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1. PROVENANCE OF THE UPPERMOST CARBONIFEROUS–LOWER TRIASSIC SANDSTONES, BOGDA MOUNTAINS, NW CHINA: IMPLICATION ON THE LATE PALEOZOIC TECTONIC HISTORY OF THE SOUTHERN CENTRAL ASIAN OROGENIC BELT

   https://doi.org/10.1130/abs/2024AM-401642  

   Yang, Wan; Wu, Sixuan (January 2024, Geological Society of America)

   The Permian-Triassic time is a significant 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. The sections 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 and U-Pb dates of 3505 zircons of 35 sandstones form the basis for interpretation. 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 represented by a regional unconformity. The Guadalupian source lithology and zircon date show a major change. Andesite is the common and rhyolite and basalt the minor source lithologies for TT and DLK; but rhyolite for ZBS. A unimodal peak at ~305 Ma occurs in TT; but 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; but 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 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 in mid Permian, 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 all 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 along the southern margin of Turpan- Junggar basin no later than Guadalupian. 

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2. 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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3. 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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4. MID-LATE PERMIAN ALPINE GLACIATION AND ASSOCIATED LOESS ACCUMULATION AT MID-LATITUDE NE PANGEA, BOGDA MOUNTAINS, GREATER TURPAN-JUNGGAR INTRACONTINENTAL BASIN, NW CHINA

   https://doi.org/10.1130/abs/2024AM-401982  

   Yang, Wan; Wan, Mingli (January 2024, Geological Society of America)

   The Capitanian–lower Wuchiapingian lower and upper Quanzijie low-order cycles (QZJ LCs) in Bogda Mountains, NW China, containevidence of mountain glaciation and loess deposition in eastern Kazakhstan Plate. They occur in Zhaobishan (ZBS), Tarlong-Taodonggou (TL-TDG), and Dalongkou (DLK) areas, ~100 km apart. The lower QZJ LC overlies a regional unconformity, consists of conglomerate at ZBS at foothills of ancestral north Tianshan and Calcisol, mudrock, sandstone, and conglomerate at TL-TDG andDLK in the basin, and is 1-10s m thick. The basinal deposits are upward-fining meandering stream deposits. In ZBS, fining-upward successions from imbricated boulder–pebble conglomerates to minor sandstones with erosional bases are braided stream deposits.Of 135 randomly-counted cobbles and boulders, 80% are faceted penta-, hexa-, and hepta-hedrons with rounded edges; 75% have atleast one flat face; 60% one concave face (60%); 93% smooth, shiny, and smeared faces; 56% 1–3 sets of parallel to non-parallel striations; and 57% one or more grinding pits, indicating a glacial origin. In contrast, the upper QZJ LC is 60-160 m thick in the basinand 205 m in ZBS. Basinal deposits consist of massive mudstone with a consistent silt-size distribution, interspersed with lenticular upward fining conglomerate to sandstone, interpreted as loess and ephemeral braided stream deposits, respectively. In ZBS, the upper QZJ LC contains mainly upward fining conglomerate–sandstone successions of coarse-grained meandering stream deposits.Few ostracod-bearing shales and well rounded and cross-stratified sandstones are lacustrine and eolian deposits, respectively.Gravels are mainly pebble–granule. 22 counted cobbles are similar to those in lower QZJ and 77% have 1–3 sets of striations, suggesting a dominantly proglacial fluvial setting. Petrified woods with distinct frost rings are common in the QZJ, indicating a freezing upland condition. The basal unconformity signifies tectonic uplift and erosion during closure of Paleo-Asian Ocean. Growth of north Tianshan in an icehouse climate promoted formation of alpine glaciers, which supplied copious fluvial sediments of the lower QZJ.Glacial retreat exposed previous sediments to source the loess accumulated in the basin, but proglacial fluvial deposition persisted inZBS until early Wuchiapingian. 

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5. Interpreting detrital modes and geochemistry of sandstones from the late Paleozoic Tepuel-Genoa Basin: Paleogeographic implications (Patagonia, Argentina)

   https://doi.org/https://doi.org/10.1016/j.jsames.2020.102858  

   Ciccioli, P. L.; Limarino, C. O.; Isbell, J.L.; Taboada, A. C.; Pagani, M. A.; Gulbranson, E.L. (September 2020, Journal of South American earth sciences)

   null (Ed.)

   The provenance of sandstones deposited in the late Paleozoic Tepuel-Genoa Basin is analyzed in this paper. Five sections were sampled in Esquel, Sierra de Tepuel, Sierra de Tecka, El Molle, and Río Genoa areas for petrographic and geochemical studies. The sandstones in the Tepuel-Genoa Basin are dominated by feldspathic litharenites and litharenites, showing lithic fragments of volcanic and sedimentary rocks in the Valle Chico Formation and medium-to high-grade metamorphic rock clasts in the rest of the units. Detrital modes of seventy-five sandstones samples from the Valle Chico, Pampa de Tepuel, Moj´on de Hierro, and Río Genoa formations were counted and analyzed. Seven modal components have discriminant value for identifying provenance areas (Qm, Qi, Lv, Lmm-h, Lm-Lp, Lm, Qpm). These modal components allow identification of three petrofacies: 1. Quartzose-lithic (Qm69Lv2Lm29), 2. Quartzose (Qm89Lv4Lm7) and 3. Volcanic-sedimentary (Qm60Lv38Lm1). The quartzose-lithic petrofacies is mainly composed of monocrystalline quartz, medium- and high-grade metamorphic clasts and polycrystalline quartz with cataclastic texture, this assemblage is interpreted as being derived from the crystalline rocks that form the Deseado Massif. The quartzose petrofacies is composed of monocrystalline quartz with scarce contributions of metamorphic clasts and traces of volcanic fragments; the provenance area is ascribed to sedimentary terrains, which most likely covered part of the Deseado Massif. The volcanic-sedimentary petrofacies is comprised of volcanic (acidic and intermediate rocks) and sedimentary (sandstone and mudstone) clasts, with discrete amounts of quartz grains with idiomorph shapes and embayments. This assemblage may correspond to material supply from the Devonian-Early Carboniferous accretionary complex developed in Chile or the unroofing of the western volcanic arc located in the central part of Patagonia. The validity of the three defined petrofacies was evaluated using Principal Component Analysis and triangular compositional diagrams; both methods show good separation and lack of overlap between the three petrofacies. Major (Si, Al, Fe, Na, K) and trace-REE elements (Zr, Th, Sc, Hf) were used to improve the petrographic information. The relation SiO2 against K2O/Na2O indicates that the Pampa de Tepuel and the Moj´on de Hierro formations correspond to a passive margin, while the Valle Chico and Río Genoa formations represent different types of active continental margins. The Th/Sc and Zr/Sc ratios and the Th-Hf-Co distributions indicate that the sandstones of the Tepuel Group were formed from rocks compatibles with the average composition of the upper continental crust. 

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