THE FRENCH CONNECTION: FIELD MAPPING AND TECTONIC RECONSTRUCTION OF THE PERMIAN-TRIASSIC CALA VIOLA-LU CAPARONI SEQUENCE (NURRA, NW SARDINIA, ITALY)

The paleogeographic reconstruction of the Corsica-Sardinian block and the opening of the western Mediterranean basin remain somewhat controversial aspects of the tectonic history of the region. Some workers infer a simple counter-clockwise rotation of an intact Sardinia-Corsica block away from the southern margin of France; others reconstruct Sardinia farther to the west, separately from Corsica. One potential constrain on the paleogeographic reconstruction of Sardinia comes from comparison of Permo-Triassic basins found in western Sardinia and portions of the complimentary rifted margin of southern France. For example, similar Permian-Triassic continental sequences are located between Cala Viola and Punta Lu Caparoni, NW Sardinia, and on continental Europe in the Toulon Basin (Provence, Southern France). The stratigraphy of this Lower Permian to Middle Triassic sequence in NW Sardinia was recently redefined and stratigraphic correlations to the similar succession of the Toulon Basin have been made. The volcanic-sedimentary stratigraphic units reflect three main depositional cycles ranging in age from Early Permian to Early Triassic. The first cycle, Early Permian in age (“Autunian”), unconformably overlies the Variscan basement and is made up of alluvial-to-lacustrine deposits with intercalations of calc-alkaline ignimbrites. The second cycle, Early to Late Permian age constraint, is represented by alluvial deposits ranging from a meandering to braided stream setting. The third depositional cycle marks the beginning of the Triassic and is made up of coarse to fine-grained aeolian and fluvial deposits. Detailed field mapping (1:5,000 and 1:10,000 scale) and structural analysis of the Cala Viola-Lu Caparoni field area is presently underway to more completely test correlations with the French Permo-Triassic basins. Further mapping of this area and possible mapping in southern France will help unravel the complex tectonic history of Sardinia and provide a better basis for tectonic models of the opening of the western Mediterranean.