الفهرس 
GEOLOGIC SETTINGOnly 14 pages are availabe for public view
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Abstract
The present work deals with the Lutetian oolitic ironstones of El Bahariya region, Western Desert,
Egypt. The ironstones are accumulated along Cenomanian paleohighs in the northeastern plateau of El
Bahariya Depression. It represents a reduced section and a facies change of the laterally
equivalent thick carbonate succession.
The oolitic ironstone represents an unconformity bounded succession, composed mainly of
autochthonous/para-autochthonous facies rich in ferriferous ooids, oncoids and various ferruginized
skeletal particles. The facies assemblage is organized in two main sequences separated by an
intra-Lutetian unconformity. Each facies sequence starts with a tidal flat/lagoonal mud-ironstones
with minor siliciclastic mudstones. These pass upward to shoals/ megarippled grain- to
pack-ironstone facies.
The ferriferous ooids and oncoids are identical in mineralogy, morphology and microfabric. This
may strength a biogenic role for ooid origin. The ferriferous allochems, matrix and cement
consist essentially of amorphous Fe-oxyhydroxides, earthy goethite, hematite and quartz. Earthy
goethite admixed with amorphous iron oxyhydroxides represent the precursor materials that derived
from the iron bearing Cenomanian elastics.
The main genetic parameters for the concerned ironstone are: a) synsedimentary supply of amorphous
iron; b) slow- to non -deposition; c) in situ reworking; d) biogenic encrustation of iron oxide; e)
local transportation via megaripple migration; f) emergence and oxidation; g) diagenetic
modifications and, h) authigenesis · of iron- and manganese oxides, silica and sulfates. An
intermittent phase of uplift and karstification modified the original marine ironstone facies and
were responsible for the redeposition of iron as cavity filling or laterite deposits.