by Tom Ager, Research Geologist (email: Tom Ager)
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This project involves reconstruction of the late Pleistocene and Holocene history of environmental change in Alaska, focusing upon the past 50,000 years. High latitude ecosystems are highly sensitive to climatic change. Understanding the history of environmental responses to past climate changes provides a basis for forecasting future responses to a variety of possible climatic scenarios. Information derived from this study has applications to ecology, paleoecology, paleoclimatology, archeology, vertebrate paleontology, and other fields. Understanding ecosystem history is also crucial for proper management of national forests, national and state parks, and wildlife refuges. The methods employed in this study involve sampling of deposits (bogs, lakes, and natural exposures) that contain fossil pollen, plant macrofossils, and sometimes ostracodes and diatoms. The project has focused mostly upon the late Pleistocene and Holocene history of (1) Tongass National Forest in southeastern Alaska; (2) south-central Alaska, including Chugach National Forest; and (3) western Alaska, Bering Sea and Chukchi Sea. |
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Figure 2. Present-day distribution of major vegetation types in Alaska. Conifer-dominated forests grow in areas where mean July temperatures are warmer than 11-12 degrees C. Map courtesy of Dan Muhs. |
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USGS Earth Surface Dynamics Program
(Previous Years)
Ager, T.A., 1998. Mid-Wisconsin interstadial vegetation in Alaska and Yukon Territory based on the fossil record: how extensive was the boreal forest? [abs.]: Program & Abstracts, 28th Arctic Workshop, March 12-14, 1998, Institute of Arctic & Alpine Research, University of Colorado, Boulder, p. 1-2.
Ager, T.A., 1999a. Late Quaternary history of vegetation and climate change in the Mount Harper area, Yukon-Tanana Upland, east-central Alaska [abs.]: Program and Abstracts, 50th Arctic Science Conference, American Association for the Advancement of Science, Denali National Park and Preserve, Alaska, September 19-22, 1999, p. 75.
Ager, T.A., 1999b. Late Wisconsin glacial and postglacial history of southeastern Alaska: Implications for ecosystem development and colonization by humans [abs.]: Geological Society of America Abstracts with Programs, v. 31, no. 7, p. A-367.
Ager, T.A., 2000. Postglacial vegetation history of the Kachemak Bay area, Cook Inlet, south-central Alaska, in Kelley, K., and Gough, L., eds.: U.S. Geological Survey Professional Paper 1615, p. 147-165.
Ager, T.A., 2001. Holocene vegetation history of the northern Kenai Mountains, south-central Alaska, in Gough, L., and Wilson, R., eds.: U.S. Geological Survey Professional Paper, 1633, p. 91-107.
Ager, T.A., 2002. Paleoenvironments of the Bering land bridge and the North Pacific coast during the late Wisconsin and early Holocene. Program and Abstracts of the 17th Biennial Meeting, American Quaternary Association, Anchorage, p. 10-12.
Ager, T.A., 2003. (Click on link to open 1 MB PDF) Late Quaternary vegetation and climate history of the central Bering land bridge from St. Michael Island, western Alaska: Quaternary Research, v. 60, p. 19-32.
Ager, T.A., Carrara, P.E., contributors to Kaufman, D.S. and Manley, W.F., 2002. Pleistocene maximum and late Wisconsin glacier extents across Alaska, U.S.A.: INQUA Commission of glaciation volume on glaciation in North America, scale 1:2,000,000.
Bigelow, N., and Ager, T.A., 2000. Interstadial vegetation at the Eva Creek site, Central Alaska [abs.]: Troy Pewe; Memorial workshop, Chena Hot Springs, Alaska, August 21-24, 2000, 1 page (unpaginated).
Carrara, P.E., Ager, T.A., Baichtal, J.F., and Van Sistine, D., 2002. Late Wisconsin glacial limits in southern southeastern Alaska, as indicated by a new bathymetric map, (abs). 32nd International Arctic Workshop, Institute of Arctic and Alpine Research, University of Colorado, Boulder, p. 41-43.
Carrara, P.E., Ager, T.A., Baichtal, J.F., and Van Sistine, D., 2002. Glacial limits and possible refugia in the southern Alexander Archipelago during the late Wisconsin, (abs). American Quaternary Association, abstracts of the 17th biennial meeting, Anchorage, Alaska, p. 23.
Carrara, P.E., Ager, T.A., Baichtal, J.F., and Van Sistine, D.P., 2003. Map of glacial limits and possible glacial refugia in southern Alexander Archipelago, Alaska during the late Wisconsin glaciation. U.S. Geological Survey Miscellaneous Field Studies Map MF-2424 (with text), scale 1:500,000.
Clague, J.J., Mathewes, R.W., and Ager, T.A., in press. Environments of northwestern North America before the last glacial maximum. In Madsen, D.B. (ed), Entering America: Northeast Asia and Beringia before the Last Glacial Maximum: University of Utah Press, Salt Lake City.
Duvall, M.L, Ager, T.A., Anderson, P.M., Bartlein, P.J., Bigelow, N.H., Brigham-Grette, J., Brubaker, L.B., Cwynar, L.C., Edwards, M.E., Eisner, W.R., Elias, S.A., Finney, B.P., Glushkova, O.Y., Hu, F.S., Kaufman, D.S., Lohzkin, A.V., Mock, C.J., Trumpe, M.A., and Webb, R.S., 1999. Announcement: Paleoenvironmental Atlas of Beringia presented in electronic form: Quaternary Research, v. 52, p. 270-271.
Edwards, M.E., Anderson, P.M., Brubaker, L.B., Ager, T.A., Andreev, A.A., Bigelow, N.H., Cwynar, L.C., Eisner, W.R., Harrison, S.P., Hu, F.-S., Jolly, D., Lozhkin, A.V., MacDonald, G.M., Mock, C.J., Ritchie, J.C., Sher, A.V., Spear, R.W., Williams, J.W., and Yu, G., 2000. (Click on link to open 4.8 MB PDF) Pollen-based biomes for Beringia 18,000, 6000, and 0 14C yr BP: Journal of Biogeography, v. 27, p. 521-554.
Froese, D.G., Smith, D.G., Westgate, J.A., Ager, T.A., Preece, S.J., Sandhu, A., Enkin, R.J., and Weber, F., 2003. (Click on link to open 1 MB PDF) Recurring middle Pleistocene outburst floods in east-central Alaska: Quaternary Research, v. 60, p. 50-62.
Kaufman, D.S., Ager, T.A., Anderson, N.J., Anderson, P.M., Andrews, J.T., Bartlein, P.J., Brubaker, L.B., Coats, L.L., Cwynar, L.C., Duvall, M.L., Dyke, A.S., Edwards, M.E., Eisner, W.R., Gajewski, K., Geirsdottir, A., Hu, F.S., Jennings, A.E., Kaplan, M.R., Kerwin, M.W., Lohzkin, A.V., MacDonald, G.M., Miller, G.H., Mock, C.J., Oswald, W.W., Otto-Bliesner, B.L., Porinchu, D.F., Ruhland, K., Smol, J.P., Steig, E.J., and Wolfe, B.B., 2004. (Click on link to open 1 MB PDF) Holocene thermal maximum in the western Arctic (0-180 degrees W): Quaternary Science Reviews, v. 23, p. 529-560.
Muhs, D.R., Ager, T.A., Been, J., Bradbury, J.P., and Dean, W.E. 2003. (Click on link to open 1 MB PDF) A late Quaternary record of eolian silt deposition in a maar lake, St. Michael Island, western Alaska: Quaternary Research, v. 60, p. 110-122.
Muhs, D., Ager, T.A., Been, J., Rosenbaum, J.G., and Reynolds, R.L., 2000. An evaluation of methods for identifying and interpreting buried soils in late Quaternary loess in Alaska: in U.S. Geological Survey Professional Paper 1615, p. 127-146.
Muhs, D., Ager, T.A., and Beget, J.E., 2001. (Click on link to open 1.1 MB PDF) Vegetation and paleoclimate of the last interglacial period, central Alaska: Quaternary Science Reviews, v. 20, p. 41-61.
Muhs, D., Ager, T.A., Bettis, E.A. III, McGeehin, J., Been, J.M., Beget, J.E., Pavich, M.J., Stafford, T.W., Jr., and Stevens, D.S.P., 2003. (Click on link to open 2.2 MB PDF) Stratigraphy and paleoclimatic significance of late Quaternary loess-paleosol sequences of the last interglacial-glacial cycle in central Alaska: Quaternary Science Reviews, v. 22, p. 1947-1986.
Sattler, R., Dixon, E.J., Heaton, T.H., and Ager, T.A., 1999. Late Pleistocene sediments and paleoenvironments in a southeast Alaska cave [abs.]: Program and Abstracts, 26th Annual Meeting, Alaska Anthropological Association, Fairbanks, Alaska, March 31-April 3, 1999.
White, J.M., Ager, T.A., Adam, D.P, Leopold, E.B., Liu, G., Jette, H., and Schweger, C.E., 1999. Neogene and Quaternary quantitative palynostratigraphy and paleoclimatology from sections in Yukon and adjacent Northwest Territories and Alaska: Geological Survey of Canada Bulletin 543, 30 p.
U.S. Department of the Interior | U.S. Geological Survey
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