EXPLORING THE POTENTIAL OF SATELLITE-BASED MULTISPECTRAL AND HYPERSPECTRAL REMOTE SENSING FOR LITHOLOGICAL MAPPING OF SALT DIAPIRS IN THE ZAGROS MOUNTAINS, IRAN

Understanding the origin of giant salt systems is often hampered by the lack of direct exposure of salt deposits. In the case of salt diapirs in the Zagros region, for example, the presence of caprocks conceals the salt. The diapirs, fed by the Precambrian Hormuz Evaporites and often associated with natural resources, intrude into the fold–and–thrust belt of the Zagros Mountains. Investigating lithological compositions of the caprocks could thus serve as a proxy to comprehending salt diapirism in the region and the origin of the Hormuz Evaporites. However, despite their scientific and economic significance, the caprocks remain poorly lithologically mapped. We explore the potential of satellite-based ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) multispectral and EnMAP (Environmental Mapping and Analysis Program) hyperspectral remote sensing for efficiently improving lithological maps of the caprocks in the region.

Our method integrates rock and mineral spectroscopy into analyzing ASTER and EnMAP images. We tested the method on the caprocks of selected salt diapirs and we subsequently extended the method to the rest of the Zagros region. We first evaluated the performance of previously established ASTER-based mineral indices to delineate various caprock lithologies. We then investigated temporal and seasonal sensitivity of sulfate-detecting indices to help select satellite scenes that could be co-analyzed for the regional mapping. To validate the accuracy of the indices, we performed spectroscopic characterization of samples collected from the diapirs and applied Spectral Information Divergence (SID) classification on EnMAP images.

Our findings suggest that satellite remote sensing offers an efficient approach to improving lithological maps of exposed salt deposits and related caprocks. However, the accuracy of these maps depends on the spectral and spatial resolutions of the satellite images. We also demonstrate that spectral signals of sulfate-rich outcrops show seasonality, weakening in warm seasons and strengthening in cold seasons. We thus recommend utilizing winter satellite scenes for accurate spectral lithological mapping of exposed salt deposits. In conclusion, our study presents the strengths and the limitations of employing satellite remote sensing for lithological mapping in evaporitic geological settings.