In late Early Cambrian to Ordovician rocks, acritarchs and trilobites are the most common fossils. Accompanying the trilobites may be less abundant inarticulate brachiopods, graptolites and hyolithids. In central Newfoundland, articulate brachiopods, bivalves, bryozoa, cephalopods, conodonts, corals, crinoids, gastropods, graptolites, ostracodes, trace fossils and trilobites are variably found in marine-deposited conglomerate, limestone, sandstone, shale and slate of Ordovician and Silurian age.
Fossils are particularly common on New World Island.
Western Newfoundland and southeastern Labrador have the greatest variety of fossils. These occur on the Port au Port Peninsula and the Great Northern Peninsula. Greater Labrador holds the distinction of having both the oldest and youngest fossils in the province. These assemblages have been used to define biostratigraphic zones. The ase of each zone is defined by the first appearance of its characteristic species.