A multi-proxy provenance study of Eocene to Oligocene sandstones in the Salin Sub-basin, Myanmar

Abstract

The Salin Sub-basin, Myanmar, contains up to 15,000 m of Cenozoic sediments, but their provenance remains ambiguous. Here, a multi-proxy provenance study that employed Raman Spectroscopy-assisted heavy mineral analysis, light mineral petrography, and U-Pb detrital zircon geochronology, is used to identify source areas and sediment pathways of nine samples from three formations of Eocene to Oligocene age. The heavy mineral assemblages are diverse and highly immature and indicate that sediments were principally provided from a range of igneous and metamorphic lithologies, with some recycling of older sediments. The metamorphic basement rocks in northern Myanmar are identified as a source in all three formations, suggesting that the headwaters of the sedimentary pathway were situated in this area. Detrital zircons overwhelmingly yield Cretaceous and Palaeogene ages. A population of Late Cretaceous and Palaeocene zircons could indicate input from the Mogok Metamorphic Belt, or a currently buried section of the Wuntho-Popa Arc; the diminishing of this signal by the end of the Rupelian suggests reduction in transport from the former, or burial of the latter. Late Cretaceous grains exhibit rounded and euhedral morphologies, suggesting input from recycled Wuntho-Popa Arc material via the sediments of the Chin Hills, and direct input from the Wuntho-Popa Arc, respectively. A persistent Palaeoproterozoic and Triassic signal in the Shwezetaw and Padaung Formations suggests provenance in the Pane Chuang Formation of the Indo-Myanmar Ranges, showing that by the early-mid Oligocene, the ranges were topographically prominent enough to be an important source of sediment for the Central Myanmar Basin.