matthiasbuecker / geophysics-chiapas-karst-lakes-se2020

Data set | Water- and land-borne geophysical surveys before and after the sudden water-level decrease of two large karst lakes in southern Mexico

Data set | Water- and land-borne geophysical surveys before and after the sudden water-level decrease of two large karst lakes in southern Mexico

This repository contains raw and processed data along with the Matlab scripts used to prepare the visualizations presented in the manuscript

Bücker, M., Flores Orozco, A., Gallistl, J., Steiner, M., Aigner, L., Hoppenbrock, J., Glebe, R., Morales Barrera, W., Pita de la Paz, C., García García, E., Razo Pérez, J.A., Buckel, J., Hördt, A., and Schwalb, A., Perez, L. (2020). Water- and land-borne geophysical surveys before and after the sudden water-level decrease of two large karst lakes in southern Mexico. Submitted to Solid Earth.

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Summary

The present geophysical study was motivated by the need to determine suitable coring locations for paleolimnological studies in two karst lakes (Metzabok and Tzibaná) of the Lacandon Forest in Chiapas, southern Mexico. We used seismic and transient electromagnetic methods to map the sediment thickness below the lake floor. When lakes were filled in March 2018, we collected seismic data with a sub-bottom profiler (SBP) and transient electromagnetic (TEM) data with a floating single-loop configuration. The latter aimed at assessing the TEM method as an alternative to seismic methods for the investigation of lake sediments and geology. After the first campaign, water levels of both studied lakes dropped dramatically by July 2019, leaving Lake Metzabok (maximum depth ~25 m) dry and Lake Tzibaná (~70 m) with a water level decreased by approx. 30 m. After the sudden drainage of the lakes, we complemented water-borne measurements by a survey carried out on the exposed lake floor in October 2019, when lake levels were still low. During this second campaign, we collected time-domain induced polarization (TDIP), and seismic refraction tomography (SRT) data on the dessicated bed of Lake Metzabok and some dry parts of Lake Tzibaná. By comparing the various data sets, we find that (i) SBP and TDIP phase images consistently resolve the thickness of the fine-grained lacustrine sediments covering the lake floor, (ii) TEM and TDIP resistivity images consistently detect the upper limit of the limestone bedrock and the geometry of fluvial deposits of a river delta, and (iii) TDIP and SRT images suggest the existence of a layer that separates the lacustrine sediments from the limestone bedrock and consists of collapse debris mixed with lacustrine sediments. While our results do not imply that resistivity-based methods could generally replace seismic reflection surveys for lake-bottom reconnaissance, they clearly show that TEM and TDIP surveys can provide important complementary information and resolve additional geological units or bedrock heterogeneities.

Overview

The following table summarizes the measurements and data provided in this repository. Individual data sets and more detailed information can be found in the subfolders of the repository.

Directory	Method	Month/Year of acquisition	Quantity
01_SBP	Sub-bottom profiler (SBP)	10/2018	62 lines
02_TEM	Transient electromagnetics (TEM)	10/2018	96 soundings
03_TDIP	Time-domain induced polarization (TDIP)	03/2019	8 lines
04_SRT	Seismic refraction tomography (SRT)	03/2019	3 lines
05_SIP_lab	Spectral induced polarization (SIP) lab measurements	03/2019	6 samples

Financial support

Financial support for the geophysical surveys was provided by Consejo Nacional de Ciencia y Tecnología (CONACyT) under grant number 252148 and Deutsche Forschungsgemeinschaft (DFG) under grant numbers BU3911/1-1 and PE2133/1-1. Parts of this work were funded through the Austrian Science Fund (FWF) – Agence Nationale de la Recherche (ANR) research project FWF-I-2619-N29 and ANR-15-CE04-0009-01 HYDROSLIDE: Hydro-geophysical observations for an advanced understanding of clayey landslides as well as by the Austrian Federal Ministry of Science, Research and Economy (project: ExploGRAF- Development of geophysical exploration methods for the characterization of mine-tailings towards exploitation).

License information

© 2020 the authors.

This work is licensed under CC-BY version 4.0.

Visit https://creativecommons.org/licenses/by/4.0 or see the LICENSE file for more information.