Geochemical and petrographic insights from speleothems: Records of Holocene Eastern Mediterranean climate

Peckover, Emily (2017) Geochemical and petrographic insights from speleothems: Records of Holocene Eastern Mediterranean climate. Doctoral thesis, University of East Anglia.

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In this thesis, new Holocene palaeoclimate information from speleothems is presented from three regions (central Peloponnese Greece, south west Turkey and the eastern forelands of the Zagros Mountains, Iran) where the spatial distribution of Holocene climate records is low. This study uses a multi-proxy approach with particular emphasis on petrography and stable isotope analysis. Holocene growth of stalagmite KTR-2 (11,900 yr BP to 6700 yr BP) from Limnon Cave in the central Peloponnese is broadly coincident with the formation of Sapropel 1. The early Holocene was generally wetter than at present. A record of the 8.2 kyr event was obtained from KTR-2 using high resolution trace element ICP-MS and micromilled stable isotope samples. Arid conditions are implied by δ18O and trace elements, with aridity probably beginning ~9000 yr BP. δ13C data suggests precipitation may have been strongly seasonal during the 8.2 kyr event.
Distinct grey coloured layers in HY-8, a stalagmite from Sirtlanini Cave, SW Turkey, represent fire events occurring above the cave; there is however, no suggestion that the fires occurred during periods of relatively enhanced aridity. The palaeoclimate record spans ~5600 yr BP to the present day, but does not indicate any significant long term reduction in precipitation. The HY-8 δ18O record suggests the 4.2 kyr anomaly was a two-step aridity event occurring between 4290 and 3850 yr BP. A distinct pluvial event from 4890-4290 yr BP is also recorded by δ18O, as is evidence for the Little Ice Age (630-280 yr BP).
The Holocene section of stalagmite KT-3, from the eastern forelands of the Zagros Mountains in Iran, grew from 9400 yr BP to present. The early Holocene until ~7000 yr BP was wetter than the present day. Multiple proxies show falling precipitation amounts from ~7000 yr BP, plateauing from ~3000 yr BP to present. There is very little short term fluctuation in δ18O but the overall trend has a profile similar to the decline of solar insolation in the Holocene, which appears to be responsible for the long term reduction in winter precipitation. In KT-3, the correlation between Ba/Ca and δ13C fluctuations might be a more sensitive indicator of moisture. A significant positive δ13C excursion could be recording the 8.2 kyr event.
Additionally, this thesis presents a specific petrographic study from two different, but discontinuously grown, Turkish stalagmites. These stalagmites grew very differently and within different epochs. Petrography has been used to interpret and relate fabrics to their environment of formation and identified micro-dissolution as a prominent feature of growth. A link between these micro-dissolution events and stratigraphically inverted U-series dates is proposed.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Megan Ruddock
Date Deposited: 19 Dec 2018 13:56
Last Modified: 20 Dec 2021 01:38

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