Sediment Composition and Provenance of the Pab Formation, Kirthar Fold Belt, Pakistan: Signatures of Hot Spot Volcanism, Source Area Weathering, and Paleogeography on the Western Passive Margin of the Indian Plate During the Late Cretaceous

Abstract

Petrographic and geochemical data collected from the Pab Formation, a late Cretaceous clastic sequence exposed in the Kirthar Range of western Pakistan, yield important clues about the influence of the varied source regimes, transportation routes and volcanic input that have influenced the composition of sediments comprising this formation. Detrital compositional modes, petrotectonic discrimination diagrams and paleocurrent data all demonstrate that the Pab sands were ultimately derived from granitic-gneissic terranes forming the Indian Craton, exposed to the E and SE of the study area, with probable supplementary contribution from the mature, ancient sedimentary cover of the craton. These data also confirm that the two contemporaneous depositional systems operating during accumulation of the Pab Formation in this area were supplied from somewhat different sources and through different routes. Sediments deposited in the Central Kirthar sub-basin were derived from the East, while coeval deposits within the Southern Kirthar sub-basin were supplied from SSE and include relatively fresh volcanic detritus that is interpreted as the product of the major Deccan Trap volcanic episode, initiated during late Maastrichtian times. Moreover, geochemical indicators demonstrate that the ultimate composition of Pab sediments has been strongly influenced by intense chemical weathering, associated with warm/humid climatic conditions in the source areas, accompanied by significant diagenetic effects. © 2013 King Fahd University of Petroleum and Minerals.