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Magnetostratigraphy, stratigraphic column, paleocurrent directions (all from Yang et al., 2017), sampling sites, and low-temperature thermochronology results for the Mojiazhuang (MJZ) section. The detrital AFT grain ages of the samples were statistically analyzed using RadialPlotter and DensityPlotter (Vermeesch, 2012). (A–F) Photographs of representative stratigraphy in the section.
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The Qilian Shan, which is located along the northeastern margin of the Tibetan Plateau, plays a key role in understanding the dynamics of the outward and upward growth of the plateau. However, when and how tectonic deformation evolved into the geographic pattern which is currently observed in the Qilian Shan are still ambiguous. Here, apatite fissi...
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Rapid denudation and uplift of eastern Tibet have accelerated during the Late Miocene due to lateral lower crustal flow, without a significant contribution from upper crustal shortening. However, growing lines of evidence have revealed that Early Cenozoic faulting controlled enhanced denudation and shortening. Here, we report 51 new zircon and apat...
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... The sediment accumulation record, basin provenance, and angular unconformity between the strata provide evidence for rapid exhumation events within the Xining Basin during the Early Cretaceous and Late Cretaceous [57] (Figure 6a(3)). Detrital AFT data within the Xining Basin (94-77 Ma) [72] (Figure 6a(4)) and bedrock AFT data from the Daban Shan (88-70 Ma) [42] (Figure 6a(5)), and Laji Shan (93-85 Ma) [43] (Figure 6a(6)) demonstrate that rapid exhumation occurred during the Late Cretaceous. Therefore, the basements of the Xining Basin, Daban Shan, and Laji Shan are direct sources of the Cretaceous FT ages in our fluvial samples. ...
... An increase in exhumation and erosion in the Qilian Shan responded to the collision between the Indian and Eurasian continents during the Late Cenozoic [79,80]. Pollen records indicate the NE Tibetan Plateau increased rapidly to 3685 ± 87 m in the Late Miocene (~11 Ma) in the east, (3): [57]; (4): [72]; (5): [42]; (6): [43]; (7): [18,20]; (8): [8,42,73]; (9): [17,74,75]; (10): [42,43,70]; (11): [61,62]; (12): [18]; (13): [46]; (14): [76,77]; (15): [18,78]. (b) Summary map of Mesozoic and Cenozoic low-temperature thermochronology and sedimentology in the Central Qilian Shan and its surrounding areas. ...
... (a) Temporal distribution of tectonic events recorded in the Qilian Shan. (1):[70];(2):[54,56,71]; (3):[57]; (4):[72]; (5):[42]; (6):[43];(7):[18,20];(8):[8,42,73];(9):[17,74,75];(10):[42,43,70];(11):[61,62]; (12):[18]; (13):[46];(14):[76,77];(15):[18,78]. (b) Summary map of Mesozoic and Cenozoic low-temperature thermochronology and sedimentology in the Central Qilian Shan and its surrounding areas. ...
The emergence of the Tibetan Plateau is one of the most significant geological events in East Asia. The Central Qilian Shan connects North and South Qilian Shan in the northeastern part of the Tibetan Plateau. However, the exhumation history of the Central Qilian Block from the Mesozoic to Cenozoic remains unclear. Determining the cooling ages of detrital zircon and apatite in modern river sediments is an ideal method for tracing the evolutionary processes of orogenic belts. In this study, we present the first single-grain detrital apatite (153) and zircon fission-track (108) data for the Huangshui River sediments from the Central Qilian Shan. The decomposition of the dataset revealed major Mesozoic and Cenozoic age peaks at ca. 145–93, and 11 Ma. The Central Qilian Shan entered the intracontinental orogeny stage dating back to the Cretaceous (ca. 145–93 Ma) and Late Cenozoic (ca. 11 Ma) caused by the subduction of the Neo-Tethys and Indian–Asian collision. Therefore, we propose that the geomorphic framework of the northeastern margin of the Tibetan Plateau was initially established during the Mesozoic and further consolidated in the Late Miocene.
Constraining exhumation and tectonic processes along an orogenic plateau's boundary provides important insights into the mechanisms leading to plateau expansion and crustal evolution. The Longshou Shan thrust belt (LSSTB) is located in the foreland of the northern Qilian Shan thrust belt, which is commonly regarded as the northeastern margin of the Tibetan Plateau. The LSSTB is thus ideal for decoding the recent expansion of the Tibetan Plateau by tracking deformational pattern at its northeastern margin. In this study, the spatiotemporal characteristics of exhumation and deformation along the LSSTB are investigated by detailed analysis and numerical modeling of published and new thermochronological data. Five Proterozoic basement and intrusion samples yielded Cretaceous apatite fission-track central ages (126–74 Ma, with mean track lengths of 12.6–13.3 μm), and Late Cretaceous to Eocene apatite (Usingle bondTh)/He mean ages (84–51 Ma). Inverse thermal history modeling reveals multi-stage exhumation of the LSSTB in the Permo-Triassic, late Mesozoic, Paleogene, and post-middle Miocene. Permo–Triassic exhumation hints at a > 250 Ma-old peneplain surface that may have formed in response to the closure of the Paleo-Tethys and Paleo-Asian oceans. Late Mesozoic exhumation likely resulted from intracontinental extensional deformation associated with tectonic processes at the Eurasian continental margin. Exhumation during the Paleogene was likely triggered by the India-Asia collision. Post-middle Miocene periods of uplifts along the reactivated Longshou Shan thrusts (no later than 10 Ma and 5 Ma on the southern and northern Longshou Shan Thrust, respectively) were driven by the northeastward expansion of the Tibetan Plateau. Our results support the LSSTB as a long-lived block boundary since the Permo-Triassic and an emerging plateau boundary that has lately been reactivated by the Tibetan Plateau expansion.
Plain Language Summary
Understanding how tectonic strain resulting from the collision between the Indian and Eurasian plates in the Early Cenozoic can spread to the edges of the Tibetan Plateau is crucial for comprehending the plateau's tectonic development. To investigate this question, we used fault gouge, which resulted from the sliding of brittle faults, to directly reveal faulting information. By conducting illite K‐Ar dating on three samples from the Leibo fault zone (LFZ) at the southeastern margin of the Tibetan Plateau (SEMTP), we found consistent ages of newly formed illite, 52 ± 2, 54 ± 12, and 55 ± 6 million years ago. Since this type of minerals form simultaneously with faulting, these ages reveal a reactivated thrust faulting event of the LFZ, suggesting a nearly simultaneous response of faulting in the SEMTP to the early stage of the India‐Asia collision.
The Weibei uplift in the Ordos Basin has a distinctive tectonic setting and intricate evolutionary history. Along these lines, we have used the stratum temperature, apatite fission track, and vitrinite reflectance data to restore the thermal and hydrocarbon generation histories of the Weibei uplift. The average value of the present geothermal gradient of the Weibei uplift was 27.9°C/km, and the heat flow was 64.9 mW/m ² . The Weibei uplift exhibited a moderate geothermal field. Three uplift cooling events occurred in the Weibei uplift during the Mesozoic era: the late Jurassic-early Cretaceous (162–125 Ma), the late Cretaceous (105–65 Ma), and the Eocene-Oligocene (40–27 Ma). The uplift history indicates an early uplift in the south region and a late uplift in the later stage. The thermal evolution history simulation demonstrates that the lower Palaeozoic Ordovician source rocks began to enter the hydrocarbon generation threshold in the middle Permian-late Permian (270 Ma) era and joined the hydrocarbon generation peak in the early-middle Jurassic event (180 Ma). The upper Palaeozoic Carboniferous-Permian source rocks began to enter the hydrocarbon generation threshold in the later period of the middle Permian period (235 Ma). They joined the hydrocarbon generation peak in the late Jurassic-early Cretaceous period (150 Ma). In addition, Triassic source rocks entered the hydrocarbon generation threshold in the early Cretaceous era (135 Ma) and did not enter the hydrocarbon generation peak until now. The low geothermal gradient of the Weibei uplift in the Palaeozoic-early Mesozoic reached the maximum paleotemperature in the early Mesozoic era (100 Ma) because of tectonic thermal events. The highest geothermal gradient of the early Cretaceous reached 51.5°C/km. The peak period of the hydrocarbon generation of source rocks of the different horizons in the Weibei uplift was regulated by the geothermal field of the early Cretaceous event. Since the late Cretaceous period, the stratum has been uplifted and cooled rapidly, and the hydrocarbon generation process of the source rocks has ceased.
Sediment source-to-sink history is pivotal to investigating the evolution of ancient sedimentary basin. Previous study focuses mostly on reconstruction of various components of siliciclastic sedimentary systems from initial source areas through the dispersal system to deposition areas, but less on the dissolved load that displays distinct transport and deposition dynamics. Here we take the Qaidam Basin (NE Tibet) as a case to provide a solute perspective for deciphering the source-to-sink history of an intracontinental basin. The modern observations exhibit a remarkable contrast of the solute Sr isotopic regime with the northern sources (the Qilian Shan) with high 87 Sr/ 86 Sr ratios and the southern sources with low 87 Sr/ 86 Sr ratios. The paleowater solute 87 Sr/ 86 Sr ratios in the northern basin fluctuate between 0.711 and 0.715 since 54 Ma. Most of the interval remains a higher 87 Sr/ 86 Sr ratio of 0.713, indicating that the solute Sr was supplied solely by the Qilian Shan. But two periods of low 87 Sr/ 86 Sr ratio (0.711-0.712) at 44.5-32 Ma and after 16 Ma suggest that there may be two paleo-megalakes connecting the northern and southern sources, and the solute with low 87 Sr/ 86 Sr ratio from the southern sources can thus approach the northern basin via lake water mixing. The two low 87 Sr/ 86 Sr paleo-megalakes developed at the northwest of the basin at 44.5-32 Ma and at southeast of the basin after 16 Ma, suggesting a southeastward migration of the basin depocenter that was mainly caused by tectonic uplift with a subordinate impact of climate-induced lake expansion. Our results show a more complex and dynamic solute transport routing history in a large basin than that indicated by coarse clastic provenance studies, and suggest that such a solute Sr approach can be useful to trace sediment routing linked to denudation of high-grade metamorphic rocks and hydrological connections under drainage reorganization. Ó
The study of large-scale and long-term sedimentary hiatus and exhumation in vast intraplate basins is of great significance for unravelling their tectonic development, morphodynamics and relationships with petroleum occurrence. The Ordos Basin is an intra-cratonic depression in the western part of the North China Craton that gradually subsides from the Proterozoic to the Mesozoic and contains several post-1.8 Ga unconformities, some of which are related to a series of Cenozoic tectonic events contributing to current plateau setting. While previously published thermochronological data have identified Mesozoic–Cenozoic multiphase cooling events, we report in this paper new apatite fission-track, zircon (Usingle bondTh)/He, and zircon Usingle bondPb geochronology on Paleoproterozoic borehole samples from the oldest sedimentary rocks in the Ordos Basin. Taken together, our data reveal cooling events at ca. 2.44 Ga, 1.97 Ga, 1.84 Ga, 630–570 Ma, 570–277 Ma, 75–15 Ma and ~ 15 Ma. Seismic reflection profiles and associated well cross-section interpretations are used to identify the basin's major unconformities and decipher the stratigraphic pattern. The six recognized unconformities exist between (1) the Precambrian and Cambrian, (2) the Cambrian and Ordovician, (3) the Lower Paleozoic and Upper Paleozoic, (4) the Middle-Upper Triassic and Jurassic, (5) the Jurassic and Lower Cretaceous and (6) the Cretaceous and Cenozoic. The new data allow a re-assessment of the Ordos Basin's amount and timing of erosion and burial. Integrating the existing evidence of exhumation, we interpret the Neoproterozoic cooling and exhumation events as a response to the Neoproterozoic Glaciations during the breakup of Rodina, while Phanerozoic wide subsidence of the Ordos Basin is interrupted by several differential exhumation and cooling events under the multiplate interactions in East Asia. Particularly, late Miocene (ca. 15–8 Ma) exhumation, synchronous topography inversion and deposition of Red Clay involve feedback relationships between tectonics and strengthening of Asian winter monsoon. Our results provide novel insights into of long-term exhumation and related unconformities concerning East Asia orogeny and climate events and impose important constraints on petroleum exploration.
