SESS 1_160211.pub Il Quaternario Italian Journal of Quaternary Sciences 24, (Abstract AIQUA, Roma 02/2011), Congresso AIQUA Il Quaternario Italiano: conoscenze e prospettive Roma 24 e 25 febbraio 2011 GEOMORPHOLOGICAL EVOLUTION OF CAGLIARI COASTAL PLAIN-CONTINENTAL SHELF SYSTEM TO LATE PLEISTOCENE- HOLOCENE TRANSITION, CORRELATIONS WITH STABLE MEDITERRANEAN SITES Paolo Orrù 1, Fabrizio Antonioli 2, Salvatore Carboni 1 & Luciano Lecca1 1. Dipartimento di Scienze della Terra, Cagliari University, Italy 2. ENEA - National Agency for New Technologies, Energy and Environment, Rome, Italy Corresponding author: P. Orrù ABSTRACT: Orrù P. et al., Geomorphological evolution of Cagliari coastal plain-continental scelf system to late Pleistocene-Holocene transition, correlations with stable Mediterranean sites. (IT ISSN 0394-3356, 2011) We report the evolutionary model of the coastal plain of Cagliari and the continental relatively late Pleistocene - Holocene, highlighting the strong linkages with similar coastal areas to its tectonic stability of the Mediterranean. RIASSUNTO: Orrù P. et al., Evoluzione geomorfologica del sistema piana costiera-piattaforma continentale di Cagliari al passaggio Pleistocene superiore-Olocene, correlazioni con siti stabili Mediterranei. (IT ISSN 0394-3356, 2011) Viene presentato il modello evolutivo della piana costiera di Cagliari e della piattaforma continentale antistante relativamente alla finestra temporale Pleistocene superiore – Olocene; ponendo in rilievo le forti correlazioni con altre aree costiere a relativa stabilità tettonica del Mediterraneo. Key words: Last Interglacial, Coastal plain, Continental shelf, Holocenic sea levels, Cagliari Gulf Parole chiave: Ultimo interglaciale, Piana costiera, linee di riva oloceniche, Golfo di Cagliari Two lagoons, closed by a system of beach ridges structured in two generations, characterize the Cagliari coastal plain similarly to other areas of the Mediterranean (FERRANTI et al., 2006). In particular, strong similarities in terms of geomorphological evolution and of depositional model are recognized, either in other coastal plains of Sardinia (Porto Pino lagoons in the Gulf of Palmas and Mistras-Cabras lagoon in the Gulf of Oristano) than in other Mediterranean coastal areas as the Plain of Fondi, in central Italy (ANTONIOLI et al., 1988 ) and in the lagoon of Santa Pola, Alicante in southern Spain (ZAZO et al., 2003). The palaeo inner beach ridges of Sa Illetta and Is Arenas have been related to the Last Interglacial (MIS 5e) using: i the Senegalese fauna as Strombus bubonius; ii the U/Th analyses on Cladocora corals; iii the aminostratigraphy analyses (ULZEGA & HEARTY, 1986). The chrono- stratigraphic age of the paleo-beach of Is Arenas (Last Interglacial) has been recently confirmed using together ESR analyses (ORRÙ, et al. 2010), and the malacofauna fossils content which includes Strombus bubonius (Fig.1). The excavation of the foundations diaphragms of the new Port Terminal of Cagliari allowed us to found continuity for the late-Quaternary succession through the system of double beach ridges of the western lagoon system (Santa Gilla Lagoon); (Fig.2). The continuity of the section allow us to follow a level containing Strombus sampled outcropping on the paleo-beach Sa Illetta, where the burrows in sandy cliffs are surmounted by a layer containing Cladocora caespitosa and calcareous algae (ULZEGA & HEARTY, 1986). We describe some new sections of the same level, highlighted on a recent excavation performed at - 15 m. On the port access channel, the underwater survey has allowed more detailed facies and Fig. 1 – Fig.1 – Strombus bubonius shell from deposits dradged at – 8,5 m (unit 3 of Fig.2), few hundred meters far from the La Plaia coast line along the entrance channel to the Industrial harbour of Cagliari Strombus bubonius provenienti dal livello dragato a – 8,5 m (unità 3 in Fig.2) in corrispondenza del canale di accesso al nuovo porto conteiner, alcune centinaia di metri al largo del cordone litorale di La Plaia. 45 - 47 46 sedimentary structures. The transition to Holocene marine deposits is marked by deep incisions founded in both coastal plain and continental shelf, these palaeo-valley began their evolution after the Last Interglacial highstand while the highest incision was carved during the MIS 2 low stand. Chrono-stratigraphic study of sediments,14C analyses of peaty, silty and sandy coastal lagoon sediments at the mouth of the lagoon of Santa Gilla, has enabled us to reconstruct the sea level rise during the Holocene (ORRÙ et al., 2004). Geophysical surveys (seismic profile Orrù et al., 2004; LECCA et al., 2005) allowed to follow the palaeo-valleys (mostly buried) carved during low stand along the continental shelf the main heads of the Canyons of the board. (FANUCCI et al., 1976) The lgm lowstand allowed also in other coastal plains the incision of palaeovalley along the continental shelf as in the Fondi fossil palaeovalley (ANTONIOLI et al. 1988). The Holocene sea level rise has been detected studying and dating (14C analyses): seven orders shelf of beach-rock outcropping on the continental shelf (ULZEGA et al., 1986) the deepest of lay at -45 m (ORRÙ et al., 2004), relict beach bordered the palaeo-lagoon (-39 m), and in the inner band (-35 m) have recently been identified and sampled the submerged back-shore sand dunes overlayed on a large fluvial fan charatterized by to medium and large polygenic gravels. A buried Punic age (2500 BP) paleo-sea level at -2 m is preserved in the bottom-area Santa Gilla lagoon (SOLINAS & ORRÙ., 2006; ANTONIOLI et al., 2007). Comparing data from the different markers studied: fossiliferous sediments from boreholes, beach- rocks, geoarchaeological markers, appear a good correspondence with the predicted sea level curve (LAMBECK et al., 2010) which indicates a relatively tectonic stability for the coastal area of Cagliari during the Holocene. REFERENCES ANTONIOLI F., FREZZOTTI M. & VALPREDA E. 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Il Quaternario. 18 (2), 202-221. Fig. 2, Geologic profile of the Lagoon of Saint Gilla - 1) grey-greenish sandy silt (Middle Pleistocene); 2) sandstones and conglomerates with burrows (Upper Pleistocene - MIS 5); 3) littoral carenites containg coastal containing Strombus bubonius and Cladocora coespitosa (Late Pleistocene – MIS 5e); 4) gray silt quartz in fluvial-deltaic peat (Late Pleistocene-Holocene); 5) littoral sandstone containing Cerastoderma and sebka beach rock - Holocenic transgression (Holocene); 6) littoral sandy gravel with Posidonia peat (Late Holocene - Present); 7) blackish silt and sandy silt of the present lagoon; 8) present sandy beach. Profilo geologico della Laguna di Santa Gilla. 1) limi argillosi e argille limose deltizie a ostree (Pleistocene medio); 2 ) limi sabbiosi ocra a burrows con lenti calcarenitiche (Pleistocene superiore – MIS 5); 3) arenarie e conglomerati litorali fossiliferi a a Strombus bubonius e Cladocora coespitosa (Pleistocene superiore – MIS 5e); 4) limi quarzosi grigi fluvio- deltizi e torbe (Pleistocene superiore-Olocene); 5) arenarie litorali a cardium e beach-rock di sebka perilagunari (Olocene); 6) ghiaie e ghiaie sabbiose di spiaggia con livelli torbosi a Posidonia oceanica (Olocene-Attuale); 7)limi e limi sabbiosi nerastri lagunari (Olocene-Attuale); 8) sabbie di spiaggia (Olocene-Attuale)  P. Orrù et al. 47 Ms. received: Testo ricevuto il SOLINAS E. & ORRÙ P. E. (2006) - Santa Gilla laguna: spiagge sommerse e frequentazioni di epoca punica, in Aequora, pontos, jam, mare. 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(2003) - Pleistocene raised marine terraces of the Spanish Mediterranean and Atlantic coasts: records of coastal uplift, sea-level highstands and climate changes. Marine Geology, 194, 103-133. January 13, 2011 13 gennaio 2011 Geomorphological evolution of Cagliari coastal ...