湖北京山地区大隆组沉积特征与烃源岩的关系

湖北京山大隆组出露甚好,根据沉积特征,该组为一套海退序列的沉积,其下部沉积环境为外陆棚沉积,上部沉积环境为内陆棚沉积。由于外陆棚紧靠大陆坡,极易发育上升洋流。处于这样的海退时期,带来了生物群的更新,由早期的放射虫变为大量藻孢子,无疑为高有机质、高生产力来源打下了良好的基础,极有利于京山大隆组广阔范围内优质、优良质烃源岩的发育。

Sedimentary characteristics and their bearings to the source rocks in the Dalong Formation, Jingshan region, Hubei

The Dalong Formation crops out very well as a succession of regressive deposits in the Jingshan region, Hubei. The Formation may be divided, according to sedimentary characteristics, into the outer shelf deposits in the lower part and inner shelf deposits in the upper part. Due to slow regression, the shallow-water organisms especially algae appear massively in the upper part of the Dalong Formation, where the organic matter contents are much higher in the upper part than in the lower part. The frequently upwelling oceanic currents close to the continental slope brought about not only abundant algal spores, a source of high organic matter contents and high productivity, but also more nutrients from the bottom to the surficial waters for the variability of the organisms. The factors cited above are interpreted to be favourable for the formation of the excellent source rocks in the Dalong Formation.