Cyclic volcanic stratigraphy in a late ordovician marginal basin, West Norwegian Caledonides

Abstract

Th e well-preserved extrusive sequence of the Solund-Stavfjord Ophiolite Complex (SSOC) in the West Norwegian Caledonides enables reconstruction of the uppermost oceanic crust that developed in a marginal basin. Basaltic sheet flows, pillow lavas and volcanic breccias are the main components of the extrusive sequence and show stratigraphic and structural evidence for a cyclic development. The first stage in a volcanic cycle is characterized by high extrusion rates yielding sheet flows, commonly with the thickest flow units at the base. Sequences of sheet flows can be correlated laterally for at least 6.5 km. Pillow lavas succeed the sheet flows later in a volcanic cycle with progressively smaller pillows forming at decreasing extrusion rates. Volcanic breccias occur towards the end of a volcanic cycle, but may also occur at lower stratigraphic levels. They are made generally of pillow breccias and hyaloclastites. The extrusive sequence of the SSOC oceanic crust was constructed through seven volcanic cycles that resulted in stratigraphic units with thicknesses ranging from 40 to 225 m. This architecture is comparable to sequences in in situ oceanic crust developed along slow-to intermediate-spreading ridges.

Bio-signatures in metabasaltic glass of a Caledonian ophiolite, West Norway

“…Samples were collected from the least deformed part of the Late Ordovician (443 ± 3 Ma) Solund-Stavfjord Ophiolite Complex in the western Norwegian Caledonides (see Furnes, Hellevang & Dilek, 2001, and references therein). The Solund-Stavfjord Ophiolite Complex displays a well-preserved volcanic sequence of basaltic pillow lavas, sheet flows and volcanic breccias, a sheeted dyke complex, and high-level gabbro.…”

Structure, geochemistry, and tectonic evolution of trench-distal backarc oceanic crust in the western Norwegian Caledonides, Solund-Stavfjord ophiolite (Norway)

“…The extrusive sequence ranges in thickness from ~470 m to 800 m. Pillow lava sequences locally show development of megacycles characterized by extrusion of large (mega) pillows at the base, overlain by lavas with decreasing pillow sizes that are in turn capped on top by pillow breccias or hyaloclastites. We interpret each of these pillow lava units as the product of a distinct eruptive event (Furnes et al, 2001(Furnes et al, , 2003. Massive lavas occur mainly in Stavestranda and Alden (Fig.…”

Hydrothermal alteration and tectonic evolution of an intermediate‐ to fast‐spreading back‐arc oceanic crust: Late Ordovician Solund‐Stavfjord ophiolite, western Norway

“…The Late Ordovician Solund‐Stavfjord ophiolite complex (SSOC) in the western Norwegian Caledonides represents a fragment of an intermediate‐spreading ancient oceanic crust developed in an Early Paleozoic marginal basin (Dilek et al . 1995, 1997; Fonneland 1997; Furnes et al . 1998, 2000, 2001, 2003a,b; Ryttvad et al .…”