湖南新北、湘潭等地区跳马涧组的遗迹化石及其沉积环境

TRACE FOSSILS AND THEIR SEDIMENTARY ENVIRONMENTS IN THE MIDDLE DEVONIAN TIAOMAJIAN FORMATION IN XINHUA AND XIANGTAN,HUNAN

摘要:

湖南跳马涧组的沉积环境曾有多人论及:湖南省地质局区测队(1980)认为在都厐岭岛东边湖南江华、新化等地为滨海沉积;湖南省区域地质志(湖南省地矿局,1989)持与区测队相同的观点;刘文均(1981)认为湘中泥盆系的沉积作用,是在一个三面为隆起区包围,海水由南西方向侵入的情况下开始的;柳祖汉(1984)认为跳马涧期海侵规模进一步扩大,湘中、湘南地区大部分处于陆源碎屑带(包括潮上带和潮间带的一部分)。上述作者都从宏观方面阐述了跳马涧组的沉积环境。

Abstract:

The trace fossils from the Middle Devonian Tiaomajian Formation in Xinhua and Xiangtan, Hunan were previously described and published(Zhang Xinping, 1991). They are referred to 15 ichnogenera and 21 ichnospecies, namely, Arenicolites hunauensis, Cochlichnus xinhuaensis, Cochlichnus luguanensis, Cochlichnus ichnosp., Chondrites Type B Osgood, Chondrites Type C Osgood, Gordia marina, Tinoichnus lineata, Monocraterion ichnosp., Phycodes pedum, Phycoles of. Phycodes of. pedun, Phycodes of. pal, palaeophycus tabularis, Palaeophycus? cf. Curoatus, Planolites lererleyensis, Palaeiphycus montanus, Rouaultia ichnosp., Rhizocorallimn tongtianexsis, Rhizocralsimn ichnosp., Skoluhos linearis, Thallassinoides, Zoophycus aff. crassus, Zoophycus ichnosp.
They are mainly included in Arenicolides—Palaeophycus assemblage, Slolithos—Planolites assemblage, Palaeophycus—Gordia assemblage and Rhizocorallium—Planolites assemblage, all being located in the upper part of the Tiaomajian Formation, representing nearshore environments and belonging to Cruziam ichnofacies. Part of them may be included in Zoophycus—Skoluhos assemblage and Zoophycus —Cochlichnus assemblage belonging to Zoophycus ichnofacies, occurring in the uppermost part of the Tiaomajian Formation and representing offshore environments.
The author contends in this paper that there are 22 ichnogenera and 40 ichnospecies altogether recognized in the Tiaomajian Formation. They may be divided into 8 ethological and ecological types, namely Domuchuia, Fodinichnia, Repichnia, Cabichnia, Pasichuia, borings, escape traces and bioturbation structures. from bottom to top of the Tiaomajian Formation, the ichnoassemblage of Domuchuia is replaced by Domuchuia in combination with Fodichnia or Fodichnia, and Pascichnia accordingly, representing the sedimentary environments ranging from foreshore to nearshore, then to offshore, whereas the sea water deepens and becomes broader and broader.