K-Ar dating of an early Middle Pleistocene distal tephra in the interglacial varved succession of Pianico-Sellere (Southern Alps, Italy)

A distal tephra has been discovered in the varved lacustrine succession of Pianico-Sellere, one of the best-preserved interglacial sedimentary assembl ages, south to the Italian Alps. The K-Ar dating of the juvenile glass frac tion gives an age of 779 +/- 13 ka. This age is supported by the observatio n of a reverse paleomagnetic direction, probably recorded before the Matuya ma-Brunhes transition dated at 780 ka. The tephra belongs to the shoshonite series and the volcanic source is likely located in Southern Italy. The ag e of 779 +/- 13 ka is much older than that of the 'Riss-Wurm' interglacial, which was previously suggested on the basis of geological setting and macr oflora studies. The Pianico tephra represents the first stratigraphical mar ker of an interglacial so far unsettled in the Southern Alps. (C) 2001 Else vier Science B.V. All rights reserved.