Transgressing Sauk Seas persisted into the Early
Ordovician, resulting in the deposition of marine limestone, mudstone and
dolostone. Equatorial continental margins continued to provide ample resources
to support burgeoning populations.
The above image depicts an ancient Atlantic
Ocean (Iapetus Ocean) separating the Taconic arc from Eastern North America.
An eastward dipping subduction zone on the western side of the Taconic arc
portends a Late Ordovician collision as part of Iapetus is subducted resulting
in a suturing of the Taconic Arc onto Eastern North America. Remnants of this
arc are present in Vermont and New York State.
Middle
Ordovician
During
the Middle Ordovician, a regional extinction
in Eastern North America. This regional extinction has been attributed to
volcanic activity, due to volcanic ash (456+1 Ma) deposits from Virginia to
Minnesota. Volcanic eruptions are a significant factor in extinction
events, although these have been overshadowed by the much more popular
meteorite impact theorists in recent years.
Go to LATE ORDOVICIAN