undifferentiated rock units

Paleontology and geology

Cambrian rocks from Cape Breton Island and northern mainland Nova Scotia (the Avalon Zone) include limestones, sandstones, and shales, deposited in the shallow seas adjacent to Gondwana. They also include volcanic rocks that formed as the crust began to pull apart and bring magma closer to the surface. Most of these Cambrian rocks have since been metamorphosed. Fossils are not very common, but trilobites and bradoriids, an extinct type of bivalve crustacean have been found.

In southern Nova Scotia (the Meguma Zone), Cambrian rocks are formed from large volumes of sediment transported from the continent. This sediment accumulated into thousands of meters of sandstone and shale, which over time have been metamorphosed. They are the oldest rocks known from this terrane and underlie most of southern mainland Nova Scotia. Fossils in these formations are not very common, but trilobites, brachiopods, graptolites, trace fossils, and some of the oldest foraminifera have been found in these rocks. The trilobites are more similar to those of Europe than to North America, supporting the idea that this area was not part of Laurentia during the Cambrian.

Due to the complex history of Cambrian age rocks, including periods of metamorphism, intrusion, and erosion, many of the rocks may appear as undifferentiated Paleozoic rocks on this and other maps.