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The stratigraphic evolution of the Indus Fan and the history of sedimentation in the Arabian Sea

The stratigraphic evolution of the Indus Fan and the history of sedimentation in the Arabian Sea,10.1023/A:1023627123093,Marine Geophysical Researches

The stratigraphic evolution of the Indus Fan and the history of sedimentation in the Arabian Sea   (Citations: 10)
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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.
Journal: Marine Geophysical Researches - MAR GEOPHYS RES , vol. 23, no. 3, pp. 223-245, 2002
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    • ...Because lithospheric thickening drives thermal subsidence we suggest that the small degree of subsidence after break-up indicates very slow lithospheric growth, and that normal subsidence and lithospheric thickening does not occur until after 37 Ma. Alternatively itispossible,ashasbeensuggestedforsomeothervolcanicmargins(e.g., Clift, 1997), that the lack of subsidence represents a balance between normal thermal subsidence and uplift ...

    Gérôme Calvèset al. Anomalous subsidence on the rifted volcanic margin of Pakistan: No inf...

    • ...Indian plate boundary undergoing uplift since the early Miocene (Clift et al., 2002)...

    Venigalla Purnachandra Raoet al. Miocene phosphorites from the Murray Ridge, northwestern Arabian Sea

    • ...Unfortunately because this study was based on proprietary, industrial data it is impossible to test these sediment budgets or assess how representative they might be. In contrast, analyses of regional 2D seismic profiles in the Arabian Sea [12] and in the marginal seas of East and SE Asia [13] are thought to better estimate regional sediment volumes by covering much more of each margin than was previously possible...
    • ...The locations of the new data are shown in Fig. 2, while the interpreted stratigraphy derived from these 1977 vintage multichannel seismic profiles is shown in Fig. 3. Although these new estimates are not fully comprehensive, they do represent a major improvement on all previous mass flux estimates, and, crucially, the original data are published [12,13], allowing the uncertainty in the results to be assessed and improved on with further ...
    • ...Of the different drainage systems examined here only in the Indus River is there a major terrestrial sediment sink, accounting for about one third of the Cenozoic sediment mass [12]...
    • ...Fig. 1. Map of Asia and surrounding oceans showing the location of sections whose backstripping and decompaction form the basis of the revised sediment budget of Clift et al. [13], as well as the Indus Fan [12]...
    • ...Several other basins show that erosion reached maximum values during the early or middle Miocene (11–23 Ma), e.g., Indus, Pearl and Mekong Rivers [12,13,19]...
    • ...The same is true in the Indus River drainage, where sedimentation rates fell drastically after the middle Miocene [12] before rebounding in the Pleistocene...
    • ...Although Molnar [48] has argued that arid climates are more erosive because of the transportation power of flash floods, geological records from the Bengal Fan [49], Indus Fan [12] and South China Sea [19], together with the data presented above, indicate slower accumulation during periods of regional aridity...
    • ...However, the new budgets [12,13] now show average accumulation values since 1.8 Ma that are much lower than would be expected from the modern clastic flux, with only the Indus River coming close to matching the two (Table 1). The Indus may differ because of the long and actively subsiding character of its onshore basin, which is thus a more effective sediment trap than those seen in SE Asia...
    • ...The new sediment budgets for the Asian marginal seas [12,13] imply that changes in erosion, driven by climate, can and are communicated directly to the stratigraphic record on the continental margins, at least during the Neogene...

    Peter D. Clift. Controls on the erosion of Cenozoic Asia and the flux of clastic sedim...

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