Subterranean Fishes of the World

5338

2021

Geophysical Research Letters

1-9

48, e2020GL092091

Abstract The Yucatan Peninsula is composed of highly porous, karstified limestone, resulting in scarce surface water bodies. Portions of the peninsula have fracture zones throughout the subsurface. We present water level measurements from four inland locations, previously assumed to be hydrologically isolated from the regional aquifer, or at most leaky with a weak connection. At all locations, tidal oscillations were detected, and verified by performing significance testing. We argue that the presence of cave passages and fracture zones in the limestone allows for much further inland penetration of the tidal signal, compared to classical Richards equation based predictions. The analysis of lacustrine sedimentbased paleoclimate records from across the Yucatan Peninsula assumes low to no interchange between the water bodies and the aquifer, and this assumption may need to be revisited based on our results. Increased connectivity of aquifer to inland water bodies also suggests greater flood risk from sea level rise. Plain Language Summary The Yucatan Peninsula is made up of limestone which is an extremely porous rock that reduces water capture on the surface, and rather retains it within the subsurface in an extensive aquifer. As a result, few lakes are found throughout the peninsula and most water is accessible through sinkholes, locally known as cenotes. There are several fracture zones where the limestone has been preferentially dissolved that run throughout the peninsula in various directions, which create conduits of preferential flow. Through a series of water level measurements at various natural inland bodies of water (lakes and cenotes) we report on tidal oscillations measured to have a much larger amplitude than calculations predict. Many of these locations have previously been assumed to have closed, or very limited, groundwater connections, but the results presented in this article indicate that this is not the case. The tidal signals were subjected to standard statistical tests and shown to be significant. This result has important implications for a range of geosciences throughout the region from paleoclimate reconstructions that use these water bodies, to potential flooding near these water bodies as sea levels continue to rise.

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