Geochemical evidence for diachronous uplift and synchronous collapse of the high elevation Variscan hinterland

Competing end-member models for the late Paleozoic Variscan orogeny (ca. 360-290 Ma) alternatively suggest moderate 2-3 km elevations underlain by relatively thin crust (<50 km) or a thick crust (>55 km) that supported high 4-5 km elevations. We tested these models and quantified the crustal thickness and elevation evolution of the Variscan orogeny using igneous trace element geochemical proxies. The data suggest that thick crust (55-70 km) capable of supporting 3-5 km elevations developed diachronously from east to west between ca. 350 and 315 Ma. Crustal thinning occurred from ca. 315 Ma to 290 Ma across the orogen. Crustal thickness and elevation changes at ca. 340-325 Ma and 315-290 Ma correspond with increases in silicate weathering recorded by Sr and Li isotopes, consistent with models in which silicate weathering of the Variscan orogen contributed to global cooling associated with the late Paleozoic ice age.