塔中早—中奥陶世斜坡刻画及勘探

Slope Facies Depiction and Exploration of the Early-Middle Ordovician in Tazhong Area

基于岩石学、地球物理、地层学等岩相标志研究,识别并划分塔中地区奥陶系鹰山组跌积边缘型斜坡和沉积边缘型斜坡。跌积边缘型斜坡主要分布在塔中Ⅰ号坡折带中—东段,发育有滑动、滑塌成因的角砾岩和巨砾岩,缺乏正、逆粒序,无分选性,无定向性;沉积边缘型斜坡主要分布在中—西段,发育有岩屑流成因的角砾灰岩、浊流成因的泥粒岩,角砾灰岩呈中块状,分选性极差;泥粒岩底部具冲刷面构造,下部可见正粒序,向上过渡为平行纹层或水平纹层,发育有不完整的鲍马序列。不同斜坡类型控制的台地边缘相带差异性表现为:前者水体浅,相带窄,镶边明显,礁滩成群成带分布,垂向加积作用明显;后者水体较深,相带宽,弱镶边,以丘滩为主。

Based on petrology,geophysics,stratigraphy,this paper aims to identify and classify the bypass margins slope,sedimentary margins slope in Ordovician Yingshan Formation in the Tazhong area.The former mainly distributes in the middle-eastern part of No.1 slope break belt,developing the breccias and the giant conglomerates by sliding and slump,lacking positive and reverse order,sorting characteristics and directionality.While the latter mainly distributes in the middle-western part,developing brecciolas caused by lithic flow and packstones caused by turbidity current.The brecciolas is nongraded,and the packstones′bottom gets erodsion surface,with the lower part observant and upward transit to parallel laminae or horizontal laminae,developing the incomplete Bouma sequence.The difference of the platform edge controlled by the different types of the slope is that the former′s water body is shallow,with narrow facies belt,obvious rims,and the reef flats are distributed in groups,with obvious vertical accretion;the latter has deeper water body,with wide phase band and weak edge,mainly distributed in bioherm beach.