Order differences to enhance the delineation of rock units boundaries by using aerospectrometric data of Wadi Al Mushash area, Central Eastern Desert, Egypt: A new approach

Abstract

The present work utilizes airborne gamma-ray spectrometric data, in a trial to refine the surface geological mapping of sedimentary rocks at Wadi Al Mushash, Central Eastern Desert of Egypt. The acquired aerospectrometric data were supported by the surface geology concerning the study area. This area is mainly covered by sedimentary rocks of Tertiary to upper Cretaceous as Nubian Sandstone Formations (Quseir Clastics and Tarif Sandstone), Duwi Phosphates Formation, Dakhla Shale Formation, Esna Shale Formation, Tarawan Formation, Thebes Formation, and Quaternary deposits. High-resolution airborne gamma-ray spectrometry can be very helpful in mapping the surface geology. The method provides estimation of the apparent surface concentrations of the most common naturally occurring radioactive elements, such as potassium (K), equivalent uranium (eU) and equivalent thorium (eTh). This work is based on the assumption that, the absolute and relative concentrations of these radioelements vary measurably and significantly with lithology. The composite image technique is used to display and simulate three parameters of the radioelements concentrations. The technique offered much in terms of lithologic discrimination, based on color differences and showed efficiency in defining areas, where different lithofacies occur within areas mapped as one continuous lithology. The Differences technique is used to delineate contacts of the rock units and the mainly structures of the study area. It is based mainly on varying in change of concentration of successive total count measurements within each line in the study area. Then, a suitable difference order is selected and matched to original measured line. Moreover, plotting the suitable order as grid and applied grid peaks on this grid. Then, these ridge grid peaks are symbolized over surface geological information and prepared radioelement composite map. This provides more detail about the surface geology, and addition more contacts occurred within original rock units. These subdivisions of rock units may be related to one formation that consists of more than one member having a different composition.