Dissolution Cavities of Karren type in the Algal Limestone Member of Al Bayda Formation, Sector (3),Wadi Az Zad, Al Jabal Al Akhdar, NE Libya

The study area of Wadi Az Zad is characterized by landforms of relatively stepped terraced escarpment and karst isolated hills.At least three distinct karst features are recognized in the selected measured traverses in the surface exposure of the Algal Limestone Member at Wadi Az Zad which are: Groove karren, Circular karren, and Kluft karren. Histograms of the Algal Limestone Member at the studied traverses (T1-T3) have revealed some relationships of the recognized karren types with their elevation, lithology, topography and number of karrens or density variations. For instance, the observed densities of these surface cavities vary widely from high density of about (5.2 15.8) karren/m^2 for circular type which is found to be associated with flat area and grainstone facies, to an intermediate density of about (1.6-3.2) karren/m2 for groove type which is found to exist mostly in relatively slope areas and in mudstone facies, and eventually to low density of about (0.5-1.5) karren/m^2 for kluft type which is found to be associated with relatively fractured (heavily jointed) and of wackstone – packstone facies. These surface dissolution cavities are evident to be associated with lithologic and structural characters of the Algal Limestone facies in the study area.