Premium
Laminated tufa sediments formed from overflow karst springs: Controls on their deposition and carbon–oxygen isotope records
Author(s) -
DomínguezVillar David,
VázquezNavarro Juan A.,
Krklec Kristina,
Lojen Sonja,
Fairchild Ian J.
Publication year - 2017
Publication title -
sedimentology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.494
H-Index - 108
eISSN - 1365-3091
pISSN - 0037-0746
DOI - 10.1111/sed.12350
Subject(s) - tufa , karst , geology , carbon dioxide , deposition (geology) , hydrology (agriculture) , groundwater , precipitation , isotopes of carbon , stable isotope ratio , carbonate , geomorphology , total organic carbon , sediment , paleontology , environmental chemistry , ecology , chemistry , physics , geotechnical engineering , organic chemistry , quantum mechanics , meteorology , biology
Abstract Tufa sediments are freshwater carbonates that precipitate in karst regions after degassing of carbon dioxide from groundwater in contact with the atmosphere. When laminated, these carbonates can provide high‐resolution records for the study of climate, hydrological and environmental conditions at the time of their precipitation. The formation of these carbonates directly depends on the hydrological regime, and in karst regions discontinuous discharges are often recorded. This study investigates the record of recent laminated tufa sediments precipitated downstream overflow springs in Trabaque Canyon (central Spain). The hydrological dynamics of the karst system were monitored for over three years and a stable isotope record was obtained from laminated tufa carbonates precipitated from an overflow spring. Additionally, a hydrological model of overflow springs was generated and a tufa δ 18 O record under constrained parameters was simulated. Temperature is the dominant control of the variation in tufa δ 13 C and δ 18 O values within each lamina, although when comparing different laminae, δ 13 C DIC and δ 18 O of river water are also major controls. The positive correlation between tufa δ 13 C values and water temperature is caused by the fractionation occurred by carbon dioxide degassing due to the thermal dependence of carbon dioxide solubility. Additionally, the system recorded a temperature‐independent degassing process caused by the large gradient between groundwater and atmospheric carbon dioxide that is limited to the proximity of the spring. This study cautions on the risk of assuming continuous deposition when studying laminated tufa sediments and highlights the potential of their stable isotope records to provide hydrological information of their aquifers during the past.