The Torridonian sediments formed in a Proterozoic rift nearly contemporaneous with the Keweenawan Supergroup of North America. The book contains the first complete field description of rocks and sedimentary environments in which they formed, together with a comprehensive examination of their tectonic, palaeoclimatic significance, palaeomagnetism and diagenesis. It includes the results of over forty years work by the author, most of it previously unpublished.