GEOCHEMISTRY AND PETROGRAPHY OF SPELEOTHEMS FROM TURKEY AND IRAN: PALAEOCLIMATE AND DIAGENESIS

Abstract Speleothems contain key archives of palaeoclimatic information, which can be interpreted through multiple geochemical and petrographic proxies, and precisely dated by Uranium Series dating. As U/Th dating is only viable for samples up to approximately 700 kyr of age, U/Pb dating must be used to date older samples. In this study, U/Pb methods were used to date an aragonite layer in a speleothem from Iran, following the use of autoradiography to select samples with appropriately high uranium. Aragonite is metastable at earth surface conditions, and is therefore prone to recrystallisation as calcite if it comes into contact with a fluid that is undersaturated with respect to aragonite. This process affected two speleothems from Dim Cave, SW Turkey, and one speleothem from Torang Cave, Iran. The older Dim Cave stalagmite, which precipitated during MIS 5e, was not identified as a recrystallised stalagmite at first, as the mineralogy of the growth axis appeared to show a change in primary mineral rather than recrystallisation. Despite the fact that recrystallisation had occurred, it was possible to create an age model, as the system had not opened to a great degree. The persistence of an aragonite layer in this speleothem, as well as several other geochemical proxies, indicates that an arid phase occurred during early MIS 5e in SW Turkey. The second recrystallised speleothem from Dim Cave provides useful insights into the geochemical and petrographic character of recrystallised speleothems. The recrystallised speleothem from Torang Cave produced a record of climatic instability in southern Iran during MIS period 9- 7, although the age model was not precise enough to draw precise conclusions. A small aragonitic Holocene growth from Dim Cave grew during a time which corresponds to an early Holocene pluvial period that affected the entire eastern Mediterranean Basin, coinciding with the deposition of Sapropel 1. *[N.B.: Additional data was attached to this thesis at the time of its submission. Please refer to the author for further details.]

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2013

Author dc:creator

• Wickens, Leretta

Language dc:language

en