柴达木侏罗系的构造层序及前陆盆地演化

JURASSIC TECTONIC SEQUENCES OF QAIDAM AND FORELAND BASIN EVOLUTION

在柴达木盆地的侏罗系中，鉴别出了两种指示前陆盆地动力过程的构造层序：一种是响应于造山带逆冲加载过程的弹塑性转换沉降型构造层序；另一种是响应于基底塑性回沉过程的塑性回沉型构造层序。柴达木盆地的侏罗系共出现了８个构造层序：下侏罗统普林斯巴阶至中侏罗统巴柔阶４个弹塑性转换沉降型构造层序；中侏罗统巴通阶至卡洛阶下部２个塑性回沉型构造层序；中侏罗统卡洛阶上部和上侏罗统２个弹塑性转换沉降型构造层序。这种充填序列表明侏罗纪的柴达木盆地经历了多旋回弹塑性转换沉降、总体塑性回沉和再次弹塑性转换沉降３个演化阶段。此演化过程与同期造山带的隆升和向前陆带的逆冲加载过程密切相关。

Abstract On the basis of the studies on outcrop sedimentary section,well logs and organic geochemistry of Jurassic System,2 types of Jurassic tectonic sequences showing the dynamic processes of foreland basin are recognized in Qaidam Basin.One is the tectonic sequence converted from elastic to plastic subsidence corresponding to the thrusting and loading of orogenic belt,another one is plastic resubsiding tectonic sequence corresponding to the plastic subsidence of basin basement.Jurassic System of Qaidam Basin can be subdivided into 8 tectonic sequences,the succession from Pliensbachian to Bajoeian includes 4 tectonic subsequences of the first type;the succession of Bathonian lower Callovian includes 2 plastic resubsiding tectonic sequences;the succession of upper Callovian Upper Jurassic includes 2 tectonic sequences of the first type again.The total Jurassic fill succession of Qaidam indicates that the basin underwent 3 evolution stages such as multicycle converted elastic plastic subsidence stage,plastic resubsiding stage and converted elastic plastic subsidence stage again.This evolutional process of the basin is closely related to the thrusting and loading of orogenic belt toward foreland zone.