Abstract

Apatite fission-track ages and track-length measurements are presented from 22 samples from the Glarus Alps, eastern Switzerland, where maximum temperatures of 100 to 350 °C along an Alpine thrust plane were reached during late Tertiary metamorphism. With the exception of the northernmost sample, apatite ages are fully reset and range between 5 and 12 Ma. Apatite fission track data along a vertical profile and a horizontal profile indicate that isothermal planes were oriented parallel to the Glarus thrust plane and that the thrust plane cooled below a mean apatite fission track closure temperature of 110 °C at 9 Ma.

The metamorphic pattern and fission-track data indicate a south-dipping thrust plane during the times of peak metamorphic conditions, postmetamorphic thrusting over a distance of ∼ 10 km, and gradational exhumation of the plane to a horizontal position at ca. 9 Ma. Ongoing rotation of the plane is reflected by the present dip of about 7°NNW.

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