摘要
本文记述了我国东海陆架盆地西南部早第三纪瓯江组和温州组的海相介形类化石13属18种,其中包括6新种及2未定种。瓯江组仅含Trachyleberis lobuculus Siddiqui及T.wnnzhouensisChen sp.nov.,其时代为早始新世,为浅海环境下的沉积;温州组下部产较多的介形类化石,有 Loxoconcha oujiangensis Liu,Buntonia lepida Chen sp.nov.及 Acanthocythereiswenzhouensis Yang sp.nov.等,其时代归中始新世,形成于热带及亚热带滨海至浅海较浅海域的环境;温州组上部含Cytherella assamensis Neale et Singh,Paijenborchella(Eopai-jenborchella sinensis Liu及Cytherelloidea symmetrica Chen sp.nov.等,其时代属中始新世,为亚热带浅—深海交替的环境。本区介形类动物群与印度及巴基斯坦始新世介形类动物群较为相近,反映出太平洋西部东海生物地理区的地方色彩。
The southwestern part of the East China Sea Shelf is one of the most import-ant areas for oil and gas exploration, with well-developed Early Tertiary marinestrata. Based on coring data, the Eocene rocks nearly 300m in thickness may bedivided into three formations, which, in ascending order, are the Oujiang Forma-tion, the Wenzhou Formation and the Pinghu Formation. They are cha?acterizedby elastic rocks intercalated with thin carbonate strata, yielding various fossils,such as foraminifers, calcareous nannoplanktons, dinoflagellates, ostraeodes andsporo-pollen. Oujiang Formation This formation with a thickness of 392.5m disconformablyoverlies the Paleocene Lingfeng Formation, and conformably underlies the MiddleEocene Wenzhou Formation. The lower part consists of sandstones intercalatedwith mudstones and carbonaceous mudstones, in which no ostracode fossils haveyet been found. The upper part is composed of grey mudstones intercalated withsiltstones, containing only a few ostracode fossils, such as Trachyleberis lobuculusSiddiqui and T. werzhouensis Chen sp. nov., the former being found from theLower Eocene of the Upper Rakhi Shale, Rakhi Nala Region, Pakistan, indicat-ing that the upper part of the Oujiang Formation seems to belong to the Early Eocene. Wenzhou Formation The formation with a thickness of 756.5m and conform-ably underlies the Upper Eocene Pinghu Formation, may be divided into threeparts. Lower part This part consists of grey mudstones and bioclastic limestones,containing the ostracode fossils Loxoconcha oujiangensis Liu, Buntonia lepida Chensp. nov., Acanthocythereis wenzhouensis Yang sp. nov., Actinocythereis donghaiensisLiu, Caudites? acrocaudalis (Liu), Munseyella simplex Chen sp. nov., etc. Middle part It is mainly composed of pebbly sandstones, silty sandstones andsilty mudstones intercalated with thin bioclastie limestones and marls, in which noostraeode fossils have yet been found. Upper part It is made up of unequally interbedded grey to light grey mud-stones, silty mudstones and fine-grained sandstones from which have been obtainedthe ostracode fossils CythereUa assamensis Neale et Singh, Paijenborchella (Eopaijen-borchella) sinensis (Liu), P. (E.) opima (Liu), Cytherelloidea symmetrica Chen sp.nov., Neonesidea sp., etc. Among the above mentioned ostracode fossils obtained from the lower andupper parts of the Wenzhou Formation, Cytherella assamensis Neale et Singh (1985)occurs in the Middle Eocene part of the Sylhet Formation in the Deopani Regionof Assam, India; Acanthocythereis wenzhouensis Yang sp. nov. is very similar toA. pedigaster Siddiqui (1971), which is known to occur in the Upper Paleocene ofthe Rakhi Gaj Formation (lower part) in Pakistan, while other species resemblethose mainly found from the Eocene, Middle Eocene or Upper Eocene, etc. Sincethe ranges of these ostraeode fossils mainly belong to Eocene as well as to theage of the underlying Oujiang Formatiom, the Wenzhou Formation may be as-signed to Middle Eocene. Pinghu Formation This formation, 128m in thickness and unconformablyunderlying the Miocene strata, consists of grey mudstones and silty mudstonesin the lower part and light brown mudstones in the upper part, but so far noostraeode fossils have been found. Paleoecologically, neither the typical brackish genus JVeocyprideis, nor the abys-sal genera such as Krith, have been found, indicating that the Eocene fauna foundin this area excludes such environments. The main genera Of this fauna are Tra-chyleberis, Loxoconcha, Buntonia, Acanthocythereis, Actinocythereis, Caudites?, Munse-yella, Cytherella, Paijenborchella (Eopaijenborchella), Cytherelloidea, Neonesidea, etc.According to available ecological data of these known genera and their verticaldistribution in the strata, it can be recognized that the fauna was living in abenthonic environment with rather shallow sea water which gradually changed torather shallow alternating with rather deep sea water under a tropical andsubtropical climatic condition. In general aspect, the ostracode fauna in this area, although not of the same
出处
《微体古生物学报》
CSCD
北大核心
1990年第4期367-388,444-446,共22页
Acta Micropalaeontologica Sinica
