Delle Rose M., 2008, The Chattian-Messinian Salento super-sequence and its relatin with tectonic and paleoclimate., GEOSED 2008, pp. 44–46, Bari, 2008,
URL: http://www.cnr.it/prodotto/i/118203

The Salento peninsula, a sub-domain belonging to the Apulia Platform (Auct.), houses continental, transitional and marine Oligocene to Miocene deposits. These terrains are arranged into a number of informal units frequently object of re-definitions, whereas only very few lithostratigraphic units were validated even if actually overstaying some questions, such as the stratigraphic relation between Andrano Calcarenite and Novaglie formation or the age of the Galatone Formation anyhow encompassing a poorly biostratigraphical defined time span between Oligocene and Miocene. As a consequence, the stratigraphic setting is interpreted in several ways that, among others things, arise the problem about the choice of the cartographic tools for the redaction of derivate maps, such as the hydrogeological hazards. This research deals with the drawing of the stratigraphic architecture of the Salento Oligocene to Miocene deposits (fig. 1), that as a whole has reference to a second order stratigraphy sequence. The tools of the research have been stratigraphic and sedimentological analyses as well as the mapping of lithozone and uncoformity surfaces. Oligocene-Miocene lie on a Cretaceous and locally Eocene substratum capped by residual deposits, dissected into horst and graben systems and intensively shaped by sub-aerial conditions during large part of the Paleogene. Marly limestones buried beneath Lecce urban area have pioneeristic referred to the Oligocene in spite of the lack of adequate studies (Palmentola, 1978). Later, probably homologous deposits, exhumed by road building excavation, were referred to Oligo-Miocene oscillating continental to marine transition (Esu et al., 1995). Very few are the knowledge about the sedimentological arrangement of this kind of sedimentary bodies. The bottom unit of the super-sequence is the Castro limestone, a reef complex built mainly by corals, that largely cropping out along the south eastern cliff of the Salento peninsula (Bosellini, 2006). It underlies the P. Badisco calcarenite through a paraconformity surface whit erosive features on which lies a discontinuous rhodolitic level. Especially the upper portion of the P. Badisco calcarenite, rich in Miogypsina sp. and well exposed along the Canaloni di Badisco, needs detailed stratigraphic and sedimentological reviews. In any case an upward regressive trend was not recognized and a correlation with the bottom stratigraphic level of the pietra leccese must be checked. The overlying high rich in phosphatized grains Aturia level is in paraconcordance without erosional shapes, letting to hypothesize a gap in the geological record without emersion. The Aturia level, a condensed phosphatized residual lag deposited on a hardground surface, is paraconformably covered by a broad glauconitic grains rich marker bed along the south east Salento coast (Delle Rose, 2001) traditionally named Piromafo. South of Otranto the following condensed succession has reconstructed_ Cretaceous substratum, bauxitic terrain, transitional to marine Oligocene and probably earliest Miocene deposits (Esu et al., 2005), Aturia and Piromafo levels, reduced Messinian (Ungaro, 1966) lumachella beds. Marine Aquitanian deposits had been recognized for the first time by Luperto Sinni (cit. in D'Alessandro and Palmentola, 1978) at Copertino; a late Oligocene-early Miocene unit (here labelled as lithozone) named "Scutelle limestones" was successively described between Nardò and Galatone (Barbera et al., 1993). Oligoaline deposits crop out east of Lecce contain abundant Metacypres gr. Danubialis, attribute to the Chattian (Conato, cit. in Del Prete and Santagati, 1972) and specimens of the striate ostracods and Darwinula aff. cylindrica, both referred to the Tortonian inside the Danube Basin (Auct.). Really the striate ostracods have very restricted biostratigraphic power whereas the chronostratigraphic span of D. cylindrica encompass a Lower Miocene-Pleistocene interval, although some Oligocene forms are again referred to such species. Samples of marls and limestones extracted by the Lecce subsoil are referred to the Galatone Formation (Bossio et al., 2006) by means of gastropods internal mould considered belong to Ampullinopsis crassantina that has undetected inside the aforementioned oligoaline deposits. Actually, the stratigraphic relationship between the NE Salento Oligocene and Miocene units are uncertain (fig. 1). Even is extensively cropping out, the boundary between pietra leccese and Andrano Calcarenite is differently interpreted either as stratigraphically continuous with or without interval of transition; heteropic, transgressive and disconformable. According to the Geological Map of Italy at 1_100.000 scale, the Miocene deposit on which Lecce had erect entirely belonging to the pietra leccese, whereas according to Bossio et al. (2006) they must be partially referred to the Andrano Calcarenite. The age corroborate by the Geological Map of Italy spanning from the Burdigalian p.p. (formerly called Elvetian) to the late Miocene (Messinian p.p.), had recently been detailed (Bossio et al., 2006). Significant thickness of pietra leccese aren't exposed whereas inside stone quarries only the middle or upper levels of the unit can be observed. The pietra leccese must be considered as both traditional and subsurface unit aiming to establish unambiguous definition in observance of the stratigraphic codes, checking excavations and boreholes to define really operable stratotype. The pietra leccese is overlaid by the Piromafo, in turn locally fades into a "glauconitic pietra leccese", that have to distinctly mapped in the perspective of a modern cartography. Moreover the passage from pietra leccese to glauconitic deposits can be related with the astronomical driven transition from the Miocene Climate Optimum to the subsequent global cooling. Also the Andrano Calcarenite record some climate events as well probably Messinian tectonic displacements; around the main horst, this formation in overlies by a chaotic assemblage, unformally know as breccia di Leuca, consists of megablocks, breccias and pebbles within heterogeneous matrix that must be separately mapped. Finally, it seems significant to carry out that the Chattian-Messinian Salento present analogies with the coeval super-sequence of the Maiella formed inside an opposite ramp of the Apulia Platform. REFERENCES Barbera C. et al., 1993. Il giacimento a scutelle di cava I Rizzi. Guida alle Escursioni XII Conv. Soc. Paleont. It., 91-96. Bosellini F., 2006. Biothic changes and their control on Oligocene-Miocene reefes_ A case study from the Apulia Platform Margin. Palaeogeography, Palaeoclimatology, Palaeoecology, 241, 393-409. Bossio A. et al., 2006. Stratigrafia neogenica-quaternaria del settore nord-orientale della provincia di Lecce. Geol. Rom., 39, 63-87. D'Alessandro A. and Palmentola G., 1978. Sabbie a brachiopodi, una nuova unità del Salento leccese. Riv. It. Paleont., 84, 1083-1120. Delle Rose M., 2001. Salento Miocene_ a preliminary paleoenvironmental reconstruction. Thalassia Salentina, 25, 41-66. Del Prete M. and Santagati G., 1972. Depositi oligoalini interposti tra calcari cretacici e pietra leccese. Geol. Appl. Idrogeol., 7, 225-233. Esu D. et al., 1995. Lagoonal-continental Oligocene of southern Apulia. Boll. Soc. Paleont. It., 33, 183-195. Esu D. et al., 2005. Late Oligocene-?Miocene mollusc and foraminiferal assemblages from the vicinity of Otranto. Rend. Soc. Paleont. It., 2, 75-85. Palmentola G., 1978. Lineamenti geologici e morfologici del Salento leccese. Atti Conv. Geol. Salento, 7-23. Ungaro S., 1966. Prima segnalazione del Miocene superiore nella penisola salentina. Mem. Museo Civ. St. Nat., 14, 435-448.

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