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 pre- sented. 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.

U-Th and radiocarbon dating of calcite speleothems from gypsum caves (Emilia Romagna, North Italy) / Columbu, Andrea; Drysdale, Russell; Hellstrom, John; Woodhead, Jon; Cheng, Hai; Hua, Quan; Zhao, Jian-xin; Montagna, Paolo; Pons-Branchu, Edwige; Lawrence Edwards, R.. - In: QUATERNARY GEOCHRONOLOGY. - ISSN 1871-1014. - 52(2019), pp. 51-62. [10.1016/j.quageo.2019.04.002]

U-Th and radiocarbon dating of calcite speleothems from gypsum caves (Emilia Romagna, North Italy)

Andrea Columbu;
2019

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 pre- sented. 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.
U-Th and radiocarbon dating of calcite speleothems from gypsum caves (Emilia Romagna, North Italy) / Columbu, Andrea; Drysdale, Russell; Hellstrom, John; Woodhead, Jon; Cheng, Hai; Hua, Quan; Zhao, Jian-xin; Montagna, Paolo; Pons-Branchu, Edwige; Lawrence Edwards, R.. - In: QUATERNARY GEOCHRONOLOGY. - ISSN 1871-1014. - 52(2019), pp. 51-62. [10.1016/j.quageo.2019.04.002]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/2901662
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