undifferentiated rock units

Paleontology and geology

During the Silurian, much of Northwest Territories was above sea level, and sediments eroding off the land were deposited in the shallow to deep waters that covered the northern and western parts of the territory. These warm, tropical seas were home to sponges, trilobites, brachiopods, bryozoans, conodonts, ostracods, graptolites, and phyllocarids (a type of crustacean). A variety of fish swam in these waters too, including thelodonts (jawless fish with tiny scales), heterostracans (armored jawless fish), and acanthodians (jawed fish). Although many of the rocks from this period have been eroded or covered by younger deposits, fossils of these animals are preserved in small exposures of sandstone, shale, and limestone in this territory. On this map, some rocks may be included in the undifferentiated Paleozoic rocks, and they may appear on other more detailed maps.