408 by Maria Bianca Cita1, Luca Capraro2, Neri Ciaranfi3, Enrico Di Stefano4, Fabrizio Lirer5, Patrizia Maiorano3, Maria Marino3, Isabella Raffi6, Domenico Rio2, Rodolfo Sprovieri4, Simona Stefanelli3, and Gian Battista Vai7 The Calabrian Stage redefined 1 Università di Milano, Dipartimento di Scienze della Terra “Ardito Desio”, via Mangiagalli 34, 20133 Milano, Italy. E-mail: [email protected] 2 Università di Padova, Dipartimento di Geoscienze, via Giotto 1, 35137 Padova, Italy. 3 Università di Bari, Dipartimento di Geologia e Geofisica, via Orabona 4, 70125 Bari, Italy. 4 Università di Palermo, Dipartimento di Geologia e Geodesia, via Archirafi 22, 90123 Palermo, Italy. 5 Istituto per l'Ambiente Marino Costiero (IAMC), CNR, Calata Porta di Massa, 80133 Napoli, Italy. 6 Università di Chieti-Pescara, Dipartimento di Geotecnologie per l'Ambiente ed il Territorio, via dei Vestini 31, 66013 Chieti Scalo, Italy. 7 Università di Bologna, Dipartimento di Scienze della Terra e Geologico-ambientali. Piazza di porta San Donato 1, 40126 Bologna, Italy. The name Calabrian was introduced in the geological liter- ature by the French stratigrapher Maurice Gignoux in Historical background 1910, and later described in his important monograph (633 pages) “Les formations marines pliocènes et quaternaires According to Gignoux (1910, 1913), the Calabrian was a stage rep- de l'Italie du sud et de la Sicile” published in 1913. Detailed resenting the younger part of the Pliocene series. Of the numerous stratigraphic successions investigated, that of Santa Maria di Catan- data were provided on several sections (Santa Maria di zaro was described as follows (Gignoux, 1913): “Au Monte S. Maria, Catanzaro, Caraffa, Monasterace, Palermo) and on their le plateau culminant du point 207 est occupè par des marnes fossil content. The Calabrian Stage has commonly been blanches qui recouvrent ce banc à Cyprina islandica: ce fait est used for over fifty years as the oldest subdivision of the Qua- intéressant à noter, car il nous montre d'abord que l'apparition de ce ternary, notably in the time scales of Berggren & van Cou- banc est due à une modification de la sedimentation et de la popula- tion organique et non à une émersion; et ensuite, il nous prouve que vering (1974) and Haq & Eysinga (1987). However, after le facies argileux a persisté jusqu'après le début du Calabrien: la the GSSP for the Pliocene/Pleistocene boundary (P/P) was continuité de sédimentation qui relie le Pliocène ancien au Cal- approved by INQUA in 1982 and ratified by IUGS in 1984 abrien est donc ici bien manifeste”. at the Vrica section of Calabria, there was a decline in the This sequence was for a long time considered as the stratotype usage of the stage name, and an increasing tendency by section of the Calabrian (Banner & Blow, 1965; Selli, 1967; Bayliss, many Quaternary workers to question the boundary strato- 1969; Smith, 1969; Bandy & Wilcoxon, 1970; Selli, 1970; Berggren, 1971). The arenaceous, fossiliferous bed with the pelecypod Arctica type. This was because there was increasing evidence that it islandica (GG bed) was selected to mark the local base of the Cal- did not correspond to the beginning of the “ice age”. In abrian. doing so, they were not complying with the recommenda- Successively micropaleontological analyses (Sprovieri et al., tions presented at the 18th International Geological Con- 1973) proved that at this site the Calabrian sediments are transgres- gress (IGC) in London, 1948 (Oakley, 1950). sive on the underlying Pliocene marls and referable—as several sec- The purpose of this paper is to clarify the current def- tions described by Gignoux (1913) (Caraffa, Monasterace, Palermo)—to the Sicilian Stage of Doderlein (1872). Since the “pro- inition and usage of the Calabrian Stage, with a proper visional” Calabrian stratotype section at Santa Maria di Catanzaro historical background and the presentation of several could not be considered a valid representive of the P/P boundary, marine fossiliferous sections exposed on land that can be other options were considered. The section of Le Castella in the Cro- chronostratigraphically correlated with multiple criteria tone Basin Calabria (Emiliani et al., 1961) was accepted for defining including biostratigraphy, magnetostratigraphy, isotopic the base of the Pleistocene by some authors (Berggren & Van Cou- stratigraphy, “astrocyclostratigraphy” and occasionally vering, 1974; Haq et al., 1977, among others), with the boundary related to the so-called “marker bed” where the first occurrence (FO) tephrastratigraphy. Other sections considered and of Hyalinea baltica occurs. However, also in this case several stud- equated with those from land are from the Mediterranean ies argued that some geological-stratigraphic problems affected this deep-sea record (Tyrrhenian Sea ODP Site 653, Ionian section (e.g. anomalous concentration of biological events around Sea ODP Site 964, Levantine Sea ODP Site 967, Balearic the marker bed and a hiatus just below it). Consequently this Sea ODP 975). sequence was considered unsuitable for the definition of the P/P The Calabrian Stage has a duration of approximately boundary (Ruggieri & Sprovieri, 1977; Colalongo et al., 1980; Raffi & Rio, 1980; Rio et al., 1996a). 1.1 Ma. Its base occurs in the latest part of the Olduvai After World War II, a number of new Pleistocene stages were Event; its top is coincident with the base of the following informally proposed in Italy by Ruggieri and co-authors, as follows: Ionian Stage. After a general agreement, the definition of a) Emilian (Ruggieri & Selli, 1949) the base of the Ionian Stage (in progress) will be proposed b) Santernian (Ruggieri & Sprovieri, 1975) coincident with the Brunhes/Matuyama magnetic reversal. c) Crotonian (Ruggieri, Unti, Unti & Moroni, 1977) d) Selinuntian (Ruggieri & Sprovieri, 1979) The choice of a physical parameter as a leading criterion The last was proposed as a replacement for the Calabrian with for its identification facilitates its recognition in continen- the rank of superstage and included from bottom to top the Santern- tal successions. ian, the Emilian and the Sicilian (of Doderlein, 1872) stages. None of December 2008 409 these stages were defined following the procedures prescribed by the A large group of stratigraphers visited several outcrops of the International Commission on Stratigraphy (ICS) (Vai, 1996, 1997) Belice Valley near Selinunte, the Capo Rossello Pliocene template, (cf. Hedberg, 1976; Cowie et al., 1986; Remane et al., 1996). where the upper part of the Monte Narbone Formation extends Meanwhile one of the first projects of the International Geolog- beyond the Pliocene/Pleistocene boundary, the Monte San Nicola ical Correlation Programme (IGCP), funded by UNESCO and IUGS, section (Monte Narbone Formation), where the Gelasian Stage was was dedicated to the Neogene/Quaternary boundary: IGCP Project about to be proposed (Rio et al., 1994) in Sicily. After crossing the 41, with Nikiforova as Project leader. The project lasted from 1974 Messina Strait, several Pleistocene and Pliocene sections were vis- to 1984 and resulted in the definition of the Vrica GSSP, which was ited at Croce Valanidi, Bianco, Singa, Santa Maria di Catanzaro, Le later approved at the INQUA Congress in Moscow in 1982. Castella, San Mauro Marchesato and Vrica. The excursion ended The difficulty of correlating the terrestrial record—which is after some well-exposed sections at the core of the Apennine fore- typically discontinuous in space and time—with the marine record, where chronostratigraphical units and their defining boundaries deep in the Agri valley of Basilicata were visited (Figure 1). Here should normally be identified, was well understood by the IGCP Pro- marine sedimentation extends into the Middle Pleistocene. Outcrops ject 41 team. visited at Santa Maria d'Anglona and Montalbano Ionico looked Three options for the boundary definition were considered, all promising, and seemed more appropriate than the nearshore San coinciding with reversals of the magnetic field in order to facilitate Mauro Marchesato area. the correlation between marine and continental deposits: Moreover, the direct comparison of the type sections of the 1) the Brunhes/Matuyama reversal at approximately 0.8 Ma, Selinuntian and Calabrian showed beyond doubt that the latter stage 2) the top of Olduvai Event at approximately 1.8 Ma, is the only one with the correlation potential required of a global 3) the Gauss/Matuyama reversal at approximately 2.6 Ma. standard of reference for its continuity and the applicability for a After years of work, Selli et al. (1977) proposed the Vrica sec- multidisciplinary approach. tion of Calabria. The proposal corresponded to the second option Nothing was published on this joint excursion, which however above and was accepted by INQUA in 1982, endorsed by ICS in had a long-lasting influence on further developments as follows: 1983, adopted by the IGC in Moscow in 1984, and ratified by IUGS 1 Proposal of the Gelasian Stage as youngest division of the in 1984. Pliocene, spanning the interval from 2.6 Ma to 1.8 Ma (Gauss/ However, no specific mention of the Calabrian Stage was made Matuyama Reversal to Olduvai Event) from type section at in the official documents, and the publication of the whole data set Monte San Nicola (Rio et al., 1994). This was selected to define arising from the IGCP Project 41 took a long time (Van Couvering, the third chronostratigraphic unit for the upper part of the ed., 1996). Thus, the only papers commonly cited in the literature are Aguirre & Pasini (1985) or Bassett (1985), where the Vrica GSSP is Pliocene, as already proposed by Rio et al. (1988; 1991); presented as the Pliocene/Pleistocene boundary stratotype. This is 2 International Workshop entitled “Marine sections from the Gulf the origin of the much quoted statement that the Quaternary of Taranto (Southern Italy) as potential stratotypes for the GSSP was never defined. The hierarchical level of the Quaternary only of the Lower, Middle and Upper Pleistocene”, reported by Cita & (whether era/erathem or sub-era or period/system or whatever) was Castradori (1994; 1995) and by van Couvering (1995).