Sedimentology and geochemistry of Middle Eocene-Lower Oligocene sandstones from the western Salin Sub-Basin, the Central Myanmar Basin: Implications for provenance, source area weathering, paleo-oxidation and paleo-tectonic setting

摘要

The Salin Sub-Basin is a well-known Cenozoic hydrocarbon-rich basin in central Myanmar, and contains a succession of siliciclastic sedimentary rocks. The analytical results of petrographic and whole-rock geochemical data indicate that the sandstone sequences in the Salin Sub-Basin were derived mainly from at least three different provenances: the Western Myanmar Arc, the Myanmar terrane basement, and the westerly Indo-Myanmar (Burman) Ranges (IMR), where sediments were subjected to initial-intermediate weathering conditions and rapid erosions, and were finally transported to the studied area. Based on the comparison of the geochemical variations between the Salin Sub-Basin in Myanmar and Sylhet Basin in Bangladesh, the provenance terranes of these two sedimentary basins were found to be significantly different from each other. This is most likely due to the rising of IMR and the IMR probably acts as the barrier between the Salin Sub-Basin in the East and Sylhet Basin in the west, and prevents influences of Myanmar sediment sources on the Sylhet Basin. As a result of major and trace-element tectonic setting discrimination diagrams and geochemical parameters, sedimentation in the studied area was likely to occur at the Continental Island Arc (CIA) setting under a well- oxygenated condition. It was most probably formed under the site of a fore-arc setting associated with the India-Asia convergence and collisional processes.