The beaches examined lie on the southeast coast of Sardinia, North of Cape Carbonara. The outcropping rock types consist almost entirely of rocks belonging to the Hercynian batholith of the Sarrabus region, primarily of the Cape Carbonara granodiorites (NICOLETTI et alii, 1983), leucogranites in some places also with pegmatoid facies and locally of basic differentiates embedded in small masses of syenite and gabbro-diorite (BROTZU P. & MORBIDELLI L, 1974, BROTZU et alii 1978). Acid and basic dykes, striking prevalently NW-SE, corresponding to Late Hercynian faulting, (BROTZU P. & MORBIDELLI L, 1974) cut through the granitoid complex. Apart from the cover of Quaternary alluvial debris, along the coast above the abraded surface of the granites, strips of Quaternary marine to continental deposits occur, dated to no older than the last interglacial age (PALMERINI, 1974; ORRÙ et alii, 1994). The morphology of both relief and coast is determined by the presence of nearly vertical dykes. These dykes form the central nucleus and the ribbing of the mountainous backbones, determining the same NW-SE trend and creating rocky promontories along the coast, alternating with more or less deep inlets occupied by bay beaches. The hydrographic network consists of intermittent streams with low sediment input. The continental shelf is a few miles wide and its extension is structurally controlled by mainly N30E striking Alpine tectonic lines (LECCA et alii, 1979). The physiographic unit studied stretches over almost two kilometres, in a roughly NNE-SSW direction, between the granite promontories of Torre di Porto Giunco to the South and Is Traias to the North. In the central part small portions of the granite basement crop out interrupting continuity of the shoreline and separating the Porto Giunco beach to the S from the Simius beach, to the N. The beaches have a typical transverse profile comprising a backshore, foreshore, and wide surf zone with bars and troughs. In the western portion of the physiographic unit, which is not supplied directly by the watercourses, lies a remnant coastal dune system including foredunes, consisting upstream of incipient blowouts. In the eastern portion only remnant foredunes can be recognized. Behind the Porto Giunco beach lies a small lagoon, while a small stretch of marshland used to back onto the Simius beach but most of it has now disappeared. The surf zone is characterized by a bar and trough system with maximum width of 320 m. In the autumn up to three submerged bars have been observed. Mean annual energy transferred to the shore by wave motion is less than 1x106 tm/m (ATZENI & GINESU, 1993). Energy flow direction is from NE to SW (R. A. S.,1987).
Regime, dynamics and sedimentological characteristics of the Porto Giunco and Simius beaches - south east Sardinia
DEMURO, SANDRO;IBBA, ANGELO;
2003-01-01
Abstract
The beaches examined lie on the southeast coast of Sardinia, North of Cape Carbonara. The outcropping rock types consist almost entirely of rocks belonging to the Hercynian batholith of the Sarrabus region, primarily of the Cape Carbonara granodiorites (NICOLETTI et alii, 1983), leucogranites in some places also with pegmatoid facies and locally of basic differentiates embedded in small masses of syenite and gabbro-diorite (BROTZU P. & MORBIDELLI L, 1974, BROTZU et alii 1978). Acid and basic dykes, striking prevalently NW-SE, corresponding to Late Hercynian faulting, (BROTZU P. & MORBIDELLI L, 1974) cut through the granitoid complex. Apart from the cover of Quaternary alluvial debris, along the coast above the abraded surface of the granites, strips of Quaternary marine to continental deposits occur, dated to no older than the last interglacial age (PALMERINI, 1974; ORRÙ et alii, 1994). The morphology of both relief and coast is determined by the presence of nearly vertical dykes. These dykes form the central nucleus and the ribbing of the mountainous backbones, determining the same NW-SE trend and creating rocky promontories along the coast, alternating with more or less deep inlets occupied by bay beaches. The hydrographic network consists of intermittent streams with low sediment input. The continental shelf is a few miles wide and its extension is structurally controlled by mainly N30E striking Alpine tectonic lines (LECCA et alii, 1979). The physiographic unit studied stretches over almost two kilometres, in a roughly NNE-SSW direction, between the granite promontories of Torre di Porto Giunco to the South and Is Traias to the North. In the central part small portions of the granite basement crop out interrupting continuity of the shoreline and separating the Porto Giunco beach to the S from the Simius beach, to the N. The beaches have a typical transverse profile comprising a backshore, foreshore, and wide surf zone with bars and troughs. In the western portion of the physiographic unit, which is not supplied directly by the watercourses, lies a remnant coastal dune system including foredunes, consisting upstream of incipient blowouts. In the eastern portion only remnant foredunes can be recognized. Behind the Porto Giunco beach lies a small lagoon, while a small stretch of marshland used to back onto the Simius beach but most of it has now disappeared. The surf zone is characterized by a bar and trough system with maximum width of 320 m. In the autumn up to three submerged bars have been observed. Mean annual energy transferred to the shore by wave motion is less than 1x106 tm/m (ATZENI & GINESU, 1993). Energy flow direction is from NE to SW (R. A. S.,1987).
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