KARREN OF PROVENCE (FRANCE), GRÉOLIÈRES, CAUSSOLS, 
TOURRETTES-SUR-LOUP AND LUBERON
ŠKRAPLJE PROVANSE (FRANCIJA), GRÉOLIÈRES, CAUSSOLS IN 
TOURRETTES-SUR-LOUP TER LUBERON
Martin KNEZ1,2,3, Tadej SLABE1,2,3, & Philippe AUDRA4  
Abstract UDC 551.435.81:552.513(449.1/.43)
Martin Knez, Tadej Slabe & Philippe Audra: Karren of 
Provence (France), Gréolières, Caussols, Tourrettes-sur-Loup 
and Luberon
The rock relief of karst forms, either of surface forms or of caves 
which are forming on different carbonate rocks and under dif-
ferent conditions, is one of the most telling traces of their for-
mation, along with the characteristic factors and development. 
Therefore, we meticulously studied and examined the geologi-
cal features and rock formations, as well as how they fit into the 
rocky relief. The diverse shaping of the karst surface is revealed 
by the rock relief of selected karren on different carbonate 
rocks, fine-grained homogeneous and compact limestones, as 
well as porous fine-grained sandstones. We have also newly ex-
plained the formation of parallel channels on the inclined sur-
faces of denuded rock (Gréolières); the gradual reshaping of the 
rock surface from a subsoil one to one directly exposed to rain 
and water creeping along the gently sloping rock (Caussols). 
Furthermore, the unique shaping of carbonate sandstones, spe-
cifically such with large channels (Tourrettes-sur-Loup) is pre-
sented for the first time. The speed of karstification of younger 
carbonate rocks is revealed by channels on the walls of the pal-
ace in Avignon.
Keywords: carbonate rock, rock relief, complexometry, 
Provence, France.
Izvleček UDK 551.435.81:552.513(449.1/.43)
Martin Knez, Tadej Slabe & Philippe Audra: Škraplje 
Provanse (Francija), Gréolières, Caussols in Tourrettes-sur-
Loup ter Luberon
Skalni relief kraških oblik, površinskih in jam, ki nastajajo na 
različnih karbonatnih kamninah in razmerah, je ena najbolj 
povednih sledi načina njihovega oblikovanja z značilnimi de-
javniki in razvoja. Zato smo natančno preučili in spoznali ge-
ološke značilnosti in skalne oblike ter njihovo povezanost v 
skalni relief. Pestrost oblikovanja kraškega površja razkrivajo 
škraplje na različnih karbonatnih kamninah, drobnozrnatih 
homogenih in kompaktnih apnencih ter poroznih drobnozr-
natih peščenjakih. Na novo razloženo je tudi oblikovanje vzpo-
rednih žlebov na nagnjenjih površinah razgaljene skale (Gré-
olières), razkriva se postopno preoblikovanje skalnega površja 
iz podtalnega v neposredno izpostavljenega dežju in polzeči 
vodi po malo nagnjeni skali (Caussols) ter prav tako na novo je 
predstavljena svojevrstnost oblikovanja karbonatnih peščenja-
kov zlasti z velikimi žlebovi (Tourrettes-sur-Loup). Hitrost za-
krasevanja mlajših karbonatnih kamnin razkrivajo žlebovi na 
zidovih palače v Avignonu.
Ključne besede: karbonatna kamnina, skalni relief, komplek-
sometrija, Provansa, Francija.
ACTA CARSOLOGICA 145-185, 145-185, POSTOJNA 2024
1 ZRC SAZU Karst Research Institute, 6230 Postojna, Slovenia, e-mails: knez@zrc-sazu.si, slabe@zrc-sazu.si
2 UNESCO Chair on Karst Education, University of Nova Gorica, 5271 Vipava, Slovenia, e-mails: knez@zrc-sazu.si, slabe@zrc-sazu.si
3 Yunnan University International Joint Research Center for Karstology, 650223 Kunming, China, e-mails: knez@zrc-sazu.si,  
slabe@zrc-sazu.si
4 Université Côte d'Azur, Polytech’Lab - UPR 7498, 06903 Sophia-Antipolis, France, e-mail: Philippe.AUDRA@univ-cotedazur.fr
Prejeto/Received: 7. 8. 2024
DOI: https://doi.org/10.3986/ac.v53i2-3.13889 
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
1. INTRODUCTION
Karren are important landforms on the karst surface of 
Provence. Their diversity leaves a special mark on the 
landscape, revealing the diverse shaping of surface karst 
forms. Three examples of karren are presented – through 
denudation they are changing from subsoil karren to kar-
ren directly exposed to rain. Origin and development of 
karren is precisely presented in a book Karst rock fea-
tures–Karren sculpturing (Ginés et al., 2009).
Provence is located in southeastern France (Figure 
1a) along the Mediterranean coast, and consists in large 
part of carbonates, mainly Mesozoic ones. The earliest 
karstifications appeared locally on structural highs at the 
end of the Cretaceous period, attested by the bauxites of 
the Durancian bulge. Transgressions invaded the lower 
topographic zones until the Miocene, with the deposition 
of molasses, which are occasionally carbonate. The struc-
ture is mainly composed of E–W folds that formed during 
the Pyrenean-Provençal phase. To the west, Alpine tecton-
ics are responsible for N–S structures superimposed on 
the Provençal folds. The relief consists of medium-altitude 
ridges and plateaus to the west, gradually rising towards 
the Alps, reaching elevations of 1500–1900 meters in the 
Préalpes de Grasse on the right bank of the Var River.
The climate is Mediterranean, characterized by heavy 
rainfall in autumn and spring, and a dry season in sum-
mer. Moving towards the Alps in the west, the climate re-
tains its Mediterranean characteristics but becomes more 
humid, especially on the initial reliefs exposed to marine 
influences. As a result of deforestation and forest fires 
over thousands of years, the vegetation has degraded into 
garrigue, which has been slowly reclaimed by the forest, 
particularly at higher altitudes and on the wetter northern 
slopes, due to the rural exodus over the past half-century.
The four areas studied are spread over a carbonate 
plateau to the west, in the case of Buoux at the foot of the 
Luberon mountain range, while the other three are tiered 
in the Préalpes de Grasse to the east.
Gréolières
The Gréolières site is the highest (43.801902°N, 
6.907847°E, alt. 1100–1150 m) of the areas studied. It lies 
in the Gréolières water gap on the steep rocky slopes of the 
Cheiron massif. The area is composed of Tithonian mas-
sive limestone (J9-n1) (Bodelle et al., 1980). The climate 
is mountain-Mediterranean, with annual temperatures 
and rainfall at the lower station of Gréolières (alt. 79 m) of 
11.4 °C and 1168 mm, respectively (1971–2000). In winter, 
snow cover on the north-facing slopes can last for several 
months, with frequent sub-zero temperatures, particularly 
at night. As the first orographic barrier behind the coast, 
precipitation remains regular throughout the year, even in 
summer.
Caussols
The Caussols site is located along the Ravin du Logis Neuf 
(43.750056°N, 6.872296°E, alt. 1050–1100 m), represented 
by the structural outcrops corresponding to the top of the 
Mesozoic carbonate formation, the Berriasian limestones 
(N1) (Bodelle et al., 1980). The climate is similar to that of 
Gréolières, with a mean temperature of 9.7 °C and an an-
nual precipitation of 1272 mm over the period 1991–2020.
Tourettes-sur-Loup
The Tourettes-sur-Loup site is located on the foothills 
of the Préalpes de Grasse, facing the Mediterranean 
(43.711942°N, 7.061447°E, alt. 300–330 m). The rock is 
carbonate molasse from the Lower Burdigalian of the 
Tourettes-sur-Loup Fm. (m1M) (Dardeau et al., 2010). 
Figure 1a: Location of the studied 
areas in Provence, France.
146 ACTA CARSOLOGICA 53/2-3 – 2024
KARREN OF PROVENCE (FRANCE), GRÉOLIÈRES, CAUSSOLS, TOURRETTES-SUR-LOUP AND LUBERON
The climate is Mediterranean with hot and dry summers, 
averaging 14.6 °C and 1031 mm (1991–2020).
Buoux
The Buoux site is a plateau dissected by dry gorges on the 
northern foothills of the Luberon chain (43.818522°N, 
5.378624°E, alt. 450–500 m). The rock is carbonate Bur-
digalian molasse (m1) (Germain et al., 1966). The climate 
is Mediterranean, characterized by hot, dry summers, 
with an average temperature of 12.1 °C and an annual 
precipitation of 816 mm.
Findings will be of great use in differentiating the 
development of the karst of Provence and its formation 
on different rocks and under different regional condi-
tions. They will also be important for differentiating de-
velopment models of karren on different rocks and in dif-
ferent environments, and for differentiating the forma-
tion of characteristic rock forms and their developmental 
transitions (Knez et al., 2003, 2010, 2011; Debevec, 2012; 
Knez et al., 2012; Al Faraj Al Ketbi et al., 2014; Gutiérrez 
Domech et al., 2015; Knez et al., 2015, 2017, 2019; Slabe 
et al., 2016, 2021; Knez et al., 2020, 2022, 2023).
2. 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 combined 
the studied karst features into a rock relief.
We defined the prevalent factors and the interaction 
of factors behind the formation of individual rock features. 
By combining these features into a rock relief, we attempt-
ed to determine the evolution of karst features.
We took a suitable number of rock samples from 
select geological profiles. We determined the appropriate 
distances between two samples or performed the sampling 
where a change in the rock was visible macroscopically.
We determined the colour of the rock using the es-
tablished colour chart (Munsell Rock-Color Chart, 2009).
In the laboratory we prepared microscope slides, i.e., 
thin sections, from the rock samples.
All microscopic thin sections were prepared and ex-
amined by transmitted light at different magnifications. 
Prior to the microscopic examination, a part of each thin 
section was dyed with alizarin red dye (1,2-dihydroxyan-
thraquinone, known also as Mordant Red 11); the calcite 
crystals were stained red, while the dolomite and non-car-
bonate crystals remained unstained (Evamy & Sherman, 
1962).
We devoted special attention to the porous rock 
samples from Tourrettes-sur-Loup. In order to present the 
type, shape and interconnection of void spaces as clearly 
and analytically as possible, we injected blue epoxy resin 
into a rock slice that had been prepared for attachment to 
the glass of a microscope slide (Gardner, 1980).
We performed complexometric analyses on all 
samples for the purpose of determining the proportion 
of calcite, dolomite, and insoluble residue in the rock. All 
samples were ground and dried at 105 °C for 24 hours fol-
lowed by cooling in a desiccator for 30 minutes prior to 
weighing. We used two reference methods – determina-
tion of calcium oxide by EGTA and determination of mag-
nesium oxide by DCTA (CEN, 2013). Both methods use 
photometric determination. Visual observation was per-
formed. The indicator methylthymol blue changes colour 
from pale green to pink in the case of calcium oxide, and 
from blue to grey in the case of magnesium oxide.
Combining the macroscopic observations in the field 
and the microscopic analyses using a transmitted light mi-
croscope at different magnifications in the laboratory, and 
by applying the results of the complexometric titration 
analysis, we are able to determine the properties of the rock.
3. SLOPE KARREN ABOVE GRÉOLIÈRES
SHAPE OF KARREN
The slope (Figures 1b, 2) develops on thick-bedded rock 
layers, which dip in the direction of the slope at a small 
angle. The slope is crossed by the faces of rock strata of 
various thicknesses that create steps. In some parts the 
steps are taller, reaching ten meters in height.
The walls, some overhanging and spanning several 
rock strata, appear to be the trace of collapsed caves. The 
ACTA CARSOLOGICA 53/2-3 – 2024 147
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
Figure 1b: Karren of Gréolières.
Figure 2: Karren of Gréolières: a. denuding subsoil channel, b. subsoil cup, c. subsoil transverse notch, d. channels, e. rain flutes with chan-
nels, f. channels formed mostly by water flowed from subsoil features, g. channels formed by water from bedding plane holes, h. steps.Loca-
tions of taken rock samples, numbers 1 to 22.
148 ACTA CARSOLOGICA 53/2-3 – 2024
surface of the karren is composed of often large, inclined, 
but predominantly flat or only slightly mounded rock 
plates and steep faces of the strata and the wall. Notches 
also developed along the lengthwise fissures that crisscross 
the rock strata. The initial roundedness of the mounds, 
which are highest in the middle and slope gently toward 
the edges, the cracks that appear along the fissures and the 
faces, and the smoothness of the rock are the consequence 
of subsoil formation. These features are particularly evi-
dent in the lower section of the karren. The karren de-
veloped in three dimensions. Along the more distinctive 
fissures where cracks occurred and in individual places 
where smaller vertical hollows occurred, the water flows 
downward to lower-lying bedding planes and then along 
them. Individual strata also appear to undergo karstifica-
tion. They are crisscrossed by numerous small hollows, 
mostly parallel to the bedding planes. The upper part of 
the karren is mostly denuded and the shrubbery, relatively 
dense in places, only grows from cracks and smaller hol-
lows filled with soil while the lower part is largely covered 
with a thin layer of soil. On some larger rock surfaces there 
are smaller and thinner rocks, the remains of the former 
upper layer of the rock. The karren are dissected by char-
acteristic rock relief forms that reveal their current forma-
tion and partly their development.
GEOLOGY
Macroscopic description
The selected profile of the rock above the village of 
Gréolières was examined in a thickness of around 50 m. 
Throughout the geological profile, the limestone is ex-
tremely hard, homogeneous, and compact. The layers are 
of varying thickness, mostly between 10 and 100 cm. Due 
to atmospheric impacts and vegetation, the surface of the 
rock is crushed in many places. In the lower part of the 
profile, which is quite overgrown and the rock is crushed 
on the surface, it is difficult to determine the real dip an-
gle of the layers. In the middle part of the profile, the dip 
angles of the layers are between 220/35 and 230/15, and at 
the top of the profile 340/4. In the field we took 22 samples 
of a homogeneous, hard, and nonporous rock at relatively 
even intervals. The macroscopically examined layers did 
not show any major differences, so we took samples of the 
rock evenly throughout the profile, i.e., at about every 2 m. 
The rock colour changes from a dark grey (brownish grey 
5YR 4/1) in the lower part of the profile, to light brownish 
grey (5YR 6/1) in the middle, and to almost white in the 
upper part of the profile (very light grey, N8).
Microscopic description
We turned each rock sample into a microscope slide. Af-
ter examining all of them, we have determined that the 
examined geological profile is in fact made up of geo-
logically very similar layers of rock. However, if we take 
a closer look, we can distinguish two groups of layers. 
In the lower part, the slope is made up of layers of pel-
biointrasparite to microsparite (mostly grainstone, only 
exceptionally packstone). In the upper part of the profile, 
the rock mostly contains intraclasts, which is why the 
predominant rock is intrapelsparite (mostly grainstone), 
which exceptionally transitions into intrapelbiomicrite 
(packstone) in the vertical direction over shorter seg-
ments. Throughout the geological profile, the highly pure 
limestone with various intraclasts within the layer is of a 
very similar composition, homogeneous, compact, and 
nonporous.
The layers of pelbiointrasparitic to microsparitic 
limestone are very similar. They differ in grain compac-
tion or cement content, in the frequency of calcite veins 
and, exceptionally in some layers, in the appearance of 
several cm large complete fossils and their fragments 
(samples from G1 to G12). The predominant grains in 
the rock are peloid grains, taking up around 80% of the 
volume. The majority of peloids are typical fecal pellets, 
which take up around 70% of the volume. The pellets are 
tiny; their cross-sections, which are visible in the micro-
scope slide, have diameters from 45 µm to 0.3 mm, while 
the large majority of them, i.e., 90%, measure 40 and 90 
µm in diameter, respectively. Intraclasts make up around 
30%. They are fully micritized, with no internal structure, 
and mostly measure between 90 µm and 0.3 mm in di-
ameter; they can be larger laterally, with diameters up to 
1 mm. Also visible in the rock are individual bioclasts; 
let us mention tiny foraminifera, miliolids, echinoderms, 
and individual fragments of unidentifiable fossils, most 
likely bivalves. Most grains touch each other. No grain 
sorting, a form of rock texture, is visible. There is very lit-
tle sparry cement due to good grain compaction. Where 
the grains do not touch, cement fills the rock with crys-
tals, usually measuring around 40 µm in diameter. The 
rock also contains individual fenestrae filled with sparry 
calcite, which can measure up to 2.2 mm in diameter. No 
primary porosity is visible in the rock. The calcite veins 
of several generations are mostly thin, between 20 and 
130 µm thick. The layers where grains do not touch and 
only make up about half of the volume have similar char-
acteristics (Figures 3a, c; sample G8). The other half is 
made up of cement, all of which is equant drusy mosaic 
spar. Most of the cement grains are anhedral to subhe-
dral; where spaces between the pelloids are larger, we also 
see euhedral crystals. The majority of sparry grains have 
a diameter between 0.1 and 0.3 mm, exceptionally up to 
0.7 mm. In some layers, especially within thicker calcite 
veins, we noticed individual dolomite crystals.
The layers of intrapelsparite (mostly grainstone), 
KARREN OF PROVENCE (FRANCE), GRÉOLIÈRES, CAUSSOLS, TOURRETTES-SUR-LOUP AND LUBERON
ACTA CARSOLOGICA 53/2-3 – 2024 149
which exceptionally transitions into intrapelbiomicrite 
in the vertical direction over shorter segments, are also 
very similar to each other. The predominant grains in the 
rock are intraclast grains, taking up around 70% of the 
volume. Pellets only make up a percent or two, and there 
are only a few specimens of tiny bioclasts, such as fora-
minifera and miliolids (Figures 3b, d; sample G17). The 
intraclast and pellet grains are fully micritized and with 
no internal structure. Most intraclasts have diameters be-
tween 0.2 and 0.5 mm, and the pellets between 45 and 90 
µm. All the cement between the grains is equant drusy 
mosaic spar. Most of the cement grains are anhedral to 
subhedral, exceptionally euhedral crystals. The major-
ity of sparry grains have a diameter between 90 and 180 
µm, exceptionally up to 0.7 mm. There are at least two 
generations of calcite veins in the rock. Most of them are 
thin, from 25 to 45 µm thick; only a few are thicker. No 
primary porosity is visible in the rock.
Complexometric analyses
Using the dissolution method (CEN, 2013), we performed 
13 complexometric analyses on 13 selected rock samples 
(Table 1). It has been determined that all profile samples 
exceed 99% of total carbonate content. The average value 
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
Figure 3: (a) Rock slice prepared for 
a thin section, sample G8. Width 
of view is 4 cm, (b) Rock slice pre-
pared for a thin section, sample 
G17. Width of view is 4 cm, (c) Thin 
section of sample G8. Lower half 
of sample was dyed in alizarin red 
dye. Width of view is 4 cm, (d) Thin 
section of sample G17. Lower half 
of sample was dyed in alizarin red 
dye. Width of view is 4 cm. 
Table 1: Complexometric analyses of rock samples from Gréolières.
Laboratory 
designation of the 
sample
Rock 
sample
CaO  
(%)
MgO  
(%)
Calcite  
(%)
Dolomite  
(%) CaO/MgO
Total 
carbonate 
(%)
Insoluble 
residue
(%)
V- 110/24 G1 55,36 0,46 98,81 0,96 120,35 99,77 0,23
V- 111/24 G3 54,96 0,76 98,09 1,59 72,32 99,68 0,32
V- 112,24 G4 55,61 0,36 99,25 0,75 154,47 100,00 0,00
V- 113/24 G6 55,12 0,58 98,38 1,21 95,03 99,59 0,41
V- 114/24 G8 55,39 0,31 98,86 0,65 178,68 99,51 0,49
V- 115/24 G9 53,95 1,62 96,29 3,39 33,30 99,68 0,32
V- 116/24 G12 55,63 0,34 99,29 0,71 163,61 100,00 0,00
V- 117/24 G13 55,64 0,33 99,31 0,69 168,61 100,00 0,00
V- 118/24 G15 55,51 0,36 99,07 0,75 154,19 99,82 0,18
V- 119/24 G17 55,56 0,37 99,16 0,77 150,16 99,93 0,07
V- 120/24 G18 55,65 0,32 99,32 0,67 173,91 99,99 0,01
V- 121/24 G20 55,61 0,36 99,25 0,75 154,47 100,00 0,00
V- 122/24 G23 55,62 0,35 99,27 0,73 158,91 100,00 0,00
150 ACTA CARSOLOGICA 53/2-3 – 2024
of all samples amounts to 99.8%. All samples show a high 
calcite percentage. Five samples have a calcite content of 
less than 99%; the average value of all samples is 98.8%. 
All samples also contain a small proportion of dolomite. 
Only one sample has a dolomite content of over 3%. The 
average value of all samples amounts to just over 1.05%. 
The samples also contain a small proportion of insoluble 
residue. Five samples contain no insoluble residue. The 
average value of all samples is 0.16%.
Impact on karstification
The entire profile of the rock, i.e., all the layers, react sim-
ilarly to karstification. The limestone is fine-grained; only 
in some places does it contain fossil remains, several cm 
large. It is homogeneous and compact. Its calcium car-
bonate content is almost 100%. The examined rock has 
excellent properties; on it, subsoil and rain rock features 
can develop efficiently, smoothly, and successfully.
ROCK RELIEF
Subsoil rock forms
The most characteristic rock forms are subsoil channels 
and subsoil cups (Slabe & Liu, 2009). The cross-sections 
of both reach several decimetres in size. The subsoil cups 
reach one meter in diameter only on the gentlest sloping 
surfaces. Subsoil channels (Figures 2a, 4a) are found on 
the upper inclined and gently sloping surfaces as well as 
on the faces of strata where they are vertical. The bot-
toms of the channels that formed along fissures are hol-
lowed by vertical tubes (Figure 4b). The subsoil cups 
(Figure 4c) are shallow on the more gently sloping upper 
surfaces while at the edges of the strata they are deeper 
and open on the outer side. The latter are in the develop-
mental transition into subsoil funnel-like notches (Fig-
ures 2b, 4d). Along a long-term soil level on the lower 
strata steps a few decimetres in size can occur on the face 
of the upper strata. They are also found at the bottoms 
of denuded funnel-like notches. A large proportion of 
the subsoil cups are filled with sediment and overgrown 
(Figure 4b). Their edges are raised above the rest of the 
rock surface. Funnel-like subsoil notches (Figure 4d) de-
veloped on steep edges where water converged from the 
larger surfaces of sloping tops. The largest reach one me-
ter in diameter.
The more gently inclined surfaces are dissected 
by transverse notches (Figures 2c, 4e). They are several 
meters long and only a few centimetres deep and wide. 
They have flat and smooth bottoms. Often they have been 
transformed into channel-like solution pans. Some have 
widened in a circular fashion and are open on the runoff 
side (Figure 4f). This indicates a long-term level of soil 
cover where water flowing to it from the higher bare rock 
surface was dammed by the soil. At some levels only in-
dividual horseshoe-shaped open cups developed. These 
forms are often found one above the other along the fall 
line of the slope, which indicates gradual denudation. 
Descriptions of such rock forms are not found in the sci-
entific literature.
Subsoil-shaped fissures are found along more dis-
tinct cracks. On their walls are vertical subsoil channels 
while subsoil tubes with circular cross sections are found 
along smaller cracks. They can be connected by subsoil 
fissures, channels, and cups. The relatively dense perfora-
tion on bedding planes and vertical fissures as well inside 
the strata has a subsoil origin (Figures 4a, 4b, 4g).
Traces of rainwater and creeping and trickling water
Well preserved subsoil rock forms and the rounded and 
often smooth rock surface testify to the relatively recent 
denudation of the karren. Denuded subsoil forms are 
transformed by rainwater and trickling water, and from 
the overall rock relief it is possible to discern the progress 
of the gradual denudation of the karren. It occurred on 
individual surfaces from the top down or vice versa as 
the faces were denuded first and then the surfaces above 
them. The lower part of strata faces often developed lon-
ger under the soil.
Channels (Figures 1b, 2, 4h) are the rock form that 
gives the primary stamp to the formation of karren. They 
are found on both steep and gently sloping surfaces. They 
occur individually but most frequently lying parallel to 
each another. They can be several meters long and their 
diameters range from a few centimetres to decimetres in 
size. Depending on their origin they can be classified into 
several types. The first type of channel (Figures 2d, 4i) 
collects water, mostly rainwater, which flows across rela-
tively large areas on more or less flat and gently inclined 
tops of karren. On the evenly gently sloping surfaces the 
upper parts of channels are up to five centimetres wide 
and shallow and increase steadily in size toward the bot-
tom (Figures 4j, 4k). They are relatively wide from the 
start. Upwards they gradually transform into a smooth 
or stepped surfaces from which water flows into them. In 
places they lie side by side. The laboratory experiment on 
the formation of rain flutes in plaster of Paris showed a 
similar formation process on the soluble surface of plas-
ter exposed to rain (Slabe 2005, 113). In dense networks, 
there are only ridges between channels. Shallow channels 
are stepped. The steps are only one centimetre high. On 
previously dissected parts of surfaces, which are relative-
ly few in number, branched networks developed. Protru-
sions with rain flutes and smaller funnel-like notches are 
found among them. Some developed from denuded sub-
soil channels while others could have originated as the 
lower parts of bedding plane anastomotic tubes.
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ACTA CARSOLOGICA 53/2-3 – 2024 151
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
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ACTA CARSOLOGICA 53/2-3 – 2024 153
At the bend below a gently sloping surface where 
it becomes steeper, channels form where the water con-
solidates in a stream after creeping evenly across the large 
surface above. They are dissected by steps. This applies 
to channels on steep surfaces that have grown upward. 
Laboratory testing on plaster of Paris also revealed this 
type of formation (Slabe 2005, 116). The channels have 
semi-circular mouths and some resemble solution pans 
that over time develop into funnel-like notches (Figure 
4l). On steeper surfaces such channels can be stepped 
(Figure 4m). Their circumference is dissected by a num-
ber of funnel-like notches arranged one above another. 
A channel of a different origin, described below, can also 
lead into an initial funnel-like notch. This could therefore 
be a composite rock form. On the steeper slopes channel 
(Figures 2e, 4h, 4n, 4o, 4p) develop under the edge with 
rain flutes. They begin with funnel like notches. They de-
velop from rain channels.
Channels also form due to water trickling from 
the soil that fills cracks and subsoil cups (Figures 2f, 
4h, 4q, 4r, 5a, 5b, 5c). These too form mostly in paral-
lel where rainwater and water trickling down inclined 
surfaces both contribute to their development. They are 
frequently larger and especially deeper on the inflow side 
and have funnel-like mouths. This characteristic helps 
us distinguish them from channels formed primarily by 
rainwater or to understand the development of compos-
ite channels. The beginning section can meander due to 
the locally smaller incline of the rock surface. This kind 
of channels prevail and they are the most expressive rock 
features. The deepest channels have winding bottoms.
A special type of channel (Figure 5d) forms due to 
the discharge of water from tubes that develop along bed-
ding planes, that is, from under upper-lying rock strata. 
They often begin with funnel-like notches that are wide if 
the water flows from a larger surface (Figure 5e). Narrow 
forms whose cross sections resemble an inverted omega 
sign occur when the water flows continuously from a 
tube.
Channels also lead from some larger solution pans.
Channels of various origins are thus interwoven on larger 
rock surfaces and can assume the role of a direct collector 
of rainwater and water that trickles down the rock. Chan-
nels that occurred due to the water discharging from the 
soil can be left hanging and transformed by rainwater 
(Figure 4p). Due to the three-dimensional development 
of the karren, the level of the soil in a vertical subsoil tube 
can lower faster than the deepening of the channels that 
originally led from it.
Solution pans (Figure 2h, 4f) are found in places at 
the bottom of the more gently sloping channels (Figure 
5f) and notches, and weathered debris from fallen veg-
etation periodically builds up in other channels. They are 
partly subsoil deepened and widened at the bottom.
The walls of larger channels are dissected by verti-
cal channels a few centimetres in size where water flows 
in from the surrounding surface (Figures 4j, 4p, 5g). On 
laterally inclined surfaces on the upper rims of channels 
there are small channels, and rain flutes (Figures 4a, 4p) 
are found on the lower edge. The distribution of these 
rock forms on dissected surfaces varies. The bottoms, 
however, are smooth as a rule, and often more distinctly 
winding than the rest of the channel.
On the bends where inclinations of the rock surface 
change distinctly, all the larger channels are distinctly 
deeper. Relative to their formation, the latter types of 
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
Figure 4: (a) Subsoil channel and meandering channel in the middle right, (b) Subsoil hollows, (c) Subsoil cup. Width of view is 2 m, (d) 
Subsoil cup in the bottom of funnel like notch, (e) Transverse notch. Width of view is 6 m, (f) Transverse notches with cups. Width of view 
is 4 m, (g) Hollows. Width of view is 2 m, (h) Channels, (i) Channels, (j) Channels on evenly gently sloping surface. Width of view is 10 m, 
(k) Channels on evenly gently sloping surface. Width of view is 5 m, (l) Channels on evenly gently sloping surface. Width of view is 2 m, 
(m) Channels on steep slope, (n) Channels below rain flutes. Width of view is 4 m, (o) Channels below rain flutes, (p) Channels below rain 
flutes, (q) Channels below subsoil features. Width of view is 3 m, (r) Channels below subsoil features.
154 ACTA CARSOLOGICA 53/2-3 – 2024
KARREN OF PROVENCE (FRANCE), GRÉOLIÈRES, CAUSSOLS, TOURRETTES-SUR-LOUP AND LUBERON
ACTA CARSOLOGICA 53/2-3 – 2024 155
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
Figure 5: (a) Channels below subsoil features, (b) Channels below 
subsoil features. Width of view is 4 m, (c) Channels below subsoil 
features, (d) Channels below bedding planes, (e) Channels below 
bedding planes. Width of view is 2 m, (f) Solution pan. Width of 
view is 0.5 m, (g) Channels in the wall of large channel. Width of 
view is 5 m, (h) Large steps. Width of view is 2 m, (i) Longitudinal 
steps. Width of view is 5 m.
channels also rank among the composite rock forms. 
They are sculpted jointly by rainwater and trickling water.
The development of parallel channels in the direc-
tion of the surface dip is characteristic of these karren. 
Branched connections are rare. This seems to be the 
characteristic of the recent formation of larger surfaces 
of relatively gently sloping flat and smooth rock where 
the main factor of its formation is the rainwater flowing 
to channels from the side. Between the protrusions with 
rain flutes that dissect the surface in some places are the 
outlines of branched networks of channels. Longer ridg-
es occur between larger channels of subsoil origin and 
channels lying side by side and the surface between them 
is the ridge itself. It appears that like this is a more mature 
form of karren dissection.
Smaller rock forms carved by rainwater and water 
trickling down the rock reveal an even more detailed de-
velopment of the recently denuded rock.
Rain flutes (Figure 4n) as a rule dissect the upper 
edges of the larger inclined flat surfaces of the tops (Fig-
ures 4p, 4r, 5b, 5d, 5e).
On the surface below them a layer of water that 
originates from the water trickling downwards is too 
thick and prevents rainwater to reach the rock directly, 
so, no rain flutes are found here. These only occur on 
rare smaller protrusions dissecting the relatively flat tops 
(Figure 4a). Larger and smaller steps (Figures 4j, 4k, 4l), 
the trace of the relatively even creeping of water across 
larger rock surfaces, form on the flat surfaces below the 
rain flutes. There are flutes on the faces of strata and 
their lateral edges only if they are not covered by larger 
amounts of water from the upper part of the strata, if the 
surfaces above them are short, or if the edge is higher. 
This type of formation also appeared in laboratory tests 
with plaster of Paris (Slabe, 2005, 2009). Only if these 
strata are shorter are flutes found across the entire sur-
face. Rain flutes also dissect protrusions, which in most 
cases are the ridges that eventually dissect the surfaces of 
originally flat tops. Funnel-like notches (Figures 4p, 5b, 
5d) form at the beginning of surfaces, relatively small at 
first, with flutes at the circumference.
The relatively large, flat, and inclined surfaces of the 
tops are dissected by larger and smaller steps (Figures 4j, 
4k, 4l). On the lower part of the surface, the water from 
them flows over the edge of the face in channels whose 
upper parts are co-formed by rainwater (Slabe, 2005, 
2009). The thick layer of water creeping across the steps 
from the upper part of the surface to the edge of the rock 
strata where channels with funnel-like mouths are often 
found does not allow drops of rain to contact the rock di-
rectly and consequently the formation of rain flutes is not 
possible except at the beginning edge of the surface. Trac-
es of an even sheet of creeping water therefore dominate 
on the rock. This requires fulfilling certain conditions 
relative to the amount of water on the rock and the size 
of the surface and its inclination. In this case, the condi-
tions are very favourable for the development of this type 
of rock relief. This is a young stage in the development 
following denudation from under soil.
In most cases the rock forms are composite. Large 
steps (Figures 2h, 4f, 5h) have circular or horseshoe 
shapes and those which lie crosswise to the slope are of-
ten several meters long and a few decimetres in width 
(Figures 4e, 4f). They are open on the runoff side and 
have steep upper edges. Some steps are partly closed on 
the runoff side by smaller protrusions. Protrusions are 
steep on the inflow side of the steps, and rain flutes dis-
sect the outer side. Together, the connected circular steps 
and channel-like steps often create the appearance of un-
dulation in the rock surface.
Larger surfaces of non-dissected rock and the forms 
described above have small steps (Figures 2h, 4j, 4k, 4l, 6a) 
a few centimetres in diameter, while medium sized steps 
are up to one decimetre in diameter and relatively shal-
low. They are open on the outflow side. The small steps 
lie side by side, connected in a network whose shape is 
dictated primarily by the composition of the rock and its 
inclination. They are also found in channels especially in 
the initial periods of development of channels on gently 
sloping surfaces; on steep slopes, however, they are char-
acteristic of channels even later (Figure 4n). In smaller 
and medium-sized channels the small steps are elongated 
156 ACTA CARSOLOGICA 53/2-3 – 2024
as a rule, as long as they are wide, and larger channels are 
dissected by a network of small steps.
The network of various steps and small steps that 
reveal the sheet pattern of flow over the rock is more 
distinctly developed on surfaces denuded for a longer 
time. These forms are naturally not found on rock that 
has been covered by soil until recently; such surfaces are 
smooth or have a network of mostly individual cups in 
the initial phase of development.
Solution pans often develop from subsoil solution 
pits at the bottom of gently sloping, longitudinal, and 
channel-like notches of subsoil origin. They are shal-
low and open on the runoff side. On denuded rock some 
notches transform into channel-like solution pans. Pans 
are also found at the bottom of larger gently sloping 
channels (Figure 5f).
There are scallops on overhanging surfaces (Figure 
6b) that reveal the way water trickles: the faster the flow, 
the smaller they are.
DEVELOPMENT MODEL
At the top of the karren on the upper surfaces of an in-
clined rock strata along which a slope formed a unique 
rock relief developed that reveals the manner of karren 
formation and its development. Relatively large surfac-
es of unfissured, mostly evenly composed, and largely 
subsoil rounded and smooth and later denuded rock 
mostly exposed to rain resulted in special hydraulic cir-
cumstances that fostered the formation of rock forms 
and the development of the rock relief. On the parts of 
rock directly exposed to rain there are rain flutes, and 
where the layer of water trickling down the inclined 
surface is thicker, there is a system of large and small 
steps that dissect the surface in an undulating fashion. 
The trickling water collects in channels that in parallel 
dissect the surface and together with the channels that 
conduct the water from subsoil rock forms gradually 
assume the role of the main conductors and increas-
ingly distinctly dissect the tops of the karren. Relative-
ly flat surfaces with dominant traces of sheet flow of 
large amounts of water therefore represent one of the 
initial stages in the development of the denudation of 
this type of rock base. New factors gradually transform 
the subsoil rock relief that is revealed when the rock is 
denuded. Only in individual places does the compo-
sition of the rock dictate the development of protru-
sions on flat surfaces. The long-term parallel position 
of channels also appears to be dictated by the hydraulic 
conditions of this type of formation of larger inclined 
surfaces, which has been confirmed by laboratory tests 
with plaster of Paris. On the latter, the most conductive 
channels gradually assume the leading role. A number 
of forms have been newly identified and described in 
detail for the first time with the development of this 
type of the relief.
4. THE KARREN OF CAUSSOLS
SHAPE OF KARREN
The central part of the karren is characterized by a rela-
tively flat, gently sloping and mostly denuded rocky top 
surface, which rises towards the west in the form of large 
steps. The western part is more steeply stepped and over-
grown with trees (Figures 7, 8).
It seems that the karren were entirely overgrown 
with a thin forest of pines and oaks, and that the entire 
KARREN OF PROVENCE (FRANCE), GRÉOLIÈRES, CAUSSOLS, TOURRETTES-SUR-LOUP AND LUBERON
Figure 6: (a) Small steps. Width of view is 5 m, (b) Scallops od trickling water on overhangs.
ACTA CARSOLOGICA 53/2-3 – 2024 157
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
Figure 7: Karren of Caussols.
Figure 8: Rock relief of karren. a. subsoil shaft, b. uncovered subsoil funnel-like notch, c. subsoil channel, d. uncovered subsoil channels, e. 
steps, f. funnel-like notch, g. rain flutes, h. transformed subsoil cups. Locations of taken rock samples, numbers 1 to 23.
158 ACTA CARSOLOGICA 53/2-3 – 2024
rock was covered with soil and moss. Their top section 
and their lowest section are like that now. In the top, 
overgrown section the surface of the karren is dissected 
by rocks and stone teeth (Figure 9). Water is intensely 
dissolving the rock beneath the vegetation and soil. The 
denuded rock in the central part is being reshaped by 
rainwater. That is why the top beds of the rock are disin-
tegrating and sliding downwards along the bottom beds. 
A section of the karren might have been artificially un-
covered, most of it a long time ago, as indicated by the 
rock relief. The latter is completely flat and free of rocks, 
i.e., of the remains of rock beds. A part of the top sec-
tion of the karren is covered with rocks that were thrown 
there during road construction.
All the stages of denudation caused by the disinte-
gration of the top rock beds and uncovering of soil are 
being revealed, as are the stages of the reshaping of the 
relatively flat, vast and gently sloping surfaces of the tops 
of karren. The karren rock relief is made up of subsoil 
rock forms; of rock forms being created beneath the 
moss; of rock forms that develop due to their reshaping 
by rain; and of rock forms hollowed out by rainwater and 
the water trickling down the rock.
The distinct rock relief enables us to clearly define 
the development model, which is widely applicable to 
similar rock surface formation.
GEOLOGY
Macroscopic description
We thoroughly examined a 9 m tall geological profile 
of limestone, where a few layers outcrop roughly in the 
middle over a larger surface, containing well-developed 
karren. In the lower part of the profile the layers, up to a 
few dm thick, are quite crushed, while those in the mid-
dle and upper part are hard and compact. The dip angle 
of layers from the foot to the top varies slightly; the pre-
dominant angle is to the north and between 16 and 260. 
The direction of the layers' dip angle is between 5 and 260. 
In the field we took 23 samples of a homogeneous, hard, 
compact, and nonporous rock at relatively even intervals. 
No major differences were detected in the samples mac-
roscopically. The rock was of a light grey to brown colour, 
with the colours pinkish grey (5YR 8/1) and light brown-
ish grey (5YR 6/1) being predominant.
We mostly focused on the subvertical cracks in the 
rock layers exposed to the atmosphere and on their aver-
age directions, on the width of the karstified cracks and 
on the depth of karstification, as the dip angle and direc-
tion of the layers change slightly in the lateral direction 
from the east to the west side. At a dip angle of 25/16 
the cracks have the prevailing direction of 170–350, and 
width of 5–10 and 30–40 cm. At a dip angle of 22/19 
the cracks have the prevailing direction of 35–215 and 
10–190, and width of 10–20 cm. At a dip angle of 25/16 
the cracks have the prevailing direction of 165–345 and 
0–180, and the prevailing width of 10 cm. At a dip angle 
of 20/25 the cracks have the prevailing direction of 0–180 
and 170–350, and width of 100–200 cm, exceptionally 
20–30 cm. At a dip angle of 10/22 the cracks have the 
prevailing direction of 175–355 and 0–180, and width of 
50–100 cm. Most cracks are karstified up to the depth 
of 10 cm and between 30 and 40 cm; in some areas they 
are even karstified up to the depth of 100–150 cm. The 
KARREN OF PROVENCE (FRANCE), GRÉOLIÈRES, CAUSSOLS, TOURRETTES-SUR-LOUP AND LUBERON
Figure 9: Part of the karren over-
grown by vegetation.
ACTA CARSOLOGICA 53/2-3 – 2024 159
karstified cracks are either interconnected or unconnect-
ed, and have in some places widened into isolated holes.
Microscopic description
Based on 23 microscope slides, one from each rock 
sample, we divided the rock in the examined profile into 
three lithological types that alternate in an irregular se-
quence in the vertical direction, in groups of several lay-
ers about half a meter thick. In roughly half of the thick-
ness of the geological profile we can trace layers of pel-
sparite to pelintrabiosparite of grainstone type. The other 
half of the profile's thickness is largely taken up by layers 
of intrabiosparitic to intrabiomicritic limestone with nu-
merous calcite veins and grainstone- to packstone-type 
fenestrae, and by several layers of micritic limestone of 
mudstone type with stylolites. These properties of the 
layers were not visible during the sampling and macro-
scopic determination. The group of layers on or in which 
the examined rock features have developed the most, are 
almost entirely fine-grained with a sparry cement, or 
fine-grained and micritic. These layers contain no larger 
fossils or their fragments, nor any larger intraclasts.
Layers of pelsparitic and pelintrabiosparitic limestone 
(grainstone) can be found throughout the middle part of 
the profile (samples C3 to C6, C11 to C17). Peloid grains 
are almost entirely predominant in the rock, taking up be-
tween 80 and 90% of the volume. Most of the peloids are 
pellets (90 to 95% of the volume), while intraclasts take up 
between 5 and 10%. The intraclasts are micritized, with no 
internal structure, and mostly measure between 0.3 and 
1.1 mm in diameter. Also visible in the rock are individual 
bioclasts, mainly miliolids and uniserial and biserial fora-
minifera, mostly measuring 0.2 mm in diameter and not 
exceeding 0.9 mm. Only exceptionally do we see bivalves in 
the rock with a shell diameter of up to 4.5 mm with no shel-
ter porosity in the shells. Bioclast grains, which also make 
up the rock, only amount to a few percent. As regards tex-
tures, we observe a distinct roundness of the grains in the 
microscope slide, whereas various cavity structures are not 
visible. All the cement between the grains is equant drusy 
mosaic spar. Most of the cement grains are anhedral to sub-
hedral; where spaces between the pelloids are larger, we also 
see euhedral crystals. The majority of sparry grains have a 
diameter of 45 µm, exceptionally up to 0.4 mm. Thus, the 
xenotopic to hipidiotopic spar texture and fabric are pre-
dominant among the micritized pelloids (Figures 10a, c; 
typical example sample C3). The grains of typical fecal pel-
lets and intraclasts are highly micritized; the spaces within 
the bioclasts are filled with mosaic drusy sparry calcite with 
no internal structure. There are no signs of compaction in 
the rock, nor any stylolites. Exceptionally we observe sec-
ondary porosity in the rock; the cracks of a single genera-
tion, with diameters up to a few µm, are entirely filled with 
mosaic drusy sparry calcite and individual spar crystals in 
them are dolomitized. There is no visible primary porosity.
Layers of intrabiosparitic to intrabiomicritic lime-
stone with numerous calcite veins and fenestrae (grain-
stone to packstone) can be seen partly in the lower and 
partly in the upper part of the profile (samples C1, C2, C7, 
C8, C18 to C23). A typical example of this group of layers 
is sample C19 (Figures 10b, d). The rock is almost entirely 
made up of fully micritized intraclasts with no internal 
structure, of varying shapes and sizes. Most intraclasts 
measure between 0.2 and 0.5 mm in diameter, followed 
by those with diameters between 45 µm and 0.2 mm; only 
individual intraclasts have diameters larger than 0.5 mm. 
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
Figure 10: (a) Rock slice prepared 
for a thin section, sample C3. Width 
of view is 4 cm, (b) Rock slice pre-
pared for a thin section, sample 
C19. Width of view is 4 cm, (c) Thin 
section of sample C3. Lower half 
of sample was dyed in alizarin red 
dye. Width of view is 4 cm, (d) Thin 
section of sample C19. Lower half 
of sample was dyed in alizarin red 
dye. Width of view is 4 cm.
160 ACTA CARSOLOGICA 53/2-3 – 2024
In most cases the intraclasts, which take up around 80% of 
the rock, touch each other, forming areas without a sparry 
cement in between, measuring between 0.4 and 2.2 mm 
in diameter. Other clasts that make up the rock, in ad-
dition to those mentioned above, are bioclasts of several 
types. The prevailing types are miliolids and uniserial and 
biserial foraminifera, mostly measuring up to 0.2 mm in 
diameter; only individual ones reach 0.9 mm. The micro-
scope slide also contains individual specimens of poorly 
preserved algae and echinoderms, of gastropods filled 
with sparry calcite, usually measuring around 0.5 mm in 
diameter, and of individual fragments of bivalves trans-
ferred to a secondary location. No texture characteristics, 
such as sorting, are visible in the rock. Judging from the 
good compaction of micritized intraclasts, we can de-
scribe the mostly unconnected areas in between, which 
are estimated at around 15%, as fenestrae filled with drusy 
sparry calcite. Most of them have diameters between 90 
µm and 0.9 mm, but those with diameters around 0.5 mm 
are predominant; they are evenly distributed throughout 
the rock. Most of the sparry cement grains are anhedral 
to subhedral; in some places we also see euhedral crystals. 
The majority of sparry grains have diameters from 45 to 90 
µm, exceptionally also up to 1 mm. Thus, sparry cement is 
predominant as xenotopic to hipidiotopic texture and fab-
ric. There is no visible primary porosity. In the rock, many 
calcite veins of several generations are distributed in vari-
ous directions and with a thickness between 20 µm and 0.4 
mm. The predominant ones are between 90 µm and 0.4 
mm thick; only individual ones are thicker, measuring up 
to 1.1 mm. All of them, with the exception of the thickest 
ones, are entirely filled with mosaic drusy sparry calcite. In 
the vertical direction the described layers gradually transi-
tion into layers of pelsparitic and pelintrabiosparitic lime-
stone, and into layers of micritic limestone.
Layers of micritic limestone of mudstone type with 
stylolites are located in the middle part of the profile 
(samples C9, C10). The fully micritic rock contains only 
individual bioclasts, well-preserved miliolids, ostracods 
and, due to intense micritization, unidentifiable tiny fos-
sil fragments. Together, they make up less than 1% of the 
space. The rare fenestrae are also entirely filled with drusy 
sparry calcite, measuring from a few µm to 0.9 mm in 
diameter. There is no primary porosity. There are many 
stylolites in the rock, which are characteristic of this rock 
type; they are distributed in various directions and with 
amplitudes between 0.4 and 1.3 mm.
Complexometric analyses
Using the dissolution method (CEN, 2013), we per-
formed 15 complexometric analyses on 15 selected rock 
samples (Table 2). It has been determined that all profile 
samples exceed 98.7% of total carbonate content. The av-
erage value of all samples amounts to 99.6%. All samples 
show a high calcite percentage. Only one sample has a 
calcite content of less than 98%; the average value of all 
samples is almost 98.8%. All samples also contain a small 
proportion of dolomite. Only one sample has a dolo-
mite content of over 1%. The average value of all samples 
amounts to just over 0.85%. The samples also contain 
a small proportion of insoluble residue. Three samples 
contain no insoluble residue, while in two samples the 
value of insoluble residue exceeds 1%. The average value 
of all samples amounts to 0.37%.
KARREN OF PROVENCE (FRANCE), GRÉOLIÈRES, CAUSSOLS, TOURRETTES-SUR-LOUP AND LUBERON
Table 2: Complexometric analyses of rock samples from Caussols.
Laboratory 
designation of the 
sample
Rock 
sample
CaO  
(%)
MgO  
(%)
Calcite  
(%)
Dolomite 
(%) CaO/MgO
Total 
carbonate 
(%)
Insoluble 
residue
(%)
V- 95/24 C1 55,38 0,47 98,84 0,98 117,83 99,82 0,18
V- 96/24 C2 55,37 0,46 98,82 0,96 120,37 99,78 0,22
V- 97/24 C3 55,65 0,32 99,33 0,67 173,91 100,00 0,00
V- 98/24 C6 55,60 0,36 99,23 0,75 154,44 99,98 0,02
V- 99/24 C7 55,60 0,37 99,23 0,76 150,23 100,00 0,01
V- 100/24 C8 55,57 0,38 99,18 0,79 146,24 99,97 0,03
V- 101/24 C10 55,03 0,43 98,22 0,90 127,98 99,12 0,88
V- 102/24 C11 55,61 0,36 99,25 0,75 154,47 100,00 0,00
V- 103/24 C14 55,41 0,35 98,90 0,73 158,31 99,63 0,37
V- 104/24 C15 54,98 0,49 98,13 1,03 112,20 99,16 0,84
V- 105/24 C16 55,58 0,38 99,20 0,79 146,26 99,99 0,01
V- 106/24 C17 55,26 0,42 98,63 0,88 131,57 99,51 0,49
V- 107/24 C19 55,56 0,40 99,16 0,84 138,90 100,00 0,00
V- 108/24 C20 54,74 0,46 97,70 0,96 119,00 98,66 1,34
V- 109/24 C23 54,79 0,48 97,79 1,00 114,15 98,79 1,21
ACTA CARSOLOGICA 53/2-3 – 2024 161
Impact on karstification
The entire geological profile, i.e., all the layers that make 
up the geological profile, react similarly to karstification. 
Fine-grained, homogeneous and compact limestone with 
a high calcium carbonate content is a rock with excellent 
properties, on which subsoil and rain rock features can 
develop efficiently, smoothly, and successfully. The devel-
opment of karren is mostly influenced by the cracking of 
the rock.
ROCK FORMS AND ROCK RELIEF
Subsoil rock forms
Subsoil holes formed along bedding planes and vertical 
cracks. Their diameter reaches 10 cm and some of them 
have been paragenetically raised (Figure 11a) and deep-
ened with a floor channel (Figure 11b) after the denuda-
tion of karren. There are subsoil shafts (with cross-sections 
in the cm to m ranges), which are dissected in some places 
(Figure 8a, 11c), and fissure caves along the cracks. In 
the overgrown section of the karren, trees and bushes are 
growing out of them (Figure 11d). The funnel-like notches 
on their top edges (Figure 8b, 11e) indicate a downward 
percolation of water through the vertical fissures. The fun-
nel-like notch is a typical rock formation created by water 
runoff from karst surfaces into the rock’s interior by gradu-
ally eroding the rock. On larger peaks, the mouth of a wall 
channel typically forms along the peak’s edge (Knez et al. 
2015), while in fractured rock areas, they tend to appear 
between the tips of rocks into which the surface has been 
dissected (Knez et al. 2012). As water continues to dis-
sect larger rock surfaces on peaks, it can create new rock 
tips through prolonged erosion (Slabe et al. 2021). Thus, 
funnel-like notches represent erosion paths formed by 
water runoff from expansive surfaces or dispersed sources 
(such as rainwater or water seeping through soil), which 
eventually gathers into streams, further eroding the rock. 
Smaller holes have also formed from the subsoil cups at 
the edges of fissures (Figure 11f). The walls also contain 
subsoil channels (Figure 11g); smaller subsoil half-bells 
(Figure 11h); subsoil longitudinal notches, which show 
that soil surrounded the rock for a longer period of time; 
and subsoil scallops (Figure 11i) on the overhangs, which 
are a trace of the sheet trickling of water at the contact 
with soil. Notched into the surface of the top of the kar-
ren are subsoil channels (Figure 8c, 11j), which sometimes 
continue down the wall (Figure 11k), and subsoil cups. 
In some places, the subsoil cups continue in the form of 
channels. On the vaster and sloping surfaces, parallel and 
meandering subsoil channels have formed (Figures 8d, 
11l, 11m). At the edge they flow into a wall channel via a 
funnel-like notch (Figure 11n). The channel dissects the 
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
162 ACTA CARSOLOGICA 53/2-3 – 2024
KARREN OF PROVENCE (FRANCE), GRÉOLIÈRES, CAUSSOLS, TOURRETTES-SUR-LOUP AND LUBERON
ACTA CARSOLOGICA 53/2-3 – 2024 163
wall of the fissure hole or shaft (Figure 11c). The channels 
often merge into a larger channel in the form of branches. 
On the densely cracked and fissured rock, the smaller tops 
are more densely crisscrossed with smaller, longitudinal 
and transversal subsoil channels and subsoil cups. Some of 
them continue on the rock beyond the fissures, which in-
dicates that they were relatively tightly filled (Figure 11o). 
They can continue to develop even after they are fully or 
partially filled with soil and the rest of the rock is bare 
(Figure 11p). Some develop cross-sections resembling an 
upside-down omega (Figure 11q). There are individual 
subsoil cups on the bottoms of larger and denuded subsoil 
channels. In some places, there are subsoil notches around 
the mouths of fissures and small shafts (Figure 11r), which 
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
Figure 11: (a) Parageneticaly increased hollow. Width of view is 3 m, (b) Flor channel in hollow. Width of view is 2 m, (c) Subsoil shaft. 
Width of view is 1 m, (d) Trees grown from karren, (e) Funnel-like notches. Width of view is 1.5 m, (f) Hollow, developed from subsoil cup, 
(g) Subsoil wall channel. Width of view is 2.5 m, (h) Subsoil half-bells. Width of view is 3 m, (i) Subsoil scallops, (j) Subsoil channels. Width 
of view is 1 m, (k) Subsoil wall channels. Width of view is 1.5 m, (l) Subsoil channels. Width of view is 5 m, (m) Subsoil channels. Width 
of view is 2.5 m, (n) Subsoil wall channels. Width of view is 1 m, (o) Subsoil channels. Width of view is 2 m, (p) Covered subsoil channels. 
Width of view is 1 m, (q) Deep subsoil channel. Width of view is 2 m, (r) Subsoil longitudinal notch. Width of view is 5 m.
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were formed when the holes were still full and the sur-
rounding surfaces above them were covered or when sub-
soil channels led into them (Figure 12a). They are dissected 
into funnel-like notches. The surfaces between them have 
already been exposed.
Rock forms hollowed out by rainwater and water 
trickling down the rock, and the reshaping of subsoil 
rock forms
The vaster and relatively flat and smooth surfaces of the 
tops of karren, which are formed on the less densely 
Figure 12: (a) Subsoil channel with notch. Width of view is 0.75 m, (b) Steps. Width of view is 5 m, (c) Steps. Width of view is 3 m, (d) Rain flutes. 
Width of view is 4 m, (e) Rain flute and steps bellow. Width of view is 3 m, (f) Rain flutes on the wall of steps. Width of view is 4 m, (g) Chan-
nels. Width of view is 1.5 m, (h) Funnel-like notches with rain flutes. Width of view is 6 m, (i) Rain flutes. Width of view is 2 m, (j) Different 
tops. Width of view is 5.5 m, (k) Small channel in the bottom of larger. Width of view is 1 m, (l) Cascade bottom of the channel, (m) Rain flutes 
on the wall of the channel, (n) Deepen denuded subsoil channel. Width of view is 1.5 m, (o) Moss overgrown bottom of the channel. Width of 
view is 1 m, (p) Solution pan. Width of view is 1 m, (q) Solution pan with rain flutes on walls, (r) Solution pan, transformed in to the channel.
ACTA CARSOLOGICA 53/2-3 – 2024 167
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
cracked rock, are mostly reshaped by a thicker layer of 
water flowing downwards. Such surfaces are initially sub-
soil or form along bedding planes as the top bed of the 
rock is disintegrating. Steps in the centimetre and deci-
metre size ranges are forming (Figures 8e, 11r, 12b, 12c) 
(Knez et al., 2015). Funnel-like notches and channels be-
low them (Figures 8f, 12b) are forming on the side edges 
of larger steps. Rain flutes (8g) are forming on the higher 
top edge and in some places on the side edge (Figure 12d) 
where raindrops reach the rock directly. The rock is be-
ing dissected three-dimensionally and rain flutes are also 
forming on the higher parts of faces (Figure 12e), over 
time also dissecting the walls of rocky steps (Figure 12f). 
Channels are forming between the smaller tops dissected 
with rain flutes; water flows away from the tops along 
these channels (Figure 12g). We can trace the first stages 
Figure 13: (a) Solution pans on the bottom of denuded subsoil channels. Width of view is 1.5 m, (b) Rain flutes on the walls of funnel-like 
notch and mouth of the shaft, (c) Rock overgrown with moss. Width of view is 3 m, (d) Cups, developed bellow moss. Width of view is 3 m, (e) 
Overgrowing of denuded rock by moss. Width of view is 2 m, (f) Moss in the solution pans. Width of view is 0.75 m, (g) Rock top, covered by 
leaves. Width of view is 2 m, (h) Pits, formed bellow moss. Width of view is 4 m, (i) Several time denuded and overgrown top of the karren.
168 ACTA CARSOLOGICA 53/2-3 – 2024
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of the development which is described in the develop-
ment model of the shaping of a flat rock surface into rock 
spikes (Slabe et al., 2021). Funnel-like notches are form-
ing on the mouths of shafts and fissures with rain flutes in 
the higher part of the rim (Figure 12h).
On the densely cracked rock on the denuded ridges 
(Figure11a), which are being sharpened, rain flutes form 
instantly between the fissures (Figure 12i). Different sur-
faces are crisscrossed (Figure 12j).
The subsoil rock forms are gradually transformed. 
Some of the fissures are still filled, while the higher sur-
faces between them have been exposed (Figure 11r). 
The larger and denuded subsoil channels that are criss-
crossing the tops and whose cross-sections shaped as an 
upside-down omega are opening up, are deepened with 
a smaller channel (Figure 12k), or with a cascaded bot-
tom in the steep sections (Figure 12l), into which flows 
the water from the rain flutes that eventually dissect the 
walls of channels (Figure 12m). The channels between 
the ridges with rain flutes, which collect water, are like-
wise often transformed from subsoil ones; the wider ones 
are cascaded or are deepened with a smaller channel 
(Figure 12n). The bottoms of deeper and shady channels 
are overgrown with moss in some places (Figure 12o). 
The denuded subsoil cups (8h) transform into solution 
pans (Figure 12p) and when they open up, their walls are 
dissected by rain flutes (Figure 12q) and they can eventu-
ally transform into channels (Figure 12r). Solution pans 
also form on the bottoms of denuded subsoil channels 
(Figure 13a). Rain flutes are also dissecting the walls of 
subsoil funnel-like notches and shafts (Figure 13b).
Impact of vegetation and overgrowing moss
The roots and trunks of trees influence the formation of 
intrastratal holes, shafts, fissures and channels (Figure 
11d).
Under the thick vegetation the rock, which has al-
ready been shaped by rain in some places (rain flutes), 
is the most overgrown with moss (Figure 13c). In the 
overgrown parts of the rock the moss covers the entire 
surfaces of the larger tops; rounded cups can be seen 
below them (Figure 13d). Moss is also growing over the 
denuded subsoil forms (Figure 13e) beneath the vegeta-
tion and the shady parts of denuded subsoil cups on the 
bare rock, some of which have already been transformed 
into solution pans (Figure 13f), and of channels (Figure 
12o). Channels are forming on the walls below the tops 
overgrown with moss; they are caused by water secreting 
from the moss (Figure 13c). In the overgrown section of 
the karren the rock relief is also being reshaped under-
neath the decaying leaves (Figures 12g, 13g); the rock is 
overgrown with different lichens (Figures 12g, 12k, 12l, 
12o, 12p, 3b, 13f).
Pits are forming beneath the moss that covers the 
rock in some places (Figure 13h). The rock surface is 
smooth under the thicker layer of moss with soil un-
derneath, while the surface is finely dissected under the 
thinner layer of moss.
DEVELOPMENT MODEL
We can discern several most typical stages of karren devel-
opment. We can classify them into the development model 
that shows the transformation of gently sloping and vast 
rocky tops from flat surfaces to rock spikes (Slabe et al., 
2001). The three-dimensional, initially subsoil formation 
of karren, when intrastratal subsoil holes, shafts and fis-
sures were also created, was followed by the development 
of tops from subsoil ones to ones exposed to rain and 
trickling water. When they form on densely cracked rock, 
the tops are narrow, spiked or longitudinal ridges, which 
are at first dissected subsoil with funnel-like notches and 
wall channels, and later denuded and reshaped by rain 
flutes and the water trickling down the walls (Figure 8A).
Because the top rock beds are disintegrating or because 
they are denuded of soil, the vaster, gently sloping and 
denuded tops are being shaped by the sheet trickling of 
water that is hollowing out small steps (Figure 8B). Rain 
flutes are forming on the top edges and on some of the 
higher side edges. Subsoil rock forms are being trans-
formed: solution pans are created from subsoil cups; the 
funnel-like notches on the edge and the channels criss-
crossing the tops are deepening, with cascades created in 
the steep ones.
Afterwards, the tops become increasingly three-di-
mensionally dissected (Figures 8C, 12f). The subsoil rock 
forms are undergoing a great transformation: solution 
pans are opening up, with rock spikes and sloping sur-
faces forming between them; the walls of large steps, so-
lution pans, channels and the initially subsoil funnel-like 
notches are being dissected by funnel-like rain notches 
and rain flutes.
In the overgrown section, the rocky tops are cov-
ered with moss; in the denuded section of the karren, the 
moss is found only in the shade, i.e., in the fissures, deep 
channels and cups. The rock is being dissected also under 
the decaying vegetation. The rain flutes in the overgrown 
and in the predominantly moss-overgrown sections of 
karren indicate that the tops of karren were alternately 
overgrown and denuded on multiple occasions (Figure 
13i). The predominantly round shape of some of the de-
nuded sections of karren testifies to the fact that the re-
shaping caused by rain and trickling water was relatively 
short-term.
The karren were initially formed as subsoil karren. 
The vaster tops were dissected by subsoil cups and chan-
nels, and with funnel-like notches on the edges. Three-
ACTA CARSOLOGICA 53/2-3 – 2024 169
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
dimensional dissection was predominant on the densely 
cracked rock. The fissures spreading along vertical cracks 
and the subsoil shafts were crisscrossed with subsoil 
holes formed along bedding planes.
Small steps have formed on the vaster, flat and gen-
tly sloping tops, which were denuded of soil or as the top 
rock beds disintegrated; the steps are traces of the sheet 
flow, while rain flutes have formed on the top edges. 
Eventually the tops become three-dimensionally dissect-
ed and rain flutes form in all the higher sections and on 
the edges of steps. The stages of the development model 
of the dissection of such surfaces into rock spikes are be-
ing revealed (Slabe et al., 2021).
The exposed subsoil rock forms are being trans-
formed. Rain flutes are dissecting the walls of channels 
and funnel-like notches; solution pans are forming from 
subsoil cups, which over time open up; water is reshaping 
the wall channels. Smaller tops on the densely cracked 
rock are instantly dissected by rain flutes.
5. KARREN ON CLASTIC CARBONATES IN TOURRETTES-SUR-LOUP
SHAPE OF KARREN
Beds of Miocene carbonate sandstone and conglomerate 
have been deposited on the limestone folds on the slope, 
resembling a topping; their total thickness amounts to 
tens of metres. They are relatively impermeable and the 
water flowing downward has cut through the limestone 
folds below in several places, carving out smaller can-
yons.
The karren are domed. The top surfaces of the 
rounded masses of Miocene sandstone measure tens of 
metres or even 100 metres; along the rock beds, they dip 
in the same direction as the slope (Figures 14, 15, 16). At 
the edge, they turn into a rather steep step that reaches a 
height of ten metres in some places. Larger steps are usu-
ally made up of several smaller ones; some of them are 
overhanging. Steps can also be seen in the middle of the 
larger top surfaces of the karren, but they are generally 
lower. The karren were formed at the transition between 
rock beds. They were formed subsoil, underneath a thin 
layer of soil and vegetation, by water flowing down the 
slope. The denuded sections, in some cases measuring 
hundreds of square metres, are transformed by rainwater 
and by the water trickling down the surface of the rock. 
Only individual channels that dissect these sections are 
filled with soil and vegetation. Water can also flow onto 
them from under the soil covering the surface above 
them. The water flows into channels; in some places, stre-
ambeds are created (Figure 15) which pour over the edge 
in a waterfall, cutting deeper and deeper into the rock.
The larger areas have been affected by construction 
and water regulation. The water flowing along the top to-
wards the edge of the domed step has been diverted into 
channels and roads have been cut into them. Houses have 
been built into the overhangs of larger steps.
Figure 14: Karrren Tourettes sur 
Loup.
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Figure 15: Karren, dissected by 
channels and stream bed with wa-
terfall.
Figure 16: Rock relief of karren. a. subsoil channels, b. longitudinal notch, c. funnel-like notch, d. subsoil cup, e. cup under moss, f. pits, g. 
steps, h. rock rib. Locations of taken rock samples, numbers 1 to 23.
ACTA CARSOLOGICA 53/2-3 – 2024 171
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
Karren have developed on fine-grained Miocene 
carbonate sandstones and conglomerates. The shape of 
karren is mostly dictated by the rock, in addition to their 
development process. They have developed from subsoil 
karren. A thorough examination of the karren rock relief 
and of the rock on which they were created explains how 
they have formed and developed.
It is the first description of the development of kar-
ren formed on this type of rock, which uniquely influ-
ences the shape and development of karren.
A settlement has developed on the domed and 
stepped karren; within the settlement, individual areas 
have been denuded, in particular the largest steps and the 
rock surrounding them.
GEOLOGY
Macroscopic description
In this rock outcrop we examined the clastic sedimen-
tary rock, i.e., molasse, which consists of multiple rock 
sequences. In the selected 15 m tall geological profile, 
layers of sandstone and conglomerate alternate, laterally 
transitioning from one lithological type to the other. The 
bedding planes in the rock are not clearly discernible and 
it is difficult to clearly define the discontinuity surfaces. 
In some places, the outcrop could be described as mas-
sive or thick-bedded rock, whereas in other places we 
could laterally predict poorly expressed layers, around 
10 cm thick. The profile contains a few heavily karstified 
sedimentation contacts. The rock is homogeneous, hard, 
compact, yet considerably porous. The dip angle of the 
denuded and karstified rock is generally between 320/10 
and 330/12. The rock colour alternates between dark yel-
lowish orange (10YR 6/6), pale yellowish brown (10YR 
6/2) and pale brown (5YR 5/2). We took 23 rock samples 
in the vertical direction at relatively even intervals.
Microscopic description
We turned the 23 rock samples into 29 microscope slides, 
i.e., thin sections. Due to the porosity that was visible 
macroscopically during sampling, and to achieve bet-
ter visibility during subsequent microscopy, we injected 
blue epoxy resin into rock slices that had been prepared 
for attachment to the glass of microscope slides. Some 
samples contained multiple cracks; the epoxy resin 
(Gardner, 1980) further strengthened the rock in those 
areas, preventing it from disintegrating when making the 
thin section. In the examined profile we microscopically 
determined three lithological types, namely sandstone in 
the lower (samples TSL1–TSL4) and upper part of the 
profile (TSL13–TSL23), and conglomerate in the middle 
part (samples TSL5–TSL12). Both sandstone types have 
the same properties.
The sandstone samples are made up of more or less 
evenly sized detrital rock fragments (Figure 17a, c; sam-
ple TSL22). Predominant in the rock are inorganic grains 
of dolomite and non-carbonate grains; calcite grains con-
stitute only a few percent. The dolomite grains are evenly 
distributed throughout the rock, with no apparent pat-
tern. They are mostly angular or slightly rounded, all with 
cross-sections between 0.1 and 0.4 mm. According to the 
complexometric analysis, they make up less than 14%. 
The amount of non-carbonate grains is similar. These 
likewise have no apparent pattern and are evenly distrib-
uted. Most of them are rounded and smaller, usually with 
diameters between 90 and 180 µm. Calcite almost always 
appears in the rock as the fine-grained cement of the 
above-mentioned grains, i.e., as drusy sparry calcite. The 
rock also contains individual bioclasts, including num-
mulites, operculinas, miliolids, foraminifera, fragments 
of algae and of unidentifiable bivalves. The bioclasts are 
likewise calcite and make up less than one percent of the 
rock. Porosity is both intergranular and intragranular. 
Intergranular porosity has been made even more visible 
in the microscope slide through impregnation with blue 
epoxy resin. Intragranular porosity is noticeable in the 
chambers of larger fossils. This lithological type does not 
really contain any typical cracks in the rock.
Conglomerate samples are made up of the same 
detrital grains or rock fragments as the sandstone, only 
larger (Figure 17b, d; sample TSL6). Dolomite grains are 
predominant, making up more than half of the rock. In 
terms of quantity, they are followed by carbonate frag-
ments of various limestones, whereas non-carbonate 
grains or rock fragments with no identifiable internal 
structure make up just over 10%. The dolomite frag-
ments are made up of xenotopic dolomite with mostly 
anhedral crystals, which often laterally transition into 
hypidiotopic and idiotopic dolomite with subhedral and 
euhedral crystals. The dolomite fragments of baroque 
type and mostly unimodal crystal size have diameters 
between 1 and 5e, while the dolomite grains in the con-
glomerate have diameters between 2.2 and 4.5 mm on 
average. Among the limestone calcite grains in the rock 
are micrite grains, pelsparite grains, and grains contain-
ing different fossil fragments. The rock also contains 
fragments of larger bivalves as individual grains in the 
conglomerate. Dedolomite crystals are clearly visible in 
one of the limestone grains. The diameters of limestone 
fragments are, on average, somewhat smaller than the 
dolomite ones – between 1.1 and 2.3 mm. Non-carbonate 
grains make up around 10%. Primary porosity is mainly 
intergranular. The fine-grained cement of rock fragments 
in the conglomerate is drusy sparry calcite, just as in the 
sandstones. This lithological type does not really contain 
any typical cracks in the rock either.
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KARREN OF PROVENCE (FRANCE), GRÉOLIÈRES, CAUSSOLS, TOURRETTES-SUR-LOUP AND LUBERON
Complexometric analyses
A complexometric analysis was performed on each rock 
sample (Table 3). The sandstone samples in the lower 
part of the profile have an average calcite content of 
46.6%, dolomite content of 49%, insoluble residue con-
tent of 4.2%, and total carbonate content of 95.8%. The 
sandstone samples in the upper part of the profile have 
an average calcite content of 68.9%, dolomite content of 
16.7%, insoluble residue content of 14.3%, and total car-
bonate content of 85.7%. The conglomerate samples have 
Figure 17: (a) Rock slice prepared 
for a thin section, sample TSL22. 
Blue epoxy resin injected. Width 
of view is 4 cm, (b) Rock slice pre-
pared for a thin section, sample 
TSL6. Blue epoxy resin injected. 
Width of view is 4 cm, (c) Thin sec-
tion of sample TSL22. Blue epoxy 
resin injected. Lower half of sample 
was dyed in alizarin red dye. Width 
of view is 4 cm, (d) Thin section of 
sample TSL6. Blue epoxy resin in-
jected. Lower half of sample was 
dyed in alizarin red dye. Width of 
view is 4 cm.
Table 3: Complexometric analyses of rock samples from Tourettes sur Loup.
Rock sample CaO (%)
MgO 
(%)
Calcite 
(%)
Dolomite 
(%)
Total 
carbonate 
(%)
CaO/MgO
Insoluble 
residue
(%)
TSL 1 39.93 12.34 40.65 56.43 97.08 3.24 2.92
TSL 2 38.08 13.71 33.94 62.70 96.64 2.78 3.36
TSL 3 43.41 7.78 58.16 35.59 93.75 5.58 6.25
TSL 4 42.85 9.15 53.76 41.86 95.62 4.68 4.38
TSL 5 39.09 3.83 60.26 17.52 77.78 10.21 22.22
TSL 6 35.78 11.93 34.22 54.59 88.81 3.00 11.19
TSL 7 34.83 4.92 49.95 22.50 72.45 7.08 27.55
TSL 8 40.38 10.16 46.85 46.47 93.32 3.97 6.68
TSL 9 42.73 8.18 55.93 37.44 93.37 5.22 6.63
TSL 10 43.29 8.47 56.25 38.73 94.98 5.11 5.02
TSL 11 45.65 7.80 62.10 35.69 97.79 5.85 2.21
TSL 12 44.98 6.05 65.27 27.66 92.93 7.43 7.07
TSL 13 46.52 5.62 69.05 25.73 94.78 8.28 5.22
TSL 14 45.99 6.01 67.17 27.48 94.65 7.65 5.35
TSL 15 45.87 6.77 65.05 30.98 96.03 6.78 3.97
TSL 16 45.48 4.76 69.37 21.76 91.13 9.55 8.87
TSL 17 44.64 2.82 72.66 12.91 85.57 15.83 14.43
TSL 18 43.74 2.62 71.56 11.99 83.55 16.69 16.45
TSL 19 39.37 1.01 67.77 4.61 72.38 38.98 27.62
TSL 20 39.26 1.17 67.17 5.35 72.52 33.56 27.48
TSL 21 43.69 1.41 74.48 6.45 80.93 30.99 19.07
TSL 22 38.53 1.69 64.55 7.75 72.30 22.80 27.70
TSL 23 44.36 3.02 71.66 13.83 85.49 14.69 14.51
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MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
an average calcite content of 52.2%, dolomite content of 
36.1%, insoluble residue content of 11.6%, and total car-
bonate content of 86.4%. The samples of the entire profile 
have an average calcite content of 62.2%, dolomite con-
tent of 26.5%, insoluble residue content of 11.3%, and to-
tal carbonate content of 88.7%.
Impact on karstification
The entire profile of the rock, i.e., all the layers, react 
similarly to karstification. The sandstone is fine-grained, 
while the conglomerate contains slightly larger grains; 
despite their porosity, both are homogeneous, compact, 
and hard. Their carbonate content is almost 89%. Both ex-
amined rocks have excellent properties; on them, subsoil 
and rain rock features can develop efficiently, smoothly, 
and successfully, except for the smallest features, i.e., rain 
flutes, due to the composition and disintegration of the 
rock. The porosity of the rock and the fine-grained calcite 
cement further accelerate karstification.
ROCK RELIEF
The surface karren have developed from subsoil karren. 
Most of them are covered by a thin layer of soil and vege-
tation. Subsoil channels (Figures 14, 15, 16a) have formed 
beneath the soil, dissecting the karren into rounded rock 
ribs, elongated in the dip direction. The channels are ei-
ther separate or, especially in the upper section, merged 
into branches. The largest ones are several metres wide 
and relatively shallow. In some places, large, elongated 
notches have formed with channels at the bottom. Some 
of these notches beneath the edge of the soil and vegeta-
tion cover and on the widened, more gently sloping sec-
tions (Figure 18a) are still filled, while the rock ribs in 
between are already bare. The fragments splitting from 
the bare rock are transported by water and deposited on 
the more gently sloping sections, where soil also accumu-
lates. Therefore, the subsoil cups are also formed in other 
ways, not just by corrosion underneath the remains of 
the original soil cover.
The rock beneath the steps, which have formed in 
the middle of the top of the karren at the transition from 
the top bed to the bed below, is often covered by soil. 
Longitudinal notches (Figures 16b, 18b) have formed 
alongside it, and funnel-like notches (Figures 16c, 18c) 
at the end of the channels. They can be a metre wide or 
wider and relatively shallow.
In some places where the soil and vegetation cover 
the rock, subsoil cups (Figure 16d) have formed. The di-
ameter of the relatively shallow cups is in the centimetre 
to metre range. Their rims are of different shapes, de-
pending on the cover. They are either round or dissected 
(Figure 18d). Most of them are located at the edge of the 
soil cover (Figure 18e), which is either washed away or 
deposited by water. In the areas containing several cups, 
a network of channels has formed between them, with 
diameters in the centimetre range (Figure 18e).
Lower down the top surface of the karren we can see 
individual cups, usually created where the rock is cor-
roded and dissected at the contacts between beds (Figure 
18f), and where it transitions into denuded subsoil chan-
nels, transformed by rain and trickling water (Figures 
18a, 18g). They are also found at the bottom of funnel-
like notches on rock steps (Figure 18h).
Relatively large areas of the rock surface are covered 
by moss. The diameters of moss rhizoids are in the cen-
timetre and decimetre range. There are either individu-
al mosses or, as is most often the case, clusters of them 
(Figure 18i), some of which measure several metres in 
diameter. Such surfaces are most often the slopes of rock 
ribs above larger water channels, especially those on the 
shady side (Figures 14, 18j). Moss clusters are often ar-
ranged in the zones of steep and mostly overhanging 
parts of steps, which have formed at the transitions be-
tween rock beds (Figures 14, 15, 18k). They are also lo-
cated at the edges of solution pans. It appears that small 
cups have also formed under the moss, in the centimetre 
size range. Their bottoms are dissected by even smaller 
cups (Figures 16e, 18l). Apparently, the moss is causing 
or at least accelerating more pronounced splitting of the 
rock, as the majority of fresh fractures are located in the 
areas with moss clusters (Figures 18i, 18k, 18m). The 
scales are the same size as the moss rhizoids. Thus, the 
scales measure 20 cm in diameter, or most often less than 
that, and are up to a centimetre thick; only the largest 
ones are thicker. The rock is weathering and splitting un-
der the moss. The water trickling down the surface of the 
rock transports the scales downward into the channels 
and gradually crushes them into sand.
There are gently sloping pits (Figures 16f, 18n) on 
the vertical and overhanging surfaces, i.e., on the walls of 
the karren that are transverse to the beds of porous rock. 
Their diameters and lengths are in the centimetre range. 
Parts of the rock are densely pitted in the horizontal 
zones of more porous beds. They appear to have formed 
on the surface, meaning that they are being hollowed out 
by the water trickling down the wall. Is the rock porous 
enough for water to percolate through it?
Small hollows (Figures 18n, 18o) are generally 
formed at the contacts between rock beds. Their diam-
eters range from one centimetre to several decimetres. 
There are wall channels below some of these hollows, 
created by the water flowing out of them. They are usu-
ally single channels, while several smaller channels can 
sometimes be seen below the wider small hollows (Fig-
ure 18p). That is why the bottom parts of the small hol-
lows are often deepened.
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Figure 18: (a) Subsoil shaping of the channel, (b) Along-sediment notch, (c) Funnel-like notch, (d) Subsoil cups, (e) Subsoil cups. Width of 
view is 2 m, (f) Subsoil cups. Width of view is 3 m, (g) Subsoil cups, (h) Subsoil cups, (i) Moss on the rock. Width of view is 5 m, (j) Moss 
on the shadow part of the rock surface, (k) Moos on the wall horseshoe notch on the end of rock layer. Width of view is 0.75 m, (l) Splitting 
of the rock under moss. Width of view is 0.5 m, (m) Splitting of the rock under moss. Width of view is 3 m, (n) Wall pits. Width of view is 4 
m, (o) Wall hollows and pits, (p) Hollow with channels. Width of view is 0.75 m, (q) Steps on the steep wall. Width of view is 4 m, (r) Steps 
in the stream bed. Width of view is 5 m.
Well-developed large and small steps (Figure 16g) 
can be seen on the gently sloping, flat and gently rounded 
surfaces, and on the steeper surfaces shaped by the sheet 
flow. The large steps (in the decimetre to metre size range) 
are formed at the transitions between rock beds (Figures 
14, 15, 16). They dissect the gentle slopes and the steep 
slopes. The steep slopes of large steps are often dissected by 
smaller steps, placed one above the other in longitudinal 
rows (Figure 18q). The most pronounced angular edges 
and relatively large level tops can be seen on the small steps 
that have formed along thin (centimetre-wide) rock beds 
in the bed of the stream that is cutting away the top of the 
karren (Figure 18r). They are arranged one above the other 
in the form of scales, and their edges on the inflow side are 
curved inward. The unique shape of the steps is the result 
of a larger and stronger flow of water.
The medium-sized steps, up to a decimetre high, 
have been created where the rock is disintegrating due 
to biocorrosion underneath the moss (Figures 18i, 18j, 
18l, 19a). The splitting sites, which are predominant in 
some places, especially on the steep, usually most over-
grown sections of the rock, are being transformed by the 
sheet flow. There, steps are even more pronounced. Moss 
is also growing over the steep parts of larger steps, often 
creating overhanging walls. Higher steps are usually lo-
cated in the steeper areas of the surface.
The smallest steps (Figure 19b), in the centimetre 
size range, are traces of an even trickling of the sheet flow 
along the coarse surface of the rock, which is not directly 
reached by rainwater (Knez et al., 2015). They are formed 
on surfaces with varying gradients – on the top surfaces 
with a gentle slope and on the steep edges. Most of them 
have round edges on the inflow side. At the bottom of the 
steps, especially the larger ones, we often find a shallow 
cup which retains water for a longer period of time. It is a 
composite form somewhere between a step, hollowed out 
by the sheet flow, and a solution pan. A distinct network 
of steps, usually arranged in a cascade, dissects the bot-
toms of channels (Figures 18g, 18h, 18j, 19c); these chan-
nels collect water from the dissected surface or water 
from the soil and vegetation cover. The steps are often as 
wide as the bottom of the channel. The larger ones have 
been deepened in some places to form a solution pan or 
a smaller pothole. Less pronounced steps can be seen in 
the smaller, higher areas.
Gradation is therefore dictated by stratification, 
biocorrosion-induced erosion, the coarseness of the rock 
and by the predominant factor shaping the rock, i.e., 
the sheet flow. The latter flows into the subsoil-formed 
or young channels that collect rainwater; it also flows 
directly and evenly onto the edge of the karren (Figure 
19d). The channels intertwine in different ways. The rock 
is impermeable, which is why the amount of water that 
is shaping it evenly and then merging it into channels is 
relatively large.
It seems that rain flutes cannot form on such a coarse 
surface, which is mostly the result of the rock composi-
tion. The formation of rain flutes can also be influenced 
by time, e.g., if the rock has only recently been denuded, 
and by a predominant sheet flow.
Channels are the most typical form on the denuded 
rock on the top surface of the karren. These uncovered, 
yet subsoil-formed channels are described above.
Another type is a channel shaped by water that flows 
from the soil and vegetation cover if it covers the top part 
of the karren, while the bottom part, which often has a 
higher gradient, has already been denuded. The densest 
network of such smaller (with diameters in the centime-
ACTA CARSOLOGICA 53/2-3 – 2024 177
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
Figure 19: (a) Steps bellow moss. Width of view is 5 m, (b) Steps under layer of trickling water. Width of view is 1 m, (c) Steps in the channel. 
Width of view is 1.5 m, (d) Steps under layer of trickling water. Width of view is 1.5 m, (e) Net of shallow channels, (f) Channels.
tre range) and meandering channels (Figures 18e, 19e) is 
created on gently sloping surfaces below the edge of the 
cover, which is often dissected into smaller areas of soil 
and vegetation, with subsoil cups forming underneath. 
The larger channels with diameters in the decimetre range 
are straighter. When the surface below the cover is steep, 
the channels are straight and can merge lower down, es-
pecially in funnel-like notches (Figure 18h). They are also 
formed under surfaces partly covered by soil and vegeta-
tion in the bottom part of the karren, which is otherwise 
mostly denuded. They often deepen the bottoms of larger, 
originally subsoil-formed channels and notches. The lat-
ter continue upwards beneath the soil cover, from where 
water is already flowing into them (Figure 14).
A level surface can be formed subsoil or a surface 
dissected by large channels, with rounded rock ribs in 
between (Figure 16h). Water trickles down the steps in 
a sheet flow along the denuded, relatively level or evenly 
rounded rock surface. Eventually, the denuded rock is in-
creasingly dissected and the water merges into currents 
178 ACTA CARSOLOGICA 53/2-3 – 2024
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in the lower-lying areas. Relatively wide and shallow 
channels are formed, which meander on gently sloping 
surfaces and are dissected by steps (Figures 19c, 19f). A 
dense network of such channels is created (Figures 14, 
15, 20a). In the steep sections, especially on the edges of 
large steps, the channels are straight, narrower and deep-
er (Figures 14, 18h, 18o). Afterwards, the main water 
collectors are formed, namely larger and straighter chan-
nels (Figure 20b), which have diameters in the decimetre 
range and can be tens of metres long; their bottoms are 
often relatively wide, flat and smooth (Figures 18j, 20b). 
On the subsoil-dissected surface this role is taken up by 
the former subsoil channels.
The formation of channels is therefore generally a 
combination of different factors – of the water flowing 
underneath the soil and of the rainwater either directly 
reaching the rock or trickling in a sheet flow or stream 
across the surface and, of course, of the development or 
denudation of the rock.
The largest funnel-like notches, whose diameters 
reach several metres, are subsoil-formed notches created 
along the main subsoil channels that dissect the tops of 
karren into rock ribs (Figures 14, 15). They were created 
when they were either fully underground or when only 
their bottom part was; when the bottom ledge (Figures 
16c, 18c) is covered by soil and the water flows to it along 
the channel that dissects the bare rock, or when the rock 
above the ledge is covered and the water flows from the 
soil over the edge. Apart from the latter, such notches are 
relatively wide. The denuded notches have been trans-
formed. There is usually a channel at their bottom that 
deepens them and, in some places, also widens their bot-
tom part. As a rule, smaller notches are formed along 
younger channels that collect water from the bare rock 
and from the soil that covers the top part of the rock. 
They can be dissected by smaller channels (Figure 18h) 
leading to the bottom of the notch, from where one wall 
channel leads onward. Their diameters are in the centi-
metre to decimetre range. Both are co-shaped by rain-
water that reaches them directly. Eventually, smaller rock 
steps cut through it, creating a flat-bottomed channel, 
with the notch becoming its high walls. The most dis-
tinct notch can be seen at the top of the waterfall, where 
a water-rich stream flows down (Figure 15).
This relatively common rock form has resulted in 
genuinely jagged rock overhangs, both those at the edge 
and the smaller ones on top of the karren (Figure 14).
Wall channels can be seen below the funnel-like 
notches; on the overhangs these channels widen into a 
bell shape (Figure 14).
The solution pans are of different origins and their 
diameters are in the centimetre to metre range. Smaller 
solution pans are predominant or shallow ones if they 
have larger diameters, which indicates their recent for-
mation, or the recent relatively even shaping of the rock 
beneath the soil and vegetation cover. They develop from 
denuded subsoil cups (Figure 18d), from small biocorro-
sion cups, and due to water being retained on the coarse 
rock, on larger steps and in channels (Figures 18g, 19c). 
The latter can be singled out as a special type of solution 
pan. They are often a composite rock form combined with 
a pothole; they are largest in the larger channels. They 
are occasionally shaped by erosion as the water swirls, 
gathering the sand that has been created by rock splitting. 
Where larger periodic streams flow, the diameter of solu-
tion pans exceeds one metre. In the section of the rock 
that is dissected by larger steps, i.e., usually in shallow 
channels, we find solution pans that are also mostly shal-
low and of different shapes, arranged one above the other 
in a cascade. They are wider on the inflow side and nar-
rower on the outflow side. Their diameter ranges from 
one centimetre to several decimetres. The solution pans 
that are developing from small biocorrosion cups, which 
were formed beneath the moss, at first consist of several 
smaller cups with diameters in the centimetre range (Fig-
ure 18l).
Figure 20: (a) Branching web of channels, (b) Larger channel in with contributory from smaller channels.
ACTA CARSOLOGICA 53/2-3 – 2024 179
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
DEVELOPMENT MODEL
In terms of composition, the relatively uniform, un-
cracked, stratified and rather impermeable rock mass is 
dissected beneath the soil by subsoil channels, most of 
which individually dip in the same direction as the rock 
bed. Only in the upper part do they merge into a larger 
channel. Notches are created along the larger channels 
and if the channels are close by, then rounded rock ribs 
are formed in between. The larger surfaces without any 
distinct channels are relatively level.
Where the rock has been denuded, the top of the 
karren, apart from the channels, is shaped by sheet flow. 
Steps are formed. Eventually, a network of smaller chan-
nels develops. They often funnel into a larger channel and 
merge with the large channels formed beneath the soil. 
Funnel-like notches are growing at the edges of the kar-
ren or at the ends of the channels, followed by wall chan-
nels below them (Figure 14).
In the case of gradual denudation, the water flows 
from the soil at the top mostly in a condensed manner 
along smaller and larger channels (Figure 19e). These 
channels join a network of rain channels (Figure 20a).
The tops of the karren are relatively poorly dissect-
ed, so it can be assumed that they have been denuded 
recently.
The karren are dissected three-dimensionally only 
by individual small hollows formed along bedding planes.
The development model can be defined as typical of 
the recent formation of gently sloping surfaces of rock 
being denuded of soil (Knez et al., 2011, 2015). In this 
case, the shape is also influenced by stratification, com-
position, the rare cracks in the rock, the moss growing 
over it, and the disintegration taking place under the 
moss. The bumps between the channels are rounded and 
the rock surface is coarse. It appears that rain flutes do 
not form on such rock.
The characteristics of the “plastically” deposited 
sloping, uniquely composed and predominantly un-
cracked beds of Miocene carbonate sandstones, which 
have a major impact on the formation of karren, are 
intertwined with the typical rock relief development 
model, which reveals a transition from subsoil forma-
tion to denuded rock exposed to rain. Rock denudation 
is gradual and the water often flows onto the bare rock 
from the soil covers. The bare, sloping peaks reveal the 
characteristic formation of a slightly inclined and rela-
tively smooth rock. Such surfaces are initially shaped by 
sheet flow; steps are a characteristic trace of that. As the 
surface is being dissected, the water begins to merge into 
streams and channels are formed. Along these channels, 
the rock is becoming increasingly dissected. That indi-
cates the initial stage of the formation described above. 
The composition of the rock that is splitting, especially 
under the moss, does not enable the development of the 
smallest rock forms, such as rain flutes, whereas its split-
ting causes the development of rounded peaks.
The special features of karren formation on this 
unique rock within an otherwise typical development 
model are broadening our understanding of the forma-
tion of the rocky karst surface.
6. KARREN OF LUBERON
We have supplemented our study of the formation of kar-
ren on the Miocene carbonates of Tourrettes-sur-Loup 
with research of the most characteristic rock forms and 
rock relief of Luberon.
Most of the surface is covered by soil and vegetation. 
Hence, the subsoil rock relief is predominant. The newly 
denuded rock surface is smooth and rounded (Figure 
21a). The edges of steep slopes, of the rocky walls of val-
leys, and of cuttings are being denuded and the subsoil 
rock relief is being reshaped. The majority of subsoil rock 
forms on steep surfaces are large subsoil channels (Figure 
21b). Sediment is accumulating below the denuded steep 
sections, with subsoil cups (Figure 21c) and solution 
pans (Figure 21d) forming underneath the sediment.
There are cups (Figure 21e) on the overhanging 
walls that only a small amount of water reaches. The rock 
is flaking (Figure 21f). Crust forms on the rocky surface 
that is reached by greater quantities of water.
The characteristic and most distinct rock relief dis-
sects the rocky walls and steep slopes. It is mostly made 
up of wall channels (Figures 22a), into which water flows 
from the overgrown surface. These are individual chan-
nels that are dependent on the inflow of water. They are 
often found along cracks and crevices (Figure 22b) or 
bedding planes (Figure 22c). Typical rain flutes (Figure 
22d) form on the uncracked rock that is directly exposed 
to rain. These rain flutes are interconnected into a net-
work.
The denuded walls are often dissected by hollows in 
the centimetre size range (Figure 22e) or in some places 
by larger ones, with diameters in the decimetre range 
(Figure 22f). They are traces of the point-accelerated dis-
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solution and disintegration of the rock and of the form-
ing of a crust on the rocky surface surrounding them.
The soft rock that was used for construction re-
shapes quickly, as attested by the dissected walls of the 
14th-century Palace of the Popes in Avignon. Channels 
have formed on the walls, with water running down them 
from the top (Figure 23a). Beneath the moss, the rock is 
dissected by cups (Figure 23b). The rock is disintegrating 
quickly in the spots that water does not reach (Figure 24).
Subsoil cups filled with sediment and soil (Figure 
25a), solution pans (Figure 25b) and channels are devel-
oping on artificially uncovered layers on the gently slop-
ing surfaces at Fort Buoux (in the middle of Luberon), 
which began construction in the 11th century, with the 
majority of traces dating from the 13th century, while the 
oldest ones’ date back to the Bronze Age. The channels 
are also found on the walls (Figure 25c). The rock is also 
being distinctly dissected under the moss (Fig. 1904).
Large solution pans (Figure 25d) have also formed 
on the denuded rocky peak above Saignon.
Figure 21: (a) Subsoil rounded and smooth rock surface, (b) Subsoil channels. Width of view is 4 m, (c) Subsoil cup. Width of view is 2 m, (d) 
Solution pan, (e) Wall cups, (f) Splitting of the rock. Width of view is 1.5 m.
ACTA CARSOLOGICA 53/2-3 – 2024 181
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
Figure 22: (a) Wall channels, (b) Wall channels along fissures, (c) Wall channels along bedding-planes, (d) Rain channels, (e) Wall pits, (f) 
Wall cups.
Figure 23: (a) Wall channels, (b) Cups bellow moss. Width of view is 1 m.
182 ACTA CARSOLOGICA 53/2-3 – 2024
KARREN OF PROVENCE (FRANCE), GRÉOLIÈRES, CAUSSOLS, TOURRETTES-SUR-LOUP AND LUBERON
Figure 24: Decaying rock.
Figure 25: (a) Subsoil cups. Width of view is 3 m, (b) Solution pans. Width of view is 4 m, (c) Wall channels, (d) Solution pans.
ACTA CARSOLOGICA 53/2-3 – 2024 183
MARTIN KNEZ, TADEJ SLABE & PHILIPPE AUDRA
7. CONCLUSION
The karren of Gréolières and Caussols are developing on 
similar rock and under similar conditions. What differs, 
however, is the dip and thickness of the rock strata. This 
also dictates the shaping and development of their rock 
relief. Parallel channels are predominant on the steep 
slopes of Gréolières on fine-grained homogeneous and 
compact thick-bedded limestone with almost entire cal-
cium carbonate content. On the flat and steep surfaces, 
the abundant water flow splits into parallel branches. 
They are gradually reshaped three-dimensionally. The 
rain flutes, which are initially characteristic of the upper 
parts of surfaces that are directly reached by rain, even-
tually also dissect all the larger channels and the surface 
between them. The surfaces of the tops of the karren of 
Caussols on the likewise fine-grained, homogeneous and 
compact limestone with a high calcium carbonate con-
tent, which are more gently sloping and flat due to the 
denudation of soil or the disintegration of older rock lay-
ers, are initially dissected into steps by the sheet flow. The 
water also reshapes the denuded subsoil channels, and 
solution pans form from subsoil cups. Afterwards, the 
surface is dissected three-dimensionally. Rain flutes also 
form on the walls of the above-mentioned rock features 
and of the funnel-like notches at the edges. Three-dimen-
sional dissection prevails on the densely cracked parts of 
the rock strata. Examples of such karren formation have 
been described in the development model (Slabe et al., 
2022).
The karren of Tourrettes-sur-Loup where homo-
geneous, compact, hard, and partly porous fine-grained 
sandstone alternates with conglomerate, with the frag-
ments bound together by fine-grained calcite cement 
are dissected by large channels which collect most of the 
water that trickles downward. They are created subsoil 
but are later reshaped into denuded channels. They are 
constantly deepening and the surfaces between them are 
being reshaped accordingly. The rock enables the devel-
opment of such channels, as it is mostly secondarily im-
permeable and three-dimensional dissection is therefore 
less distinct. Smaller rock features, such as rain flutes, do 
not form on such rock. The rock is also flaking.
Thus, all karren are formed from subsoil ones 
through gradual denudation. The subsoil rock relief is 
reshaped by rainwater, by the water flowing across kar-
ren, and by biocorrosion. The first two examples of kar-
ren differ mostly because of the dip and thickness of the 
strata of similar rock, while the third example is unique, 
as karren form on a completely different type of rock.
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 RE-
SEARCH INFRASTRUCTURE FOR THE INTERNA-
TIONAL COMPETITIVENESS OF THE SLOVENIAN 
RRI SPACE – RI-SI-EPOS” and “DEVELOPMENT OF 
RESEARCH INFRASTRUCTURE FOR THE INTER-
NATIONAL COMPETITIVENESS OF THE SLOVE-
NIAN RRI SPACE - RI-SI- LifeWatch”; both operations 
are co-financed by the Republic of Slovenia, Ministry of 
Education, Science and Sport, the European 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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http://www.dlib.si/details/URN:NBN:SI:doc-
W7VPJ05Q, DOI: 10.3986/ac.v50i2-3.9308
ACTA CARSOLOGICA 53/2-3 – 2024 185