Assessment of geohazards of karstified limestone in Al-Coeffiah area, Benghazi plain, NE Libya

Abstract

Al-Coeffiah karst terrain is located in Benghazi plain which is a part of Al-Jabal Al-Akhdar anticlinorium, northeast Libya. The exposed stratigraphic sequence of the area is largely represented by the Middle Miocene limestone rocks of Benghazi Formation. The area is affected by abundant karstic features such as caves and giant dolines with many subsurface voids and canal networks which extends for several kilometers. This research is based on field observations combined with analysis of high-resolution satellite imagery of Al-Coeffiah karst terrain. The main aim is to assess potential geohazards provided by the karst features, including (i) rock failure, (ii) groundwater pollution, and (iii) geochemical processes. The potential geohazards have been found to lies in the large caves at shallow depths such as Al-Jebah, Habibi, Merisi, and Boukarmah doline-caves. In addition, there is a greater geohazard in fractured karst terrains which are created by dolines in soft sediments. Chemical and bacteriological analyses indicate that the groundwater pollution in Al-Coeffiah area and its surrounding regions is considered as one of the most serious problems largely due to the seepage of sewage water through karst phenomena particularly during the last 10 years.