In this image we see the ashes and sediments associated with the Island Arcs that have experienced epidote alteration. That is what gives them their blue-green color. Though these volcanically derived deposits were created at the same time as the Antler, there are no evidence of ashes or volcanic fragments in the Orogeny, suggesting that the Arcs were still far away from the edge of North America during Antler time. -------------- An interesting thing to know about the sediments created in Arc Complexes is that most of the volume of material that we see is not the primary eruptive deposits but rather the materials eroded off the volcanic edifices. Thus they are mostly sedimentary deposits of volcanic materials.