9405114 Landing PIs and collaborators will develop new biostratigraphic and geochronologic bases for correlation of the Lower-Middle Cambrian of Avalon and Morocco. Detailed work on the small shelly fossils of the Avalon sequence, combined with high-precision geochronology, will provide a significantly refined time scale for this important time in evolution of life on Earth. Study of Moroccan sequence will permit correlation, and allow extension of the study in the time scale. Work will also contribute to understanding the tectonic history of these Cambrian platforms.