60,000 year climate and vegetation history of Southeast Alaska
Dissertation (Ph.D.) University of Alaska Fairbanks, 2017 Sedimentological and palynological analyses of lacustrine cores from Baker Island, located in Southeast Alaska's Alexander Archipelago, indicate that glaciers persisted on the island until ~14,500 cal yr. BP. However, the appearance of t...
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ftunivalaska:oai:scholarworks.alaska.edu:11122/7905 2023-05-15T14:18:02+02:00 60,000 year climate and vegetation history of Southeast Alaska Wilcox, Paul S. Fowell, Sarah Bigelow, Nancy Mann, Daniel Dorale, Jeffrey 2017-08 http://hdl.handle.net/11122/7905 en_US eng http://hdl.handle.net/11122/7905 Department of Geosciences Paleoclimatology Alaska Southeast Paleobotany Dissertation phd 2017 ftunivalaska 2023-02-23T21:36:57Z Dissertation (Ph.D.) University of Alaska Fairbanks, 2017 Sedimentological and palynological analyses of lacustrine cores from Baker Island, located in Southeast Alaska's Alexander Archipelago, indicate that glaciers persisted on the island until ~14,500 cal yr. BP. However, the appearance of tree pollen, including Pinus cf. contorta ssp. contorta (shore pine) and Tsuga mertensiana (mountain hemlock) immediately following deglaciation suggests that a forest refugium may have been present on ice-free portions of neighboring islands or the adjacent continental shelf. Sedimentological and palynological analyses indicate a variable climate during the Younger Dryas interval between ~13,000 and ~11,500 cal yr. BP, with a cold and dry onset followed by ameliorating conditions during the latter half of the interval. An eight cm-thick black tephra dated to 13,500 ± 250 cal yr. BP is geochemically distinct from the Mt. Edgecumbe tephra and thus derived from a different volcano. Based on overall thickness, multiple normally graded beds, and grain size, I infer that the black tephra was emplaced by a large strombolian-style paroxysm. Because the dominant wind direction along this coast is from the west, the Addington Volcanic Field on the continental shelf, which would have been subaerially exposed during the eruption, is a potential source. The similarity in timing between this eruption and the Mt. Edgecumbe eruption suggests a shared trigger, possibly a response to unloading as the Cordilleran Ice Sheet retreated. To complement the Baker Island lacustrine record, a speleothem paleoclimate record based on δ¹³C and δ¹⁸O values spanning the interval from ~60,000 yr. BP to ~11,150 yr. BP was recovered from El Capitan Cave on neighboring Prince of Wales Island. More negative δ¹³C values are attributed to predominance of angiosperms in the vegetation above the cave at ~22,000 yr. BP and between ~53,000 and ~46,000 yr. BP while more positive δ¹³C values in speleothem EC-16-5-F indicate the presence of gymnosperms. These data ... Doctoral or Postdoctoral Thesis Archipelago glaciers Ice Sheet Prince of Wales Island Alaska University of Alaska: ScholarWorks@UA Fairbanks Prince of Wales Island ENVELOPE(-99.001,-99.001,72.668,72.668) The Baker ENVELOPE(-54.765,-54.765,49.667,49.667) |
institution |
Open Polar |
collection |
University of Alaska: ScholarWorks@UA |
op_collection_id |
ftunivalaska |
language |
English |
topic |
Paleoclimatology Alaska Southeast Paleobotany |
spellingShingle |
Paleoclimatology Alaska Southeast Paleobotany Wilcox, Paul S. 60,000 year climate and vegetation history of Southeast Alaska |
topic_facet |
Paleoclimatology Alaska Southeast Paleobotany |
description |
Dissertation (Ph.D.) University of Alaska Fairbanks, 2017 Sedimentological and palynological analyses of lacustrine cores from Baker Island, located in Southeast Alaska's Alexander Archipelago, indicate that glaciers persisted on the island until ~14,500 cal yr. BP. However, the appearance of tree pollen, including Pinus cf. contorta ssp. contorta (shore pine) and Tsuga mertensiana (mountain hemlock) immediately following deglaciation suggests that a forest refugium may have been present on ice-free portions of neighboring islands or the adjacent continental shelf. Sedimentological and palynological analyses indicate a variable climate during the Younger Dryas interval between ~13,000 and ~11,500 cal yr. BP, with a cold and dry onset followed by ameliorating conditions during the latter half of the interval. An eight cm-thick black tephra dated to 13,500 ± 250 cal yr. BP is geochemically distinct from the Mt. Edgecumbe tephra and thus derived from a different volcano. Based on overall thickness, multiple normally graded beds, and grain size, I infer that the black tephra was emplaced by a large strombolian-style paroxysm. Because the dominant wind direction along this coast is from the west, the Addington Volcanic Field on the continental shelf, which would have been subaerially exposed during the eruption, is a potential source. The similarity in timing between this eruption and the Mt. Edgecumbe eruption suggests a shared trigger, possibly a response to unloading as the Cordilleran Ice Sheet retreated. To complement the Baker Island lacustrine record, a speleothem paleoclimate record based on δ¹³C and δ¹⁸O values spanning the interval from ~60,000 yr. BP to ~11,150 yr. BP was recovered from El Capitan Cave on neighboring Prince of Wales Island. More negative δ¹³C values are attributed to predominance of angiosperms in the vegetation above the cave at ~22,000 yr. BP and between ~53,000 and ~46,000 yr. BP while more positive δ¹³C values in speleothem EC-16-5-F indicate the presence of gymnosperms. These data ... |
author2 |
Fowell, Sarah Bigelow, Nancy Mann, Daniel Dorale, Jeffrey |
format |
Doctoral or Postdoctoral Thesis |
author |
Wilcox, Paul S. |
author_facet |
Wilcox, Paul S. |
author_sort |
Wilcox, Paul S. |
title |
60,000 year climate and vegetation history of Southeast Alaska |
title_short |
60,000 year climate and vegetation history of Southeast Alaska |
title_full |
60,000 year climate and vegetation history of Southeast Alaska |
title_fullStr |
60,000 year climate and vegetation history of Southeast Alaska |
title_full_unstemmed |
60,000 year climate and vegetation history of Southeast Alaska |
title_sort |
60,000 year climate and vegetation history of southeast alaska |
publishDate |
2017 |
url |
http://hdl.handle.net/11122/7905 |
long_lat |
ENVELOPE(-99.001,-99.001,72.668,72.668) ENVELOPE(-54.765,-54.765,49.667,49.667) |
geographic |
Fairbanks Prince of Wales Island The Baker |
geographic_facet |
Fairbanks Prince of Wales Island The Baker |
genre |
Archipelago glaciers Ice Sheet Prince of Wales Island Alaska |
genre_facet |
Archipelago glaciers Ice Sheet Prince of Wales Island Alaska |
op_relation |
http://hdl.handle.net/11122/7905 Department of Geosciences |
_version_ |
1766289796757454848 |