Application of actualistic models to unravel primary volcanic control on sedimentation (Taveyanne Sandstones, Oligocene Northalpine Foreland Basin)

Abstract

This work is focused on the Taveyanne Sandstones (Grés de Taveyanne), an Oligocene volcaniclastic turbidite sequence cropping out in the Northern Alpine Molassa between SE France and Central Switzerland, with the aim to investigate the temporal relationship between volcanic activity and sediment supply. Detailed stratigraphic, sedimentological, and petrographic (XRD analyses on mudstones and point counts on sandstones) studies conducted on three sections (Col de l'Oulette and Flaine in SE France, Taveyanne in SW Switzerland) allow a discrimination of three main facies, among which only one is extremely enriched in volcaniclastic detritus and characterized by features similar to those of disaggregated pyroclastic density current deposits. The other two facies are characterized by variable to no volcanic detritus but supplied by crystalline and sedimentary detritus. Such sediment trends are similar to those of modern, volcanically controlled source-to-sink systems. This allows a reinterpretation of the Taveyanne Sandstones as a syn-volcanic turbidite system, episodically supplied by large amounts of volcanic detritus, which periodically modified the drainage paths. Moreover, the well-known temporal and spatial persistence of such modifications in modern settings leads to conciliate the syn-volcanic supply with the location of the volcanic centers in the internal part of the Alps, without invoking particular climatic and tectonic conditions controlling foreland sedimentation.