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1. Provenance of uppermost Carboniferous–Lower Triassic sandstones, Bogda Mountains, NW China: implication on late Paleozoic tectonic history of southern Central Asian Orogenic Belt

   Wu, S X; Yang, W (August 2025, International Meeting for Applied Geoscience and Energy)

   Provenance of uppermost Carboniferous–Lower Triassic sandstones, Bogda Mountains, NW China: implication on late Paleozoic tectonic history of southern Central Asian Orogenic Belt The Permian-Triassic time is a critical stage in the Paleozoic continental amalgamation and Cenozoic orogenic reactivation of southern Central Asian Orogenic Belt (CAOB). Field, petrographic and detrital zircon U-Pb geochronological data of the uppermost Carboniferous– Lower Triassic sandstones from 3 sections in Bogda Mountains, greater Turpan-Junggar basin, NW China, are used to decipher the tectonic history. They are Tarlong- Taodonggou (TT) and Zhaobishan (ZBS) in the south and Dalongkou (DLK) in the north, 100 km apart and ~7,000 m in total thickness. Four petrofacies of 229 sandstones are defined using the abundance of volcanic, sedimentary, and metamorphic (with polycrystalline quartz) lithics. Petrofacies A (Lv73Ls21(Qp+Lm)6) contains mainly volcanic lithics, indicating a volcanic arc as the main source. Petrofacies B (Lv14Ls41(Qp+Lm)45) and Petrofacies C (Lv38Ls14(Qp+Lm)48) contain mixed sedimentary, metamorphic, and volcanic lithics, indicating multiple sources. Petrofacies D (Lv11Ls82(Qp+Lm)7) contains mainly sedimentary lithics with a trace amount of volcanic and metamorphic lithics, indicating local rift-shoulder sedimentary sources. Additionally, the U-Pb dates of 3505 detrital zircon grains of 35 sandstones were analyzed. The predominant Paleozoic zircon grains yield major age populations at ca. 360–280 Ma and 485–385 Ma. Precambrian dates are present, ranging from 542 Ma to 3329 Ma. During Gzhelian–Asselian, andesite and basalt are the major source lithologies in TT. Zircon ages peak at ~300 Ma. During Sakmarian–Kungurian, basalt and andesite are the main source rocks in TT and ZBS; and zircon ages of both areas peak at ~300 Ma. The Roadian–Wordian is probably represented by a regional unconformity. The Guadalupian source lithology and zircon date show a major change. Andesite is the common and rhyolite and basalt minor source lithologies for TT and DLK; but rhyolite significant for ZBS. A unimodal peak at ~305 Ma occurs in TT; two peaks at 305 and 455 Ma with common Precambrian dates in ZBS; and peaks of 310–295 Ma in DLK. During Wuchiapingian–mid Olenekian, andesite and rhyolite are the common source lithologies for TT and DLK, and rhyolite as the primary volcanic lithology for ZBS. In TT, Wuchiapingian-Induan samples have a major age peak at ~300 Ma, and an Olenekian sample has two peaks at ~300 and ~450 Ma. In ZBS, the age pattern is similar to that of the Guadalupian sample. In DLK, samples have a major age peak at ~310 Ma and a minor peak at ~450 Ma. The comparable age clusters identified by multi-dimensional scaling indicate that North Tianshan is the source for TT and ZBS during the latest Carboniferous–early Permian. But south Central Tianshan became the main source solely to ZBS. During late Permian–Early Triassic, both north and central Tianshan became the common sources to the three areas due to enhanced denudation. The source change in mid-Permian across a regional unconformity is synchronous with Paleo-Asian Ocean closure and arc-continent and continent-continent collisions, which occurred no later than Guadalupian. 

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2. Paleoenvironmental and Paleoclimatic Evolution and Cyclo- and Chrono-Stratigraphy of Upper Permian-Lower Triassic Fluvial-Lacustrine Deposits in Bogda Mountains, NW China – Implications for Diachronous Plant Evolution Across the Permian-Triassic Boundary

   https://doi.org/https://10.1016./j.earscirev.2021.103741  

   Yang, W. (November 2021, Earthscience reviews)

   Stratigraphic sections in the Bogda Mountains, NW China, provide detailed records of late Permian–Early Triassic terrestrial paleoenvironmental and paleoclimatic evolution at the paleo-mid-latitude of NE Pangea. The sections are located in the Tarlong-Taodonggou, Dalongkou, and Zhaobishan areas, ~100 km apart, and ~5000 m in total thickness. An age model was constructed using seven high-resolution U-Pb zircon CA-TIMS dates in the Tarlong-Taodonggou sections and projected to sections in two other areas to convert the litho- and cyclo-stratigraphy into a chronostratigraphy. Sediments were deposited in braided and meandering streams, and lacustrine deltaic and lakeplain-littoral environments. A cyclostratigraphy was established on the basis of repetitive environmental changes for high-order cycles, stacking patterns of high-order cycles, and long-term climatic and tectonic trends for low-order cycles (LC). Sedimentary evidence from the upper Wuchiapingian–mid Induan Wutonggou LC indicates that the climate was generally humid-subhumid and gradually became variable toward a seasonally dry condition in the early Induan. Lush vegetation had persisted across the Permo–Triassic boundary into the early Induan. A subhumid-semiarid condition prevailed during the deposition of mid Induan–lower Olenekian Jiucaiyuan and lower Olenekian Shaofanggou LCs. These three LCs are largely continuous and separated by conformities and diastems. Intra- and inter-graben stratigraphic variability is reflected by variations in thickness, depositional system, and average sedimentation rate, and results in variable spatial and temporal stratigraphic resolution. Such stratigraphic variability is mainly controlled by paleogeographic location, depocenter shift, and episodic uplift and subsidence in the source areas and catchment basin. A changeover of plant communities occurred during the early Induan, postdating the end-Permian marine mass extinction. However, riparian vegetation and upland forests were still present from the mid Induan to early Olenekian, and served as primary food source for terrestrial ecosystems, including vertebrates. Correlation of the vascular plant evolutionary history from the latest Changhsingian to early Induan in the Bogda Mountains with those reported from Australia and south China indicates a diachronous floral changeover on Pangea. The late Permian–Early Triassic litho-, cyclo- and chrono-stratigraphies, constrained by the age model, provides a foundation for future studies on the evolution of continental sedimentary, climatic, biologic, and ecological systems in the Bogda region. It also provides a means to correlate terrestrial events in the mid-paleolatitudes with marine and nonmarine records in the other parts of the world. 

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3. Palaeocupressinoxylon uniseriale n. gen. n. sp., a gymnospermous wood from the upper Permian of Central Taodonggou, southern Bogda Mountains, northwestern China

   https://doi.org/10.1016/j.palwor.2019.06.002  

   Wan, M.L.; Yang, W.; Wang, J. (January 2020, Palaeoworld)

   A silicified wood, Palaeocupressinoxylon uniseriale n. gen. n. sp., is described from the upper Permian of the Central Taodonggou section,Turpan–Hami Basin, Xinjiang Uygur Autonomous Region, northwestern China. Multidisciplinary data including U–Pb ID–TIMS zircon dating,vertebrate and invertebrate biostratigraphic, and cyclostratigraphic correlation from current and previous studies indicate that the fossil bearinginterval is Wuchiapingian (late Permian) in age. The pycnoxylic wood consists of thick-walled tracheids and parenchymatous rays. It is characterizedby separated uniseriate radial tracheidal pits, uniseriate ray cells, and cupressoid cross-field pitting. The absence of growth rings in the wood,together with the occurrence of Argillisols, Gleysols, and Histosols above and below the fossil interval, suggests that a stable landscape and aperennially humid climate prevailed in the Taodonggou area during the Wuchiapingian. 

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4. Evidence of a Continuous Continental Permian-Triassic Boundary Section in western Equatorial Pangea, Palo Duro Basin, Northwest Texas, U.S.A.

   https://doi.org/10.3389/feart.2021.747777  

   Tabor, Neil J.; Geissman, John; Renne, Paul R.; Mundil, Roland; Mitchell, William S.; Myers, Timothy S.; Jackson, Jacob; Looy, Cindy V.; Kirchholtes, Renske P. (May 2022, Frontiers in Earth Science)

   The Whitehorse Group and Quartermaster Formation are extensive red-bed terrestrial sequences representing the final episode of sedimentation in the Palo Duro Basin in north-central Texas, U.S.A. Regionally, these strata record the culmination of a long-term regression sequence beginning in the middle to late Permian. The Whitehorse Group includes beds of abundant laminated to massive red quartz siltstone to fine sandstone and rare dolomite, laminated to massive gypsum, and claystones, as well as diagenetic gypsum. The Quartermaster Formation exhibits a change from nearly equal amounts of thin planar and lenticular fine sandstone and laminated to massive mudstone in its lower half to overlying strata with coarser-grained, cross-bedded sandstones indicative of meandering channels up to 7 m deep and rare overbank mudstones. Paleosols are absent in the Upper Whitehorse Group and only poorly developed in the Quartermaster Formation. Volcanic ash-fall deposits (tuffs) present in uppermost Whitehorse Group and lower Quartermaster Formation strata permit correlation among five stratigraphic sections distributed over ∼150 km and provide geochronologic age information for these rocks. Both the Whitehorse Group and Quartermaster Formation have traditionally been assigned to the late Permian Ochoan (Changhsingian) stage, and workers assumed that the Permian-Triassic boundary is characterized by a regionally significant unconformity. Chemostratigraphic or biostratigraphic evidence for this age assignment, however, have been lacking to date. Single zircon U-Pb CA-TIMS analyses from at least two distinct volcanic ash fall layers in the lower Quartermaster Formation, which were identified and collected from five different localities across the Palo Duro Basin, yield interpreted depositional ages ranging from 252.19 ± 0.30 to 251.74 ± 0.28 Ma. Single zircon U-Pb CA-TIMS analyses of detrital zircons from sandstones located only a few meters beneath the top of the Quartermaster Formation yield a range of dates from Mesoproterozoic (1418 Ma) to Middle Triassic (244.5 Ma; Anisian), the latter of which is interpreted as a maximum depositional age, which is no older than Anisian, thus indicating the Permian-Triassic boundary to lie somewhere within the lower Quartermaster Formation/upper Whitehorse Group succession. Stable carbon isotope data from 180 samples of early-burial dolomicrite cements preserve a chemostratigraphic signal that is similar among sections, with a large ∼−8‰ negative isotope excursion ∼20 m beneath the Whitehorse Group-Quartermaster Formation boundary. This large negative carbon isotope excursion is interpreted to be the same excursion associated with the end-Permian extinction and this is in concert with the new high precision radioisotopic age data presented and the fact that the excursion lies within a normal polarity stratigraphic magnetozone. Dolomite cement δ 13 C values remain less negative (between about −5 and −8 permil) into the lower part of the Quartermaster Formation before becoming more positive toward the top of the section. This long interval of negative δ 13 C values in the Quartermaster Formation is interpreted to represent the earliest Triassic (Induan) inception of biotic and ecosystem “recovery.” Oxygen isotope values of dolomicrite cements show a progressive trend toward more positive values through the boundary interval, suggesting substantially warmer conditions around the end-Permian extinction event and a trend toward cooler conditions after the earliest Triassic. Our observations on these strata show that the paleoenvironment and paleoclimate across the Permian-Triassic boundary in western, sub-equatorial Pangea was characterized by depositional systems that were not conducive to plant preservation. 

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5. Middle Albian provenance, sediment dispersal and foreland basin dynamics in southwestern Montana, North American Cordillera

   https://doi.org/10.1111/bre.12645  

   Rosenblume, Justin A.; Finzel, Emily S.; Pearson, David M.; Gardner, Cole T. (January 2022, Basin Research)

   Abstract The Lower Cretaceous Blackleaf Formation in southwestern Montana records sedimentation in the Idaho‐Montana retroforeland basin of the North American Cordillera. Regional‐scale sedimentology suggests that during Albian time southwestern Montana was partially flooded by an early marine incursion of the Western Interior Seaway during deposition of the Blackleaf Formation. We use sandstone petrography, large‐n(n = 600) U‐Pb detrital zircon geochronology and mixture modelling to determine the provenance of these strata. Our analysis suggests three distinct provenance groups: Group 1 sandstones occur in the eastern region of the study area, are quartz‐rich and have zircon age‐probability peaks of ca. 110, 160, 420–450, 1050 and 1160 Ma; these sandstones match with a primarily Appalachian provenance. Group 2 sandstones occur in the western region of study area, are lithic‐rich and have peaks of ca. 110, 160, 1780, 1840, 1920, 2080 and 2700 Ma; the primary source for these sandstones was exhumed lower‐middle Palaeozoic strata from the Idaho sector of the Sevier belt. Group 3 sandstones occur in the western region of the study area, are lithic‐rich and have prominent peaks of ca. 115, 170, 430, 600, 1085, 1170, 1670 and 1790 Ma; the primary source for these sandstones was exhumed Triassic‐upper Palaeozoic strata from the Idaho sector of the Sevier belt. Our provenance data record a sharp change that coincides with the western shoreline of the seaway, and we infer that it may indicate the position of an irregular, submarine forebulge depozone influenced by dynamic subsidence during a period of reduced thrusting in the adjacent fold‐thrust belt. Albian‐aged sediments in southwestern Montana were delivered by rivers with headwaters in the Sevier belt as well as transcontinental river systems with headwaters in eastern North America. In southwestern Montana, west‐flowing transcontinental fluvial systems were flooded by the Western Interior Seaway as it encroached from the north. 

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