东濮凹陷沙河街组(古近纪)植物活动痕迹类型及其环境与层序地层学意义

植物活动痕迹即根迹,是层序地层学中识别低位期沉积的重要标志。东濮凹陷沙河街组(古近纪)根迹发育,形态各异,可分为A、B、C、D、E五种类型,分别被解释为五类次级沉积环境下的产物。其中A型根迹、B型根迹与河口湾沉积环境相关,前者见于河口湾陆方一侧的河口沙坝(bay head bar),后者则出现于海方一侧易受海浪冲蚀的盐碱凹地。已有资料证明,植物活动痕迹,结合动物活动痕迹和古生物学、沉积学研究,可为判别河口湾沉积环境、层序界面提供重要实据,从而在层序地层学研究和储层沉积环境探索中显示重要作用。

FEATURES OF PLANT TRACE FOSSILS DISCOVERED FROM THE SHAHEJIE FORMATION (PALAEOGENE),DONGPU DEPRESSION AND ITS SIGNIFICANCE IN THE ENVIRONMENTS AND SEQUENCE STRATIGRAPHY

It is believed by palaeontologits that plant trace fossils(or rhizoliths) are very important indicators for discerning lowstand period in sequence stratigraphy and diagnosing past water table fluctuation in facies analysis.The well developed plant trace fossils found in Shahejie Formation of Dongpu Depression are first documented in detail,and this is therefore an important discovery in palaeontological history of China.In this paper,the forming environments are assumed to cope with the five types of plant trace fossils recognized.In determining esturarine environment and sequence surface boundary,recognition of plant trace fossils is thought to be an useful tool,and it is extremely emphasized here in terms of sequence stratigraphy and reservoir sedimentology.