Ordovician and Silurian trace fossils from northern Benin (W. Africa)

Among the trace fossils of the Kandi Sandstone, which was originally believed to be entirely Cretaceous in age, trilobite burrows (Cruziana) are the most telling elements. They allow to distinguish an Upper Ordovician unit with C. petraea, and a Silurian one with C. acacensis, in a lithologically uniform and tectonically disturbed section. Associated worm burrows (Arthrophycus spp. and Gyrochorte zigzag n. ichnosp.) are also distinctive. Apart from documenting marine ingressions far into the African craton, this result bears on the tectonic history and on the regional potential for hydrocarbons and deep aquifers.