Late Pleistocene to Mid-Holocene climate variability in Ireland : evidence from Ostracod geochemistry
Year: 2010
Type: dissertation
Abstract: Late Pleistocene to Mid-Holocene Climate Variability in Ireland: Evidence from Ostracod GeochemistryStable isotope values of ostracod calcite provide a record of variation in δ 18 O(H 2 O) values and water temperature from the late glacial to mid-Holocene in Western Ireland.Lough Monreagh, located in County Clare, Western Ireland, contains marl sediment that includes pristine ostracod calcite whose δ 18 O and δ 13 C values were evaluated.These values were used relative to modern ecological requirements to derive a paleoenvironmental record for Lough Monreagh that includes water temperature, eutrophication, water depth, as well as terrestrial vegetation and weathering within the lake's watershed.δ 13 C values of ostracod calcite presented herein suggest a significant increase in terrestrial vegetation beginning during the Allerød (13,600 cal year B.P.) and extending through to the mid-Holocene (6,997 cal year B.P.).Marl and ostracod δ 18 O values record variability in temperature and precipitation δ 18 O(H 2 O) values that are in turn forced by variation in atmospheric and oceanic circulation.Water temperatures presented herein were calculated from δ 18 O values of ostracod calcite and marl, constrained by temperature preference and tolerance ranges of ostracod species, yielding the highest resolution temperature record covering this period to date.Over 4,700 ostracods representing all three freshwater superfamilies were counted and identified to evaluate the trophic stage of the lake.The lake was characterized as a clear-, cold-water (~8ºC iii summer water temperature), low-nutrient environment during the Allerød, then freezes abruptly during the Younger Dryas as evidenced by black clay deposits aged 12,800 to 11,300 cal yr B.P. Following the Younger Dryas, transitional warming and increasing terrestrial vegetation are evidenced by decreasing δ 13 C values of ostracoda and faunal transition to phytophyllic species.Summer water temperatures warm to >16ºC, with ostracod species suggesting a shallow-water, fen-and macrophyte-rich environment with abundant plant life in and around the lake by ~8,000 cal yr B.P.
Author: Shawn McKenzie
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Climate action
Open Access status: green
Funder: University of Pittsburgh
OpenAlex ID: W1546319945