Deglaciation and late-glacial climate change in the White Mountains, New Hampshire, USA

Abstract

Recession of the Laurentide Ice Sheet from northern New Hampshire was interrupted by the Littleton-Bethlehem (L-B) readvance and deposition of the extensive White Mountain Moraine System (WMMS). Our mapping of this moraine belt and related glacial lake sequence has refined the deglaciation history of the region. The age of the western part of the WMMS is constrained to ~14.0–13.8 cal ka BP by glacial Lake Hitchcock varves that occur beneath and above L-B readvance till and were matched to a revised calibration of the North American Varve Chronology presented here. Using this age for when boulders were deposited on the moraines has enabled calibration of regional cosmogenic-nuclide production rates to improve the precision of exposure dating in New England. The L-B readvance coincided with the Older Dryas (OD) cooling documented by workers in Europe and the equivalent GI-1d cooling event in the Greenland Ice Core Chronology 2005 (GICC05) time scale. The readvance and associated moraines provide the first well-documented and dated evidence of the OD event in the northeastern United States. Our lake sediment cores show that the Younger Dryas cooling was likewise prominent in the White Mountains, thus extending the record of this event westward from Maine and Maritime Canada.

Guidebook for Field Trips in Western Maine and Northern New Hampshire

“…Fowler (2013) proposed these landforms are moraines using the following rationale. Earlier but just recently published findings of Thompson, et al (2017 and Fig. 3), suggest that near-glacial conditions may have existed in the region immediately following departure of the LIS and due to its close proximity during the now confirmed nearby stillstand.…”

“…He continued to find no convincing evidence for post-LIS cirque activity in the cirques, generally postulating that post-LIS regional climate warmed so rapidly that equilibrium-line altitudes rose too quickly above the cirques floors to support cirque glaciers. Thompson and Fowler, 1989;Thompson et al, 1999;Fowler, 1999Fowler, , 2011Fowler, , 2012and Thompson et al, 2017 established that moraines deposited by late-glacial readvance or standstill of the LIS 5 to 8 km northwest of the Presidential Range are part of the White Mountain Moraine System (Fig. 3) that extends irregularly west to east across the region.…”

“…This trip visits the northwestern White Mountains, where a wide variety of glacial and glacial-lake deposits formed during recession of the Laurentide Ice Sheet (Thompson et al, 2017). We will examine key sites that turned up during recent field studies and see examples of new LiDAR imagery that is being used to refine the mapping of glacial features in the area.…”

Applying the Cosmogenic Nuclide Dipstick Model for Deglaciation of Mt. Washington

“…Perhaps a local Appalachian ice sheet or ice cap covered the mountainous areas of northern New England during parts of the late Wisconsinan, an idea invoked long ago by Flint (1951). However, the moraine record in the lowlands adjacent to the Presidential Range to the north and the North American varve record from glacial Lake Hitchcock to the west suggest continental ice recession toward the north during deglaciation (Thompson et al, 1999(Thompson et al, , 2017Ridge;Ridge et al, 2012;Bromley et al, 2015). Bierman et al (2015).…”

“…In addition, a model of the LIS at the end of the Oldest Dryas (~15 ka) and during the Bølling-Allerød (~14.2 ka) found the surface balance increased during the Bølling , supporting the varve thickness record. As the ice sheet retreated further inland the Pineo Ridge moraine complex in coastal Maine was abandoned around the Bølling Interstadial (14.5 ± 0.7 ka; Koester et al, 2017) followed by the Littleton-Bethlehem moraine, just north of the Presidential Range in northern New Hampshire (13.8 ± 0.7 ka, n = 4; Balco et al, 2009;Thompson et al, 2017), and the Androscoggin moraine in northeastern New Hampshire and western Maine (13.2 ± 0.7 ka, n = 7; Bromley et al, 2015) before retreating further north into Canada.…”