Geologic offsets across the northern Karakorum fault: Implications for its role and terrane correlations in the western Himalayan-Tibetan orogen

While the >1000 km long Karakorum right-slip fault is one of the most prominent structures in the Himalayan-Tibetan orogen, considerable disagreement exists as to the total magnitude of offset across the fault and the role it has played in accommodating convergence between India and Asia. Using satellite images, I have correlated a well defined carbonate unit, the Late Triassic-Early Jurassic Aghil formation, across the northern portion of the Karakorum fault from the southwest Pamir to the Tianshuihai terrane of western Tibet. The northern and southern exposure limits of the Aghil formation have 149-167 km of separation, which I interpret to represent the magnitude of displacement on the northern Karakorum fault. These values overlap with estimates correlating the Bangong-Nujiang and Shyok sutures across the central Karakorum fault and maximum offsets of the Miocene Baltoro Granite and rule out correlations of the Bangong-Nujiang suture and the Rushan Pshart suture. The displacement yields a geologic slip rate of 10.8 +/- 1.3 mm/yr using an initiation age of 14.7 +/- 1 Ma, or 6.89 +/- 0.8 mm/yr with an initiation age of 23 +/- 1 Ma. This result supports previous work showing limited offset across the Karakorum fault and indicates that the fault that has not accommodated either large magnitudes (i.e. 100's of km) of eastward lateral extrusion of Tibet or hundreds of kilometers of offset between terranes of the western and central portions of the orogenic belt. (C) 2009 Elsevier B.V. All rights reserved.