Underwater cave systems in carbonate rocks as semi-proxy indicators of paleo-sea levels

Abstract

Underwater caves may yield valuable information on changes in sea level, as they can track the position of an ancient sea level to a variable degree of accuracy. Limestone caves, in particular, develop different morphologies as a function of oscillating sea levels. In carbonate settings, when true coastal caves including precise indicators of sea-level such as notches or beach deposits are lacking (which hold true as paleo-sea levels indicators for any type of lithology), ancient stillstand levels are approximated: 1) by determining a former groundwater level for continental karst processes (which subsequently experiences submersion) provided they acted sufficiently close to the coast; 2) by determining a mixing zone of different solutions leading to hyperkarst processes. The wide range of different typologies developed in the limestone coastal belt of the Tyrrhenian Sea (Italy), yields case-histories which can be taken as representative of the relationships between relative changes in sea levels and the evolution of karst systems. In particular, the occurrence of features related to hyperkarst processes can be reliable "semi-proxy" indicators of paleo-sea levels in absence of more precise markers.