Late-glacial Coleoptera and the paleoclimate at Hirtles, Nova Scotia

Abstract

Paleoentomological studies of Coleoptera from a late-glacial site at Hirtles, Nova Scotia, Canada, produced a tundra-treeline to northern boreal assemblage during the interval 12,300 to 11,700 years B.P. This is one of the oldest late-glacial buried organic deposits in the Maritime Provinces of Canada and provides fossil beetle evidence for recently deglaciated environments in the region. Bark beetles indicate the presence of trees, perhaps as early as 11,900 years B.P. A comparison can be made with contemporaneous sites in central and eastern North America where coleopteran evidence suggests warmer temperatures. Coleoptera fossils demonstrate evidence of a climatic gradient from the Great Lakes to eastern Canada during this time interval possibly greater than occurs today.
 
 RÉSUMÉ
 Des études paléoentomologiques de coléopteres d'un emplacement tardiglaciaire, à Hirtes, en Nouvelle-&#xX9;cosse, au Canada, ont permis l'etablissement d'une limite de végétation des arbres et de toundra pour la florizone boréale septentrionale pendant l'intervalle de 12 300 à 11 700 ans avant le present. Il s'agit de l'un des plus anciens dépôts organiques tardiglaciaires enfouis dans les provinces maritimes canadiennes; il fournit une preuve de l'existence de coléopteres fossiles dans la région. L'existence de scolytes révèle la présence d'arbres, peut-être des 11 900 ans avant le présent. On peut effectuer une comparaison avec des emplacements contemporains dans le centre et Pest de l'Amérique du Nord, oû la preuve de la présence de coléopteres permet de supposer des températures plus chaudes. Les fossiles de coléoptères demontrent qu'il a existé pendant cet intervalle un gradient climatique possiblement supérieur à celui d'aujourd'hui, des Grands Lacs à l'Est du Canada.
 
 [Traduit par la rédaction]

Deglaciation of Nova Scotia: Stratigraphy and chronology of lake sediment cores and buried organic sections

“…He proposed that during the Younger Dryas organic sedimentation was merely suppressed, and no ice or snow was extant. The results of this study and others, however, Wilson et al, 1993;Levesque et al, 1994;1995) clearly indicate sedimentation rate increases during the Younger Dryas interval. The discrepancy between these studies may be explained by proximity to residual ice and snow, whereby significant sedimentation rate increases (and mineral sediment flux) were largely recorded in northern Nova Scotia, Maine and New Brunswick (Fig.…”

“…The southernmost site in Nova Scotia (Hirtles Beach; Fig. 1) features an unconsolidated organic and clay-rich diamicton, probably a solifluction deposit, overlying peat in a hollow between drumlins (Miller, 1995). Mass wasting processes were prevalent in the transitional areas between permanent snowfields to the north and seasonally frozen ground to the south.…”

“…Low shrub and herbaceous vegetation were the first to occupy the coastal landscape, usually low, wet protected areas or where soils were more suitable for plants to colonize (Mott and Stea, 1994). Trees began to migrate into the southern Nova Scotia, around 12.0 ka (Mott, 1991;Miller, 1995).…”

Late-glacial (Allerød – Younger Dryas) Coleoptera from central Cape Breton Island, Nova Scotia, Canada

“…The most complete published coleopteran sequence is from Gage Street in southwestern Ontario (Schwert et al 1985), where, at 12 800 BP, the assemblage contained open-ground and boreal species, including bark beetles. Compared with southwestern Ontario, colder conditions persisted at Hirtles (Miller 1995), Amaguadees, and Benacadie (4) (Schwert et al 198 l), to older than 12 800 BP at Brampton, Ontario (Morgan and Freitag 1982), to 12400 BP at Norwood, Minnesota (Ashworth et al 1981). Compared with southwestern Ontario, colder conditions persisted at Hirtles (Miller 1995), Amaguadees, and Benacadie (4) (Schwert et al 198 l), to older than 12 800 BP at Brampton, Ontario (Morgan and Freitag 1982), to 12400 BP at Norwood, Minnesota (Ashworth et al 1981).…”

“…3c) includes 0 . Its absence elsewhere during the 11 800 to 10800 BP interval (Miller and Morgan 1991;Miller 1995) suggests that 0 . Some of these species occurred in samples older than 11 800 BP.…”