undifferentiated rock units

Paleontology and geology

Intense tectonic activity in the Early Carboniferous caused further uplift of the Antler Mountains. To the east and south of these mountains, carbonate reefs continued to accumulate in the shallow sea, eventually forming limestone. Occasional pulses of tectonic activity uplifted this carbonate shelf slightly, exposing it to erosion. To the west of the Antler Mountains, a deep ocean basin accumulated chert and shale rich in the skeletons of marine plankton. Some of the chert is colored red by the presence of iron oxides, indicating that the ocean bottom had good circulation with plenty of oxygen. Brachiopods and coral are common fossils from this time period.