Mohawk Valley Fossils

New York during the later Ordovician

Strata deposited in New York State during the Ordovician are primarily found in two belts, one running east-west across the middle of the state, and another which runs north-south along its eastern edge. Here, we are only considering strata in the Mohawk River Valley ("Study Area") shown on this map of New York State. The strata were deposited during the Taconic orogeny, a time of subduction and mountain building along the area now known as the Taconic Front.

The rocks along the Western edge of the Taconic Front are highly deformed, the result of being compressed during this orogeny. Further west, at the site of this study, the rocks are not highly deformed, although there are numerous faults which cross the area parallel to the Taconic Front.

During the time that these rocks were deposited, the area to the west of the Mohawk River Valley was nearly flat-lying, and most of the sediment which accumulated there became limestone. To the east of the Mohawk River Valley, the sediments were deposited in a deep, North-South trending trench, and are primarily shales. The transition between limestones and shales is in the Study Area.