undifferentiated rock units

Paleontology and geology

After the Western Interior Seaway drained away, lakes and swamps filled the lowlands, and rivers flowed from the Rocky Mountains to the east and northeast. In the Early Tertiary, the climate was warm and humid. The land was covered with forests of sycamore, birch, and walnut, as well as katsura and dawn redwood, plants that were known to grow only in southeast Asia (until distribution by humans). Over time, the climate became cooler, and the forests were replaced by savannas and grasslands. Much of this plant material is preserved in Alberta’s coal fields, but fossils can also be found in sandstones and shales exposed in the south. These deposits have also yielded tracks and fossils of early mammals, including those of a venomous rodent-like mammal, Bisonalveus browni.