Astronomical dating of two Pliocene alkaline volcanic ash layers in the Capo Rossello area (southern Sicily, Italy): implications for the beginning of the rifting in the Sicily Channel

Two volcaniclastic ash layers (AL1 and AL2) are intercalated throughout the middle Pliocene sedimentary sequences of Punta Piccola and Capo Rossello exposed along the south coast of Sicily (Italy). Astronomical calibration of the Punta Piccola section provided ail age of 2.676 Ma for the deposition of the AL1 layer. The high-resolution bio-cyclostratigraphy of the Capo Rossello section, in combination with detailed correlations with previously astronomically calibrated coeval sequences, provided an age of 2.225 Ma for the deposition of the AL2 layer. Mineralogical, petrographical and geochemical results from the two volcaniclastic layers suggest a Na-alkaline differentiated magnatism for the volcanic source, similar to the one which formed the alkaline rocks of the island of Pantelleria (Sicily Channel). These results indicate that isolated volcanic activity and/or early differentiated magmatic events may have occurred in the area of the Sicily channel well before the well-known late Pleistocene volcanic activity.