Mineralogical Studies on Subsurface Jurassic and Lower Cretaceous Sandstones From the Western Desert, Egypt

Abstract

This paper describes the use of heavy minerals and the characteristics of quartz grains in the study of three exploratory wells (149 core samples) in the northern Western Desert, Egypt. The studied sandstones are characterized by a predominance of tourmaline, zircon, rutile, anatase. epidote, garnet, monazite. staurolite and chlorite, in decreasing order of abundance. In general, there is no distinctive heavy‐mineral variation between Jurassic and Lower Cretaceous sands. Examination of the frequency distribution of the different types of inclusions in the quartz revealed that abundant rutile needles reflect a metamorphic terrane and a plutonic environment. Abundant tourmaline, microlites and devitrified magmatic relicts reflect acidic intrusive/extrusive parent rocks. The abundance of rutile with apatite and zircon is interpreted as being derived from host quartz of various parent rocks. The alteration in some inclusions (segmented rutile needles, spotted apatite and dark zircon) suggests possible dynamic disturbance of the area, resulting in the introduction of inclusions and devitrified and/or altered primary solid inclusions. It is concluded that the Jurassic and Lower Cretaceous sandstones studied were formed in areas characterized by an arid climate. These conditions led to the decomposition of both unstable and metastable heavy minerals.

New Information Regarding the Holotype of Spinosaurus Aegyptiacus Stromer, 1915

“…I N THE autumn of 1912, the fossil collector Richard Markgraf, with financial support and direction from Bavarian paleontol ogist Ernst Freiherr Stromer von Reichenbach and the Bavarian Academy of Sciences, discovered the partial skeleton of a bizarre predatory dinosaur in Upper Cretaceous (early Cenomanian, -97 Ma, see Ismail et al, 1989;Barakat et al, 1993;El Beialy, 1994, 1995Nabil and Hussein, 1994;Ismail and Soliman, 2001;Ibra him, 2002;Gradstein et al, 2005) rocks of the Bahariya Forma tion exposed in the Bahariya Oasis of western Egypt (Fig. 1, see also Sereno et al, 1998;Nothdurft et al, 2002).…”