DEGLACIATION AND GLACIAL LAKE SEQUENCE FROM THE WHITE MOUNTAINS TO LAKE COOS, UPPER CONNECTICUT RIVER BASIN, NEW HAMPSHIRE AND VERMONT

End moraines occur in the headwaters of the Israel River valley, just north of the Presidential Range in New Hampshire. These moraines formed simultaneously with the Bethlehem Moraine complex to the west. They provide further evidence of the Littleton-Bethlehem Readvance, which occurred ca. 12,000 BP (14C yr), probably due to Older Dryas climatic cooling. The NW-receding ice margin in the Israel valley dammed successively lower stages of glacial Lake Israel: the Bowman, Cherry Pond, and Lancaster stages at elevations of ~457, 338, and 309 m respectively. Concurrent ice recession in the adjacent Johns River basin to the southwest ponded stages of glacial Lake Carroll, followed by Lake Whitefield, at lowering elevations between ~429 m and a minimum of 282 m. Further deglaciation caused lakes Israel and Whitefield to merge with glacial Lake Coos in the Connecticut River valley, which extended from Gilman (just upvalley from Lake Hitchcock) at least 27 km to Brunswick, VT. Early high-level fan/delta deposits of Lake Coos occur from Guildhall north to Brunswick at elevations from ~287 m to at least 303 m. These deposits probably formed when the valley was blocked by a temporary ice and/or sediment dam in the Guildhall area. The tops of lower-level deltaic deposits range from ~270 m in Whitefield, NH to at least 293 m in Brunswick. During this lower stage of Lake Coos, morainic deposits dammed a narrow segment of the Connecticut valley at Gilman, temporarily forcing lake drainage west through a spillway at ~267 m between Gilman and East Concord, VT, and thence a short distance south to Lake Hitchcock. Postglacial erosion, valleyside fan deposition, and poor exposure hinder precise determination of Lake Coos levels and isostatic tilt.