How deep was the early Himalayan foredeep?

The Himalayan foredeep is a good archive of the events that occurred during different stages of the basin evolution. The early part of this archive is used here to interpret depositional environments and paleobathymetry based on facies associations, sedimentary structures and larger foraminifera. Three facies associations are recognized in the early Himalayan foreland basin sequences. Facies association I, containing chert breccia, bauxite/quartzose sandstone, coal and black shale, was deposited in short-lived ephemeral streams, swamps and inner parts of lagoons. The limestones and shales of the facies association II were deposited in a barrier-lagoonal system where the former represent barrier and the latter represent lagoon deposits. The limestone beds, containing hummocks and wavy ripples, were deposited under the influence of oscillatory storms and represent tempestites. Siltstone beds, containing hummocky cross-stratification and ripple cross-laminae, were deposited in the shoreface or foreshore zone where storm activities were dominant. Facies association III, comprises marl laminites and purple shale deposited in intertidal and supratidal zones of a tidal flat. Larger foraminifera such as Nummulites and Assilina flourished in the tropical climatic belt and accumulated in the coastal zone as a result of their transportation by waves and tides. In general, the sedimentation took place on a ramp similar to the present day Persian Gulf with a paleobathymetry of similar to 55 m. In strike continuity in Pakistan, the coeval sequences were deposited on shelves with a paleobathymetry <200 m. The early foredeep sequences are, thus, devoid of deep marine sediments. (C) 2012 Elsevier Ltd. All rights reserved.