鄂西北上震旦统灯影组沉积相及构造古地理

湖北省丹江口、谷城、郧县及邻区河南浙川等地广泛分布的灯影组碳酸盐岩,几乎均系较深水或深水环境下的产物。按照沉积作用特征将其分为6种成因类型,即重力流沉积、滑坡滑塌沉积、较深水静水沉积)。浅水机械沉积和生物沉积（藻）碳酸盐岩及少量陆源碎屑岩。它们组成了5种不同的剖面结构（岩相序列）。根据各种类型剖面的空间分布对灯影期沉积古地理进行了恢复。该区在灯影期系一总体呈北西向延伸的被动大陆边缘,西北部发育藻礁沉积,推测北部淅川附近存在碳酸盐水下高地。

SEDI MENTARY FACIES AND TECTONO-PALEOG EOGRAPHY OF THE LATE SINIAN DENGYING FORMATION IN NORTHWESTERN HUBEI

The Late Sinian Dengying Formation, extensively distributed in northwestern Flubei (Gucheng. Danjiangkou and Yunxian) and the adjacent Xichuan area of southwestern Henan. is mainly composed of deep-water carbonate rocks with intercalations of terrigenous elastics and include six genetic types, (l) Carbonate gravity flow deposits(dominantly of carbonate turbidites), (2) carbonate olistostromes including slides and slumps, (3) deep- and static-water carbonates, (1) shallow water carbonates, (5) algal carbonates and (6) terrigenous elastics. The characteristics of carbonate turbidites can be well compared with those of typical turbidity current deposits in sedimentary structures, sequence and grain size distribution. Q-mode cluster analysis of trace elements indicates a distinct difference between carbonate turbidites and associated deep- and static-water carbonate rocks. Five sequence pattern types may bediscerned in-the stratigraphic sections at different localities within the region through field and laboratory studies. Based on the sedimentary environments represented by the sequence patterns and on their spacial distribution, an outline paleo-geographic reconstruction is made. The slope or ramp facies is distributed in the tract from Gucheng to Anyangkou trending NW-SE, which becomes more complicated northwestward. Along the line f-rom Danjiangkou to Xijiadian through Liangshuihe exists the base-of slope apron facies, to the northeast of which occurs the basin facies. There occur the shallow water and reef facies in Nanhur tang area, probably with surrounding reef slope facies. In Xichuan, Henan there may have been a submerged carbonate highland. The Dengying Formation of northwestern Hubei and southwestern Henan belongs to a transitional to mobile sedimentation type, contrasting sharply with the stable epicontinental sea type within the Yangtze platform in the south.The tectonic setting under which the Dengying Formation was deposited was a northeasterly inclined complicated passive continental margin with a NW-SE trend.