摘要
豫西前寒武纪汝阳群是一套主要由潮汐和风暴所影响的滨岸和内陆棚碎屑沉积.整个沉积序列由九种主要岩相组成,即粗砂岩/砾岩相(F_1),槽状交错层砂岩相(F_2),复合交错层砂岩相(F_3),巨型板状交错层砂岩相(F_4),丘状交错层砂岩相(F_5),平坦层状砂岩相(F_6),低角度交错层砂岩相(F_7),互层泥岩/砂岩相(F_8)和水道沉积(F_9).这些不同的岩相可构成三种典型的相组合,即潮汐影响的相组合(A_1),风暴影响的相组合(A_2),和潮汐/风暴结合影响的相组合(A_3).其中A_1主要发育在云梦山组和白草坪组,A_2构成北大尖组的大部分,而A_3则在云梦山组和北大尖组都有出现.文中详细讨论了各种相的形成过程,并且强调了由潮汐形成的沙浪沉积.
Ruyang Group, consisting of the Yunmengshan, Baicaoping and Beidajian formations in an sacend-ing order, is the first sedimentary sequence overlying the Precambrian volcanic rocks in western Henan, which is geologically situated on the southern margin of North China Platform. Detailed facies and facies association analyses show that Ruyang Group was formed in tide- and storm-influenced coastal and inner shelf environments. The group can be divided into nine main facies coarse-grained sandstone / conglomerate (F1), trough crossbedded sandstone (F2), compound crossbedded snadstone (F3), giant planar crossbedded sandstone (F4) , hummocky cross- stratified sandstone (F5) , flat bedded sandstone (F6), low-angle crossbedded sandstone (F7), interbedded sandstone / mudstone (F8) and channel deposits facies (F9) .
F1 was once presumably fouvial products but further reworked into coastal conglomerats and coarse-grained sandstonesl. F2, F3, F4 and F8 are clearly related to tide, and they were formed by means of migration of tide-generated megaripples and sandwaves in the subtidal zones, while F8 is intertidal de- posit. F . F, and F are storm-influenced facies. F5 evidently formed under combined unidirectional and oscilatory currents. Most of F6 represents the shallow marine turbidites with Bouma sequence-like structures and often inierlayered with F The rest portion of F6 with symmetuic wave marks on the bedding is inter-preted as shoal deposits above fairweather wave base. F7 is also generated undrr combined flow condition but unlike F5 it is structured mostly by swaley cross-stratifications. F9 is further divided into two types. The small-scale and often mutually -cut channels are suggested to be tidal channels in sub- and inter-tidal while the large-scale channels may be the tidal inlets, a barrier island is inferred on the basis of as-seciation. of tidal inlets, spit or beachface deposits with well-developed wash bedding and washover depos-
Three kinds of facies associations are recongnized. Tide-infl
出处
《沉积学报》
CAS
CSCD
北大核心
1992年第1期57-67,共11页
Acta Sedimentologica Sinica
