East Antarctic outlet glacier contributions to the Ross Sea from chronology of detrital grains (NSF grant)
The PIs proposed a provenance study of glacial deposits in the Ross Embayment that will provide a broad scale geochronologic survey of detrital minerals in till to help characterize bedrock beneath the East Antarctic ice sheet and constrain Antarctica?s glacial history. This project capitalizes on previous investments in field sampling. Analytical tools applied to single mineral grains extracted from existing collections of glacial till will generate ?fingerprints? of East Antarctic outlet glaciers and West Antarctic till to refine paleo-ice flow models for the Ross Embayment during the last glacial maximum, older records from ANDRILL cores, and to assess IRD sources in the Southern Ocean. New provenance tracers will include a suite of geochronological methods that together provide greater insights into the orogenic and erosional history the region. This project will include U/Pb of detrital zircons, (U-Th)/He on a subset of the U/Pb dated zircons, as well as Ar-Ar of detrital hornblende, mica and feldspars.
*Welke, B., Licht K., *Hennessy, A., Hemming, S., Pierce-Davis, E., *Kassab, C., in press. Applications of detrital geochronology and thermochronology from glacial deposits to the Paleozoic and Mesozoic thermal history of the Ross Embayment, Antarctica. Geochemistry, Geophysics, Geosystems.
Licht, K.J., Hennessy, A.J., and Welke, B.M. (2014) The U/Pb detrital zircon signature of West Antarctic ice stream tills in the Ross Embayment, with implications for LGM ice flow reconstructions. Antarctic Science.
Pleistocene East Antarctic Ice Sheet history as recorded in sediment provenance and chronology of high-elevation TAM moraines (NSF grant)
The proposed work will investigate changes in the compositional variation of glacial tills over time across two concentric sequences of Pleistocene moraines located adjacent to the heads of East Antarctic outlet glaciers in the Transantarctic Mountains (TAM). The chronologic framework for this work will be generated from cosmogenic exposure ages of boulders on prominent morainal ridges. The PIs hypothesize that variations in till composition may indicate a change in ice flow direction or a change in the composition of the original source area, while ages of the moraines provide a long-term terrestrial perspective on ice sheet dynamics. Both results are vital for modeling experiments that aim to reconstruct the East Antarctic Ice Sheet and assess its role in the global climate system and its potential impact on global sea level rise. The variation of till compositions through time also allows for a more accurate interpretation of sediment cores from the Ross Sea and the Southern Ocean. Additionally, till exposures at the head of some East Antarctic outlet glaciers have been shown to contain subglacial material derived from East Antarctic bedrock, providing a window through the ice to view East Antarctica’s inaccessible bedrock. Till samples will be collected from two well-preserved sequences of moraine crests at Mt. Howe (head of Scott Glacier) and Mt. Achernar (between Beardmore and Nimrod Glaciers). Each size fraction in glacial till provides potentially valuable information, and the PIs will measure the petrography of the clast and sand fractions, quantitative X-ray diffraction on the crushed <2mm fraction, elemental abundance of the silt/clay fraction, and U/Pb of detrital zircons in the sand fraction. Data collection will rely on established methods previously used in this region and the PIs will also explore new methods to assess their efficacy. On the same moraines crests sampled for provenance studies, the PIs will sample for cosmogenic surface exposure analyses to provide a chronologic framework at the sites for provenance changes through time.
Integrated study of East Antarctic Ice Sheet Tills (ISET): Tracers of ice flow and proxies of the ice-covered continental shield (NSF grant)
This project studies till from the glaciers that drain the East Antarctic ice sheet through the Transantarctic Mountains into the Ross Embayment. Glaciers from both East and West Antarctica converge in this area, creating the Ross Ice Shelf, whose size is a sensitive indicator of global climate change. This work will determine till provenance through petrologic, geochemical, and isotopic studies. Its goal is to understand the flow paths of ice sheets into this area during the late Quaternary period, especially focused on the last glacial maximum approximately 18,000 yrs ago. This knowledge is critical to modeling ice sheet formation and behavior. While the East Antarctic ice sheet is considered stable, West Antarctica hosts rapidly flowing ice streams that may be affected by global climate change. The work will also improve our knowledge of the crustal rocks of East Antarctica. Covered by kilometer-thick ice sheets, its basic geology is largely unknown. The provenance studies will also be used in field-based curriculum workshops for Indiana Earth Science educators. Other broader impacts include graduate and undergraduate education, and improving society’s understanding of global climate change. Antarctica’s ice sheets play a pivotal role in atmospheric and oceanic circulation, and are key factors in sea-level rise. Models of ice sheet behavior rely on accurate reconstructions of past ice sheet configurations that this study will provide.
Licht, K.J., and *Palmer, E.F., 2013. Erosion and transport by Byrd Glacier, Antarctica during the last glacial maximum. Quaternary Science Reviews, v.62, p.32-48.
*Palmer, E.F., Licht, K.J., Swope, R.J., and Hemming, S.R., 2012. Nunatak moraines as a repository of what lies beneath the East Antarctic ice sheet, in Rasbury, E.T., Hemming, S.R., and Riggs, N.R., eds., Mineralogical and Geochemical Approaches to Provenance. Geological Society of America Special Paper 487, 97–104, doi:10.1130/2012.2487(05).
Goodge, J., Fanning, M., Brecke, D., Licht, K., *Palmer, E., 2010. Continuation of the Laurentian Grenville province across the Ross Sea margin of Antarctica. Journal of Geology, v. 118, p. 601-619.
Paleo ice flow paths from till provenance in the Ross Embayment, Antarctica (NSF grant)
This award supports a collaborative research project to study glacio-marine sediments from the Ross Sea toward an understanding of the history of the West Antarctic Ice Sheet (WAIS). Reliable predictions of the future response of the WAIS to changing climate and rising sea level depend, to a large extent, on improving our knowledge and understanding of its ice dynamics during the last glacial maximum (~18,000 yrs ago). Sediments from the Ross Sea, Antarctica, contain a detailed physical record that can be used to reconstruct past glacier flow patterns. Although significant progress has been made in constraining the extent of ice and the timing of its maximum extent, reconstructions of ice flow paths vary substantially. Studies have predicted that ice streams (regions of fast flowing ice) derived primarily from West Antarctica were dominant features of the Ross Ice Sheet, whereas an ice sheet modeling reconstruction showed roughly equal input from East and West Antarctic ice. Fundamental differences in rock types and ages beneath these source areas should allow the provenance of tills across the Ross Sea to be determined, facilitating the reconstruction of past ice flow paths. Thus the Ross Embayment provides an exciting opportunity to relate modern ice flow dynamics to past ice sheet dynamics and deposits.
Licht, K.J., *Lederer, J.R., Farmer, G.L., Swope, R.J., and Andrews, J.T., 2006. Petrographic and Isotopic Composition of Late Quaternary Ross Embayment Till. Terra Antarctica Reports No. 12. p.35-42.
Farmer, G.L., Licht, K., Swope, R.J., and Andrews, J.T., 2006. Isotopic constraints on the provenance of fine-grained sediment in LGM till from the Ross Embayment, Antarctica. Earth and Planetary Science Letters, v.249, p.90-107.
Licht, K.J., *Lederer, J.R., and Swope, R.J., 2005. Provenance of LGM Glacial Till (sand fraction) across the Ross Embayment, Antarctica. Quaternary Science Reviews, v.24, p.1499-1520.