The depositional and postdepositional features observed in the sediments of the coastal system of Portixeddu-San Nicolao (SW Sardinia) have been analyzed. The depositional features include grain size, mineralogic composition, roundness of quartz grains, coatings of syn-depositional silica while the postdepositional features comprise the presence of carbonate cement, pink colouration, secondary silica deposition. The samples, collected on foreshore, foredune, man-stabilized dune, naturally stabilized dune and Pleistocene dune have grain size distibutions and mineralogic composition consistent with depositional environment and paleozoic basement. On the contrary, SEM examination of the surface textures of quartz grains shows considerable variability from the foreshore to the oldest dunes. It is pointed out that the primary marine surface textures may be progressively modified and obliterated by aeolian transport and by pedogenetic processes. The latter, on the man-stabilized dunes, can occur within 50 years.
CARATTERI SEDIMENTARI DEL SISTEMA SPIAGGIA-DUNA DI PORTIXEDDU - S. NICOLAO (SARDEGNA SO)
IBBA, ANGELO;
2010-01-01
Abstract
The depositional and postdepositional features observed in the sediments of the coastal system of Portixeddu-San Nicolao (SW Sardinia) have been analyzed. The depositional features include grain size, mineralogic composition, roundness of quartz grains, coatings of syn-depositional silica while the postdepositional features comprise the presence of carbonate cement, pink colouration, secondary silica deposition. The samples, collected on foreshore, foredune, man-stabilized dune, naturally stabilized dune and Pleistocene dune have grain size distibutions and mineralogic composition consistent with depositional environment and paleozoic basement. On the contrary, SEM examination of the surface textures of quartz grains shows considerable variability from the foreshore to the oldest dunes. It is pointed out that the primary marine surface textures may be progressively modified and obliterated by aeolian transport and by pedogenetic processes. The latter, on the man-stabilized dunes, can occur within 50 years.
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