Pleistocene paleoecology of the Don and Scarborough Formations, Toronto, Canada, based on cladoceran microfossils at the Don Valley Brickyard

Cladoceran microfossil evidence has confirmed that a disjunction in environmental conditions existed during deposition of the Don and Scarborough Formations in Toronto, Ontario. Although mean annual temperatures were distinctly warmer during the Don interval than in the Scarborough, they were probably similar to the present-day regime. The cladoceran community was almost exclusively composed of littoral species throughout the sequence, suggesting that the deposition site was a shallow-water lentic habitat. Chydorid cladoceran species richness in the Don Formation averaged four times that in the Scarborough. Past community structure, water depth, and trophic state changes at the site were reconstructed from the proportions of littoral to planktic species, the proportions of sediment- to vegetation-preferring chydorids, and the species diversity and equitability.