Chronostratigraphic confimation of MIS 5 age of a baymouth bar at Is Arenas (Cagliari, Italy)
In 2005, the National Geological Survey of Italy released the new sheet, 557 Cagliari (1:50.000 scale). A coastal barrier marine formation at Is Arenas (Cagliari, Sardinia, Italy), containing Strombus bubonius, was reassigned a Holocene age, in contradiction with extensive literature published over the past century indicating an MIS 5.5 age. In 2007, spurred by this controversy, a short note was published in Il Quaternario demonstrating the stratigraphic difficulties in attributing the age of this formation to the Holocene. Later, another paper signed by numerous Italian geologists was published in Il Quaternario criticizing the Holocene attribution. The tectonic consequences of assigning a Holocene age to these deposits are of great significance, as their elevation could only be explained by strong uplift over the past few thousand years. Such a tectonic setting would imply a radical change in the recent geodynamic history of Sardinia, which is considered to be among the most stable areas of the Mediterranean basin. This paper provides further geochronological data for a MIS 5 age for the deposits at Is Arenas. Electron Spin Resonance (ESR) analyses were performed on 4 fossil shells sampled along the fossil baymouth bar. The results established an MIS 5 age. The amino acid racemization (AAR) and U-series data that first determined a correlation with the last interglacial, Tyrrhenian age of this ancient shoreline is reviewed, with additional documentation provided by the fossil marker S. bubonius.
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