14-12. Constructing a late Quaternary tephrostratigraphy across southern Alaska -- Elucidating eruptive histories, assessing tephra-fall hazards, and linking marine & lacustrine records of climate variability
This Research Opportunity is targeted at postdoctoral scientists interested in studying tephrostratigraphic records of late Quaternary age across southern Alaska preserved in terrestrial and marine settings. The research will focus on: [i] synthesis of existing tephra records obtained by other lake and marine coring studies; [ii] analysis and evaluation of existing (but yet unstudied) lake and marine core records; and [iii] collection and analysis of new lake core tephra records from selected areas in south-central Alaska, the Alaska Peninsula and the Aleutian Islands. The goal of the research is to integrate tephrostratigraphic data into frequency-magnitude estimates of past eruptions, develop correlations of tephra records across broad areas of southern Alaska and the Northern Hemisphere, and improve tephra-fall hazard assessments.
The Aleutian arc of Alaska is one of the most volcanically active regions in the world with ~90 volcanoes that have been active during the last 10,000 years. A common product of explosive eruptions is volcanic ash, which can be a significant hazard as well as an important stratigraphic marker that enables linking, dating, and synchronizing geological, and paleoenvironmental events (Lowe, 2011). Studies of volcanic ash in lake and marine cores can aid in deciphering the frequency-magnitude relations of Holocene volcanic eruptions, which are critical for reconstructing the eruptive history of Aleutian arc volcanoes because they establish the temporal context for hazardous tephra-producing eruptions that have occurred in the past (Schiff et al., 2010).
Tephra records from Alaskan lakes have been under-utilized in volcanological studies of eruption frequency and magnitude, and thus offer new insight into the record of tephra-producing eruptions during the late Quaternary. Lake core records provide a unique opportunity to develop high-resolution age estimates of tephra deposits which act as “event horizons” that can be correlated among sites using physical and chemical characteristics, thus allowing the transfer of dated intervals in one location to be projected to other locations stratigraphically, and thus allow the synchronization of important records of climate change, ecosystem evolution, and surface processes (e.g., Preece et al., 2011; Pyne-O’Donnell et al., 2012).
Recent studies focused on tephrostratigraphic records obtained from lake sediment cores in south-central and southwest Alaska have shown that lake deposits contain a rich archive of tephra-fall events that can be superior to outcrop-based records (deFontaine et al., 2007; Schiff et al., 2010; Kaufman et al., 2012). For example, stratigraphic studies of unconsolidated eruptive products at Redoubt Volcano indicate about fourteen eruptive episodes during the Holocene (Beget and Nye, 1994). However, lake sediment records from nearby lakes suggest more than 50 (and possibly as many as 100) eruptive events of Holocene age have occurred at Redoubt Volcano (Schiff et al., 2010).
We seek a postdoctoral scientist to investigate tephrostratigraphic records obtained from lakes in southern Alaska and to integrate the results of this work with existing knowledge of past eruptions and ash-fall hazards. A secondary objective is the application of tephra correlations to link other geological records of marine and terrestrial environmental change, as Alaskan tephra deposits are common in sediments from marine continental shelf settings in the Gulf of Alaska and Bering Sea, varved lake records in southern Alaska, peat bogs from the Alaskan Interior, and ice cores in the Chugach/St. Elias Range, all of which also contain critical archives of paleoclimate information.
Successful applicants will be required to apply new or novel techniques useful in the identification and geochemical and physical analysis of volcanic ash. Potential candidates should be familiar with dating methods and correlation techniques applicable to tephra and lacustrine deposits of Holocene age and be familiar with applications of tephrochronology to other geological archives of environmental change. Facilities and equipment needed to successfully complete the research are available within USGS and Northern Arizona University. Experience with coring equipment and procedures in remote environments are desirably.
Beget, J. E., and Nye, C. J., 1994, Postglacial eruption history of Redoubt volcano, Alaska: Journal of Volcanology and Geothermal Research, v. 62, n. 1, p. 31-54.
de Fontaine, C.S., Kaufman, D.S., Anderson, R.S., Werner, A., Waythomas, C.F., and Brown, T.A., 2007, Late Quaternary distal tephra-fall deposits in lacustrine sediments, Kenai Peninsula, Alaska: Quaternary Research, v. 68, p. 64-78, doi:10.1016/j.yqres.2007.03.006.
Gudmundsdottir, E.R., Larsen, G., and Eiriksson, J., 2012, Tephra stratigraphy on the North Icelandic shelf: extending tephrochronology into marine sediments off North Iceland. Boreas, v. 41, p. 719-734.
Kaufman, D.S., Jensen, B.J.L., Reyes, A.V., Schiff, C.J., Froese, D.G., 2012, Late Quaternary tephrostratigraphy, Ahklun Mountains, southwestern Alaska. Journal of Quaternary Sciences, v. 27, p. 344-359.
Lowe, D., 2011, Tephrochronology and its application: a review. Quaternary Geochronology, v. 6, p. 107-153.
Pyne-O’Donnell, S.D.F., Hughes, P.D.M., Froese, D.G., Jensen, B.J.L., Kuehn, S.C., Mallon, G., Amesbury, M.J., Charman, D.J., Daley, T.J., Loader, N.J., Mauquoy, D., Street-Perrott, F.A., and Woodman-Ralph, J., 2012, High-precision ultra distal Holocene tephrochronology in North America. Quaternary Science Reviews, v. 52, p. 6-11.
Preece, S.J., Westgate, J.A., Froese, D.G., Pearce, N.J.C., and Perkins, W.T.A., 2011, Catalog of late Cenozoic tephra beds in the Klondike goldfields and adjacent areas, Yukon. Canadian Journal of Earth Science, v. 48, p. 1386-1418.
Schiff, C., Kaufman, D. S., Wallace, K. L., and Ketterer, M. E., 2010, An improved proximal tephrochronology for Redoubt Volcano, Alaska. Journal of Volcanology and Geothermal Research, v. 193, p. 203-214.
Proposed Duty Station: Anchorage, AK
Areas of Ph.D.: Volcanology, Quaternary geology, tephrochronology (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).
Qualifications: Applicants must meet one of the following qualifications: Research Geologist, Research Geophysicist, Research Geographer.
(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant’s background, education, and research proposal. The final classification of theposition will be made by the Human Resources specialist).
Research Advisors: Christopher F. Waythomas, (907) 786-7122, firstname.lastname@example.org.; Darrell Kaufman (Northern Arizona U), (928) 523-7192, Darrell.Kaufman@nau.edu.; Kristi Wallace, (907) 786-7109, email@example.com.; Jason A. Addison, (650) 329-5271, firstname.lastname@example.org.
|Summary of Opportunities|