Speleothems are key archives of palaeoclimatic information, chronologies for which can be precisely derived by Uranium Series methods. This investigation uses stable isotopes, trace elements and petrography in speleothems from the Eastern Mediterranean to reconstruct palaeoclimatic parameters in the area over the last -100 ka. Speleothems were collected along a transect from North-East to South West Turkey to Greece. Five stalagmite samples were selected for detailed geochemical analysis which was anchored by - 30 Uranium-Series dates. Most notably, oxygen isotope ratios in a stalagmite from Karaca cave, northeast Turkey exhibit similar temporal patterns to the Greenland ice core oxygen isotope records and to Chinese speleothem records of East Asian Monsoon (EAM) fluctuations over the period 77 ka to 6 ka. Winter rainfall maxima in north-east Turkey coincide with periods of intensified EAM. The isotope curve is interpreted as an insolation (precession) forced record of rainfall seasonality on glacialinterglacial timescales, with periods of high Northern Hemisphere insolation giving rise to cool wet winters and hot dry summers. Millennial-scale variability is caused by shorter-term changes in seasonality of precipitation and/or switching of moisture source areas in response to the stadial-interstadial climatic oscillations originating in the North Atlantic Basin and widely recorded in both marine and terrestrial climate records. Oxygen isotope rations in a 21 ka to7 ka stalagmite from southern Greece are interpreted similarly to Karaca. Shifts in S13C values in the record are related to soil biogenic activity. An isotopic event at 21 ka is interpreted as a short term increase in winter rainfall in response to increased seasonality due to increased insolation (precession). In south-west Turkey the 110 ka to 68 ka KE- I record is characterised by several large shifts in &180 and 613C corresponding to MIS 4,5a, 5b and 5c. These variations are again related to changes in seasonality of rainfall and are correlative with the Hulu speleothem record and Greenland ice core oxygen isotope records.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:520432 |
| Date | January 2009 |
| Creators | Mason, Jennifer |
| Publisher | University of East Anglia |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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