Map of glacial limits and possible refugia in the southern Alexander Archipelago, Alaska, during the late Wisconsin glaciation

Metadata Updated: November 12, 2020

During the late Wisconsin glaciation (circa 26,000-13,000 carbon-14 yr BP) the Cordilleran glacier complex formed vast ice fields and large glaciers along the crest of the Coast Mountains. As these glaciers flowed west to the Pacific Ocean, they were joined by local glaciers originating on the higher reaches of the Alexander Archipelago (Mann and Hamiltion, 1995). This extensive volume of ice was channeled into deep troughs (present-day fiords) that formed major outlet glaciers, such as the glaciers that occupied Chatham Strait and Dixon Entrance. In several places along the coast, deep glacially scoured submarine troughs indicate that glaciers reached to the edge of the continental shelf. For instance, the glacier that extended into the Dixon Entrance trough is known to have extended to the edge of the continental shelf. Its retreat began sometime after 16,000-15,000 carbon-14 yr BP (Barrie and Conway, 1999). The exact extent of late Wisconsin cordilleran ice in southeastern Alaska is poorly known. Small-scale maps and reports of the region commonly show or imply ice extending west to the edge of the continental shelf (Capps, 1931; Coulter and others, 1965; Flint, 1971; Pewe, 1975; Denton and Hughes, 1981; and Prest, 1984). These maps relied heavily on earlier work, much of it of a reconnaissance nature. The map shows our interpretation of the limit of the Cordilleran ice sheet, which is more restricted than previous estimates, and possible refugium (an area that escaped the extensive glaciation of the late Wisconsin and so provided a suitable habitat for relict species) in the southern Alexander Archipelago during the late Wisconsin glaciation. In addition to the analysis of the bathymetric map, the limits of the Cordilleran ice sheet and possible refugia were also identified by analyses of aerial photographs, USGS topographic maps (1:63,360 and 1:250,000 scales), NOAA bathymetric charts (1:20,000 and 1:40,000 scales), previous literature, and reconnaissance fieldwork throughout the region. Ice-free areas that may have served as refugia include (1) high mountain nunataks (too small to show at map scale), (2) unglaciated ocean-facing slopes and forelands (Dahl, 1946), (3) the outer islands of the Alexander Archipelago (Worley, 1980), and (4) parts of the inner continental shelf exposed by the lowering of sea level during the late Wisconsin by an estimated 125 m (Bard and others, 1990).

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License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Dates

Metadata Date February 5, 2016
Metadata Created Date November 12, 2020
Metadata Updated Date November 12, 2020
Reference Date(s) January 1, 2003 (publication)
Frequency Of Update notPlanned

Graphic Preview

Reduced-size image of the entire map sheet, 250x157 pixels, 13k bytes.

Additional Metadata

Resource Type Dataset
Metadata Date February 5, 2016
Metadata Created Date November 12, 2020
Metadata Updated Date November 12, 2020
Reference Date(s) January 1, 2003 (publication)
Responsible Party U.S. Geological Survey (Point of Contact)
Contact Email
Guid
Access Constraints Use Constraints: none. Acknowledgment of the U.S. Geological Survey would be appreciated in products derived from these data., Access Constraints: none
Bbox East Long -131.1200724
Bbox North Lat 57.29756559
Bbox South Lat 54.21530596
Bbox West Long -136.27626612
Coupled Resource
Frequency Of Update notPlanned
Graphic Preview Description Reduced-size image of the entire map sheet, 250x157 pixels, 13k bytes.
Graphic Preview File http://pubs.usgs.gov/mf/2003/mf-2424/MF-2424_250_pixel_wide.gif
Graphic Preview Type GIF
Harvest Object Id 227f30c0-1fac-4806-a175-68f46f774d70
Harvest Source Id 00f54869-3a43-480d-a67c-0ba115f5d739
Harvest Source Title USGS-Harvest
Licence Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials.
Metadata Language
Metadata Type geospatial
Progress completed
Spatial Data Service Type
Spatial Reference System
Spatial Harvester True

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