The Rocourt Tephra, a widespread 90–74 ka stratigraphic marker in Belgium

A new study of the stratigraphy and composition of the Rocourt Tephra is performed at five sites in Belgium and brackets the age of the tephra between 90.3 and 74 ka. The volcanic glass grains have a typical shape of phreatomagmatic eruption products. A large set of tephra minerals were analyzed, namely clinopyroxene, orthopyroxene, amphibole, and Cr-spinel. The compositions of these minerals have been compared with the lava xenocrysts, megacrysts, and phenocrysts of the proximate Eifel volcanic province for which the origin has been determined (mantle xenoliths, high-pressure cumulates, and middle- to low-pressure magmatic phases). This allowed us to determine the likely origin of the tephra minerals. The Rocourt Tephra source could be a West Eifel volcano that was fed by a deep-seated magma batch rich in high- to middle-pressure minerals.