Syn-rift to post-rift tectonic transition and drainage reorganization in continental rifting basins: Detrital zircon analysis from the Songliao Basin,NE China     

《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   

塔河油田上奥陶统良里塔格组储层特征及控制因素     

卢宇峰  刘存革  杜春晖  姜昊罡  梁锋 《新疆地质》2011,29(2):198-202

塔河油田勘探表明,上奥陶统良里塔格组是潜在勘探层位.通过岩心、测井、薄片、物性、钻井和生产测试等资料综合分析,认为良里塔格组具两套岩性组合,顶部和底部为浅水高能沉积,中间为深水低能沉积,物性比中下奥陶统差,渗透率非均质性较强,主要受泥质条带和裂缝影响.储集空间主要包括溶蚀孔隙、溶蚀孔洞和裂缝3类.储层类型有孔隙-裂缝型和孔洞-裂缝型两类,后者是主要储层类型.储集空间形成主要受同生期和表生期岩溶作用、埋藏溶蚀作用和断裂作用4个因素控制,其中断裂作用是良里塔格组储层形成和分布的主控因素.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987111000594     

Victor D. Mats  Tatiana I. Perepelova 《地学前缘(英文版)》2011,2(3):349-365

A new model is suggested for the history of the Baikal Rift,in deviation from the classic two-stage evolution scenario,based on a synthesis of the available data from the Baikal Basin and revised correlation between tectonic-lithological-stratigraphic complexes(TLSC) in sedimentary sections around Lake Baikal and seismic stratigraphic sequences(SSS) in the lake sediments.Unlike the previous models,the revised model places the onset of rifting during Late Cretaceous and comprises three major stages which are subdivided into several substages.The stages and the substages are separated by events of tectonic activity and stress reversal when additional compression produced folds and shear structures.The events that mark the stage boundaries show up as gaps,unconformities,and deformation features in the deposition patterns. The earliest Late Cretaceous-Oligocene stage began long before the India-Eurasia collision in a setting of diffuse extension that acted over a large territory of Asia.The NW-SE far-field pure extension produced an NE-striking half-graben oriented along an old zone of weakness at the edge of the Siberian craton.That was already the onset of rift evolution recorded in weathered lacustrine deposits on the Baikal shore and in a wedge-shaped acoustically transparent seismic unit in the lake sediments.The second stage spanning Late Oligocene-Early Pliocene time began with a stress change when the effect from the Eocene India-Eurasia collision had reached the region and became a major control of its geodynamics.The EW and NE transpression and shear from the collisional front transformed the Late Cretaceous half-graben into a U-shaped one which accumulated a deformed layered sequence of sediments.Rifting at the latest stage was driven by extension from a local source associated with hot mantle material rising to the base of the rifted crust.The asthenospheric upwarp first induced the growth of the Baikal dome and the related change from finer to coarser molasse deposition.With time,the upwarp became a more powerful stress source than the collision,and the stress vector returned to the previous NW-SE extension that changed the rift geometry back to a half-graben. The layered Late Pliocene-Quaternary subaerial tectonic-lithological-stratigraphic and the Quaternary submarine seismic stratigraphic units filling the latest half-graben remained almost undeformed.The rifting mechanisms were thus passive during two earlier stages and active during the third stage. The three-stage model of the rift history does not rule out the previous division into two major stages but rather extends its limits back into time as far as the Maastrichtian.Our model is consistent with geological, stratigraphic,structural,and geophysical data and provides further insights into the understanding of rifting in the Baikal region in particular and continental rifting in general.  相似文献   

The continent-ocean transition at the southeastern margin of the South China Sea   总被引：2，自引：0，他引：2  

D. Franke  U. BarckhausenN. Baristeas  M. EngelsS. Ladage  R. LutzJ. Montano  N. PellejeraE.G. Ramos  M. Schnabel 《Marine and Petroleum Geology》2011,28(6):1187-1204

The South China Sea formed by magma-poor, or intermediate volcanic rifting in the Paleogene. We investigate the structure of the continent-ocean transition (COT) at its southern margin, off NW Palawan between the continental blocks of Reed Bank and the islands of Palawan and Calamian. Several surveys, recorded by the BGR from 1979 to 2008, established a comprehensive database of regional seismic lines, accompanied with magnetic and gravity profiles.We interpret two major rifted basins, extending in the NE direction across the shelf and slope, separated by a structural high of non volcanic origin.The continent-ocean transition is interpreted at the seaward limit of the continental crust, when magnetic spreading anomalies terminate some 80-100 km farther north. The area in between displays extensive volcanism - as manifest by extrusions that occasionally reach and cut the seafloor, by dykes, and by presumed basaltic lava flows - occurring after break-up.The COT is highly variable along the NW Palawan slope: One type shows a distinct outer ridge at the COT with a steep modern seafloor relief. The other type is characterised by rotated fault blocks, bounded by listric normal faults ramping down to a common detachment surface. Half-grabens developed above a strongly eroded pre-rift basement. The seafloor relief is smooth across this other type of COT.We suggest the pre-rift lithospheric configuration had major influence on the formation of the COT, besides transfer zones. Volcanic domains, confined to the north of competent crustal blocks correlate with the style of the COT.Gravity modelling revealed an extremely thinned crust across the shelf. We propose a depth-dependent extension model with crust being decoupled from mantle lithosphere, explaining the discrepancy of subsidence observed across the South China Sea region.  相似文献   

Structurally controlled hydrothermal dolomites in Albian carbonates of the Asón valley,Basque Cantabrian Basin,Northern Spain     

M.A. López-Horgue  E. Iriarte  S. Schröder  P.A. Fernández-Mendiola  B. Caline  H. Corneyllie  J. Frémont  M. Sudrie  S. Zerti 《Marine and Petroleum Geology》2010

Shallow marine carbonate sedimentation dominated during the Albian in the western part of the Basque Cantabrian Basin in Northern Spain, forming the large Ramales Platform. This platform originated on a less subsiding tectonic block facing deeper and more subsiding areas to the south and east, which were created by tectonic activity in the Basin. Fracture-related hydrothermal dolomites hosted in these Albian carbonates are well exposed in the Asón valley area. Mapping in the studied area revealed several dolomite bodies related to main faults that cut the stratification almost at right angles. The bodies show a vertical development along fault-strike up to 900 m thick from which kilometre-scale branches expand following the stratification. Dolomitization is pervasive and independent of the limestone facies. Main dolomite facies are fine replacive, sucrosic and saddle. Petrography, C, O and Sr isotopes and fluid-inclusion analysis support a polyphase hydrothermal dolomitization at fluid temperatures between 75 °C and 240 °C and highly variable salinity of up to 22 wt.% NaCl. Fine dolomite replaced limestone first and then, sucrosic and saddle dolomites replaced part of the first dolomite and cemented newly created fracture porosity together with different calcite cements. Zebra dolomites and hydroclastic breccias are products of this later stage. Burial analysis of the host rock supports maximum burial temperatures of 80 °C and intense tectonic activity from the Albian to Turonian with a latest Albian peak subsidence. Albian stretching of the crust and subsequent ascent of the isotherms in the area is suggested to have produced sufficient heat to the dolomitizing fluids. The structural analysis indicates a strong transtensional tectonic activity in the studied area during Albian to Turonian time with the creation of an overstep between W–E trending and N–S trending faults. Fluids moved from subsiding areas to fractured uplifted parts of the Ramales Platform, enhanced by diapiric activity.  相似文献   

Thermal regime of the northwest Indian rifted margin – Comparison with predictions     

Gérôme Calvès  Anne M. Schwab  Mads Huuse  Peter D. Clift  Asif Inam 《Marine and Petroleum Geology》2010

We use a simple approach to estimate the present-day thermal regime along the northwestern part of the Western Indian Passive Margin, offshore Pakistan. A compilation of bottom borehole temperatures and geothermal gradients derived from new observations of bottom-simulating reflections (BSRs) allows us to constrain the relationship between the thermal regime and the known tectonic and sedimentary framework along this margin. Effects of basin and crustal structure on the estimation of thermal gradients and heat flow are discussed. A hydrate system is located within the sedimentary deep marine setting and compared to other provinces on other continental margins. We calculate the potential radiogenic contribution to the surface heat flow along a profile across the margin. Measurements across the continental shelf show intermediate thermal gradients of 38–44 °C/km. The onshore Indus Basin shows a lower range of values spanning 18–31 °C/km. The Indus Fan slope and continental rise show an increasing gradient from 37 to 55 °C/km, with higher values associated with the thick depocenter. The gradient drops to 33 °C/km along the Somnath Ridge, which is a syn-rift volcanic construct located in a landward position relative to the latest spreading center around the Cretaceous–Paleogene transition.  相似文献   

Potential implications of differential preservation of testate amoeba shells for paleoenvironmental reconstruction in peatlands   总被引：1，自引：0，他引：1  

Edward A. D. Mitchell  Richard J. Payne  Mariusz Lamentowicz 《Journal of Paleolimnology》2008,40(2):603-618

Testate amoebae are now commonly used in paleoenvironmental studies but little is known of their taphonomy. There is some experimental evidence for differential preservation of some testate amoeba shell types over others, but it is unclear what, if any impact this has on palaeoenvironmental reconstruction. To investigate this issue we looked at palaeoecological evidence for the preservation of different shell types. We then investigated the possible impact of selective preservation on quantitative palaeoenvironmental inference. We first used existing palaeoecological data sets to assess the vertical patterns of relative abundance in four testate amoeba shell types: (1) shells made of secreted biosilica plates (idiosomes, e.g. Euglypha), (2) idiosomes with thick organic coating (Assulina), (3) proteinaceous shells (e.g. Hyalosphenia), (4) shells built from recycled organic or mineral particles (xenosomes) (e.g. Difflugia, Centropyxis). In three diagrams a clear pattern of decay was only observed for the idiosome type. In order to assess the implications of differential preservation of testate amoeba taxa for paleoenvironmental reconstruction we then carried out simulations using three existing transfer functions and a wide range of scenarios, downweighting different test categories to represent the impact of selective test decomposition. Simulation results showed that downweighting generally reduced overall model performance. However downweighting a shell type only produced a consistent directional bias in inferred water table depth where that shell type is both dominant and shows a clear preference along the ecological gradient. Applying a scenario derived from previous experimental work did not lead to significant difference in inferred water table. Our results show that differential shell preservation has little impact on paleohydrological reconstruction from Sphagnum-dominated peatlands. By contrast, for the minerotrophic peatlands data-set loss of idiosome tests leads to consistent underestimation of water table depth. However there are few studies from fens and it is possible that idiosome tests are not always dominant, and/or that differential decomposition is less marked than in Sphagnum peatlands. Further work is clearly needed to assess the potential of testate amoebae for paleoecological studies of minerotrophic peatlands.  相似文献   

山东沂沭断裂带早白垩世晚期恐龙足迹特征差异性^*   总被引：1，自引：0，他引：1       下载免费PDF全文

彭楠  柳永清  旷红伟  吴清资  刘海  陈军  许欢  徐加林  汪明伟  王宝红  王克柏  陈树清  张艳霞 《古地理学报》2013,15(4):517-528

近些年来,在山东沂沭断裂带南部地区(莒南、临沭、郯城和东海）的下白垩统上部大盛群中发现了大量的恐龙足迹化石,而这些化石反映的足迹类型、形态大小、足迹踩踏深度等方面都存在有差异性。研究发现,在足迹类型方面,莒南地区以兽脚类和鸟脚类恐龙足迹为主,临沭、郯城和东海地区以蜥脚类恐龙足迹为主。足迹大小方面,莒南地区的兽脚类足迹可划分为类型Ⅰ和类型Ⅱ两种类型,而东海地区的恐龙足迹主要属于类型Ⅱ,但是莒南地区大多数足迹的趾间角要小于东海地区的,这可能是由于兽脚类恐龙属种的不同所造成的;莒南地区鸟脚类足迹绝大多数要小于临沭地区的鸟脚类足迹;郯城地区的蜥脚类足迹较小,而莒南、临沭和东海地区大多数蜥脚类足迹的大小较为相似,个别临沭和莒南地区的蜥脚类恐龙足迹较大。足迹踩踏深度方面,临沭、东海和郯城地区的足迹相比莒南地区的足迹要稍深,这与足迹形成在不同湿度、黏度、颗粒度的沉积物表面上有密切联系。基于上述研究认为,在早白垩世晚期,沂沭断裂带内生活着种类繁盛,数量庞大的恐龙动物群,联系到沂沭断裂带东部诸城地区早白垩世早期地层中也发现有大量的以兽脚类为主的恐龙足迹化石,推断在早白垩世,沂沭断裂带及胶莱盆地当时为一个理想的恐龙生存、繁衍的栖息地。同时,山东早白垩世大量恐龙足迹化石的发现也为整个华北甚至东北亚地区晚中生代恐龙属种的分布、演化以及古地理研究提供了丰富的材料和信息。  相似文献   

汾河上游土地利用变化及其水文响应研究   总被引：4，自引：1，他引：3  

陆志翔  杨永刚  邹松兵  肖洪浪  尹振良  谢家丽 《冰川冻土》2014,36(1):192-199

以河岔水文站以上的汾河流域为研究区,采用土地利用转移矩阵和SWAT模型模拟方法,就汾河上游土地利用变化对水文过程的影响进行研究. 流域从1995-2000年,以耕地向林地和草地转变为主;从2000-2010年,城市建设用地不断增加,主要是对耕地的占用. 结果显示,在相同气候背景、不同土地利用情景（1995、2000年2010年）下,流域1992-2000年多年平均产水量微弱增加（分别为85.69 mm、85.75 mm和85.82 mm）,主要因为耕地持续减少,草地和城市建设用地不断增加. 但是各年产水量的大小关系不完全一致,枯水年和平水年与丰水年存在差异,而土壤水分呈现一致的减少状况. 子流域水平上,降水条件同样影响水文过程对土地利用变化的响应程度. 以上结果表明,汾河流域在退耕还林还草政策等影响下,土地利用发生变化并且直接影响流域的水文过程,但是流域水文过程对土地利用变化的响应还受到降水的影响.  相似文献   

Miocene silicic volcanism in southwestern Idaho: geochronology,geochemistry, and evolution of the central Snake River Plain     

Bill Bonnichsen  William P. Leeman  Norio Honjo  William C. McIntosh  Martha M. Godchaux 《Bulletin of Volcanology》2008,70(3):315-342

New ⁴⁰Ar-³⁹Ar geochronology, bulk rock geochemical data, and physical characteristics for representative stratigraphic sections of rhyolite ignimbrites and lavas from the west-central Snake River Plain (SRP) are combined to develop a coherent stratigraphic framework for Miocene silicic magmatism in this part of the Yellowstone ‘hotspot track’. The magmatic record differs from that in areas to the west and east with regard to its unusually large extrusive volume, broad lateral scale, and extended duration. We infer that the magmatic systems developed in response to large-scale and repeated injections of basaltic magma into the crust, resulting in significant reconstitution of large volumes of the crust, wide distribution of crustal melt zones, and complex feeder systems for individual eruptive events. Some eruptive episodes or ‘events’ appear to be contemporaneous with major normal faulting, and perhaps catastrophic crustal foundering, that may have triggered concurrent evacuations of separate silicic magma reservoirs. This behavior and cumulative time-composition relations are difficult to relate to simple caldera-style single-source feeder systems and imply complex temporal-spatial development of the silicic magma systems. Inferred volumes and timing of mafic magma inputs, as the driving energy source, require a significant component of lithospheric extension on NNW-trending Basin and Range style faults (i.e., roughly parallel to the SW–NE orientation of the eastern SRP). This is needed to accommodate basaltic inputs at crustal levels, and is likely to play a role in generation of those magmas. Anomalously high magma production in the SRP compared to that in adjacent areas (e.g., northern Basin and Range Province) may require additional sub-lithospheric processes. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. This paper constitutes part of a special issue dedicated to Bill Bonnichsen on the petrogenesis and volcanology of anorogenic rhyolites.  相似文献