GEOMORPHOLOGICAL ANALySIS OF KARST LANDFORMS  
AT THE mASSO dELLA VECChIA GEOSITE  
(SALENTO PENINSULA, ITALy)
GEOMORFLOšKA ANALIZA KRAšKIH OBLIK NA OBMOČJU 
mASSO dELLA VECChIA  
(POLOTOK SALENTO, ITALIJA)
Paolo SANSÒ1
Izvleček UDK  551.435.8(450.75)
Paolo Sansò: Geomorfološka analiza kraških oblik geozname�
nitosti Masso della Vecchia (polotok Salento, Italija)
Prisotnost matične kamnine, ki jo krajevno imenujejo masso 
della Vecchia, je pomembna geološka zanimivost v okolici vasi 
Giuggianello (polotok Salento, Apulija, Italija). Zaradi nena-
vadne naravne reliefne oblike te kamnine in mnogih drugih 
podobnih kamnin, ki se pojavljajo na tem območju, so nastali 
številni miti in legende. Naredili smo podrobno geomorfološko 
analizo masso della Vecchia. študijsko območje je okoli 100 m 
nad morjem na abrazijskem območju iz spodnjega pleistocena, 
ki je pravzaprav vrh morfostrukturnega grebena Serra di Po-
ggiardo. Krajevno se iz kamnin miocenske starosti na površju 
pojavlja Pietra Leccese. Sestavljen je iz slabo strjenih, biotu-
rbacijskih rumenkastih biomikritov, ki se na nižjih ravneh 
hitro vzpenjajo v masivni grainstone, bogat z mineralom 
glavkonita. Celotna sekvenca je rahlo nagnjena proti severov-
zhodu. Geomorfološka analiza je pokazala, da so masso della 
Vecchia in podobne reliefne oblike, ki se pojavljajo na območju, 
kraške in da so nastale pod pokrovom prsti. Prepoznali smo 
vrhove, kanale, zareze, podtalne fasete, polzvonove in druge 
tipične oblike. Svojevrsten skupek podtalnih kraških oblik je 
mogoče razložiti z upoštevanjem geološke strukture, podtalnih 
kraških procesov in geomorfološkega razvoja tega območja v 
času poznega pleistocena.
Ključne besede: podtalne škraplje, naravna dediščina, Salento, 
Italija.
1 Di.S.Te.B.A., Università del Salento, Italy, e-mail: paolo.sanso@unisalento.it
Received/Prejeto: 04.05.2016
COBISS: 1.01
ACTA CARSOLOGICA 46/1, 7–18, POSTOJNA 2017
Abstract UDC  551.435.8(450.75)
Paolo Sansò: Geomorphological analysis of karst landforms 
at the Masso della Vecchia geosite (Salento peninsula, Italy)
The presence of a pedestal rock, locally named masso della 
Vecchia, marks a site of relevant geological interest (geosite) 
in the surrounding of Giuggianello village (Salento Peninsula, 
Apulia region, Italy). This unusual natural landform and simi-
lar others occurring in the same area gave birth to myths and 
legends. A detailed geomorphological analysis of masso della 
Vecchia area has been carried out. The site is placed at about 
100 m of altitude on a lower Pleistocene abrasion surface which 
constitutes the top of the Serra di Poggiardo morphostructural 
ridge. Locally, the Miocene Pietra Leccese Formation crops out. 
It is constituted by poorly consolidated, bioturbated, yellowish 
biomicrites at lower levels rapidly grading upward in massive 
grainstones rich in glauconite minerals. The entire sequence 
gently dips northeastward. The geomorphological analysis re-
vealed that the masso della Vecchia and similar landforms oc-
curring in the area are karstic features produced under a soil 
cover. Pinnacles, channels, notches, subsoil scallops, half-bells 
and other typical features have been recognized. The peculiar 
assemblage of subsoil karst features can be explained taking 
into account the geological structure, subsoil karst processes 
and the geomorphological evolution of this area during the 
Late Pleistocene.
Key words: subsoil karren, geoheritage, Salento, Italy.
INTRODUCTION
A natural monument marks a site placed in the surround-
ing of Giuggianello, a small village of southern Salento 
(Apulia region) (Fig.1). It is constituted by a pedestal 
rock called by local people “lu furticiddhu de la vecchia 
de lu manni” (i.e. the spindle used by a witch to make 
yarn) or more simply “masso della Vecchia” (i.e. the large 
ACTA CARSOLOGICA 46/1 – 20178
PAOLO SANSÒ
block of the witch). Numerous local legends arouse from 
the occurrence of this unusual landform.
De Simone (1867) reported for the first time the 
presence in the Salento peninsula of this mushroom-like 
rock, even if he wasn’t able to indicate precisely its posi-
tion. Maggiulli (1871) considered it a megalithic monu-
ment whereas Botti (1871) referred its origin to weather-
ing processes reporting examples of similar landforms in 
Italy (“pile di formaggio” at Elba island, “pietra ballerina” 
near Nuoro, Sardinia) and in Europe (Central Massif of 
France, “cheesewring” in Cornwall, “herkulessaulen” at 
Bielagrund, Switzerland).
According to De Simone (1872) this singular rock 
would be that one quoted by Aristotelis’ “de mirabilibus 
Auscultationibus” reporting the legend that this heavy 
block was thrown away by Hercules in his fierce battle 
against Giants. This author accurately describes the size 
of masso della Vecchia mushroom-like rock shaped on 
the Tertiary Pietra Leccese Formation. The pedestal is 
2.75 m high and supports a block showing a perimeter 
15.60 m long, long axis 5.70 m and short axis 2.85 m; the 
block thickness at its centre is about 2.30 m (Fig. 2).
Other unusual rocks can be found in the area. De 
Simone (1872) noted that in the same place another 
mushroom-like rock, more than twice larger than the 
masso della Vecchia, was broken in piece by a mine few 
years before. Finally, the author informs readers that the 
Royal Government classified the masso della Vecchia as 
National Monument of First Category. De Giorgi (1879) 
resumes De Simone (1872) data, reporting also the near-
by occurrence of a mushroom-like rock which lost its 
top stone and of another rock shaped as an anvil. This 
author refers the development of these particular rocks 
to weathering process even if he doesn’t rule out that 
these natural landforms could be used as sacred places 
by prehistoric men. 
The geomorphological singularity of the masso della 
Vecchia pedestal rock justifies its presence in the inven-
tory of geosites recently realized by the Regione Puglia 
Administration (Mastronuzzi et al. 2015).
Fig. 1: The grey box indicates the geographical position of masso della Vecchia area (Giuggianello, Salento Peninsula).
Fig. 2: The Masso della Vecchia pedestal rock in a XIX century 
drawing of Cosimo de Giorgi.
ACTA CARSOLOGICA 46/1 – 2017 9
GEOMORPHOLOGICAL ANALySIS OF KARST LANDFORMS AT THE mASSO dELLA VECChIA GEOSITE ITALy ...)
GEOLOGICAL AND GEOMORPHOLOGICAL SETTING
The Salento peninsula is the southernmost emerged 
part of Adria Plate which constitutes the foreland of 
both Apenninic and Dinaric orogens. It comprises a 
Variscan basement covered by a 3–5 km thick Meso-
zoic carbonate sequence (the Calcari delle murge unit) 
overlain by thin Tertiary and Quaternary deposits. 
The most ancient rocks of this cover were produced 
by transgressions after the definitive emersion of the 
Apulian carbonate platform occurred between the end 
of the Cretaceous and the beginning of Paleogene peri-
ods; in some cases, bauxitic deposits can be found be-
tween Mesozoic limestones and Paleogene units (Dog-
lioni et al. 1994).
Four sedimentary cycles have been recognized 
from Neogene to Lower Pleistocene periods (Giudici 
et al. 2012). The first cycle comprises the Pietra Leccese 
Formation and the overlying Calcarenite di Andrano 
Formation. The Miocene sedimentary cycle was inter-
rupted because of the emersion of Salento which pre-
vented the formation of Messinian evaporites. The total 
thickness of Miocene formations is greater than 150 m 
on the eastern side of the peninsula. The second cycle is 
represented by breccias and conglomerates of the Leuca 
Formation that was deposited during the Lower Plio-
cene, reaching a maximum thickness of 30 m. The third 
sedimentary cycle is represented by the Upper Plio-
cene Uggiano la Chiesa Formation, composed of well-
stratified and fossiliferous biodetritical limestones and 
yellowish calcareous sands with a maximum thickness 
of about 80 m. The fourth sedimentary cycle promoted 
the deposition in the Lower Pleistocene of the Calcar-
eniti del Salento Formation, a very fossiliferous biode-
tritical calcareous sediment marked by the occurrence 
of Artica islandica Linneo. Its maximum thickness is of 
about 60 m. Finally, a number of Middle-Upper Pleis-
tocene deposits related to eustatic sea level change can 
be found on the Salento peninsula (Hearty & Dai Pra 
1992; Mastronuzzi et al. 2007).
Three main tectonic events affected the Salento Pen-
insula during the Eo-Oligocene, the Middle Pliocene, 
and the Middle Pleistocene periods. In particular, the 
most recent tectonic phase was responsible for the final 
uplift of the Apulia foreland after the general subsidence 
took place in the early Miocene period; uplift ended at 
Marine Isotope Stages (MIS) 9.3, about 330 ka BP (Mas-
tronuzzi et al. 2007). Since then, maximum uplift rates 
have been recorded only in the Taranto area (0.25 m/ka 
according to Ferranti et al. 2006), whereas they decrease 
to zero in the southernmost part of the region. Finally, 
a slow subsidence has been recorded along the Salento 
peninsula coast during the last four millennia (Mas-
tronuzzi & Sansò 2014).
The Salento peninsula is a low-elevated landscape 
composed of a number of Pleistocene plains placed 
at different altitude between sea level and 160 m of el-
evation. They are bordered by geomorphically degraded 
fault scarps, mostly elongated in Nw−SE and NNw−SSE 
directions, by differential erosion scarps, and by relict 
cliffs. Along the Salento peninsula coast a number of 
marine terraces, produced by the superimposition of 
regional uplift and glacio-eustatic sea level changes oc-
curred since the Middle Pleistocene period, can be rec-
ognized.
In particular, the inner and western parts of the 
Salento Peninsula show a landscape produced by con-
tact karst processes made of wide karstic surfaces, rem-
nants of a Middle Pleistocene sedimentary cover and 
morphostructural ridges. The karstic surfaces belong to 
a re-exhumed landscape shaped between the Lower and 
the Middle Pleistocene whereas the morphostructural 
ridges are made of Mesozoic dolomitic-carbonatic units 
and show a polycyclic landscape (Selleri et al. 2003). 
However, sinkholes are the main karstic landforms in 
many sectors of Salento affecting all outcropping car-
bonate rocks, including the Cretaceous limestone, the 
Oligocene, Miocene, and Plio-Pleistocene calcarenites, 
and the middle-upper Pleistocene terraced marine de-
posits. They are widespread especially along the low el-
evated rocky platforms occurring both on the Adriatic 
and Ionian coasts and display different typologies and 
states of activity (Delle Rose & Parise 2002; Bruno et al. 
2008).
Notwithstanding all this, no specific research to 
describe the geomorphological features at masso della 
Vecchia site and to explain their genesis and evolution 
has been carried out so far. Aiming to fill this gap, a geo-
morphological survey of the area marked by this natu-
ral monument has been performed; it defined the main 
morphogenetic processes responsible for landforms gen-
esis as well as allows the morphogenetic evolution of lo-
cal landscape to be reconstructed.
ACTA CARSOLOGICA 46/1 – 201710
The masso della Vecchia pedestal rock is placed on the 
top surface of a morphostructural ridge, locally named 
Serra di Poggiardo, bordered by two low NNw−SSE 
trending scarps. Its top surface is a plain mainly shaped 
on Cretaceous limestone but also on Oligocene, Mi-
ocene and Lower Pliocene units (Fig. 3). It is placed at 
about 100 m above m.s.l. and gently slopes from the SSE 
to the NNw. A number of wide and shallow karstic de-
pressions can be recognized on this plain surface. From 
a genetic point of view, it could be referred to a marine 
abrasion surface shaped at the end of Lower Pleistocene 
while along the eastern Salento coastal slope the Porto 
miggiano calcarenites were depositing (Tropeano et al. 
2004).
Locally, on the ridge top surface three main lith-
ostratigraphic units crop out (the Calcari di Altamura 
Formation, the Pietra Leccese Formation, the Calcareniti 
di Andrano Formation), arranged in a monoclinal gently 
dipping towards NNw (Fig. 4). Two younger units (the 
Leuca Formation and the Sabbie di Uggiano Formation) 
can be recognized in correspondence of the lower elevat-
ed plains stretching at the foot of Serra di Poggiardo on 
its western and eastern slopes (Bossio et al. 2005).
The Calcari di Altamura Formation is a thick, 
shallow water carbonate succession deposited in shelf 
interior environments. In the studied area this unit 
is represented by a peritidal succession showing thin 
and rare inter-supratidal algal mats (stromatolites) and 
marked by quite common discontinuous concentrations 
of rudist fragments and bioclastic grainstone as well as 
frequent flat pebble intraformational breccias. The Cal-
cari di Altamura Formation has been referred to the late 
Campanian – early Maastrichtian (Parente 1994). The 
remnants of a bauxitic cover can be recognized on the 
Cretaceous limestones; it is in some places buried under 
small patches of two Oligocene lithostratigraphic units 
– the Galatone Formation and the Lecce Formation 
–, none cropping out in the studied area. The Salento 
bauxite derived by the erosion of a weathered pristine 
deposit formed most likely during the middle Campa-
nian emersion event under dry warm climatic condi-
tions (Mongelli et al. 2015).
The Pietra Leccese Formation is typically repre-
sented by biomicrites, badly stratified in thick beds, with 
prevalent calcareous plankton, generally straw-coloured, 
green in colour only in the upper part due to the abun-
dance of glauconite. The formation is transgressive on 
different pre-Neogene units through a conglomeratic 
level marked by phosphatic nodules or pebbles and mac-
rofossils. Occasionally, this level is replaced by a phos-
phatic film covering surfaces or filling bedrock cavities 
(Mazzei et al. 2009).
GEOMORPHOLOGICAL AND GEOLOGICAL FEATURES OF mASSO dELLA  
VECChIA GEOSITE
Fig. 3: Geomorphological map of 
the Masso della Vecchia area.
Legend: a – Serra di Poggiardo 
top abrasion plain (Lower Pleis-
tocene); b- denudation surface 
shaped on Pliocene units; c – slope 
scree; d – fault scarp; e – incised 
channels; f – talus cone; g – eleva-
tion point. black triangle marks 
the masso della Vecchia position.
PAOLO SANSÒ
ACTA CARSOLOGICA 46/1 – 2017 11
In the studied area three distinct lithofacies have 
been surveyed. The base is marked by a brownish con-
glomeratic level, about 20–30 cm thick, made of partly 
phosphatized limestone pebbles, phosphate nodules, nu-
merous phosphastized fossils and reworked bauxitic pi-
soliths. yellowish biomicrites made of prevailing calcare-
ous plancton with variable cementation follows upward; 
this level is constitutes by layers up to 2 m thick showing 
sparse fossils (mainly pectinids) and several bioturbated 
levels. The local sequence is closed by greenish glauco-
nitic biomicrites, without stratification, very rich in fos-
sils in the uppermost levels, often clustered in layers, and 
in small brownish phosphatized grains.
The Pietra Leccese Formation has been referred to 
the late Burdigalian-early Messinian (Mazzei et al. 2009). 
Its maximum thickness is about 90 m in the Lecce type 
area whereas it is about 35 m in the Cursi-Melpignano 
area and only 17 m in the studied area (Bossio et al. 
2005). The relatively small thickness of this unit in com-
parison with its duration (approximately 11 Ma) is in-
terpreted as a consequence of repeated action of marine 
currents that inhibited deposition and/or eroded the 
previously deposited sediments. The related hiatuses are 
generally outlined by the presence of more or less abun-
dant glauconite grains, a typical mineral of dynamic ma-
rine environment.
The Pietra leccese Formation is everywhere overlied 
by the Calcareniti di Andrano Formation which repre-
sents the regressive sequence of the Late Miocene sedi-
mentary cycle. This cycle was interrupted by the uplift of 
Salento peninsula occurred just before Messinian salin-
ity crisis. The Calcareniti di Andrano Formation reaches 
a thickness of about 50 metres; it is made of different 
carbonatic deposits which are well stratified and very 
fossiliferous. The unit can be entirely referred to the pre-
evaporitic Messinian.
Fig. 4: Geological map of Masso 
della Vecchia area.
Legend: a – Cretaceous limestone; 
b – Pietra Leccese Formation 
(Upper miocene); c – Calcarenite 
di Andrano Formation (Upper 
miocene); d – Leuca Formation 
(Lower Pliocene); e – Sabbie di 
Uggiano Formation (Upper Plio-
cene); f – fault; g – strata attitude; 
h – elevation point.
GEOMORPHOLOGICAL FEATURES OF THE mASSO dELLA VECChIA GEOSITE
A detailed geomorphological survey has been carried out 
aiming to provide a quantitative description of the singu-
lar landforms occurring at masso della Vecchia geosite as 
well as to define their genesis and evolution.
The survey allows four groups of landforms marked 
by peculiar features to be identified which are spatially 
arranged in belts stretching roughly in Sw−NE direc-
tion as well as two sinkholes (Fig. 5).
GEOMORPHOLOGICAL ANALySIS OF KARST LANDFORMS AT THE mASSO dELLA VECChIA GEOSITE ITALy ...)
ACTA CARSOLOGICA 46/1 – 201712
a) Groups of peculiar landforms
Starting from the SE, the first group is formed by elon-
gated rock pinnacles which studded a cultivated field; 
pinnacles in some cases are one parallel each other and 
divided by narrow corridors, about 4–5 m large (Fig. 6). 
Most of pinnacles were modified by farmers that ripped 
and accumulated rock slabs around main outcroppings. 
Pinnacles are about 2 m high and 10 m long and are 
shaped into the Pietra Leccese yellowish biomicrites. The 
pinnacle surface shows subsoil karstic microforms like 
cavernous weathering and subsoil scallops.
The small group of pinnacles placed to the eastern-
most part of the studied area (blocks 7) can be referred 
to this group. They are up to 1.6 m high, about 4.5 m 
long and 2.0 m large. They show two different rock sur-
faces: the lower surface, extended nearly vertically from 
soil level up to 1.0 m, is marked by well-developed sub-
soil scallops whereas a smooth gentler surface occurred 
in the upper part. A break-in slope separates the two 
surfaces (Fig. 7).
Rocky outcrops prevail northwestward where the 
second group of blocks can be found just at the border 
between olive groves and cultivate fields. This group is 
marked by pedestal rocks included the suggestive mas-
so della Vecchia (block 0), the mushroom-like rock de-
scribed in the previous chapter (Fig. 8). Its stalk is made 
by three strata of yellowish biomicrites showing in some 
areas cavernous weathering whereas the capstone is made 
of a massive glauconitic layer. The pedestal rock stands 
on a rocky platform, affected during the xIx century by 
Fig. 5: Spatial distribution of 
blocks surveyed in the Masso 
della Vecchia area.
Legend: a – olive grove; b – cul-
tivated field; c – rural road; 
d – dry-stone wall; e – subsoil 
pinnacle; f – Group 1 blocks; 
g – Group 2 blocks; h – Group 
3 blocks; i – Group 4 blocks; l – 
karstic sinkhole.
Fig. 6: A view of rock pinnacles 
which studded a cultivated field 
belonging to the Group 1. Pin-
nacles shown in the photo are one 
parallel each other and elongated 
in NE−SW direction; they are di-
vided by narrow corridors, about 
4–5 m large.
PAOLO SANSÒ
ACTA CARSOLOGICA 46/1 – 2017 13
a small quarry activity (De Giorgi 1879), bordered by 
two main karstic corridors developed along main joints.
The same lithological sequence gives rise to another 
less prominent pedestal rock (block 5) about 120 metres 
to the northeast of the masso della Vecchia. The rock stalk 
is about 1.0 m high from soil surface and is constituted 
by weakly cemented, laminated and bioturbated yel-
lowish biomicrites whereas the top block is about 0.8 m 
thick, about 5.4 m long and 3.0 m large (Fig. 9).
The third group is placed inside a wide olive grove 
and comprises rocks showing a prominent notch at the 
base. Block 1 offers the best example; it has an ellipsoidal 
shape (long axis length 9.5 m, short axis length 6.0 m) 
and elevates about 2.3 m from ground surface (Fig. 10). 
Fig. 7: The surface of block 7, belonging to group 1, is affected by 
well-developed subsoil scallops (sensu zseni 2009) and cavern-
ous weathering.
Fig. 8: The Masso della Vecchia pedestal rock (block 0, group 
2) viewed from NW. The top block is made of a massive glauco-
nitic layer and has a perimeter 15.60 m long, long axis 5.70 m 
and short axis 2.85 m; the block thickness at its centre is about 
2.30 m. Three strata of yellowish biomicrites showing in some ar-
eas cavernous weathering constitute the stalk.
A notch marks the base of the block; notch’s edge is at 
about 1.3 m from the soil surface whereas the maximum 
depth of about 1.6 m is reached at the block base. The 
lower section of the notch (about 0.8 m from soil sur-
face) is shaped on the yellow biomicrites, the top on a 
massive glauconitic layer.
The last group comprises low karren pinnacles di-
vides by narrow depressions filled by soil developed 
along main joints (grikes), striking about N150E–N170E. 
Pinnacles are bordered at ground level by subcutaneous 
channels with subcircular transverse section up to 50 cm 
high and 20–30 cm wide (Fig. 11). In Fig. 12 the peculiar 
profiles of some blocks surveyed at masso della Vecchia 
area are reported.
Fig. 9: A view of block 5 (group 2) from south. It is a less promi-
nent pedestal rock showing a stalk about 1.0 m high. The litho-
structural difference between the cap rock, made of massive 
glauconitic calcarenites, and the stalk, constituted by laminated 
biomicrites, can be easily recognized.
Fig. 10: block 1 (group 3) shows a well-developed notch at its 
base. Notch is about 1.6 m deep and shows its edge is at about 
1.3 m from the soil surface. On the foreground a half-bell can be 
recognized.
GEOMORPHOLOGICAL ANALySIS OF KARST LANDFORMS AT THE mASSO dELLA VECChIA GEOSITE ITALy ...)
ACTA CARSOLOGICA 46/1 – 201714
them showing well-developed rundkarren (subcutane-
ous channels sensu Slabe 1999) (Fig. 14). The sinkhole S1 
opens at the bottom of a roughly circular morphological 
b) sinkholes
Two sinkholes have been surveyed in the third group 
area (S1 and S2 in Fig. 5). The largest one (S1) has been 
partly filled by farmers with rock slabs (Fig. 13), one of 
Fig. 12: Peculiar profiles of some 
blocks surveyed at Masso della 
Vecchia area. Legend: a – mas-
sive grainstone; b – bioturbated 
or laminated biomicrites; c – soil.
Fig. 13: The sinkhole S1 opens at the bottom of a morphological 
depression, roughly circular in shape, showing a diameter of 50 m.
Fig. 14: The sinkhole S1 has been partly filled by farmers with 
rock slabs. The surface of one of these slab is marked by well- de-
veloped subcutaneous channels that, accordingly to the local tra-
ditions, resembles the hercules’ foot.
Fig. 11: A view the subcutaneous channels with subcircular 
transverse section that mark the borders of blocks belonging to 
the Group 4.
Fig. 15: N-S (below) and E−W (above) cross profiles of sinkhole 
S1. The sinkhole shows an elliptical shape with main axis about 
50 m long. Sinkhole bottom is about 2 m lower than surrounding 
level topographic surface.
PAOLO SANSÒ
ACTA CARSOLOGICA 46/1 – 2017 15
depression, about 2 m lower than surrounding surface, 
showing a diameter of 50 m (Fig. 15). On the other hand, 
sinkhole S2 is quite entirely covered by stone blocks and 
vegetation so that its morphology cannot surveyed.
According to the genetic classification of sinkholes 
proposed by Gutierrez et al. (2014) it is possible to re-
fer the S1 sinkhole to a cover suffosion sinkhole since it 
result from both subsurface dissolution and downward 
gravitational movement of overlying material. S1 sink-
hole formed most likely by downward migration of re-
sidual soil cover (suffosion process) into major conduits 
occurring into the bedrock.
DISCUSSION
The geomorphological analysis of masso della Vecchia 
area points out an epikarst marked by peculiar land-
forms shaped on the Miocene Pietra Leccese Formation 
such as pinnacles, channels, notches, subsoil scallops, 
half-bells and so on. The epikarst consists of a near sur-
face zone of weathered rock with high secondary poros-
ity that can outcrop directly at the surface or occur im-
mediately beneath the soil (williams 2008). The epikarst 
is tipically 3–10 m deep but its characteristics can vary 
considerably according to lithology and geomorpho-
logical history. The high porosity and permeability of 
the epikarst arises from an intense carbonate solution 
because of proximity to the main source of CO2 pro-
duction in the soil. Soil, in fact, has an important role 
in the evolution of different karst features (Zseni 2009). 
In general, forms which develop in open-air conditions 
are fretted and sharp, having been subjected to much 
more selective corrosion due to episodic dissolution by 
rainwater so that only the rapidly soluble constituents 
of the rock will be removed. On the contrary, the so-
lution of limestone is more intense under a soil cover 
due to the higher CO2 concentration and the longer 
time period of direct water-rock contact. In the case of 
subsoil solution, in fact, CO2 and other acids produced 
by the breakdown of the organic matter by microor-
ganisms living in the soil add to the CO2 dissolved by 
rainwater from the air. The macroflora produces CO2 
directly through respiration of roots. For this the net-
work of fissures through which percolation water passes 
is widened by dissolution near the surface but the extent 
and frequency of widening diminished gradually with 
depth. Solutionally enlarged joints taper downwards 
and become less numerous (williams 1983). Since soil 
is often washed down into the larger grikes, lowering 
of the soil surface down the developing cleft, possibly 
also with soil loss into near surface cave systems, can 
result. The distribution of subsoil solutional landforms 
depends on soil moisture, drainage rates, soil texture, 
soil depth, water-flow rates, slope, vegetation, and the 
nature of the limestone.
Numerous classifications of subsoil karst landforms 
have been proposed so far (e.g. Bögli 1960; Jennings 
1971, 1985; Gams 1976; Slabe 1999; Ford & williams 
2007; Slabe & Liu 2009); in this paper the classification 
of Zseni (2009) has been adopted.
The influence of local stratigraphic sequence as 
well as the geological structure on karstic process can 
explain the present morphology of the local landscape. 
Starting from an even abrasion plain presently placed at 
about 100 m of elevation, karstic processes have been re-
sponsible for the geomorphological evolution of the area 
(Fig. 16). Due to the geological structure the yellowish 
laminated biomicrites crop out at Group 1 area; subsoil 
solution has been responsible for the widening of main 
fracture planes and for the development of elongated 
pinnacles, which became more and more prominent as 
soil level lowered due to corridors deepening and wid-
ening. The occurrence of the deep karstified Mesozoic 
limestone basement close to ground surface enhanced 
surface lowering in response to soil transfer in epikarst 
cavities.
In Group 2 area, a massive grainstone bed overlies 
yellowish laminated biomicrites. Here differential weath-
ering due to soil cover has been responsible for the mod-
elling of some pedestal rocks, whose height lowers from 
SSw to NNE. Historical data indicate that at least two 
large pedestal rocks have been destroyed.
In Group 3 area, deep and high solution notches 
formed along the border of larger outcrops, particularly 
at the contact between massive grainstone/yellowish 
laminated biomicrites.
Finally in Group 4 area, solution channels and sub-
soil enlargement of main joints affecting massive grain-
stone outcroppings can be detected.
The geomorphological analysis of the local land-
scape suggests that the subsoil karstic process responsi-
ble for the particular morphology of masso della Vecchia 
area can be referred to a morphogenetic phase occurred 
in the Upper Pleistocene. In fact, in this period a Sw−NE 
extensional tectonic phase reactivated the Nw−SE and 
GEOMORPHOLOGICAL ANALySIS OF KARST LANDFORMS AT THE mASSO dELLA VECChIA GEOSITE ITALy ...)
ACTA CARSOLOGICA 46/1 – 201716
phauna that refers subsoil karst development to the Last 
Interglacial Period (Pandolfi et al., in press). Moreover, 
the same morphogenetic phase most likely promoted 
the development of numerous solution pipes in homog-
enous Pliocene and Pleistocene calcarenites cropping 
out at several coastal areas of Salento peninsula (Marsico 
et al. 2003; De waele et al. 2010).
NNE−SSw faults (Di Bucci et al. 2009, 2011) influenc-
ing karst landforms development (Festa et al. 2012; Pepe 
& Parise 2014) under humid-warm climatic conditions 
which promoted intense subsoil karst processes respon-
sible for the widening of joints and cutters development 
in Pietra Leccese Formation. These processes are well 
documented in literature since cutters, locally named 
“ventarole”, preserve in their filling a rich vertebrate fossil 
Fig. 16: Geomorphological scheme of subsoil karst landforms surveyed at Masso della Vecchia area.
Legend: a – Cretaceous limestone; b – yellow laminated or bioturbated biomicrite (Pietra Leccese Formation, Upper miocene); 
c – greenish massive glauconitic bed (Pietra Leccese Formation, Upper miocene); d – soil cover; e – strata surface; f – transgressive 
surface.
CONCLUSIONS
The assemblage of peculiar landforms occurring in the 
masso della Vecchia area can be explained taking into 
account the geological characteristics and the geomor-
phological evolution of Serra di Poggiardo area. An abra-
sion surface formed during lower Pleistocene, presently 
at about 100 m of altitude, cut strata belonging to the 
Miocene Pietra Leccese Formation which are locally ar-
ranged in a monoclinal structure slightly dipping north-
eastward.
Starting from this abrasion surface, subsoil karst 
processes have been responsible for the soil surface low-
ering due to joints enlargement. The particular litho-
stratigraphical characteristics of Pietra Leccese Forma-
tion and the gently dipping of strata to the NE justify the 
occurrence of pinnacles where poorly consolidated, bio-
turbated, yellowish biomicrites crop out. Pedestal rocks, 
notches and grikes formed where weak biomicrites are 
covered by massive grainstones. Smaller subsoil karren 
produced by karst processes are recognizable such as 
subcutaneous channels, subsoil scallops and half-bells.
The morphogenetic phase responsible for the de-
velopment of masso della Vecchia landforms assemblage 
can be referred to the Last Interglacial Period when a 
tectonic extensional phase along with warm humid cli-
matic conditions promoted subsoil karstic processes.
The present research could be the first step for the 
geotouristic promotion of this very peculiar site of Salen-
to peninsula aiming to improve significantly the cultural 
touristic offer in the Salento peninsula and to increase 
the number of Italian and foreign tourists during low-
season periods.
PAOLO SANSÒ
ACTA CARSOLOGICA 46/1 – 2017 17
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