Karstic geomorphology of carbonate Ouarsenis Piedmont (Boukadir region, Chelif) in Algeria: The role of the Messinian Salinity Crisis

Algeria displays various karst landscapes due to its diversity in lithology, relief, age and climate. On 16th June 1988, the northwest of Algeria, a 60 m wide sudden collapse occurred Chelif Basin about 1 km north marginal carbonate platform. Despite this large event visible dissolutions platform, region has not been classified among areas yet. Our study focuses on Messinian carbonates that form northern piedmont Ouarsenis Mountain range are covered by Plio-Quaternary deposits. The geological geomorphological data we collected reveal present-day karstification is limited at outcropping surface. Present-day dissolution impeded absence topsoil supplying CO 2 presence calcrete improving drainage. Although depth generally diffuse porous friable nature carbonates, two factors can, contrary, concentrate water infiltration: network more or less subvertical fractures and, occasionally, surface, calcrete, independently fracturing nodes There few ponors sinkholes present. endokarst still present as evidenced rare caves. In epikarst, solution pipes shelter caves prevalent. later results from differential weathering relation with facies progressive cementation valleys slopes during river incision. Near valley bottom, shelters arranged steps like terraces. This morphology related base-level lowering deformation uplift piedmont. southern edge Basin, deep (>55m) karstic voids associated paleo-valley incision presently burried We interpreted 1988 paleokarst propose triggering was partly induced aquifers deficit precipitation. formation buried attributed low Salinity Crisis (5.97–5.33 Ma). an upper level filled per ascendum evolution phreatic following Pliocene aggradation. • development paleokarst. sinkhole triggered regional drought lowering. Boukadir platform capped calcrete. Solution main exokarst features. allows well-developed surface drainage network.