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Site U1608 (proposed Site MB-06D) was cored at 74°7.6818′N, 60°58.3172′W at 607 meters below sea level (mbsl) on the middle section of the northwest Greenland shelf, west of the Melville Bay Ridge and graben structures formed during Cretaceous rifting (Figure F1; see Figure F4 in the Expedition 400 summary chapter [Knutz et al., 2025b]). The main coring targets are mounded contourite drift deposits of expected Pliocene age associated with Megaunit B (Knutz et al., 2015, 2019; Aubrey et al., 2021) and overlying sediments of Megaunit A, recording the transition into glacigenic deposits of earliest trough mouth fan (TMF) progradation (Figure F2). The expanded interval of Megaunit B, captured at Sites U1606 and U1608, reflects deposition below a major incised escarpment that is at least 500 m tall and extends into disturbed sediment packages interpreted as mass transport deposits (Figure F3). The base of the contourite drift accumulation is defined by Horizon c1 of probable Late Miocene age (Knutz et al., 2015). Site U1608 ends ~100 m above Horizon c1, which at this location is characterized by an erosional unconformity related to the slope instability that is strongly expressed in the seismic record (Figure F3). In the context of the full development of the Melville Bugt TMF, Site U1608 targeted TMF Seismic Unit 1, which records the first advance of the northwestern Greenland ice sheet (GrIS) onto the continental shelf, which is hypothesized to correspond to the Pleistocene/Pliocene boundary (Knutz et al., 2019) (Figures F2, F3). Combined, the cores from middle shelf Sites U1606 and U1608 access archives of ocean and climate conditions presumably much warmer than today that were buried by glacial deposits representing global cooling and expansion of northern hemisphere glaciers. These sites use the dynamic drift morphology to capture different parts of Megaunit B strata to capture high-resolution records of the Pliocene ocean-climate system at high Arctic latitudes.
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This content will become publicly available on March 24, 2026
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).
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- PAR ID:
- 10579119
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- International Ocean Discovery Program
- Date Published:
- Journal Name:
- Proceedings of the International Ocean Discovery Program Expedition reports
- Volume:
- 400
- Issue:
- 106
- ISSN:
- 2377-3189
- ISBN:
- 978-1-954252-93-6
- Subject(s) / Keyword(s):
- International Ocean Discovery Program IODP JOIDES Resolution Expedition 400 NW Greenland Glaciated Margin Site U1606 Baffin Bay Pliocene/Pleistocene boundary intensification of Northern Hemisphere glaciation meridional heat transport contourite drift ice-rafted debris IRD continental shelf
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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