鄂尔多斯盆地上三叠统延长组负载构造类型及特征^*

Types and characteristics of load structures in the Upper Triassic Yanchang Formation,Ordos Basin

摘要

负载构造是一种重要的软沉积物变形构造类型,具有重力(密度差)作用是主要驱动力、变形发生在密度倒置的岩性界面等特征。根据变形构造与母体是否分离把负载构造分为3类: 一是未分离的负载构造,包括重荷(模)构造、火焰构造、枕状构造、水滴状构造及底辟(挤入)构造; 二是分离的负载构造,包括砂球(假结核)、砂球层、泥球; 三是复合型负载构造。在鄂尔多斯盆地上三叠统延长组岩心及露头中发现了大量的负载构造,通过对不同类型负载构造的特征描述、形成条件及触发机制分析,认为负载构造是地震和重力作用双重机制作用的结果,除了重力作用外,地震扰动是形成多种变形构造的主要原因,反映了鄂尔多斯盆地在晚三叠世印支期构造活动较强的特征。

Abstract

Load structures are known as an important type of soft sediment deformation structure,and are characterized by gravity(density difference)as the main driving force and deformation occurring at the lithologic interface with inverted density. According to whether the deformation structures are separated from the parent body,load structures can be divided into three categories including,non-separated load structures,separated load structures,and composite load structures. The non-separated load structures include heavy load(mold)structures,flame structures,water drop structures and diapir(extrusion)structures,and the separated load structures includes sand ball(false nodule),ball pillow layer and mud ball. A large number of load structures were recognized in the cores and outcrops of the Yanchang Formation of the Late Triassic in the Ordos Basin. Through the analysis of the characteristics,formation conditions and triggering mechanisms of different types of load structures,it is believed that the load structures were the result of the dual mechanisms of earthquakes and gravity. In addition to gravity,seismic disturbance was also the main reason for the formation of various deformation structures. It reflects the characteristics of strong tectonic activity in the Ordos basin during the Middle Indosinian Movement.

关键词

负载构造 / 砂球构造 / 地震 / 延长组 / 鄂尔多斯盆地

Key words

load structure / sand ball structures / earthquake / Yanchang Formation / Ordos Basin

基金资助

*陕西省教育厅重点实验室项目(编号: 20JS127)资助