The stratigraphic evolution of the Indus Fan and the history of sedimentation in the Arabian Sea |
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| Authors: | Clift Peter Gaedicke Christoph Edwards Rosemary Il Lee Jae Hildebrand Peter Amjad Shahid White Robert S Schlüter Hans-Ulrich |
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| Institution: | (1) Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA;(2) Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, D-30655 Hannover, Germany;(3) Bullard Laboratory, Madingley Rise, Department of Earth Sciences, University of Cambridge, Cambridge, CB3 0EZ, UK;(4) Polar Sciences Laboratory, Korea Ocean Research and Development Institute, Ansan P.O. Box 29, Seoul, 425-600, Korea;(5) Department of Geology, Trinity College, Dublin 2, Ireland;(6) National Institute of Oceanography, ST-47-Block 1, Clifton, Karachi, 75600, Pakistan |
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| Abstract: | The Indus Fan records the erosion of the western Himalayas and Karakoram since India began to collide with Asia during the Eocene,  50 Ma. Multi-channel seismic reflection data from the northern Arabian Sea correlated to industrial well Indus Marine A-1 on the Pakistan Shelf show that sedimentation patterns are variable through time, reflecting preferential sedimentation in deep water during periods of lower sea-level (e.g., middle Miocene, Pleistocene), the diversion of sediment toward the east following uplift of the Murray Ridge, and the autocyclic switching of fan lobes. Individual channel-levee systems are estimated to have been constructed over periods of 105–106 yr during the Late Miocene. Sediment velocities derived from sonobuoys and multi-channel stacking velocities allow sections to be time-depth converted and then backstripped to calculate sediment budgets through time. The middle Miocene is the period of most rapid accumulation, probably reflecting surface uplift in the source regions and strengthening of the monsoon at that time. Increasing sedimentation during the Pleistocene, after a late Miocene-Pliocene minimum, is apparently caused by faster erosion during intense glaciation. The sediment-unloaded geometry of the basement under the Pakistan Shelf shows a steep gradient, similar to the continent-ocean transition seen at other rifted volcanic margins, with basement depths on the oceanward side indistinguishable from oceanic crust. Consequently we suggest that the continent-ocean transition is located close to the present shelf break, rather than >350 km to the south, as previously proposed. |
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| Keywords: | Arabian Sea backstripping submarine fan |
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