COMPOSITION OF INLAND WATERS WITH MARINE-LIKE FAUNA AND INFERENCES FOR A MIOCENE LAKE IN SPAIN

Knowledge of the ionic composition of athalassic (non-marine) waters where marine-like organisms currently live allows to evaluate their ionic- and total dissolved solid (TDS)-tolerance ranges. Together with other ecological data these chemical parameters can be used to interpret hydrological and hydrochemical conditions in ancient lake basins where analogous faunas have been recorded. An example of such a utilization of the biological record is presented for Miocene clastic-dominated lacustrine deposits of the Tertiary Ebro Basin of NE Spain, which contain marine-like fossils. Comparison of the deduced chemical parameters for the Miocene lake waters with the chemical composition of recent groundwaters and saline springs in the same area allows us to infer a similar mode of solute acquisition. This implies that there were important Cl-SO4 saline inflows to the Miocene lakes.