RECONNAISSANCE GEOLOGY IN UPPER CHITRAL, BAROGHIL AND KARAMBAR DISTRICTS (NORTHERN KARAKORAM, PAKISTAN)

During the summer of 1992 a geological expedition crossed the northern Karakorum range in northern Pakistan, from the Chitral to Karambar va lleys, from the villages of Mastuj to Imit. Some of the areas visited were geologically unknown. A number of structural units were crossed, belonging to the Karakorum block or to other crustal blocks north of i t. They are: (a) the axial batholith, in which three plutonic bodies h ave been identified, and (b) the northern sedimentary belt (NSB), in w hich three major tectonostratigraphic units form thrust stacks dipping to the north. Their internal stratigraphy and structural style are pa rtly different. The most complete contains a crystalline basement, tra nsgressed by a marine succession during the Early Ordovician. The youn gest strata are represented by the Reshun conglomerate, of inferred Cr etaceous age. The northernmost unit of the NSB is tightly folded, wher eas the central one forms a monocline. Vertical faults, mainly strike- slip, dissect the thrusted slabs. Metamorphic deformation is absent or reaches only the anchizone in the studied sector of the Karakorum NSB . To the north of the Karakorum proper there are several other tectoni c units, separated by vertical faults. They are, from south to north: (a) the Tas Kupruk zone, with metavolcanics of basaltic to latibasalti c composition; (b) the Atark unit, mostly consisting of massive carbon ate rocks of Mesozoic age; and (c) the Wakhan slates which consist of a thick widespread succession of dark slates, metasiltites and sandsto nes. The fine-grained elastic rocks are supposed to be Palaeozoic to E arly Triassic in age. The Wakhan slates are intruded by plutons belong ing to the East Hindu Kush batholith, from which a single K/Ar age on muscovite gave a Jurassic age.