ASTER mapping of limestone formations and study of caves, springs and depressions in parts of Sultanate of Oman

Caves, springs, and large depressions of limestone karst formations are becoming more attractive tourist places and have potential importance on socio-economic development. The present study is a multi-scale point of view on limestone karst, from the space images to microscopic fabric. Here, the karst features consist of limestone formations of Cretaceous (Albian–Cenomanian) age of Tanuf Valley and Tertiary (Late Paleocene–Middle Eocene) age of Sur region of parts of Sultanate of Oman which are mapped in the visible near-infrared and shortwave infrared spectral bands of advanced spaceborne thermal emission and reflection radiometer (ASTER) using decorrelated stretch image processing technique and the occurrences of caves, springs, and depressions of the formations in the field were studied. The decorrelated RGB images of ASTER spectral bands 8, 3, and 1 discriminated well the limestone formations and associated lithology. The limestone formations of Tanuf valley (Natih formations of Hajar unit) are thick-bedded, massive, shallow marine limestone and clayey limestone, which have caves and springs. Large depressions are studied as collapsed structures at the boundary between Abat formations; they consist of gray to white marly or micritic limestone with chert nodules and Seeb Formation of bioclastic limestone, calcarenite, marl, and sandstone of Sur region. Interpretations of limestone formations, their occurrences and distributions of caves, springs and depressions of these regions are verified and confirmed in the field and studied in the laboratory. Occurrences of more springs and depressions in the limestone formations of the study sites are interpreted and located on the Google Earth image. The study proved the capability of ASTER sensor in mapping of limestone formations and recommends the technique to other geographical regions where similar geological questions need to be resolved.