Indian Ocean Carbonate Platform Evolution: Currents, Monsoon, and Sea Level
The objective of this proposal to unlock the Neogene paleoceanographic, sea level and paleoenvironmental archive of the Maldives carbonate platform and to test the hypothesis that currents are a major controlling factor of carbonate platform facies and stratigraphy. This goal will be achieved by analyzing cores, sediment samples, and wireline logs to be recovered during IODP Expedition 359, thus ground truthing a seismic stratigraphic model of this platform which has been developed for this expedition.
The Maldives carbonate edifice bears a unique and mostly unread Indian Ocean archive of the evolving Cenozoic icehouse world and it has great potential to serve as a key area for better understanding the effects of this global evolution in the Indo-Pacific realm. A dramatic shift in development of the carbonate edifice from a sea level-controlled to a predominantly current-controlled system during the Miocene is thought to be directly linked to the evolving Indian monsoon. Fluctuations in relative sea level control the stacking pattern of depositional sequences during the early to middle Miocene. This phase was followed by a two-fold configuration of bank development: bank growth continued in some parts of the edifice, whereas in other places, banks drowned. It is proposed that drowning steps coincide with onset and intensification of the monsoon-related current system and the deposition of giant sediment drifts. The shapes of drowned banks attest to the occurrence of these strong currents. The drift sediments, characterized by off-lapping geometries, formed large-scale prograding complexes, filling the Maldives Inner Sea basin. Because the strong current swept most of the sediment around the atolls away, relict banks did not prograde, and steady subsidence was balanced by aggradation of the atolls, which are still active today. Thus, what has to be tested is if carbonate platform slopes, although developing in the same carbonate platform, can possibly modify their internal structure and external geometry not only in response to modification in the accommodation space but largely as a reaction to current pattern changes, which in the case of the Maldives are related to the onset of the Indian Monsoon.
Addressing this question will directly improve our knowledge on processes shaping carbonate platforms and their stratigraphic records. Our findings would be clearly applicable to other Tertiary carbonate platforms in the Indo-Pacific region and to numerous others throughout the geological record. The proposal therefore encompasses the following work packages:
(1) Core- and sample-based reconstruction of the platform and slope facies;
(2) Wireline log-based core to seismic correlation;
(3) Characterization of the bottom current regime through time and linkage of variations in current strength to major changes in platform architecture.