First Finding of Upper Silurian and Lower Devonian Conodonts from the Peloritani Mountains (NE Sicily, Southern Italy)
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published online Bollettino della Società Paleontologica Italiana, 2013, i-ix. Modena First finding of upper Silurian and Lower Devonian conodonts from the Peloritani Mountains (NE Sicily, southern Italy) Rosario RODRÍGUEZ-CAÑERO, Pilar NAVAS-PAREJO, Roberta SOMMA, Agustín MARTÍN-ALGArrA & Vincenzo PErrONE R. Rodríguez-Cañero, Departamento de Estratigrafía y Paleontología, Universidad de Granada, Campus de Fuentenueva, E-18071 Granada, Spain; [email protected] P. Navas-Parejo, Departamento de Estratigrafía y Paleontología, Universidad de Granada, Campus de Fuentenueva, E-18071 Granada, Spain; [email protected] R. Somma, Dipartimento di Scienze dell’Ambiente, della Sicurezza, del Territorio, degli Alimenti e della Salute (S.A.S.T.A.S.), Università di Messina, Salita Sperone 31, Contrada Papardo, Sant’Agata di Messina, I-98166 Messina, Italy; [email protected]; corresponding author A. Martín-Algarra, Departamento de Estratigrafía y Paleontología, Universidad de Granada, Campus de Fuentenueva, E-18071 Granada, Spain; [email protected] V. Perrone, Dipartimento di Scienze della Terra, della Vita e dell’Ambiente, Campus Scientifico Località Crocicchia, I-61029 Urbino, Italy; [email protected] KEY WORDS - Conodonts, biostratigraphy, upper Silurian, Lower Devonian, Silurian/Devonian boundary, Peloritani Mountains, Sicily. ABSTRACT - In the Peloritani Mountains (NE Sicily), the Favoscuro west section (near Pizzo Leo, between Floresta and Roccella Valdemone, Messina Province) cross-cuts the Variscan basement of the Longi-Taormina Unit. This section, in the less deformed part, shows a mildly metamorphosed continuous 50-m-thick Palaeozoic succession of metamarls and calc-schists with a bed of nodular metalimestones occurring at the base and of calc-schists at the top. The basal bed yielded a conodont fauna consisting of several fragments of Pa elements of Ancoradella cf. A. ploeckensis Walliser, 1964 (Ludlow, Ancoradella ploeckensis - Polygnathoides siluricus zones). The topmost bed yielded one fragment of a Pa element of Polygnatus cf. P. kitabicus Yolkin, Weddige, Izokh & Erina, 1994 (early Emsian, Polygnathus kitabicus - Polygnathus excavatus zones). This conodont fauna, although not well preserved due to greenschist facies metamorphism and deformation, for the first time enables the recognition of upper Silurian and Lower Devonian rocks in the Peloritani Mountains. The Favoscuro west section studied herein is of important stratigraphic significance as it encompasses the Silurian/Devonian boundary. RIASSUNTO - [Primo ritrovamento di conodonti del Siluriano superiore e Devoniano Inferiore nei Monti Peloritani (Sicilia nord-orientale; Italia meridionale)] - In Sicilia, i migliori affioramenti di terreni paleozoici si ritrovano nell’Unità di Longi-Taormina dei Monti Peloritani (Sicilia nord-orientale). La sezione Favoscuro ovest (nei pressi di Pizzo Leo, tra Floresta e Roccella Valdemone; provincia di Messina) attraversa il basamento varisico dell’Unità di Longi-Taormina. In particolare, in essa, nella parte meno deformata, è rappresentata una successione continua paleozoica, potente circa 50 m, formata da metamarne e calcescisti con un livello di metacalcari nodulari e uno di calcescisti, rispettivamente alla base e al tetto della sezione. Il livello basale ha fornito una fauna a conodonti formata da diversi frammenti di elementi Pa di Ancoradella cf. A. ploeckensis Walliser, 1964 (Ludlow, biozone Ancoradella ploeckensis - Polygnathoides siluricus). Il livello superiore ha fornito un elemento Pa di Polygnatus cf. P. kitabicus Yolkin, Weddige, Izokh & Erina, 1994 (Emsiano inferiore, biozone Polygnathus kitabicus - Polygnathus excavatus). La fauna a conodonti individuata, sebbene mal preservata a causa del metamorfismo in facies scisti verdi, consente di riconoscere per la prima volta la presenza del Siluriano superiore e del Devoniano Inferiore nei Monti Peloritani. In conclusione, la sezione Favoscuro ovest risulta molto importante da un punto di vista stratigrafico poiché comprende il limite Siluriano/ Devoniano. INTRODUCTION The recognized fauna differs from that previously reported by the French authors, indicating that older In the Peloritani Mountains (Calabria-Peloritani Arc; carbonate beds, presumably late Silurian and Early Fig. 1), the only Variscan basement preserving Palaeozoic Devonian in age, are also present in this sector of the remnants of original sedimentary-volcanic protoliths and Calabria-Peloritani Arc. fossils belongs to the Longi-Taormina Unit (Bonardi et al., 1976; Somma et al., 2005b, 2012; Somma, 2006). In this unit, the main Palaeozoic fossils thus far found are GEOLOGICAL SETTING related to Cambrian-Ordovician acritarchs (Bouillin et al., 1987), Devonian dacryoconarids (Lardeux & Truillet, The crystalline basements of the Peloritani Mountains 1971), and Upper Devonian-Lower Carboniferous (Amodio-Morelli et al., 1976; Bonardi et al., 1976; conodonts (Majesté-Menjoulas et al., 1986; Bouillin et Messina et al., 2004; Somma et al., 2005a, b; Somma, al., 1987). 2006; Di Paolo et al., 2010; Aldega et al., 2011; De The aim of this paper is to illustrate the preliminary Capoa et al., 2013; Fig. 1) are formed by Palaeozoic (and results of a biostratigraphic analysis on a conodont fauna older) protoliths metamorphosed during the Variscan found in some beds of nodular metalimestones and calc- event under thermo-baric conditions ranging from schists of the Longi-Taormina Unit exposed west of Pizzo subgreenschist to granulite facies (Messina et al., 2004). Leo (between Floresta and Roccella Valdemone, in the Among the different Peloritani basements, the best- Messina Province, Fig. 1). preserved Palaeozoic succession belongs to the Longi- ISSN 0375-7633 doi:10.4435/BSPI.2013.15 ii Bollettino della Società Paleontologica Italiana, 2013 Fig. 1 - Geological sketch map of the Peloritani Mountains with the study area (Pizzo Leo) and main Palaeozoic fossiliferous sites (modified after Somma, 2006; Aldega et al., 2011; Somma et al., 2013). The Calabria-Peloritani Arc (CPA) is represented in the insert at bottom-right. Key: 1: Upper Miocene to Holocene covers. 2: Etna volcanics. 3: Calcareniti di Floresta (Serravallian-Langhian), “Antisicilide Variegated Clays” (Upper Cretaceous-Palaeogene), and Stilo-Capo d’Orlando Fm (Burdigalian). 4: Aspromonte Unit (Variscan medium-high grade metamorphics with Pre-Variscan granulitic relics, intruded by Late-Variscan plutonic rocks and with local medium- to low-grade Alpine metamorphic overprint). 5: Mela Unit (Variscan medium-grade metamorphics with Eo-Variscan eclogitic relics). 6: Mandanici-Piraino Unit (Variscan low- to medium-grade basement and Mesozoic cover affected by low-grade Alpine metamorphism). 7: Alì-Montagnareale Unit (Permian?-Mesozoic succession affected by Alpine very low-grade metamorphism). 8: Fondachelli Unit (Variscan low-grade basement and Mesozoic cover). 9: Longi-Taormina Unit (Variscan very low- to low-grade basement and Mesozoic-Cenozoic sedimentary cover). 10: Maghrebian Flysch Basin Units (Upper Jurassic-lower Miocene). 11: Stratigraphic contact. 12: Tectonic contact. 13: Peloritani basal thrust (Taormina Line; triangle on the hanging wall). 14: Conodonts (Majesté-Menjoulas et al., 1986). 15: Dacryoconarids (Pizzo Leo: Lardeux & Truillet, 1971; Caprileone: Acquafredda et al., 1991). 16: Acritarchs (Majesté-Menjoulas et al., 1986; Bouillin et al., 1987). Taormina Unit (Bonardi et al., 1976), as mildly deformed and metamorphosed under subgreenschist to greenschist (chlorite zone) facies conditions (T ~ 350°C and P < 0.2 GPa; Atzori et al., 1984). Notwithstanding Variscan metamorphism and deformation, responsible for two foliations crossing the original bedding at different angles (Sv1 and Sv2; Somma, 2006), pre-Permian siliciclastics and minor carbonates crossed by volcanic rocks (Ferla & Azzaro, 1978; Cirrincione et al., 2005) are still clearly observable (Somma et al., 2012). In the Longi-Taormina Unit, the main outcrops of Palaeozoic rocks are exposed in the eastern (Taormina area), central (Pizzo Leo area), and western (Caprileone area) sector of the Taormina Line (sensu Bonardi & Giunta, 1982; Fig. 1). Particularly, in the central sector of the Taormina Line (Pizzo Leo area), one of the best preserved Palaeozoic successions crops out. The geological survey made in this area (Fig. 2) indicates that the Variscan basement, up to 300 m thick, consists mainly of a Palaeozoic siliciclastic and carbonate monoclinal succession, primarily N-dipping. The lower part of the succession is formed by siliciclastic beds, composed Fig. 2 - Geological sketch map of the Pizzo Leo area with location of the Favoscuro west section and the investigated conodont sites. R. Rodríguez-Cañero et alii - Silurian and Devonian conodonts from the Peloritani Mountains iii Fig. 3 - Favoscuro west section: section A-B (see location of the section in Fig. 2). The conodonts in the southernmost carbonate block are Emsian in age (Somma et al., 2012). mainly of metapelites hosting several-metre-thick lenses limestone in the section A-B (Fig. 3). Also, eight samples of alkaline metavolcanic rocks (in the lower part) and (MAJ-6, MAJ-7, MAJ-8, MAJ-9, MAJ-10, MAJ-11, decimetre-thick lenses of nodular metalimestones (at MAJ-12, and MAJ-13) were collected from the metamarls the top). The upper part of the succession is made up and interbeds of limestone in the intermediate part of mainly of metacarbonates. These are represented, at the the Favoscuro west section (Fig. 3). In total, more than base, by thick-bedded