Quaternary Sea-Level and Climate Signatures in Phreatic Coastal Caves
Underwater (phreatic) caves are a ubiquitous landform on coastal karst terrain, but the marine geological processes operating in these systems are largely unknown. This dissertation redresses the problem by asking if Bermudian phreatic cave sediments archive sea-level and climate information? An imp...
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ftcanadathes:oai:collectionscanada.gc.ca:NSHD.ca#10222/13123 2023-05-15T16:41:32+02:00 Quaternary Sea-Level and Climate Signatures in Phreatic Coastal Caves van Hengstum, Peter 2010-12-03T14:29:52Z http://hdl.handle.net/10222/13123 en eng http://hdl.handle.net/10222/13123 Caves sea level foraminifera anchialine submarine North Atlantic Oscillation Quaternary 2010 ftcanadathes 2013-11-23T23:00:20Z Underwater (phreatic) caves are a ubiquitous landform on coastal karst terrain, but the marine geological processes operating in these systems are largely unknown. This dissertation redresses the problem by asking if Bermudian phreatic cave sediments archive sea-level and climate information? An important premise is that coastal cave environments are not identical. They can be categorized based on whether they are terrestrially-influenced (anchialine), completely flooded by saline groundwater (submarine), positioned at sea level (littoral) or in the vadose zone (vadose). For the first time the boundary between modern anchialine and submarine cave environments has been distinguished in Green Bay Cave using a multi-proxy approach (benthic foraminifera, sedimentary organic matter content and carbon isotopic composition - ?13Corg, and grain-size analysis). Twelve push cores were extracted from Green Bay Cave and dated with twenty 14C dates, recovering the first underwater cave succession spanning the Holocene (13 ka to present). Green Bay Cave transitioned through all major cave environments during Holocene sea-level rise (vadose, littoral, anchialine, and submarine), providing a sedimentary model for global cave successions. These relationships provide a novel means to solve Quaternary sea-level and climate problems. For sea level, two examples indicate that the littoral cave can be used as a sea-level indicator, distinguished stratigraphically by microfossil or sedimentary proxies. First, the elevation and timing of when Green Bay Cave was a littoral environment indicates Bermuda experienced an abrupt ~6.4 m sea-level rise at 7.7 ka, coinciding with final collapse of the Labrador sector of the Laurentide Ice Sheet. Second, microfossils preserved in elevated caves at +21 m above modern sea level and dated to marine isotope stage 11 (U-series, amino acid racemization) are consistent with modern Bermudian caves and co-stratigraphic sea level. For climate problems, annual temperature monitoring in Walsingham Cave indicates that cave water is thermally comparable to regional oceanographic conditions in the Sargasso Sea. Three sediment cores dated with sixteen radiocarbon dates indicate that Bermuda’s coldest and stormiest conditions of the last 3.2 ka occurred during the Little Ice Age (proxies: ?18Oc, grain size, bulk organic matter). Other/Unknown Material Ice Sheet North Atlantic North Atlantic oscillation Theses Canada/Thèses Canada (Library and Archives Canada) Green Bay ENVELOPE(-36.014,-36.014,-54.870,-54.870) |
institution |
Open Polar |
collection |
Theses Canada/Thèses Canada (Library and Archives Canada) |
op_collection_id |
ftcanadathes |
language |
English |
topic |
Caves sea level foraminifera anchialine submarine North Atlantic Oscillation Quaternary |
spellingShingle |
Caves sea level foraminifera anchialine submarine North Atlantic Oscillation Quaternary van Hengstum, Peter Quaternary Sea-Level and Climate Signatures in Phreatic Coastal Caves |
topic_facet |
Caves sea level foraminifera anchialine submarine North Atlantic Oscillation Quaternary |
description |
Underwater (phreatic) caves are a ubiquitous landform on coastal karst terrain, but the marine geological processes operating in these systems are largely unknown. This dissertation redresses the problem by asking if Bermudian phreatic cave sediments archive sea-level and climate information? An important premise is that coastal cave environments are not identical. They can be categorized based on whether they are terrestrially-influenced (anchialine), completely flooded by saline groundwater (submarine), positioned at sea level (littoral) or in the vadose zone (vadose). For the first time the boundary between modern anchialine and submarine cave environments has been distinguished in Green Bay Cave using a multi-proxy approach (benthic foraminifera, sedimentary organic matter content and carbon isotopic composition - ?13Corg, and grain-size analysis). Twelve push cores were extracted from Green Bay Cave and dated with twenty 14C dates, recovering the first underwater cave succession spanning the Holocene (13 ka to present). Green Bay Cave transitioned through all major cave environments during Holocene sea-level rise (vadose, littoral, anchialine, and submarine), providing a sedimentary model for global cave successions. These relationships provide a novel means to solve Quaternary sea-level and climate problems. For sea level, two examples indicate that the littoral cave can be used as a sea-level indicator, distinguished stratigraphically by microfossil or sedimentary proxies. First, the elevation and timing of when Green Bay Cave was a littoral environment indicates Bermuda experienced an abrupt ~6.4 m sea-level rise at 7.7 ka, coinciding with final collapse of the Labrador sector of the Laurentide Ice Sheet. Second, microfossils preserved in elevated caves at +21 m above modern sea level and dated to marine isotope stage 11 (U-series, amino acid racemization) are consistent with modern Bermudian caves and co-stratigraphic sea level. For climate problems, annual temperature monitoring in Walsingham Cave indicates that cave water is thermally comparable to regional oceanographic conditions in the Sargasso Sea. Three sediment cores dated with sixteen radiocarbon dates indicate that Bermuda’s coldest and stormiest conditions of the last 3.2 ka occurred during the Little Ice Age (proxies: ?18Oc, grain size, bulk organic matter). |
author |
van Hengstum, Peter |
author_facet |
van Hengstum, Peter |
author_sort |
van Hengstum, Peter |
title |
Quaternary Sea-Level and Climate Signatures in Phreatic Coastal Caves |
title_short |
Quaternary Sea-Level and Climate Signatures in Phreatic Coastal Caves |
title_full |
Quaternary Sea-Level and Climate Signatures in Phreatic Coastal Caves |
title_fullStr |
Quaternary Sea-Level and Climate Signatures in Phreatic Coastal Caves |
title_full_unstemmed |
Quaternary Sea-Level and Climate Signatures in Phreatic Coastal Caves |
title_sort |
quaternary sea-level and climate signatures in phreatic coastal caves |
publishDate |
2010 |
url |
http://hdl.handle.net/10222/13123 |
long_lat |
ENVELOPE(-36.014,-36.014,-54.870,-54.870) |
geographic |
Green Bay |
geographic_facet |
Green Bay |
genre |
Ice Sheet North Atlantic North Atlantic oscillation |
genre_facet |
Ice Sheet North Atlantic North Atlantic oscillation |
op_relation |
http://hdl.handle.net/10222/13123 |
_version_ |
1766031982759772160 |