Surface and Subsurface Investigations for the Detection and Mapping of Underground Karst Cavities in MChentel Area, Cheria Basin, Northeast of Algeria

A combined approach using the surface geophysical method (microgravimetric survey) and sub-surface investigations (speleology) was undertaken at an experimental karst site located in the MChentel area near Cheria town (Northeast of Algeria). The gravimetric survey, carried out by a gravimeter GNU-KC 444 during March-April 2016, allowed the procurement of 614 gravimetric measurements distributed on the whole of the zone of study. The gravimetric data shows a reduction in the values of the Bouguer anomaly between two collapses. This trend probably implies an effect of karstification that would explain the reduction in the values of the Bouguer anomaly while moving towards the centre of the zone of study. The results provided in this work of underground exploration by the team of speleologists from Polytechnic Nice-Sophia in 2013 and 2014 are particularly well illustrated by the topography of the cavities upstream and the real photographs, the micromorphology and the microstructures of the walls of the cavities explored. The joint application of the microgravimetry and speleology make it possible to evaluate the advantages and effectiveness of the microgravimetry for the detection of underground cavities. This improves knowledge of the karstic system structure of Eocene carbonates in the studied area.