鄂尔多斯盆地晚三叠世构造沉积响应

Sedimentary Response of Late Triassic Structures,Ordos Basin

对晚三叠世鄂尔多斯盆地延长组沉积前期、中期与末期3次大规模的构造活动及沉积响应进行了研究。延长组沉积前的早印支运动对湖盆形成及整个延长组的沉积奠定了基础;湖盆早期处于欠补偿状态,广泛发育冲积扇和河流相沉积;发生在长8末期的构造活动,使湖盆整体快速下降,发育了长7烃源岩,湖泊—三角洲沉积发育,沉积中心和沉积格局也发生了迁移和调整,直至湖盆沉积枯萎。延长组末期的印支运动使其地层遭受东西向抬升剥蚀,顶部地层剥蚀严重,形成高低起伏的早期侏罗纪古地貌;同时,上部延长组储层受大气淡水淋滤物性变好。

The late Triassic Yanchang Formation, Ordos Basin,experienced three large-scale tectonic movements during the early, middle and late sedimentary periods. In this paper,these movements and their sedimentary response are studied. The early Indo-China movement before Yanchang Formation’ s deposition is a basis for not only lake-basin formation but also whole Yanchang Formation’s deposition. The lake-basin in the early period was in a state of undercompensation and two sedimentary facies of both alluvial fan and fluvial might widely be found. And then,one movement during the end of Yanchang 8 Member made the whole lake-basin went down rapidly; and Yanchang 7 Member, a set of source rock,formed. Meanwhile,there was developed a lacustine-delatic deposition,and depocenter migrated and sedimentary pattern changed till the lake-basin deposition disappeared. During the end of Yanchang Formation, all strata uplifted and were erosive from an E-W trending by the Indo-China movement,especially for the top; furthermore, the early Jurassic landform with very various reliefs formed;at the same time,the petrophysical properties of upper Yanchang Formation became better due to fresh-water leaching.