Holocene Glacial and Tree-Line Variations in the White River Valley and Skolai Pass, Alaska and Yukon Territory

Dados Bibliográficos

ID24085404
AutoresGeorge H Denton (University of Maine), Wibjörn Karlén (University of Maine)
Ano1977
Volume7
Fascículo1
Páginas63-111
Data de publicação1977-01-01
Peer ReviewedSim
Open AccessSim
TipoARTICLE
PeriódicoQuaternary Research (JOURNAL)
Identificadores do periódicoISSN: 0033-5894 • E-ISSN: 1096-0287
EditoraCambridge University Press (CUP) (PUBLISHER)
DOI10.1016/0033-5894(77)90014-x
OpenAlexW1967193306
IdiomaEN
Citações recebidas26
Referências citadas34

Complex glacier and tree-line fluctuations in the White River valley on the northern flank of the St. Elias and Wrangell Mountains in southern Alaska and Yukon Territory are recognized by detailed moraine maps and drift stratigraphy, and are dated by dendrochronology, lichenometry, 14 C ages, and stratigraphic relations of drift to the eastern (1230 14 C yr BP) and northern (1980 14 C yr BP) lobes of the White River Ash. The results show two major intervals of expansion, one concurrent with the well-known and widespread Little Ice Age and the other dated between 2900 and 2100 14 C yr BP, with a culmination about 2600 and 2800 14 C yr BP. Here, the ages of Little Ice Age moraines suggest fluctuating glacier expansion between ad 1500 and the early 20th century. Much of the 20th century has experienced glacier recession, but probably it would be premature to declare the Little Ice Age over. The complex moraine systems of the older expansion interval lie immediately downvalley from Little Ice Age moraines, suggesting that the two expansion intervals represent similar events in the Holocene, and hence that the Little Ice Age is not unique. Another very short-lived advance occurred about 1230 to 1050 14 C yr BP. Spruce immigrated into the valley to a minimum altitude of 3500 ft (1067 m), about 600 ft (183 m) below the current spruce tree line of 4100 ft (1250 m), at least by 8020 14 C yr BP. Subsequent intervals of high tree line were in accord with glacier recession; in fact, several spruce-wood deposits above current tree line occur bedded between Holocene tills. High deposits of fossil wood range up to 76 m above present tree line and are dated at about 5250, 3600 to 3000, and 2100 to 1230 14 C yr BP. St. Elias glacial and tree-line fluctuations, which probably are controlled predominantly by summer temperature and by length of the growing and ablation seasons, correlate closely with a detailed Holocene tree-ring curve from California, suggesting a degree of synchronism of Holocene summer-temperature changes between the two areas. This synchronism is strengthened by comparison with the glacier record from British Columbia and Mt. Rainier. Likewise, broad synchronism of Holocene events exists across the Arctic between the St. Elias Mountains and Swedish Lappland. Finally, two sequences from the Southern Hemisphere show similar records, in so far as dating allows. Hence, we believe that a preliminary case can be made for broad synchronism of Holocene climatic fluctuations in several regions, although further data are needed and several areas, particularly Colorado and Baffin Island, show major differences in the regional pattern.

Climate change · Dendrochronology · Geography · Geomorphology · Glacial period · Glacier · Holocene · Moraine · Physical geography · Tree line · Climate change and permafrost · Cryospheric studies and observations · Geology · Geology and Paleoclimatology Research · Oceanography · Paleontology