THE MORPHOTECTONIC EVOLUTION OF RIFT-MARGIN MOUNTAINS IN CENTRAL KENYA - CONSTRAINTS FROM APATITE FISSION-TRACK THERMOCHRONOLOGY

Abstract

Passive margin mountains and rift flank uplifts are common features of extended continental areas. Apatite fission-track thermochronology of Proterozoic rocks from mountain ranges east of the Kenya Rift in central Kenya reveals episodes of rapid cooling and denudation, in Early Cretaceous (130-110 Ma), Late Cretaceous-Paleocene (70-60 Ma), and possibly Miocene ( ∼ 10 Ma) times. During the Early Cretaceous ∼ 1.2-2.0 km of denudation occurred in this area, and evidence for this is preserved in the Karisia Hills. The Late Cretaceous-Paleocene episode is well documented from escarpments along the western margin of the Anza Rift including the Mathews Range. Detailed fission-track age profiles up ..