山东济阳坳陷古近系沙河街组深水湖沉积中的遗迹化石

山东济阳坳陷古近系沙河街组深水湖沉积地层主要由深灰色、褐灰色泥岩、油泥岩、泥灰岩和石灰岩以及岩盐组成,浊流沉积发育。已发现深水型遗迹化石有12个遗迹属14个遗迹种,包括3个新遗迹属6个新遗迹种。根据这些遗迹化石的组成与分布特征及其围岩的沉积特征,可以划分出2种不同沉积环境下的遗迹化石群落,即(1)Mermoides-Neonereites遗迹群落,主要由觅食迹(Fodinichnia)和牧食迹(Pascichnia)组成,常见分子有Mermoides chezhenensis,Mermoides latiusculus,Neonereites uniserialis,Hel minthoidichnitescf.tenuis,Hel-minthopsis abeli,Pilichnus lacustris,Multilagueichnus lingpanensis,Cochlichnus anguineus,Gordiaichnosp.,Palaeophycus tubularis和Planolites beverleyensis等,它们被解释形成于半深水湖或较深水湖沉积环境;(2)Semi-rotundichnus遗迹群落,以半圆形、小碟形牧食迹为其特征,典型组成分子有Semirotundichnus dongyingensis,Pa-tellarisichnus boxingensis和Neonereites uniserialis等,它们均产生于深水湖沉积环境。

TRACE FOSSILS OF DEEPER LACUSTRINE DEPOSITS IN THE PALEOGENE SHAHEJIE FORMATION OF JIYANG DEPRESSION,SHANDONG PROVINCE, EASTERN CHINA

The Paleogene Shahejie Formation of Jiyang Depression , Shandong Province,Eastern China, contains dark and brown grey mudstone, oil-bearing mudstone, marl, limestone and rock salt, in which 12 ichnogenus(including 3 new ichnogenus) and 14 ichnospecies(including 6 new ichnospecies) were discovered in the deeper water lacustrine deposits. According to the composition and distribution characteristics of these trace fossils and their country rock features, two types of ichnocoenosis under different sedimentary environments have been recognized as follows: 1)Mermoides-Neonereites ichnocoenosis,which mainly consists of Fodinichnia and Pascichnia including such common trace fossils as Mermoides chezhenensis ,Mermoides latiusculus ,Neonereites uniserialis,Helminthoidichnites cf.tenuis,Helminthopsis abeli,Multilagueichnus lingpanensis,Pilichnus lacustris,Cochlichnus anguineus,Gordia ichnosp. and Planolites beverleyensis,generates in mid-deep lacustrine sedimentary environment;and(2)Semirotundichnus ichnocoenosis,which is characterized by the semi-round and small dishing Pascichnia containing such representative trace fossils as Semirotundichnus dongyingensis, Patellarisichnus boxingensis and Neonereites uniserialis,forms in deep lacustrine sedimentary environment.