Marine sediments, obtained from cores and captures from deep sea and continental shelf sites of West Antarctica, contain rich records of latest Miocene to Present glacial and deglacial processes and conditions at the margin of the West Antarctic ice sheet (WAIS). The materials we are investigating were recovered from a) Resolution Drift on the Amundsen Sea continental rise (water depths >3900m), b)the continental shelf in the Amundsen Sea, Wrigley Gulf, and Sultzberger Bay (water depths <1000m). Resolution Drift cores were drilled by IODP Expedition 379 (Gohl et al., doi:10.14379/iodp.proc.379.2021) in sediments dominated by compacted clay and silty clay, with conglomeratic intervals of ice-rafted detritus (IRD) and downslope deposits. The shelf sediments were recovered by piston core, trigger core, and Smith McIntyre Grab (SMG) during USA research cruises of the RVIB Nathaniel B Palmer (1999, 2000, 2007) and USCGC Glacier (1983). The shelf samples are non-compacted clay, containing abundant cobbles, pebbles and biogenic fragments.
Our research focuses upon rock clasts, detrital apatite and zircon, felsic volcanic tephra, and micro-manganese nodules separated from marine and glaciomarine clay. The rock clasts and detrital minerals represent samples of continental crust that we characterise according to rock type, petrology, geochemistry, and geo-thermochronology [U-Pb, (U-Th)/He, and fission track methods]. These characteristics illuminate solid Earth processes, including the development of subglacial topography . We compared clasts’ petrology and age data to the exposed onshore geology and thermochronology of bedrock, and determined that ≥90% of clasts likely originated in West Antarctica. Therefore the materials can be used to assign roughness, erodibility, and heat production factors for subglacial bedrock, which constitute boundary conditions used by ice sheet modelers.
Rhyolite ash and fragments provide new evidence for explosive eruptions (dated ca. 2.55 to 2.92 Ma; feldspar 40Ar/39Ar) delivered to sea as airfall, IRD, and possible subglacial water transport. Silicic eruptions produce ash and aerosols that may screen solar energy, and provide bio-available nutrients that produce phytoplankton blooms leading to sequestration of carbon. The rhyolite dates coincide with the end of a Pliocene warm period recorded in IODP379 cores (Gille-Petzoldt et al., 10.3389/feart.2022.976703). Our work in progress seeks to obtain higher resolution geochronology in order to determine whether silicic continental volcanism occurred in response to ice unloading due to deglaciation (cf. Lin et al., 10.5194/cp-18-485-2022) and whether erupted products contributed to latest Pliocene significant cooling and WAIS re-glaciation.
Another distinctive sediment constituent is micro-manganese nodules of unusual form. Whereas typical micro-MN nodules are dark, formed of concentric layers, this form is pale in color, ‘barbell’ shaped, and transparent in transmitted light. Scanning electron microscopy shows these to be microcrystalline Mn-oxide with embedded grains of quartz and feldspar, which likely served as seed material. Mn-oxides form by authigenesis at/near the seafloor surface, requiring high oxygen concentrations in the bottom water and low sedimentation rates, generally associated with the end of glacials/during interglacials (Hillenbrand et al. 2021, 10.1029/2021GL093103). Work is in progress to determine whether Mn oxides formed through passive accretion upon seed grains or microbially-mediated precipitation from Mn-oxyhydroxides or colloids, of possible relevance for coastal carbon budgets.
https://doi.org/10.5194/egusphere-egu23-9728
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Enlisting historically excluded undergraduates in the effort to extend knowledge of West Antarctica’s bedrock, through course-based undergraduate research experiences (cures) and Art-Science initiatives
An enormous reserve of information about the subglacial bedrock, tectonic and topographic evolution of Marie Byrd Land (MBL) exists within glaciomarine sediments of the Amundsen Sea shelf, slope and deep sea, and MBL marine shelf. Investigators of the NSF ICI-Hot and NSF Linchpin projects partnered with Arizona Laserchron Center to provide course-based undergraduate research experiences (CUREs) for from groups who do not ordinarily find access points to Antarctic science. Our courses enlist BIPOC and gender-expansive undergraduates in studies of ice-rafted debris (IRD) and bedrock samples, in order to impart skills, train in the use of research instrumentation, help students to develop confidence in their scientific abilities, and collaboratively address WAIS research questions at an early academic stage. CUREs afford benefits to graduate researchers and postdoctoral scientists, also, who join in as instructional faculty: CUREs allow GRs and PDs to engage in teaching that closely ties to their active research, yet provides practical experience to strengthen the academic portfolio (Cascella & Jez, 2018). Team members also develop art-science initiatives that engage students and community members who may not ordinarily engage with science, forging connections that make science relatable. Re-casting science topics through art centers personal connections and humanizes science, to promote understanding that goes beyond the purely analytical.
Academic research shows that diverse undergraduates gain markedly from the convergence of art and science, and from involvement in collaborative research conducted within a CURE cohort, rather than as an individualized experience (e.g. Shanahan et al. 2022). The CUREs are offered as regular courses for credit, making access equitable via course enrollment. The course designation carries a legitimacy that is sought by students who balance academics with part-time employment. Course information is disseminated via STEM Bridge programs and/or an academic advising hub that reaches students from groups that are insufficiently represented within STEM and cryosphere science.
CURE investigation of Amundsen Sea and WAIS problems is worthy objective because: 1) A variety of sample preparation, geochemical methods, and scientific best-practices can be imparted, while educating students about Antarctica’s geological configuration and role in the Earth climate system. 2) Individual projects that are narrowly defined can readily scaffold into collaborative science at the time of data synthesis and interpretation. 3) There is a high likelihood of scientific discovery that contributes to grant objectives. 4) Enrolled students will experience ambiguity and instrumentation setbacks alongside their faculty and instructors, and will likely have an opportunity to withstand/overcome challenges in a manner that trains students in complex problem solving and imparts resilience (St John et al., 2019). Based on our experiences, we consider CUREs as a means to create more inclusive and equitable spaces for learning to do research, and a basis for a broadening future WAIS community. Our groups have yet to assess student learning gains and STEM entry in a robust way, but we can report that two presenters at WAIS 2022 came from our 2021 CURE, and four polar science graduate researchers gained experience via CURE teaching.
Data obtained by CURE students is contributing to our NSF projects’ aims to obtain isotope, age, and petrogenetic criteria with bearing on the subglacial bedrock geology, tectonic and landscape evolution, and ice sheet history of MBL.
Cited and recommended works:
Cascella & Jez, 2018, doi: 10.1021/acs.jchemed.7b00705
Gentile et al., 2017, doi: 10.17226/24622
Shanahan et al. 2022, https://www.cur.org/assets/1/23/01-01_TOC_SPUR_Winter21.pdf
Shortlidge & Brownell, 2016, doi: 10.1128/jmbe.v17i3.1103
St. John et al. 2019, EOS, doi: 10.1029/2019EO127285.
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- NSF-PAR ID:
- 10376640
- Date Published:
- Journal Name:
- 29th West Antarctic Ice Sheet workshop
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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