Sedimentary Nature of Nile Sediments in Upper Egypt:
Relationships and Implications to Weathering and Climate of Provenance
Abbas M. Mansour, Hans Kurtzweil1
and Mohamed R. Osman
Geology Dept., Fac. Sciences, South Valley Univ., Qena, Egypt; 1Inst.
Petrology, Vienna Univ., Austria |
Samples were collected from cores in islands and sections of the adjoining banks, and
PreNile sediments in the area between Nag Hammadi and Aswan, Upper Egypt. They were
analyzed for grain size, mineral and chemical compositions in order to interpret their
differences and nature of provenance.
Islands and banks sediments reflect low chemically weathered provenance with poor drainage
or low rainfall. Furthermore, PreNile sediments reflect lower chemically weathered
provenance than other Nile sediments. Weathering and transport processes did not affect
their mineral diversity, but changes in mineral proportions by chemical differentiation
are recorded. The sediments composition changes vertically in the cores and sections
studied. Grain size sorting mainly controls this. Composition reflects the upward increase
of most elements in the islands. In the contrary, they are richer in the lower parts of
banks. The relatively higher Pb and Cr concentration in the upper sediments of islands
compared to the banks sediments is attributed to local pollution due to the presence of
boats or due to the influence of domestic wastewater.
The sediments of banks are mainly derived from basic volcanic rocks, whereas the PreNile
sediments were derived from acidic and metamorphic rocks and the pre-existing sedimentary
rocks. Islands sediments are mainly composed of mixture of the reworked detritus resulting
from the denudation of bank sediments, the scourig of the river channel bed and the flush
floods of the adjacent wadis.
Tectonic setting of source rocks as revealed by sediment composition infers a passive
margin for PreNile sediments and ranges between active margin and oceanic and continental
island arc for islands and banks sediments.
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