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Title: Site U1452
Site U1452 (proposed Site MBF-5A) is in the center of our seven-site transect. It is located in a relatively flat environment with a smooth morphology. Topographic expressions of channels are absent in the vicinity of the site. The seismic profile at this site reveals a prominent, >20 km wide, and up to 40 m thick levee; the top is only at ~5 m below the seafloor. At this site, we focused on coring the upper levee to provide a detailed record of this type of depositional system. Two holes were cored through this levee to allow high-resolution sedimentological, geophysical, geochemical, and micropaleontological investigations. A single mudline core from Hole U1452A was devoted to detailed study of the hemipelagic deposition during the last glacial cycle and to the Toba ash. Hole U1452B was cored to 217.7 m drilling depth below seafloor (DSF) for the study of the Upper Pleistocene section. Finally, Hole U1452C was cored to 41.3 m DSF to provide a more complete record of the levee and to allow more extensive sampling.  more » « less
Award ID(s):
1326927
PAR ID:
10578908
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more » ; ; ; ; ; ; ; ; ; ; ; ; ; ; « less
Publisher / Repository:
International Ocean Discovery Program
Date Published:
Journal Name:
Proceedings of the International Ocean Discovery Program Expedition reports
Volume:
354
Issue:
106
ISSN:
2377-3189
ISBN:
978-1-954252-47-9
Subject(s) / Keyword(s):
International Ocean Discovery Program IODP Expedition 354 JOIDES Resolution Site U1452 Bengal Fan
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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    Site U1449 (proposed Site MBF-6A) is part of our seven-site transect designed to document turbiditic transport processes and the architecture of deposition in the Middle Bengal Fan at 8°N since the Pleistocene. Sediments will also be used to trace sources of eroded material in the Himalaya and reconstruct erosion rates as a function of climate change. Site U1449 is located at 08°0.419′N, 088°6.599′E in a water depth of 3653 m. The main Hole U1449A penetrated to 213.5 m drilling depth below seafloor (DSF) and was cored by a combination of the advanced piston corer (APC), half-length APC (HLAPC), and extended core barrel (XCB) systems. Hole U1449B consists of a single APC core from the mudline taken for microbiological studies. 
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  2. ; ; (, Preliminary report)
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The principal goals of Expedition 374 were to • Evaluate the contribution of West Antarctica to far-field ice volume and sea level estimates; • Reconstruct ice-proximal atmospheric and oceanic temperatures to identify past polar amplification and assess its forcings and feedbacks; • Assess the role of oceanic forcing (e.g., sea level and temperature) on AIS stability/instability; • Identify the sensitivity of the AIS to Earth’s orbital configuration under a variety of climate boundary conditions; and • Reconstruct eastern Ross Sea paleobathymetry to examine relationships between seafloor geometry, ice sheet stability/instability, and global climate. 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Cores from this site will provide a record of the changing vigor of the ASC through time. Such a reconstruction will enable testing of the hypothesis that changes in the vigor of the ASC represent a key control on regulating heat flux onto the continental shelf, resulting in the ASC playing a fundamental role in ice sheet mass balance. We also cored two sites on the continental slope and rise. At Site U1524, we cored a Plio–Pleistocene sedimentary sequence on the continental rise on the levee of the Hillary Canyon, which is one of the largest conduits of Antarctic Bottom Water delivery from the Antarctic continental shelf into the abyssal ocean. Drilling at Site U1524 was intended to penetrate into middle Miocene and older strata but was initially interrupted by drifting sea ice that forced us to abandon coring in Hole U1524A at 399.5 m drilling depth below seafloor (DSF). We moved to a nearby alternate site on the continental slope (U1525) to core a single hole with a record complementary to the upper part of the section recovered at Site U1524. We returned to Site U1524 3 days later, after the sea ice cleared. We then cored Hole U1524C with the rotary core barrel with the intention of reaching the target depth of 1000 m DSF. However, we were forced to terminate Hole U1524C at 441.9 m DSF due to a mechanical failure with the vessel that resulted in termination of all drilling operations and a return to Lyttelton 16 days earlier than scheduled. The loss of 39% of our operational days significantly impacted our ability to achieve all Expedition 374 objectives as originally planned. In particular, we were not able to obtain the deeper time record of the middle Miocene on the continental rise or abyssal sequences that would have provided a continuous and contemporaneous archive to the high-quality (but discontinuous) record from Site U1521 on the continental shelf. The mechanical failure also meant we could not recover sediment cores from proposed Site RSCR-19A, which was targeted to obtain a high-fidelity, continuous record of upper Neogene and Quaternary pelagic/hemipelagic sedimentation. Despite our failure to recover a shelf-to-rise transect for the Miocene, a continental shelf-to-rise transect for the Pliocene to Pleistocene interval is possible through comparison of the high-quality records from Site U1522 with those from Site U1525 and legacy cores from the Antarctic Geological Drilling Project (ANDRILL). 
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  3. ; ; (, Proceedings of the International Ocean Discovery Program)
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International Ocean Discovery Program Expedition 374 drilled a latitudinal and depth transect of five sites from the outer continental shelf to rise in the central Ross Sea to resolve Neogene and Quaternary relationships between climatic and oceanic change and WAIS evolution. The Ross Sea was targeted because numerical ice sheet models indicate that this sector of Antarctica responds sensitively to changes in ocean heat flux. Expedition 374 was designed for optimal data-model integration to enable an improved understanding of Antarctic Ice Sheet (AIS) mass balance during warmer-than-present climates (e.g., the Pleistocene “super interglacials,” the mid-Pliocene, and the Miocene Climatic Optimum). The principal goals of Expedition 374 were to: 1. Evaluate the contribution of West Antarctica to far-field ice volume and sea level estimates; 2. Reconstruct ice-proximal oceanic and atmospheric temperatures to quantify past polar amplification; 3. Assess the role of oceanic forcing (e.g., temperature and sea level) on AIS variability; 4. Identify the sensitivity of the AIS to Earth’s orbital configuration under a variety of climate boundary conditions; and 5. Reconstruct Ross Sea paleobathymetry to examine relationships between seafloor geometry, ice sheet variability, and global climate. To achieve these objectives, postcruise studies will: 1. Use data and models to reconcile intervals of maximum Neogene and Quaternary ice advance and retreat with far-field records of eustatic sea level; 2. Reconstruct past changes in oceanic and atmospheric temperatures using a multiproxy approach; 3. Reconstruct Neogene and Quaternary sea ice margin fluctuations and correlate these records to existing inner continental shelf records; 4. Examine relationships among WAIS variability, Earth’s orbital configuration, oceanic temperature and circulation, and atmospheric pCO2; and 5. Constrain the timing of Ross Sea continental shelf overdeepening and assess its impact on Neogene and Quaternary ice dynamics. Expedition 374 departed from Lyttelton, New Zealand, in January 2018 and returned in March 2018. We recovered 1292.70 m of high-quality core from five sites spanning the early Miocene to late Quaternary. Three sites were cored on the continental shelf (Sites U1521, U1522, and U1523). At Site U1521, we cored a 650 m thick sequence of interbedded diamictite and diatom-rich mudstone penetrating seismic Ross Sea Unconformity 4 (RSU4). The depositional reconstructions of past glacial and open-marine conditions at this site will provide unprecedented insight into environmental change on the Antarctic continental shelf during the late early and middle Miocene. At Site U1522, we cored a discontinuous late Miocene to Pleistocene sequence of glacial and glaciomarine strata from the outer shelf with the primary objective of penetrating and dating RSU3, which is interpreted to reflect the first continental shelf–wide expansion of East and West Antarctic ice streams. Site U1523, located on the outer continental shelf, targeted a sediment drift beneath the westward-flowing Antarctic Slope Current (ASC) to test the hypothesis that changes in ASC vigor regulate ocean heat flux onto the continental shelf and thus ice sheet mass balance. We also cored two sites on the continental rise and slope. At Site U1524, we recovered a Plio–Pleistocene sedimentary sequence from the levee of the Hillary Canyon, one of the largest conduits of Antarctic Bottom Water from the continental shelf to the abyssal ocean. Site U1524 was designed to penetrate into middle Miocene and older strata, but coring was initially interrupted by drifting sea ice that forced us to abandon coring in Hole U1524A at 399.5 m drilling depth below seafloor (DSF). We moved to a nearby alternate site on the continental slope (Site U1525) to core a single hole designed to complement the record at Site U1524. We returned to Site U1524 after the sea ice cleared and cored Hole U1524C with the rotary core barrel system with the intention of reaching the target depth of 1000 m DSF. However, we were forced to terminate Hole U1524C at 441.9 m DSF because of a mechanical failure with the vessel that resulted in termination of all drilling operations and forced us to return to Lyttelton 16 days earlier than scheduled. The loss of 39% of our operational days significantly impacted our ability to achieve all Expedition 374 objectives. In particular, we were not able to recover continuous middle Miocene sequences from the continental rise designed to complement the discontinuous record from continental shelf Site U1521. The mechanical failure also meant we could not recover cores from proposed Site RSCR-19A, which was targeted to obtain a high-fidelity, continuous record of upper Neogene and Quaternary pelagic/hemipelagic sedimentation. Despite our failure to recover a continental shelf-to-rise Miocene transect, records from Sites U1522, U1524, and U1525 and legacy cores from the Antarctic Geological Drilling Project (ANDRILL) can be integrated to develop a shelf-to-rise Plio–Pleistocene transect. 
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  4. ; ; ; ; ; ; ; ; ; ; et al (, Proceedings of the International Ocean Discovery Program)
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  5. ; ; ; ; ; ; ; ; ; ; et al (, Proceedings of the International Ocean Discovery Program Expedition reports)
    Site U1604 (proposed Site MB-02C) was cored on the lower slope below the Melville Bugt Trough Mouth Fan (TMF) at 1943 meters below sea level (mbsl) at 73°06.9077′N, 63°47.3996′W below a prominent crescent-shaped protrusion of the Melville Bugt TMF on the northwest Greenland shelf margin (Figure F1). The site was aimed at retrieving a continuous high-resolution record of ice sheet–ocean interactions and processes going back to early Pleistocene. The depth target was the base of an expanded drift channel succession situated on the lower slope between two paleo–ice sheet outlets representing major drainage routes for the northern Greenland ice sheet (NGrIS) into Baffin Bay (Knutz et al., 2019; Newton et al., 2017, 2020, 2021). The sedimentary succession is covered by regional 2D industry data as well as high-resolution multichannel seismic data providing a detailed seismic stratigraphy to guide the drilling objectives (Figure F2). The strategy at Site U1604 was to core through the youngest seismic units (9–11) to capture the expanded depositional sequence within Seismic Unit 8 showing stratified intervals with asymmetric geometries resembling contourite drifts. Site U1604 is paired seismic-stratigraphically with Site U1603, located 16 nmi (~30 km) to the southeast adjacent to a deepwater channel. With Horizon 7 as a stratigraphic target (about 420 meters below seafloor [mbsf]), the succession cored at Site U1604 is complementary to Site U1603 but records sedimentation that is more distal to the channel system and presumably recovers an interval older than at Site U1603. 
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