The aim of this study is to improve our knowledge of the processes that lead to clay smear during faulting of a layered sand-clay sequence in an analogue sandbox model. We carefully characterized mechanical properties of the materials used by a series of geotechnical tests. Displacement field was quantified using PIV (Particle Image Velocimetry). The model is water-saturated to allow the deformation of wet clay and sand in one experiment comprising a sand package with a horizontal layer of clay above a predefined rigid basement fault. The thickness and rigidity of the clay layer are the parameters varied in this study. The model shows a range of structures that are related to competence contrast between sand and different clay types. Results show ductile shearing of soft clay with a transition to brittle fracturing of stiff clay accompanied by the formation of rotating clay blocks in the fault zone. Localized deformation is observed through time showing (i) the propagation of one active fault migrating laterally through the sediment package, and (ii) the formation of a stable prism between two or more active faults that gets progressively smaller with minor rotation of the hanging wall fault. Continuous clay smear is observed resulting from the lateral injection of clay as well as from a reworked mixture of sand and clay.
The Yucatán Peninsula is mainly composed of limestone. Cozumel Island is part of the Yucatec carbonate platform. Dissolution processes in the limestone lead to karstification. Groundwater preferentially flows into karstic cavities. Due to its geological structure the karstic aquifer shows a high vulnerability to anthropogenic impacts. This study investigates the impact on groundwater in the area of the informal settlement "Las Fincas". Due to the informal urbanization of the settlement there is neither a public water and power supply nor a sewerage nor waste disposal system. Groundwater samples were taken in a number of domestic wells that are in use for local water supply in "Las Fincas" and tested for typical indicators of anthropogenic pollution. Distinct evidence of fecal contamination was found. The evaluation of a reference analysis of wells outside "Las Fincas" also showed a significant fecal contamination. Two aspects were considered as a reason for the fecal pollution. On the one hand there is the pollution of wastewater and feces by the local residents. On the other hand, there is the practice of the grouting of treated wastewater in deeper zones of the aquifer by the local water supplier. For further investigation a long-term monitoring was established in order to take groundwater samples and record groundwater levels frequently. The study documents the hydrodynamic and hydro chemical conditions of the aquifer and gives recommendations for the use of groundwater without any health risk.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.