Reconstructing the Evolution of Foreland Fold‐And‐Thrust Belts Using U‐Pb Calcite Dating: An Integrated Case‐Study From the Easternmost Jura Mountains (Switzerland)

• Published in: Tectonics (Washington, D.C.) Vol. 43; no. 5
• Main Authors: Madritsch, Herfried, Looser, Nathan, Schneeberger, Raphael, Wohlwend, Stephan, Guillong, Marcel, Malz, Alexander
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-05-2024
• Subjects: Boreholes; Calcite; Carbonates; Cenozoic; Dating techniques; Deformation; deformation style; Evolution; foreland thrust‐belts; Geochronology; Jura Mountains; Mesozoic; Mountains; Paleozoic; Seismic data; Seismological data; shortening rates; U‐Pb carbonate dating; Switzerland; Jura Mountains
• ISSN: 0278-7407; 1944-9194
• DOI: 10.1029/2023TC008181

This case‐study from the Jura Mountains in the foreland of the European Alps demonstrates how the coupling of subsurface analysis and U‐Pb carbonate dating can provide absolute timing constraints and shortening rate estimates of fold‐and‐thrust belts. It is confirmed that the initial Late Cenozoic foreland deformation driving the formation of the easternmost Jura Mountains in Switzerland was predominately thin‐skinned with contractional deformation largely restricted to the Mesozoic succession above a sub‐horizontal basal décollement. Thereby, the localization and structural style of related deformation structures was strongly guided by the characteristics of underlying Late Paleozoic half grabens. The main thin‐skinned thrust front formed at ∼12 Ma, followed by further deformation in the hinterland and locally continued foreland‐directed thrust propagation. The major deformation zones exposed at surface were established at ∼8 Ma but shortening continued until at least ∼4 Ma. Thick‐skinned contraction associated with the inversion of basement structures only played a subordinate role during the latest deformation phase after 8 Ma. Based on cumulative shortening values derived from balanced cross sections, our U‐Pb ages of syn‐tectonic calcite slickenfibres allow to estimate thin‐skinned deformation rates for the easternmost Jura Mountains between ∼0.9 and ∼0.1 mm/year, decreasing toward the eastern tip of the arcuate belt. Moreover, deformation rates seemingly decreased over time with rates of initial thin‐skinned thrusting being significantly higher than the later deformation north of the main thrust front. These new findings from a classical foreland setting highlight the potential of integrating U‐Pb dating in regional fold‐and‐thrust belt investigations elsewhere.
Plain Language Summary
We present a case‐study combining the geological‐geophysical analysis of the subsurface with novel geochronological dating techniques to better constrain the evolution of the easternmost Jura Mountain in northern Switzerland. Seismic data and boreholes support the characterization of the deformation style, while dating of calcite percipitations on fractures observed in the field allow to establish deformation timing and rates.
Key Points
Alpine deformation in the easternmost Jura Mountains is predominantely thin‐skinned strongly guided by basement structures
U‐Pb calcite dating suggests thin‐skinned deformation rates between 0.9 and 0.1 mm/year decreasing toward the tip of the belt
Deformation rates appear to have decreased over time and are lower north of the main thrust front