The Indus Suture Rocks crop-out south of the Kohistan batholith over a c. 40 km strike width from NW to SE. The Indus Suture Rocks are exceptionally well exposed, forming cliffs and mountains with a c. 2000 m + vertical relief in places. The unit is well bedded and contiguously bedded. Thrust and fault structures are clearly visible in mountainside outcrops. There is a wide variation in clastic lithological character from coarse conglomerates to shales. This stratigraphy constitutes a molasse sequence which, in part, onlaps unconformably onto the Ladakh batholith. Outcrops in the north-westernmost part of the study area are dominated by cyclical graded coarse sandstone/conglomerate—shale sequences akin to hemipelagic turbidites. Parallel bedded sequences of conglomerate, gritty sandstone, siltstone and shale predominate with individual beds varying in thickness between a few centimetres and 60 cm. The rocks are metamorphosed from very low grade to phyllite-low greenschist grade. Sedimentary structures include graded bedding, cross bedding, flute structures, soft sedimentary deformation structures, and erosive bases. A high abundance of mafic and feldspar minerals in some sandstones are indicative of volcanic and plutonic source rocks. Structural studies of the Indus Suture Rocks largely, from photo-mosaic interpretations, reveal complex thrust nappe/horse stacks, antiformal thrust-stacks, and related fold structures. Individual thrusts vary from 10s to 100s of m thick. Whilst there is a predominant NE-trending thrust vergence, back-thrusts verge towards the NW and SE, with local variations in thrust kinematics. 

Charles G. Oviatt

Papers

Structure and Lithology of the Indus Suture Rocks (Indus Formation) in the Leh–Ladakh Region