Accelerated mass flux to the Arabian Sea during the middle to late Miocene

Abstract

Possible links between orogenic uplift and the strengthening of the South Asian monsoon are best examined in the Arabian Sea, where the erosional flux is not dominated by the High Himalaya, as in the Bengal Fan, but is controlled by Tibet, the Karakoram, and the Hindu Kush. The erosional flux from these mountains into a basin where the monsoon is well dated allows a direct comparison of erosional, tectonic, and climatic processes. New seismic data from the proximal Indus Fan permit the thickest part of this system to be dated for the first time through correlation to drilling sites. After converting time sections to depth and then accounting for sediment compaction, the data show a two- to threefold increase in mass flux to the upper fan and continental shelf, peaking during the middle Miocene (16–11 Ma), and falling from the late Miocene to the present. Increased sedimentation rates are accompanied by the growth of channel-levee complexes. High sediment flux does not correlate with monsoonal strengthening at 8.5 Ma, but follows uplift of the Murray Ridge, uplift in Tibet and the Karakoram after 20 Ma, and the start of transpression along the Karakoram fault at 18 Ma (>20 km of erosion).