Eman Kamel - Faculty of Science, Cairo University, Cairo, Egypt
Mohamed Hammed - Faculty of Science, Cairo University, Cairo, Egypt
Osama Attia - Faculty of Science, Cairo University, Cairo, Egypt

In the recent years, the use of ASTER and Landsat data have become prevalent for mapping different types of rock formations. Specifically, this study utilizes ASTER (L۱B) and Landsat ۸ (AOL) images to map outcrops of various gypsum facies in Ras Malaab area of west-central Sinai. These gypsum facies are part of a lithostratigraphic group called Ras Malaab, estimated to have been formed during the Miocene period. A range of image processing techniques was employed to create the final facies map including quartz and sulphate indices, composite image band combinations, band ratios, principal component analyses, decorrelation stretching, and SAM mapping followed by supervised classification. By using band combinations, mineral indices, and principal component analyses, sulphate minerals were distinguished from their surroundings. Additionally, decorrelation stretches and band ratios were used to differentiate between primary, secondary, faulted gypsum, anhydrite, and carbonates. The SAM rapid mapping algorithm was also an effective tool to distinguish between the main facies in the studied area and to differentiate between primary massive and bedded gypsum. The results of this study were summarized by creating a facies map of the area using supervised classification, which, in addition to petrographic studies, greatly aided in understanding the distribution of the different gypsum facies.

Sulphate index, Band ratio, Spectral Signature