DIATOM ASSEMBLAGES FROM PLEISTOCENE INTERGLACIAL BEDS AT TORONTO, ONTARIO

Abstract

Interglacial beds from the Don Valley brickyard at Toronto were sampled systematically for diatoms. In 34 samples, 11 contained diatoms, and a total of about 200 species and varieties were identified. The dominant species are Tabellaria fenestrata (Lyng.) Kütz, Opephora martyi Héribaud, Cocconeis disculus var. diminuta (Pant.) A. Cl., Amphora proteus Greg., and Achnanthes clevei Grun. The overall assemblage suggests deposition in a freshwater estuary in alkaline, mesotrophic, or eutrophic water. The variation in ecologic composition of the samples indicated shifting of the river channel or repeated shallowing and deepening of the estuary. With some exceptions, the diatom flora is typical of temperate North America today, but the lack of knowledge of the extant diatom flora precludes a closer comparison.