张性环境中与断裂相关的褶皱类型及特征

Features And Classification of Fault-Related Folds in Extensional Settings

张性环境下与断裂相关的褶皱作用 (包括纵向褶皱作用和横向褶皱作用 )的研究刚刚起步 ,以往的研究都将后者归因于走滑扭动或挤压反转的结果。但最新研究表明 ,横向褶皱多与张性环境下正断层作用相关的位移变化密切相关 ,也即横向褶皱是应变控制的构造 ,而不是应力控制的构造。根据相关断裂级别 ,横向褶皱级别也分为 5类 :盆地级别 (一级 )的横向褶皱、控坳及控隆横向褶皱、控凹及控凸横向褶皱、控制断鼻的横向褶皱、小尺度孤立横向褶皱 ,并与断裂分级对应。对张性环境下褶皱同时的干涉和先后的叠加 (统称复合作用 )进行了系统研究 ,对复合褶皱样式进行创新与探讨。这一研究不仅有助于伸展区发现新的圈闭类型 ,指导油气勘探 ;而且在于可创新性地在平面构造图上进行断裂生长顺序和组合规律的定性分析 ,同时还可对沉积相分布、沉积厚度变化等进行对应分析。

The study of fault-related folds, including longitudinal and transverse folds in extensional settings, just started in recent years. In the past, transverse folding was considered to result from wrench faulting or reverse compression. However, the latest research reveals that transverse folds are related to fault displacement variation along the strike direction. These folds are not controlled by stress but by strain. Transverse folds are classified into five orders correlated to the equivalent orders of faults in this paper. They are named the basin-controlled or the first-order transverse fold, the depression- or uplift-controlled transverse fold, the sag- or salient-controlled transverse fold, the nose-like-block-controlled transverse fold and the small-scale, isolated transverse fold. The synchronous interaction and asynchronous superposition of longitudinal and/or transverse fold in extensional settings are studied, and the fold combination is proposed and discussed for the first time in this paper. This is beneficial not only to the discovery of new trap types in extensional settings, but also to the analysis of fault-growing sequences and fault assemblage on a plane tectonic map and to the analysis of sedimentary facies and the variation of sedimentary thickness.