We apply the 39Ar/40Ar dating method to detrital hornblende grains, in conjunction with other geochemical measurements (e.g. U-Pb zircon, Nd and Sr isotopes of fine terrigeous sediments, and (U-Th)/He and fission track dating of detrital apatite and zircon) in order to 1) better understand the evolution of the East Antarctic Ice Sheet and 2) characterize the subglacial geology and 3) investigate the landscape evolution of East Antarctica. This collective work involves several collaborations with scientists at Imperial College, IUPUI, The University of Arizona, and Montclair State.
East Antarctic Ice Sheet History
Graduate student Elizabeth Pierce is working on sedimentary provenance studies to better understand the evolution of the East Antarctic ice sheet. The distinctive ages of different parts of East Antarctica make it ideal for applications of sedimentary provenance studies to understanding this history of the East Antarctic ice sheet. East Antarctica is characterized by distinctive provenance sectors with Ross (450-550 Ma), Pan-African (500 -600 Ma), Grenville (1100-1300 Ma) and Paleoproterozoic ages. ODP core 1165, located off of Prydz Bay, records changes in the provenance of ice rafted detritus (IRD) over a 20 million year period. 40Ar/39Ar ages of hornblendes from IRD-rich layers in ODP core 1165 indicate sourcing of grains from Adélie Land and George V Land at different times in the past, indicating major fluctuations in the East Antarctic ice sheet since the mid-Miocene (Williams et al., 2010). Motivated by these initial findings, we have measured 40Ar/39Ar ages of glacially derived hornblends, biotites and feldspars from marine sediment cores off the coast of East Antarctica, from the Ross Sea east to Prydz Bay, in order to better characterize the age of material being shed from under the ice sheet, and explore the use of 40Ar/39Ar biotite ages as a provenance tracer (Pierce et al., 2009).
Presently, work is underway to look in more detail at shifts in IRD provenance recorded in ODP core 1165. Our group is also excited to soon be working on samples from the recently completed IODP Wilkes Land Expedition, which drilled through to Eocene sediments off the Wilkes Land margin, and which will provide further constraints on the evolution and past stability of the East Antarctica ice sheet.
Ninety-eight percent of Antarctica is covered by ice (averaging ~1 km thick in West Antarctica, and ~3 km thick in East Antarctica), making it difficult to directly study the underlying geology. Antarctica has been integral in past continental configurations, and so in order to better reconstruct paleogeography, it is important to understand the geochronology and thermochronology of the underlying bedrock. In order to indirectly sample the geology that is obscured by the ice, we used sediments obtained from marine sediment cores around the Antarctic perimeter. By dating minerals found within the sediments, all of which have different closure temperatures (zircons (Tc=900C), hornblendes (Tc=500C), biotites (Tc=300C), feldspars (250-300C, and muscovite (Tc=400C), we are able to learn more about the underlying geology, uplift patterns and erosional histories. 40Ar/39Ar ages of ice rafted hornblende grains from marine coretop sediments around the Antarctic perimeter (Roy et al., 2010) reproduce the geological story from field observations of very limited outcrops. Most East Antarctic perimeter cores are characterized by predominant ~500 Myr 40Ar/39Ar ages but 40Ar/39Ar ages along the Wilkes Land margin include significant populations of Mesoproterozoic and Paleoproterozoic ages, and even some Archean ages (Pierce et al., 2009). Along the coast of Droning Maud Land, in the Eastern Weddell Sea, 40Ar/39Ar hornblende ages and U-Pb zircon ages vary along the margin, but collectively show peaks at 500 and 1000 Ma (Steponaitis et al., 2008).We currently have collected data from the George V, Adélie, Wilkes, Prydz Bay area and Droning Maud Land coasts, and are in the process of analyzing more samples from locations around East Antarctica.
Pierce, E.L., Williams, T., van de Flierdt, T., Hemming, S.R., Brachfeld, S.A., Goldstein, S.L. (in press: Paleoceanography): Characterizing the sediment provenance of East Antarctica’s weak underbelly: the Aurora and Wilkes sub-glacial basins. doi:10.1029/2011PA002127.
Cox, S. E., 2009. An investigation of the exhumation history of the Gamburtsev Mountains through low-temperature thermochronology of detrital sediments in Prydz Bay, East Antarctica. Senior thesis, Columbia College, May 5, 2009
Cox, S.E., Reiners, P.W., Thomson, S.N., Gehrels, G.E., Nicolescu, S., Hemming,
S.R., Van de Flierdt. T., Goldstein, S.L., Brachfeld., S.A., 2008, "Triple-dating of detrital apatites and zircons from Prydz Bay, East Antarctica, 8th Annual V M Goldschmidt Conference., v.72, 2008, p. A187-A187.
Cox, S.E., Reiners, P.W., Thomson, S.N., Gehrels, G.E., Nicolescu, S., Hemming,
S.R., Van de Flierdt. T., Goldstein, S.L., Brachfeld., S.A., 2008, Hints about the formation of the Gamburtsev subglacial mountains from triple-dating detrital apatite and zircon in Abstract Volume for SCAR/IASC IPY Open Science Conference p. 70.
Cox, S. E., Hemming, S. R., Reiners, P. W., Nicolescu, S., Thomson, S. N., Gehrels, G. E., van de Flierdt, T., Goldstein, S. L., and Brachfeld, S. A., 2007. Detrital apatite and zircon (U-Th)/He evidence for early formation and slow erosion of the Gamburtsev Mountains, East Antarctica, in Antarctica: A Keystone in a Changing World – Online Proceedings of the 10th ISAES X, edited by A. K. Cooper and C. R. Raymond et al., USGS Open-File Report
Dale, C.L., 2009. Geochemical and petrographic signatures from Marie Byrd Land and Larsen-B ice shelf sediments: Implications for provenance trading. M.S. Thesis, Montclair State University, 72 pp.
Licht, K., and *Palmer, E., 2007. Characteristics of till transported by the Byrd and Nimrod Glaciers, Antarctica. In Antarctica: A Keystone in a Changing World – Online Proceedings of the 10th ISAES X, edited by A.K. Cooper and C.R. Raymond et al., USGS Open-File Report 2007-1047, Extended Abstract 114.
Palmer, E.F., Licht, K.J., Hemming, S.R., 2008, Tracing glacial material into the Ross Sea using U/Pb, 40Ar/39Ar and petrographic analyses of detritus, in Abstract Volume for SCAR/IASC IPY Open Science Conference p. 78.
Palmer, E. F., Licht, K. J., Swope, J., and Hemming, S. R., submitted, A glimpse of the ice covered East Antarctic craton from the Lonewolf Nunataks, Antarctica, for Geology.
Pierce, E.L., Williams, T., van de Flierdt, T., Hemming, S.R., Goldstein, S.L. and
Brachfeld, S.A, 2008, Ar-Ar ages of glacially transported hornblende, Wilkes Land, Antarctica, in Abstract Volume for SCAR/IASC IPY Open Science Conference p. 79.
*Pierce, E.L., Williams, T., van de Flierdt, T., Hemming, S.R., Goldstein, S.L. and
Brachfeld, S.A, 2008, Ar-Ar ages of glacially transported hornblende, Wilkes Land, Antarctica, Geochimica et Cosmochimica Acta, V 72, N12S, p. A747.
Pierce, E.L., Williams, T., van de Flierdt, T., Hemming, S.R., Goldstein, S.L., and Brachfeld, S.A., 2009, 40Ar/39Ar Thermochronology of Australia’s conjugate margin in Antarctica form ice-rafted hornblende, biotite and feldspar grains, Geological Society of America Abstracts with Programs, Vol. 41, No. 7, p. 427.
Pierce, E.L., **Steponaitis, E., **Cox, S.E., Gehrels, G.E., Hemming, S.R., Goldstein, S.L., Brachfeld, S.A., van de Flierdt, T., Williams, T., 2009, U-Pb zircon and 40Ar/39Ar hornblende ages of glaciogenic detritus around East Antarctica, Geochimica et Cosmochimica Acta, V 73, p. A1027.
Roy, M., T. van de Flierdt, S. R. Hemming, and S. L. Goldstein (2007), 40Ar/39Ar ages of hornblende grains and bulk Sm/Nd isotopes of circum-Antarctic glacio-marine sediments: Implications for sediment provenance in the southern ocean, Chemical Geology, 244(3-4), 507-519.
Steponaitis E., G.E. Gerhrels, S.R. Hemming, T. van de Flierdt, S.L. Goldstein, S.A. Brachfeld., 2008, Hornblende Ar-Ar and zircon U-Pb evidence for provenance of eastern Weddell Sea glaciogenic sediments, Antarctica, 8th Annual V M Goldschmidt Conference, Pergamon-Elsevier Science Ltd., Pages:A897-A897, ISSN:0016-7037
Van de Flierdt, T., Hemming S.R., Goldstein S.L., Gehrels G.E., Cox S.E., 2008, Evidence against a young volcanic origin of the Gamburtsev Subglacial Mountains, Antarctica, Geophysical Research Letters, v. 35, L21303.
Williams, T., T. van de Flierdt, S.R. Hemming, E. Chung, M. Roy, S.L. Goldstein, 2010, Evidence for iceberg armadas from East Antarctica in the Southern Ocean during the late Miocene and early Pliocene. Earth and Planetary Science Letters 290, 351-361.