The role of strike-slip faults in the displacement of the Palaeotethys suture zone in Southeast Thailand

Abstract

Six N–S tectono-stratigraphic belts can be recognized in Southeast Thailand, each with a distinct stratigraphy and igneous history. The westernmost Belt (I) is thought to be part of the Sibumasu Block, and the easternmost (V) to include part of the Indochina Block. Between those, Belt III comprises acid volcanic rocks, volcaniclastics, and Carboniferous to Triassic sedimentary rocks with distinctive faunas, interpreted to be a volcanic arc; Belt IV comprises Triassic rocks of back-arc basin origin; Belt V is interpreted as a Permian accretionary complex on the western flank of Indochina; and VI is an unconformable cover of Jurassic–Cretaceous red-beds correlating with the Khorat Group. A history of the Triassic Indosinian Orogeny is proposed, leading to the cratonization of Southeast Thailand by the end-Triassic.The apparent absence in Southeast Thailand of rocks from the Devonian–Triassic Palaeotethys ocean (the Inthanon Zone of Northern Thailand) is suggested to have resulted from a phase of post-Indosinian, oblique to longitudinal, sinistral, strike-slip faulting. That phase is thought to have included displacement on the Mae Yuam Fault which bounds the Inthanon Zone in Northern Thailand. Then followed a phase of transverse, sinistral, strike-slip faulting which offset the tectono-stratigraphic belts and faults of the earlier phase.