Karst water resources play an important role in drinking water supply but are highly vulnerable to even slight changes in climate. Thus, solid and spatially dense geological information is needed to model the response of karst hydrological systems to such changes. Additionally, environmental information archived in lake sediments can be used to understand past climate effects on karst water systems. In the present study, we carry out a multi-methodological geophysical survey to investigate the geological situation and sedimentary infill of two karst lakes (Metzabok and Tzibaná) of the Lacandon Forest in Chiapas, southern Mexico. Both lakes present large seasonal lake-level fluctuations and experienced an unusually sudden and strong lake-level decline in the first half of 2019, leaving Lake Metzabok (maximum depth ∼25 m) completely dry and Lake Tzibaná (depth ∼70 m) with a water level decreased by approx. 15 m. Before this event, during a lake-level high stand in March 2018, we collected water-borne seismic data with a sub-bottom profiler (SBP) and transient electromagnetic (TEM) data with a newly developed floating single-loop configuration. In October 2019, after the sudden drainage event, we took advantage of this unique situation and carried out complementary measurements directly on the exposed lake floor of Lakes Metzabok and Tzibaná. During this second campaign, we collected time-domain induced polarization (TDIP) and seismic refraction tomography (SRT) data. By integrating the multi-methodological data set, we (1) identify 5–6 m thick, likely undisturbed sediment sequences on the bottom of both lakes, which are suitable for future paleoenvironmental drilling campaigns, (2) develop a comprehensive geological model implying a strong interconnectivity between surface water and karst aquifer, and (3) evaluate the potential of the applied geophysical approach for the reconnaissance of the geological situation of karst lakes. This methodological evaluation reveals that under the given circumstances, (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. Our results show that the combination of seismic methods, which are most widely used for lake-bottom reconnaissance, with resistivity-based methods such as TEM and TDIP can significantly improve the interpretation by resolving geological units or bedrock heterogeneities, which are not visible from seismic data. Only the use of complementary methods provides sufficient information to develop comprehensive geological models of such complex karst environments

中文翻译：

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综合的陆地和水上地球物理勘测为墨西哥南部大型喀斯特湖突然干燥提供了启示

岩溶水资源在饮用水供应中起着重要作用，但极易受到气候甚至微小变化的影响。因此，需要固体和空间密集的地质信息来模拟岩溶水文系统对这种变化的响应。此外，湖泊沉积物中存档的环境信息可用于了解过去的气候对岩溶水系统的影响。在本研究中，我们进行了一次多方法地球物理调查，以调查墨西哥南部恰帕斯州拉坎登森林的两个喀斯特湖（Metzabok和Tzibaná）的喀斯特湖的地质情况和沉积填充物。这两个湖都表现出较大的季节性湖面波动，并且在2019年上半年经历了异常突然而强烈的湖面下降，留下了Metzabok湖（最大深度约为25 m）完全干燥，Tzibaná湖（深度约 70  m）的水位下降了约。15 米。在此事件发生之前，我们在2018年3月的湖水高位站立期间，使用亚底剖面仪（SBP）收集了水基地震数据，并使用新开发的浮动单回路配置收集了瞬变电磁（TEM）数据。2019年10月，在突然的排水事件之后，我们利用了这种独特的情况，并直接在Metzabok湖和Tzibaná湖裸露的湖面上进行了补充测量。在第二个活动中，我们收集了时域感应极化（TDIP）和地震折射层析成像（SRT）数据。通过整合多方法数据集，我们（1）确定5–6  m 两个湖泊底部的厚厚的，可能未被扰动的沉积物序列，适合于将来的古环境钻探活动；（2）建立了一个综合的地质模型，暗示了地表水和岩溶含水层之间的强相互联系，（3）评价了该湖的潜力。应用地球物理方法勘察喀斯特湖泊的地质情况。该方法学评估表明，在给定的情况下，（i）SBP和TDIP相图一致地分辨了覆盖湖床的细粒度湖相沉积物的厚度，（ii）TEM和TDIP电阻率图一致地检测了石灰岩的上限基岩和河流三角洲河流沉积物的几何形状，（iii）TDIP和SRT图像表明存在一层将湖相沉积物与石灰岩基岩分隔开的层，该层由与湖相沉积物混合的崩塌碎屑组成。我们的结果表明，将地震方法（最常用于湖底勘查的方法）与基于电阻率的方法（如TEM和TDIP）相结合，可以通过解析地质单元或基岩异质性（从地震中看不到）来显着改善解释。数据。仅使用补充方法即可提供足够的信息，以开发此类复杂岩溶环境的综合地质模型 TEM和TDIP等基于电阻率的方法通过解析地质单元或基岩非均质性（从地震数据中看不到），极大地提高了解释能力。仅使用补充方法即可提供足够的信息，以开发此类复杂岩溶环境的综合地质模型 TEM和TDIP等基于电阻率的方法通过解析地质单元或基岩非均质性（从地震数据中看不到），可以最广泛地用于湖底勘察。仅使用补充方法即可提供足够的信息，以开发此类复杂岩溶环境的综合地质模型