Реферат: Sistema Zacatón, a karst area in northeastern Mexico known for deep phreatic shafts and hydrothermal water, also displays a unique travertine morphology. Some of the sinkholes are dry or contain shallow lakes with flat travertine floors; other deeper water-filled sinkholes have flat floors without the cone of collapse material commonly observed in these types of shafts. We tested the hypothesis that these floors have large water-filled voids beneath them using electrical resistivity imaging (ERI) to image both open cenotes and travertine-covered sinkholes. . Three separate flat travertine caps were imaged using ERI; (1) La Pilita, which is partially open, exposing the structure of the cap over a deep water-filled shaft; (2) Poza Seca, which is dry and vegetated; and (3) Tule, which contains a shallow (<1 m) lake. A fourth line was run adjacent to the open cenote Verde. ERI at La Pilita tested the morphology of travertine surrounding this 110+ m deep cenote. The existence of some water-filled void spaces interpreted from ERI data was verified by SCUBA exploration and new voids are inferred. The ERI lines at Poza Seca demonstrated a thin (<2 to 4+ m) layer interpreted as the travertine cap with a conductive region (consistent with the resistivity of water) under the layer extending to at least 25 m depth beneath the cap. No lower boundary of the void is evident in the ERI data. The line at Tule also produced geophysical evidence of a large water-filled void beneath a thin (<2 to 4+ m) cap. A deep, higher resistivity layer indicates a flat lower boundary 45 m deep that may be a second cap, similar to one that exists at Verde. The ERI line adjacent to Verde hints at a deep water-filled cavity below this 45 m deep layer. These findings support the hypothesis of capped water-filled voids and may have implications for paleo-climate models of the late Pleistocene. The capped voids may provide habitats for anoxic microbial communities to evolve in isolated isothermal environments.