The Y-3 tephra: A Last Glacial stratigraphic marker for the central Mediterranean basin G. Zanchetta a,b, ⁎, R. Sulpizio c , B. Giaccio d , G. Siani e , M. Paterne f , S. Wulf g , M. D'Orazio a a Dipartimento di Scienze della Terra, University of Pisa, via S. Maria 53, I-56126 Pisa, Italy b IGG-CNR Via Moruzzi, 1, 56100 Pisa, Italy c CIRISIVU, c/o Dipartimento Geomineralogico, University of Bari, via Orbona 4, I-70125, Bari, Italy d Istituto di Geologia Ambientale e Geoingegneria, CNR, via Bolognola 7, 00138, Roma, Italy e FRE 2566 Orsayterre Universitè Paris XI 91405 Orsay, France f Laboratoire des Sciences du Climat et de l'Envirnment, CNRS-CEA 91198 Gif sur Yvette, France g Institute for Geophysics, Jackson School of Geosciences, The University of Texas, J.J. Pickle Research Campus, Bldg. 196,10100 Burnet Rd., Austin, TX 78758-4445, USA abstract article info Article history: Received 15 January 2007 Accepted 31 August 2007 Available online 14 September 2007 Keywords: tephrostratigraphy tephrochronology Y-3 Central Mediterranean Campanian volcanoes The paper reviews the existing data on the Y-3 tephra layer, first recognised in the Ionian Sea (Mediterranean basin). The collection and collation of old and new data on distal tephra occurrences in terrestrial, marine and lacustrine successions indicate that the Y-3 layer is dispersed over a wide area of the central Mediterranean basin. The peculiar homogeneous chemical composition of this layer makes its recognition rather straightforward and permits it being distinguished from other stratigraphically adjacent tephras. The best age estimate for the Y-3 layer of ca 30–31 cal ka BP, its peculiar stratigraphic position close to the Marine Isotope Stage 3/2 transition or Heinrich Event 3 onset, as well as its wide dispersion makes this layer an important marker to link and date late Pleistocene terrestrial and marine archives of the central Mediterranean basin. © 2007 Elsevier B.V. All rights reserved. 1. Introduction The Last Glacial was characterised by frequent pronounced and rapid climatic oscillations, which can be recognised in different natural archives. Although these climatic oscillations were first recognised in the North Atlantic area (e.g. Johnsen et al., 1992; Bond et al., 1992; Dansgaard et al., 1993), recent studies have demonstrated that these events also brought about climatic changes in southern Europe and the Mediterranean basin (e.g. Allen et al., 1999; Bartov et al., 2003; Genty et al., 2003; Martrat et al., 2004; Drysdale et al., 2007). However, the frequency of these oscillations makes it very difficult to correlate among different natural archives, and often even the 14 C dating method, the most common geo-chronometer for dating the latter half of the Last Glacial period, does not provide the required precision to resolve the rate of recurrence of the climatic changes. In addition, the 14 C method is often affected by uncertainties related to hard water and reservoir effects, and to the calibration of raw data between ca 20,000 and 50,000 yr; indeed, a universally accepted calibration curve for the interval between ca 20,000 and 50,000 is not yet available (e.g. Hughen et al., 2004; Fairbanks et al., 2005). In areas characterised by recurrent volcanic explosive activity, one alternative approach for dating different natural archives is the use of volcanic ash layers or tephras (e.g. Keller et al., 1978; Turney et al., 2004; Wulf et al., 2004). Deposition of distal ash layers can be considered isochronous over large areas, and it can physically link together different successions. To be a useful tool for a stratigraphic and chronologic correlation, a tephra layer recovered in different archives must have some basic characteristics: i) it should be chemically and petrographically distinguishable from other volcanic layers; ii) it should have widespread dispersion for regional to extra- regional correlation although less dispersed tephras can be useful for local correlations; iii) it should be accurately dated. Points i) and ii) are important for defining a robust stratigraphic, physically-based frame- work of tephra-bearing archives, whereas point iii) is important for controlling the age model of archives dated with different methodol- ogies. It is obvious that the most favourable situation occurs when the complete identity of the volcanic layer is available. This implies that the volcanic source of the tephra is well constrained and the geochemistry, stratigraphy and the chronology of the explosive eruption is well known in proximal areas. In this case, the recognition of a tephra layer in distal archives is also useful for volcanological studies, such as the correct estimation of the erupted volume and definition of the area affected by pyroclastic deposition (e.g. Fierstein and Nathenson, 1992; Sulpizio, 2005). Journal of Volcanology and Geothermal Research 177 (2008) 145–154 ⁎ Corresponding author. Dipartimento di Scienze della Terra, University of Pisa, via S. Maria 53, I-56126 Pisa, Italy. E-mail address: zanchetta@dst.unipi.it (G. Zanchetta). 0377-0273/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jvolgeores.2007.08.017 Contents lists available at ScienceDirect Journal of Volcanology and Geothermal Research journal homepage: www.elsevier.com/locate/jvolgeores