再论塔里木盆地库车坳陷三叠纪—侏罗纪的海泛事件

Rediscussion on the Sea-slooding Events During Triassic to Jurassic of Kuqa Depression in Tarim Basin

多年来的油气源对比表明,塔里木盆地库车坳陷的油气来源于三叠系—侏罗系的湖相、湖沼相烃源岩,因而探讨三叠纪—侏罗纪湖盆曾否遭受过特提斯洋海水的海泛,不仅对古地理重建,而且对烃源岩及其生油气潜力评价都具有重要的意义。笔者在该坳陷三叠系—侏罗系湖相烃源岩的生烃母质中发现了大量的各类底栖宏观藻类化石,并获得了沉积地球化学证据。据此,并结合区域古构造-古地貌演变与全球、大区域海平面升降规律的综合判断,初步认为库车坳陷在三叠纪—侏罗纪曾多次受到过特提斯洋短暂海泛的影响,其中规模最大的是晚三叠世黄山街期晚期、早侏罗世阳霞期晚期和中侏罗世恰克马克期。海泛的原因,可能与特提斯洋海平面升高和库车坳陷湖盆区—陆源区地势缓坦的联合作用有关。由于海泛改善了生烃母质类型,从而使海泛层段的源岩氢指数等表征生烃能力的指标有一定提高。

Compare the characters of biomarkers in the oil, gas with that in source rocks demonstrates that the oil and gas of Kuqa depression, Tarim Basin, are derived from Triassic-Jurassic lacustrine and limnogenic source rocks. Whether the sea-flooding from tethys sea occurred in this area during Triassic to Jurassic is important to paleogeographic reconstruction and the comment to make upon the source rocks and potential of oil and gas generation. During the time of Ninth Five years Science and Technology development project of China abundant various benthonic macroalgae fossils discovered from the lacustrine source rocks of Triassic to Jurassic and corresponding sedimentary geochemical evidence suggest that Kuqa Depression may be covered by marine water repeatedly and the duration of every sea-flooding was very short. The vastly spreaded sea-flooding events occurred in upper Huangshanjie Formation（T3）, upper Yangxia The causes of sea-flooding may be the sea-level rising with the Formation （J1）and Qiakemake Formation （J2）. paleogeographic panplain development during that time. Sea-flooding improves the characters of bioprecursors and rases the HI and other index of the generation of oil and gas.