STRATIGRAPHIC ARCHITECTURE OF LATE QUATERNARY DEPOSITS IN THE LOWER ARNO PLAIN (TUSCANY, ITALY)

Abstract

Detailed sedimentological investigation of two continuously-cored boreholes, up to 106 m deep, combined with stratigraphic analysis of about 300 well logs performed for water research in the area between Cascina and the Tyrrhenian coast, reveal subsurface stratigraphy of Late Quaternary deposits in the lower Arno Plain. Facies analysis of the cores allows identification of twelve different facies associations, grouped into alluvial and coastal depositional systems. A stratigraphic cross section, roughly parallel to present Arno River and 30 km long, shows the presence of two trangressive-regressive sequences, attributed to the last two interglacial-glacial cycles (base of OIS 1 and 5e, respectively). Despite significant facies variability from proximal to distal locations, the basal transgressive surfaces appear as the most readily identifiable features from both core and borehole data, and constitute a stratigraphic marker that can be physically traced across the entire study area. The high resolution stratigraphic data shown in this paper are in marked contrast with previous work, and pro- vide a new stratigraphic framework for the upper portion of the Viareggio Basin.