Imp.DeWaeleDiGreg.Pala


KARST GEOMORPHOSITES OF MONTE ALBO 
(NORTH-EAST SARDINIA) 

Jo De Waele, Felice Di Gregorio & Aldo Pala  
Department of Geology, Via Trentino 51, 09127 Cagliari - E-mail: geoam@unica.it 

ABSTRACT: J. De Waele et al., Karst Geomorphosites of Monte Albo (north-east Sardinia). (IT ISSN 0394-3356, 2005).
In this paper the Authors present the results of a study performed on the geomorphosites of the Monte Albo chain (North-East
Sardinia), an important karst area elongated in a NE-SW direction for a length of 30 km and a width of 5, starting from 50 m a.s.l. and
reaching altitudes of more than 1100 m. This relief consists of Middle Jurassic-Lower Cretaceous sometimes intensely karstified dolo-
stones and limestones covering with an unconformity a metamorphic Palaeozoic basement. 
Although the geomorphosites of Monte Albo are not so impressive as in other Sardinian karst areas it seems noteworthy presenting
them in the framework of this spectacular landscape unit that, in its whole, represents an area of great geomorphological interest. 
Among the described geomorphosites many places with didactic surficial karst phenomena (Karren fields of Monte Turuddò, suspen-
ded valley of Janna Nurai, Solution flutes and kamenitza of Punta Catirina, macro-dolines of Campu ‘e Susu, Sas Puntas and Altudè,
ruin-like landforms of Nuraghe Litu Ertiches, canyon of Riu Siccu), the structural geosite of Punta Azza Ruja, the overthrusts and the
conglomerates of Cuile su Ramasinu, the vertical cliffs of N-Monte Albo, the geological landscape of Punta Cupetti and the landslide
of Punta Ervare 'e Chervos and two places of hydrogeological interest can be mentioned (Sinkhole of Bonaettè and karst spring of
Fruncu ‘e Oche). Furthermore many subterranean places are enclosed, two vertical karst shafts (Tumba ’e Nudorra and Tumba 'e
Nurai), several horizontal caves (Sa Conca ‘e Crapa, Omines Agrestes, Locoli, Su Santuariu, Cane Gortoé) and a natural tunnel
(Listincu).
All these geomorphosites should be connected in a local network inserted in the Monte Albo landscape unit, already part of the
Geomining, Historical and Environmental Park of Sardinia (Area 6), through the realisation of equipped pathways and the elaboration
of explicative maps and panels and a website in which geology, geomorphology, karst, fauna, flora, archaeology and industrial
archaeology are described. The explanation of the chain’s genesis, its evolution, its geodiversity and the single elements it contains
can help the visitors in understanding the importance of geology and geomorphology on landscape evolution, flora and human activi-
ties, that combine in an educational model of great suggestion and efficiency.
This proposal of valorisation of these landscape units and their geomorphosites could well be connected to other areas of the region,
and the Authors hope that the local and regional stakeholders will commit themselves in the valorisation of their territory, giving an
important service to the many tourists that come and visit the Monte Albo. 

RIASSUNTO: J. De Waele et al., Geomorfositi carsici del Monte Albo (Sardegna nord-orientale). (IT ISSN 0394-3356, 2005).
In questo lavoro gli Autori presentano i risultati di una ricerca effettuata sui geomorfositi della catena del Monte Albo (Sardegna nordo-
rientale), un’importante area carsica allungata in direzione NE-SW per una lunghezza di 30 km ed una larghezza di 5, con quote che
variano dai 50 m s.l.m. della piana fino ad oltre 1100 sulle cime più alte. La catena è costituita da dolomie e calcari di età Giurassico
medio-Cretaceo inferiore, più o meno carsificati, che poggiano in discordanza sul basamento paleozoico metamorfico. 
Anche se i singoli geomorfositi del Monte Albo non raggiungono l’importanza di quelli riscontrati in altre aree carsiche sarde, tuttavia
essi caratterizzano questa spettacolare unità di paesaggio e ne fanno un’area di grande interesse geomorfologico.
Tra i geomorfositi scelti riportiamo molte morfologie carsiche di elevato interesse didattico e turistico-culturale (campi careggiati di
Monte Turuddò, la valle sospesa di Janna Nurai, le scannellature e le vaschette di corrosione di Punta Catirina, le macrodoline di
Campu ‘e Susu, di Sas Puntas e di Altudè, le città di roccia di Nuraghe Litu Ertiches, la gola di Riu Siccu), i geositi strutturali di Punta
Azza Ruja, di Cuile Su Ramasinu e del versante Nord della catena, il paesaggio geologico di Punta Cupetti, la frana di ribaltamento di
Punta Ervare ‘e Chervos e due luoghi di interesse idrogeologico (inghiottitoio di Bonaettè e sorgente carsica di Fruncu ‘e Oche).
Inoltre, molte sono le grotte incluse nell’elenco, tra cui due voragini (Tumba ‘e Nurai e Tumba ‘e Nudorra),  molte grotte suborizzontali
(Sa Conca ‘e Crapa, Omines Agrestes, Locoli, Su Santuariu, Cane Gortoé) ed un traforo naturale (Listincu).
Tutti questi geomorfositi potrebbero essere collegati in una rete locale all’interno dell’unità di paesaggio del Monte Albo e facente
parte del Parco Geominerario, Storico ed Ambientale della Sardegna (Area 6), mediante la realizzazione di sentieri attrezzati, l’elabora-
zione di carte tematiche e pannelli informativi e la creazione di un sito web con l’illustrazione degli aspetti più significativi del paesaggio
naturale ed umano. L’illustrazione del paesaggio e della sua evoluzione, della sua geodiversità e dei caratteri dei singoli geomorfositi
che esso contiene può aiutare il visitatore a comprendere l’importanza della geologia e della geomorfologia per l’evoluzione del pae-
saggio e delle molteplici attività antropiche che vi si svolgono, creando un modello educazionale di grande suggestione ed efficienza.
Questa proposta di valorizzazione dell’unità di paesaggio e dei geomorfositi in essa contenuti potrebbe essere estesa anche ad altre
aree della regione. Gli Autori auspicano che gli amministratori locali e regionali elaborino proposte di valorizzazione di questo territorio
caratterizzato da molteplici valenze, dando un importante servizio non solo ai molti turisti che visitano il Monte Albo ma anche alla
popolazione locale. 

Keywords: Jurassic limestones, Karst, Geomorphosites, Monte Albo, Sardinia.

Parole chiave: Calcari giurassici, Carsismo, Geomorfositi, Monte Albo, Sardegna.

Il Quaternario
Italian Journal of Quaternary Sciences
18(1), 2005 - Volume Speciale, 145-153



146 J. De Waele et al.

1. INTRODUCTION

The study of geomorfosites in karst areas has
already brought our research team in many parts of the
Island; the Gulf of Orosei (Barca et al., 1995), the
Iglesiente-Sulcis area (De Waele et al., 1998), the
Tacchi area (Ardau & De Waele, 1999; De Waele et al.,
2004). Furthermore the twenty most important karstic
geosites of the Island have already been described (De
Waele et al., 1999) and at the moment one of us (De
Waele) is working on the inventory of natural hypogean
geosites in the framework of a national research pro-
gram performed together with the National Geological
Survey (Piccini et al., 2004). 

In the framework of the National Project COFIN
2001-2003 “Geomorphosites in the Italian Landscape”
our research team has continued these researches, and
in this paper the results of a study on Monte Albo are
presented. 

2. GEOLOGY

Monte Albo is a karst area located in north-east
Sardinia, elongated from NE to SW for a length of 30
km and a width of 5 and reaching altitudes of more
than 1100 m a.s.l..

The outcropping rocks can roughly be subdivided
in a Palaeozoic mainly metamorphic basement and
Mesozoic sedimentary sequences (Fig.1).

The characteristics of the Palaeozoic rocks are
related to the tectonic and metamorphic events of the
Hercynian orogeny (Carboniferous-Permian). In the
south-eastern part of Monte Albo the basement is cha-
racterised by Hercynian granites of Permian age, while
to the north the outcropping rocks are more or less
metamorphic. Petrographical and mineralogical studies
have allowed to distinguish two important crystallisa-
tion episodes (Franceschelli et al., 1982; Elter & Sarria,
1989) and four complexes of different metamorphic
degree. The outcropping metamorphic rocks are, rou-
ghly from south to north, constituted of metasandsto-
nes, phyllites, micaschists, paragneiss, granodioritic
orthogneiss and bird’s eye gneiss.

After a long-during continental period, estimated
from Permian to Lower Jurassic, the sea started
occupying the hilly Hercynian peneplain during
Bajocian-Bathonian. The Jurassic-Lower Cretaceous
ocean never reached great depths in the Monte Albo
area, and the different carbonate facies evidence seve-
ral shallow depositional environments, going from
lagoons to coral reefs. This sedimentary sequence
starts with dolostones containing limestone lenses,
oolithic limestones and massive fossil-rich outer-shelf,
reef, interreef and backreef limestones.

The Jurassic transgression starts with clastic
sediments of the Genna Selole Formation, represented
by quartz conglomerates and sandstones with plant
fossils typical of a fluvial or delta environment influen-
ced by tidal movements (Amadesi et al., 1961; Fazzini
et al., 1974; Dieni et al., 1983). Traces of this transgres-
sional facies can be found at Punta Casteddu (south
Monte Albo) (Dieni & Massari, 1971). Upwards this
facies becomes marly, typical of a littoral depositional
environment, and the alternation of marl and dolostone

beds preludes the Dorgali Formation dolostones
(Amadesi et al., 1961; Calvino et al., 1972; Dieni &
Massari, 1985; 1987). These dolostones are sandy in
the basal levels becoming pure brownish dolostones in
the upper beds and locally contain Brachiopods,
Echinoids, Ammonites, Belemnites and Foraminifers of
Bathonian-Kimmeridgian. At Monte Albo this Formation
reaches a thickness of at least 300 meters in the
western part (Lula), but reduces to only a couple of
meters in the eastern extremity (Monte Gutturgios).

Upon these dolostones two heterotopic limestone
Formations are reported: the s’Adde Limestones and
the Monte Bardia Formation (Dieni & Massari, 1985).
The first Formation is characterised by brownish micro-
crystalline limestones sometimes containing chert
nodules, not well stratified at the bottom but extremely
well bedded in the upper part. The fossil fauna
(Ammonites, Belemnites, Brachiopods, Echinoids and
Foraminifers) gives an age of Callovian-Kimmeridgian.
The Monte Bardia Formation instead is composed of
typical reef and bioclastic limestones, with frequent fos-
sil corals (sometimes in life position) and their debris.
The age of these limestones, based on Corals,
Gastropods, Algae and Foraminifers is Kimmeridgian-
Berriasian (Upper Jurassic-Lower Cretaceous). The
uppermost part of this Formation is characterised by
marly limestones sometimes with mud cracks and
fauna of brackish water environments, introducing the
deposition of Lower Cretaceous Purbeckian sediments
after a short interruption of sedimentation (Massari,
1968). These last sediments, composed of marls and
marly limestones locally rich in pyrite and organic mate-
rial, have been deposited in a relatively deep and confi-
ned sea and can be found only in two tectonically
disturbed areas southwest of Siniscola (Dieni et al.,
1987). Their age has been determined on the basis of
Foraminifers to Valanghinian (Dieni & Massari, 1966).  

Upper Cretaceous is not present in the Monte
Albo region, but the discovery of Maastrichtian pebbles
in the post-Middle Eocene conglomerate of Cuccuru ‘e
Flores, outcropping in the central-eastern part of Monte
Albo, indicates that these sediments were eroded in
Late Mesozoic-Early Cretaceous times (Busulini et al.,
1984). The syn-tectonic continental Cuccuru ‘e Flores
conglomerate was deposited after Middle Eocene
during a tectonic instable and continental period related
to the Pyrenean and Apennine collision (Dieni &
Massari, 1965). 

The geological sequence of Monte Albo is com-
pleted with Pleistocene gravitational deposits, mainly
represented west of Siniscola (flanks of Punta Cupetti)
and Quaternary deposits (alluvium, debris, etc.).

The tectonic situation is dominated by two main
transcurrent fault systems, NE-SW and E-W,  associa-
ted with local transpressive and pull apart sectors cau-
sed by the continental collision between the Apulian
plate and the South-European margin during
Oligocene-Lower Miocene. The most important fault
system in the Monte Albo area is directed NE-SW (e.g.
Nuoro Fault), running parallel to the national road that
connects Nuoro with Siniscola (Carmignani et al., 1994;
Pasci, 1997). The movement of the transcurrent Nuoro
fault is left-handed and is believed to be several kilome-
tres for a vertical displacement of approximately 1000
meters and has lead, in the Monte Albo area, to impor-



147Karst geomorphosites ...

Fig. 1 – Geological sketch map of Monte Albo with the location of the geomorphosites.

Carta geologica schematica del Monte Albo con l’ubicazione dei geomorfositi.

tant overthrusting. Along these overthrust surfaces
many outcrops of the syn-tectonic Cuccuru ‘e Flores
conglomerate can been found.

From a morpho-structural point of view these tec-
tonic movements have determined the typical landform
of cuesta or hogback to the entire chain, with the more
or less gently dipping back towards SE (Fig.2).

3. KARST GEOMORPHOLOGY

The Mesozoic dolostones and limestones of
Monte Albo have been interested by karst processes
since their early emersion (Upper Cretaceous), even

though the major karst landforms can be referred to the
Plio-Quaternary. 

Dolostones (Dorgali Formation, Dogger) are cha-
racterised by diffuse fractures and joints and a well-
defined bedding causing ruin-like landforms (pinnacles)
and scarcely developed micro-forms (essentially solu-
tion pans or kamenitze). Intense fracturing and jointing
leads the meteoric water immediately underground with
scarce superficial runoff. Caves in dolostones usually
consist of vertical shafts in which the tectonic imprint is
clearly distinguishable. Limestones instead (S’Adde
Limestone and Monte Bardia Formation, Dogger-Malm)
are generally microcrystalline and pure carbonates that
are ideal for the development of micromorphologies



148

such as solution flutes, rillenkarren, kamenitze etc. (Fig.
3). In these rocks interesting solution caves are also for-
med (e.g. Conca ‘e Crapa) characterised by phreatic
rounded morphologies and well developed calcite con-
cretions. In areas affected by important tectonics (e.g.
the southwestern flank of Monte Albo) no important
caves are known and landforms are very much influen-
ced by the tectonic surfaces and subsequent differen-
tial erosion.

The North-western flank of the mountain is much
more exposed to rain than the South-eastern one, also
because here are located the highest altitudes (Punta
Catirina and Monte Turuddò 1127 m a.s.l.). This diffe-
rence is also clearly visible in the surface landforms.
Karren fields are well developed especially on the
southern slopes of Punta Sae Mussinu, Punta
Ferulargiu and Punta Su Mutucrone. In many areas of
high altitude (e.g. the flanks of Punta Catirina and
Monte Turuddò) the exposed karren fields are much
more rounded, being an ancient covered karst. In fact,
deforesting of these areas probably goes back to the
early 20th century and the covering soil has been
washed away since then (Fig. 4).

A distinct feature on Monte Albo is the scarcely
developed drainage pattern,
meaning that seasonal runoff
takes place along small river
incisions generally directed
towards the northwest and the
southeast. Between Punta
Gutturgius and Punta Cupetti
the valley s’Adde cuts though
the Monte Albo carbonates
from NW to SE and ends with
the canyon of Riu Siccu located
on the vertical walls of the
southern flanks. This valley has
probably been inherited from a
period in which the drainage on
the north-western Palaeozoic
basement was directed towards
the SE and represents thus the
initial stage of the formation of a
suspended valley.

A beautiful example of this
latter type is Janna Nurai, loca-
ted between Monte Turuddò
and Punta Catirina at an altitude
of approximately 600 meters.
This valley flows towards the
east ending up in the macrodo-
line of Altudè. This large and
complex depression still reflects
an ancient drainage pattern
with a southwest-northeast
direction, finding its natural
outlet in the steep Badde Viola
canyon, probably of a much
more recent origin.

But the most interesting
karst landforms of Monte Albo
are the two macrodolines of
Campu ‘e Susu and Sas
Puntas, located on the northea-
st flank of Punta Catirina, at an

J. De Waele et al.

Fig. 2 – Schematic sections showing the structural and geological settings of: A) the two
macrodolines Campu ‘e Susu and Sas Puntas; B) the two mountains of Punta Azza Ruja and
Punta Urros. For location see Fig.1.

Sezioni schematiche che mostrano le condizioni geologico-strutturali di: A) le due macrodoline
di Campu ‘e Susu e Sas Puntas; B) i due rilievi dolomitici di Punta Azza Ruja e Punta Urros. Per
la localizzazione vedasi Fig. 1.

altitude of 950 and 900 m a.s.l. respectively (Fig. 5).
These large depressions are characterised by relatively
steep slopes and an almost flat floor, with considerable
dimensions (average width of 500 meters and length of
almost 1 km). They are probably formed on a palaeo-
valley, successively transformed in large depressed
areas that take the form o macrodolines: their genesis
is thus only partially controlled by dissolution of lime-
stone. A small outcrop of “éboulis ordonnées” on the
northern slope of Sa Puntas would represent a
Pleistocene debris deposit produced by the breakdown
of the valley walls.  

Underground karst phenomena are not very well
developed on Monte Albo, especially comparing this
karst area with other neighbouring carbonate outcrops
such as Supramonte or the Gulf of Orosei. The majority
of caves are characterised by vertical development,
mostly fracture-controlled shafts with no horizontal
branches. The best example of such type of cave is
Tumba ‘e Nurai, a 100 meters deep karst pit with an
elliptical plant of 6x12 meters. Much more impressive is
the spectacular Tumba ‘e Nudorra cave, a collapsed
sinkhole of 45x30 meters width and a depth of 45
meters. This sinkhole resembles somewhat the famous



149

sil cave passage that crosses the Punta Listincu lime-
stone ridge from side to side. The two active caves are
Cane Gortoé and Locoli. The first is located in the villa-
ge of Siniscola and is characterised by approximately 1
km of narrow horizontal cave passages occupied by
two different subterranean rivers that join before emer-
ging from the entrance. The second is located at the
foot of the Monte Albo Southern flank and gives rise
during heavy rainy periods to the Locoli river. This cave

is characterised by impressive
submerged passages for a total
length of more than 1050
meters and a water depth of 80
(Perna & Murgia, 2002).

4. GEOMORPHOSITES

In the framework of the
National Project COFIN “Geo-
morphosites in the Italian
Landscape” we have chosen
the most interesting karst geo-
morphosites of Monte Albo on
the basis of an exhaustive
bibliographical research, on the
analysis of aerial photographs
and on detailed field work,
inserting them in a geomorpho-
site database (Tab. 1). Karst
morphology has previously
been described by several
Authors (Altara, 1964; Mucedda,
1991; Pala, 1998).

The largest karst landforms
on Monte Albo are the macro-
dolines: three of these have
been inserted in our geo-
morphosite database: Campu ‘e
Susu, Sas Puntas and Altudè.
All three are located in the
Southern part of the mountain,
the first two northeast of Punta
Catirina at an altitude of 950
and 900 m a.s.l. respectively,
and Altudè two km East of these
about 300 meters lower (Pala,
1998). All three have the shape
of macrodolines, but are most
likely genetically related to a
post-tectonic Tertiary (Mio-
Pliocene) palaeo-drainage
system that had a general W-E
direction and drained a morpho-
logical height located to the
west, now mostly eroded.
Especially the plain of Altudè
still reflects the complex pattern
of several converging rivers.

Smaller dolines are scarcely
represented on Monte Albo,
except for the spectacular
Tumba ’e Nudorra collapse doli-
ne located right on top of the
homonymous mountain. Tumba

Karst geomorphosites ...

Fig. 4 – Geomorphological sketch map of the area of the two macrodolines Campu ‘e Susu
and Sas Puntas.

Carta geomorfologica schematica dell’area delle due macrodoline Campu ‘e Susu e Sas
Puntas.

Fig. 3 – Some examples of karst microforms (Monte Turuddò and Punta Catirina).

Alcuni esempi di microforme carsiche (Monte Turuddò e Punta Catirina).

“cenotes” of Mexico, also for the presence of a luxu-
riant vegetation on its bottom.

The horizontal caves of Monte Albo can be subdi-
vided in relict and active caves (Mucedda, 1991).
Among the first Su Santuariu, Conca ‘e Crapa, Omines
Agrestes and Galleria Listincu can be mentioned. The
first three are relic caves with quite well developed
chambers and cave passages characterised by impor-
tant flowstones, while the fourth is a 20 meter long fos-



150 J. De Waele et al.

Table 1 – The main characteristics of the geomorphosites of Monte Albo.

Le principali caratteristiche dei geomorfositi del Monte Albo.

Fig. 5 – The macrodoline Campu ‘e
Susu seen from Punta Catirina
towards the NE. The whole hogback
of Monte Albo is clearly distingui-
shable.

La macrodolina fotografata da Punta
Catirina verso NE. L’intero hogback
del Monte Albo è chiaramente visibi-
le.

N° Name Commune Altitude Morphotype Access Importance
m a.s.l.

1 Campu ‘e Susu Lula 980 Macrodoline B L

2 Sas Puntas Lula 895 Macrodoline B L

3 Tumba ‘e Nudorra Lula 910 Collapse sinkhole C* R

4 Conca ‘e Crapa Lula 1.055 Cave B* L

5 Su Santuariu Lula 240 Cave B* L

6 Omines Agrestes Lula 790 Cave B* L

7 Cane Gortoe’ Siniscola 45 Cave A* L

8 Tumba ‘e Nurai Lula 670 Karst pit B* R

9 Locoli Lula 70 Cave A* R

10 Listincu Lula 635 Cave-tunnel C* L

11 Bonaette’ Lodè 550 Swallow hole A L

12 Altude’ Lula 575 Macrodoline A L

13 Janna Nurai Lula 575 Suspended valley B L

14 M.Te Turuddo’ Lula 1.080 Karren field B L

15 P.ta Urros Lula 475 Geological structure B L

16 P.ta Gurturgius Lula 830 Palaeo-landslide A L

17 P.ta Catirina Lula 1.090 Karst landforms B L

18 S’Adde-Riu Siccu Siniscola 500 Canyon C L

19 P.ta Cupetti Siniscola 1029 Karst landscape B L

20 Litu Ertiches Lula-Irgoli 200 Ruin like landscape A L

21 Fruncu ‘e Oche Siniscola 48 Karst spring A R

22 Albo N Flank Lula-Lodè 500-700 Cliffs A L

23 Cuile Su Ramasinu Lula 400 Tectonic features A L

Access: A=easy (close to roads), B=Difficult (close to equipped pathways), C=Very Difficult (far from existing pathways
and roads), *Speleological; Importance: L=Local, R=Regional



‘e Nudorra is a unique example of collapse sinkhole
and can be classified as one of the most beautiful ones
of Sardinia (Loru & Sechi, 1984).

Of different nature is the famous Tumba ‘e Nurai
pit, located close to the Janna Nurai pass, constituted
of a 100 meter deep karst pit (Mucedda, 1983). This is
the deepest pit of Monte Albo, known since a very long
time also to local people who narrate fantastic stories
about this hole, and it was explored for the first time by
speleologist of Trieste in 1955 (Guidi, 2002).

The nearby suspended valley of Janna Nurai is
the most beautiful example of Monte Albo and one of
the most interesting of Sardinia. It is clearly visible from
the village of Lula and constitutes one of the few natural
gateways to the mountain from the west. This ancient
valley reflects a palaeo-drainage system, connected to
the one of the three macrodolines, that flowed towards
the east where it continued in the valley of Altudè.

The only valley that can occasionally become
active on Monte Albo is the S’Adde-Riu Siccu valley,
that starts on the metamorphic rocks south of Punta
Cupetti, directs towards the southeast and becomes a
beautiful canyon before leaving the carbonate chain
with a succession of vertical falls (Loru & Dore, 1994).
From the southeast this valley is clearly visible and is
also characterised by beautiful ruin-like landforms (pin-
nacles).

These typical ruin-like landforms are even more
developed and easily accessible close to the Nuraghe
Litu Ertiches where they form a labyrinth of dolomite
rocks and pinnacles.

Karst micro-forms are not very well developed on
Monte Albo and they are usually confined to Monte
Bardia or s’Adde pure limestone facies where slopes
are not too steep and vegetation (thus soil) is not too
thick. Two places are of special interest and have been
chosen as geomorphosites: the Monte Turuddò karren
fields and the Punta Catirina micro-forms. The first is
characterised by uncovered karren fields that have
been developed under soil cover. Soil has probably
been washed away since the early 20th Century, when
intense deforestation changed the natural landscape of
Monte Albo. At Punta Catirina, especially along the
North-eastern slope, rillenkarren, kamenitze and solu-
tion channels are relatively well preserved, representing
a good didactic example of small scale karst landforms.
Similar in shape but located on the other extremity of
the chain is Punta Cupetti from where the entire
morphology of Monte Albo can easily be understood.
Punta Cupetti is also characterised by the presence of
rich micro-forms sculpted in the s’Adde limestones.

Many caves have been inserted in the database:
Conca ‘e Crapa, Su Santuariu, Omines Agrestes and
Listincu caves are horizontal relics of an ancient under-
ground and complex karst drainage system. While
Omines Agrestes and Galleria Listincu are small caves
(Dore et al., 1996), formed by karst solution along fissu-
res, Conca ‘e Crapa and Su Santuariu are much more
complex and important testimonials of ancient karst
processes. Conca ‘e Crapa is one of the highest caves
of Sardinia (1050 m a.s.l.), composed of several cham-
bers connected by crawling passages (Dédé, 1976;
Loru & Sechi, 1984), and represents a very important
habitat for cave dwelling fauna (Grafitti, 1996). Su
Santuariu, instead, is located almost 1000 meters lower

and is characterised by the presence of massive and
important concretions (Dore et al., 1996), probably
testimonials of a much wetter and warmer climate.

At even lower altitudes, at the foot of the moun-
tain, two active caves are classified as geomorphosites;
the Cane Gortoé and the Locoli resurgences. The first,
located in the centre of the village Siniscola at an altitu-
de of 40 m a.s.l. has a development of almost 1000
meters and is very important for its cave dwelling fauna
(Grafitti, 1996). Cane Gortoé contains two slowly
flowing underground rivers that meet just before exiting
the cave and represents the active base level of the
karst acquifer of Monte Albo (Mucedda, 1991). Locoli
instead has a much more impressive appearance and
becomes active only after heavy rain periods. This
cave, of great hydrogeological importance (Maccioni,
1976; Murgia, 1999) is located at an altitude of 100 m
a.s.l. and has an important underwater development
explored during the 80’s by French cave divers (Le
Guen, 1983; Pittalis et al., 1983; Isler, 1990). The total at
present explored development of this cave system rea-
ches more than 1500 meters (Perna & Murgia, 2002).

The underground river that exits the mountain
from the Locoli cave is believed to come from the
Bonaettè sinkhole, located at a distance of  approxima-
tely 4 km WNW at an altitude of 550 m a.s.l. (Sanna,
1990). This sinkhole, although not very beautiful and
active only after heavy rains, is nevertheless one of the
most didactic ones of the Monte Albo chain, and for its
hydrogeological importance this swallow hole deserves
its classification as geomorphosite. 

The current main outflow from the Monte Albo
aquifer is located close to Siniscola, near the San
Giuseppe chapel, and has been known since a long
time as the San Giuseppe or Fruncu ‘e Oche spring.
This karst spring, with a mean discharge of 80 l/s, is
developed on important fault systems at an altitude of
48 m a.s.l. (Perna & Murgia, 2002).

To explain further geological interest of Monte
Albo four non-karstic geomorphosites have been cho-
sen: the geological and tectonic features of Punta Azza
Ruja, the Punta Gutturgius palaeo-landslides, the Cuile
su Ramasinu overthrust with outcrops of the Cuccuru ‘e
Flores conglomerates and the impressive vertical cliffs
of the north-western side of the Monte Albo chain. At
Punta Azza Ruja, in the southern part of the carbonate
chain, a thick succession of basal dolomite beds dip-
ping southeast clearly shows overthrusting and faulting,
while at the foot of Punta Gutturgius Early-Quaternary
landslides have determined unusual landforms with
impressive isolated dolomite blocks. Near Cuile Su
Ramasinu, instead, overthrusting has enabled the pre-
servation of the Eocene Cuccuru ‘e Flores conglomera-
te, important testimony of the Cretaceous erosion
period.

5. CONCLUSIONS

Monte Albo is an important landscape unit that
constitutes a characteristic landmark in the north-
eastern part of Sardinia. Landforms are mainly related
to karst processes and subordinately to tectonic featu-
res. The twenty-three geomorphosites described in this
paper represent most of the morphological processes

151Karst geomorphosites ...



that this mountain went through in the past millions of
years. The connection of these geomorphosites in a
local network, comprising the realisation of equipped
pathways and the elaboration of explicative maps and
panels and a website in which geology, geomorpho-
logy, karst, fauna, flora, archaeology and industrial
archaeology are described, would be an interesting
alternative to the conventional tourist offer of this region
based on beaches and one-day trips to single tourist
sites (nuraghi, show caves etc.). In fact, the explanation
of the landscape, its evolution, its geodiversity and the
single elements it contains can help the visitors in
understanding the importance of geology and geo-
morphology on landscape evolution, biology and
human activities, that combine in an educational model
of great suggestion and efficiency.

This valorisation fits also well in the framework of
the Geomining, Historical and Environmental Park of
Sardinia of which the Monte Albo landscape unit, com-
prising the two abandoned mines of Guzzurra and Sos
Enattos, is part (Area number 6). Furthermore, the eva-
luation of the geological and geomorphological heritage
of Monte Albo enriches the classification of the area on
a pure biological basis (Cassola & Tassi, 1973) and as a
Site of Comunitary Interest (Directive Habitat 92/43, SIC
ITB001107). 

This proposal of valorisation of these landscapes
and geomorphosites could well be connected to other
areas of the region, and the Authors hope that the local
and regional stakeholders will participate in the valori-
sation of their territory, giving an important service to
the many tourists that come and visit the Monte Albo

ACKNOWLEDGEMENTS

This study has been carried out in the framework
of the National Project COFIN 2001-2003
“Geomorphosites in the Italian Landscape”, National
Coordinator Prof. Sandra Piacente of the University of
Modena, Responsibles of the Local Research Unit Prof.
Antonio Ulzega and Prof. Felice Di Gregorio of the
University of Cagliari. The comments of the two refe-
rees, Leonardo Piccini and Marco Firpo were helpful to
enhance this paper.

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153Karst geomorphosites ...