DISCOVERY AND SIGNIFICANCE OF TIDAL FLAT SEDIMENTS IN CARBONIFEROUS HUYOUFANG FORMATION IN SHANGCHENG AREA, HENAN

Based on analysis about the sedimentologic characteristics, mudstone B-Ga-Rb contents and paleoecology, the authors found that the middle Carboniferous Huyoufang Fm. distributed in Shangcheng area, Henan is a typical tidal flat sedimentary series. The prograding and retrograding sequences with common thickness between 10 and 30m can be found on the outcrop, in which the main subfacies is tidal channel, intertidal flat and supratidal mud flat. Huyoufang Fm. Consists mainly of sediments of Carboniferous sequence in Shangcheng area, and may represent the marginal remnant marine sediments formed in the unified Hefei-Beihuaiyang Carboniferous-Permian retroarc foreland basin located in the south margin of North China Plate. So the authors predict that the corresponding strata buried under the south part of Feizhong fault in Hefei basin could be predominantly shallow shelf sediments, and dark mudstones with potential hydrocarbon generation could probably be developed in the strata. Regional stratigraphic correlation shows that Erlangping-Xinyang-Waimiao-Liu'an fault belt is the suture between North China Plate and north Qinling-north Dabie island arc from late Caledonian to early Hercynian, and Shang-Dan Caledonian suture may extend eastwards at least to the south of Fuziling Group distributed in Beihuaiyang.