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Abstract

International Ocean Discovery Program (IODP) Expedition 359 is designed to address sea level, currents, and monsoon evolution in the Indian Ocean. Seven proposed drill sites are located in the Maldives and one site is located in the Kerala-Konkan Basin on the western Indian continental margin. The Maldives carbonate edifice bears a unique and mostly unread Indian Ocean archive of the evolving Cenozoic icehouse world. It has great potential to serve as a key area for better understanding the effects of this global evolution in the Indo-Pacific realm. Based mainly on seismic stratigraphic data, a model for the evolution of this carbonate bank has been developed, showing how changing sea level and ocean current patterns shaped the bank geometries. A dramatic shift in development of the carbonate edifice from a sea level-controlled to a predominantly current-controlled system 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 lower 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. Drowning steps seem to 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.One important outcome of Expedition 359 is ground-truthing the hypothesis that the dramatic, pronounced change in the style of the sedimentary carbonate sequence stacking was caused by a combination of relative sea level fluctuations and ocean current system changes. Answering 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. In addition, the targeted successions will allow calibration of the Neogene oceanic 13 C record with data from a carbonate platform to platform-margin series. This is becoming important, as such records are the only type that exist in deep time. Drilling will provide the cores required for reconstructing changing current systems through time that are directly related to the evolution of the Indian monsoon. As such, the drift deposits will provide a continuous record of Indian monsoon development in the region of the MalExpedition 359 Scientific Prospectus 4 dives. These data will be valuable for a comparison with proposed Site KK-03B in the Kerala-Konkan Basin (see Geological...

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“…It is located to recover the entire drift succession (DS01-DS09). This site was selected to replace previous primary Site MAL-04B (Betzler et al, 2014), which is believed to have a mass flow intercalated into the succession at a depth of 720 ms between 63250 and 69000, based on analysis of a new parasound line recovered crossing the site. F10, F11).…”

“…F2; see F19 in Betzler et al, 2014) • Primary line(s): Line 65 ( Fig. F3; see F21 in Betzler et al, 2014) Objective ( • Location map (Fig. F2) • Primary lines: Line SO236-32 ( Fig.…”

“…This addendum to the Expedition 359 Scientific Prospectus (Betzler et al, 2014) addresses a modification to the scientific objectives and operations plan of the expedition. After consultation with and direction from the U.S. National Science Foundation (NSF), the Ancillary Proposal 849-APL will not be implemented as part of Expedition 359, and consequently the proposed sites (KK-03A and KK-03B) originally planned for scientific drilling in the Kerala-Konkan Basin have been dropped from the operations plan.…”

“…Also detailed in this addendum is an extension to the total penetration depth at primary proposed Site MAL-02A from 560 to 1010 meters below seafloor (mbsf). All other details contained within the original Scientific Prospectus published by the International Ocean Discovery Program in November 2014 (Betzler et al, 2014) remain the same. A summary of the primary sites targeted for Expedition 359 is shown in Table T1.…”

“…= pending EPSP approval. MAL-08A and MAL-09A are new proposed sites that are not in the Expedition 359 Scientific Prospectus(Betzler et al, 2014). MAL-04B and MAL-08A are proposed alternate sites.…”