The 1:100 000 geological map of Western-Central North Karakoram terrain (Northern areas, Pakistan)

After the last expedition carried out by the Milano team in 1999 between Chitral and the Karambar valley (Gilgit agency, northern areas), the new geological map of the western-central sector of the north Karakoram terrain has been now completed and prepared for final printing at a 1:100 000 scale. The new map includes the survey of the entire sedimentary cover lying north of the Karakoram batholith up to the Afghan border on a longitudinal extension of 150 km. Stratigraphic and structural work carried out by us since 1992 has allowed for the identification of the main tectono-stratigraphic units cropping out in the area. Fieldwork has been integrated also through photo-interpretation with Spot panchromatic imagery and previous maps, extending the mapped area northward into Afghanistan (Buchroitner and Gamerith, 1978). The map also includes part of the northern sector mapped by Le Fort and Gaetani (1998). The main results of our cartographic work can be summarised as:. The sedimentary cover of the western-central part of Karakoram includes a thick and almost complete Paleo-Mesozoic succession (5-6 km) uncomformably covering a pre-Ordovician crystalline basement (quartzite) intruded by granitoids. The youngest terms of the succession include Jurassic carbonates in the Baroghil area, and the Late Cretaceous Reshun Formation, which unconformably covers previously deformed units. Each tectonic unit displays a peculiar stratigraphic evolution suggesting strong mobility and repeated rifting events between Late Devonian and Permian with a major event during Carboniferous. The Reshun formation continuously occurs across the study area joining the Tupop formation defined in the Hunza region, which can be considered a lateral equivalent of the former. At the same time, the western continuation of the Reshun fault has been traced to the Baroghil area and further on across the Chantar glacier and the Chillinji area up to the western extension of the Hunza fault in the uppermost part of the Chapursan valley. A large part of Karakoram extends into Afghanistan, forming the southern part of the Wakhan. The northern margin of the Karakoram batholith is generally sheared and thrusted northward above the sedimentary cover, Several slices of metasediments are tectonically intercalated between the main intrusive units, suggesting an extensive regional deformation of the batholith. The main structural features of the mapped tectonic units and the kinematics of the major faults have been defined, taking to a general interpretation of the evolution of the area. Information included in the map is in a digital georeferenced format (arcinfo-arcview format) and has been integrated within a database containing structural and stratigraphic data. A schematic topography represented by contour lines (500 m) has been obtained from the 1:100 000 scale USSR map of the world (original survey 1:40 000). The map will be published in collaboration with the geological survey of Pakistan.