Late Quaternary climatic evolution of the Arno coastal plain (Western Tuscany, Italy) from subsurface data

A multidisciplinary study of a 105-m-long core was carried out on the Tyrrhenian coast of Tuscany, Western Italy. Detailed description of sedimentary facies, foraminifer and ostracod assemblages, pollen, and 14C ages is presented in this paper.Identification in core of two transgressive surfaces (TSs) as the most prominent stratigraphic markers allows subdivision of the Late Quaternary stratigraphic succession into two transgressive–regressive (T–R) sequences, attributed to the last 150 kyr BP. Sequence boundaries have no unequivocal physical expression in the core.Detailed pollen analysis documents a direct relationship between vertical facies evolution and climate fluctuations. Coastal to shallow-marine sediments in the lower part of T–R sequences were deposited during the last two interglacial periods (OIS 1 and 5e), under rising sea-level conditions and during the following sea-level highstands. By contrast, alluvial sedimentation (upper part of T–R sequences) took place during periods of sea-level fall and subsequent sea-level lowstands, and was invariably linked to the onset of glacial periods (OIS 4–2 and 6, respectively).This paper presents the first detailed facies documentation of a Late Quaternary incised-valley fill sequence from Italy. About 51 m of Holocene sediments are recorded beneath the present Arno River valley. Early transgression is documented in the lower part of the incised-valley fill by wave-dominated estuarine facies overlying lowstand fluvial deposits. Late transgression records the rapid landward migration of a beach-barrier system, followed by the establishment of an open-marine environment. Highstand sedimentation is represented by a shallowing-upward succession, which reflects progradation of the modern delta/strandplain.