Stratigraphic and sedimentological insights about the Capo San Gregorio breccias and conglomerates (South Salento)

The geological literature of the south Salento peninsula (around Capo S. M. di Leuca) shows a number of chrono- and lithostratigraphic setting reconstructions surprisingly high, regarding both the Cretaceous-Tertiary platform carbonates and the Quaternary marine-continental clastic deposits. As an example, the eastern well exposed coastal cliff has been considered belonging to: a Paleocene-Oligocene Calcari di Castro formation (SERVIZIO GEOLOGICO D'ITALIA, 1968); an undifferentiated succession of pre-Neogene formations (BOSSIO et alii, 1987); a Oligocene-Miocene clinostratified slope systems including reef tracts (BOSELLINI et alii, 1999, 2001). Moreover, the outcropping carbonate substratum of the west ionian coast up to the Pesculuse littoral has been referred entirely to the Cretaceous (SERVIZIO GEOLOGICO D'ITALIA, 1968) or locally made up by Miocene formations (BOSSIO et alii, 1987; CIARANFI et alii, 1988). Along this shore tract, the breccias and conglomerates overlying the above mentioned platform carbonates at Capo San Gregorio, have been referred to: weathering continental slope deposits (SERVIZIO GEOLOGICO D'ITALIA, 1968); shoreface deposits linked to a 3-4 m a.s.l. paleo-shoreline (COTECCHIA et alii, 1969); a marine conglomeratic lithostratigraphic unit named Leuca formation (BOSSIO et alii, 1987, 2001). Preliminary stratigraphic and sedimentological observations carried out at Capo San Gregorio allow us to distinguish the main features of breccias and conglomerates and to delineate their outcropping extensions, as briefly summarized. Some units have been observed: 1) weathering continental slope deposits characterized by a medium-coarse breccia (clasts of limestones, dolomitic limestones and calcarenites) within a well cemented reddish matrix spread all around the area. Frequently are present well cemented interlayered reddish hard crusts. The whole deposit is characterized by terrace shaped morphology; 2) debris-mud flow deposits showing embricated structures, wide sorted and rich in bauxite pisolites; they are usually associated to the aforementioned slope deposits; 3) well smoothed conglomerates (mainly limestones and calcarenites content) within a well cemented yellowish carbonate matrix, characterized by a wide sorting with clasts ranging from some centimetres up to some decimetres; 4) coarse conglomeratic level at the base of cross-bedding reddish calcarenites which shows a thickness of about of 0.5 m; more or less rounded pebbles are randomly present also within the overlying calcarenites 5) intraclastic breccia layers interbedded within carbonate platform succession; the best outcrop is located in point number 3 in the attached map, where the succession is thick about 15 meters. More considerations must be done regarding the evidences of the litological features above described. Here we preliminary approach some questions. The weathering continental slope deposits are widespread along the Salento southwest coast between Pesculuse and Leuca. Its well cemented reddish matrix could emphasize continental or transitional diagenetic processes during paleo-climatic favourable conditions, meanwhile their terraced morphologies seems to be undergone to erosion processes of shoreline retreat. Moreover, breccias in reddish matrix, containing terrestrial fossil bones, are described along the east Salento coast as the result of interglacial processes (DI STEFANO et alii, 1992). The well smoothed conglomerates (1 of fig.1) are evidently shoreface deposits. According to the literature, they can indicate a Tyrrhenian high stand (COTECCHIA et alii, 1969; DAI PRA & HEARTY, 1988). At Pesculuse area (about 5 km far from Capo San Gregorio towards North-West), D'ALESSANDRO & MASSARI (1997) have been recognized shoreface limestone co