Structural Style of Songkhla Basin, Gulf of Thailand

Abstract

Gulf of Thailand is composed of number of Cenozoic basins. The Ko Kra Ridge divides the Gulf of Thailand into two parts, which are Western Graben and Basinal Areas. Songkhla Basin is located in the Western Graben of the Gulf of Thailand. There is no detail study about the structure style of the Songkhla basin so far. In this study, in order to understand the tectonic evolution of the basin, I observed major geological structures by using 2D & 3D seismic data set. Seismic interpretation revealed four main types of geological structures that are; border faults, intrabasinal ridge, compressional structures and interbasinal fault. The basin has thicker sediments in the Western part as the sediments accumulated along the growth fault surface. Basin has geometry of an asymmetric half-graben bounded by major extensional faults (boundary faults) oriented NNW-SSE. Most of the faults are east dipping, but there are also some antithetic conjugated faults. Tectonic activity of the basin has three phases. The initial rifting occurred in Eocene or in Early Oligocene, which initiated the basin formation. The rifting phase was followed by inversion tectonic phase in Early Miocene. In the Middle Miocene extensional tectonics resumed.