undifferentiated rock units

Paleontology and geology

In the Early Carboniferous, eastern New Brunswick was flooded by a shallow sea, called the Windsor Sea. In very shallow areas, the water would often evaporate, leaving deposits of salt and gypsum, which are economically important today. After the sea retreated, rivers coursed between the mountains, and lakes developed in the lowlands. Sandstones, mudstones, and limestones deposited in these lakes contain fossils of fish, invertebrate traces, and algae. These rocks also contain oil shales form which oil and gas are produced.

In the Late Carboniferous, the climate became more humid, and plants like Calamites, a horsetail that grew to 30 meters, and lycopsids formed extensive forests and swamps. Land snails and insects, including gigantic ones like Arthropleura, a two-meter-long millipede, thrived in the swamps. Many different reptiles wandered through the forests and floodplains, leaving their tracks in the sand and mud. The lakes were home to foraminifera, ostracods, bivalves, fish, and sharks. Fossils of these animals and plants are preserved in the sandstones, mudstones, limestones, and coal deposits around central, eastern, and southern New Brunswick.

By the end of the Carboniferous, the climate became drier, and the wetland plants were replaced by more drought-tolerant species. Rivers and lakes accumulated sediments eroding from the highlands, forming the reddish-colored conglomerates, sandstones, and mudstones found in northern New Brunswick.