undifferentiated rock units

Paleontology and geology

During the Cambrian, the central and eastern parts of Northwest Territories were above sea level. Sediments eroding from land were deposited over the continental shelf and slope that covered the rest of the territory. In shallow lagoons and mudflats close to shore, sea water evaporated from time to time, leaving deposits of salt and gypsum along with sandstone and mudstone. The shallow waters a little farther from land accumulated limestone, while shales and deposits from underwater avalanches formed in deeper waters of the shelf and slope. Archeocyathids, brachiopods, trilobites, and conodonts lived in these warm seas, and their fossils are preserved in some of the shallow and deep water deposits. Some rocks from below the surface even contain fossils of Burgess Shale type animals, such as Anomalocaris, Wiwaxia, and crustaceans. Many rocks from this time have been eroded or covered by younger rocks, but some exposures can be found in the center of the territory. Additional exposures may be included in the undifferentiated Paleozoic rocks on this map.