Resolving abrupt palaeoenvironmental changes in a lake sediment sequence from Ioannina, northwest Greece

• Main Author: McGuire, Amy
• Format: Text
• Language: unknown
• Published: Apollo - University of Cambridge Repository 2021
• Subjects: Quaternary; palaeoecology; last glacial; abrupt climate change; palynology; tephrochronology; lake sediments; Ioannina; NW Greece; North Atlantic
• Online Access: https://dx.doi.org/10.17863/cam.66044; https://www.repository.cam.ac.uk/handle/1810/318927

Palaeoenvironmental sequences from the Mediterranean have, for many years, been a cornerstone of our understanding of ecological responses to Quaternary climate change. Lake Ioannina (NW Greece) is one such archive, with a vegetation record which spans multiple glacial-interglacial cycles. This PhD builds upon earlier work at Ioannina, seeking to characterise last glacial millennial-scale palaeoenvironmental change at the site through study of core I-08. Detailed visible and ‘crypto-’ tephra analysis identifies deposits associated with explosive volcanism at Italian volcanic sources, including Campi Flegrei, Pantelleria, and the Aeolian islands for the first time at Ioannina. Two visible tephra layers, the Campanian Ignimbrite (CI/Y-5; ca. 39.8 ka BP) and Pantelleria Green Tuff (PGT/Y-6; ca. 45.7 ka BP) are identified, as well as the Holocene Vallone del Gabellotto cryptotephra marker (E-1; ca. 8.3 ka BP). Evidence for repeated remobilisation and redeposition of CI/Y-5 tephra material is outlined, and the potential mechanisms and impacts of sediment reworking in lake environments are examined. Bayesian modelling, which incorporates the new tephra ages with earlier radiocarbon ages, extends the I-08 core chronology back to ca. 46 ka BP. New, centennial-scale palaeoenvironmental analysis of the I-08 core is presented, spanning the section of core ca. 46 to 38 ka BP, chronologically well-constrained by the two visible tephra deposits. The data comprise pollen, loss-on-ignition, XRF, and particle size analyses. Pollen data suggest multiple expansions and contractions of temperate woodland during this window, however these changes are not always in phase with changes in sedimentology, suggesting a complex local response to millennial-scale climatic variability associated with North Atlantic D-O cyclicity. In contrast, ca. 40 ka BP both sediment and vegetation changes occur synchronously and can be attributed to abrupt cooling and drying at the Ioannina site associated with Heinrich stadial 4. Tephra isochrons, particularly the ca. 39.8 ka BP Campanian Ignimbrite eruption, facilitate direct correlation of the I-08 palaeoenvironmental record to other high resolution last glacial pollen sequences in the Mediterranean such as Lago Grande di Monticchio (Italy) and Tenaghi Philippon (Greece) with less ambiguity than work reliant on traditional geochronological approaches. : This work was funded by the Department of Geography, University of Cambridge.