MeBo70 Seabed Drilling on a Polar Continental Shelf: Operational Report and Lessons From Drilling in the Amundsen Sea Embayment of West Antarctica

Abstract

A multibarrel seabed drill rig was used for the first time to drill unconsolidated sediments and consolidated sedimentary rocks from an Antarctic shelf with core recoveries between 7% and 76%. We deployed the MARUM‐MeBo70 drill device at nine drill sites in the Amundsen Sea Embayment. Three sites were located on the inner shelf of Pine Island Bay from which soft sediments, presumably deposited at high sedimentation rates in isolated small basins, were recovered from drill depths of up to 36 m below seafloor. Six sites were located on the middle shelf of the eastern and western embayment. Drilling at five of these sites recovered consolidated sediments and sedimentary rocks from dipping strata spanning ages from Cretaceous to Miocene. This report describes the initial coring results, the challenges posed by drifting icebergs and sea ice, and technical issues related to deployment of the MeBo70. We also present recommendations for similar future drilling campaigns on polar continental shelves.

Evidence for a Highly Dynamic West Antarctic Ice Sheet During the Pliocene

“…Prior to investigation with scientific drilling, previous models of the stratigraphic architecture and ages of shelf and rise sedimentary sequences in the Amundsen Sea (Gohl et al., 2013; Uenzelmann‐Neben & Gohl, 2012, 2014) were based only on long distance or jump correlation of regional seismic reflection profiles to the seismic stratigraphy of the Ross Sea tied to Deep Sea Drilling Project (DSDP) Leg 28 sites (e.g., De Santis et al., 1999) as well as to DSDP Leg 35 and Ocean Drilling Program (ODP) Leg 178 sites west of the Antarctic Peninsula (Barker et al., 2002; Tucholke et al., 1976). Recently, shelf sediments in the ASE were drilled with the MARUM‐MeBo70 sea‐bed drilling device in 2017, recovering sedimentary rocks of Cretaceous to Oligocene‐Miocene age (Gohl et al., 2017; Klages et al., 2020). The almost continuous sequences at IODP Expedition 379 Sites U1532 and U1533 on the continental rise (Gohl et al., 2021; Wellner et al., 2021a, 2021b) span the latest Miocene to Holocene with high core recovery rates of 90% and 70%, respectively (Figure 1).…”

Elevated geothermal surface heat flow in the Amundsen Sea Embayment, West Antarctica

“…The ice sheet modeling community (e.g. Golledge et al, 2015) repeatedly outlined the importance of better constrained thermal boundary conditions to enhance the accuracy of ice sheet model performance for future sea level rise predictions. Moreover, Barletta et al (2018) demonstrate that the solid-Earth deformation exerts an important control on the possibility of future West Antarctic Ice Sheet (WAIS) collapse.…”

Volume 379: Amundsen Sea West Antarctic Ice Sheet History

“…Seismic records from the Amundsen Sea shelf show dipping strata on the midshelf that are possibly of Cretaceous to Miocene age and buried by aggradational, less consolidated strata of presumed Pliocene-Pleistocene age (Lowe and Anderson, 2002;Gohl et al, 2013b). Preliminary results from a seabed drilling expedition place constraints on the Cretaceous sequences that overlie outcropping bedrock on the middle and inner shelf in Pine Island Trough (Gohl et al, 2017). Since the mid-Miocene, the outer shelf and slope have undergone first progradational and then aggradational deposition (Nitsche et al, 1997;Hochmuth and Gohl, 2013;Gohl et al, 2013b).…”