[1] The Chazy Fossil Reef National Natural Landmark includes three islands in Lake Champlain.

[3] The reef is an observable portion of the larger Chazy Formation which extends from Quebec to Tennessee.

[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] Among the preserved specimens are prehistoric stromatoporoids, gastropods, cephalopods, echinoderms, brachiopods, sponges, coral, bryozoa and stromatolites.