Tephrochronology in faulted Middle Pleistocene tephra layer in the Val d’Agri area (Southern Italy)

Abstract

The High Agri River Valley is a Quaternary Basin located along the hinge of the Southern Apennines fold-andthrust belt. The inner margin of the orogen has been affected by intense transtensional and normal faulting, which accompanied vigorous volcanism during the Quaternary. Marker tephra layers are distributed across the whole of Southern Italy and provide a powerful tool to constrain both the size of eruptions and the regional activity of extensional faults controlling basin evolution. Paleoseismological trenching within the Monti della Maddalena range, that borders the Agri River Valley to the south-west, has exposed a faulted stratigraphic sequence and recovered a 10 cm thick tephra layer involved in deformation. This is the first tephra horizon recognized in the high Agri Valley, which, based on the stratigraphic study of the trench, lies in a primary position. 40Ar/39Ar dating constrain its age to 266 ka and provide an important marker for the Middle Pleistocene tephrochronology of the region. Together with dating, geochemical analysis suggests a possible volcanic source in the Campanian region.

Keywords

• tephra layer
• 40Ar/ 39Ar dating
• Southern Italy