Gebel Qatrani, located north of the Faiyum Depression in Egypt, is
characterized by a diversity of geoheritage and abundance of very
impressive desert landforms (Sallam et al. 2018; Al-Dhwadi and Sallam
2019). In the Gebel Qatrani area, the mushroom rocks, inselbergs
and buttes are very common geomorphic features, which are generally
found in many parts of the Egyptian deserts (Plyusnina et al. 2016; Sallam
and Ruban 2017). These desert landforms are mainly the result of
wind erosion (Goudie 2008). The Faiyum Depression formed through
a long time of deflation, especially where the limestone packages are
thin, cracked, and jointed or even dissected by faults, hence prone to
erosion (Said 1990). The desert landforms commonly occur in the
Middle Eocene rocks belonging to the Birket Qarun Formation that is
well exposed at the Gebel Qatrani area, north of the Qarun Lake. The
Birket Qarun Formation consists of sandstones, shales and sandy limestones
deposited in a low-energy open shallow-marine shelf (Swedan
1992; Anan and El-Shahat 2004; Strougo et al. 2013). The mushroom
rocks are composed of soft rocks (calcareous sandstone) at the base,
capped by harder rocks (quartzitic sandstone) at the top. This shallowing
upward sequence (Anan and El-Shahat 2004) permitted the lower
soft rocks to be readily eroded by sandstorms than the overlying harder
packages, so the whole rock after a certain time looks like a mushroom
with a narrow stem and broad top (Fig. 1). If wind erosion continues
excessively for a long time, the slender stem body collapses. Southwestward,
at the Wadi Hitan (Valley of Whales) area, the mushroom
rocks are also common where their cap rocks displaying a characteristic
tafoni (small cave-like) structure formed mostly by the action of wind
erosion. The height of the mushroom rocks in the Gebel Qatrani and
Wadi Hitan areas ranges from ~ 1.5 to 5 m. |
