GEOMORPHOMETRY OF TRIASSIC LANDFORMS: A QUANTITATIVE GEOMORPHIC ANALYSIS OF SALT EXTRUSIONS USING DEM, "DIAPIRIC AREA", NORTHERN TUNISIA, TUNISIA

The "diapiric area" within the northern Tunisian Atlas presents a complex and heterogeneous geological framework leading to various geomorphic landforms among them there are numerous Triassic salt extrusions having an evident impact on the topographic configuration, shaping and dynamics. They also have an apparent NE-SW-trending outcrops characterized by an unusual sedimentary contacts with younger rocks aged from Cretaceous until Upper Cainozoic.

In the present work, landforms characterization of the study area was carried out using the geomorphometric approach which is mainly based on the Digital Elevation Models (DEMs) analysis into GIS environment using spatial data analysis tools. Several topographic attributes and parameters have been calculated, combined and interpreted: basin hypsometric curve and integral, longitudinal river profile, stream-length gradient index normalized by the graded river gradient (SLk index), mountain-front sinuosity, relief curvature analysis, bulk erosion and residual mapping, topographic swath profile, drainage basin asymmetry factor, and trend surface analysis with landform generalization. Moreover, qualitative hydrographic investigation (stream network configuration, hydrographic diversion, river meandering, etc.) was also considered in this study.

The main results show evidences of a positive correlation between salt extrusions, landform configuration and Quaternary drainage network evolution. We postulate, according to the results of our analysis and inferences, that most of these Triassic landforms have accommodated recent topographic growth initiated and conducted by active neo-halokinesis and salt rock uplifting, stimulated by additional Atlasic shortening. They also tends to be highly dynamic and, thereafter, generating high sediment yields into surrounding basins and areas.