An unusually rich and extensive 5 m sequence of organic-rich sediments (ca. 13 000 to ca. 4500 BP) from a drained glacial kettle near Brampton, Ontario, has produced a large and varied assemblage of fossil insects. Coleoptera (beetles) from the base include species typical of northern boreal or tree line habitats today. Approximately one metre above the base of the section (ca. 11 500 BP), there is an abrupt appearance of numerous bark beetles (family Scolytidae) and other Coleoptera that inhabit boreal forests. Temperate species whose ranges are predominantly or totally south of the Ontario border, appear, beginning at ca. 9500 BP, suggesting environmental conditions similar to modern ones. Younger Dryas and Pre-Boreal Oscillation cold events may be evident in lower parts of the boreal sequence, although considerations of temporal and climatic resolution make interpretation somewhat ambiguous.