Morphostructural Analysis and Active Tectonics of the Northeastern Constantine Basin, Algeria: Insights from Morphometric Indices and Structural Lineaments

Abstract

Since their formation, the Maghrebids have been influenced by major tectonic movements in geological history. These events have resulted in morpho-structural arrangements that are still poorly understood, particularly in the northeastern of the Constantine Basin. This study aims to fill this gap with an integrated morpho-structural analysis, based on: (i) detailed field mapping, (ii) detailed lineament analysis based on aerial and satellite imagery, and (iii) the calculation of quantitative geomorphological indices grouped in the IRAT (Indice de Tectonique Active Relative). Seven morphometric indices were extracted from a 10 m resolution DTM and applied to the Kef Hahouner (KHB) and Guendoula Messigla (GMB) watersheds. These are the hypsometric integral (H_i), mountain front sinuosity (S_mf), valley floor width/height ratio (V_f), asymmetry factor (A_f), basin shape index (B_s), transverse topographic symmetry factor (T) and stream length gradient (S_L). The ENE-WSW trending Kef Hahouner-Aïn Berda (KHAB) sinister strike-slip fault crosses both basins. It constitutes the main structure, identified through more than 500 lineaments, accompanied by more recent faults oriented N-S and NW-SE. The average IRAT S/N score is 2.0, classifying the zone as class 3 (moderate activity). However, several indicators suggest that this moderate classification is underestimated: S_L values exceed 600, V_f ratios are below 0.5, the S_mf of the KHB mountain front is 1.11, and A_f values indicate asymmetrical basin tilting. In addition, the low B_s values (1.43-1.58) seem to testify to tectonic control. This suggests that the IRAT probably underestimates the actual level of activity. By combining morphometric data with GIS and field measurements of offset geomorphic markers, the area was reclassified as class 2 (high activity). Our results show that an active fault corridor strongly modifies drainage, relief generation and sediment dynamics. They underline the importance of combining geomorphological indicators with structural analysis to improve neotectonic assessments in structurally complex regions.