Hydrography of the brines in the Bannock and Tyro anoxic basins (eastern Mediterranean)

Abstract

The anoxic brine-filled Tyro and Bannock Basins (eastern Mediterranean) show strong temperature and conductivity gradients at the interface between normal water and anoxic brine (at ∼ 3276 m in the Bannock Basin, at 3328 m in the Tyro Basin), with temperature and conductivity increasing toward the bottom. Temperature reaches values of 15.14°C in the Bannock area and of 14.13°C in the Tyro Basin, and conductivity at the bottom is respectively 177.44 and 191.26 mS cm −1. In the deepest basin of the Bannock area (named Libeccio) a sequence of nearly homogeneous layers, separated by sharp interfaces, is present below the seawater-brine interface. Near the bottom a homogeneous 244-m-thick layer has been observed. The hydrological structure of brines in Tyro Basin shows no evidence of thermal layering. The present geothermal flux seems to be sufficient to create and maintain the temperature structure observed in the brines. A minimum of 4500 years would be needed to raise the Bannock brine body to its current temperature. Only a minimum of 150 years is needed to bring the Tyro brine to its current condition.