1,721,053 research outputs found
Alluvial fans at Cala Gonone (Sardinia), a fast developing touristic village: origins, hazards and potential risks
Full text linkThe study area of Cala Gonone in NE Sardinia (Italy) consists of a wide terraced re-entrance/valley crowned inland by carbonate hills and, near the coast bounded laterally and partly floored by thin basaltic lava lying over carbonate bedrock. In this re-entrance, several inland alluvial fans (500 m length by 700 m wide) have developed, and a local ~ 30 m high, about 10 m wide (thick), 400 m long scarp body-remnant of semi-consolidated alluvial fan deposits is exposed along the coast. The fans experience depositional events mostly developed during the late Pleistocene. They although nowadays dormant may be reactivated by major rainstorms during strong climate changes. In these last few decades, the touristic village of Cala Gonone has been rapidly expanding over the mid to lower parts of two coalescing alluvial fans (Stadium and Gustui) and along the coastal marine scarp edge (Palmasera alluvial fan system). The village thus may become exposed to natural hazards if extreme climatic conditions may re-occur. Moreover, rock falls and the instability of the costal scarp due to wave erosion may add addition hazards for habitations built near the scarp crest and visitors to the frontal replenished beach. As commonly occurring elsewhere since antiquity, the risk perception of such events is low because of the centennial, millennial of longer recurrence. Such perception does not negate the hazards but a long event recurrence may be accepted as a reasonable risk for the human’s activity. Nevertheless, serious consideration should be given to potential problems and plan and build for amelioration and defense. The evidence of what environmentally did and could still happen in the Cala Gonone and similar other area is in part clearly imprinted on the landscape: geology, geomorphology, and relative details in the stratigraphy and sedimentology of the deposits
Transgressive dune formation along a cliffed coast, NW Sardinia (Italy): a record of Late Pleistocene climate change
No full textNew estimation of the post little ice age relative sea level rise
Full text linkThe study area is located in NW Sardinia Island (Italy), Mediterranean Sea. Sardinia is considered stable since the late Pliocene with a negligible subsidence of about 0.01 mm/y. It is therefore normally used to reconstruct the Pleistocene and Holocene sea level curves. Our research focusses on the sea-facing city of Alghero that from 1353 to 1720 was under the Spanish government. During this time, the city was renovated and new buildings edified. Dimension stones were quarried all around Alghero both in the nearby inland and along the coast. Coastal quarries were considered the most suitable for both rock quality and the easiest way to transport the quarried material by boat. The quarried rocks are late Pleistocene dune and beach sandstones deposited from the 132 ka (Marine Isotopic Stage-MIS5) to about 65 ka (MIS4). Sandstones crop out from few cm to 3 m above the present sea level and underwent several consolidation processes related to loading and marine weathering. This latter favoured dissolution and circulation of calcium carbonate which cemented the rocks. It is reported that the Spanish were looking for these "marine" sandstones for their high geotechnical characteristics. Different rules were adopted through time for the size of the dimension stones and this has allowed us to establish a quarry exploitation chronology. For example, "40 x 60 x 20" cm was the size of the dimension stones used for the Alghero Cathedral dated at 1505-1593. Nowadays most of the coastal Spanish quarry floors are 30 centimetres below mean sea level (tidal range is 30 cm). Accordingly, we infer that relative sea level from 1830 AD (and of the Little Ice Age) rose in about 200 years to the present level at the rate of about 1.4 mm/y. Considering that relative sea level rise during the Medieval warm period was of 0.6 mm/y over a period of about 400 years, we may deduce that human influence was strong enough to lead to a relative sea-level rise faster and in shorter time
I depositi tardo quaternari della Sardegna Settentrionale: implicazioni paleogeografiche e paleoclimatiche
No full textUpper Pleistocene coastal deposits of West Sardinia: a record of sea level and climate change
No full textIntertidal upper pleistocene algal build-ups (Trottoir) of NW Sardinia (Italy): A tool for past sea level reconstruction
No full textBiological sea level indicators such as intertidal coralline red algal build-ups (Lithohyllum rim or Trottoir) are a powerful tool for precise sea level reconstruction. Several patches of relict intertidal Lithophyllum Trottoir crop out along the north-west Sardinia coasts (Mediterranean Sea, Italy). Based on the strathigraphic correlations and preliminary luminescence ages (avg 120±8 ka) these algal bindstones are associated with the Marine Isotope Stage 5e (MIS 5e, 135-115 ka). A Sedimentological/stratigraphic approach performed on relict Mediterranean Algae Trottoir led us to developed an evolution model and precisely estimate the relative sea level elevation during MIS 5e along the NW coast of Sardinia. Moreover, coastal feature plays a vital role for “Lithophyllum incipient Trottoir” development which under a stable sea condition may growth up to the mature tabular Trottoir aspect. The mean elevation of the studied MIS 5e Lithophyllum bioconstructions is 4.9±0.5 m above the present sea level, which is in good agreement with both the global and the regional data
High energy beaches system developing during MIS 5c high sea-stand (100 Ka), north-west Sardinia, Italy
No full text- …
