FIGURE 5 EARLY COVEVILLE MAXIMUM COVEVILLE
Figure 6. Looking west from the top of Mount Philo State Park. The Adirondack Mountains are on the skyline, Lake Champlain in middle background and the Champlain Lowlands stretch from Lake Champlain to the base of Mount Philo.
FIGURE 7 FORT ANN MAXIMUM MARINE MAXIMUM
Shortly after Coveville Lake Vermont reached its maximum size (see map, [Fig. 5]B), a southern gorge-outlet was formed at an elevation lower than the previous Coveville outlet in the vicinity of Fort Ann, New York (Fort Ann is located approximately 8 miles south of the present southern extremity of Lake Champlain). The level of Lake Vermont’s water dropped to the new Fort Ann Stage (see map, [Fig. 7]A). Evidence for this new lake level is seen on the slopes of Mt. Philo, Snake Mountain and Cobble Hill. These lake-level features are parallel to and found 100 feet below those of the Coveville Stage. These parallel features, then, indicate that very little, if any, tilting of the earth’s crust had taken place between the Coveville and Fort Ann lake stages.
Figure 8. Beach and clay banks exposed along the Lake Champlain portion of Button Bay State Park. This view is toward the northwest and includes a major portion of the Park’s lake frontage. Photo by Robert B. Williams.
This Champlain ice lobe continued to melt and retreat toward the Canadian border and beyond. As the glacial front approached the St. Lawrence valley, fresh water from Lake Vermont began to seep through the retreating ice lobe and into the marine waters which filled the St. Lawrence area. Several shoreline (lake-level) features are found at different elevations below the Fort Ann Stage of Lake Vermont and attest to a slow lowering of the lake level by the escape of fresh water to the north.
The conspicuous clays of Button Bay State Park were deposited during the next episode in the history of the Champlain Valley, a development heralded by continued retreat of the ice lobe and contact with the St. Lawrence marine waters. Let’s take a look at the clays so well displayed along the Button Bay State Park beach and see if we can piece together their history.