Palaeoenvironmental Evolution Based on Elemental Geochemistry of the Wufeng-Longmaxi Shales in Western Hubei, Middle Yangtze, China

The organic-rich shales found in the Wufeng–Longmaxi Formation are typically deposited oxygen-deficient reducing environments. One of primary sources debate revolves around question whether anoxic bottom water these is either euxinic or ferruginous, and this matter remains unresolved. Previous studies have mostly focused on as a whole order to understand key factors that control organic accumulation (OMA). However, research OMA for each member, including Wufeng (WF), lower Longmaxi (LLM), upper (ULM), has been insufficient. This paper aims investigate palaeoenvironmental conditions mechanisms western Hubei by integrating data total carbon (TOC) content, mineral compositions, major trace elements, iron speciation. results indicate were under highly restricted hydrographic conditions, except relatively open upwelling WF. Silica WF was primarily biogenic origin not hydrothermal. Ferruginous redox minor formations LLM conditions. Due tectonic uplift caused Kwangsian Orogeny LLM, palaeoenvironment characterized warmer wetter climate, high terrigenous influx, oxic low productivity result insufficient nutrients weak upwelling, leading turnover graptolite biozones from LM5 LM6. influencing changed vertically. TOC contents positive correlation with Al indicating influx main factor affecting WF, which significantly differed patterns other regions. suggests sedimentation rate higher than dilution during stage. combination while controlling ULM, resulting matter. Regions eastern Yiling block, close Qinling Ocean, show better prospects shale gas exploration. will further facilitate development area.