Isle La Motte Chazy Reef Fossil Hunting Guide

Introduction

Isle La Motte is a small island at the northern end of Lake Champlain, in the far northwest corner of Vermont. Its bedrock holds the Chazy Reef, which is among the oldest reefs on Earth known to have been built by a diverse community of different animals rather than by microbes alone. The reef grew in a tropical sea during the Middle Ordovician, when the land that is now Vermont lay south of the equator. Two public preserves on the island, Goodsell Ridge and the nearby Fisk Quarry, expose the reef rock and let visitors walk across the fossils where they formed.

This is a place to look, not to collect. The reef is a National Natural Landmark, and the preserves protect the fossils in place so that the structure of the ancient reef can still be read in the rock. The fossils are large and easy to see on the weathered limestone surfaces, and interpretive material and trails help visitors make sense of them. This guide covers how to reach the preserves, what the reef contains, its geological story, the access rules, and the practical details for a visit.

Location and Directions

The Goodsell Ridge Preserve is at 69 Pine Street on Isle La Motte, in Grand Isle County, near 44.874 degrees north, 73.339 degrees west. The Fisk Quarry Preserve is a short distance away on the same island. Both are managed by the Isle La Motte Preservation Trust.

Isle La Motte is reached by road from the Vermont mainland across a series of bridges through the Lake Champlain islands, or from the west via the causeway at Rouses Point, New York. Once on the island, follow local signs to the preserves. Goodsell Ridge has a parking area and a small welcome center that is open seasonally.

The preserves are open to the public. Goodsell Ridge is open dawn to dusk year-round and is free to visit, with self-guided trails across the fossil-bearing rock. Facilities are limited, so bring water, and check the Isle La Motte Preservation Trust for current welcome-center hours if you want to visit the exhibits.

What Fossils You'll Find

The Chazy Reef preserves the animals that built and lived on an ancient reef, and they are visible in place on the weathered limestone rather than as loose specimens to gather. The main reef-builders were stromatoporoids, layered mound-shaped animals related to sponges, which appear as rounded masses in the rock. Early corals grew alongside them, adding to the reef framework.

Among and around the reef-builders are the shells of other animals. Gastropods, the coiled snails including the large form Maclurites, are a common and striking sight, showing as spiral cross-sections on cut and weathered surfaces. Straight-shelled nautiloids, the cone-shaped cephalopods that were among the top predators of the Ordovician sea, appear as long tapering shapes in the stone. Crinoids, bryozoans, and brachiopods fill out the community. Together they record one of the earliest times that many different kinds of animals combined to build a reef, which is what makes the site scientifically important.

The fossils show best on clean, weathered rock surfaces and in the old quarry faces at Fisk, where the reef is cut in cross-section. Wetting a surface or visiting in low-angle morning or evening light can make the shapes stand out.

Geologic History

The Chazy Reef formed during the Middle Ordovician, roughly 460 to 470 million years ago. At that time the fragment of crust carrying present-day Vermont lay in warm tropical waters well south of the equator, on the margin of an ancient continent. In that shallow sea, stromatoporoids, corals, and other animals grew together into a reef, one of a chain of such reefs that ran for hundreds of miles along the continental shelf. The Isle La Motte exposures preserve some of the most complete of these.

Over the hundreds of millions of years that followed, the reef rock was buried, hardened into limestone, and then slowly lifted and tilted as the mountains of New England were built. Erosion eventually stripped away the overlying rock and exposed the reef at the surface. Quarrying on Isle La Motte in the nineteenth and twentieth centuries cut into the same limestone, which was prized as a building stone, and those quarry faces, now protected at Fisk Quarry, give a clear cross-section through the ancient reef.

Collecting Rules and Regulations

Fossil collecting is not allowed at the Isle La Motte preserves. The Chazy Reef is a designated National Natural Landmark, and the Goodsell Ridge and Fisk Quarry preserves exist to protect the fossils in place. Visitors are welcome to walk the trails, view the fossils on the rock surfaces, and take photographs, but removing, hammering, or defacing any fossil or rock is prohibited.

Stay on the marked trails and viewing areas, and do not climb on or disturb the reef exposures. Treating the site as an outdoor museum is what keeps the reef intact and readable for future visitors and researchers. If you want a closer look or a guided explanation, the Isle La Motte Preservation Trust runs interpretive programs and can advise on visiting.

Safety

The preserves are gentle ground, but a few cautions apply. The weathered limestone can be uneven and slick, especially when wet, so wear sturdy shoes and watch your footing on the rock surfaces and around the old quarry at Fisk. Keep back from the edges of the quarry faces.

The island is rural, with limited services, so bring water, sun protection, and insect repellent in the warmer months. Cell coverage can be patchy. There are no cliffs or fast water at the trails, so the main hazards are simply uneven rock and exposure to sun and biting insects in summer. Watch children around the quarry edges.

Sources

https://ilmpt.org/ https://en.wikipedia.org/wiki/Chazy_Fossil_Reef https://www.lclt.org/goodsell-and-fisk-quarry-preserves/