The palaeoenvironmental interpretations of coastal caves and speleothemes here discussed dealing with some examples from the south-east Salento (South Italy). Marine stillstands and glacio-eustatic speleogenesis control and climatic influences on both phreatic overgrowth and calcareous tufas speleothemes are stressed.

Since the first settlements, the flat Salento landscapes (south eastern Italy) have been modified to drain surface waters, to discharge floods and to reclaim swamps. The Asso catchment basin is part of a complex hydrological system located within a wide graben and encloses a network of natural and artificial channels joined to karst holes (ponors) owing to flooding and epidemiological problems. Presently, channels and water sinks aim to be filled with alluvium so that without periodic detritus removal they would be obstructed leading the expansion of wetlands. The Quaternary evolution is reconstructed and the analogies with the polje of similar tectonic setting and climate regions are pointed out. Finally, geo-hydrological protection issues are exposed.

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.

The stratigraphic arrangement of two Pliocene-Lower Pleistocene Salento sequences have been reconstructed by means of stratigraphic and sedimentological analyses as well as the mapping of a number of lithozones (i. e. lithological facies, unformal units) and some uncoformities. The sequences show intriguing climate proxy records as well some sedimentological response to geodynamic phases and events. A chaotic assemblage lies above the basal disconformity surface. It consists of megablocks, breccias and pebbles in heterogeneous matrix containing lens of clay and limestone, probably formed inside transitional environments subject to intense evaporation under warm and dry climate, and oolithic calcarenites with Strombus coronatus (Massari and D'Alessandro, 2000). The chaotic assemblage fades into marlstones, related to the Trubi Fm (Bossio et al., 1991), and is draped by condensed glauconitic siltstones (Zanclean-Piacenzian). These lithozones respectively represent the sedimentation of clasts dismantled during the Messinian Salinity Crisis and later settled in transitional environment, the Pliocene inundation (Iaccarino et al., 1999) and the subsequent very low rate of sedimentation period (Cita et al., 1999) during the maximum Mediterranean flood. They are separated by a paraconformity from a phosphatized rudite which represents a regional marker and whose gravitational deposition can be related to the about 2.5 My cooling onset and/or the southern Apennines Middle-Upper Pliocene tectonic phase. The previous phosphatization process of the clasts probably occurred at inner-middle shelf (Delle Rose, 2006) during the most recent extended period significantly warmer than today. The aforementioned lithozone have been recognized at the south-eastern portion of the investigated region, whereas at the opposite Triglio hydrographic basin where Salento fades into le Murge plateau, a supposed Upper Pliocene marly unit (nearly unknown in literature) is interposed between Cretaceous and calcarenites and calcilutites (Delle Rose, 2007). The calcarenites and calcilutites (Gelasian-Santernian) consist of fossiliferous intensively bioturbated coarse to fine-grained beds, supplied from an expansive source area located to the north west of Salento as far as the Murge. This facies (the High Stand Tract relative to the sea level dropping) includes the Uggiano La Chiesa formation (Auct.) and can be related to the Gravina Calcarenite Fm. It presents depositional features mainly driven by the accommodation space. Along the east Salento, it is interbedded with greenish-brown clayey lutites that represent astronomical forcing sapropelic deposits. At the top, the calcarenites and calcilutites contain Arctica islandica, somewhere inside biogenic shell concentrations (Delle Rose and Medagli, 2007). With relation to the third order sequence cycles (Haq et al., 1987; Berggren et al., 1995), the first three lithozones can be related to TB 3.4, TB 3.5 and TB 3.6, the phosphatized rudite to TB 3.7 and the calcarenites and calcilutites to TB 3.8. Along the central and western Salento, the calcarenites and calcilutites are overlain by a glauconitic sandy deposit rich in mollusc and brachiopods, especially Terebratula scillae, by means of a disconformity surface. The "brachiopods sands"( D'Alessandro and Palmentola, 1978; Delle Rose and Medagli, 2007) zone form the base deposit of the upper sequence, about which an Emilian-Sicilian age could tentatively assigned. In any case the highest sandy beds have been referred to the Pseudoemiliana Lacunosa zone (Coppa et al., 2001; D'Alessandro et al., 2004). The age of formation of the disconformity between calcarenites and calcilutites and "brachiopods sands" falls into a period characterized both of eustatic-climate sea level drop and tectonic deformation of the southern Apennine and the Apualian Foreland. In any case, this phase set a drastic change of the sediments transportation and accumulation inside the shelf, stopping or reducing the sandy supplying of the east Salento and bordering the subsequent clayey sedimentation within the central and west sectors. Where complete successions are found, as an example in the Cutrofiano area (fig. 1), the aforementioned greenish sandy deposits fades into marly-clay beds that represent the local Argille azzurre (Auct.). The latter, more and more sandy toward the top containing at least one trachyte volcanogenic decimetric bed (Delle Rose et al., 2007), are in turn locally overlie by sands probably homologous of the Monte Marano Sands Fm of the Bradanic trough cycle (Auct.). The whole Emilian-Sicilian (or early Ionian) sequence is related to the TB 3.9 third orders cycle; the origin of its upper boundary surface appear related to the begin of the "glacial Pleistocene". REREFENCES Berggren W.A. et al., 1995. Late Neogene chronology_ New perspectives in high-resolution stratigraphy. Geol. Soc. Am. Bull., 107, 1272-1287. Bossio A. et al., 1985. La sequenza pliocenica di S. Andrea (Lecce) e il suo contenuto in pesci, ostracodi, foraminiferi e nannofossili. Mem. Soc. Toscana Sc. Nat., 92, 35-93. Bossio A. et al., 1987. Stratigrafia del pozzo Poggiardo. Atti Conv. Geol. Salento, 55-87. Bossio A. et al., 1991. Note geologiche e stratigrafiche sull'area di Palmariggi. Riv. It. Paleont. Strat., 97, 175-234. Cita B.M. et al., 1999. Changes in sedimentation rates in all Mediterranenan drillsites document basin evolution and support starved basin condition after early Zanclean flood. Mem. Soc. Geol. It., 54, 145-159. Cherubini C. and Margiotta B., 1984. Caratteristiche geolitologiche e geotecniche dei depositi quaternari di Nardò. Quad. Centro Studi Geotecnici Ingegneria, 9, 3-19. Coppa M.G. et al, 2001. The Pleistocene with Aequipecten opercularis of Campo di Mare. Boll. Soc. Paleont. It., 40, 405-429. D'Alessandro A. and Palmentola G., 1978. Sabbie a brachiopodi, una nuova unità del Salento leccese. Riv. It. Paleont., 84, 1083-1120. D'Alessandro A. et al., 2004. Pliocene-Peistocene bounded by subaerial unconformities within foramol ramp calcarenites and mixed deposits. Sedimentary Geology, 166, 89-144. Delle Rose M., 2006. Mediterranean Pliocene events in the Salento geological record. Thalassia Salentina, 29, 77-99. Delle Rose M., 2007. Sedimentological features of the Plio-Quaternary aquifers of Salento. Mem. Descr. Carta Geol. D'It., 76, 137-146. Delle Rose M. and Medagli P., 2007. The Lower Pleistocene succession of Contrada Torsano. Thalassia Salentina, 30, 57-79. Delle Rose et al., 2007. Volcanogenic sediments of the Apulian Foreland_ implications on paleoenvironment and provenance. VI Forum It. Sc. Terra, Epitome, II, 147. Haq B.U. et al., 1987. Chronology of fluctuating sea levels since the Triassic. Science, 235, 1156-1167. Iaccarino S. et al., 1999. The Miocene-Pliocene boundary and the significance of the earliest Pliocene flooding in the Mediterranean. Mem. Soc. Geol. It., 54, 109-131. Massari F. and D'Alessandro A., 2000. Tsunami-related scour-and-drape undulations in Middle Pliocene restricted carbonate deposits (Salento). Sedimentary Geology, 135, 265-281.

Il Salento e le Murge, sub-paleodomini della Piattaforma Apula (Auct.), confinano lungo una fascia di deformazione tettonica con orientamento meridiano e sono caratterizzati da differenti assetti tettono-stratigrafici. Nel Salento, l'abitato di Lecce è ubicato su un horst a struttura complessa (delimitato a sud-ovest da un blocco ribassato noto come graben di Novoli) dove affiorano depositi miocenici (De Giorgi, 1922) attribuiti interamente alla pietra leccese (Rossi, 1969), oppure in parte anche alle Calcareniti di Andrano (Bossio et al., 2006). Benché una distinzione tra pietra leccese e calcareniti macrofossilifere (Lumachelle) fosse stata già introdotta da De Giorgi (1922), è solo con la redazione della IIa ed. della Carta Geologica d'Italia a scala 1_100.000 che la questione della differenziazione litostratigrafica assume la giusta rilevanza. Secondo Martinis (1967) e Rossi (1969) l'istituzione di una nuova formazione è "giustificata dal fatto che mentre nella pietra leccese i caratteri sono piuttosto costanti e uniformi, nelle Calcareniti di Andrano i caratteri sono molto diversi". Tale apparentemente vago criterio distintivo, ha contribuito a determinare nella letteratura geologica un proliferare di suddivisioni e schematizzazioni oltre a indurre ampia discrezionalità nelle distinzioni in affioramento e in perforazione. Il limite tra pietra leccese e Calcareniti di Andrano è infatti descritto come_ privo di significative discontinuità (Rossi, 1969); eteropico (Largaiolli et al., 1969); trasgressivo e discordante (Bossio et al., 1988); con interposizione di livelli di transizione (Margiotta e Varola, 2004; Bossio et al., 2006). Tuttavia, mentre per la pietra leccese manca ancora una proposta di sezione tipo e le indicazione di letteratura sull'aria tipo sono piuttosto generiche, le Calcareniti di Andrano sono state validate come formazione (Commissione Italiana di Stratigrafia, 2002). La definizione di un limite litostratigrafico così diversamente descritto in letteratura e ad andamento sub-orizzontale, costituisce una questione di rilievo anche nell'ottica della c.d. "geologia urbana", le cui tecniche di rilevamento differiscono da quelle classiche delle zone affatto o poco antropizzate, utilizzando frequentemente osservazioni su tagli artificiali (ipogei, scavi) e su campioni carotati mediante sondaggi. Le ricerche eseguite nell'area urbana ed a est di Lecce, svolte nella prospettiva di quanto indicato dalla Commissione Italiana di Stratigrafia (2003), hanno condotto ai seguenti risultati_ - la litozona di passaggio dalla pietra leccese alle Calcareniti di Andrano, tradizionalmente denominata piromafo e ben descritta già da Martelli (1931), è chiaramente individuabile anche in perforazione così come i sovrastanti strati basali della unità superiore; - il piromafo, già considerato livello guida per il Salento (Delle Rose, 2001) benché privo di un ben definito status litostratigrafico, permette correlazioni tra le successioni dell'horst di Lecce e del graben di Novoli, la cui interposta fascia di deformazione è il risultato di intersezioni tra dislocazioni NNO-SSE e NO-SE, queste ultime attive probabilmente dal Pliocene; - la base delle Calcareniti di Andrano è interessata da intensa bioturbazione con particolari icnoforme evidenziate da patine ocracee, ed è anche caratterizzabile dal punto di vista paleontologico (macrofossili); - per il passaggio piromafo/Calcareniti di Andrano viene proposta una sezione stratigrafica di riferimento completata dalla stratigrafia di un carotaggio eseguito sino al limite pietra leccese/piromafo; - nel Foglio 204 - Lecce della CGI a scala 1_100.000, il limite pietra leccese/Calcareniti di Andrano appare posto alla base di depositi riferibili a una facies calcareo-detritica (con intraclasti) delle Calcareniti di Andrano, probabilmente distinguibile anche nell'area tipo di tale formazione. Oltre alla valenza stratigrafica gli studi eseguiti assumono risalto anche in campi applicativi. Infatti il piromafo, la cui predisposizione alla carsogenesi e speleogenesi è già nota in letteratura (Tadolini et al., 1971) è sede preferenziale di dissesti idrogeologici quali sprofondamenti del suolo. Nondimeno, per l'abitato di Lecce, si segnala una discreta sovrapposizione tra gli areali di affioramento di pietra leccese, piromafo e Calcareniti di Andrano e le zone a differente pericolosità idraulica e rischio di allagamento del Piano di bacino stralcio per l'Assetto Idrogeologico (PAI) elaborato dall'Autorità di Bacino della Puglia. BIBLIOGRAFIA Bossio A. et al., 1988. Evoluzione paleogeografica dell'area di Leuca nel contesto dell'area mediterranea. Atti Conv. Conoscenze Geologiche Salento, Lecce 12/12/1987, 31-54. Bossio A. et al., 2006. Stratigrafia neogenica-quaternaria del settore nord-orientale della provincia di Lecce. Geol. Rom., 39, 63-87. Commissione Italiana di Stratigrafia, 2002. Catalogo delle formazioni-Unità validate. Apat, quaderni, serie 3, n. 7, 11-20. Commissione Italiana di Stratigrafia, 2003. Guida italiana alla classificazione e alla terminologia stratigrafica. Apat, quaderni, serie 3, n. 9, 155 pp. De Giorgi C., 1922. Descrizione geologica e idrografica della provincia di Lecce. 263 pp. Delle Rose M., 2001. Salento Miocene_ a preliminary paleoenvironmental reconstruction. Thalassia Salentina, 25, 41-66. Largaiolli T. et al., 1969. Note illustrative della CGI, Foglio 214 Gallipoli. Serv. Geol. It., 63 pp. Margiotta S. e Varola A., 2004. Nuovi dati geologici e paleontologici sul alcuni affioramenti nel territorio di Lecce. Atti Soc. Tosc. Sc. Nat., 109, 1-12. Martelli A., 1931. Sui fosfati del leccese. Boll. Soc. Geol. It., 50, 171-188. Martinis B., 1967. Note geologiche sui dintorni di Casarano e Castro (Lecce). Riv. Ital. Paleont., 73, 1297-1380. Rossi D., 1969. Note illustrative della CGI, Foglio 215 Otranto. Serv. Geol. It., 69 pp. Tadolini et al., 1971. Idrogeologica delle sorgenti Idume. Geol. Appl. e Idrogeol., 6, 41-64.