Middle Triassic lake deepening in the Ordos Basin of North China linked with global sea-level rise

Jin, Xin; Baranyi, Viktória; Caggiati, Marcello; Franceschi, Marco; Wall, Corey J.; Liu, Guanglin; Schmitz, Mark D.; Gianolla, Piero; Ogg, James G.; Lu, Gang; Shi, Zhiqiang; Preto, Nereo

doi:10.1016/j.gloplacha.2021.103670

Cited by 22 publications

(8 citation statements)

References 83 publications

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“…It can be considered as the product of contemporary magmatic activity. The volcanic ages of three samples are consistent with the ages of igneous zircons as commonly observed in the Chang 7 and Chang 8 members (Wang et al, 2014;Zhang et al, 2014;Wang et al, 2017;Deng et al, 2018;Liu et al, 2018;Zhu and Cui, 2019;Jin et al, 2021). According to the detailed study of stratigraphy and paleontology, the sample An-2 was located at the bottom of Chang 7 Member and the MTG-1 was sampled at the top of Chang 8 Member.…”

Section: The Boundary Of Chang 7 and Chang 8 Memberssupporting

confidence: 83%

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Zircon U–Pb Dating of Tuff Layers in the Middle–Upper Triassic Strata of Successions and Sedimentation of Chang 7 Member in the Ordos Basin, China

Gou

Liu

et al. 2022

Front. Earth Sci.

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During the Late Triassic, the southern margin of the Ordos Basin was influenced by the Indosinian Movement, in response to closure of the Paleo-Tethys Ocean. Thinly bedded tuff layers are exposed near the base of the Middle–Upper Triassic formations (Chang 8/7/6 members) in the Ordos Basin. Tuff samples from drilling core (well An-35) and outcrop (Motiangou section) samples in the Yanchang Formation were studied by the detailed field work. Igneous zircon crystals were picked and analyzed by the instruments of cathodoluminescence and laser ablation inductively coupled plasma mass spectrometery (LA-ICP-MS). The timing of volcanic activity was determined by means of high-precision zircon age. Combining tectonic setting and paleogeographic reconstruct, the ages of tuff layers indicate that volcanic activities occurred at three peaks (241.6 ± 1.1 Ma, 240.2 ± 1.1 Ma, and 233.5 ± 1.2 Ma) from the top of Chang 8 Member to the Chang 7 Member. The results implied that the volcanic activities lasted from Ladinian to Carnian, as well as define the sedimentary duration of the Chang 7 Member with a deposition rate of 1.34 cm/ka.

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Section: The Boundary Of Chang 7 and Chang 8 Memberssupporting

confidence: 83%

“…U-Pb ages of volcanic zircons in the upper section of Chang 7 Member are between 234 Ma and 236 Ma . A recent CA-ID-TIMS dating (240.95 ± 0.03 Ma) was obtained on tuff layers in the lower section of Chang 7 Member (Jin et al, 2021). Even with the abundant data of the study area, the ages of initial volcanic activities are still in debate.…”

Section: Introductionmentioning

confidence: 99%

Zircon U–Pb Dating of Tuff Layers in the Middle–Upper Triassic Strata of Successions and Sedimentation of Chang 7 Member in the Ordos Basin, China

Gou

Liu

et al. 2022

Front. Earth Sci.

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“…Multiple hypotheses for Yanchang organic-rich shale include high primary productivity, , magmatic activity, , marine transgression, etc. Good correlations of TOC with various elements such as Mo, U, Re, Cu, etc.…”

Section: Discussionmentioning

confidence: 99%

“…Organic-rich deposition of the Triassic Yanchang Formation is likely to be controlled by a range of geological events (such as marine transgression, anoxia, algal bloom, volcanic eruptions, deep hydrothermal activity, etc. ). , The Triassic Yanchang Formation has developed the most important hydrocarbon-rich shale in central and western China. The shale at the Chang 7 member of the Upper Triassic Yanchang Formation has high total organic carbon (TOC).…”

Section: Introductionmentioning

confidence: 99%

Shift in the Mode of Carbon Cycling Recorded by Biomarkers and Carbon Isotopic Compositions in the Yanchang Formation, Ordos Basin: Autotrophy vs Heterotrophy

Liu

et al. 2023

ACS Omega

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Organic-rich shales and mudstones have long been investigated regarding the control of source, environment, climate, etc. on the enrichment of organic carbon. However, little is documented about how autotrophy and heterotrophy influence organic carbon cycling/export. Here, we show molecular and carbon isotopic compositional changes of the shale or mudstone source rocks from the Chang 3 to 7 members of the Yanchang Formation. The Chang 7 member source rocks have higher quality (480−500 mg/g) and total organic carbon (TOC) (15.3% on average) than other member source rocks; the sterane/hopane ratio and the δ 13 C of organic carbon and kerogen decrease from the Chang 3 to 7 members, but Δδ ([average δ 13 C of n-C 17 + n-C 18 ] − [average δ 13 C of pristane + phytane]) increases, and no aryl isoprenoids and C 40 aromatic carotenoids (e.g., isorenieratane) were observed. These low maturity biomarker features suggest that there were no water stratification, photic zone euxinia (PZE), and no obvious change in the organic matter source, and the water column is generally anoxic. A comparison of the δ 13 C of Pr and Ph with the δ 13 C of the n-C17 and n-C18 alkanes reveals a shift in the mode of carbon cycling/export (autotrophy versus heterotrophy) in the Yanchang Formation and that there was dominant heterotrophic bacterial activity or bacterial biomass in the Chang 7 member. The TOC spike in the Chang 7 member may result from boosted carbon cycling/export that improves organic carbon preservation than other members. Possible external forcings on the shift are abundant hydrothermal-or volcanic-derived metal salts as electron acceptors in the palaeowater, which is a reasonable explanation for enhanced heterotrophic bacterial activity. This finding improves our understanding of heterotrophic bacterial activity control on organic matter (OM) preservation and may be a significant supplement for understanding the ecological or environmental forcings in the Yanchang Formation, Ordos Basin.

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“…In general, it was characterized by a slightly negative δ 13 C and an evident negative anomaly δ 18 O. The δ 13 C V-PDB value of organic carbon in Chang 7 shale is −32‰ to −28‰ (Jin et al, 2021). This suggests that the carbon source of fibrous calcite is not related with the wall rock.…”

Section: Substance Sourcesmentioning

confidence: 96%

Genesis of Fibrous Calcite in the Chang 7 Member of the Yanchang Formation, Ordos Basin, China

LIU

et al. 2023

Acta Geologica Sinica (Eng)

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To explore the genesis of the laminated calcite veins developed in the black shale of Chang 73 submember of the Ordos Basin, the petrology, microstructure and geochemistry of calcite veins are studied using thin sections, fluid inclusions, trace elements and isotopic geochemistry. The source, the time of formation, the mechanism of formation, and the dynamic background of the veins are discussed. The veins are mostly made up of calcite, mixed with lenticular or spindle‐shape solid wall rock inclusions. Three structures are identified in the calcite minerals: fibrous, rhombic cleavage, and wedge‐like structure. Trace elements and isotopes of carbon and oxygen confirm that the calcite veins were formed from a high density hydrothermal fluid. It is assumed that calcite veins formed prior to wall rock consolidation during the formation of the Qinling Orogenic Belt in the Middle and Late Triassic. The results show that the sedimentary sources of Chang 73 submember were influenced by hydrothermal materials besides terrigenous detritus. The fibrous calcite is different from the fibrous calcite reported in the morphology and mechanism of formation. In this way, the research complements and improves the morphology and the mechanism of formation of fibrous calcite.

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Middle Triassic lake deepening in the Ordos Basin of North China linked with global sea-level rise

Cited by 22 publications

References 83 publications

Zircon U–Pb Dating of Tuff Layers in the Middle–Upper Triassic Strata of Successions and Sedimentation of Chang 7 Member in the Ordos Basin, China

Zircon U–Pb Dating of Tuff Layers in the Middle–Upper Triassic Strata of Successions and Sedimentation of Chang 7 Member in the Ordos Basin, China

Shift in the Mode of Carbon Cycling Recorded by Biomarkers and Carbon Isotopic Compositions in the Yanchang Formation, Ordos Basin: Autotrophy vs Heterotrophy

Genesis of Fibrous Calcite in the Chang 7 Member of the Yanchang Formation, Ordos Basin, China

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