Discovery of cutinitic liptobiolith in northwestern China and a comparative study with Luquan Devoni

• 作 者: Daofu SONG Tieguan WANG Ningning ZHONG Yuan CHEN Dengfa HE Di LI
• 机 构: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing
• 出 处: 中国科学：地球科学（英文版）
• 发表日期: 2021年4期
• 关键词: NW China Devonian Cutinitic liptobiolith Coal petrology Biomarkers Coal-forming

Devonian cutinitic liptobiolith is a special cuticle-rich coal formed during the early stage of land plant evolution.In China,this special coal has previously only been reported in the Yangtze area,with the Luquan Devonian cutinitic liptobiolith of Yunnan Province being the most well-known.Recently,this type of coal was first discovered in the Bulonggoer Sag,to the northwest of the Junggar Basin,NW Xinjiang.Its geological age is regarded as the Givetian period of the late Middle Devonian,which is equivalent to the age of the Luquan Devonian coal.The cutinitic liptobiolith from NW Xinjiang has a distinct sheet-like texture resembling a stack of paper or leaf sheets in appearance,and so it is commonly called “paper coal” or“leaf coal”.Ribbonlike cutinite (thick-walled type) is the most abundant maceral in the coal (＞60％ and up to 80％,on a mineral-free basis),followed by ribbon-like collotelinite.The NW Xinjiang and Luquan cutinitic liptobioliths share similar maceral compositions;while their coal-forming plants and depositional conditions are distinct.The NW Xinjiang cutinitic liptobiolith was deposited in a regional fluvial or flood plain condition,with lycopsids as the dominant coal-forming plants.In contrast,the Luquan cutinitic liptobiolith formed in a coastal-lagoon environment,with primitive ferns as the predominant coal-forming plants,followed by lycopsids.The saturated fractions of the NW Xinjiang and Luquan liptobioliths are mainly composed of tetracyclic diterpanes.However,the tetracyclic diterpane compositions in the NW Xinjiang cutinitic liptobiolith are distinct from those in the Luquan Devonian coal:The former is dominated by atisanes and the latter is mainly composed of phyllocladanes.Different coal-forming plants may have contributed to the distinct tetracyclic diterpane compositions.