الفهرس 
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Abstract
Ten sections of the exposed Quaternary Nile and the Holocene sand sheets sediments were measured and described at the Kafr el Gebel area south of the Sphinx, Giza, Egypt. These sections are Kafr el Gebel Gravels, Kafr el Gebel I which divided to 6 sections(1,2,3,4,5,6), Kafr el Gebel II, Sand Sheets I and Sand Sheets II. Several features and observations were recorded. Among these are elevations, bedding, lamination, cross bedding and texture. This study is mainly concerned with paleoenvironmental interpretation and mineralogical study of the exposed Nile terraces of the Quaternary channel bars sediments.
The lithostratigraphy of the study area are Kafr el Gebel Gravels section belongs to Early Pleistocene, Kafr el Gebel I which divided to 6 sections(1,2,3,4,5,6) sections belong to Middle Pleistocene , Kafr el Gebel II belongs to Late Pleistocene, finally Sand Sheets I and Sand Sheets II belong to the Holocene. The Middle Pleistocene sections are correlated with Abbassia Formation while the Early Pleistocene section is correlated with Qasr el Basil Formation.
The quantitative and qualitative determinations of the grain size analysis of the Quaternary sediments are measured. Most of them are a large scale plannar wedged shape cross bedding coarse to very coarse sand grains transported by traction and saltation agents that indicate a high energy current of the defunct network braided Nile channels. Whereas, sand sheets I and II were derived from the channel bars of the Pleistocene Nile terraces.The Kafr El Gebel Gravels are bladed to disc shape. The average shapes of boulders are mainly disc (55.8%), spheroidal shape (26.7%), rod (10.5%) and bladed shape (7%) as well as (bladed+disc) shape = (62.8%). It indicates that these gravels are transported and deposited by the channel water currents.
The investigated thin sections gravels of the Kafr el Gebel Gravels section revealed that most of them are of sedimentary origin beside few igneous and metamorphic clasts. It indicates that the provenances of these gravels are derived from older formations (Eocene, Oligocene and Miocene). Whereas, the igneous and metamorphic clasts are most likely derived from the Red Sea Hills.
X-ray diffraction analyses of samples show that the identified minerals assemblages of the studied samples are quartz, albite, calcite, gypsum) and illite. The presence of albite means that the sediments are derived from acidic igneous rocks. Whereas, gypsum is derived from Miocene evaporates. The calculated Carbonate% values of the studied sediments range from .51% to 28. 65 % (average 8.86%).
Geochemical analysis shows that these sediments are mainly composed of SiO2. It is the most abundant oxide, this fact may be related to the abundance of quartz and chert fragments in the studied samples as revealed from petrographical characteristics. The enrichment of SiO2 over Al2O3 is may be due to the mechanical and chemical process in source rocks. This silica enrichment reflects the duration and intensity of weathering and destruction of other minerals during transportation. Silica abundant may be related to the ratio of silicate to non-silicate minerals. Thus silica content in sediments approximately matches with mineralogical maturity of siliciclastic rocks.
CaO oxide shows a high ratio in the Early Pleistocene more than the Middle Pleistocene. Whereas, the other major oxides such as SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, K2O and P2O5 oxides show high ratios in the Middle Pleistocene more than the Early Pleistocene. These observations confirmed that the Early Pleistocene sediments are derived from the Red Sea Hills as local tributaries but the Middle Pleistocene sediments are derived from the Ethiopian tributaries.
Mineralogically, the light fractions consist of sub-rounded to sub-angular quartz with a little amount of feldspar. The investigated heavy minerals are zircon, tourmaline and rutile of the ultrastable group. Epidote, staurolite, kyanite and garnet of the metastable group. Amphibole is mainly represented by hornblende while pyroxene is mainly represented by augite of the unstable group. ZTR index for the studied samples lies below 25 % which indicating mineralogically immature sediments. The dominance of subangular to subrounded heavy mineral grains with low ZTR index in the studied sediments reflects instability of the sediments. Also we conclude that the non-opaque heavy minerals in the study area are originally derived from gneisses and schist metamorphic rocks as well as igneous rocks of the Ethiopian plateau, and they were derived by the Nile water from pre-existing sedimentary sources.