四川盆地西缘早三叠世早期碳酸盐重力流沉积与环境

四川竹园坝?梨园里地区下三叠统飞仙关组地层中,碳酸盐砾屑沉积类型有:碎屑流和浊流;根据岩性组合可分三种组合层序:Ⅰ.碎屑流与半深水泥晶灰岩沉积组合层序;Ⅱ.碎屑流与浊流沉积组合层序;Ⅲ.复合层序?据重力流形成环境,计算了古斜坡坡度,测定了古流向,结合重力流形成及古构造?古地理演化,提出了区内碳酸盐重力流的演化及沉积模式?

Sedimentology and Environment of Carbonate Gravity Flows on the Wester Margin of Lower Triassic. Sichuan Basin

Deposits of carbonate gtavity flows on the western margin of Lower Triassic Sichuan bsain may be divided into two perts:debris current and turbidity current.Debris current deposits mainly consist of four kinds of calcirudites with 1. horizontal structure (type A), 2. graded structure (type B), 3. disorder fabric (type C), 4. matrix supported(type D). Turbidity current deposits are composed of 1. calcarenite for low density current, 2. contain calcirudite calcarenite for high dentity current. Distribution frequency curves of carbonate gtavity flow deposits may be classified into four groups. It's importantly disscured differing from curves of debris and turibidity current and varying with their characteristic parameters.Assocaition sequences of gtavity flow sediments may show origin and evolution of gravity flow deposits. The association sequences are as follows: 1. association with debris flow deposits and micritic limestone in half -deep water environment. 2. association with cohesive debris current (type D) and turbulent debris current(type A B C). 3. association with debris current and turbidity current deposits. 4. complex association with calcilutite - debris current - turbidity current- calcilutite deposits.It's studied that paleo - slope is along northeast - southwest. It dipsfo the is southeast.direction of gravity flow is from northwest to southeast. Its slope angle is about 2- 9. Gravity flow deposits have linear distribution. It's non - water channel gravity flow deposits controlled by a marginal growth fault on the background of plateform geosyncline.