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http://hdl.handle.net/11375/19651
Title: | ESR Isochron Dating of Speleothems |
Authors: | Karakostanoglou, Iakovos |
Advisor: | Schwarcz, Henry P. |
Department: | Geology |
Publication Date: | Nov-1982 |
Abstract: | <p>Calcium carbonate precipitated in caves (speleothem) may contain more than 1 ppm of U but is devoid of Th or K. The major part of its natural radiation dosage (NRD) may have arisen internally from U and its short-lived daughters. By analysing adjacent, approximately coeval samples with varying U content, it is possible to construct an isochron of NRD versus U content which, when extrapolated to zero, gives the external NRD component. The slope of the isochron is a function of the age of the samples, taking into account appropriate corrections for disequilibrium between U-series daughter isotopes, and alpha-particle ESR efficiency ("a"-factor). Using speleothems which have been dated by the 230Th/234U method, the above procedure has been reversed to determine the average "a"-factor of the samples, and to establish that its values lie around 0.1.</p> <p>Several discrete and reproducible ESR peaks of approximately constant g-value have been observed in speleothem calcites. The main peak (S 1A) with g=2.0008(±2), fades at approximately 220°C and corresponds to the principal TL peak, used for dating so far. Other weaker peaks of various g-values and fading temperatures are also radiation-sensitive. Several other peaks are present which are associated with Mn2+. Low-temperature annealing has a mild effect on the main peak, probably due to retrapping. This peak varies greatly with grain size, decreasing by more than half for particles less than 100 μm.</p> |
Description: | Title: ESR Isochron Dating of Speleothems, Author: Iakovos Karakostanoglou, Location: Thode |
URI: | http://hdl.handle.net/11375/19651 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Karakostanoglou_Ikovos_1982_11_master.pdf | Title: ESR Isochron Dating of Speleothems, Author: Iakovos Karakostanoglou, Location: Thode | 23.6 MB | Adobe PDF | View/Open |
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