Himalayan-Bengal Model for Flysch Dispersal in the Appalachian-Ouachita System

Abstract

The relation of the modern Bengal subsea fan to the Cenozoic Himalayan suture belt and the analogous relation of the Carboniferous Ouachita flysch to a presumed Paleozoic Appalachian suture belt suggest a guiding principle of synorogenic sedimentation. Most sediment shed from orogenic highlands formed by continental collisions pours longitudinally through deltaic complexes into remnant ocean basins as turbidites that are subsequently deformed and incorporated into the orogenic belts as collision sutures lengthen. India first encountered a southern Eurasian subduction zone near the end of Paleocene time. Northward movement of India since Oligocene time choked the subduction zone, stifled the associated magmatic arc, and created a suture complex of deformed Cretaceous flysch and younger Tertiary molasse. Strata derived from the resulting orogen include continental clastic wedges shed southward toward India and voluminous turbidites fed longitudinally through the Ganges-Brahmaputra Delta into the Bay of Bengal. The eastern flank of the Bengal subsea fan is being subducted now beneath the still-active eastern extension of the subduction zone. The sequential, north-to-south welding of Europe and Africa to North America formed the complex Appalachian-Caledonide-Mauritanide suture belt, from which Taconic, Acadian, and Alleghanian clastic wedges were shed toward the North American craton. Turbidites of the Carboniferous Ouachita flysch were fed longitudinally, as sediment supplied through the Alleghanian clastic wedge, into a remnant ocean basin lying south of North America. The Ouachita system was then thrust northward across the continental edge during arc-continent collision that progressed from east to west.