110
A. M. Sharaky
3. Phosphate beds: The Phosphate beds extend over the whole of the escarpment
that bounds the greater Dakhla area from Qasr to Teneida.
4. Variegated Shale: Red clays with some green beds from the base of the
depression. They are formally known as Variegated shales and later called Mut
Formation by Fay and Degen (1984).
5. Nubian Sandstone: The Nubian Sandstone Formation on the Dakhla depression
extending southwards forms a gently rising desert. It is classified into three main
members from Landsat-1 satellite images.
Dakhla depression was formed by erosion during Oligo-Miocene times (Mansour
1973; Beadnell 1901). Differential weathering in the thick shale section capped by
limestone caused successive retreat of the scarp to the north during the Pleistocene.
2.6 Land Use and Land Cover in Dakhla Oasis
The cultivated lands in Dakhla Oasis was doubled to about 210 km
2 (52,000 Fadden)
in 2011 from 110 km
2 in 1984 (Kato et al. 2014). A slight increase in the cultivated
lands was recorded from the Landsat 8 OLI/TIRS C1 Level-1 images between 2014
and 2019 (see Fig. 6).
A false color composites image was produced from three bands 2, 3 and 4 of
SPOT4 satellite images of 1971 and 2011 (Kato et al. 2014). The visual interpretation
helped to give a general idea about land cover changes with time. A noticeable change
was recorded in areas of new land reclamation in the Dakhla Oasis where some of
the deserts were changed to productive lands.
2.7 Types of Sand Dunes in Dakhla Oasis
The sand dunes in Dakhla Oasis cover a surface area of about 600 km
2 . They are
concentrated in the western part of the oasis, west of the longitude 29° E. The sand
dunes form five parallel dune belts running southwards. They are perpendicular to
the longitudinal axis of the depression (see Fig. 7). In different to northeast African
dunes, the sand dune belts in Dakhla move counterclockwise around a center close
to Gabal Abu Tartur (29° 43’ E and 25° 33’ N).
There are two main types of sand dunes in the Dakhla Depression. They are
crescentic and linear dunes (see Fig. 8). Crescentic dunes are commonly referred to
as barchan dunes. The slope of slip faces of crescentic dunes varies between 31 and
34°. The inclination of the windward slope is more gentle and variable depending on
the dune size. It ranges from 3 to 10° (gentle to moderate slope). Crescentic dunes
form ridges, commonly known either barchanoid or transverse ridges showing a
single slip face on each arc.
A. M. Sharaky
3. Phosphate beds: The Phosphate beds extend over the whole of the escarpment
that bounds the greater Dakhla area from Qasr to Teneida.
4. Variegated Shale: Red clays with some green beds from the base of the
depression. They are formally known as Variegated shales and later called Mut
Formation by Fay and Degen (1984).
5. Nubian Sandstone: The Nubian Sandstone Formation on the Dakhla depression
extending southwards forms a gently rising desert. It is classified into three main
members from Landsat-1 satellite images.
Dakhla depression was formed by erosion during Oligo-Miocene times (Mansour
1973; Beadnell 1901). Differential weathering in the thick shale section capped by
limestone caused successive retreat of the scarp to the north during the Pleistocene.
2.6 Land Use and Land Cover in Dakhla Oasis
The cultivated lands in Dakhla Oasis was doubled to about 210 km
2 (52,000 Fadden)
in 2011 from 110 km
2 in 1984 (Kato et al. 2014). A slight increase in the cultivated
lands was recorded from the Landsat 8 OLI/TIRS C1 Level-1 images between 2014
and 2019 (see Fig. 6).
A false color composites image was produced from three bands 2, 3 and 4 of
SPOT4 satellite images of 1971 and 2011 (Kato et al. 2014). The visual interpretation
helped to give a general idea about land cover changes with time. A noticeable change
was recorded in areas of new land reclamation in the Dakhla Oasis where some of
the deserts were changed to productive lands.
2.7 Types of Sand Dunes in Dakhla Oasis
The sand dunes in Dakhla Oasis cover a surface area of about 600 km
2 . They are
concentrated in the western part of the oasis, west of the longitude 29° E. The sand
dunes form five parallel dune belts running southwards. They are perpendicular to
the longitudinal axis of the depression (see Fig. 7). In different to northeast African
dunes, the sand dune belts in Dakhla move counterclockwise around a center close
to Gabal Abu Tartur (29° 43’ E and 25° 33’ N).
There are two main types of sand dunes in the Dakhla Depression. They are
crescentic and linear dunes (see Fig. 8). Crescentic dunes are commonly referred to
as barchan dunes. The slope of slip faces of crescentic dunes varies between 31 and
34°. The inclination of the windward slope is more gentle and variable depending on
the dune size. It ranges from 3 to 10° (gentle to moderate slope). Crescentic dunes
form ridges, commonly known either barchanoid or transverse ridges showing a
single slip face on each arc.