Permian to Late Triassic evolution of the Longmen Shan Foreland Basin (Western Sichuan): Model results from both the lithospheric extension and flexure

We have analysed 129 stratigraphic sections from the Timan–Pechora basin, from its adjacent continental shelf and from the South Barents Sea basin, in order to determine whether existing models of extensional sedimentary basin formation can be applied to these intracratonic basins or whether new mechanisms of formation need to be invoked. The subsidence history of each section has been calculated using standard backstripping techniques. An inverse model, based on finite-duration lithospheric stretching, has then been used to calculate the distribution of strain rate as a function of time required to fit each subsidence profile. Results demonstrate an excellent fit between theory and observation. By combining our analysis with independent field-based and geophysical observations, we show that the Timan–Pechora basin underwent at least four phases of mild lithospheric stretching during the Phanerozoic (β<1.2). These phases occurred in Ordovician, Late Ordovician–Silurian, Middle–Late Devonian and Permian–Early Triassic times. Growth on normal faults, episodes of volcanic activity and regional considerations provide corroborative support for the existence of all four phases. Although less well constrained, subsidence data from the South Barents Sea basin are consistent with a similar Early–Middle Palaeozoic history. The main difference is that Permian–Early Triassic extension is substantially greater than that seen onshore. This similarity implies structural connectivity throughout their respective evolutions. Finally, subsidence modelling demonstrates that rapid foreland basin formation, associated with the Uralian Orogeny, was initiated in Permo-Triassic times and is confined to the eastern margin of the Timan–Pechora basin. Coeval foreland subsidence does not occur on the eastern margin of the South Barents Sea basin, supporting the allochthonous nature of Novaya Zemlya. The most puzzling result is the existence of simultaneous lithospheric extension and foreland loading in Permian–Early Triassic times. This juxtaposition is most clearly seen within the Timan–Pechora basin itself and suggests that convective drawdown may play a role in foreland basin formation.

Download Full-text

Testing the Mesozoic plate configuration of the Eastern Mediterranean domain

10.5194/egusphere-egu2020-7157 ◽

2020 ◽

Author(s):

Michael Nirrengarten ◽

Geoffroy Mohn ◽

François Sapin ◽

Jon Teasdale ◽

Charlotte Nielsen ◽

...

Keyword(s):

Mediterranean Sea ◽

Carbonate Platform ◽

Eastern Mediterranean ◽

Late Triassic ◽

East Mediterranean ◽

Satellite Gravity ◽

Eastern Mediterranean Sea ◽

Rifted Margins ◽

Lithospheric Extension ◽

Starting Point

At the transition between the Atlantic and the Tethys oceanic systems, the plate kinematic configuration of the East Mediterranean domain during the early Mesozoic is still poorly understood. Several factors like the Messinian salt, the different compressional events, the thick carbonate platforms and Cenozoic deltaic deposits combine to blur the imaging of Eastern Mediterranean rifted margins. This has led to distinct and often markedly contrasting interpretations of the timing of opening (ranging from Carboniferous to Cretaceous), structural evolution (divergent to transform segments) and kinematics (N-S to WNW-ESE extension).To address this long-standing problem, we gathered disparate geological observations from the margins surrounding the Eastern Mediterranean Sea to integrate them in a global plate model. Distinct, end-member plate kinematic scenarios were tested, challenged and iterated by observations from the Eastern Mediterranean rifted margins.The N-African and NW-Arabian margins of the Eastern Mediterranean Sea are relatively weakly reactivated by the different compressional events and were chosen as the starting point of our integrative tectonic study. Legacy plate models for the area mostly show N-S to NNE-SSW opening of the Eastern Mediterranean of pre-Jurassic age. We have integrated dense industrial seismic data, deep boreholes and dredge data, as well as enhanced satellite gravity images that strongly suggests WNW-ESE oriented lithospheric extension and sea floor spreading during the Late Triassic to Early Jurassic.Our approach starts by the mapping of the main extensional and compressional structures, the different crustal domains and the pre-rift facies distribution. We investigate the potential conjugate margins now located and imbricated in the Dinarides, Hellenides and Taurides on the northern side of the East Mediterranean Sea by looking at the drowning ages of the Mesozoic carbonate platform and the related rift structures. We refine the full fit and initial spreading of the Atlantic Ocean using crustal thickness and features observed on both sides of the system to calibrate the motion of Eurasia and Africa, which determine the space available to develop the Eastern Mediterranean Sea. Initial tests on the evolution of the main tectonic plates highlight an insufficient eastward motion of Africa relative to Eurasia (Iberia) to accommodate the extension of Eastern Mediterranean during the Jurassic with a purely WNW-ESE direction of extension. Further hypotheses remain to be tested. However, for now, a scenario involving poly-phased and poly-directional motion of the conjugate continent &#8220;Greater Adria&#8221; during Jurassic is favoured to model the Eastern Mediterranean plate evolution in relation with the closure of the Neo-Tethys further north.

Download Full-text

Segmentation of the Longmen Mountains thrust belt, Western Sichuan Foreland Basin, SW China

Tectonophysics ◽

10.1016/j.tecto.2009.12.007 ◽

2010 ◽

Vol 485 (1-4) ◽

pp. 107-121 ◽

Cited By ~ 28

Author(s):

Wenzheng Jin ◽

Liangjie Tang ◽

Keming Yang ◽

Guimei Wan ◽

Zhizhou Lü

Keyword(s):

Foreland Basin ◽

Thrust Belt ◽

Sw China ◽

Western Sichuan

Download Full-text

Late Triassic tectonic inversion in the upper Yangtze Block: Insights from detrital zircon U-Pb geochronology from south-western Sichuan Basin

Basin Research ◽

10.1111/bre.12310 ◽

2018 ◽

Vol 31 (1) ◽

pp. 92-113 ◽

Cited By ~ 6

Author(s):

Zhaokun Yan ◽

Yuntao Tian ◽

Rui Li ◽

Pieter Vermeesch ◽

Xilin Sun ◽

...

Keyword(s):

Detrital Zircon ◽

Sichuan Basin ◽

Late Triassic ◽

Yangtze Block ◽

Western Sichuan ◽

Tectonic Inversion ◽

Western Sichuan Basin

Download Full-text

Controlling factors and formation mechanism of fractures in the tight-gas sandstones of the Upper Triassic Xujiahe Formation, western Sichuan Basin, China

10.5194/egusphere-egu2020-4123 ◽

2020 ◽

Author(s):

Wenya Lyu ◽

Lianbo Zeng ◽

Shuangquan Chen ◽

Lei Tang ◽

Yunzhao Zhang

Keyword(s):

Formation Mechanism ◽

Isotope Analysis ◽

Late Triassic ◽

Burial History ◽

Thin Sections ◽

Xujiahe Formation ◽

Western Sichuan ◽

Mechanical Stratigraphy ◽

Filling Sequence ◽

Western Sichuan Basin

Based on cores, image logs and thin sections, five sets of fractures are developed in the study area, where faults are developed. Most of fractures are open without fillings, and some fractures are filled with calcite, quartz, bitumen, pyrite and mud. Fractures are mainly controlled by lithology, mechanical stratigraphy and faults. Based on mutual crosscutting relationships of fractures, mineral filling sequence of fracture fillings, fluid inclusion and carbon-oxygen isotope analysis of calcite fillings in fractures, and quartz spintronic resonance analysis of quartz fillings in fractures, in combination with thermal and burial history, the formation sequence and time of fractures were analyzed. The results show that fractures mainly formed over three period, that is, the late Triassic, Middle to Late Jurassic, and Late Cretaceous to Paleogene. Then&#65292;combined with the paleostress evolution and fracture characteristics of the study area, the formation mechanism of fractures was discussed.

Download Full-text

Early Paleozoic Extension-Compression Transition and Formation of a Paleo-Oil Reservoir System in the NW Sichuan Basin: Implications for Deeply Buried Hydrocarbon Accumulation

Geofluids ◽

10.1155/2021/5538174 ◽

2021 ◽

Vol 2021 ◽

pp. 1-25

Author(s):

Xiao Liang ◽

Shu-gen Liu ◽

Liang-liang Wu ◽

Bin Deng ◽

Jing Li ◽

...

Keyword(s):

Oil And Gas ◽

Late Triassic ◽

Oil Reservoir ◽

Hydrocarbon Accumulation ◽

Early Paleozoic ◽

Gas Generation ◽

Western Sichuan ◽

Marine Strata ◽

Complex Structural ◽

Hydrocarbon Distribution

Owing to multiple tectonic events after the Late Triassic, the northern segment of the western Sichuan depression (NSWSCD) has a complex geological history of significant uplift and deeply buried. With abundant oil and gas play in the NSWSCD, the study of paleo-oil reservoir systems and early hydrocarbon accumulation in this area is of great significance for deep marine hydrocarbon distribution prediction in complex structural settings. Analysis on the northern section of the Mianyang-Changning Intracratonic Sag (MY-CN IS) and the Tianjingshan Paleouplift (TJS PU), the two Early Paleozoic tectonic units are laterally superimposed. Combined the reservoir bitumen of the Sinian Dengying Fm firstly, the biomarker (TT23/tT24, S21/S22, etc.) and Organic δ13C (lighter than 30‰) characteristics indicate that the Sinian-Jurassic paleo-oil system in the TJS PU area is the main source of Lower Cambrian organic-rich black shale. This is closely related to the superimposition and combination effects of the intracratonic sag and paleouplift. Therefore, this study establishes a geological-geochemical accumulation model through a combination of R o and fluid inclusion data. The No. 1 fault is an important zoning fault in the NSWSCD, which significantly controls the division of the oil-gas zone. The process of paleo-oil reservoir destroyed directly only exists in the frontal deformation zone. The deep marine strata of the eastern No. 1 fault demonstrate the four-center hydrocarbon accumulation processes, which include oil generation, gas generation, gas storage, and gas preservation. The superdeep Dengying Fm has long-term exploration potential in the NSWSCD.

Download Full-text