COBISS: 1.01

GEOMORPHOLOGICAL ANALYSIS OF KARST LANDFORMS AT THE MASSO DELLA VECCHIA GEOSITE ( PENINSULA, ) GEOMORFLOŠKA ANALIZA KRAŠKIH OBLIK NA OBMOČJU MASSO DELLA VECCHIA (POLOTOK SALENTO, ITALIJA)

Paolo SANSÒ1

Abstract UDC 551.435.8(450.75) Izvleček UDK 551.435.8(450.75) Paolo Sansò: Geomorphological analysis of karst landforms Paolo Sansò: Geomorfološka analiza kraških oblik geozname� at the Masso della Vecchia geosite (Salento peninsula, Italy) nitosti Masso della Vecchia (polotok Salento, Italija) The presence of a pedestal rock, locally named Masso della Prisotnost matične kamnine, ki jo krajevno imenujejo Masso Vecchia, marks a site of relevant geological interest (geosite) della Vecchia, je pomembna geološka zanimivost v okolici vasi in the surrounding of village (Salento Peninsula, Giuggianello (polotok Salento, Apulija, Italija). Zaradi nena- region, Italy). This unusual natural landform and simi- vadne naravne reliefne oblike te kamnine in mnogih drugih lar others occurring in the same area gave birth to myths and podobnih kamnin, ki se pojavljajo na tem območju, so nastali legends. A detailed geomorphological analysis of Masso della številni miti in legende. Naredili smo podrobno geomorfološko Vecchia area has been carried out. The site is placed at about analizo Masso della Vecchia. Študijsko območje je okoli 100 m 100 m of altitude on a lower Pleistocene abrasion surface which nad morjem na abrazijskem območju iz spodnjega pleistocena, constitutes the top of the Serra di morphostructural ki je pravzaprav vrh morfostrukturnega grebena Serra di Po­ ridge. Locally, the Miocene Pietra Leccese Formation crops out. ggiardo. Krajevno se iz kamnin miocenske starosti na površju It is constituted by poorly consolidated, bioturbated, yellowish pojavlja Pietra Leccese. Sestavljen je iz slabo strjenih, biotu­ biomicrites at lower levels rapidly grading upward in massive rbacijskih rumenkastih biomikritov, ki se na nižjih ravneh grainstones rich in glauconite minerals. The entire sequence hitro vzpenjajo v masivni grainstone, bogat z mineralom gently dips northeastward. The geomorphological analysis re- glavkonita. Celotna sekvenca je rahlo nagnjena proti severov- vealed that the Masso della Vecchia and similar landforms oc- zhodu. Geomorfološka analiza je pokazala, da so Masso della curring in the area are karstic features produced under a soil Vecchia in podobne reliefne oblike, ki se pojavljajo na območju, cover. Pinnacles, channels, notches, subsoil scallops, half-bells kraške in da so nastale pod pokrovom prsti. Prepoznali smo and other typical features have been recognized. The peculiar vrhove, kanale, zareze, podtalne fasete, polzvonove in druge assemblage of subsoil karst features can be explained taking tipične oblike. Svojevrsten skupek podtalnih kraških oblik je into account the geological structure, subsoil karst processes mogoče razložiti z upoštevanjem geološke strukture, podtalnih and the geomorphological evolution of this area during the kraških procesov in geomorfološkega razvoja tega območja v Late Pleistocene. času poznega pleistocena. Key words: subsoil karren, geoheritage, Salento, Italy. Ključne besede: podtalne škraplje, naravna dediščina, Salento, Italija.

Introduction

A natural monument marks a site placed in the surround- rock called by local people “lu furticiddhu de la vecchia ing of Giuggianello, a small village of southern Salento de lu Manni” (i.e. the spindle used by a witch to make (Apulia region) (Fig.1). It is constituted by a pedestal yarn) or more simply “Masso della Vecchia” (i.e. the large

1 Di.S.Te.B.A., Università del Salento, Italy, e-mail: [email protected] Received/Prejeto: 04.05.2016

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Fig. 1: The grey box indicates the geographical position of Masso della Vecchia area (Giuggianello, Salento Peninsula).

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 Fig. 2: The Masso della Vecchia pedestal rock in a XIX century Masso della Vecchia, was broken in piece by a mine few drawing of Cosimo De Giorgi. years before. Finally, the author informs readers that the Royal Government classified the Masso della Vecchia as block of the witch). Numerous local legends arouse from National Monument of First Category. De Giorgi (1879) the occurrence of this unusual landform. resumes De Simone (1872) data, reporting also the near- De Simone (1867) reported for the first time the by occurrence of a mushroom-like rock which lost its presence in the Salento peninsula of this mushroom-like top stone and of another rock shaped as an anvil. This rock, even if he wasn’t able to indicate precisely its posi- author refers the development of these particular rocks tion. Maggiulli (1871) considered it a megalithic monu- to weathering process even if he doesn’t rule out that ment whereas Botti (1871) referred its origin to weather- these natural landforms could be used as sacred places ing processes reporting examples of similar landforms in by prehistoric men. Italy (“pile di formaggio” at Elba island, “pietra ballerina” The geomorphological singularity of theM asso della near Nuoro, Sardinia) and in Europe (Central Massif of Vecchia pedestal rock justifies its presence in the inven- France, “cheesewring” in Cornwall, “Herkulessaulen” at tory of geosites recently realized by the Regione Puglia Bielagrund, Switzerland). Administration (Mastronuzzi et al. 2015).

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Notwithstanding all this, no specific research to ral monument has been performed; it defined the main describe the geomorphological features at Masso della morphogenetic processes responsible for landforms gen- Vecchia site and to explain their genesis and evolution esis as well as allows the morphogenetic evolution of lo- has been carried out so far. Aiming to fill this gap, a geo- cal landscape to be reconstructed. morphological survey of the area marked by this natu-

GEOLOGICAL AND GEOMORPHOLOGICAL SETTING

The Salento peninsula is the southernmost emerged uplift of the Apulia foreland after the general subsidence part of Adria Plate which constitutes the foreland of took place in the early Miocene period; uplift ended at both Apenninic and Dinaric orogens. It comprises a Marine Isotope Stages (MIS) 9.3, about 330 ka BP (Mas- Variscan basement covered by a 3–5 km thick Meso- tronuzzi et al. 2007). Since then, maximum uplift rates zoic carbonate sequence (the Calcari delle Murge unit) have been recorded only in the Taranto area (0.25 m/ka overlain by thin Tertiary and Quaternary deposits. according to Ferranti et al. 2006), whereas they decrease The most ancient rocks of this cover were produced to zero in the southernmost part of the region. Finally, by transgressions after the definitive emersion of the a slow subsidence has been recorded along the Salento Apulian carbonate platform occurred between the end peninsula coast during the last four millennia (Mas- of the Cretaceous and the beginning of Paleogene peri- tronuzzi & Sansò 2014). ods; in some cases, bauxitic deposits can be found be- The Salento peninsula is a low-elevated landscape tween Mesozoic limestones and Paleogene units (Dog- composed of a number of Pleistocene plains placed lioni et al. 1994). at different altitude between sea level and 160 m of el- Four sedimentary cycles have been recognized evation. They are bordered by geomorphically degraded from Neogene to Lower Pleistocene periods (Giudici fault scarps, mostly elongated in NW−SE and NNW−SSE et al. 2012). The first cycle comprises the Pietra Leccese directions, by differential erosion scarps, and by relict Formation and the overlying Calcarenite di cliffs. Along the Salento peninsula coast a number of Formation. The Miocene sedimentary cycle was inter- marine terraces, produced by the superimposition of rupted because of the emersion of Salento which pre- regional uplift and glacio-eustatic sea level changes oc- vented the formation of Messinian evaporites. The total curred since the Middle Pleistocene period, can be rec- thickness of Miocene formations is greater than 150 m ognized. on the eastern side of the peninsula. The second cycle is In particular, the inner and western parts of the represented by breccias and conglomerates of the Leuca Salento Peninsula show a landscape produced by con- Formation that was deposited during the Lower Plio- tact karst processes made of wide karstic surfaces, rem- cene, reaching a maximum thickness of 30 m. The third nants of a Middle Pleistocene sedimentary cover and sedimentary cycle is represented by the Upper Plio- morphostructural ridges. The karstic surfaces belong to cene Formation, composed of well- a re-exhumed landscape shaped between the Lower and stratified and fossiliferous biodetritical limestones and the Middle Pleistocene whereas the morphostructural yellowish calcareous sands with a maximum thickness ridges are made of Mesozoic dolomitic-carbonatic units of about 80 m. The fourth sedimentary cycle promoted and show a polycyclic landscape (Selleri et al. 2003). the deposition in the Lower Pleistocene of the Calcar- However, sinkholes are the main karstic landforms in eniti del Salento Formation, a very fossiliferous biode- many sectors of Salento affecting all outcropping car- tritical calcareous sediment marked by the occurrence bonate rocks, including the Cretaceous limestone, the of Artica islandica Linneo. Its maximum thickness is of Oligocene, Miocene, and Plio-Pleistocene calcarenites, about 60 m. Finally, a number of Middle-Upper Pleis- and the middle-upper Pleistocene terraced marine de- tocene deposits related to eustatic sea level change can posits. They are widespread especially along the low el- be found on the Salento peninsula (Hearty & Dai Pra evated rocky platforms occurring both on the Adriatic 1992; Mastronuzzi et al. 2007). and Ionian coasts and display different typologies and Three main tectonic events affected the Salento Pen- states of activity (Delle Rose & Parise 2002; Bruno et al. insula during the Eo-Oligocene, the Middle Pliocene, 2008). and the Middle Pleistocene periods. In particular, the most recent tectonic phase was responsible for the final

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GEOMORPHOLOGICAL AND GEOLOGICAL FEATURES OF MASSO DELLA VECCHIA GEOSITE

The Masso della Vecchia pedestal rock is placed on the is represented by a peritidal succession showing thin top surface of a morphostructural ridge, locally named and rare inter-supratidal algal mats (stromatolites) and Serra di Poggiardo, bordered by two low NNW−SSE marked by quite common discontinuous concentrations trending scarps. Its top surface is a plain mainly shaped of rudist fragments and bioclastic grainstone as well as on Cretaceous limestone but also on Oligocene, Mi- frequent flat pebble intraformational breccias. The Cal- ocene and Lower Pliocene units (Fig. 3). It is placed at cari di Altamura Formation has been referred to the late about 100 m above m.s.l. and gently slopes from the SSE Campanian – early Maastrichtian (Parente 1994). The to the NNW. A number of wide and shallow karstic de- remnants of a bauxitic cover can be recognized on the pressions can be recognized on this plain surface. From Cretaceous limestones; it is in some places buried under a genetic point of view, it could be referred to a marine small patches of two Oligocene lithostratigraphic units abrasion surface shaped at the end of Lower Pleistocene – the Galatone Formation and the Formation while along the eastern Salento coastal slope the Porto –, none cropping out in the studied area. The Salento calcarenites were depositing (Tropeano et al. bauxite derived by the erosion of a weathered pristine 2004). deposit formed most likely during the middle Campa- Locally, on the ridge top surface three main lith- nian emersion event under dry warm climatic condi- ostratigraphic units crop out (the Calcari di Altamura tions (Mongelli et al. 2015). Formation, the Pietra Leccese Formation, the Calcareniti The Pietra Leccese Formation is typically repre- di Andrano Formation), arranged in a monoclinal gently sented by biomicrites, badly stratified in thick beds, with dipping towards NNW (Fig. 4). Two younger units (the prevalent calcareous plankton, generally straw-coloured, Leuca Formation and the Sabbie di Uggiano Formation) green in colour only in the upper part due to the abun- can be recognized in correspondence of the lower elevat- dance of glauconite. The formation is transgressive on ed plains stretching at the foot of Serra di Poggiardo on different pre-Neogene units through a conglomeratic its western and eastern slopes (Bossio et al. 2005). level marked by phosphatic nodules or pebbles and mac- The Calcari di Altamura Formation is a thick, rofossils. Occasionally, this level is replaced by a phos- shallow water carbonate succession deposited in shelf phatic film covering surfaces or filling bedrock cavities interior environments. In the studied area this unit (Mazzei et al. 2009).

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.

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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.

In the studied area three distinct lithofacies have 2005). The relatively small thickness of this unit in com- been surveyed. The base is marked by a brownish con- parison with its duration (approximately 11 Ma) is in- glomeratic level, about 20–30 cm thick, made of partly terpreted as a consequence of repeated action of marine phosphatized limestone pebbles, phosphate nodules, nu- currents that inhibited deposition and/or eroded the merous phosphastized fossils and reworked bauxitic pi- previously deposited sediments. The related hiatuses are soliths. Yellowish biomicrites made of prevailing calcare- generally outlined by the presence of more or less abun- ous plancton with variable cementation follows upward; dant glauconite grains, a typical mineral of dynamic ma- this level is constitutes by layers up to 2 m thick showing rine environment. sparse fossils (mainly pectinids) and several bioturbated The Pietra leccese Formation is everywhere overlied levels. The local sequence is closed by greenish glauco- by the Calcareniti di Andrano Formation which repre- nitic biomicrites, without stratification, very rich in fos- sents the regressive sequence of the Late Miocene sedi- sils in the uppermost levels, often clustered in layers, and mentary cycle. This cycle was interrupted by the uplift of in small brownish phosphatized grains. Salento peninsula occurred just before Messinian salin- The Pietra Leccese Formation has been referred to ity crisis. The Calcareniti di Andrano Formation reaches the late Burdigalian-early Messinian (Mazzei et al. 2009). a thickness of about 50 metres; it is made of different Its maximum thickness is about 90 m in the Lecce type carbonatic deposits which are well stratified and very area whereas it is about 35 m in the - fossiliferous. The unit can be entirely referred to the pre- area and only 17 m in the studied area (Bossio et al. evaporitic Messinian.

GEOMORPHOLOGICAL FEATURES OF THE MASSO DELLA VECCHIA GEOSITE

A detailed geomorphological survey has been carried out The survey allows four groups of landforms marked aiming to provide a quantitative description of the singu- by peculiar features to be identified which are spatially lar landforms occurring at Masso della Vecchia geosite as arranged in belts stretching roughly in SW−NE direc- well as to define their genesis and evolution. tion as well as two sinkholes (Fig. 5).

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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.

a) Groups of peculiar landforms faces: the lower surface, extended nearly vertically from Starting from the SE, the first group is formed by elon- soil level up to 1.0 m, is marked by well-developed sub- gated rock pinnacles which studded a cultivated field; soil scallops whereas a smooth gentler surface occurred pinnacles in some cases are one parallel each other and in the upper part. A break-in slope separates the two divided by narrow corridors, about 4–5 m large (Fig. 6). surfaces (Fig. 7). Most of pinnacles were modified by farmers that ripped Rocky outcrops prevail northwestward where the and accumulated rock slabs around main outcroppings. second group of blocks can be found just at the border Pinnacles are about 2 m high and 10 m long and are between olive groves and cultivate fields. This group is shaped into the Pietra Leccese yellowish biomicrites. The marked by pedestal rocks included the suggestive Mas- pinnacle surface shows subsoil karstic microforms like so della Vecchia (block 0), the mushroom-like rock de- cavernous weathering and subsoil scallops. scribed in the previous chapter (Fig. 8). Its stalk is made The small group of pinnacles placed to the eastern- by three strata of yellowish biomicrites showing in some most part of the studied area (blocks 7) can be referred areas cavernous weathering whereas the capstone is made to this group. They are up to 1.6 m high, about 4.5 m of a massive glauconitic layer. The pedestal rock stands long and 2.0 m large. They show two different rock sur- on a rocky platform, affected during the XIX century by

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Fig. 7: The surface of block 7, belonging to group 1, is affected by Fig. 9: A view of block 5 (group 2) from south. It is a less promi- well-developed subsoil scallops (sensu Zseni 2009) and cavern- nent pedestal rock showing a stalk about 1.0 m high. The litho- ous weathering. structural difference between the cap rock, made of massive glauconitic calcarenites, and the stalk, constituted by laminated biomicrites, can be easily recognized.

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 Fig. 10: Block 1 (group 3) shows a well-developed notch at its and short axis 2.85 m; the block thickness at its centre is about base. Notch is about 1.6 m deep and shows its edge is at about 2.30 m. Three strata of yellowish biomicrites showing in some ar- 1.3 m from the soil surface. On the foreground a half-bell can be eas cavernous weathering constitute the stalk. recognized. a small quarry activity (De Giorgi 1879), bordered by A notch marks the base of the block; notch’s edge is at two main karstic corridors developed along main joints. about 1.3 m from the soil surface whereas the maximum The same lithological sequence gives rise to another depth of about 1.6 m is reached at the block base. The less prominent pedestal rock (block 5) about 120 metres lower section of the notch (about 0.8 m from soil sur- to the northeast of the Masso della Vecchia. The rock stalk face) is shaped on the yellow biomicrites, the top on a is about 1.0 m high from soil surface and is constituted massive glauconitic layer. by weakly cemented, laminated and bioturbated yel- The last group comprises low karren pinnacles di- lowish biomicrites whereas the top block is about 0.8 m vides by narrow depressions filled by soil developed thick, about 5.4 m long and 3.0 m large (Fig. 9). along main joints (grikes), striking about N150E–N170E. The third group is placed inside a wide olive grove Pinnacles are bordered at ground level by subcutaneous and comprises rocks showing a prominent notch at the channels with subcircular transverse section up to 50 cm base. Block 1 offers the best example; it has an ellipsoidal high and 20–30 cm wide (Fig. 11). In Fig. 12 the peculiar shape (long axis length 9.5 m, short axis length 6.0 m) profiles of some blocks surveyed at Masso della Vecchia and elevates about 2.3 m from ground surface (Fig. 10). area are reported.

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Fig. 11: A view the subcutaneous channels with subcircular Fig. 14: The sinkhole S1 has been partly filled by farmers with transverse section that mark the borders of blocks belonging to rock slabs. The surface of one of these slab is marked by well- de- the Group 4. veloped subcutaneous channels that, accordingly to the local tra- ditions, resembles the Hercules’ foot.

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. 15: N-S (below) and E−W (above) cross profiles of sinkhole S1. The sinkhole shows an elliptical shape with main axis about Fig. 13: The sinkhole S1 opens at the bottom of a morphological 50 m long. Sinkhole bottom is about 2 m lower than surrounding depression, roughly circular in shape, showing a diameter of 50 m. level topographic surface.

b) sinkholes Two sinkholes have been surveyed in the third group them showing well-developed rundkarren (subcutane- area (S1 and S2 in Fig. 5). The largest one (S1) has been ous channels sensu Slabe 1999) (Fig. 14). The sinkhole S1 partly filled by farmers with rock slabs (Fig. 13), one of opens at the bottom of a roughly circular morphological

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DISCUSSION

The geomorphological analysis of Masso della Vecchia Numerous classifications of subsoil karst landforms area points out an epikarst marked by peculiar land- have been proposed so far (e.g. Bögli 1960; Jennings forms shaped on the Miocene Pietra Leccese Formation 1971, 1985; Gams 1976; Slabe 1999; Ford & Williams such as pinnacles, channels, notches, subsoil scallops, 2007; Slabe & Liu 2009); in this paper the classification half-bells and so on. The epikarst consists of a near sur- of Zseni (2009) has been adopted. face zone of weathered rock with high secondary poros- The influence of local stratigraphic sequence as ity that can outcrop directly at the surface or occur im- well as the geological structure on karstic process can mediately beneath the soil (Williams 2008). The epikarst explain the present morphology of the local landscape. is tipically 3–10 m deep but its characteristics can vary Starting from an even abrasion plain presently placed at considerably according to lithology and geomorpho- about 100 m of elevation, karstic processes have been re- logical history. The high porosity and permeability of sponsible for the geomorphological evolution of the area the epikarst arises from an intense carbonate solution (Fig. 16). Due to the geological structure the yellowish because of proximity to the main source of CO2 pro- laminated biomicrites crop out at Group 1 area; subsoil duction in the soil. Soil, in fact, has an important role solution has been responsible for the widening of main in the evolution of different karst features (Zseni 2009). fracture planes and for the development of elongated In general, forms which develop in open-air conditions pinnacles, which became more and more prominent as are fretted and sharp, having been subjected to much soil level lowered due to corridors deepening and wid- more selective corrosion due to episodic dissolution by ening. The occurrence of the deep karstified Mesozoic rainwater so that only the rapidly soluble constituents limestone basement close to ground surface enhanced of the rock will be removed. On the contrary, the so- surface lowering in response to soil transfer in epikarst lution of limestone is more intense under a soil cover cavities. due to the higher CO2 concentration and the longer In Group 2 area, a massive grainstone bed overlies time period of direct water-rock contact. In the case of yellowish laminated biomicrites. Here differential weath- subsoil solution, in fact, CO2 and other acids produced ering due to soil cover has been responsible for the mod- by the breakdown of the organic matter by microor- elling of some pedestal rocks, whose height lowers from ganisms living in the soil add to the CO2 dissolved by SSW to NNE. Historical data indicate that at least two rainwater from the air. The macroflora produces CO2 large pedestal rocks have been destroyed. directly through respiration of roots. For this the net- In Group 3 area, deep and high solution notches work of fissures through which percolation water passes formed along the border of larger outcrops, particularly is widened by dissolution near the surface but the extent at the contact between massive grainstone/yellowish and frequency of widening diminished gradually with laminated biomicrites. depth. Solutionally enlarged joints taper downwards Finally in Group 4 area, solution channels and sub- and become less numerous (Williams 1983). Since soil soil enlargement of main joints affecting massive grain- is often washed down into the larger grikes, lowering stone outcroppings can be detected. of the soil surface down the developing cleft, possibly The geomorphological analysis of the local land- also with soil loss into near surface cave systems, can scape suggests that the subsoil karstic process responsi- result. The distribution of subsoil solutional landforms ble for the particular morphology of Masso della Vecchia depends on soil moisture, drainage rates, soil texture, area can be referred to a morphogenetic phase occurred soil depth, water-flow rates, slope, vegetation, and the in the Upper Pleistocene. In fact, in this period a SW−NE nature of the limestone. extensional tectonic phase reactivated the NW−SE and

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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. NNE−SSW faults (Di Bucci et al. 2009, 2011) influenc- phauna that refers subsoil karst development to the Last ing karst landforms development (Festa et al. 2012; Pepe Interglacial Period (Pandolfi et al., in press). Moreover, & Parise 2014) under humid-warm climatic conditions the same morphogenetic phase most likely promoted which promoted intense subsoil karst processes respon- the development of numerous solution pipes in homog- sible for the widening of joints and cutters development enous Pliocene and Pleistocene calcarenites cropping in Pietra Leccese Formation. These processes are well out at several coastal areas of Salento peninsula (Marsico documented in literature since cutters, locally named et al. 2003; De Waele et al. 2010). “ventarole”, preserve in their filling a rich vertebrate fossil

CONCLUSIONS

The assemblage of peculiar landforms occurring in the notches and grikes formed where weak biomicrites are Masso della Vecchia area can be explained taking into covered by massive grainstones. Smaller subsoil karren account the geological characteristics and the geomor- produced by karst processes are recognizable such as phological evolution of Serra di Poggiardo area. An abra- subcutaneous channels, subsoil scallops and half-bells. sion surface formed during lower Pleistocene, presently The morphogenetic phase responsible for the de- at about 100 m of altitude, cut strata belonging to the velopment of Masso della Vecchia landforms assemblage Miocene Pietra Leccese Formation which are locally ar- can be referred to the Last Interglacial Period when a ranged in a monoclinal structure slightly dipping north- tectonic extensional phase along with warm humid cli- eastward. matic conditions promoted subsoil karstic processes. Starting from this abrasion surface, subsoil karst The present research could be the first step for the processes have been responsible for the soil surface low- geotouristic promotion of this very peculiar site of Salen- ering due to joints enlargement. The particular litho- to peninsula aiming to improve significantly the cultural stratigraphical characteristics of Pietra Leccese Forma- touristic offer in the Salento peninsula and to increase tion and the gently dipping of strata to the NE justify the the number of Italian and foreign tourists during low- occurrence of pinnacles where poorly consolidated, bio- season periods. turbated, yellowish biomicrites crop out. Pedestal rocks,

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