Site U1606

Site U1606 (proposed Site MB-17A) was cored at 74°13.9380′N, 61°2.2426′W at 653 meters below sea level (mbsl) on the middle section of the northwest Greenland shelf (Figure F1). The site targets the transition from preglacial contourite drift sediments into glacigenic deposits of the earliest trough mouth fan progradation (Seismic Unit 1), marking the first advance of the northern Greenland ice sheet onto the continental margin (Figure F2). The drilling target was at 411 m core depth below seafloor, Method A (CSF-A), near the base of Megaunit B above Horizon c1 (Figure F3), coring a succession that is complementary to Site U1608. The uppermost 180 m at Site U1606 targets a geographically restricted depositional unit, possibly an erosional remnant, aimed at capturing a stratigraphic record of the preglacial to glacial transition that hypothetically corresponds to the Pleistocene/Pliocene boundary (Knutz et al., 2019). Below 150–180 m CSF-A, Site U1606 targets a 200 m thick sedimentary unit characterized internally by a uniform bundle of tilting strata that converges updip against a fault defining an erosional scarp above Horizon c1 (Figure F3). The seismic geometries imply accumulation of sedimentary drift deposits of Megaunit B over a significantly truncated section of Megaunit C (Knutz et al., 2015). The lower sedimentary unit of Site U1606 has a corresponding section at the base of Site U1608 (Figures F2, F3).