episodic onset of explosive and silicic-dominated volcanism in a continental rift; insights from the Permian Oslo Rift, Norway

The nature of rifting episodes and their associated volcanism mark key stratigraphic events in the evolution of volcano-sedimentary basins. Following the final assemblage of Pangea, the European region was subject to rifting and magmatismduring crustal re-equilibration throughout the Permian. The aborted, partially eroded Oslo Rift is an excellent archive of thisPermian magmatism, but the late-stage volcanological evolution is poorly understood. We present the first detailed documen-tation of a succession covering this period, with mafic lavas and volcaniclastic (tuff breccia) deposits, trachy-andesitic tuffs,and rheomorphic to moderately welded ignimbrites. Contrary to previous ideas, we show evidence suggesting the develop-ment of Strombolian-type scoria-cones, silicic fissure-fed eruptions, and major periods of rift-wide volcanic quiescence. Ourobservations highlight episodic silicic volcanism characterised by rapid evolution from high-grade ignimbrites to moderatelyand poorly welded ignimbrites. We infer rapid emptying of large, shallow silicic reservoirs and frequent source switching isresponsible for the observed characteristics.