The proximal marine record of the Marsili Seamount in the last 7 ka (Southern Tyrrhenian Sea, Italy): Implications for the active processes in the Tyrrhenian Sea back-arc S. Tamburrino a,c , M. Vallefuoco a , G. Ventura a,b, ⁎, D.D. Insinga a , M. Sprovieri c , M. Tiepolo d , S. Passaro a a Istituto per l'Ambiente Marino Costiero di Napoli, Consiglio Nazionale delle Ricerche, Napoli, Italy b Istituto Nazionale Geofisica e Vulcanologia, Roma, Italy c Istituto per l'Ambiente Marino Costiero U.O.S. di Capo Granitola, Consiglio Nazionale delle Ricerche, Campobello di Mazara, Italy d Dipartimento di Scienze della Terra “A. Desio”, Università degli Studi di Milano, Milano, Italy abstract article info Article history: Received 25 March 2015 Received in revised form 3 July 2015 Accepted 14 July 2015 Available online 18 July 2015 Keywords: Holocene tephra Back-arc spreading Extensional arc Submarine active volcanism Plumbing system Marsili Seamount Etna volcano The volcanism of back-arc basins resembles that of oceanic spreading centers, rifts, and, in vanishing stages, ex- tensional arcs, depending on the amount and rate of the dynamic processes associated to the subduction. Marsili Seamount (MS) represents the axial ridge of the Southern Tyrrhenian Sea back-arc basin, which is connected to the slab roll-backing processes affecting the Calabrian Arc (Italy). The Southern Tyrrhenian Sea back-arc is char- acterized by a significant decline in the spreading rate with time (2.8–3.1 mm/a to less than 1.8 mm/a in the last 0.78–1 Ma). MS develops between about 1 Ma and 3 ka and mainly consists of lava flows erupted from central and fissural vents. The MS products belong to the calcalkaline association and range in composition from basalts to trachytes. We present new stratigraphic, geochronological, and geochemical data (glass shards and minerals) of tephra from a 2.35 m long gravity core (Marsili1 core) recovered on MS at 943 m b.s.l. We recognize five tephras [M1 (top of the core) to M5 (bottom)] represented by poorly to highly vesiculated ashes. The lowermost tephra M5 emplaced between ca. 7 and 26 ka B.P.; it represents the less evolved distal counterpart of the Unit D related to the Biancavilla–Montalto products of Mount Etna (Sicily). The M1 to M4 tephras emplaced between 2.1 and 7.2 ka B.P. and are related to strombolian-like submarine eruptions of NNE–SSW aligned MS vents. The com- position of the M1–M4 glasses ranges from basaltic trachyandesites to andesites and trachytes. The M1 to M4 magmas mainly originated by crystal fractionation from a heterogeneous mantle source with varying LILE enrichments by subduction-related fluids. The degree of evolution of the MS magmas increases with decreasing time. The formation of vertically stacked magma storage zones at the crust/mantle interface and within MS is related to the vanishing Southern Tyrrhenian Sea opening, which implies the rapid (b 1 Ma) evolution from a slow spreading back-arc setting to an arc system. © 2015 Elsevier B.V. All rights reserved. 1. Introduction The volcanism at plate margins is controlled by the strain rate and by the conditions of magma storage and ascent, which, in turn, depend on the temperature field, the rheology and thickness of the lithosphere. Contractional arcs and immature rifts are characterized by null to slow opening rates, polygenic volcanism, and andesitic to silicic magmatism (Acocella, 2014), whereas extensional arcs, mature rifts and oceanic spreading centers have monogenetic, mainly basaltic volcanism and higher values of the opening and magma production rates (Crisp, 1984; Abelson and Agnon, 2001). The above described geodynamic settings represents a ‘continuum’ among different end member scenarios. As an example, back-arcs are associated to subduction zones and their magmatic/volcanic setting spans from that of contractional arc/immature rifts (e.g., the Puna back-arc in Argentina; Risse et al., 2013) to mature rifts and oceanic spreading centers (e.g., Eastern Lau Spreading Center, Tonga; Martinez et al., 2006). Also, back-arc spreading centers are controlled by the spatial proximity to the subduction zones, the inclination and velocity of the slab, the occurrence of possible roll- back processes, and the temperature and composition of the mantle wedge. Because of this complexity, the study of the volcanism in back- arc spreading centers is of primary importance to analyze the eruptive style and geometry of the plumbing systems, whose time variations may be signs of important geodynamic changes. Marsili Seamount (MS, about 1.07 Ma to 3 ka) is a NNE-SSW elongat- ed volcanic complex located in the Southern Tyrrhenian Sea oceanic basin (Fig. 1a, b; Selli et al., 1977; Marani and Trua, 2002; Cocchi et al., 2009; Ventura et al., 2013; Iezzi et al., 2014). MS, which covers an area Global and Planetary Change 133 (2015) 2–16 ⁎ Corresponding author at: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Roma, Italy. E-mail address: guido.ventura@ingv.it (G. Ventura). http://dx.doi.org/10.1016/j.gloplacha.2015.07.005 0921-8181/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Global and Planetary Change journal homepage: www.elsevier.com/locate/gloplacha