Abstract

Exposures in the Oligocene to Miocene section of coal mines in the Li Basin of northern Thailand show a complex structural evolution. The basins formed under approximately east–west extension. NW to north–south‐striking normal faults are dominant with some east–west normal faults also being present, but much less frequently. Episodically compressional and/or strike‐slip events affected the basin creating new east–west to NE–SW‐striking thrusts and folds and inverting some normal faults. The latest episode of compression formed NW‐SE to north–south striking thrusts and folds. Cross‐cutting structures, reactivation of structures, syn‐sedimentary deformation and unconformites help to constrain the relative timing of structural events. At least five episodes of predominantly NNW–SSE to NE–SW oriented compression interrupted the extensional development of the basin. The compression was probably related to the escape tectonics of the Himalayan orogeny. The episodic nature of the compression and extension is inconsistent with either simple strike‐slip related opening of the rift basins or simple extension. The data from the Li Basin indicate a reappraisal of current tectonic models for the region is necessary.

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