La végétation postglaciaire du Témiscamingue, Québec, durant l'épisode glaciolacustre Barlow

Abstract

The 14C ages of the basal organic deposits accumulated in 32 small lakes located higher than or near the altitudinal limit of proglacial Lake Barlow, in Témiscamingue, span the period between 10400 and 6490 years BP. A regional pollen zonation has been established, allowing the rejection of the 14C ages younger than 8500 years BP, as minimum ages for local ice retreat. From 10400 to 8500 BP, whatever the age of the lake, the same general sequence of vegetation has spread over the deglaciated landscapes. The initial vegetation was dominated by Picea and Larix (pollen, macrofossils) and included Quercus, Ostrya, Ulmus, and Fraxinus (pollen influxes equal or greater than what they are today) along with plants having a present-day mainly arctic distribution such as Dryas integrifolia and Silene acaulis (macrofossils). The initial proglacial vegetational environment on the islands or around Lake Barlow was thus an open conifer forest with arctic plants and groves of relatively thermophilous deciduous trees, whatever the age of the onset of sediment accumulation in the lakes studied, between 10400 and 8500 years BP. After the initial vegetation was established and within a few centuries, Betula papyrifera, Populus tremuloides, Populus balsamifera, Pinus banksiana, and Abies balsamea (macrofossils, pollen) joined the other trees around each lake, whatever the age or location.