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Geochemical characterization of piping-sinkhole lakes as a potential monitoring tool in seismogenic areas

Jacopo Cabassi 1,2, Monia Procesi2, Daniele Cinti2, Franco Tassi1,2,3, Francesco Capecchiacci1,2,3

  • Affiliations: 1CNR-IGG Institute of Geosciences and Earth Resources, Florence, Italy; 2Istituto Nazionale di Geofisica e Vulcanologia, Italy; 3Department of Earth Sciences, University of Florence, Florence, Italy

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 85

  • Programme No: 6.8.11

  • Theme 6 > Session 8

Abstract

Natural sinkholes are depressions in the ground that are commonly associated with karst and/or intense fracturing and faulting. Seismic events favor the uprising of endogenous fluids that may cause rock dissolution and produce piping-sinkholes. The latter may develop in areas of CO2-rich gas emissions and, when an aquifer is present, create small lakes potentially rich in dissolved CO2(CH4) at depth, with characteristics similar to bio-activity volcanic lakes. The results of geochemical surveys carried out in winter and summer at Paterno (LP) and Telese (LT) lakes are here reported. These two lakes are piping-sinkholes located in seismically active areas of central-southern Italy where CO2-rich springs occur. They have maximum depths of 54 and 17 m, respectively, a Ca(Mg)-HCO3 composition and are monomictic, with the establishment of thermal and chemical stratification in summer. During the latter, the CO2 concentrations in the hypolimnion were up to 0.53 and 0.13 mmol/L in LP and LT, respectively, while the δ13C-CO2 values ranged from -8.6 to -7.2 ‰ vs. V-PDB, indicating a contribution of crustal fluids. According to these data, inputs into the lakes of deep fluids, related to seismic activity, may be revealed by changes of the chemical and isotopic features of the lake waters. Therefore, these lakes could be considered promising sites for monitoring seismic activity.