The Chazy Fossil Reef National Natural Landmark includes three islands in Lake Champlain. Included within the designated area are two preserves on Vermont's Isle La Motte; the 20-acre (8.1 ha) Fisk Quarry Preserve and the 83-acre (34 ha) Goodsell Ridge Preserve are both open to the public and managed by the Isle La Motte Preservation Trust.[2] New York's Valcour Island and Garden Island are also included as part of the landmark.[3]
The reef is an observable portion of the larger Chazy Formation which extends from Quebec to Tennessee.[4] The location features an exposed Ordovician fossil reef, approximately 450 to 480 million years old, containing fossils from what was once a tropical marine environment.[5] The site is recognized as the oldest known fossil reef that contains substantial biological diversity.[1]
Strata from successive periods of time may be viewed across the landscape due to the tilted orientation of the sedimentary rock layers.[4] The presence of fossils from a continuous time series allow for the observation of faunal succession.[6] On Isle La Motte, the oldest fossils occur at the southern end of the island, with progressively newer layers visible toward the island's north end.[4]
