Increase in late Neogene denudation of the European Alps confirmed by analysis of a fission-track thermochronology database

Abstract

International audienceA sharp increase in deposited sediment volume since Pliocene times has been observed worldwide and in particular around the European Alps. This phenomenon has been linked to a rise in denudation rates controlled by an increase of either climatic or tectonic forcing. Observation of in-situ cooling histories for orogens is critical to assess the reality of the inferred increase in denudation rates, and to determine whether this phenomenon is widespread or localized at active tectonic structures. We exploit the unique density of fission-track ages in the Western European Alps to reconstruct cooling isoage surfaces and to estimate exhumation rates on the orogen scale between 13.5 and 2.5 Ma. Our novel technique is based on the association of isoage contours with age–elevation relationships. It uses map-view interpolation, enabling a spatio-temporal analysis of exhumation rates over the entire Western Alps. The resulting exhumation histories reconstructed for eight areas of the Western Alps display strong similarities in timing and rates with orogen-wide average denudation rates inferred from sediment volumes. This consistency validates the use of both techniques for the study of an orogen characterized by strong relief and high recent exhumation rates. We conclude that exhumation rates in the Western Alps have increased more than twofold since Late Miocene times. This increase may have been locally modulated by the distinct response of different tectonic units

Erosion-driven uplift of the modern Central Alps

“…The finite deformation and exhumation over a succession of many glacial-interglacial periods is insensitive to this process . The rate of exhumation rates over million of years (fission track ages, Vernon et al, 2008) is of the same order of magnitude as those of the Late Holocene (~1 mm/yr or 1 km/Ma) and the thermal history reflects the average of short term denudation variations.…”

Thick-Skinned and Thin-Skinned Tectonics: A Global Perspective

“…The uplift maxima in eastern and western Switzerland are higher (around 1.5 mm/a). It is interesting to note that Zircon and Apatite fission track data (see compilation by [143]) show a similar regional distribution of maximum exhumation rates suggesting that the present day pattern has been active at least since 5 Ma [133].…”

Geochronological evidence for continuous exhumation through the ductile‐brittle transition along a crustal‐scale low‐angle normal fault: Simplon Fault Zone, central Alps

“…Instead there is a progressive and gradual decrease in age to the north across the SFZ (from 12 Ma to 5.4 Ma with zircon and from 5.8 Ma to 2.2 Ma with apatite). In the northwestern part, across the Rhone Valley (Figure 1a), a clear jump in cooling ages is shown by the fission track ages [Soom, 1990;Seward and Mancktelow, 1994;Vernon et al, 2008]. Nevertheless, almost no radiometric ages were previously available between the Rhone Valley and the central region of the SFZ and a continuation of the thermochronological jump into the Rhone Valley was not well established.…”