INTERIOR CAVITIES AND EXTERIOR SURFACE TEXTURE OF DETRITAL QUARTZ OF SOME EGYPTIAN CLASTIC SEDIMENTS

Abstract

Cavities of freshly fractured surface and the exterior surface texture of detrital quartz grains were examined and photographed with the help of the scanning‐electron microscope at different magnifications. Three formations of Egyptian clastic sediments are used for this purpose namely: (a) Carboniferous sandstone of west‐central Sinai, (b) the so‐called Nubian sandstone of Early Cretaceous(?) age from southern Egypt, and (c) Oligocene sand accumulations from the vicinity of Cairo.It is concluded from the present study that in most cases the intracrystalline cavities have an average diameter of less than 10 microns. Different shapes can be acquired by these cavities‐ranging between irregular and negative crystal forms. The distribution of ca vities seems to be mainly along the fractures and the planes of growth but random distribution is sometimes observed.Examination of the surface features also shows that the depositional environment for Sinai and Aswan sandstones is aeolian with more effective diagenetic alteration in the first type of deposit. In the case of Cairo sandstone, the surface impressions of the quartz confirm the alluvial environment of deposition.