Abstract
Abstract. In the Yucatán Peninsula (YP), southern Mexico, cities and towns are settled on a platform of calcareous sedimentary sequence, where karst processes have formed numerous sinkholes, underground water conduits, and caverns. Anthropogenic activities there threaten the only source of freshwater supply, which is in a regional unconfined aquifer; there are no lakes or rivers on the surface. For the sustainable management of this resource in the YP, mathematical tools are needed in order to model groundwater. To determine the geometry of the aquifer, for example the positions of caves, sinkholes, and underground principal conduits, we modified a software to invert three-dimensional electromagnetic low-induction number (3-D EM-LIN) data for a set of profiles at arbitrary angles. In this study we used the EM-LIN geophysical method to explore the Chac-Mool sinkhole system in the state of Quintana Roo, Mexico. We performed inverse modeling in 3-D using the EM-34 instrument for vertical and horizontal magnetic dipoles. The 3-D inversion process yields models that enable us to correlate the path of the underground principal conduits with the subsurface electrical resistivity. In this work we show that inverse modeling of EM-LIN data can give us information about how close to surface the underground water conduits and the location of the boundary between fresh and salty water are.
Highlights
The main source of fresh water in the Yucatán Peninsula is a regional unconfined karst aquifer that is constituted by sedimentary limestones (Bauer-Gottwein et al, 2011)
Karst aquifers are extremely vulnerable to contaminants because of their high permeability and the peculiar turbulent groundwater flow passing through karst conduits and caves (Worthington, 1999; Parise et al, 2015; Parise, 2019)
In this study we aim to explore a novel approach by using electromagnetic (EM) methods at low-induction numbers (LIN) and applying 3-D geophysical inverse modeling (Pérez-Flores et al, 2012) in order to set up a conceptual model of a sinkhole system and gain more knowledge on the geomorphology of the site
Summary
The main source of fresh water in the Yucatán Peninsula is a regional unconfined karst aquifer that is constituted by sedimentary limestones (Bauer-Gottwein et al, 2011). Sinkholes are natural geological features connecting the land surface with underground karst terrains, and they are formed when rainwater dissolves limestone, creating underground voids (Coškun, 2012). Two main groups of sinkholes have been identified in the genetic classification (Williams, 2004; Gutierrez et al, 2008, 2014). The first group comprises solution sinkholes, which are formed by differential corrosion, lowering the ground surface where karst rocks are exposed. The second group comprises subsidence sinkholes, which result from both subsurface dissolution and downward gravitational movement
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