中扬子台地及其南缘早奥陶世道保湾期生态地层

ECOSTRATIGRAPHY OF THE MIDDLE YANGTZE PLATFORM AND ITS SOUTHERN MARGIN DURING THE DAOBAOWANIAN (EARLY ORDOVICIAN)

关键词:  群落  生态相  奥陶纪  中扬子台地  华南古大陆边缘

Key words:  community  ecostratigraphic facies  Ordovician  Middle Yangtze platform  margins of South China oldland

摘要:

通过对中扬子台地及其南缘早奥陶世道保湾期生态地层的研究,划分出了7个生态相域,即:Batostoma-Calathium群落台地生物礁生态相域、Calathium-Archaeoscyphia群落台地生物礁生态相域、Sinorthis群落内陆棚生态相域、Cameroceras群落中-外陆棚生态相域、Endoceras群落深水斜坡生态相域、Tetragraptus群落盆地边缘生态相域、Didymograptus群落深水盆地生态相域。根据生态相域的组合特征,建立了4个生态相区和1个生态相体系。生态地层研究的结果揭示了中扬子台地及其南缘道保湾期的生态特征、古生物地理和古构造及沉积古地理等特征。

Abstract:

Seven ecostratigraphic facies tracts (EFT) have been distinguished,for the Daobaowa-nian ecostratigraphy of the Middle Yangtze platform and its southern margin.They are:(1)Batostoma-Calathium platform organic reef ecostratigraphic facies tract,characterized by benthic reef-building communities;(2)Calathium-Archaeoscyphia platform organic reef ecostratigraphic facies tract;(3)Sinorthis inner shelf ecostratigraphic facies tract;(4)Came-roceras mid-outer shelf ecostratigraphic facies tract characterized by nektonic organisms; (5)Endoceras deep-water slope ecostratigraphic facies tract also characterized by nektonic organisms;(6)Tetragraptus basin-margin ecostratigraphic facies tract characterized by planktonic organisms,and (7)Didymograptus deep-sea basin ecostratigaphic facies tract characterized by planktonic organisms as well.According to the assemblages of ecostrati-graphic facies tracts,four ecostratigraphic facies regions have also been established.(1) Batostoma-Calathium and Calathium-Archaeoscyphia platform organic reef ecostratigraphic facies region;(2)Sinorthis and Cameroceras shelf ecostratigraphic facies region dominated by benthic and nektonic organisms;(3)Endoceras deep-water slope ecostratigraphic facies region including the transitional-type organisms,and (4)Tetragraptus and Didymograptus deep-water basin ecostratigraphic facies region composed of the Jiangnan-type organisms, all of which are arranged into one ecostratigraphic facies system,i.e.BCA,SC,E and TD platform-shelf-slope-basin ecostratigraphic facies system,The results of research on ecos-tratigraphy in this paper have disclosed the ecological,palaeobiogeographic,tectono-paiaeo-geographic,sedimentary facies and palaeogeographic characteristics of the study area dur-ing the Daobaowanian(Early Ordovician).