Holocene Insect Fossils from Two Sites at Ennadai Lake, Keewatin, Northwest Territories, Canada

Abstract

Ennadai Lake, in the forest-tundra ecotonal region of Keewatin, Northwest Territories, Canada, has been the subject of several paleoecological investigations (palynology, plant macrofossils, fossil soils). This study concerns Holocene insect fossils at Ennadai, a new approach in a region shown to be sensitive to climatic change. The Ennadai I site yielded 53 taxa, representing 13 families of Coleoptera and 7 families of other insects and arachnids, including abundant ants. These fossils range in age from about 6300 to 630 yr B.P. The Ennadai II site produced fossils of 58 taxa, including 13 beetle families and 15 families of other arthropods, ranging in age from 4700 to 870 yr B.P. The insect evidence suggests the presence of trees in the Ennadai region from 6000 to 2200 yr B.P. A conifer pollen decline from 4800 to 4500 yr B.P. at Ennadai has previously been interpreted as an opening up or retreat of forest in response to climatic cooling, but the insect fossils reveal the continued presence of trees during this interval. Both insect assemblages suggest trends of forest retreat and tundra expansion between about 2200 and 1500 yr B.P., presumably due to climatic cooling, with a return of woodland by about 1000 yr B.P.

Late Glacial and Holocene records of tree-killing conifer bark beetles in Europe and North America: Implications for forest disturbance dynamics

“…During the late Holocene, two sites in North America contained remains of D. rufipennis and D. brevicomis . One of the sites, located west of Hudson Bay, Canada (Elias, 1982), contained remains of D. rufipennis , and the other site, located in the Rocky Mountains in the United States (Elias et al, 1986), contained remains of D. rufipennis and D. brevicomis .…”

“…Dendroctonus ponderosae (red diamonds), Dendroctonus rufipennis (blue triangles), Dendroctonus brevicomis (orange stars), Dendroctonus simplex (yellow diamonds), Ips perturbatus (green squares) and Ips pini (pink triangles). Depicted sites with Late Glacial fossils are St. Hillaire (Mott et al, 1981), Johns Lake (Ashworth and Schwert, 1992), Norwood (Ashworth et al, 1981) and Huntington Dam (Elias et al, 1991); Early Holocene sites are Seibold (Ashworth and Brophy, 1972), 18 Miles River (Ashworth, 1977), Gage Street Site (Schwert et al, 1985), Lake Isabella Delta (Elias et al, 1986) and Lake Emma (Elias et al, 1991); Mid-Holocene sites are Hoodoo Lake (Brunelle et al, 2008), Baker Lake (Brunelle et al, 2008), Au Sable River (Morgan et al, 1985), La Poudre Pass LP5 (Elias et al, 1986) and Lake Isabella Peat (Elias, 1985); Late Holocene sites are Ennadai II (Elias, 1982) and Roaring River (Elias et al, 1986).…”

“…For these type of studies, single occurrences of primary bark beetle remains were sufficient evidence of the presence of host trees at the study site (e.g. Ashworth et al, 1981; Elias, 1982). In Europe, fossil insect remains have been used to reconstruct late-Glacial to early-Holocene climates (Coope et al, 1998).…”