PLIOCENE FACIES AND FOSSIL CONTENTS OF QARET EL-MULUK FORMATION AT WADI EL-NATRUN DEPRESSION, WESTERN DESERT, EGYPT

A sequence of late Pliocene sediments (Qaret El-Muluk Formation) cover s large areas within Wadi El-Natrun depression; at the western periphe ry of the Nile Delta. The exposed sequence is composed of friable sand s, mudstones, shales and minor limestones with combined total thicknes s of approximately 50 m. The fossil content consists of fresh and brac kish water elements; charophytes, ostracods, gastropods, oysters and b enthonic foraminifera. Planktonic forams which suggest marine influenc e have been also recorded. Terrestrial and aquatic continental vertebr ate fauna includes mammals, reptiles, fish and aves. Several subtypes of ichthyoliths have been discovered in this study. Both lithological and paleontological data testify to a depositional environment which b elongs to a marginal region where fluvial and marine deposition meet i n shallow brackish lagoons. The sediments display changes from channel led fluvial sands to deltaic interbedded sands and mudstones to lagoon al shales and limestones to lacustrine chara limestones. Vertical stac king of facies is indicative of a series of transgressive-regressive e vents. The transgression brought shallow lagoonal conditions to the ar ea. The transgressions were incomplete due to high rate of fluvial inp ut. The lagoon dried up intermittently and calcretes and red brown soi ls were formed. Each regression is indicated by river generated elasti c influx. During periods of active fluvial input, fluvial sediments pr ograded lagoonward. The clastic material was probably a mixture of rew orked detritus from older sediments. An admixture of first cycle mater ial from the basement rocks of the Red Sea hills cannot be ruled out. The diversity of provenance argues for several channels of a large riv er which existed during the late Pliocene.