Bangladesh-Burma Accretionary Prism: Evolution and Provenance

The Chittagong Hill Tracts of Bangladesh and the Indo-Burman Ranges (Arakan Yoma) of Myanmar constitute an accretionary prism which runs along the India-Asian subduction zone. It consists of Palaeogene as well as Neogene sedimentary rocks that may preserve a record of early Himalayan erosion, which is as yet inaccessible in the deeper parts of the Bengal Fan, or missing in other sediment repositories of the region (Curray et al. 1979, 2003 and Gani et al. 1999). However, a Burman provenance has also been suggested for these rocks (Mitchell, 1993; Pal et al. 2003). In order to characterise the provenance signature of the accretionary prism rocks and determine Himalayan or Burman source, we have used petrographic, heavy mineral, U-Pb, fission track, Sm-Nd and Ar-Ar analyses. We present results of the initial study, including new seismic data (obtained by Cairn Energy plc.) which provides a seismic stratigraphy of the Chittagong Hill Tracts calibrated to offshore well seismic data, as well as comprehensive palaeoshelf mapping of the Bengal Basin region during the Eocene to Pliocene, which documents source input direction.