227 / 2019-06-28 11:26:14

Geologic Age of the Lower Part of Taiyuan Formation in Western Henan Province

Conodont,Gzelian stage,Late Carboniferous,Western Henan Province

The late Paleozoic Taiyuan Formation in Henan Province is mainly composed of a mixture of shallow marine carbonate and terrigenous clastic deposits. Whether its basal limestones are of Permian or late Pennsylvanian is a long-standing question unresolved, for the lack of marine fossils with biostratigraphic significances. Recently, four genera and 12 species conodonts was collected in lower part of Taiyuan Formation, they are Idignathodus hebeiensis, I. delicatus, I. tersus, I. antiquus, Idignathodus sp., Lochdus sp., Hindeadella sp., Streptognathodus elegantulus, S. elongatus, S. gracilis, S. wabaunsensis, S. nodulinearis. We tend to established Streptognathodus elegantulus - Idignathodus hebeiensis assemblage in first limestone layer of Taiyuan Formation in northern Henan Province, Streptognathodus elongatus - S. wabaunsensis assemblage in lower part of Taiyuan Formation in southcentral Henan Province. Combined with zircon age from volcanic tuff in lowest Taiyuan Formation shows peaks at 304 Ma, these conodonts assemblage suggest the lower part of Taiyuan Formation should be assigned to Gzelian stage of late Pennsylvanian. Streptognathodus elegantulus - Idignathodus hebeiensis assemblage has been reported from north western Shanxi Province and Hebei Province in northern North China, but this is the first report from the southern North China. This biostratigraphic age is important to reconstruct the late Paleozoic paleogeography for North China and understand the sea-level variation in low-latitudes related to the activity of the high-latitude Gondwanan glaciation.