Trace fossils from the cambro-ordovician rocks of North Wales and their stratigraphic significance

In North Wales, Cruziana semplicata (Salter) is recorded from three otherwise unfossiliferous localities and Teichichnus sp. (Seilacher) and Phycodes circinatum (Richter) are shown to be widely distributed within the lower Arenig (Didymograptus extensus zone) sediments. P. circinatum is also recorded from the otherwise unfossiliferous Upper Pennant Quartzite. From a discussion of the stratigraphic ranges of these trace fossils it is suggested that the rocks of the C. semplicata bearing localites are Upper Cambrian (Ffestiniog) in age while the Upper Pennant Quartzite is Ordovician, probably Arenig.