L'evoluzione geomorfologica della pianura del fiume Volturno (Campania) durante il tardo Quaternario (Pleistocene Medio-Superiore - Olocene)

Abstract

The geomorphological evolution of the Volturno river coastal plain between Late Mid-Pleistocene and Holocene times has been reconstructed. The recostruction in based on data from natural outcrops, data from ~ 600 existing boreholes drilled in the area and 3 new boreholes drilled in the area. The age model relies on 230Th/234U dating of fossiliferous layers present in the cores. The succession is made up of 6 stratigrafie units: (1) the lowermost is represented by marine sediments, the top of which is dated to 126 ±11 kyr BP and has been correlated with the Cancello terrace; (2) pyroclastic and lava deposits ranging from 126 ± 11 to 42 kyr BP and which have been correlated with 2 pumice outcrops located on the eastern edge of the Volturno plain; (3) transitional and marine deposits relating to isotopie substage 3.3, dating to 55÷50 kyr BP (Martinsons et al., 1987); (4) Campanian Ignimbrite Auct. dating to 42 ÷ 27 kyr BP (Scandone et al., 1991); (5) locally reworked pyroclastic deposits belonging to the IV Phlegrean period (Di Girolamo et aL, 1984); (6) clay, silt and peat layers of lagoonal environment of Holocene age (10 kyr BP onwards). Sedimentation has been influenced by non-homogeneous tectonics. During the first half of the Upper Pleistocene the whole area was subsiding, and at a higher rate in the southwestern sector, a marine environment lasted throughout the period in the central sector of the plain, despite pyroclastic aggradation. In the latter part of the Upper Pleistocene reduced subsidence and negative glacioeustatic fluctuation lead to total emersion of the plain; subaerial erosion dates to this period. Tectonic uplifting of some tens of metres in the northeastern edge of the plain also took place: morphological and archaeological data indicate continuation of uplifting well into historical times. The central and coastal parts of the plain have not been subjected to tectonic activity since the deposition of the Campanian Ignimbrite. This area was progressively invaded by the sea during the Versilian transgression, and marshes persisted in the area up until Borbonic reclamation during the 18th Century.