Middle and Late Eocene Ostracoda from Gebel El Mereir, Nile Valley, Egypt

Abstract

Middle and Late Eocene deposits assigned to the El Mereir, El Fashn and Qarara Formations, middle Egypt, yielded 26 species of marine Ostracoda of which the following are new: Loxoconcha pseu- dopunctatella, Schizocythere fadlensis, Digmocythere omarai, Bythocypris ? mereirensis, Anticythereis saidi, A. seylingi, Costa bassiounii and C. nilensis. Smaller and larger foraminifera indicate a late Lutetian age for the El Fashn and Qarara rock-units, whereas the El Mereir Formation appears to be Late Eocene in age. INTRODUCTION In the region of Gebel El Mereir, on the eastern side of the Nile River, Middle Egypt, Middle and Late Eocene deposits are exposed. Previous micropaleontological investigation (Said, 1951; Krasheninnikov and Ponikarov, 1964; Hume, 1965) of these sections has emphasized the larger foraminiferal assemblages, and the ostrecode faunas have not been described. Moreover, except for the series of studies by Bassiouni (1969, 1970, 1971) of middle and upper Eocene ostracodes from the lower Nile Valley, there is little published information on Eocene ostracodes from this part of the world. Hence a study of the ostracodes from Gebel El Mereir was undertaken. MATERIAL AND METHODS Because of their friable nature, bulk samples required no mechanical disintegration but were simply washed, fractions were decanted and then dried, and ostracode valves and carapaces were picked from the residue using a fine brush. Following examination with a light micro- scope, scanning electron photomicrographs were taken of type speci- mens at the Museum of Comparative Zoology, Harvard University. Unfortunately, many specimens consisted of the entire carapace, and the 2 valves could not be separated without damaging the shell. Thus, examination of internal features such as hingement, duplicature and muscle scars was sometimes impossible. Nevertheless, preservation of the external surface of carapaces was generally good and generic assignments could be made with confidence for most taxa. Others, requiring examination of internal features, were given questionable generic assignments.