Organic Geochemical Characteristics of Source Rocks of Hongshuizhuang Formation in the Mengjiawopu Section of Lingyuan-Ningcheng Basin in North China

Through the regional geological survey,outcrop section measurement and other field geological work,a block of black shale is found at the outcrop of Mengjiawopu Section of Hongshuizhuang Formation in Jixian County,and organic geochemical source rock analysis and evaluation methods are used to study the source rocks in Hongshuizhuang Formation.The set of source rocks is mainly gray-black silty mudstone and gray-black shale,with a cumulative thickness of 78 m;the total organic matter(TOC)is generally high,with an average content of 1.35%,of which good and rich source rock samples account for 86%.A combined analysis of the stable carbon isotope of kerogen,the correlation between Pr/nC17 and Ph/nC18,and the ratio of saturated hydrocarbon to aromatic hydrocarbon identifies that the organic matter is mainly TypeⅡkerogen;the equivalent vitrinite reflectance R o of organic matter is from 1.68%to 1.94%.R c,the correlation of the methylphenanthrene index(MPI)against the vitrinite reflectance is from 1.63%to 1.81%,with an average of 1.71%,and the Odd/Even Predominance(OEP)value is between 0.87 and 1.11,both indicating that the source rocks of the Hongshuizhuang Formation are at the stage of high to over maturation.In summary,the set of source rocks in Hongshuizhuang Formation is characterized by high organic matter content,good kerogen types,and high to over maturation stage.

火山磷供给推动中国北方中生代陆地生物繁荣

中国北方中生代热河生物群的生物量和生物多样性超过了同时期的其他陆地生物群,早白垩世热河生物群的辐射可能是对华北克拉通峰期破坏过程的响应,然而,克拉通破坏的深部过程和陆地生物群演化之间的内在联系尚不清楚。磷是生命所必需的营养元素,火山产物(包括熔岩和火山碎屑岩)中的磷可通过风化作用供给陆地生态系统。中国北方中生代连续的火山-沉积序列记录了火山磷供给、生物生产力和物种丰度的变化,为研究地球深部过程、火山作用与陆地生物群的协同演化提供了关键证据.火山磷供给与生物群演化之间的耦合关系表明,在华北克拉通峰期破坏期间,大量火山产物的风化作用为陆地生态系统供给了丰富的营养物质,创造了有利于热河生物群繁荣的陆地环境。与华北克拉通破坏初期相对应的侏罗纪燕辽生物群的演化也反映了上述火山-生物之间的耦合机制。