See more from this Division: Gulf Coast Association of Geological Societies
See more from this Session: Environmental Geology I and Hydrology
Abstract:
To achieve these objectives, we analyzed geochemical and isotopic compositions along two transects from the outcrop towards the coast. We observed a progressive decrease in the molar ratios of sulfate/chloride, sodium/chloride, potassium/chloride, and bicarbonate/chloride and increase in boron concentrations and chloride/bromide ratios towards the coast. These changes indicate chemical processes including dissolution and precipitation of carbonates, ion exchanges, evaporite dissolution, and local, chemical changes due to minor saltwater intrusion. Saltwater intrusion is not evident in any of the groundwater analyzed except for a limited number of wells located in close proximity to the coast.
Modern groundwater recharge into the deeper parts of the aquifers is probably insignificant as indicated by the near absence of tritium and low carbon-14 (percent modern carbon). Percent modern carbon values progressively decrease from the outcrop to the downdip areas towards the coast. Several pairs of wells were used to estimate groundwater flow velocities using carbon-14 data. Groundwater flow velocities calculated using geochemical models are in reasonable agreement with hydraulically derived groundwater flow velocities. This suggests that groundwater in the coastal parts of the aquifer may be up to about 30,000 years old.
See more from this Division: Gulf Coast Association of Geological Societies
See more from this Session: Environmental Geology I and Hydrology