CORRELATION OF VARVES OF GLACIAL LAKE WINOOSKI, NORTH-CENTRAL VERMONT

In late-glacial time, the northwest-draining Winooski River basin was dammed by the retreating Late-Wisconsinan ice sheet to form glacial Lake Winooski. The lake expanded down the Winooski River valley until a lower outlet was uncovered and then it drained. Classic clay-silt varves resting on till record the history of Lake Winooski. In 1928, Ernst Antevs published a correlation of varves in the Winooski basin with the New England varve chronology that he had developed for the Connecticut Valley. His Lake Winooski curve extends from NE varve 7059 to 7288. In this study we report on two sites. The first, the Muzzy Road varve section, no longer exposed and on private property, is in the Northfield 7.5-minute quadrangle 6.8 km S40°W of the Vermont State Capitol Building. Of 280 varves measured, 130 varves near the top correlate well with Antevs’ Lake Winooski varve curve from NE varve 7125 to 7254. The lower 150 varves extend back to about NE varve 6982, or 77 varves below the base of Antevs’ varve curve. The Muzzy Road section at about NE varve 7274 is disconformably overlain by 4.0 m of massive clayey silt with deformed varves and ball-and-pillow structures, which may have formed when Lake Winooski drained. The second site, the Wrightsville Dam varve section, is accessible and on public land. The site is in the Montpelier 7.5-minute quadrangle 5.55 km N3°E of the Vermont State Capitol Building. The upper 101 varves of 183 varves measured correlate well with Antevs’ NE varve 7097 to 7197. The lower 82 varves extend back to NE varve 7017, 42 varves below Antevs’ curve for Lake Winooski. The top of the Wrightsville Dam section is truncated by younger terrace/fan deposits. Using Antevs’ youngest varve (NE 7288) and the Muzzy Road oldest varve (NE 6982), the data indicate that Lake Winooski existed for a minimum of 307 years.