| Lockport Group | |
|---|---|
| Stratigraphic range:Sheinwoodian-Homerian ~433–427 Ma | |
| Type | Group |
| Unit of | Cayugan Series |
| Sub-units | |
| Underlies | Vernon Formation |
| Overlies | Clinton Group |
| Lithology | |
| Primary | Dolomite |
| Other | Limestone,Chert |
| Location | |
| Region |  New York, Ohio, Pennsylvania, West Virginia |
| Country |  United States, Canada |
| Extent | Appalachian Basin,Michigan Basin |
TheLockport Group is ageologic group in theAppalachian Basin andMichigan Basin in the northeasternUnited States andCanada. This unit makes up theNiagara Escarpment. Its most famous feature isNiagara Falls. The unitoutcrops inNew York,Ontario,Michigan,Wisconsin, andIllinois.[1]
The Lockport Group is made up of four formations. From base to top:Gasport Formation,Goat Island Formation,Eramosa Formation andGuelph Formation. The entire unit is composed ofdolomite, with the exception of the Gasport which can belimestone, as well as occasionalchert nodules.[2]
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The Guelph Formation is at the top of the Lockport Group. It has been called the "Vernon Transition Zone" due to thin beds and laminations between carbonates, claystones and evaporates. Its base is delimited by astromatolite bed.
Below the Guelph is the Eramosa Formation. This formation is typically a thinly laminatedpackstone andgrainstone. There are stromatolite beds as well as corals preserved in this formation. Near the base the unit becomesvuggy. Again the top of this formation is marked by a sharp change between grainstone and a stromatolite bed.