Facies (2010) 56:399-432 DO1 10.1007/s10347-010-0212-6 Fish otoliths from the pre-evaporitic Early Messinian of northern Italy: their stratigraphic and palaeobiogeographic significance Angela Girone a Dirk Nolf * Oreste Cavallo Received: 13 August 2009 / Accepted: 4 January 2010 / Published online: 9 February 2010 O Springer-Verlag 2010 Abstract The study of otolith assemblages from the pre- affinity of the fossil assemblage with the present-day Medi- evaporitic Messinian deposits allows the reconstruction of a terranean neritic fauna, which was already recorded at the fauna of 79 taxa of which 35 could be identified at the spe- genus level for the Rupelian fauna, persists during the Neo- cific level. Three of these are new: Diaphus rubus, Myctop- gene and continues until the Pleistocene. hum coppa, and Uranoscopus ciabatta. The assemblages reflect mainly a neritic environment influenced by the oce- Kepords Fishes . Teleostei . Otoliths . Messinian anic realm. Analysis of the global present-day geographic Appearance . Extinction distribution of 42 of the recognised Messinian genera indi- cates that 88% of these are still living in the Mediterranean, 98% in the Atlantic and 78% in the Indo-Pacific realm. Introduction These results are in good agreement with the evolutionary trends documented for the Oligocene and Miocene teleost During the Late Miocene (Tortonian and Messinian), the fauna, specifically an increase in percentage of genera Tethyan Ocean was ultimately closed as result of synoro- inhabiting the modern Mediterranean, a very high percent- genic collisional tectonism, and its Mesozoic and Cenozoic age of Atlantic and Indo-Pacific genera, and a slight fall of sedimentary sequences were deformed and uplifted along the importance of present-day Indo-Pacific genera from the the emerging Alpine-Himalayan orogenic system. Deep- Rupelian up to the Late Miocene. Analysing the composi- water, open-sea environments persisted through the Late tion of the Early Messinian fauna at the level of nominal Miocene in scattered areas in the proto-Mediterranean species indicates that about 53% of the species represented Basin. During the Messinian, the Mediterranean Basin was in the assemblages are still living in the Recent Mediterra- affected by palaeoceanographic changes marked in the sedi- nean, and that a significant number of these were already mentary record by both cyclic variations forced by astro- present in the Tortonian. It is interesting that these species nomical factors and periodic or abrupt changes related to are mainly neritic. This seems to confirm that the close water mass exchanges with the Atlantic Ocean driven by tectonicleustatic controls. The main change corresponds to the Salinity Crisis, which was responsible for the deposition A. Girone (El) of widespread saline deposits over the whole palaeo- Facold di Scienze, Dipartimento di Geologia e Geofisica, Mediterranean area (Hsii et al. 1973; Cita et al. 1978; Campus Universitario, Via E. Orabona 4,70125 Bari, Italy Rouchy 1982) (Fig. 1). An age between 6 and 5.7 Ma is e-mail: [email protected] now commonly accepted for the onset of the evaporite D. Nolf deposition in several basins (Vai et al. 1993; Gauthier et al. Institut royal des Sciences naturelles de Belgique, 1994; Hilgen et al. 1995; Sprovieri et al. 1996). Evidence 29, Rue Vautier, 1000 Brussels, Belgium exists that although the end of the Messinian Salinity Crisis 0. Cavallo appears to have been rather abrupt, the onset was gradual. Civico Museo Archeologico e di Scienze Naturali, Throughout the Mediterranean, the pre-evaporite sediments Via Vitt. Ernanuele 19, 12051 Alba, Italy display changing lithologies during the Early Messinian, a Springer 400 Facies (2010) 56:399-432 Fig. 1 Location of the studied area (from Cita and Corselli 1993; modified) from predoxninantly marl/sapropel sequences to either diat- The Early Messinian otolith associations are compared omites (e.g. Sicily, Gavdos, northeastern Morocco, Algeria) with those from the Tortonian and Pliocene Mediterranean or euxinic clays (e.g. northern Italy, Tyrrhenian Sea, east- deposits, in order to evaluate the evolution of the fish fauna ern Mediterranean). Palaeoenvironmental changes related at the Tortonian-Early Messinian interval and to focus on to these lithological transitions are documented by faunal the principal changes in the composition and diversity of (e.g. Cita 1976; Van der Zwaan 1982; Benson et al. 1991; the teleost fauna before and after the Messinian Salinity Sierro et al. 1993; Hodell et al. 1994) and geochemical (sta- Crisis in the Mediterranean realm. ble isotope) parameters (e.g. Vergnaud-Grazzini 1983; Vergnaud-Grazzini et al. 1977; McKenzie et al. 1979; Van der Zwaan and Gudjonsson 1986; Hodell et al. 1994; Geoloaeal context Kastens 1992). Micropalaeontological studies indicate from the Late Tortonian through Early Messinian, the beginning The studied sections are located in the Tertiary Piedmont of deterioration of the Mediterranean water mass circulation, Basin (Verduno and Moncucco sections) and inside the probably related to a warming climate phase (characterised thrust belt of the Rornagna Apennines (Brisighella sec- by stratification in the water column) and to the closure of tions). the southern Rifian Corridor representing the corridor for The Tertiary Piedmont Basin is composed of different the idow of Atlantic deep-water during the Tortonian tectono-sedimentary domains: the Torino fill and Monfer- (Benson et al. 1991) (Fig. 1). rat0 (Moncucco section) to the north and the Langhe Basin The present paper provides an otolith-based reconstruc- (Verduno sections), the Alto Monferrato and the Borbera tion of the Early Messinian faunas in the Mediterranean Grue sector to the south. These domains show partially realm, based on assemblages from several sections in the independent tectono-sedimentary evolution and are filled Piedmont and Romagna basins (northern Italy) (Fig. 1). by Eocene to Neogene sediments. The Piedmont Messinian Until now, knowledge of the Messinian Mediterranean tele- succession outcrops widely in the Langhe area where ost fauna was based mainly on skeletal material. A synthe- Sturani (1973, 1978) described a three-fold succession very sis of the data is given by Gaudant (2002). Otolith-based comparable to coeval Sicilian deposits. However, the Mon- reconstructions of the Miocene fish fauna in the Mediterra- ferrato Messinian outcrops are rather scarce and are repre- nean realm deal mainly with Lower Miocene and Tortonian sented mainly by evaporitic and post-evaporitic deposits. (Upper Miocene) associations from deep-sea sediments in The classical Piedmont Messinian succession is character- northern Italy (Robba 1970; Nolf and Steurbaut 1983; Nolf ised, from bottom to top, by: (1) lower "pre-evaporitic" and Brzobohaty 2004). Additional data are furnished by deep-water marine sediments, coeval to the Sicilian Tripoli neritic assemblages from Lower Miocene deposits of Formation, representing normal and euxinic facies (Shuani France (Nolf and Cappetta 1980; Reichenbacher and 1978) and lithologically referable to the Sant9AgataFossili Cappetta 1999) and by Middle Miocene (Langhian) neritic Marls (Tortonian-Early Messinian in age); (2) intermediate associations from Spain Woedemakers and Batllori 2005). "evaporitic" shallow-water deposits, referred to the Q springer Facies (2010) 56:399-432 Gessoso-solfifera Formation, described by Vai and Ricci The section offers a complete overview of Messinian sedi- Lucchi (1977) in the Romagna Basin (see below), starting ments, starting in the top of the pre-evaporitic Messinian with calcareous levels indicated as "Calcare di Base" and clays, which are succeeded by huge massive gypsum including gypsum deposits (Sturani 1978); (3) upper "post- deposits that are overlain by Lago Mare sediments. Finally, evaporitic" brackish deposits of the "Strati a Congerie" cor- the Messinian is overlain with marine Zanclean clays. The related to the Mediterranean Lago-Mare facies (Cita et al. interesting part for otolith studies is the top of the pre-evap- 1978). The succession is overlain with open-marine Early oritic clays, just below the massive gypsum beds and Pliocene clays. underlying "Calcare di Base". This part of the section was In the Brisighella area, the four main formations build- measured and additionally sampled in 2007 (Fig. 2). AU ing the Romagna Apennines are exposed: (1) the upper part samples were very rich in otoliths of small mesopelagic of the Marnoso-arenacea Formation (Tortonian-Early Mes- fishes, mainly Diaphus. The overall weight of the samples sinian), (2) the Gessoso-solfifera Formation (Messinian), is f 20 kg for samples a, c, d and e, and about 100 kg for (3) the Colombacci Formation (Late Messinian) and (4) the sample b. lower part of the Argille Azzurre Formation, whose base The foraminifera of sample b were analysed by Erica belongs to the MPLl Zone (Lower Pliocene) (Vai 1989). Bicchi and indicated the sediment as Messinian N17, 610- As defined by Vai (1989), the Tripoli and Marne tripola- borotalia conomiozea Zone, Globigerina multiloba Subz- cee units of the older literature correspond to part of mem- one of D' Onofi-io et al. (1975). bers 4 and 5 (upper part) of the Marnoso-arenacea Moncucco, gypsum quarry: Formation. Part of these deposits, characterised by shaly, organic-matter-rich layers, are also named "pre-evaporitic Carta d'Italia IGM 1125,000, sheet Buttigliera d7Asti(56 II euxinic shales", and Early Messinian in age. The Gessoso-