Date/heure
Date(s) - 17 janvier 2023
13 h 00 min - 14 h 00 min
Catégories
Reconstructing topography of the Equatorial Variscan belt
Résumé: The first stable isotope paleoaltimetry estimates have been recently acquired for the internal zones of the eroded Variscan Belt of Western Europe (Limousin region) based on the hydrogen isotope ratios (δD) of muscovite from syntectonic leucogranites that have been emplaced at ~315 Ma. The results point to locally sourced waters that originated at high elevations (3.4 ± 0.7 km) in an area with strong relief, most likely forming a Late Carboniferous topographic high within the Variscan hinterland. Although we are limited in extrapolating isotope elevation relationships into the distant past, our results indicate that this Variscan area was high enough to block air masses from the SE and induces an orographic rainshadow to the North.A minimum mean elevation of ~ 3.4 km is reinforced using a new empirical relationship between elevation and the stable isotope composition of precipitation and surface waters (-1.5‰/km for δ18O & -14‰/km for δD) established across the Western Southern Ecuadorian Andes, which, like the Variscan belt was during the Carboniferous, is located at (or near) the Equator.