The Cayugan Series contains a number of carbonate, shale and evaporite formations of the upper Silurian System of sedimentary strata in eastern North America. It was formed during a period of marine transgression, and is near the end of the placid shallow marine environments of the Cambrian through Ordovician periods. The end of the Taconic orogeny marks the beginning of the Cayugan. A number of changes were taking place as the Iapetus Ocean was slowly shrinking. The north end of the sea had already closed. At the end of the Silurian and of the Cayugan Series, the Iapetus Ocean had entirely closed, leaving behind the Iapetus Suture. A result of being closed at one end was that fluctuations in sea level allowed for large parts of the Appalachian and Michigan basins to form large evaporite deposits. All of these deposits are found with in the Salina Group. While the Salina covers an area from New York to Illinois south into Kentucky and Tennessee, the evaporites are primarily found in western New York, western and central Pennsylvania, eastern Ohio and north western West Virginia. As well as in the Michigan Basin.