Guidebook for Field Trips in Western Maine and Northern New Hampshire

Johnson, Beverly; Eusden, J. Dykstra

doi:10.26780/2017.001.0001

Cited by 1 publication

(1 citation statement)

References 172 publications

(305 reference statements)

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“…Such a delay is plausible in the northeastern US, where year‐round stadial conditions persisted until ~18 ka (Buizert et al, 2014; Lora and Ibarra, 2019). These cold, dry conditions, and the scant vegetation and occurrences of permafrost (Stone and Ashley, 1992) that resulted during the early deglacial period, were primarily controlled by changes in the North Atlantic regional climate (Shuman et al, 2004; Buizert et al, 2014; Osman et al, 2021). We surmise that during this relatively cold period, as much as several thousand years elapsed after the ice margin receded and before the landscape became vegetated enough that organic material, particularly macrofossils, were deposited in lake basin sediment in sufficient numbers to be found in sediment cores.…”

Section: Discussionmentioning

confidence: 99%

A critical re‐analysis of constraints on the timing and rate of Laurentide Ice Sheet recession in the northeastern United States

Halsted,

Bierman,

Shakun

et al. 2023

J Quaternary Science

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We review geochronological data relating to the timing and rate of Laurentide Ice Sheet recession in the northeastern United States and model ice margin movements in a Bayesian framework using compilations of previously published organic 14C (n = 133) and in situ cosmogenic 10Be (n = 95) ages. We compare the resulting method‐specific chronologies with glacial varve records that serve as independent constraints on the pace of ice recession to: (1) construct a synthesis of deglacial chronology throughout the region; and (2) assess the accuracy of each chronometer for constraining the timing of deglaciation. Near the Last Glacial Maximum terminal moraine zone, 10Be and organic 14C ages disagree by thousands of years and limit determination of the initial recession to a date range of 24–20 ka. We infer that 10Be inherited from pre‐glacial exposure adds 2–6 kyr to many exposure ages near the terminal moraines, whereas macrofossil 14C ages are typically 4–8 kyr too young due to a substantial lag between ice recession and sufficient organic material accumulation for dating in some basins. Age discrepancies between these chronometers decrease with distance from the terminal moraine, due to less 10Be inherited from prior exposure and a reduced lag between ice recession and organic material deposition. 14C and 10Be ages generally agree at locations more than 200 km distal from the terminal moraines and suggest a mostly continuous history of ice recession throughout the region from 18 to 13 ka with a variable pace best documented by varves.

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