undifferentiated rock units

Paleontology and geology

In the Cambrian, the eastern margin of North America ended in Vermont, and Maine did not exist. The first parts of Maine were not assembled until the Ordovician, when ancient landmasses were accreted to North America and sediments were laid down along its margin. Nonetheless, Maine does have a fossil record from this time. Though not shown on this map, deep-water fossils have been found in the Grand Pitch Formation in northeastern Maine, representing Precambrian-Early Cambrian deposits, and in the Hurricane Mountain Formation in western Maine, representing Middle Cambrian-Ordovician. These organisms were never natives of Maine. Instead they lived out their lives somewhere else, died and became fossilized before becoming part of Maine later in the Ordovician.