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.
Bibliographical noteFunding Information:
The carbonate flowstones of Monte Tondo cave system were collected with the help of the cavers of GAM Mezzano and the Federazione Speleologica Regionale dell’Emilia Romagna (FSRER), and especially by Garibaldi Sansavini, Piero Lucci, and Massimo Ercolani. Special thanks to Prof. Jo De Waele and Paolo Forti for their help and constructive comments during the whole “carbonate from gypsum caves” project. The work carried out here was supported by the Australian Research Council (Discovery Project number 160102969 ), and partially supported by U.S. NFS 1702816 Grant to RLE. Finally, thanks to two anonymous reviewers for their useful suggestions and to the Editor for handling the manuscript, as well as to Cesco Sauro for the elucidation about pseudokarst.
© 2019 Elsevier B.V.
- Evaporite karst: Gypsum caves
- U-Th dating