The Island of San Pietro, situated on the SW coast of Sardinia, covers an area of roughly 51 square kilometres. Geologically, the island is composed almost entirely of volcanic rock, with minor outcrops of Tyrrhenian fossil-bearing sandy conglomerates, of eolian sandstones, ancient and recent alluvial deposits, dunal sands and sediments deposited in palustrine and marshy environments. In spite of its small size, the island boasts a wealth of geodiversity, with the occurrence of a variety of effusive magmatic rocks formed during the Oligo-Miocene volcanic cycle that affected the whole of Sardinia. During this cycle numerous units were emplaced as well as various, easily distinguishable types of volcanic rocks, namely lava (rhyolite, rhyolitic ignimbrite, comendite, retinite, diaspore, etc.) and tuff (tuff, pyroclastite, cinerite, pumiceous cinerite, red and yellow ochre), sometimes with spectacular domes (for instance at Capo Sandalo and Cala Fico) manganese bearing mineralizations, emission centres, lava flow surface structures (comendite lava at Bricco di Nasca and Montagna di Ravenna), convolute flow structures (comendite lava at Cala Fico) and spectacular columnar fracturing. Detailed field surveys and laboratory investigations conducted using aerial photographs, orthophotographs and satellite images allowed to examine and classify those landforms attributable to geomorphological processes associated with water, weathering, wind and coastal dynamics. The marine environment was geologically-geomorphologically interpreted chiefly by examining the Side Scan Sonar data, supplemented with direct observations during underwater surveys. For the pericoastal areas (between 0 and -15 m), photograms and recently acquired satellite imagery were analysed. Side scan sonograms together with direct underwater observations were used to determine lithology of submerged rock outcrops, to reconstruct boundaries between different rock types, to detect evidence of tectonic lines, to determine the evolution of coastal and underwater relief forms, to identify the main sedimentary facies and evidence of sea level stand (palaeo shore line). Interpretive hypothesis of the side scan sonar data were validated by means of underwater surveys. Data from land and sea surveys were interpreted in CAD and GIS environments,
Note della Carta geomorfologica costiera e marina. Isola di San Pietro (Sardegna sud-occidentale). Scala 1:25.000
ORRU', PAOLO EMANUELE;
2010-01-01
Abstract
The Island of San Pietro, situated on the SW coast of Sardinia, covers an area of roughly 51 square kilometres. Geologically, the island is composed almost entirely of volcanic rock, with minor outcrops of Tyrrhenian fossil-bearing sandy conglomerates, of eolian sandstones, ancient and recent alluvial deposits, dunal sands and sediments deposited in palustrine and marshy environments. In spite of its small size, the island boasts a wealth of geodiversity, with the occurrence of a variety of effusive magmatic rocks formed during the Oligo-Miocene volcanic cycle that affected the whole of Sardinia. During this cycle numerous units were emplaced as well as various, easily distinguishable types of volcanic rocks, namely lava (rhyolite, rhyolitic ignimbrite, comendite, retinite, diaspore, etc.) and tuff (tuff, pyroclastite, cinerite, pumiceous cinerite, red and yellow ochre), sometimes with spectacular domes (for instance at Capo Sandalo and Cala Fico) manganese bearing mineralizations, emission centres, lava flow surface structures (comendite lava at Bricco di Nasca and Montagna di Ravenna), convolute flow structures (comendite lava at Cala Fico) and spectacular columnar fracturing. Detailed field surveys and laboratory investigations conducted using aerial photographs, orthophotographs and satellite images allowed to examine and classify those landforms attributable to geomorphological processes associated with water, weathering, wind and coastal dynamics. The marine environment was geologically-geomorphologically interpreted chiefly by examining the Side Scan Sonar data, supplemented with direct observations during underwater surveys. For the pericoastal areas (between 0 and -15 m), photograms and recently acquired satellite imagery were analysed. Side scan sonograms together with direct underwater observations were used to determine lithology of submerged rock outcrops, to reconstruct boundaries between different rock types, to detect evidence of tectonic lines, to determine the evolution of coastal and underwater relief forms, to identify the main sedimentary facies and evidence of sea level stand (palaeo shore line). Interpretive hypothesis of the side scan sonar data were validated by means of underwater surveys. Data from land and sea surveys were interpreted in CAD and GIS environments,
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