The Upper Carboniferous-Lower Permian Benxi Formation of Henan Province was deposited in an epicontinental sea environment, and developed a set of deposits of lagoon facies characterized by the alumina-ferrous mudstones bearing iron ore and bauxite, and tidal flat facies, restricted carbonate platform facies and sand bar ( barrier island) facies. Based on the isoline trend analyses of thickness of strata and carbonate rocks, the percentage of sandstone content, as well as distribution features of facies fossils, trace elements and deposit types, four types of lithofacies areas are divided, including the coastal lagoon mudstone lithofacies, lagoon-tidal flat sandstone and mudstone lithofacies, restricted platform carbonate and clastic rock lithofacies, and sand bar (barrier island) clastic rock lithofacies. The Late Carboniferous-Early Permian palaeotopographic feature of Henan Province displays a higher terrain in the south and the west, and a lower terrain in the north and the east, and exists a large palaeo-uplift area under water in the center zone, therefore, the spread of the sea over land is from southeast and northeast to west in this province; Old lands are located on the Funiu Mountain in southwestern Henan Province and Zhongtiao Mountain in western Henan Province. Therefore, sedimentary area extends from west to east in a fan shape and there are two sedimentary areas with the largest thickness of this formation that lie in the northeast and east of Henan Province. It is possible to infer that sediment source is mainly from the Zhongtiao Old Land.%河南省上石炭统一下二叠统本溪组沉积主要形成于陆表海环境,发育了一套以含铁矿和铝土矿的铁铝质泥岩为特色的潟湖相,间有潮坪、碳酸盐岩局限台地及砂坝(障壁岛)相沉积.基于地层厚度、碳酸盐岩厚度和砂岩含量等值线的变化趋势分析以及指相化石、微量元素的分布特征和沉积组合类型,可划分出4种岩相区,包括滨岸潟湖泥岩相区,潟湖一潮坪砂岩、泥岩相区,局限台地碳酸盐岩、碎屑岩相区和砂坝(障壁岛)碎屑岩相区.当时沉积古地理特征表现为:豫西南为伏牛古陆,豫西为中条古陆,受该两条古陆的控制,沉积区域呈向东撒开的扇形;总体地势呈南高北低,西高东低,中部有一较大水下隆起区;海水从南东和北东方向侵入河南并逐渐向西延伸;物源主要来自盆地西侧的中条古陆;沉积最大厚度区位于豫北和豫东两大区域.
展开▼
