. The initial stage of evolution of the Amagá Basin was related to the initial uplift of the Central Cordillera of Colombia around 25 Ma, which promoted moderate subsidence rates and high rates of sediment supply into the basin. This allowed the development of aggradational braided rivers and widespread channel amalgamation resulting in poor preservation of both, low energy facies and geomorphic elements. The presence of poorly preserved Alfisols within the scarce flood plains and the absence of swamp deposits suggest arid climate during this stage. The compositional modes of sandstones suggest sediment supply from uplifted basement-cored blocks. The second stage of evolution was related to the late Oligocene eastward migration of the Pre-Andean tholeitic magmatic arc from the Western Cordillera towards the Cauca depression. This generated extensional movements along the Amagá Basin, enhancing the subsidence and increasing the accommodation space along the basin. As a result of the enhanced subsidence rates, meandering rivers developed, allowing the formation of extensive swamps deposits (currently coal beds). The excellent preservation of Entisols and Alfisols within the flood plain deposits suggests rapid channels migration and a humid climate during deposition. Moderate to highly mature channel sandstones support this contention, and point out the Central Cordillera of Colombia as the main source of sediment. Enhanced subsidence during this stage also prevented channels amalgamation and promoted both, high preservation of geomorphic elements and high diversity of sedimentary facies. This resulted in the most symmetric stratigraphic cycles of the entire Amagá Formation. The final stage of evolution of the Amagá Basin was related to the early stage of development of the late Miocene northwestern Andes tholeitic volcanism (from ∼10 to ∼8 Ma). The extensive thrusting and folding associated to this volcanism reduced the subsidence rates along the basin and thus the accommodation space. This permitted the development of highly aggradational braided rivers and promoted channels amalgamation. Little preservation of low energy facies, poor preservation of the geomorphic elements and a complete obliteration of important swamp deposits (coal beds) within the basin are reflected by the most asymmetric stratigraphic cycles of the whole formation. The presence of greenish/reddish flood plain deposits and Alfisols suggests a dry climate during this depositional stage. The presence of channel sandstones with high contents of volcanic rock fragments supports a dry climate, and suggests an incipient phase of the Combia tholeiitic magmatism present during deposition of the Amagá Formation. The subsequent eastward migration of the NW Andes magmatic arc (after ∼8 Ma) may have produced basin inversion and suppressed deposition along the Amagá Basin. 相似文献
18.
The Paleocene-recent post-rift subsidence history recorded in the Mumbai Offshore Basin off western continental margin of India is examined. Results obtained through 2-D flexural backstripping modelling of new seismic data reveal considerable thermo-tectonic subsidence over last ca. 56 Myr. Reverse postrift subsidence modelling with variable β stretching factor predicts residual topography of ca. 2000 m to the west of Shelf Margin Basin and fails to restore late Paleocene horizon and the underlying igneous basement to the sea level. This potentially implies that:(1) either the igneous basement formed during the late Cretaceous was emplaced under open marine environs; or(2) a laterally varying cumulative subsidence occurred within Mumbai Offshore Basin(MOB) during ca. 68 to ca. 56 Ma. Pre-depositional topographic variations at ca. 56 Ma across the basin could be attributed to the extensional processes such as varied lower crustal underplating along Western Continental Margin of India(WCMI). Investigations about basement tectonics after unroofing of sediments since late Paleocene from this region support a transitional and heavily stretched nature of crust with high to very high β factors. Computations of past sediment accumulation rates show that the basin sedimentation peaked during late Miocene concurrently with uplift of Himalayan-Tibetan Plateau and intensification of Indian monsoon system. Results from basin subsidence modelling presented here may have significant implications for further studies attempting to explore tectono-climatic interactions in Asia. 相似文献
19.
侏罗系是柴达木盆地最重要的源储层系之一。通过野外地质、剖面实测、地震解释、显微构造分析等大量系列资料的综合应用与分析,认为研究区自中生代以来,经历了印支期右行逆冲-走滑构造运动、早—中侏罗世伸展运动、早白垩世北西-南东向挤压及新生代南北向挤压运动,它们与早侏罗世至中侏罗世早期(小煤沟组至大煤沟组)在NE向伸展应力场作用下形成的断陷盆地、中侏罗世晚期至晚侏罗世(彩石岭组—洪水沟组)热力沉降坳陷盆地、早白垩世南北向挤压坳陷盆地密切相关。侏罗纪原型盆地发育三类沉积边界,即盆缘不整合边界(缓坡型和陡坡型边界)、盆内正断层边界、后期逆断层改造边界。不同的现存盆地边界类型对原型盆地恢复的作用不同。侏罗纪盆地以东昆仑构造带为界具有"北陆南洋"的古地理格局,柴达木地区的侏罗纪盆地主要发育在沿岸造山带和岛弧带的山前坳陷以及薄弱的柴北缘加里东俯冲碰撞带之上,形成相对分隔的独立盆地群。柴达木早、中、晚侏罗世原型盆地的分布因受到古特提斯洋向北偏东方向的俯冲作用和阿尔金断裂左旋走滑作用的影响,其沉积中心和沉积范围呈现出从早到晚向东北方向逐渐迁移的规律。早侏罗世盆地的沉积沉降中心主要位于柴北缘西部的冷湖—马海一带,中侏罗世盆地的沉积沉降中心主要位于柴北缘中段的大柴旦—怀头他拉一带,而晚侏罗世盆地的沉积沉降中心主要位于德令哈—乌兰一带。 相似文献
20.
盆地构造运动、气候变化对后裂谷盆地源汇系统、沉积体系和层序建造影响的研究尚待深入.松辽盆地是一个富含油气的晚白垩世大型后裂谷盆地.应用构造层序分析方法,利用测井曲线、岩心观察成果、三维地震和录井资料,在泉四段（K1-2q4）至嫩江组（K2n）划分出两个二级层序和7个三级层序.这7个三级层序根据其发育的古地貌背景和气候条件,可识别出发育在二级层序底部、干旱气候环境的低可容纳空间层序建造和发育在二级层序中上部、湿润-半湿润气候条件下的高可容纳空间层序建造.高可容纳空间层序建造又可根据古地貌背景划分为缓坡和受挠曲坡折控制的高可容纳层序建造.研究区这两个二级层序及其三级层序建造特征是对盆地幕式构造运动和气候变化的响应.一个热沉降幕开始于盆地基底抬升后的沉降.基底抬升造成气候干旱、剥蚀,形成不整合,随后的沉积沉降发育低可容纳空间层序.当盆地基底沉降较快,且沉降速率大于沉积物供给速率、气候湿润、湖平面上升导致盆地可容纳空间快速增长时,发育以水进域和高位域为主的高可容纳空间层序建造.二级层序界面两侧发育的地层圈闭,沉积在高可容纳空间背景的层序其水进和高位域早期的重力流砂体为岩性油藏的主要圈闭,该类砂体在Sqqn1和Sqn1层序最为发育,在坡折带及其之下集中分布. 相似文献