Late Triassic-Early jurassic volcanism along the southern Afar-plateau margin

Abstract

Field mapping carried out along the escarpment bordering the southern Afar has revealed the presence of trachyte lava flows and tuffs up to 30 m thick and extending in an east-west direction parallel to the strike of the escarpment. The trachyte is intercalated with the Lower Sandstone Unit, which suggests a Late Triassic-Early Jurassic age for the volcanics.

The regional Mesozoic sedimentary sequence includes the Jurassic Limestone Unit and the Cretaceous Upper Sandstone Unit. These are absent from the eastern part of the study area but are extensive on the western side.

Tensional tectonics is expressed by block-faulting in the region underlain by the Lower Sandstone-trachyte intercalation whereas warping is characteristics of the region underlain by extensive Mesozoic-Tertiary units.

It is suggested that the study area constitutes part of an uplited landmass which was only peripherally affected by Mesozoic transgression. This uplift resembles the Tertiary doming in the region and may have been its precursor.