摘要
本文描述了东海陆架盆地西南部W6-1-1井始新世海相沟鞭藻类24属36种(包括4新种),绿藻1属2种;论述了生物地层特征,建立了两个沟鞭藻组合并讨论了其地质时代、古环境及海侵海退等问题。东海陆架盆地始新统两个沟鞭藻组合基本上代表了一个大的海侵海退过程;海侵导致微体浮游植物的繁盛,并提供了较丰富的生油母质。文中提出下、中始新统的界线应置于温州组下部的灰岩与厚层泥岩之间,即瓯江组上部至温州组下部的灰岩应划归下始新统,温州组的其余地层应划归中始新统。
The Eocene sediments in the Continental Shelf Basin of the East China Sea,with a thickness of over 1000m, have been subdivided into three formations in as-cending order as Oujiang Formation, Wenzhou Formation and Pinghu Formation.The former two formations yield diverse and well-preserved marine dinocysts,microforaminiferal linings together with a small number of green algae such asthe genus Pterospermella. A total of more than 40 species belonging to 27 genera were discovered fromthe rock-cuttings of Hole W 6-1-1, located at 27°9′ N latitude and 122°8′ Elongitude, in the southwestern Shelf Basin. Thirty-six species belonging to 24 generaof dinoflagellates and two species of the genus PterospermeUa are illustrated inthis paper. Four new dinocyst species are established here, namely, Apteodiniumdonghaiense, Hystrichokolpoma wenzhouense, Spinidinium minor and Wilsonidium sub-tile, Based on the stratigrapbical ranges of the selected species as shown in Table1, two dinocyst assemblages can be recognized from the Upper part of the OujiangFormation to the Wenzhou Formation which in ascending order are as follows: 1. Kisselovia reticulata-Apteodinium donghaiense assemblage This assemblage, defined by the occurrence of Wetzeliellacean forms includ-ing the critical species Kisselovia reticulata, is found from the Upper Oujiang For-mation to the lower part (grey limestones intercalated with mudstones) of theLower Wenzhou Formation. It is characterized by the relative abundance of Wet-zeliellacean forms, but the Gonyaulacacean cysts are still more abundant thanthe Peridiniaceans. The important species are Apectodinium homomorphum, Apteo-dinium australiense, A. donghaiense sp. nov., A. rhombiforme, Cordosphaeridium ino-des, Deflandrea leptodermata, Fromea cf. chinensis, Glaphyrocysta intricata, Hystricho-kolpoma rigaudiae, Kisselovia reticulate, Membranophoridium aspinatum, Operculodiniumcentrocarpum, Polysphaeridium subtile, Pterodinium cingulatum subsp, granulatum,Rhombodinium sp., Spinidinium minor sp. nov., Spiniferites ramosus, Wetzeliella cf.articulate, Wilsonidium lineidentatum, W. subtile sp. nor.and W. tabulatum. According to the species with a restricted stratigraphical range worldwide andits correlation with the dinocyst assemblages of the Lower Eocene London Clayin southeastern England (Bujak et al., 1980), this assemblage (or the Upper Ou- jiang Formation to the lower part of the Lower Wenzhou Formation) is consid-ered to be of Early Eocene in age. The relatively abundant Wetzeliellacean formsand a high proportion of chorate cysts contained in this assemblage indicate awarmtemperate shallow sea--gulf environment. 2. Impagidinium dispertium-Horologinella incurvata assemblage This assemblage was mainly found from the upper part (grey thickbeddedmudstones) of the Lower Wenzhou Formation (with only a few species from theMiddle to Upper Wenzhou Formation) and is characterized by the absence ofWetzeliella, Kisselovia, Rhombodinium, Wilsonidium and the appearance of twelvespecies which are not recorded in Assemblage 1, including Achilleodinium biformo-ides, Horologinella incurvata, Hystrichokolpoma wenzhouense, Impagidinium dispertitum,Lacunodinium foveolata, Pterospermella eurypteris, P. australiensis, etc. Assemblage 2 is further characterized by the absolute predominance of Gony-aulacacean cysts such as Achilleodinium, Cordosphaeridium, Glaphyrocysta, Hystricho-kolpoma, Impagidinium, Lacunodinium. This assemblage (or the Wenzhou Format-ion excluding its lowermost part) is considered to be of Middle Eocene age. Thedinocysts and lithological evidence in the beginning of this period indicate a warm-temperate deep water condition of a normal shallow sea, suggesting that a strongtransgression might have occurred during early Middle Eocene in the East ChinaSea, and then a regression began in this region. It is possible that the two dinoflagellate assemblages from the Shelf Basin ofthe East China Sea represent a cycle from transgression to regression, i.e., Assem-blage 1 indicates the beginning of the transgression, and Assembl
出处
《微体古生物学报》
CSCD
北大核心
1990年第4期403-426,450-453,共24页
Acta Micropalaeontologica Sinica
