Linking the northern Alps with their foreland: The latest exhumation history resolved by low‐temperature thermochronology

Abstract

The evolution of the Central Alpine deformation front (Subalpine Molasse) and its undeformed foreland is recently debated because of their role for deciphering the late orogenic evolution of the Alps. Its latest exhumation history is poorly understood due to the lack of late Miocene to Pliocene sediments. We constrain the late Miocene to Pliocene history of this transitional zone with apatite fission track and (U‐Th)/He data. We used laser ablation inductively coupled mass spectrometry for apatite fission track dating and compare this method with previously published and unpublished external detector method fission track data. Two investigated sections across tectonic slices show that the Subalpine Molasse was tectonically active after the onset of folding of the Jura Mountains. This is much younger than hitherto assumed. Thrusting occurred at 10, 8, 6–5 Ma and potentially thereafter. This is contemporaneous with reported exhumation of the External Crystalline Massifs in the central Alps. The Jura Mountains and the Subalpine Molasse used the same detachments as the External Crystalline Massifs and are therefore kinematically coupled. Estimates on the amount of shortening and thrust displacement corroborate this idea. We argue that the tectonic signal is related to active shortening during the late stage of orogenesis.

Fault Slip and Exhumation History of the Willard Thrust Sheet, Sevier Fold‐Thrust Belt, Utah: Relations to Wedge Propagation, Hinterland Uplift, and Foreland Basin Sedimentation

“…Many prior studies have examined timing of footwall exhumation in extensional tectonic settings (e.g., Brichau et al, 2006;Singleton et al, 2014;Stockli, 2005;Stockli et al, 2001;Wells et al, 2000). While applications to reverse faults have increased (e.g., Anderson et al, 2018;Carrapa et al, 2011;Fosdick et al, 2015;Herman et al, 2010;Long et al, 2012;Parra et al, 2009;von Hagke et al, 2012), quantifying thermal effects associated with varying fault slip rates and exhumation in structurally complex areas is challenging. Estimates for the onset, duration, and rates of contractional deformation can be improved by integrating systematic sampling with sequential structural restorations and thermal modeling (e.g., Almendral et al, 2015;Lock & Willett, 2008;Mancktelow & Grasemann, 1997;McQuarrie & Ehlers, 2015;Rak et al, 2017).…”

Laterally varying structure and kinematics of the Molasse fold and thrust belt of the Central Eastern Alps: Implications for exploration

“…Strong indications exist that significant deformation in the Swiss Molasse is 10 m.y. and younger in age (Cederbom et al, 2011;von Hagke et al, 2012). For Austria and Bavaria, west of the Inn Valley, late Burdigalian deformation and shortening postdating the youngest sedimentary rocks (i.e., 9 m.y.)…”

Multi-scale imaging of a slow active fault zone: contribution for improved seismic hazard assessment in the Swiss Alpine foreland

“…This north-directed major thrust zone correlates with the young and out of sequence thrusting of the Alps (Fig. 1b) (Cederbom et al 2011;von Hagke et al 2012). The general NE-SW oriented alpine trend of folds in the Molasse basin and Jura fold-and-thrust belt shows a deviation east of the city of Fribourg to form the Fribourg structure or Fribourg zone (Fig.…”