From deglaciation to the Early Holocene in the northern Appalachians: A multiproxy palaeoenvironmental record from Scotstown Bog, Québec, Canada

Abstract

A multiproxy study of a sediment sequence from a Québec peatbog characterises the rapid and significant environmental responses to changing climatic conditions from the deglaciation of the Laurentide Ice Sheet to the early Holocene period. Scotstown Bog (45°30'45.0“N, 71°11'42.0“W) is an ombrotrophic peatland on the edge of the Appalachian Uplands in southern Québec, Canada. We reconstructed its Late-glacial and early Holocene palaeoenvironments for 14 000–6 000 cal a bp using palaeobotanical (plant macrofossil, macrocharcoal, pollen analyses), faunal (chironomid analysis), sedimentological (grain-size analysis, sediment organic content), and geochemical (sedimentary n-alkanes and hydrogen isotope analyses) methods. We targeted our multiproxy reconstruction on the Late-glacial period, which provides an example of how biota can respond to profound changes in climatic and environmental conditions. A major transition occurred between 13 000 and 12 900 cal a  bp, which is recorded in all palaeoecological proxies. Our reconstruction reveals two major environmental changes at this time. First, the Scotstown basin became isolated from a larger proglacial lake, as shown by sedimentological changes, sediment grain size and chironomid assemblage shift. Second, plant macrofossils and pollen influx show contemporaneous major shifts in the vegetation composition from tundra to tree-line to closed-canopy forested communities.