Analysis of Morphology, Morphotectonics, and Morphometry of the Kalut Salt Domes in Northeast Ardakan (Central Iran)

Introduction

Salt domes are among the most important geological structures in evaporitic basins, formed by the upward movement of salt layers under the influence of buoyancy, tectonic pressure, and fault systems. These structures play a major role in tectonic evolution and create diverse geomorphological features such as sinkholes, salt karren, dissolution valleys, and polygonal salt crusts. In arid and semi-arid regions, dissolution and evaporative erosion intensify salt karst development and increase the salinity of soils, runoff, and groundwater resources. Advances in geomatics and remote sensing technologies have enabled quantitative analyses of dome morphology and morphometry, revealing the significant role of faults and tectonic stresses in controlling their geometry and evolution. The Kalut region in northeastern Ardakan represents one of the major salt diapirism zones in Central Iran, where salt domes are mainly developed along faults and anticlines. The present study aims to analyze the morphology, morphometry, and morphotectonics of these domes using geomatic and remote sensing data in order to better understand their formation processes, environmental hazards, and geotourism potential



Methodology





This study collected data through library research, field surveys, satellite imagery, and topographic and geological maps. Field visits verified salt dome outcrops, measured their morphologies, and recorded surface geomorphology. Fourteen representative domes were selected based on size, height, exposure, geographic distribution, proximity to rivers and roads, human activity, and nearby faults. The study area was divided into seven sections to ensure comprehensive coverage. Morphometric analysis used satellite images and digital elevation models to produce elevation maps, river profiles, and dome-river intersections. Indices calculated for each dome included area, perimeter, maximum and minimum elevation, relative height, axes, radius, and distance to faults, which were then used to compute elongation ratio, circularity, and compactness. Statistical correlations and regression analyses examined differences between dome groups. Morphotectonic analysis included river longitudinal gradient (SL), channel sinuosity, and valley floor width to height ratio (VF) to assess tectonic activity and landscape evolution. Field surveys complemented satellite data by observing polygons, cauliflower shapes, sinkholes, karren, sediment cover, vegetation, and human impacts on morphology. All data were integrated in a GIS-based framework, enabling evaluation of dome distribution, geometric and morphologic indices, relationships with rivers and faults, and temporal changes in salt expansion. This comprehensive approach provided a robust understanding of the structure, evolution, and environmental interactions of the salt domes in the region.



Results

The research findings indicate that the salt domes in the northeast and southeast of Ardakan have developed and evolved under the combined influence of tectonic, dissolutional, and erosional processes. Field surveys, satellite imagery, and geological map analysis show that most domes formed along active faults and fractures, highlighting the critical role of tectonics in their elongation, uplift, and spatial distribution. Surface landforms such as salt karren, sinkholes, salt polygons, cauliflower-like forms, salt flats, and cliffs indicate ongoing dissolution and erosion processes. Sinkholes are the most frequent karst features, with their distribution closely linked to fault trends.Analysis of morphotectonic indices, including SL, Smr, and VF, reveals active tectonics in the area. High values of longitudinal gradient and channel sinuosity indicate geomorphic instability and the impact of tectonic uplift on drainage networks, while low VF values reflect V-shaped valleys and the youthfulness of erosional and tectonic processes. Morphometric studies show that domes closer to faults are more elongated, while those farther from faults are more circular and uplifted. Significant correlations between distance from faults and parameters like area, elongation, and uplift demonstrate the direct control of faults on the geometry and evolution of salt domes. Overall, the results suggest that active tectonics, along with dissolution processes and arid climatic conditions, are the primary factors controlling the morphology and development of Ardakan's salt domes



Conclusion

This study showed that the salt domes in the northeast of Ardakan have formed and evolved under the simultaneous influence of geomorphological, climatic, and neotectonic processes. Field surveys, satellite imagery, and morphometric index analysis indicate that active salt dissolution, water and wind erosion, and fault activity are the main factors shaping and evolving the geomorphic features of the region. The presence of salt karrens, sinkholes, salt polygons, cauliflower-like forms, salt flats, and escarpments reflects the high dynamism of the environment and the continuity of karstic and evaporative processes. Neotectonic indices, including SL, Smr, and VF, revealed relatively high tectonic activity in the area. High SL values in downstream sections, river sinuosity of 1.40, and the predominance of V-shaped valleys indicate active tectonic uplift and erosional imbalance. The existence of river terraces, river imposition on salt domes, and meandering river development provide further evidence of ongoing neotectonic activity. Morphometric studies also showed that the shape, size, and elevation of the domes are closely related to their proximity to faults. Domes near faults are more elongated and develop along fractures, whereas domes farther from faults are more circular and elevated. Overall, the current geomorphology of the salt domes in northeast Ardakan results from the complex interaction of salt diapirism, erosional processes, and active neotectonics, continuously influencing the landscape evolution of the region.