Structural Patterns of The Mud Diapir in Andaman Seas and Their Determining Factors

Diapirs are widely occurred both in continental margins and foreland basins. Although the features and formation mechanisms of salt diapirs have been investigated in detail, mud diapirs are still far from being fully... [ view full abstract ]

Diapirs are widely occurred both in continental margins and foreland basins. Although the features and formation mechanisms of salt diapirs have been investigated in detail, mud diapirs are still far from being fully understood because it is normally difficult to clearly distinguish them in seismic profiles. Oil and gas exploration activities have revealed that mud diapirs are also common structures occurred both in continental margins and foreland basin and can have significant effects on the distribution of oil and gas. Based on interpretations of new seismic profiles and drilling data together with regional tectonic information, the features and controlling factors of mud diapirs in Andaman Sea basins were discussed in this paper. Our works revealed that there are five types of mud diapirs in Andaman Sea basins, including turtles, domes, pierces, mud volcanoes and gas chimney. Turtles and domes diapirs mainly existed in the south part of accretionary wedge far from the Bengal fan with obviously low sedimentation rates, where the tectonic stress is dominantly compressional. Piercing diapirs mainly occurred in the middle part of accretionary wedge with thick shale and close to the sediment provenance and where the tectonic stress is transpressional and sedimentation rates are relatively high. Mud volcano mainly occurred in the north part of accretionary wedge dominated by shear tectonic stress filed, where the thickness of shale is large due to high sedimentation rates. Gas chimney diapirs mainly existed in the north of Andaman sea back arc basin with obviously high sedimentary rate, where the thickness of shale is large and geothermal gradient is relatively high and the fault activating by Sagaing fault. Our works suggested that the occurrence of mud diapirs in Andaman sea basin were controlled by the thickness of the source layer, sedimentation rates, geothermal gradient, tectonic stress fields and the activity of Sagaing fault.