MESOZOIC DEEP-WATER SLOPE RISE SEDIMENTATION AND VOLCANISM ALONG THE NORTH-INDIAN PASSIVE MARGIN - EVIDENCE FROM THE KARAMBA COMPLEX, INDUSSUTURE ZONE (WESTERN LADAKH-HIMALAYA)/

Mesozoic deep-water sedimentary and basic volcanogenic rocks, defined as the Karamba Complex, are exposed within the Indus suture zone of We stern Ladakh (N India). The Karamba Complex originated as part of the North-Indian passive margin in its entirety, and does not include exot ic melange or accreted oceanic units, as recently suggested. The compl ex preserves younger, more distal equivalents relative to more proxima l deep-water slope (Lamayuru Complex) and shelf (Zanskar) successions of the North-Indian passive margin. The Karamba Complex is mainly inve rted, youngs to the NNW, and includes many outcrop-scale folds that fa ce NNW. The Complex was initially emplaced onto the Zanskar Shelf as t hree main thrust slices probably in the latest Cretaceous, and later i nverted, faulted and sheared during mid-late Tertiary NW backthrusting that accompanied uplift of the High Himalaya. Sedimentation in the Ka ramba Complex began in the Mid-Late Triassic, with mainly siliciclasti c turbidites derived from the Indian basement, together with redeposit ed limestones and minor basic volcanics. Mixed radiolarian sediments, siliciclastic turbidites and redeposited shelf-derived calciturbidites accumulated in Early-Mid Jurassic, accompanied by eruption of alkalin e volcanic rocks, mainly in the Mid Jurassic. The probable cause of th e Jurassic volcanism was a pulse of crustal extension along the contin ent-ocean transition zone, triggered by late-stage rifting of India fr om Gondwana, as a precursor to its northward drift. Quartzose sandston e turbidites accumulated on the upper slope in the Early Cretaceous, w hereas sedimentation on the lower slope/rise was pelagic, marked by de positional hiatuses and sediment redeposition. During the Late Cretace ous a switch to mainly calcareous pelagic deposition took place, inter spersed with radiolarian accumulation on the lower slope/rise. Initial thrust emplacement onto the Zanskar Shelf in the latest Cretaceous is suggested by the absence of post-Upper Cretaceous sediments within th e Karamba Complex. (C) 1998 Elsevier Science Ltd. All rights reserved.