Gravity interpretation of Chiang Mai Basin, northern Thailand: concentrating on Ban Thung Sieo area

Abstract

The interpretation of gravity data from the Chiang Mai Basin area indicates that this Tertiary basin can be divided into five sub-basins. The largest is located just east of Chiang Mai City. This sub-basin is bordered in the west and northwest by steep major dip-slip faults and in the east by a more gentle dipping contact between the Tertiary sequence and the basement rocks of the eastern mountain range. South of this large sub-basin, in an area around Ban Thung Sieo, there are two other nearly parallel sub-basins separated by a basement horst which runs in a northeast-southwest direction; 2.5 D modelling suggests that the depth to the Cretaceous basement along the axis of the eastern sub-basin varies from 1.3 km at the northern end to 2.3 km at the southern end. This eastern sub-basin is bordered in the east by a fault contact with Paleozoic rocks of the eastern mountain range. As for the western sub-basin, the modelling suggests that its western edge consists of a fault contact between the rocks of western Doi Suthep mountain range and the Tertiary sequence. The maximum depth to the Cretaceous basement for this sub-basin is around 1.9 km.