2026-10-10T09:24:54Z https://api.figshare.com/v2/oai

oai:figshare.com:article/34018281 2026-09-28T19:07:45Z category_4 category_14 category_21 category_272 category_873 category_39 category_734 category_61 category_69 portal_63 item_type_6 month_year_09_2026

Palaeoenvironment and Productivity-Driven Organic Matter Enrichment in the Upper Permian Dalong Formation Shales, Northeastern Sichuan Basin Xue Chen (127892) Longfei Lu (12522019) Zongquan Hu (21670674) Wangwei Liu (25133106) Weixin Liu (519888) Chencheng He (25133109) Biochemistry Molecular Biology Biotechnology Environmental Sciences not elsewhere classified Chemical Sciences not elsewhere classified Ecology Biological Sciences not elsewhere classified Developmental Biology Inorganic Chemistry widespread siliceous shales wells leba b organic matter enrichment limited terrigenous input hydrothermal inputs may available geochemical evidence northeastern sichuan basin evaluate palaeoenvironmental conditions toc contents vary sensitive trace metals episodic seawater exchange xs </ sub 3 </ sub 2 </ sub lbb ), heba elevated marine productivity tethyan seawater hba ), episodic inflow basin setting reducing conditions yuanba c studied samples rich palaeo restricted intrashelf relative roles rb values primarily controlled positive correlations occurred locally negative sio mainly driven low cia excess silica especially ni dominant controls dalong formation controlled preservation 40 wt The Upper Permian Dalong Formation in the northeastern Sichuan Basin contains organic-rich siliceous shales deposited in the Kaijiang–Liangping Trough, but the relative roles of productivity, redox conditions, and nutrient supply in organic matter enrichment remain debated. This study integrates total organic carbon (TOC), petrographic observations, major-element, and trace-element data from wells Leba B (LBB), Heba A (HBA), and Yuanba C (YBC) to evaluate palaeoenvironmental conditions and organic matter enrichment mechanisms. TOC contents vary from 0.40 wt % to 20.78 wt %, indicating spatially heterogeneous organic matter accumulation. Low CIA and Ga/Rb values in most LBB and HBA samples suggest relatively weak chemical weathering and limited terrigenous input. Redox-sensitive element patterns indicate that the studied Dalong Formation succession experienced fluctuating redox conditions, ranging from oxic to anoxic–sulfidic conditions. Mo–TOC relationships further suggest a semi-restricted intrashelf-basin setting with episodic seawater exchange. The widespread siliceous shales, excess silica, negative SiO₂–Al₂O₃ relationship, and abundant radiolarian remains indicate enhanced siliceous biological productivity. Positive correlations between TOC and productivity-sensitive trace metals, especially Ni_XS and Cu_XS, suggest that organic matter enrichment was mainly driven by elevated marine productivity. Volcanic and hydrothermal inputs may have occurred locally or episodically, but the available geochemical evidence does not support them as dominant controls in most studied samples. Overall, organic matter enrichment in the Dalong Formation was primarily controlled by productivity, further modulated by redox-controlled preservation, and sustained by a combination of limited terrigenous nutrient input, episodic inflow of nutrient-rich Palaeo-Tethyan seawater, and possible internal phosphorus recycling under reducing conditions. 2026-09-28T00:00:00Z Text Journal contribution 10.1021/acsearthspacechem.6c00149.s001 https://figshare.com/articles/journal_contribution/Palaeoenvironment_and_Productivity-Driven_Organic_Matter_Enrichment_in_the_Upper_Permian_Dalong_Formation_Shales_Northeastern_Sichuan_Basin/34018281 CC BY-NC 4.0