EARLY ORDOVICIAN CHITINOZOANS FROM THE HONGHUAYUAN FORMATION AND LOWER PART OF MEITAN FORMATION IN DATANGKOU OF CHENGKOU, CHONGQING
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Abstract:
Summary The Ordovician sequence is complete and well exposed at Datangkou of Chengkou County, Chongqing City. The investigation has been carried out on chitinozoans, together with the graptolites and conodonts, from the Honghuayuan Formation and the Yingpan Member of the Meitan Formation which represents the late Early Ordovician and early Middle Ordovician in the eastern Dabashan, belonging to the north Yangtze carbonate platform. For this study thirty-five chitinozoan samples were collected so that a stratigraphical control can be expected based on graptolite or conodont zones in this interval. Chitinozoans are lacking in eleven samples while in others are abundant but poorly diversified. A total of seventeen species, three new species (Conochitina datangkouensis sp. nov., C.wengxigouensis sp. nov., Rhabdochitina chenkouense sp. nov.) included, belonging to six genera have been described and figured. Among the key species recorded, the FAD of Lagenochitina esthonica, C. poumoti, C. brevis and ?Eremochitina brevis allow biostratigraphical correlation with graptolite zones of the same section and chitinozoan zones from Quebec, Bohemia, and south-eastern Europe. Yet, we must emphasize the absence of the typical Conochitina symmetrica which is unrecorded in the Honghuayuan Formation.
