New Field and Geophysical Data About the Transpressional Deformation in Shagou Fault Zone, Northeastern Edge of Tibetan Plateau, Central China

Abstract

Situated near the northeastern edge of the Tibetan Plateau, the Shagou fault zone represents an important area to understand Cenozoic regional interactions between northeastern Tibetan Plateau and southwestern Liupan Shan Basin. Within this region, several huge bow-like fault systems such as Lijun fault and Madong Shan piedmont fault accommodate the transpressive deformation, but their structural style is still highly debated. The unique structural pattern of this zone can be identified by the field observation data, interpretation of seismic reflection profiles and two-dimensional gravity forward modeling. Based on the resent fieldwork, the horizontal slickensides, structural cleavages, sub-vertical fault surfaces, “ribbon effect” as well as the linear geomorphic features indicate these faults are strike-slip systems. Newly acquired seismic profiles, characterized by distinct positive flower structures, strongly suggested that this area is again a strike-slip fault system rather than a thrusting system. Furthermore, gravity forward modeling shows that the reverse strike-slip model without large-scale nappe is more approximate to the real structural style. Generally speaking, the overall structural style of the Shagou fault zone is not characterized by large-scale thrust nappes, but dominated by a transpressional shear system with significant strike-slip faulting. The Cenozoic transpressive deformation may have breached seals and thus negatively affected the hydrocarbon potential of the zones adjacent closely to strike-slip faults, as contrasted with those in the middle part of Shagou fault zone, which was not significantly disrupted by transpressional movements.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015