A well-established Early–Middle Pleistocene marine sequence on south-east Zakynthos island, western Greece: magneto-biostratigraphic constraints and palaeoclimatic implications MARIA D. PAPANIKOLAOU, 1 * ,y MARIA V. TRIANTAPHYLLOU, 2 ELLEN S. PLATZMAN, 3 PHILIP L. GIBBARD, 1 CONALL MAC NIOCAILL 4 and MARTIN J. HEAD 5 1 Department of Geography, University of Cambridge, Downing Place, Cambridge CB2 3EN, UK 2 Department of Historical Geology–Paleontology, University of Athens, Panepistimioupoli 15784, Athens, Greece 3 Department of Earth Sciences, University of Southern California, 3651 Trousdale Pkwy, Los Angeles, CA 90089, USA 4 Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK 5 Department of Earth Sciences, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario L2S 3A1, Canada Received 31 March 2010; Revised 10 October 2010; Accepted 13 October 2010 ABSTRACT: The chronostratigraphy of a long, onshore Early–Middle Pleistocene marine sedimentary sequence on the south-east part of Zakynthos island, Greece, is presented. Correlation of the succession with the isotope record of Ocean Drilling Program Site 963 reveals the combined influence of tectonics and eustacy in this area. The sequence is divided into three formations by two main unconformities that apparently relate to sea-level lowstands associated with two major northern hemisphere glaciations, those of marine isotope stages (MIS) 22 and 12. The Zakynthos sequence in many ways is comparable with the Italian Valle di Manche section. Magnetostratigraphic and rock magnetic analyses, supported by biostratigraphy, document the position of the Matuyama/Brunhes Chron boundary (0.77 Ma), the top and base of the Jaramillo Subchron (0.99–1.07 Ma), the Cobb Mountain Subchron (1.173–1.185 Ma) and the top of the Olduvai Subchron (1.78 Ma). The underlying strata are constrained exclusively by detailed nannofossil biostratigraphy extending at least to the lowermost Pleistocene at around 2.54 Ma and therefore certainly incorporating the base of the Olduvai Subchron (1.95 Ma) and possibly the Gauss/Matuyama Chron boundary (2.58 Ma). In addition, a remarkable increase in sedimentation rate (from 3.2 and 28 cm ka 1 to 167 cm ka 1 ) and hence resolution above the Matuyama/Brunhes boundary (Middle Pleistocene) reveals one short-lived magnetic excursion, possibly 17a (0.66 Ma), within the normal polarity Brunhes Chron. Copyright # 2011 John Wiley & Sons, Ltd. KEYWORDS: magnetostratigraphy; nannofossils; palaeoclimate; Quaternary; rock magnetics. Introduction The Mediterranean is renowned for its continuing tectonic activity that has contributed to the formation of thick marine sedimentary sequences now exposed onshore as a con- sequence of ongoing uplift. The geodynamic regime of the Mediterranean has been particularly active since the Miocene, which explains the numerous Neogene and Quaternary sections, particularly in the central–eastern Mediterranean. These uplifted sections are closely related to the subduction of the Ionian crust (relics of the Tethyan Ocean) under the Eurasian plate, which has given rise, for example, to the Calabrian and Hellenic arcs. The disappearing Ionian crust between the Hellenic arc to the east and the Calabrian arc to the west constitutes part of the common subducting (e.g. Royden, 1993) or detached (e.g. Wortel and Spakman, 2000) slab. The global stratotype section and point (GSSP) for the Gelasian Stage (2.58 Ma; Gibbard et al., 2010; Gibbard and Head, 2010) is therefore unsurprisingly located in Italy, as is the Semaforo– Vrica section (Fig. 1) in Calabria, southern Italy, which formerly served as the GSSP of the Plio-Pleistocene boundary (Aguirre and Pasini, 1985) and remains available as the GSSP for the Calabrian Stage (Gibbard et al., 2010; Gibbard and Head, 2010). We note that the Pleistocene and Quaternary are now both defined by the Gelasian Stage GSSP at Monte San Nicola in Sicily, their bases dated at 2.58 Ma (Head et al., 2008a; Gibbard and Head, 2009a,b, 2010). Two candidate GSSPs for the Middle Pleistocene Series (Head et al., 2008b), the Valle di Manche section (Capraro et al., 2005) and Montalbano Jonico section (Brilli et al., 2000; Stefanelli et al., 2005; Ciaranfi and D’Alessandro, 2005), are also located in Italy (Fig. 1). Although the candidacy of Montalbano Jonico is now in question owing to difficulties in obtaining a reliable magnetostratigraphy, the recent astronomical tuning of this section (Ciaranfi et al., 2010) nonetheless highlights its importance. A series of Quaternary marine sequences in Greece occurs in Crete (e.g. Tortorici et al., 2010), Kephalonia, (Keraudren, 1970; Triantaphyllou et al., 1999) and Rhodes (Corne ´e et al., 2006; Steinthorsdottir et al., 2006; Joannin et al., 2007). None of these, however, is as long and continuous as the Gerakas peninsula composite section in south-east Zakynthos. The post- orogenic sedimentary succession on the Gerakas peninsula was first described by Keraudren (1970). Detailed geological mapping by Dermitzakis et al. (1979) proved the existence within the Quaternary sequence of two similar yet separate unconformities that had often been regarded as one. A comparable Pleistocene two-conformity-bound sedimentary succession has also been recognised in the central-northern Zakynthos island (Papanikolaou et al., 2010). The Quaternary sequence on the Gerakas peninsula comprises three formations that have been studied earlier for their micropalaeontological content, namely ostracods (Tsapralis, 1981), nannofossils (Triantaphyllou, 1996; Triantaphyllou et al., 1997), foramini- fera (Blanc-Vernet et al., 1979; Hinsbergen, 2004) and dinoflagellate cysts (Papanikolaou, 2008), and for their palaeomagnetic implications (Duermeijer et al., 1999; Broad- ley et al., 2006). Previous palaeomagnetic studies examined the Tertiary deformation of the Ionian zone, including Zakynthos island, by determining the rotation that discrete areas have undergone through time. Laj et al. (1982) sampled, along with JOURNAL OF QUATERNARY SCIENCE (2011) 26(5) 523–540 ISSN 0267-8179. DOI: 10.1002/jqs.1462 Copyright ß 2011 John Wiley & Sons, Ltd. *Correspondence: M. D. Papanikolaou, E-mail: maria.papanikolaou@cantab.net y Present address: Department of Dynamic, Tectonic and Applied Geology, University of Athens, Panepistimioupoli, 15784 Zografou, Greece