Monsoonal impact on the Maldives carbonate platform (ODP Site 716).
Final Report Abstract
The Neogene evolution of the carbonate edifice of the Maldives archipelago is controlled by sealevel changes and fluctuations of the oceanic current regime. Lower and middle Miocene strata form ten sequences that formed in response to variations of accommodation space primarily driven by relative sea level. The upper Middle Miocene is characterized by the appearance of a largescale clinoform bodies which are attached to passages where bank segment drowned, while in other parts bank grew on. Hence, since late middle Miocene times the Maldives show a twofold configuration of bank development of persisting growth, which is accompanied by partial platform drowning and associated localized deposition of contourites and drifts in areas just some kilometer apart. The drift deposits comprise contourite fans, elongated mounted drifts and prograding clinoform drift bodies. The currents kept the proximal platform foreslopes relatively sediment starved which hindered the progradation and supported the aggradation of the neritic platform. The architecture of some drift bodies exhibits seismic patterns comparable to sea-level controlled clinoforms, which are typical for prograding carbonate platform margins. However, their forests are not concave but convex in shape. Because of their fabric drift sediments could be potential exploration targets. Grain-size variations of periplatform ooze in the drift deposits at ODP Site 716 for the last seven My correlate to seismostratigraphic unit boundaries. For the last two My it can be shown that coarser deposits formed at time of an intensified monsoon regime. During the early Mid Pleistocene Transition, the first large sea-level fall triggered deposition of a grain-flow interval in the Inner Sea; subsequently, strong bottom current let to winnowing of fines at the sea floor. With relaxation of the monsoon system around MIS 10, the grain-size data become positively correlated with the oxygen isotope data and the aragonite contents. It is therefore shown that periplatform ooze not only record the highstand shedding of carbonate platforms but also fluctuations in the regime of bottom currents. This implies that periplatform ooze accumulated in sediment drift bodies are a potential target for reconstruction of past changes of oceanic currents.
Publications
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2012. Relationship between Late Pleistocene sea-level variations, carbonate platform morphology and aragonite production (Maldives, Indian Ocean). Sedimentology, 59, 1640 - 1658
Paul, A., Reijmer, J.J.G., Fürstenau, J., Kinkel, H., Betzler, C.
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Sea-level and ocean-current control on carbonate-platform growth, Maldives, Indian Ocean. Basin Research
Betzler, C., Fürstenau, J., Lüdmann, T., Hübscher, C., Lindhorst, S., Paul, A., Reijmer, J.J.G., Droxler, A.
