SUBSURFACE LATE QUATERNARY
FLOOD PLAIN SEDIMENTS OF SAQQARA AREK EGYPT:
PALEOENVIRONMENTAL INTERPRETATIONS
MOHAMED ABDEL RAHMAN HAMDAN
Geology Dept., Fac. of Sciences, Cairo Univ., Giza, Egypt
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Late Quaternary Nile sediments taken from two "26 m" cores in the Nile flood plain of Saqqara-ElBadrashin area, S of Cairo, are subdivided into three lithic units, The lower unit (below depth 12 ms) is represented by pebbly medium to coarse-grained quartzose channel sand (Late Pleistocene) deposited by highly seasonal, vagarious, braided river of Ethiopian origin.
The middle unit (between depths of ab. 8 and 12 ms, at Saqqara core only) is massive medium grained aeolian sand, At the lower contact, the lag gravel has traces of desert varnish. This unit represents the terminal Pleistocene arid period in North Africa (between 12,000 and 10,000 BP), where the Nile floods were low.
The upper lithic unit (from flood plain surface to depth 8 ms) represents the Holocene Nile flood. Six Thermoluminescence-age determinations gave, 3500± 350, 7340±730 and 10,110±800 BP for samples taken at depths of 3, 7, 11 ms, respectively at ElBadrashin, and 3250±320, 6181±600 and 8200±800 BP for samples taken at depths of 3, 5 and 8 m at Saqqara core. Mineral study indicates, two flood stages, the lower represented by the interval 3-8 ms (ranging in age from 10,000 to ab. 3500 BP) is characterized by high Amphibole Index, which may indicate equatorial central African origin, This Nile stage can be correlated to the high African lake levels attributed to paleoclimatic changes in East Africa that contributed the Nile discharge and relative sediment-load. The upper stage is represented by thick massive sandy silt, with angular local limestone fragments indicating increase of local fluvial contributions. This Nile silt displays high Pyroxene Index, which may indicate humid condition in Ethiopian hinterland. The top 2 ms are disturbed by the anthropogenic activity during the Pharaonic and later periods.
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