undifferentiated rock units

Paleontology and geology

Throughout the Ordovician, the entire Yukon Territory was under water. Deeper basins still existed in the north and southeast, while the shallow waters of the continental shelf covered most of the territory. The continental slope dropped down to the open ocean over the southwestern part of the territory. Deeper waters accumulated shales and cherts, whereas limestones, sandstones, and siltstones were deposited in the shallower areas. These warm, tropical seas were home to many marine invertebrates, including sponges, trilobites, brachiopods, graptolites, and conodonts.