AAPG Annual Convention and Exhibition

Datapages, Inc.Print this page

A New Type of Flower Structures in a Divergent-Wrench Fault Zone, Tan-Lu Fault Zone, East China


Flower structures are typical features of wrench fault zones. In conventional studies, two distinct kinds of flower structures have been identified based on differences in their internal structural architecture: (1) Negative flower structures characterized by synform (i.e., syncline) and normal separations, and; (2) Positive flower structures characterized by antiform (i.e., anticline) and reverse separations. In addition to negative and positive flower structures, here we identify a third kind of flower structure present in a divergent-wrench fault zone (Tan-Lu Fault Zone in east China), a hybrid characterized by both antiform (i.e., antiformal syncline or anticline) and normal separations. This new kind of flower structure, hybrid flower structures, have not been previously defined and investigated in previous structural research. In this study, we investigate the characteristics, structural background, and formation mechanisms of the three types of flower structures seen within a divergent-wrench fault zone, with emphasis on hybrid flower structures. The result shows that: (1) Negative flower structures widely occur in divergent-wrench fault zones, and their presence indicates the combined effects of extensional and strike-slip strain. In contrast, positive and hybrid flower structures occur only in local compressional regions under divergent-wrench background, such as fault-restraining bends, offset, overlap, and situations of compressional horsetail splay. In these local compressional regions, if compressional stress is large enough, positive flower structures will develop, or hybrid flower structures may occur. Thus, a hybrid flower structure occurs as the result of the combined effects of extensional, compressional, and strike-slip strain. (2)The existence of these hybrid structures in divergent-wrench fault zones indicates that compressional and extensional deformation can occur at the same time and place, and that anticlines are formed more easily than reverse faults given a compressional background. (3) Hybrid flower structures are also favorable for the accumulation of hydrocarbons because of their special structural configuration and the background to their formation.