河南商城地区石炭系胡油坊组潮坪沉积组合的发现及意义

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

通过对河南省商城地区出露的中石炭统胡油坊组的沉积特征研究、微量元素分析并结合古生态分析,首次提出胡油坊组属于较为典型的潮坪沉积组合,分别发育了潮下—潮间—潮上的进积型与退积型沉积相序列,主要发育潮道、潮间带混合坪—泥坪及潮上带沼泽亚相。胡油坊组是河南商城地区石炭系的主体部分,属于华北板块南缘合肥—北淮阳石炭-二叠纪弧后前陆盆地残留海相沉积;预测合肥盆地肥中断裂以南下伏相当层位应以浅海陆棚相为主,可能发育了较好生烃条件的暗色泥岩。综合分析认为,二郎坪—信阳—歪庙—六安断裂带是加里东晚期—海西早期北秦岭—北大别岛弧与华北陆块的碰撞缝合带,商丹加里东缝合带向东的延伸位置至少应该在北淮阳佛子岭群分布区以南。

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.