Three broad sets of geomorphic processes are principally responsible for landscape modelling and for carving the wide variety of landforms occurring in the Pollino Park: tectonics, river dissection, and karst processes. These geomorphic processes, combined with a high degree of geological diversity (structural frame and contrasting rock erodibility), give rise to a landscape alternating between steep mountainous districts and hilly areas.
In this regard, the Pollino Park features a wide range of landscapes and landforms that have long captivated some geoscientists. Here below, we describe the widest range of geomorphological features, with the aim of fascinating all readers about this wild and appealing landscape.

Geographical setting

This part of southern Apennines is characterized by an asymmetrical topographic profile. The summit line of the mountain belt is locally shifted toward the inner (i.e. Tyrrhenian) margin and does not correspond to the regional water divide. Consequently, the eastern flank of the chain has a greater length and a lower mean gradient than the western flank. The highest summits exceed 2000m a.s.l, whereas the mean elevation of the whole belt is about 650m asl. Many of the highest peaks offer wonderful panorama of the of Basilicata and Calabria landscapes.
In particural, the Pollino Ridge is a NW-SE trending morpho-structure made of Meso- Cenozoic carbonate rocks. It is classically interpreted as a simple homoclinal structure dipping to the NE under ophiolitic nappes which were emplaced in early Miocene time. The Pollino ridge is bordered by Quaternary basins filled by both marine and continental sediments.
Because of its geographic position and its mountainous nature, the Pollino National Park records a high climatic variability. The climate is Mediterranean with montane modifications (wetter summers and colder winters, with more than one month of snow cover). There is a strong precipitation gradient ranging from 300 mm to 1,500
mm. However, based on the analysis of daily and monthly rainfall concentration, the eastern side presents a greater seasonality of rainfall distribution, with high- intensity, short-duration thunderstorms (maximum daily rain up to 120 mm) strongly affecting the total yearly rainfall volume.

Geological control on processes and landforms

The landscape of the Pollino National Park is strongly controlled by lithology and structure, as well as by the intense uplift occurred during the Quaternary. This area lies in one of the most geodinamically active sectors of the central Mediterranean area, where complex crustal deformation is occurring as a result of the Africa- Europe collision, still active.
The core of the massif consists of Meso-Cenozoic carbonate units and Mesozoic Ophiolitic units covered by Neogene foredeep and late Miocene to Quaternary wedge-top basin clastics.
The formation of the Pollino landscape took place mainly during Quaternary time, strongly influenced by the tectonic history together with the action of geomorphic processes resulting from the main climate variations.
The main geomorphological units that can be recognized in the area are as follows:

• Carbonate mountainous massifs, with karst landscapes, bounded by deep structural slopes and some wide piedmont areas; these massifs host major cave systems and are important water storage zones.
• Terrigenous mountainous massifs, with jagged crests and deeply incised ravines.
• Marly-clayey hills, with gentle slopes and a dendritic drainage pattern.
• Intermontane basins and alluvial plains.

Tectonic and Structural Landforms

The imprint of tectonics on geomorphology of the Pollino is evident not only in the size, extent, and location of landforms, but also in the steepness of river profiles, the feature of mountain slopes, and in the pattern of river network.
Tectonics influences geomorphological processes and landforms through the direct action of faulting and the indirect influences of spatial variability in rock erodibility, and the effects of geological structure. Notably, the present landscape of the south- western slope of the Pollino Ridge is strongly related to tectonic activity, whereas structurally controlled erosional features dominate the north-eastern side. In addition, the different landscapes are due to the competing influence of bedrock on both sides of the Pollino Ridge.
The most impressive tectonic feature of the region is represented by the Pollino fault zone, which forms a NW-striking normal fault belt that runs more or less continuously along the Calabria-Lucania boundary continuing towards the SE in the Calabrian offshore. Some segments of the fault systems are still active, making the area a key point for characterising the seismic hazard of northern Calabria.
The fault belt is made up of some segments showing an overall en-echelon arrangement and formed by southwest-facing normal fault segments that strongly articulate the Pollino Ridge.
These fault segments exhibit very sharp rectilinear escarpments, locally showing well developed triangular facets separated by wineglass canyons. They are tens to hundreds of metres in height and noticeable from the A3 Highway, state roads (Fig.10) and many panoramic viewpoints.

Fig. 10. Highway A3 (Salerno-Reggio Calabria); view from the north of NW-trending Pollino fault scarp hanging relics of the gently rolling landscape.

Moving to the northeast, several pieces of evidence highlight the key role of lithological controls, through which geological structure receives its topographic expression. Conversely, it is hard to discern a clear topographic signature of tectonic landforms because of high rates of erosional processes. Nevertheless, through the indirect influences of spatial variability in erodibility generated by faulting and juxtaposition of rocks with variable erosion resistance, the influence of faults on landscape is easy to detect (fault line scarp, Fig. 11).

Fig. 11. Timpa San Lorenzo homoclinal ridge. Worthy to note are the fault line scarp (blue arrows) bordering the southwestern slope of Timpa San Lorenzo, and the T. Raganello gorge (red arrow) noticeable in the upper reach.

Because of lithological heterogeneity, a diverse gallery of homoclinal ridge eroded onto Meso-Cenozoic carbonates is evident (Fig. 11). Notably, the Neogene sedimentary succession is strongly characterized by small-scale landforms (hogback and stepped slope) which develop according to the dip of the beds.

Fluvial processes and landforms

Fluvial processes and landforms reflect the morphology of highlands, major slopes and piedmont zone. Moving from the Pollino highland, streams change dramatically becoming roaring torrents excavating deep gorges and canyons with riverbeds excavated on bare rock or locally lined with very coarse-grained, lag deposits.
Anomalous drainage bucks structural controls, flowing across geological and topographic units. A common anomalous pattern occurs where a major stream flows across a mountain range. Such transverse drainage has prompted a variety of hypotheses: diversion, capture or piracy, antecedence, and superimposition.
In particular, superimposed drainage develops when a drainage network established on one geological formation cuts down to, and is inherited by, a lower and harder geological formation. The superimposed pattern may be discordant with the structure of the formation upon which it is impressed. Lao (Fig. 12) and Raganello (Fig. 11) gorges are considered two example of superimposed valley. Indeed, both rivers cut through the more erodible ophiolitic units and are held up by the harder, underlying limestone and dolostone. Furthermore, several pieces of evidence highlight the key role of river piracy that occurred during the erosive exhumation of the carbonate heights. River capture phenomena resulted from headward retreat of river valleys facing the sea, also favoured by coastal uplift, and by selective dismantling of highly erodible material overlying carbonate rocks.

Fig. 12. Overview of Tectonic and fluvial landscapes noticeable in the Pollino National Park. View from the south of Mt. Gada-Mt. Rossino ridge.

Intramontane-valley fans are uncommon, but piedmont fans are very widespread throughout the Pollino southern slope, and show no evidence of current activity.

Stepped landscapes

Since the Pliocene, contractional structures have been superimposed by extensional faults, which have fragmented the Calabria region into structural highs and subsiding basins. Since the Early-Middle Pleistocene, Apennine experienced strong uplift, largely coeval with motion on extensional faults.
It is worthy to emphasise that above the fault scarps produced by these fault belt crossing the chain, the landscape is dominated by hanging remnants of gentle land surfaces, which locally form a staircases up to 2100m a.s.l. These land surfaces can be related to the oldest stages of landscape evolution occurred during Early-Middle Pleistocene through relief smoothing erosional and depositional processes.
In this regard, the Mercure and Castrovillari basins (Fig. 13) provide the best evidences of these step-like distributed surfaces very useful to reconstruct the main
stages of landscape evolution during the Quaternary.

 

Fig. 13. (A) Morphostructural sketch map and morphostratigraphic section of the Mercure intramontane basin showing the main recognized tectonic landforms and the distribution of the palaeolandscapes.(B) Block diagram showing the main depositional stages, landscapes and landforms of the Castrovillari basin.

Fig. 14. (A) Sketch of karst plateau area, where ponors fed by a blind valley transport rainwater down to the basal water table through vertical cave systems; 1) blind valley, 2) ponor, 3) solution doline, 4) collapse sinkhole, 5) vertical cave system, 6) karst resurgence, 7) fossil phreatic cave, 8) basal spring, 9) active phreatic karst system. (B) The Timpone del Castello gently rolling landscape is widely characterized by surface karst landforms reported in (A); Red and blue arrows indicate part of the complex Deep Seated Gravitational Slope of Civita and the T. Raganello gorge, respectively.

Karst landforms

The calcareous zone of the Pollino National Park is pivotal to explain how karst processes act within a carbonate massif and how they influence underground water storage and circulation In particular, the Pollino area may be considered one of the best example of a karst massif in Southern Italy. Notwithstanding the abundance carbonate massifs in southern Apennines (Matese Mts., Picentini Mts. and Alburno-Cervati Mts.), the Pollino massif preserves similar karstic environment (deep and large caves), variety (i.e. active and fossil phreatic caves, contact ponors, polje) and beauty.
For example, moving on to the karst plateau upward of Frascineto (Fig. 14), there are several evidences of surface karst landforms from where waters come in (e.g. ponors, blind valley) even though how underground water circulates inside a karst massif is still to be well understood.
Furthermore, many cave systems should be explored for research topics and to assess their potential interest in geo-tourism terms and to provide a valid example
for further geo-itinerary planning.
This could give visitors hands-on experience of the fascinating underground world created by the waters during their path within a limestone massif.
It is noteworthy that many karst plateaus, locally constituting stepped landscape, are interpreted as border polje that developed through karst processes at the contact between limestones and erodible materials.

Glacial landforms

The highest peaks of the Pollino Nationakl Park (Mt. Pollino, 2267 m; Mt La Mula, 1935m, Mt. Cozzo del Pellegrino, 1987) show clear traces of glaciers (Fig. 15). The glacial remains consist in some cirques and cirquelike forms, and in some morainic alignments dating from the LGM and their retreat phases During the LGM, on Mt. Pollino the equilibrium line altitude was 1800 m. One rock glacier has been also found on Mt. Pollino. It overlies the moraine of the early phases of glacial retreat, about 1750 m a.s.l; it is older than the stadial moraine covered by loess dated 15-16,000 years BP.

Fig. 15. Location of cirques and morainas on (A) Mt. Pollino, (B) Mt. Cozzo del Pellegrino, (C) Mt. La Mula

The majority of the rock glaciers were formed between 20,000 and 10,000 years BP, when the mean yearly temperatures were still 4–6 °C lower than the present ones; however, their geographic distribution gives rise to some important considerations.
The geographical distribution of the rock glaciers, corresponding to the boundary of the areas with mountain permafrost, suggests that, during the final phases of the LGM period, in the Late Glacial and in the early Holocene, there was also an altitude and latitude shift with a reduction of this boundary, following the temperature increase. From the altitude of 1570/1600 m, the boundary of discontinuous mountain permafrost rose to 2300/2500 m during the late Holocene, and it is now even higher. About the time of the latitude shift, the boundary migrated northwards, from 39°55'N to 41°45'N and later to 42°07'N.
Cryoplanation terraces and pediments may also features, although their genesis and significance is still to be assessed. In fact, gently rolling landscapes may be also developed by different processes and at different rates as locally suggested by their non-glacial appearance and presumed long periods of formation.

Slope processes and landforms

Slope processes and landforms are widespread throughout the Pollino Massif, particularly where high erodibility lithologies crop out.
Sharp increase in slope gradients marks the transition to the downstream area, where deeply incised valleys originate, the thickness of regolith strongly decreases and slope movements becomes the dominant process. Landslides are widespread and intense, and form all-size scars, scree slopes and landslide-related fans. However, due to outcropping of more erodible rocks, the lucanian side is more deeply dissected and affected by deep-seated mass-movement. Literature data highlighted that factors favouring such morphogenetic attitude to mass-movement are the extremely pervasive and intense tectonic deformation of rocks along with clay content.
On calcareous bedrock, the main mass movement is the complex Deep Seated Gravitational Slope of Civita (Fig.5) whose development is strongly controlled by a fault zone. It reach relevant dimensions, being about 2-km wide with a maximum local relief exceeding 600 m.
On ophiolitic units and Neogene outcropping sedimentary rocks, landforms depend on the dominance of mass-movement or running-water modelling processes. Where flysch and clayey melange significantly outcrop, a wide range of landslides occurs among which earth slide and flow are the predominant phenomena, and may reach very large dimensions. Alternating weak and resistant lithologies also provides
fascinating landslide scenarios.
On silty marls and onto old landslide bodies, badlands also develop. It is noteworthy where strongly fractured Meso-Cenozoic limestones and dolostones with marly intercalations crop out (e.g. near Mormanno) ; rocky slopes are deeply incised by steep flanked V-shaped gullies, outlining a badland-like drainage network.

Conclusions

The Pollino National Park provides a wide range of rocks, geological environment and tectonic structures. The entire area exhibits a variety of landscape that result from the interaction of tectonic uplift, river dissection, rock erodibility, and slope processes, which giving rise to a landscape alternating between steep mountainous districts and hilly areas. At times, landscapes are arranged in such a beautiful, ever- changing scenario that some landscapes may be considered unique and incomparable geomorphological examples, making the Pollino National Park potentially one of the most significant earth science sites in South Italy and a valid example for geo-tourism.
Notwithstanding its ease to access, it would be desirable that the geological and geomorphological significance of Pollino improves in the future by attracting more and more scientists and people, which may enhance its importance as a training ground for research programmes and recreation activities in a wonderful scenery overhanging the Tyrrhenian and Ionian seas.

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