Paleogeography of the West Burma Block and the eastern Neotethys Ocean: Constraints from Cenozoic sediments shed onto the Andaman-Nicobar ophiolites

The Andaman and Nicobar ophiolites, in the forearc of western Sunda subduction zone, underwent enigmatic, rapid Cenozoic vertical motions: shallow-water sediments with abundant arc debris characterize middle Paleocene–middle Eocene are under- overlain by significantly deeper sediments. Recent paleomagnetic results revealed a near-equatorial paleolatitude West Burma Block associated at similar latitude as until early Eocene, providing new avenue toward explaining unusual stratigraphy. Here, we studied provenance clastic Andaman-Nicobar accretionary ridge using petrography, geochemistry, detrital zircon geochronology. We found that Paleocene-Eocene Namunagarh Grit is likely to be derived from then proximal, 60 Ma old was located ocean north (present-day east) Block, west Andaman-Nicobar. Oligocene–lower Miocene East Flysch contains traveled much farther mixed Sundaland. Great have an additional Himalayan source consistent derivation downgoing plate. interpret this history reflecting late Paleocene–early collision part Australian Plate, causing uplift proximal sedimentation shed colliding arc. Subsequent northward motion caused subsidence forarc N-S opening Sea, which opened pathway for Sundaland-derived reach ophiolites. recently proposed high mobility remains reconciled detail geological observations Myanmar Sundaland, but our show scenario provides ample opportunity explain previously enigmatic stratigraphic evolution Islands.