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Because the weather window for Expedition 303 was challenging, we designed a flexible operations scenario, which required reassessment of the original Expedition 306 operational plan following Expedition 303 drilling. During Expedition 303, seven proposed sites were occupied and more than 4600 m of high quality upper Pliocene–Quaternary sediments were recovered. Proposed sites occupied during Expedition 303 were ORPH-3A and ORPH-2A (Sites U1302/U13033), GAR-2B (Site U1304), LAB-6A, LAB-7A, and LAB-8C (Sites U1305, U1306, and U1307, respectively), and IRD-1A (Site U1308). See the Expedition 303 Preliminary Report for additional details (

In addition to the sites not drilled during Expedition 303 that are described in the Expedition 303/306 Scientific Prospectus, several new sites have been identified to provide additional operational and scientific flexibility. These new sites, approved for drilling prior to Expedition 303 (LAB-8V, LAB-8X, LAB-8Y, and LAB-8Z-alt), are located in the Eirik Drift area along the same seismic line (Knorr KN166-14 cruise Line KN166-14 25a) where Sites LAB-8C (Site U1307) and LAB-8A are situated (Fig. F1). They are positioned in series downslope from Site LAB-8C, encompassing LAB-8A. Results from drilling at LAB-8C (Site U1307) on this transect during Expedition 303 established the feasibility of recovering the Pliocene sedimentary section on the Eirik Drift using the advanced piston coring (APC) system. This transect provides a unique opportunity to sample the older (Pliocene–Miocene) stratigraphy to complement the stratigraphic sections sampled at Sites U1305, U1306, and U1307 and, hence, document drift architecture and climate history since the onset of Eirik Drift deposition.

Two additional sites were identified along the same seismic line (KN166-14 25a) during the process of assessing options for a revised operations plan for Expedition 306: LAB-8F and LAB-8G (Fig. F1). Although these sites are optimally positioned to maximize recovery of progressively older sediments, at the time of this addendum they are awaiting clearance from Denmark/Greenland. When these two sites are approved, they will be elevated from "alternate" to "primary" status.

Drilling results from the LAB-8 transect sites could extend the climate record back into the Miocene at locally enhanced sediment accumulation rates and provide a more-or-less complete record of Eirik Drift sedimentation that can be traced throughout the KN166-14 seismic network. The combination of successful drilling, logging, and the high-quality KN166-14 seismic records would make the Eirik Drift one of the best documented sediment drifts yet drilled and would answer questions about the sedimentary architecture of sediment drifts, the role of the Western Boundary Under-Current (WBUC) in North Atlantic Deep Water (NADW) formation, and provide a unique record of Greenland Ice Sheet instability.

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