Major, trace-elemental and sedimentological characterization of the upper Ordovician Wufeng-lower Silurian Longmaxi formations, Sichuan Basin, south China: Insights into the effect of relative sea-level fluctuations on organic matter accumulation in shales

Wei, Chenji; Dong, Tian; He, Zhiliang; He, Sheng; He, Qing; Yang, Rui; Guo, Xiaowen; Hou, Yuguang

doi:10.1016/j.marpetgeo.2021.104905

Cited by 30 publications

(21 citation statements)

References 80 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Through a comprehensive study on the redox conditions, paleoproductivity, input of terrigenous debris, and water mass restriction in the Wufeng-Longmaxi Formation of well N1, well ZY1, and well XY3, it is believed that the enrichment pattern of organic matter is a comprehensive dynamic process, which is not only controlled by the high primary productivity at the beginning but also controlled by the later preservation conditions. Therefore, based on the com-prehensive previous research and combined with the tectonic evolution, it is believed that the enrichment of organic matter in the study area is a differential enrichment model [62][63][64][65][66][67][68][69] (Figures 1 and 6). The Middle Ordovician-Early Silurian was the tectonic transition stage of the Upper Yangtze.…”

Section: Mechanism Of Organic Mattermentioning

confidence: 90%

“…Studies on the input of terrigenous materials in modern sedimentary basins show that terrigenous detrital mainly comes from rivers, volcanic eruptions, and biological remains. Elements such as Al and Ti are the main components of continental crust, and their contents 13 Geofluids are relatively low in the oceanic crust dominated by siliceous magnesia in that they are rarely affected during diagenesis [52], so the Al and Ti contents of sediments have been usually used as proxies for the input of terrigenous detritus (Rimmer, 2004;Tribovillard et al, 2006;Liu et al, 2019;He, 2020;Wei et al, 2021). In this time, the analysis of terrigenous debris input in the study area is mainly based on the Ti and Al and the ratio of Ti/Al.…”

Section: Terrigenous Influxmentioning

confidence: 99%

See 1 more Smart Citation

The Sedimentary Geochemical Characteristics and Geological Significance of the Wufeng-Longmaxi Formation Accumulation of Organic Matter Black Shale on the Southeastern Sichuan Basin, China

2022

Geofluids

View full text Add to dashboard Cite

At present, the understanding of the sedimentary paleoenvironment and organic matter enrichment law of black shale in the Wufeng-Longmaxi Formation is still insufficient. This time, we investigated the total organic carbon (TOC) content, X-ray diffraction mineralogical composition, and the major and trace element abundances of the newly recovered cores of three shale gas exploration wells in Changning, Qianjiang, and Xiushan areas which were, respectively, selected to discuss and compare the varying paleoenvironmental conditions and the factors that control organic matter accumulation, such as terrigenous input, redox conditions, primary productivity, and the degree of water retention in the basin. The results show that black siliceous shale lithofacies, gray-black shale lithofacies, gray-black silty shale lithofacies, gray argillaceous siltstone lithofacies, and gray shell marl lithofacies are mainly deposited in the Wufeng-Longmaxi Formation in the southeastern Sichuan Basin. Organic-rich black shale is mainly concentrated in the lower part of the Wufeng Formation and Longmaxi Formation. The continuous thickness of organic carbon content greater than 2% in the Changning area is 32 m, the continuous thickness in the Qianjiang area is 22 m, and the continuous thickness in the Xiushan area is 11 m. The hydrocarbon generation potential gradually weakens from west to east. The identification of the geochemical behavior characteristics of major and trace elements shows that enrichment of the organic matter black shale section in the Changning-Qianjiang-Xiushan areas is mainly formation in the anoxic-moderate water mass restriction environment with high primary productivity and less terrigenous detritus input under the low hydrodynamic conditions. However, the correlations of terrigenous detrital proxies Ti/Al, redox proxies V/Cr, Ni/Co, and paleoproductivity proxies Babio with the TOC contents show that the Changning area is a favorable area for the formation of organic-rich black shale and the Qianjiang area is affected by the Wuling underwater uplift; the thickness of the black shale deposits becomes thinner; the Xiushan area is adjacent to the Xuefeng uplift, and the deposition conditions of the accumulation of organic matter black shale deteriorate, which is unfavorable for shale gas exploration.

show abstract

Section: Mechanism Of Organic Mattermentioning

confidence: 90%

Section: Terrigenous Influxmentioning

confidence: 99%

The Sedimentary Geochemical Characteristics and Geological Significance of the Wufeng-Longmaxi Formation Accumulation of Organic Matter Black Shale on the Southeastern Sichuan Basin, China

2022

Geofluids

View full text Add to dashboard Cite

show abstract

“…Since aluminum (Al) and titanium (Ti) are not converted and immobile during diagenesis, these two elements are often used as proxies for detrital inputs [16,24,45]. In this study, the Al and Ti contents of Wufeng Formation samples range from 3.28% to 9.48% (avg.…”

Section: Discussionmentioning

confidence: 99%

“…Under reducing conditions, organic carbon is more conducive to preservation, 11 Geofluids while organic phosphorus content gradually decreases in the process of remineralization [56]. Therefore, C org /P is used as an index to evaluate redox conditions [16,58].…”

Section: Fluctuating Anoxic or Dysoxic Bottom Water Conditionsmentioning

confidence: 99%

“…Although deposition of OM enrichment shales from Wufeng and Longmaxi Formations has been extensively investigated in Sichuan Basin, the controlling factors for OM enrichment are still under debate. Some authors have suggested that the OM enrichment in Wufeng-Longmaxi samples is closely related to the productivity of OM, that is, to the primary production [15], whereas others have proved that the OM enrichment depends on its preservation conditions; that is, it is related to the anoxic bottom water conditions [16][17][18]. Besides, the geological events (e.g., volcanic activity and glacial period) may also play a crucial role in OM enrichment owing to anoxic water conditions and/or weathering input of nutrient caused by volcanism [19].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Geochemical Characteristics and Organic Matter Accumulation of Wufeng-Longmaxi Shales in the Southeast of the Sichuan Basin of South China

et al. 2022

View full text Add to dashboard Cite

The Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation black shales are the critical targets for shale gas exploration in the Sichuan Basin of South China. The enrichment of organic matter (OM) in shale is the basis for the generation of large-scale shale gas; however, its controlling factors in Wufeng-Longmaxi shales are still under debate, and few studies have focused on the edge of the Sichuan Basin. Based on the mineral composition, total organic carbon (TOC), and systematic inorganic geochemistry analysis of 72 core samples from Wufeng and Longmaxi formations in Well Xike 1, southeastern Sichuan Basin, the sedimentary conditions (palaeoclimate, palaeoredox, and palaeoproductivity) were reconstructed, and the controlling factors of OM enrichment were identified. The mineral compositions are dominated by quartz, clay minerals, calcite, and feldspar, associated with minor dolomite, pyrite, and anhydrite. The TOC contents (0.31%-6.84%, avg. 2.22%) show an upward decreasing trend from the Wufeng Formation to Longmaxi Formation. The chemical index of alteration (CIA) ranges from 65 to 71 (avg. 69), indicating warm and humid climate with moderate weathering. The diagrams of Al2O3-TiO2, TiO2-Zr, Zr/Sc-Th/Sc, La/Th-Hf, and La-Th-Sc jointly indicate the contribution from felsic and intermediate rock weathering. The P/Al, Cu/Al, and Ni/Al ratios suggest that marine paleoproductivity was relatively high in the Wufeng Formation and relatively low to moderate in the Longmaxi Formation. The V/Cr, V/Sc, U/Th, MoEF/UEF, and Corg/P ratios indicate that the bottom water was anoxic during the Wufeng Formation deposition and then fluctuating dysoxic and/or oxic in the overlying Longmaxi Formation. The TOC content was positively correlated with productivity proxies (P/Al, Cu/Al, and Ni/Al) as well as redox proxies (U/Th, V/Cr, MoEF/UEF, and Corg/P), indicating that the OM accumulation in Wufeng-Longmaxi shales is mainly controlled by high productivity and anoxic bottom water conditions.

show abstract

Clumped isotope thermometry reveals diagenetic origin of the dolomite layer within late Ordovician black shale of the Guanyinqiao Bed (SW China)

Müller

Zhao

et al. 2022

Chemical Geology

View full text Add to dashboard Cite

Major, trace-elemental and sedimentological characterization of the upper Ordovician Wufeng-lower Silurian Longmaxi formations, Sichuan Basin, south China: Insights into the effect of relative sea-level fluctuations on organic matter accumulation in shales

Cited by 30 publications

References 80 publications

The Sedimentary Geochemical Characteristics and Geological Significance of the Wufeng-Longmaxi Formation Accumulation of Organic Matter Black Shale on the Southeastern Sichuan Basin, China

The Sedimentary Geochemical Characteristics and Geological Significance of the Wufeng-Longmaxi Formation Accumulation of Organic Matter Black Shale on the Southeastern Sichuan Basin, China

Geochemical Characteristics and Organic Matter Accumulation of Wufeng-Longmaxi Shales in the Southeast of the Sichuan Basin of South China

Clumped isotope thermometry reveals diagenetic origin of the dolomite layer within late Ordovician black shale of the Guanyinqiao Bed (SW China)

Contact Info

Product

Resources

About