Answer. The oldest rock is the lava flow. Then the Cambrian Arkosic Sandstone followed by the Shale. The youngest feature is the dike by the prinicple of cross cutting relationships.
Cool. So now all we need to do is to figure out the absolute ages of these events. It is tempting to want to simply date feldspars from the Arkosic Sandstone do get a direct date for the Cambrian. The problem is that the feldspar in a clastic rock weathered from some igneous or metamorphic rock somewhere to become deposited with the rest of the arkosic sand. The age of the feldspar reflects the age of the igneous or metamorphic rock that supplied it to the sediment that eventually became the sandstone. The best we can tell is that the Cambrian must be younger than that.