Chronology of the transition from a spreading ridge to an accretional seamount in the Marsili backarc basin (Tyrrhenian Sea)

Abstract

Inversion of new high‐resolution magnetic data from the Marsili seamount and the surrounding basin in the Tyrrhenian Sea reveals NNE–SSW magnetization stripes ranging from the Matuyama chron to the Brunhes chron, including the short positive Jaramillo subchron. The detailed magnetic chronology shows that from the late Matuyama (1.77 Ma), the average half spreading rate was about 1.5 cm yr−1, with a slight decrease between the Jaramillo and the Brunhes events, when the growth of the volcanic edifice overcame lateral spreading. Analysis of spreading rate and volume of erupted lava indicates that at the beginning of the Jaramillo subchron (1.07 Ma), the Marsili basin evolved from pure horizontal spreading to a superinflated seamount as a consequence of tearing of the Ionian slab. Our data give us a snapshot of the geodynamic transition from an active backarc spreading phase to the vertical accretion of the seafloor because of a radical change in the subduction dynamics.

The Marsili Volcanic Seamount (Southern Tyrrhenian Sea): A Potential Offshore Geothermal Resource

“…Figure 4 shows the total field magnetic anomaly map, reduced to the magnetic pole, recorded above Marsili seamount. In agreement with literature data [35,37,38], positive magnetic anomaly maxima are located along the central sectors of the volcanic structure. At northern and southern tips the highest positive anomalies of Marsili are present, with maximum values around 1500 nT; in the central and highest portion of volcano and in the middle of these two former anomalies, the values are around 0 nT, reaching a minimum of −100 nT.…”

“…Marsili seamount is a recent volcanic structure (1-0.1 Ma), mainly composed of basalts and, to a lesser extent, andesites and trachy-andesites with calc-alkaline affinity [32][33][34]. This structure has been interpreted as an inflated, small-scale spreading centre, since bio-and magneto-stratigraphic data show features comparable to those typical of mid-ocean ridges [35][36][37][38].…”

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

“…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 of about 2100 km 2 and rises from about 3200 m to 508 m b.s.l.…”

“…The geodynamic significance of MS is still debated: Marani and Trua (2002) propose that MS represents the super-inflated ridge of the Marsili oceanic basin, whereas Ventura et al (2013) suggest that (a) MS is a volcanic arc edifice formed within the now inactive, relict Marsili back-arc, and (b) its growth is due to passive magma ascent along pre-existing fractures inherited by the early spreading activity. In fact, the spreading rate in the Southern Tyrrhenian Sea back-arc abruptly decreased from 2.8-3.1 mm/a to less than 1.8 mm/a in the last 0.78-1 Ma (Cocchi et al, 2009). …”

Observing Volcanoes from the Seafloor in the Central Mediterranean Area

“…During the Plio-Pleistocene, the extension changed from E-W to SE-NW [4], forming the Marsili basin that includes the Marsili Seamount (MS; Figure 1), the largest European underwater volcano. MS is associated with the north-westward subduction of the Ionian lithosphere below the Calabrian Arc [5], and its formation is dated between 1.7 and 0.1-0.2 Ma [6,7]. In this region, the coexistence of compression due to slab Figure 1.…”