Hydrogeology of Caves in the Sierra de El Abra Region

The hydrogeology of the El Abra region has a very dynamic history. Surface and underground rivers have broadly changed their paths throughout time. A simple model for estimating the age of caves by assessing rates of uplift/erosion is proposed. It is likely that not a single one of the river caves that currently house Astyanax populations had been formed when the original wave of colonization occurred 4.6-1.12 mya (million years ago). Colonization had to occur at higher-level caves. As the zone uplifted and eroded, deeper-level cave passages formed. Capture and sequestration of the underground streams allowed the ancestral population(s) to migrate to their current localities.