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PhD defense by Meighan Boyd

Date: 04 December 2015, 13.00 PM - 04 December 2015, 16.00 PM

Titel:  Speleothems in warm climates. Holocene records from the Carribbean and Mediterranean regions
Venue: De Geersalen, Geovetenskapen hus
Handledare:  Prof. Karin Holmgren
Opponent: Prof. Ian Fairchild, School of Geography, Earth and Environmental Sciences, University of Birmingham
Associate Prof. Silvia Frisia, ​School of Environmental and Life Sciences, The University of Newcastle
Associate Prof. Henriette Linge, Department of Earth Science, University of Bergen
Associate Prof. Giovanni Zanchetta, Department of Earth Sciences, Geochemistry and Volcanology, University of Pisa
Reserve member: Prof. Carl-Magnus Mörth, Department of Geological Sciences, Stockholm University
This thesis contributes to increased knowledge on Holocene climate and environmental variability from two complex and sparsely studied areas. Using a speleothem from Gasparee Cave, Trinidad, as a paleoclimate archive, the local expression of the 8.2 ka (thousand years before 1950) climate event and associated patterns of the inter-tropical convergence zone (ITCZ) and rainfall is provided. Subsequent speleothem studies using multi-proxy analysis of stalagmites from Kapsia Cave and Alepotrypa Cave, Greece, provide records of climate, vegetation and human induced changes in the cave environment during parts of the Holocene.
The speleothems from the well-studied Neolithic habitation site, Alepotrypa Cave, have produced a climate and habitation record which covers the period of 6.3-1.0 ka. The cave was inhabited between 8.0-5.2 ka and was closed by a tectonic event, which has preserved the settlement. The stable oxygen record shows the first well-dated and robust expression of the 4.2 ka dry event in the Peloponnese, places the timing of the 3.2 ka dry event within an ongoing dry period, and shows a final dry event at 1.6 ka. The North Atlantic as well as more regional drivers, such as the North Sea Caspian Pattern Index is proposed to, in a complex interplay, govern many of the climate trends and events observed.
Trace element variation after the site is abandoned indicate what is interpreted as two volcanic eruptions, the Minoan eruption of Thera (Santorini) around 3.6 ka and the 2.7 ka eruption of Somma (Vesuvius). Variations in trace elements during the habitation period show clear human influence, indicating an association with specific cave activities. One of the most interesting prospects for continued work on Alepotrypa Cave is this successful marriage of speleothem studies and archeology. A framework of dates which constrain some behavior of people living in the cave is only the beginning, and there is great potential to continue finding new clues in the speleothem data.
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