Left-lateral sense offset of Upper Proterozoic to Paleozoic features across the Gobi Onon, Tost, and Zuunbayan faults in southern Mongolia and implications for other central Asian faults

Abstract

We present a preliminary study of Upper Proterozoic to Paleozoic features adjacent to, and offset across, three faults in southern Mongolia. Restoration of four offset stratigraphic units adjacent to the Gobi Onon fault indicates a left-lateral sense offset of 70–95 km. The Tost fault has a left-lateral sense offset of 95–125 km defined by three offset features. The Zuunbayan fault has seven offset features that display left-lateral sense offsets of 185–235 km. Deformation on these faults apparently occurred during the Mesozoic prior to the Late Cretaceous based upon the age of offset features, the age of overlap sequences, and inferred timing relationships with regional contractional structures. Although Cenozoic overprinting and reactivation has occurred along parts of these faults, thus complicating their restorations, we present a testable hypothesis which predicts possible connections between these faults and faults within China.