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.
Highlights
The high valley of the Agri River (High Agri Valley, HAV in fig. 1) is a Quaternary tectonic depression located along the axis of the Neogene-Quaternary Southern Apennines fold-andthrust belt
This paper documents the first tephra layer found within the High Agri Valley, and as such helps place the valley in tectonic context with other basins found within the Southern Apennines
Considering the importance of documenting tephrochronology histories in the Southern Apennines to constrain the timing of basin tectonism, we present a study of the tephra layer recovered in the trench
Summary
The high valley of the Agri River (High Agri Valley, HAV in fig. 1) is a Quaternary tectonic depression located along the axis of the Neogene-Quaternary Southern Apennines fold-andthrust belt (fig. 2). The HAV formed during Pleistocene-Holocene time in relation to the Mesostructural and geomorphological investigations along the Monti della Maddalena range to the west of the HAV have identified a 3.5 m high scarp which intercepts unconsolidated sediments, and this geomorphic feature likely represents the surface expression of a hidden seismogenic fault (Maschio et al, 2005). This area has been struck by destructive earthquakes, including the December 16, 1857 Imax= XI, Me= 7 event The geochemical signatures from different volcanic provinces make it possible to discriminate among sources for these distal tephra layers, this geochemical characterization is not yet sufficiently complete to unambiguously correlate individual horizons to volcanic sources in Southern Italy
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