KARST ROCK RELIEF OF QARA AND WHITE DESERT  
(WESTERN DESERT OF EGYPT) 
KRAŠKI SKALNI RELIEF V QARI IN BELI PUŠČAVI  
(ZAHODNA PUŠČAVA V EGIPTU)
Martin KNEZ1, 2, 3, Tadej SLABE1, 2, 3, Magdy TORAB4 & Noura FAYAD5
Abstract UDC 551.3.053:552.54(620.21/.22) 
Martin Knez, Tadej Slabe, Magdy Torab & Noura Fayad: 
Karst Rock Relief of Qara and White Desert (Western Desert 
of Egypt)
The karst rock relief clearly reveals the ways in which the karst 
surface and caves have been shaped and how they have devel-
oped. The oldest traces are the rock features of old karst caves, 
which were formed under climate conditions entirely different 
from the current ones, i.e., in the Pleistocene, and which have 
been dry for a longer period of time. Today, the wind is the pre-
vailing factor in shaping the rock on the surface and in the karst 
of the White Desert near Farafra in particular, where we can 
witness the development of an entire range of wind rock fea-
tures which helps us sort and classify them logically. However, 
in the wadis near the Qara Oasis a unique rock relief is forming, 
in which traces of water flow and dissolution of the rock under 
the sandy deposits are utterly predominant. The rainfall volume 
is low, however, the heavy rainfall events lasting short periods 
of time are enough to shape the less resistant rock. The rock 
features dominating the walls are co-shaped by dissolution and 
aeolian erosion. Crust forms on those parts of the rock surface 
that come in contact with water. The bare surfaces, on the other 
hand, are carved out by the wind. In the places where the crust 
has flaked off, the wind carves out cups. 
Keywords: carbonate rock, rock relief, complexometry, Qara 
Oasis, White Desert (Farafra), Egypt.
Izvleček UDK 551.3.053:552.54(620.21/.22)  
Martin Knez, Tadej Slabe, Magdy Torab & Noura Fayad: 
Kraški skalni relief v Qari in Beli puščavi (Zahodna puščava 
v Egiptu)
Kraški skalni relief tudi tokrat povedno razkriva način ob-
likovanja in razvoj kraškega površja ter jam. Najstarejše sledi so 
skalne oblike starih kraških jam, ki so se oblikovale v povsem 
drugačnih podnebnih razmerah od današnjih v pleistocenu in 
so že dlje časa suhe. Danes je prevladujoč dejavnik oblikovanja 
skale na površju veter in zlasti v krasu Bele puščave pri Far-
afri se razvija celoten nabor vetrnih skalnih oblik, ki služi tudi 
za njihovo smiselno razbiranje in razvrščanje. V vadijih pri 
oazi Qari pa se oblikuje svojevrsten skalni relief, v katerem 
povsem prevladajo sledi pretakanja vode in raztapljanja skale 
pod peščeno naplavino. Padavin je malo, a izrazitejša količina 
v kratkem časovnem obdobju je dovolj za oblikovanje slabše 
obstojne kamnine. Skalne oblike, kakršne prevladujejo na ste-
nah, pa sooblikujeta korozija in vetrna erozija. Na delih skalne 
površine, ki jih dosega voda, nastane skorja. Gole površine pa 
dolbe veter. Na mestih, kjer se skorja odlušči, veter izdolbe 
vdolbine. 
Ključne besede: karbonatna kamnina, skalni relief, komplek-
sometrija, oaza Qara, Bela puščava (Farafra), Egipt.
ACTA CARSOLOGICA 52/2-3, 197-217, POSTOJNA 2023
1 Research Centre of the Slovenian Academy of Sciences and Arts, Karst Research Institute, Titov trg 2, SI-6230 Postojna, Slovenia, 
e-mails: knez@zrc-sazu.si, slabe@zrc-sazu.si
2 UNESCO Chair on Karst Education, University of Nova Gorica, Glavni trg 8, SI-5271 Vipava, Slovenia, e-mails: knez@zrc-sazu.
si, slabe@zrc-sazu.si
3 Yunnan University International Joint Research Center for Karstology, Xueyun road 5, CN-650223, Kunming, China, e-mails: 
knez@zrc-sazu.si, slabe@zrc-sazu.si
4 Damanhour University, Faculty of Arts, Department of Geography, Abadia, Agriculture road, EG-5842001 Damanhour, Egypt, 
e-mail: torab.magdy@gmail.com
5 Damanhour University, Faculty of Arts, Department of Geography, Absom Alsharqia, EG-22821 Kom Hamada, El Beheira, 
Egypt, e-mail: fayyadnoura43@gmail.com
Prejeto/Received: 12. 6. 2023
DOI: https://doi.org/10.3986/ac.v52i2-3.12796 
MARTIN KNEZ, TADEJ SLABE, MAGDY TORAB & NOURA FAYAD
1. INTRODUCTION
The rock relief with the most typical rock features clues 
us into the prevalent ways in which the karst surface 
of the studied areas has been shaped and how it has 
developed. It has never before been presented in these 
karst areas. We have presented mountain karst in dry 
environments (Al Farraj Al Ketbi et al., 2014; Audra et 
al., 2017). Reading the karst rock has once again made 
a major contribution to our understanding of the karst 
being formed on different carbonate rocks in diverse 
parts of the world (Knez et al., 2003, 2010, 2011; De-
bevec, 2012; Knez et al., 2012; Al Faraj Al Ketbi, 2014; 
Gutiérrez Domech et al., 2015; Knez et al., 2015, 2017, 
2019; Slabe et al., 2016, 2021; Knez et al., 2020, 2022).
We began by studying the desert karst surrounding 
the Qara and Farafra oases. The karst in the Qara has 
never been researched before, as access to it is restrict-
ed. First of all, we present select features which we will 
attempt to combine into an overall image of the desert 
karst (Fayad, 2023).
In the Qara Oasis (Qarat Umm Al-Saghir Oasis) 
and the wider area, the formation and evolution of karst 
is significantly influenced by the different carbonate rock 
beds which have been incised by wadis (Figure 1). This 
paper focuses on a selected sample of smaller (tens of 
meters in diameter) wadis (Figure 2a) and their areas of 
contact with larger wadis (hundreds of meters in diam-
eter). In some places, wadi basins are wide, indicating the 
presence of standing water at some point in the past. 
The rock layers display different resistance to 
weathering and have been shaped by different pro-
cesses, giving rise to the distinctive shape of the rocky 
perimeter of wadis and the occurrence of smaller and 
bigger solitary rocks and rock pillars with a unique rock 
relief (Figures 2b, 2c). The rock layers feature different 
carbonate contents and are of varying resistance. 
By slowly dissolving the more resistant layers, it was 
through the action of water that this signature rock relief 
came about. Other layers are less resistant and quickly 
weather. They are more noticeably exposed to eolian 
erosion. They mostly break down into sand, which con-
stitutes the prevalent land cover. The color of the land-
scape reflects the color of the weathered prevalent rock 
layer (Figure 2d). Where such layers predominate, the 
sloping walls are largely covered with sand (Figure 2e). 
The peaks are defined by the resistance of the individual 
layers. Where more resistant layers are underlain by less 
resistant rock, there occur overhanging walls (Figure 2f) 
and mushroom-like rock pillars (Figure 2g). 
In the White Desert (Figure 3), the eolian rock re-
lief is predominant, however, it does characteristically 
intertwine with traces of water and the resulting solidi-
fication of the rock surface into crust. We can discern 
a broad range of typical rock features. The rock relief 
noticeably dissects the surface of hills, cones, rock pil-
lars and rocky ground, forming on the soft, white rock, 
chalk. 
Figure 1: Lower parts of wadis, Qara.
ACTA CARSOLOGICA 52/2-3 – 2023198
KARST ROCK RELIEF OF QARA AND WHITE DESERT (WESTERN DESERT OF EGYPT) 
Figure 2: (a) Cross-section of the wadi, (b) Wall of the wadi, (c) Wall in different rock layers, (d) Wadi, (e) Wall covered by sand, (f) Harder 
layers of the rock on top, (g) Mushroom-like pillar.
ACTA CARSOLOGICA 52/2-3 – 2023 199
1.1. RESEARCH METHODOLOGY
We studied the rock relief and the rock features that com-
prise it. First, we identified the rock features in the field, 
then we discerned their shape and thoroughly mapped 
them. We linked their formation and shape with geologi-
cal characteristics. The numerous photographs aided us 
in further researching the rock features. We then com-
bined the studied karst features into a rock relief. 
We defined the prevalent factors and the interaction 
of factors behind the formation of individual rock fea-
tures. By combining these features into a rock relief, we 
attempted to determine the evolution of karst features. 
In the Qara, we took 10 samples of rock at three lay-
ers’ contacts: in two cases, we took the samples where we 
macroscopically noticed in the profile a clear contact be-
tween two layers, a major difference in rock compaction, 
a difference in porosity, and a difference in the degree 
of weathering of the rock. In one case, we took samples 
where we likewise noticed a clear contact between two 
layers, but the rock was macroscopically the same, i.e., 
the compaction of both layers, their porosity and degree 
of weathering were similar.
From 10 rock samples, 17 microscopic thin sections 
were prepared and examined by transmitted light. Prior 
to the microscopic examination, half of each sample was 
dyed with alizarin red dye (1,2-dihydroxyanthraquinone, 
known also as Mordant Red 11; Evamy & Sherman, 
1962). Combining the observations with the results of 
the complexometric titration analysis, we were able to 
determine the properties of the rock.
In the Farafra region we took several samples; here 
we present 3 samples out of the 6 we took in Old White 
Desert.
All samples were ground and dried at 105 °C for 24 
hours followed by cooling in a desiccator for 30 minutes 
prior to weighing (Table 1). We performed 6 complexo-
metric titration analyses on 6 rock samples. We used two 
reference methods, determination of calcium oxide by 
EGTA and determination of magnesium oxide by DCTA 
(CEN, 2013). Both methods use photometric determina-
tion. Visual observation was performed. The indicator 
methylthymol blue changes color from pale green to pink 
in the case of calcium oxide, and from blue to gray in the 
case of magnesium oxide.
2. ROCK RELIEF OF RESISTANT CARBONATE ROCK LAYERS  
SUBJECT TO DISSOLUTION BY WATER IN THE WADIS OF QARA AND TRACES  
OF EOLIAN EROSION
2.1. QARA AREA
The Qara Oasis is located on the western edge of the Qat-
tara Depression (Farouk et al., 2010), south of the city of 
Marsa Matrouh by about 198 km, and northeast of the 
Siwa Depression by 120 km (Figures 4, 5).
The topography of the Qara appears as an asymmet-
ric depression, the eastern bottom of which is lower than 
its western parts.
The length of the depression from north to south 
is about 7.5 km, from east to west about 5.4 km, and its 
MARTIN KNEZ, TADEJ SLABE, MAGDY TORAB & NOURA FAYAD
Figure 3: White desert.
ACTA CARSOLOGICA 52/2-3 – 2023200
total area is about 45.7 km². The western edge of the de-
pression formed in the Middle Miocene carbonates (the 
Marmarica Formation; Figure 6) ranges between 5 me-
ters in the north and 15 meters in the south a.s.l.; its east-
ern edge ranges between 32 meters in the north and 5 
meters in the south. The deepest parts of the depression 
reach a level of 60 meters in the northeastern outskirts of 
the lake, where there are springs and wells (Farouk et al., 
2010; Zaki et al., 2013).
The Qara consists of a depression that was carved 
into the carbonate rocks of Middle Miocene age during 
the Quaternary by several geomorphological factors:
1. The action of karst dissolving during humid periods 
of the Quaternary;
2. Mechanical weathering activity during dry periods 
that led to the destruction of some landforms at the 
rock joints in particular;
3. The prevailing action of ablation by wind during 
the current drought periods and the transfer of 
weathered materials and sediments, which helped 
deepen the depression (Farouk et al., 2010; Zaki et 
al., 2013).
Despite the low rainfall, the surface rock relief, es-
pecially of the wadis and smaller caves, shows traces of 
water flow. The reason for that is the occasional heavier 
rainfall events. 
A continuous denudational lowering of the surface 
of the area occurred through the action of ancient karst 
dissolution during the rainy periods of the Quaternary (El 
Awady et al., 2018). Moreover, the action of weathering 
KARST ROCK RELIEF OF QARA AND WHITE DESERT (WESTERN DESERT OF EGYPT) 
Figure 4: Location of the Qara 
Oasis and White Desert (West-
ern Egypt’s Desert) (Google Maps, 
2023). 
Figure 5: Qara Oasis on the West-
ern Edge of the Qattara Depression 
(Google Maps, 2023).
ACTA CARSOLOGICA 52/2-3 – 2023 201
processes and wind denudation helped erode the rocks of 
the area, leaving a group of scattered limestone hills that 
are gradually eroding due to the processes of weathering 
and wind sculpting during the current drought periods.
The geomorphological features in the Umm al-Sa-
ghir region can be divided into two types. Geomorpho-
logical features that were formed during the current dry 
periods and include the remaining limestone hills, such 
as the conical, domed, flat-topped, double-topped, oval, 
and mushrooms hills that spread out over the plains sur-
rounding Lake Umm al-Sagheer and its marshes. There 
are also a number of wadis that cut the rocky edges 
surrounding the depression, especially from the west-
ern edge, which consists of Miocene limestones (the 
Marmarica Formation). The lowest parts of the depres-
sion are occupied by Lake Qara Umm al-Saghir, which 
derives its water from the hot springs that surround it, 
especially from the western side, where the water seeps 
towards the lowest parts of the region. On the shores of 
the lake, barriers and hooks have formed through the 
action of waves and the wind movement of sand grains. 
Sand grains gather around the assemblages of dry desert 
plants. Spread around the shores of the lake are the flats 
of Lake Sabkha, which dry up completely in the summer 
and a thin salt crust appears on them, mixed with sand 
and silt grains (El Awady et al., 2018; Farouk et al., 2010; 
Khalil et al., 2021; Thabet et al., 2013).
The second type of geomorphological features is the 
forms created during past rainy periods, the most impor-
tant of which are karst caves, most of which were affected 
by mechanical and chemical weathering processes, and 
the roofs of some of them have collapsed. It has been 
noted that the caves were formed by the effect of rainwa-
ter intrusion through the limestones of the Moghra and 
Marmarica formations, in addition to the influence of 
the geological weakness lines, especially the rock joints 
(Farouk et al., 2010). Smaller horizontal caves form un-
der the hardened limestone crust at heights not exceed-
ing one meter. The majority of such caves are found in 
the remaining limestone hills.
The annual average rainfall in Marsa Matrouh is 150 
ml, and in Siwa only 50 ml. By calculating the distance 
between Umm al-Saghir and these two cities, it has been 
concluded that the annual average rainfall in Umm al-
Saghir’s neighborhood is about 75 ml (https://www.me-
teoblue.com) and maximum daily rainfall 28 mm, which 
is result of the Mediterranean climate.
2.2. GEOLOGY
At the fold of the stepped wall terrain, between the level 
of the central village and the top of the tens of meters 
tall step, the beds pinch out towards the south, forming 
a gentle incline that generally dips from the north to the 
south by 10 to 20°.
The diversely composed beds in some places con-
tinuously transition from one to the other, or the lateral 
MARTIN KNEZ, TADEJ SLABE, MAGDY TORAB & NOURA FAYAD
Figure 6: Cut of the geological map 
of Egypt, Siwa, 1:500.000 (Coy 
H.S.C., 1986).
ACTA CARSOLOGICA 52/2-3 – 2023202
contacts between different beds have been obscured by 
the clasts of the upper layers. In places, either laterally 
or in the direction of the geologic column, the contacts 
between two beds of different textures and structures are 
more visible.
The outer edges of beds that outcrop into a stepped 
wall, where we can see their entire thickness in the 
stepped profile, are not vertical, but semicircularly 
rounded up the stepped incline. 
The contacts between beds of different structures 
and textures, where we took rock samples directly below 
and directly above the contact, as described below, are 
not the kind of contacts where the upper layer is located 
on the surface over a larger area, thus fully exposed to 
the atmosphere, and where, conversely, the bottom layer 
is covered by the upper layer and thus protected against 
the impact of the atmosphere and karstification. Owing 
to the stepped beds making up the wall, we keep seeing 
new layers, from one meter to several meters apart, as 
we walk up the slope; therefore, all the parts of the beds 
that are not covered with younger layers, are evenly ex-
posed to atmospheric impact. However, certain beds are 
much more susceptible to weathering and karstification 
due to the loosely bound particles and higher porosity; 
these disintegrate more quickly into the predominantly 
original clasts, as they were before binding into a rock.
According to the geological map (Coy H.S.C., 1986; 
El Sisi et al., 2002), the wider area of the Siwa Oasis be-
longs to the Upper Eocene, to the Moghra Formation. 
The Moghra Formation consists of a continental to shal-
low marine clastic sequence including shale and white 
sandy carbonate beds, which are in some parts abundant 
with silicified wood. The uppermost carbonate layers 
transition to the Marmarica Formation which consists 
of fossiliferous shallow marine platform limestones with 
few marly intercalations.
2.2.1. MACROSCOPIC DESCRIPTION
Contact 1. The bottom layer (sample EGQ1, Table 1) is 
made up of very pale orange (10 YR 8/2; Munsell Rock-
Color Chart, 2009) calcarenite, which is hard and com-
pact within the layer; the clasts are tightly bound together 
(Figure 7a). However, on the surface it intensely disinte-
grates into the basic particles; hence, the somewhat hard 
KARST ROCK RELIEF OF QARA AND WHITE DESERT (WESTERN DESERT OF EGYPT) 
Figure 7: (a) Rock slice prepared for a thin section, sample EGQ1. Width of view is 4 cm, (b) Rock slice prepared for a thin section, sample 
EGQ2. Width of view is 4 cm, (c) Thin section of sample EGQ1. Lower half of sample was dyed in alizarin red dye. Width of view is 4 cm, 
(d) Thin section of sample EGQ2. Lower half of sample was dyed in alizarin red dye. Width of view is 4 cm. 
ACTA CARSOLOGICA 52/2-3 – 2023 203
layer in the area of the stepped wall, which is denuded 
and exposed to the atmosphere because of the inclined 
surface, transitions or re-disintegrates into fine-grained 
particles. Most of the grains in the rock are inorganic 
carbonate grains, mostly measuring around 1 mm in 
diameter. The rock particles are mostly spherical and 
either rounded or angular.
Visible among the grains are larger reflective crys-
tal surfaces. We can rarely see several mm large pieces 
of unidentifiable fossil fragments in the rock, most like-
ly molluscan. No cracks, calcite veins or other micro-
tectonic characteristics are visible in the bed. Moreover, 
no diagenetic alteration is visible, however, we can see 
initial stages of binding and compaction. The fabric of 
sedimentary rock is very porous and has a great abil-
ity to transmit water. The upper layer (sample EGQ2, 
Table 1) differs greatly from the bottom one; it is com-
posed of a darker (light gray, N7), more coarse-grained 
and much harder calcarenite (Figure 7b). The clasts in 
the rock measure up to a few mm in diameter and are 
more tightly bound together than in sample EGQ1. The 
grains in the rock are inorganic carbonate grains, mostly 
measuring a few mm in diameter, and angular. No fos-
sil remains, cracks, calcite veins or other microtectonic 
characteristics are visible. The voids between the clasts 
have a higher cement content; there are fewer voids but 
they are larger (with a diameter of up to 10 mm) than 
in sample EGQ1. The rock is more resistant to weather-
ing and atmospheric impact than the underlying layer. 
Rock porosity and the ability of water transmittance are 
much lower than in the underlying layer. 
Contact 2. Contact 2 has similar characteristics 
as contact 1: less porous and more tightly bound clasts 
in the upper layer, and more porous and more loosely 
bound clasts in the bottom layer. The bottom layer of 
the pale yellowish orange (10 YR 8/6) calcarenite (sam-
ple EGQ3, Table 1) is rather hard and compact on the 
inside, but on the surface, and under the influence of 
the atmosphere, it disintegrates into the basic particles. 
In the rock we can observe mostly inorganic carbonate 
grains of varying sizes, from already weathered ones, 
smaller than 1 mm, to unweathered ones, measuring 
up to 1 cm in diameter. The rock particles are mostly 
prismatic and angular; some of them are also partially 
rounded and bladelike. Also visible in the rock are fossil 
fragments, some over 2 mm large, most likely from the 
Nummulitidae family and the bivalves group. No cracks, 
calcite or other microtectonic characteristics are visible 
in the bed; however, we can see initial stages of bind-
ing and compaction. The rock is very porous and has 
a smaller ability to transmit water than sample EGQ1. 
The upper layer of contact 2 consists of a lighter (gray-
ish yellow, 5 Y 8/4), more coarse-grained, more com-
pact and harder calcarenite (sample EGQ4, Table 1), 
which is more resistant to weathering and atmospheric 
impact than the calcarenite in the underlying layer. The 
clasts in the rock measure from 0.5 cm to several cm 
in diameter. They are more tightly bound together than 
in sample EGQ3. The content of inorganic angular car-
bonate grains, with an average diameter of half a cm, in 
the rock has been estimated to roughly half; the other 
half comprises fossil remains from the Nummulitidae 
family and the bivalves group. There are a few empty 
spaces in the rock, measuring up to 1 cm3. Due to larger 
clasts oriented parallel, mostly bioclasts, the bed has a 
slate-like appearance in some places. Rock porosity and 
water absorption ability are lower than in the underly-
ing layer.
Contact 3 is between two very similar layers of a 
fine-grained calcarenite; the bottom sample EGQ5 (Ta-
ble 1), which is a pale yellowish orange color (10 YR 
8/6), and the top sample EGQ6 (Table 1) of a grayish 
orange color (10 YR 7/4). The clasts in the rock, most 
of which do not exceed a few mm in size, are tightly 
bound; both rocks are quite hard and compact. No fossil 
remains are visible; only perhaps tiny fragments of the 
Nummulitidae family and the bivalves group here and 
there. No cracks, calcite or other microtectonic char-
acteristics are visible in these two layers; however, we 
can see the initial stage of compaction. Both rocks are 
very porous, though without any larger voids; they have 
a high ability of water absorption and a low ability of 
water transmittance.
2.2.2. MICROSCOPIC DESCRIPTION
Contact 1. On account of the loosely bound particles in 
the rock and the macroscopically determined high po-
rosity, we hardened sample EGQ1 with Araldite before 
making the thin section. A major difference in the com-
position of both rocks at the contact is also visible in 
the microscope slides. The bottom layer (sample EGQ1, 
Figure 7c) is made up of micritized carbonate intra-
clasts with diameters from 0.5 to 1 mm, and of mostly 
up to 2 mm longitudinally elongated bioclasts (mainly 
algae) and numerous fragments of various bioclasts. 
There is virtually no cement; only exceptionally do we 
see druzy calcite spar among the rock clasts. The intra-
clasts and bioclasts are carbonate, while some of the 
micritized clasts are of non-carbonate origin, namely in 
the places where we were unable to determine staining 
with alizarin and based on the complexometric titration 
analyses. A high percentage of the dolomite belongs to 
bioclasts. Mechanical compaction is well visible in the 
rock on the damaged larger elongated bioclasts. Re-
gardless, the porosity of the rock, which can be classi-
fied as rudstone, is very high, estimated at a minimum 
MARTIN KNEZ, TADEJ SLABE, MAGDY TORAB & NOURA FAYAD
ACTA CARSOLOGICA 52/2-3 – 2023204
of 70%. The upper layer (sample EGQ2, Figure 7d) is 
made up of intraclasts, mostly measuring from 45 µm 
to 0.5 mm in diameter, exceptionally up to 1 mm. No 
bioclasts are visible in the rock; however, there are a few 
peloids. The clasts are tightly bound together with mi-
crosparite and druzy calcite spar cement. The crystals of 
the druzy calcite spar cement, with diameters between 
45 and 200 µm, are well visible on the inside of the nu-
merous fenestrae. The latter are partially and, in some 
places, fully filled with druzy calcite spar. The fenestrae 
that are not fully filled have diameters between 0.1 and 
2 mm, but mostly around 0.7 mm. The porosity of the 
carbonate rock of the grainstone or packstone type has 
been estimated at about 5 to 10%.
Contact 2. Here too, on account of the loosely bound 
particles in the rock, we hardened the bottom layer with 
Araldite before making the thin section. Very similar dif-
ferences in the composition of both rocks, as described 
in the case of contact 1, are also visible in the microscope 
slides of contact 2. The bottom layer (sample EGQ3) is 
made up of carbonate intraclasts and many larger bio-
clasts. Some of the intraclasts are smaller, with diam-
eters up to 0.1 mm; a small number of them are larger 
and of irregular shapes, with diameters up to 1.4 mm. 
The majority of bioclasts, which represent the dolomite 
part of the rock (some reaching over 4.5 mm in the lon-
gitudinal direction), belong to the Nummulitidae family 
and algae. The cement laterally and seemingly randomly 
transitions from micrite to sparite, taking up about 20% 
of the rock. Alizarin did not stain the dark fine-grained 
cement in many places; we therefore assume that a part of 
the cement is non-carbonate and makes up the insoluble 
residue. No major traces of compaction are visible. The 
porosity of the grainstone- or packstone-type rock has 
been estimated at about 60 to 70%. The upper layer (sam-
ple EGQ4) is likewise made up of intraclasts and some 
extraclasts, both of which are mostly micritized, and of 
bioclasts. The intraclasts and extraclasts are larger in size, 
with an average diameter between 0.9 and 1.8 mm, and 
are tightly cemented together. The cement is micrite and 
sparite. Mechanical compaction is well visible. Most of 
the bioclasts from the Nummulitidae family, as well as 
the algae and corals, are broken and their pieces have 
been displaced, in some places by 0.5 mm. Much like in 
contact 1, porosity is lower in the upper layer and has 
been estimated at about 15 to 20%.
Both layers of contact 3 are almost identical, both 
in the macroscopic and microscopic view. They are made 
up of intraclasts of different sizes, ranging from 0.1 mm 
to 0.6 mm; most of them measure around 0.3 mm in di-
ameter. There are no bioclasts in the layers. The cement 
is sparite and micrite, in some areas laterally dolomite, 
and of non-carbonate origin. Compared to the previous 
layers, the rock is highly compacted. Porosity has been 
estimated at 10 to 15%.
2.2.3. COMPLEXOMETRIC TITRATION ANALYSES
The samples of contact 1 are almost entirely carbonate, 
with a total carbonate content between 91 and 94% (Table 
1). The bottom layer contains a slightly higher amount of 
insoluble residue than the upper layer. A major difference 
between both layers is the calcite-dolomite ratio. Where-
as over 50% of the rock underneath the contact is made 
up of calcite and as much as 40% of dolomite, almost 90% 
of the rock above the contact is made up of calcite.
The samples of contact 2 have a slightly lower to-
tal carbonate content, with the bottom layer contain-
ing just under 83% and the upper layer almost 90%. 
KARST ROCK RELIEF OF QARA AND WHITE DESERT (WESTERN DESERT OF EGYPT) 
Table 1: Complexometric analyses of rock samples (granulation < 0.25 mm, dried 24h at 105 °C); samples from Qara (EGQ1 to RGQ6) and 
samples from White Desert (EGF21 to EGF23).
Laboratory 
designation of 
the sample
Rock 
sample
CaO  
(%)
MgO  
(%)
Calcite  
(%)
Dolomite  
(%)
CaO/
MgO
Total carbonate 
(%)
Insoluble residue
(%)
V- 53/23 EGQ1 28.65 19.31 51.13 40.39 1.48 91.52 8.48
V- 54/23 EGQ2 49.92 2.03 89.10 4.25 24.59 93.35 6.65
V- 55/23 EGQ3 26.38 17.07 47.08 35.71 1.55 82.79 17.21
V- 56/23 EGQ4 30.48 16.75 54.40 35.04 1.82 89.44 10.56
V- 57/23 EGQ5 22.23 15.37 39.68 32.15 1.45 71.83 28.17
V- 58/23 EGQ6 24.41 16.54 43.57 34.60 1.48 78.17 21.83
V- 59/23 EGF21 33.79 17.21 60.31 36.00 1.96 96.31 3.69
V- 60/23 EGF22 53.81 0.99 96.04 2.07 54.35 98.11 1.89
V- 61/23 EGF23 54.10 1.01 96.56 2.11 53.56 98.67 1.33
ACTA CARSOLOGICA 52/2-3 – 2023 205
The bottom layer contains just over 17% of insoluble 
residue, and the upper layer just over 10%. Much like in 
contact 1, the bottom layer has a lower calcite content 
than the upper layer, while both layers have the same 
dolomite content.
The samples of contact 3 are very similar; they have 
a similar total carbonate content, and a similar calcite, 
dolomite and insoluble residue content.
2.3. ROCK RELIEF
Occurring in various sizes, the smaller wadis join the 
bigger ones in dendritic patterns, occasionally – when 
smaller wadis drain into the larger ones from the flank – 
creating steep parts of water bed.
Distinct rock features, which came about due to the 
dissolution of the rock, can be made out in the harder 
(e.g., samples EGQ2, EGQ4), more resistant and more 
calcite-rich rocks, and in the contact with the less resis-
tant carbonate rocks (e.g., samples EGQ1, EGQ3) which 
disintegrate into very fine, original particles (Figure 8). 
Their different compositions (with varying sizes of clasts 
and degrees of porosity) are also reflected in the rock re-
lief. Fossils are also visible (Figure 9a). Such rock strati-
fication can occur in repetitive sequences, where harder 
layers with traces of dissolution and the disintegrating 
layers overlying them can be stacked on top of each oth-
er. The more resistant layers are rounded and either pro-
trude from the higher wall or form stepped walls (Figure 
2b), forming the resistant top of the karren. They become 
exposed over time by the action of wind and water. As 
they are more resistant and solid, these layers often end 
up being the wadi’s bed over prolonged periods. Subject 
to periodical water flows in varying amounts, the rock 
relief shows traces of sand being carried to and away, of 
being covered and then exposed again. 
Subsediment rock features are formed as water per-
MARTIN KNEZ, TADEJ SLABE, MAGDY TORAB & NOURA FAYAD
Figure 8: Rock relief of the wadi. a. subsediment cup, b. subsediment rock pillar, c. large solitary rocks, d. half-cup notches, e. half-cup 
notches, f. subsedimentary channels, g. small half-bell, h. smaller and bigger steps, i. subsediment steps, j. larger channels, k. channels.
ACTA CARSOLOGICA 52/2-3 – 2023206
colates through the detritus of the upper disintegrating 
layer, thereby dissolving the lower layer, and on sloping 
surfaces as water is drained away. Various subsediment 
cups are formed on horizontal or gently sloping surfaces, 
whereas subsediment channels are formed on inclined 
surfaces. 
On the rock, which is covered with sand in places, 
subsediment cups are formed, sometimes next to each 
other (Figures 8a, 9b), and subsediment channels with a 
diameter ranging from 10 cm to several meters and with 
small stone pillars between them. This applies to the up-
per parts of the karren. In sandier rock layers, there are 
irregularly shaped subsediment cups with outstanding 
ragged edges (Figure 9c), which are either the result of 
the dissolution and consolidation of the sandy carbon-
ate rock or of the frequent, partial or complete, covering 
and exposing of the surface. Under the same conditions, 
a surface which is composed of less resistant, sandier 
rock, and is slightly more soluble, will become dissected 
by tiny, centimeter-sized cups (Figure 9d). Such surfaces 
also contain larger subsediment cups. Such cups also 
form beneath the steep sections of cliffs, with channels 
leading down to them. Sand is deposited in them by wa-
ter and wind, and the rock underneath dissolves more 
efficiently and over longer periods. Between them, small 
subsediment rock pillars form. In some places, they make 
up veritable stone forests (Figures 8b, 9e) with ten-centi-
meter-tall pillars that take a mushroom shape, provided 
that their top layers are more resistant to corrosion and 
erosion. They protrude from the mainly sand-covered 
surface.
They are a common feature of the wadi’s banks that 
divert water to the bottom, which we will proceed to de-
scribe below. Large solitary rocks (Figures 8c, 9f) stand 
out between, and sometimes within, the relatively dense 
network of smaller and shallower wadis.
At the end of the layer which terminates in a stepped 
wall are the uniquely shaped tops of rock steps (Figure 
9g). Below the step, a subsediment longitudinal notch 
has formed, which is dissected by half-cup notches on 
the outflow side (Figures 8d, 8e, 9g). They catch water 
from the sand that covers the notch. The largest channels 
are also, at least periodically, subsedimentary (Figures 
8f, 9h) as their bottom is covered by sand. Also formed 
subsedimentary are the mouths of channels which drain 
away the water coming down the step (Figure 9g); the 
water runs down the channels in the steep part of the 
wall between the ledges (Figure 9i). As a result, funnel-
like notches have also formed on the occasionally sand-
covered top edge of the rock ledge (Figure 9j). There are 
also small half-bells in the lower part of the steeper wall 
sections, which are occasionally covered by sand (Figures 
8g, 9k). Channels also form on overhanging sections un-
der the disintegrating layer that extends to the edge of 
the wall. This is also true of the rock relief of the steep 
parts in the bed. A semicircular longitudinal notch may 
also form at the lower sections of steep edges (Figures 8d, 
9l). Some channels (Figure 9m) that have formed under 
small springs between rock layers are also subsedimen-
tary. 
Smaller and bigger steps (Figure 8h) have also 
formed on the sloping surface as a result of the water 
creeping down the surface, carrying and depositing sand. 
Underneath, dissolution occurs slightly faster and over 
extended periods (Figure 9n). A step has also formed at 
the contact of the upper, harder layer, which dissolves 
more slowly, and which covers and protects the slight-
ly less resistant lower layer (Figure 9o). A channel has 
formed in its wall, leading to a subsediment cup in the 
lower layer.
At the bottom of the shallow wadis, in which sand 
is transported by water and partly wind, and which are 
usually sand-covered in places, a typical rock relief can 
be made out (Figure 9p). It is dominated by large (with 
a diameter of up to one meter) half-cup notches, which 
are semicircular in shape on the inflow side and open 
on the outflow side. In many instances, they occur in 
tiers, one on top of the other (Figures 9p, 9q). There are 
also larger (meter-sized) subsediment steps (Figures 8i, 
9r) which are occasionally bare and feature steep inflow 
edges. On the lower part of the steep edges, subsediment 
longitudinal notches (Figures 9r, 9s) form at the bottom 
of the bed or the banks, which are traces of the frequent 
changes in the level of sand that covers the bottom of 
the wadi. In the lowest parts of the bed, larger channels 
(Figures 8j, 9t) have formed, which also develop from or 
at the bottom of subsediment cups (Figure 9u). The bot-
tom of the wadi is often completely covered or exposed 
to varying degrees. Water also runs in from the sides 
(Figures 8k, 9v), as is noticeable in the rock forms (Fig-
ures 8k, 9w). The rocky wadi bottom is also eroded and 
reshaped by the water and the sand it carries. The most 
exposed parts are therefore relatively smooth and dis-
sected by shallow cups (Figure 9x). Here, the small rock 
protrusions that characterize the banks of the wadis and 
the higher parts of the karren described above are not 
present. Only larger protrusions (Figure 9y, center) can 
be seen. 
On the bare rock, especially in the steeper sections, 
channels have formed that drain water from the layers, 
which break up into sand (Figure 9z), and the bedding 
plane caves. There are also cases where the water creep-
ing down the bare rock forms channels. On the gently 
sloping sections, these are partly or periodically covered 
with sand. 
The overhanging parts of the higher walls are dis-
KARST ROCK RELIEF OF QARA AND WHITE DESERT (WESTERN DESERT OF EGYPT) 
ACTA CARSOLOGICA 52/2-3 – 2023 207
MARTIN KNEZ, TADEJ SLABE, MAGDY TORAB & NOURA FAYAD
ACTA CARSOLOGICA 52/2-3 – 2023208
sected by tiny cups, a few centimeters in diameter, which 
connect into a network. They appear to be of subsedi-
ment origin, some of them partially infilled and covered 
by a crust of solidified solution overlying the lower, oc-
casionally covered, overhanging parts of the wall (Fig-
ure 10a). Located above them are wider wall channels 
(Figure 10a), also subsedimentary judging from their 
form, which were later reshaped by creeping water. 
Above ground, however, large longitudinal notches have 
formed, most of them longitudinally cup-shaped (Figure 
10b), which can be traced to the steady levels of sand sur-
rounding the rock. 
The subsediment bedrock has a relatively smooth 
surface, whereas the upper parts of the mostly bare rock, 
which are only occasionally covered with fine sand, are 
coarse, depending on the composition of the rock (Fig-
ure 10c). 
The karren are most prominently perforated along 
the bedding planes (Figures 2d, 2e). The smallest cavities 
have a diameter of about one centimeter (Figure 10e). 
Typically, the caves are relatively wide (several meters) 
and low (Figure 10f). 
Only the largest old caves (Fig. 11) are accessible. 
In some places, more pronounced central pipes have 
formed, which might occur as ceiling channels where the 
ceiling is made up of a more highly soluble rock. Con-
versely, a bottom channel is formed if the water cuts into 
less resistant rock overlain by a more resistant layer. In 
some places there are springs of water on the edges of 
the rock walls, and underneath them epiphreatic caves. 
KARST ROCK RELIEF OF QARA AND WHITE DESERT (WESTERN DESERT OF EGYPT) 
Figure 9: (a) Fossil in the rock. Width of view is 45 cm, (b) Subsediment cups. Width of view is 3.5 m, (c) Subsediment cup with a higher 
edge. Width of view is 1 m, (d) Small subsediment cups. Width of view is 25 cm, (e) Small rock pillars, (f) Rock pillar. Width of view is 
5 m, (g) Stepped wall at the end of the wadi, (h) Subsediment channel. Width of view is 3 m, (i) Subsediment funnel-like notches and 
channels. Width of view is 7 m, (j) Subsediment funnel-like notch. Width of view is 1.5 m, (k) Subsediment half-bell. Width of view is 
1.5 m, (l) Longitudinal subsediment notch, (m) Channel under a small spring. Width of view is 1.5 m, (n) Small steps on the steep wall. 
Width of view is 6.5 m, (o) Longitudinal notch between the less resistant and more resistant rock layer. Figure 9p: Half-cup notch, (q) 
Half-cup notches in a tier. Width of view is 5 m, (r) Large subsediment steps. Width of view is 7 m, (s) Longitudinal subsediment notch, 
(t) Large channel on the bottom of the wadi. Width of view is 7 m, (u) Subsediment cups and channel. Width of view is 6 m, (v) Traces 
of water flowing from the sides of the wadi. Width of view is 25 m, (w) Traces of water flowing from the sides of the wadi, (x) The most 
exposed parts of the wadi bottom with shallow cups, (y) The most exposed parts of the wadi bottom with shallow cups and a large pro-
trusion, (z) Channels on the rock edge. 
ACTA CARSOLOGICA 52/2-3 – 2023 209
MARTIN KNEZ, TADEJ SLABE, MAGDY TORAB & NOURA FAYAD
Water flowing out of the bedding-plane recent forming 
caves carves out channels in the wall through different lay-
ers of rock, including those that quickly disintegrate on the 
surface. 
In Qara the sandy, less cohesive and thus less re-
sistant rocks are eroded by the wind. This results in 
rounded surfaces and the formation of longitudinal 
notches next to them, which are dissected by large and 
shallow (several tens of centimeters or a meter or more 
across) wind scallops (Figure 10d). Their surface is fur-
ther dissected into small cups (Figure 9r), which are 
largely linked to porous layers and narrower notches, 
weak spots in the structure and the fissuring of the rock, 
and into smaller protrusions which are in fact parts of 
a more resistant rock. Longitudinal notches also form 
along the contact within the layers. The rock disinte-
grates into sand, which is picked up by the wind and 
deposited on the karst surface.
Figure 10: (a) Overhanging wall with channels. Width of view is 4 m, (b) Overhanging wall with a longitudinal notch and large cups, (c) 
Trace of rock composition on its surface. Width of view is 30 cm, (d) Wind scallops. Width of view is 8 m, (e) Small hollows. Width of view 
is 5 m, (f) Small caves along bedding planes. Width of view is 7 m.
Figure 11: Entrance into the cave.
ACTA CARSOLOGICA 52/2-3 – 2023210
KARST ROCK RELIEF OF QARA AND WHITE DESERT (WESTERN DESERT OF EGYPT) 
3. EOLIAN EROSION IN THE KARST OF THE WHITE DESERT IN FARAFRA
3.1. WHITE DESERT, FARAFRA
The floor of the depression (Figure 3) exposes a large 
expanse of flat-lying Cenomanian fluvial sandstones. 
Around the margins these pass upwards into the terres-
trial to marine transitional clastic beds well known for 
their vertebrate fauna (Slaughter & Thurmond, 1974; 
Stromer, 1936). This is followed by a carbonate bed 
called the El Heiz Bed (Said, 1990). Above this, a mixed 
lithological section of dolomites and clastics, the Hefhuf 
Formation, can be traced around much of the rim of 
the depression, but is absent in the part of the northern 
area where pre-Middle Eocene erosion has breached 
the crest of the dome down to the Cenomanian clas-
tics. Maastrichtian to Danian age chalky limestone or 
Farafra chalk (Coy H.S.C., 1987; Issawi, 1972; Plyusnina 
et al., 2016) is present in the southwest from the oasis 
below the Eocene carbonates.
In the area of Farafra rainfall amounts to merely 
11.8 mm (El-Marsafawy et al., 2019).
3.2. GEOLOGY
We took several samples of rock in the area of Crystal 
Mt., Aqaba, and Old and New White Deserts (all lo-
cations are up to a few tens of km northeast from the 
Farafra Oasis). Presented below are three samples out 
of the six we took in Old White Desert: a sandstone 
sample and two chalk samples. On the geological map 
(Coy H.S.C., 1987) the rock is shown as white massive 
neritic chalk and chalky limestone (the Khoman For-
mation) which interfingers with submarine fan deposits 
of yellowish carbonate-bound siltstone and sandstone 
intercalated with clay, known as the Dakhla Formation.
3.2.1. MACROSCOPIC DESCRIPTION
The depressions between the smaller rocky hills consist 
of a brown ochre (10 YR 6/6 and 10 YR 5/4; Munsell 
Rock-Color Chart, 2009) sandstone (sample EGF21; 
Table 1). The sandstone is carbonate, which we were 
surprised to discover after performing an acid test; it is 
fine-grained and many particles with a smooth, reflect-
ing plane are visible on its surface. On the broken sur-
faces we can feel that the grains are angular. The rock is 
completely homogeneous, consisting of macroscopical-
ly identical grains; no gradation is visible in the profiles, 
the rock is uniform and hard: the particles are tightly 
bound together. No porosity was visible macroscopi-
cally; we noticed considerable porosity only after ex-
amining the rock with a field magnifier and later, when 
processing the samples in the laboratory. Exceptionally, 
we see intercalations in the rock – spherical sinsedi-
mentary white and carbonate and brownish-red non-
carbonate intraclasts, mostly measuring up to a few cm 
in diameter, which are believed to have originated from 
iron-rich paleosol (ferricrete) horizons (Catuneanu et 
al., 2006).
In some places on the eroded rock surface, 
smoothed by eolian erosion, there are many dissolved/
broken-off non-carbonate reddish-brown clasts, most 
likely also due to the weathered younger layers, which 
have been carried away by the wind.
The small rocky hills, located next to each other 
in some places or alone on a plain at the edge of such 
groups, are composed of pure white fine-grained car-
bonates (white, N9); the rock is chalk (samples EGF22, 
EGF23, Table 1). There are hardly any larger clasts vis-
ible on the surface of the rock; only exceptionally are 
there fragments of various bioclasts, mostly measuring 
up to 10 mm in diameter, distributed across horizons, 
several meters thick. In these horizons we notice differ-
ent bivalves (Figure 12) here and there; in many places, 
they protrude from the rock by several cm. The contacts 
between the sandstones that make up the depressions 
and between the chalk that makes up the small rocky 
hills are mostly obscured by the sand from the weath-
ered sandstone. 
3.2.2. MICROSCOPIC DESCRIPTION
Due to the loosely bound particles in the rock, we 
hardened all the samples with Araldite before making 
the thin section. The brown ochre sandstone (sample 
EGF21) is composed entirely of almost equal-sized car-
bonate grains of calcite and dolomite. Individual sec-
tions of the rock can be identified as having a dolomite 
mosaic idiotopic texture with euhedral unimodal crys-
tals. The average grain size is between 0.2 and 0.3 mm; 
only individual grains reach a diameter of 0.5 mm. The 
grains touch and overlap; cement that would addition-
ally bind individual clasts together is not visible. Most 
of the grains are heavily micritized. There is no visible 
compaction; the grains are not damaged, nor in any way 
deformed. There are no bioclasts or other types of clasts 
in the rock. Porosity is typically 
intergranular. Individual voids in the rock gener-
ally do not exceed 0.5 mm; some of the larger ones have 
diameters up to 0.9 mm, and the smaller ones between 
0.1 and 0.2 mm. The total porosity of the grainstone-
type rock has been estimated at 15 to 20%. The white 
chalk (samples EGF22 and EGF23) consists of tiny mi-
crite, microsparite and sparite clasts, mostly measuring 
around 45 µm in diameter. Also very numerous are the 
ACTA CARSOLOGICA 52/2-3 – 2023 211
MARTIN KNEZ, TADEJ SLABE, MAGDY TORAB & NOURA FAYAD
bioclasts represented by different species of planktonic 
foraminifera, mostly of the Globigerina genus, taking 
up at least 50% of the volume of the rock, which can 
best be described as biomicrite to biosparite. There is 
no visible compaction in the rock. Intergranular and es-
pecially intragranular porosity are well visible, together 
estimated at about 30%. 
3.2.3. COMPLEXOMETRIC TITRATION 
ANALYSES
We performed 3 complexometric titration analyses 
(Table 1), according to which more than half of the 
sandstone in the rock (sample EGF21) is composed of 
calcite and a good third of dolomite. Due to the heavy 
micritization of most grains, which usually do not ex-
ceed 0.3 mm, alizarin red dye is difficult to distinguish 
in individual mineral grains in many places. Insoluble 
residue makes up just under 4%. The chalk rock (sam-
ples EGF22 and EGF23) contains over 96% of calcite, a 
good two percent of dolomite, and less than 2% of in-
soluble residue.
3.3. ROCK RELIEF
Eolian rock features are predominant in the rock relief 
of the White Desert near Farafra (Figures 13, 14, 15). 
They are therefore clearly visible in the soft layers of 
chalk, which are being dissected into the characteristic 
forms of the karst surface, as they are denuded of the 
harder layers of sandstone that are disintegrating into 
sand. The wind whirls this sand around and thus me-
chanically sculpts the rock features. The geomorpho-
logical classification of the karst surface of the Bahariya 
and Farafra area divides it into sixteen different types 
and defines their development (El Aref et al., 2017). 
The largest eolian rock features, reaching several 
meters in size, are: wall niches (Figure 16a); longitudi-
nal notches above the ground; the wall (Figure 16b) and 
bottom channels (Figure 16c), which have developed 
into genuine wind gorges in some places (Figure 16d) 
that dissect the hills. The former are characteristic of the 
windward slopes of hills, while the latter cut through 
the hills. Due to their size, rock features are generally 
dissected by smaller niches, while gorges are dissected 
by large niches (Figure 16a); yet all of them are also dis-
sected by wind scallops. The large niches higher above 
the ground are dissected by bottom channels, while 
their tops are dissected by ceiling channels, which in-
dicate air flowing through the niches. The walls are dis-
sected by large and small cups and channels (Figure 
16d), which were formed by eolian erosion between the 
harder crusts overlying them.
The wind scallops are of different sizes, from me-
ter-sized (Figures 16a, 16d) to decimeter- and centime-
ter-sized. Sometimes the smaller ones dissect the larger 
ones and are often connected into a channel (Figure 
16e) or a leeward funnel (Figure 16f). The network of 
scallops clearly reveals the prevailing wind direction 
(Figure 16g). 
On the ground, which is being denuded of the 
harder layer of rock and is occasionally at least part-
ly covered with sand, rock features form in two main 
ways. If a steeper windward edge is formed, i.e., when 
the denuded part of the rock is higher, then a longitudi-
nal notch forms on the edge (Figures 13, 16d) or semi-
Figure 12: Fossil in the rock. Width 
of view is 15 cm. 
ACTA CARSOLOGICA 52/2-3 – 2023212
KARST ROCK RELIEF OF QARA AND WHITE DESERT (WESTERN DESERT OF EGYPT) 
circular channel-like cups. Sometimes channels cut 
through these protrusions (Figure 16c). It seems that 
at first, when the part of the rock protruding from the 
sand is low, a gently sloping section is formed, contain-
ing shallow channels and wind scallops (Figure 16h), 
and a steeper leeward section. If such areas are vaster 
(Figure 16i), then the surface is more undulating, and 
sand-filled cups can form on the rock.
The rock pillars (Figure 16j) are carved by the sand-
carrying wind out of the parts of the rock which is over-
Figure 13: Hill with wind rock features.
Figure 14: Rock teeth.
ACTA CARSOLOGICA 52/2-3 – 2023 213
MARTIN KNEZ, TADEJ SLABE, MAGDY TORAB & NOURA FAYAD
lain by a harder layer the longest, with the thickness of 
the layer determining their extensiveness, and out of 
larger cones. The tallest pillars are mushroom-shaped, as 
the action of wind and sand is the most intense just above 
the ground, where it forms longitudinal notches. The wa-
ter that flowed down the walls or out of smaller cavities 
(Figure 16k) has caused a crust, typical for this kind of 
rock and climatic conditions, to form on the surface, 
which in turn caused the development of the rock relief. 
The crusted surfaces generally protrude from the walls, 
with wind channels deepening around them (Figure 16l). 
The crust is usually best preserved near the top and also 
covers the surface of vertical channels. In the sections 
where eolian erosion is predominant, only smaller crust-
ed surfaces have been preserved. Cups form in the weak 
sections of the crust and in the sections where the crust 
has not covered the surface. They are being carved out by 
the sand-carrying wind. 
4. CONCLUSION
The rock relief of wadis in Qara is dominated by dissolu-
tion traces made in various carbonate rocks of varying 
resistance. Its subsediment formation is mostly the result 
of the sand created by the unconsolidated disintegrated 
beds transported around by water and wind. Typically, 
it is made up of subsedimentary rock forms; their dis-
tinctive shapes are down to the fact that the sand under 
which they have formed is being constantly transported 
around, i.e., they are being regularly uncovered and cov-
ered. The unique rock relief of wadi beds features rock 
forms that can be attributed to ephemeral sand-carrying 
water streams and the water running down from the 
banks. Steep rock parts of water bed that emerge where 
smaller wadis meet larger ones are also typical. The forms 
that occur on bare rock are less prominent, as they tend 
to be occasionally covered by sand at least to some extent. 
In this way form channels on the steep sections of rock 
walls as well as higher parts of the rock, and rock forms 
that are of subsedimentary design when bare. 
 The sandiest rock beds are co-shaped by water 
and even more prominently by wind. 
In the rock relief of hills, rock cones and pillars, and 
of the rocky ground of the White Desert near Farafra, eo-
lian rock features prevail. An entire range of rock features 
Figure 15: Rock pillar.
ACTA CARSOLOGICA 52/2-3 – 2023214
KARST ROCK RELIEF OF QARA AND WHITE DESERT (WESTERN DESERT OF EGYPT) 
Figure 16: (a) Notch with scallops. Width of view is 20 m, (b) Wall channel. Width of view is 2 m, (c) Floor channels, (d) Wind-shaped 
gorge, (e) Wind scallops connected in channels. Width of view is 2 m, (f) Wind scallops connected in a funnel-like notch. Width of view is 
2 m, (g) Wind scallops on the wall, (h) Wind scallops connected in funnel-like notches and floor channels. Width of view is 8 m, (i) Rock 
floor dissected by wind rock features. Width of view is 6 m, (j) Rock pillars, (k) Wall dissected by cups and covered by crust, (l) Rock relief 
of a pillar. Width of view is 10 m.
can be discerned: from large niches and longitudinal 
notches on the windward side of barriers, channels and 
gorges crossing the rock barriers, to the smaller scallops 
dissecting the surface of the rock. The formation of crust 
on the surface of the rock that is in contact with water 
is also important for the development of the rock relief. 
This crust is a trace of the dissolution and hardening of 
the surface of the rock. At the gaps in the crust, cups are 
being carved into it by the wind. 
The diverse shapes of the rock relief of karst features 
seem to also be affected by the volume of rainfall, which 
is higher in the area of the Qara Oasis, although its distri-
bution and type (e.g., downpour, drizzle) are the decisive 
factor. 
The exposure of the different rock layers provides 
an insight into the distinct evolution of the karren and 
the karst surface over various time periods. There are 
many possibilities for examining the various combina-
tions, however, an intimate knowledge of these phenom-
ena should be the cornerstone for improving our under-
standing of this type of karst formation process. 
ACTA CARSOLOGICA 52/2-3 – 2023 215
MARTIN KNEZ, TADEJ SLABE, MAGDY TORAB & NOURA FAYAD
ACKNOWLEDGEMENTS
The authors acknowledge the financial support from 
the Slovenian Research Agency (research core funding 
No. P6-0119). Research was supported and included in 
the framework of projects “Development of research in-
frastructure for the international competitiveness of the 
Slovenian rri space RI-SI-EPOS” and “Development of 
research infrastructure for the international competi-
tiveness of the slovenian rri space RI-SI- LIFEWATCH”; 
both operations are co-financed by the Republic of Slo-
venia, Ministry of Education, Science and Sport, the Eu-
ropean Union, the UNESCO IGCP project No. 661, and 
the UNESCO Chair on Karst Education.
We wish to thank Mrs. Mojca Škerl for perform-
ing the complexometric analyses at the laboratory of the 
Slovenian National Building and Civil Engineering In-
stitute/Zavod za gradbeništvo Slovenije ZAG, Dimičeva 
ulica 12, Ljubljana, Slovenia.
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