THE MIDDLE-LATE DEVONIAN SEDIMENTARY MICROFACIES AND CONODONT BIOSTRATIGRAPHY IN THE SIHONGSHAN AND LALI SECTIONS,GUANGXI
The Middle-Upper Devonian carbonate rocks in South China are highly developed.However,systematic study on the carbonate microfacies is lacking.The Middle-Upper Devonian strata are developed continuously in the Sihongshan section in Du'an and the Lali section in Yizhou,Guangxi,SW China,and they are important reference sections of the Devonian system in South China.The Middle-Late Devonian in the Sihongshan section is a slope-basin facies,and in the Lali section is a platform-basin facies.In this paper,the Middle-Upper Devonian conodont biostratigraphy at the two sections was established,based on which the sedimentology of the carbonate microfacies was studied,the evolutionary course of the sedimentary environment in the same period was reconstructed,so as to provide a reliable basis for the regional comparison among different stratigraphic units.In the Givetian and Frasnian FZ1-FZ4,the Sihongshan section shows mainly siliceous limestone in the Fenshuiling Formation and calcareous mudstone in the"Liujiang Formation",while the Lali section exposes reef limestone in the Laoyefen Formation.In the Frasnian FZ5-FZ13,the Wuzhishan Formation was formed in both sections,presenting mainly micritic/nodular/mud-banded limestone with few large fossils due to the platform drowning in a transgression event that corresponds to the global Middlesex Event.In addition,a series of bio-events in the Middle-Late Devonian such as F-F event could be identified based on the population change of conodonts.
万方数据
维普
