Provenance of the Eocene sandstones in the southern Chindwin Basin, Myanmar: Implications for the unroofing history of the Cretaceous–Eocene magmatic arc

Abstract

The Eocene sedimentary rocks, exposed in the southern Chindwin Basin, northern part of Myanmar, are characterized by a thick sequence of continental clastic units consisting of sandstones with abundant volcaniclastic materials, and a subordinate amount of metamorphic lithic fragments. Detrital information preserved in these Eocene clastic sequences has shed light on the erosional unroofing history of a Cretaceous to Eocene Andean-type continental magmatic arc related to the India–Asia collision.An integrated study of the petrography, geochemistry and LA-ICP-MS (Laser Ablation Inductively Couple Plasma Mass Spectrometer) U–Pb zircon geochronology of the late Middle Eocene, volcaniclastic Pondaung sandstones, combined with the WSW-directed regional mean palaeocurrent direction (∼254° azimuth), has revealed an older, calc-alkaline, andesitic volcanic arc (detrital U–Pb zircon age: 101–43Ma), situated to the NE of the southern Chindwin Basin, possibly related to the Neo-Tethys seafloor subduction beneath the Eurasia continental margin, i.e., the West Burma Block or Burma (Myanmar) Plate. We suggest that this arc may have been eroded during the late Middle Eocene (Bartonian) with volcaniclastic detritus deposited in the fore-arc basin of the Central Myanmar Basin, forming the Pondaung Formation.