U-Th and radiocarbon dating of calcite speleothems from gypsum caves (Emilia Romagna, North Italy)
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Publication Date
4-15-2019
Publication Title
Quaternary Geochronology
Volume Number
52
Abstract
High-resolution U-Th and 14C dating of two calcite flowstones (RTf: Last Interglacial; RTy: Late Holocene) from the Re Tiberio – Monte Tondo karst system (North Italy) is presented to investigate the palaeoclimate potential of speleothems from gypsum caves. To date, there is a lack of information regarding the dating potential of calcite speleothems that have grown in such gypsum karst environment (e.g. no pseudokarst). High-resolution U-Th dating, aimed at establishing if these speleothems can provide robust radiometric age sequences, is first presented. Although both samples show promise for reliable radiometric dating, about 20% of the ages in the RTf dataset were excluded from the age-model as outliers. These outliers are best explained by post-depositional diagenetic processes affecting the U-Th system rather than anything specific to gypsum karst environment conditions. In contrast, outliers were not detected in the RTy sample, but U-Th analysis was not able to constrain its relatively young age (∼600 years before present, B.P.). Consequently, radiocarbon measurements were undertaken, and combined with the U-Th ages to build an age-model. The latter allowed the estimation of “dead carbon fraction” (DCF), which yields a constant value through time, and a magnitude comparable to other sites where climate is similar to Monte Tondo. Soils were considered the main source of carbon, because bedrock dissolution acted predominantly under open-system conditions, and soil organic matter (SOM) turnover rate appears above average compared to sites studied elsewhere.
Keywords
Speleothems, Uranium-thorium dating, Radiocarbon dating, Karst, Paleoclimatology
Document Type
Article
Digital Object Identifier (DOI)
https://doi.org/10.1016/j.quageo.2019.04.002
Language
English
Recommended Citation
Columbu, Andrea; Drysdale, Russell; Hellstrom, John; Woodhead, Jon; Cheng, Hai; Hua, Quan; Zhao, Jian-xin; Montagna, Paolo; Pons-Branchu, Edwige; and Edwards, R. Lawrence, "U-Th and radiocarbon dating of calcite speleothems from gypsum caves (Emilia Romagna, North Italy)" (2019). KIP Articles. 8421.
https://digitalcommons.usf.edu/kip_articles/8421
