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Operational strategy

Drilling offshore Barbados (Fairbanks, 1989) demonstrated that the reef sequence corresponding to the last deglaciation developed only on slopes and therefore forms discontinuous successive terraces of various lateral extent.

At Tahiti, recovery of the last deglacial reef sequence required drilling successive reef terraces that occur seaward of the living barrier reef. Studies and surveys around Tahiti have demonstrated the occurrence of successive reef terraces at various depths—100, 90, 60, and 40–50 m—which therefore correspond to drilling targets. Thus, at each site, we cored several boreholes along transects to attempt to recover the entire last deglacial reef sequence.

Based on the results of previous scientific drilling and bathymetric and seismic data acquired during the Sismique Haute Resolution, Bathymetrie et Dragages sur les Pentes Externes des Recifs de Tahiti (SISMITA) cruise, we drilled a transect of holes in three areas around Tahiti: offshore Faaa (proposed Site TAH-01A), Tiarei (proposed Site TAH-02A), and Maraa (proposed Site TAH-03A) (Fig. F2). Water depths at these locations ranged from 41.65 to 117.54 m.

The exact location of the drill holes was determined during the cruise by checking the nature and morphology of the seafloor with a through-pipe underwater camera. All holes were sited within a 150 m radius around the proposed drilling sites approved by the Environmental Pollution and Safety Panel (EPSP), or within the midcruise EPSP-approved 200 m extension of the circle around proposed Site TAH-02A 4 (to 350 m radius). Figures F3, F4, and F5 show the locations of the holes at Faaa, Tiarei, and Maraa, respectively.