New results of ⁴⁰Ar/³⁹Ar dating constrain the timing of transition from fissure‐type to central volcanism at Mount Etna (Italy)

Abstract

Recent geological studies performed at Etna allow reassessing the stratigraphic frame of the volcano where distinct evolutionary phases are defined. This stratigraphic reconstruction was chronologically constrained on the basis of a limited number of U–Th and K–Ar age determinations whose uncertainty margins are sometimes too wide. For this reason, we successfully adopted at Etna the 40Ar/39Ar technique that allowed obtaining more precise age determinations. The incremental heating technique also gives information on sample homogeneity, and potential problems of trapped argon. Five samples were collected from stratigraphically well‐controlled volcanic units in order to chronologically define the transition between the fissure‐type volcanism of the Timpe phase to the central volcanism of the Valle del Bove Centers. Isotopic ages with an uncertainty margin of 2–4% have been obtained emphasizing that this transition occurred (130–126 ka) without significant temporal hiatus.

Geological evolution of Mount Etna volcano (Italy) from earliest products until the first central volcanism (between 500 and 100 ka ago) inferred from geochronological and stratigraphic data

“…All experiments yielded excellent plateaus in agreement with the commonly accepted standards (e.g. Dunai and Wijbrans 2000;De Beni et al 2005).…”

“…This behaviour (Geol Rundsch) suggests that the K-rich components become depleted and Ca-rich phases (andesine and labradorite) dominate the final steps of the experiments because their crystal sizes are generally larger and likely to melt later then K-rich components. K-rich phases are microlite of albite and anorthoclase which are spread in the groundmass as the result of the late (post-eruption) crystallization of the volcanic glass during the cooling of lava flow below the solidus temperature (De Beni et al 2005). The isochron age is in disagreement with the weighted plateau age probably due to the presence of extraneous argon.…”

“…D'Oro, has an isotopic age constrained between 145.8 ± 7.0 ka (TC sample) and 121.2 ± 7.5 ka (VS sample). During this time span a thin lava flow cropping out on the northern Catania periphery was emplaced at about 134.2 ± 3.3 ka (De Beni et al 2005).…”

“…The lava flows forming the base of the Moscarello Timpa succession have an 40 Ar/ 39 Ar age of 129.9 ± 2.4 ka (De Beni et al 2005) that is coeval with the age of Calanna volcanics. In particular, De Beni et al (2005) evidence that the Moscarello lava succession were emplaced in a short Fig. 8 Extension of the tholeiitic lava plateau inferred by subsurface and geological data and location of the paleo-shoreline of about 300 ka ago.…”

“…Currently, De Beni et al (2005) successfully applied the 40 Ar/ 39 Ar technique on Etna volcanics in order to improve the reconstruction of its geochronological evolution defining the temporal hiatus and the significance of one of the main unconformities of the volcanic succession.…”