Document Type : Original Article
Authors
1
Geology , faculty of science, New Valley University
2
Geology , faculty of science, Ain shams University
3
Geology, faculty of Science, Asuit University
Abstract
Over the last few years, remote sensing techniques have become an indispensable in Earth science, especially in geological investigation. El Fayum-Greater Cairo region is characterized by strong diversity in the rocks lithologies (Upper Cretaceous-Quaternary units) and the affecting structures, as well as the agricultural activities at both sides of the Nile River in the Nile Valley and tow water lakes. These geologic diversities encourage us selecting this region to applying the PCA and ICA techniques for the Landsat 8 OLI and Sentinel-2A imagery data. These two applications are used to define the ratio combinations for each sedimentary lithologic facies and mixed facies, basaltic flows, agricultural systems, and water bodies of different salinity. Several geologic factors are determined controlling the quality appearances on the processed images, which are the lithologic homogeneity, percent of each lithology in the mixed facies, rock unit thickness, outcrop width, weathering intensity, surficial sediment covers, which part of the unit is exposed, and topographic occurrence of the unit. Three orders of qualities are suggested for the band combination ratios that used in the separation of limestone, limestone mixed facies, sand-sandstone, sandstone mixed facies, basaltic flows, clastic and carbonate mixed facies, agricultural cover, water bodies (Qarun and Wadi Rayan lakes and Nile River). These combination ratios are controlled by the lithologic homogeneity, percents of lithologies in the mixed facies, rock unit thickness, outcrop width, weathering intensity, surficial sediment covers, which part of the unit is exposed, and topographic setting of the unit. The Upper Eocene sandstone and claystone mixed facies are well represented on the ICA images rather than those on the PCA. The whole basaltic flows in the study area are discriminated well on most images whereas the large (thick) flow parts are separated only on the PCAL (6/5/3RGB) and ICAs (7/2/11RGB). The east-west faults that offseted the basaltic sheets are clearly mapped on the PCAL3/1/2RGB, ICAL3/1/2RGB, and ICAL4/7/3 images, as well as they are mapped on the ICAs11/2/12RGB and ICAs3/11/5RGB.
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