Glacially redeposited pollen in tills of southern Ontario, Canada

Abstract

According to published opinion based on analytical data, the secondary pollen of subglacial till in the eastern Baltic region of Europe reflect the pollen assemblages of the preceding interstadial or interglacial sediment, including abundant thermo-philous pollen. Tills and glaciolacustrine sediments from 10 sites in southern Ontario, including the Don Valley Brickyard section at Toronto, where polynologically investigated to compare the pollen content in glacigenic deposits of various ages. Only one site (upper Bradtville till) contained a secondary pollen assemblage with abundant deciduous pollen, like those found in a Yarmouthian interglacial deposit in Indiana. In all the others, pine (Pinus) pollen dominate. This phenomenon is explained by glacial incorporation of sediments enriched in overproduced Pinus pollen, which had accumulated during either (i) a lengthy cool transitional period between the warm phase of the Sangamonian Interglacial and the first major Early Wisconsinan glacial advance, (ii) the interstadial Middle Wisconsinan, or (iii) the cool nonglacial episode of Illinoian and pre-Illinoian time. Therefore, the northern European model for distinguishing tills of different ages by their secondary pollen assemblages is applicable to southern Ontario only in exceptional cases. Pollen in the glaciolacustrine Early Wisconsinan Sunnybrook Drift sediments resembles those of Sunnybrook till, but are more variable in their preservation and composition and contain more pre-Quaternary palynomorphs.

The significance of pollen‐rich inorganic lake sediments in the Cratére du Nouveau‐Quèbec area, Ungava, Canada

“…Such a pollen-bearing till may act as a source for reworking into a younger, subsequent till sheet as a result of glacier erosion of the surficial deposits of the previous glaciation/interglaciation cycle, a process similar to the one discussed by Heinonen (1957) and Dreimanis et al (1989). The result would be a pollen-bearing till with recycled pollen grains (Florin 1975).…”

“…In the first case, the microfossils are derived from preglacial, interglacial or interstadial pollenrich sediments (soil humus, peat, lake sediment) that became incorporated into till as a result of the glacial erosion of the terrain over which the ice passed. This is the process sometimes referred to as 'reworking' or 'redeposition' (Dreimanis et al 1989;Gillberg 1977). A spectacular occurrence of pollen-bearing and even humus-rich till incorporating lake sediments is the Kauhajoki till in southern Finland Rainio & Lahermo 1976).…”

“…In their recent paper, Dreimanis et al (1989) BOREAS 20 (1991) Cratkre du Nouueau-QuCbec 137 review the significance of recycled pollen in tills from southern Ontario. Employing the methodology developed in Scandinavia, they attempt to use microfossils as a tool in till stratigraphy and genesis.…”

“…Employing the methodology developed in Scandinavia, they attempt to use microfossils as a tool in till stratigraphy and genesis. In contrast to the views of most palynologists, these authors believe that, instead of a nuisance, reworked pollen 'may become the main object of interest, whereas "new" pollen (which is contemporaneous with the formation and deposition of till, or even postdepositional) could be viewed as a disturbing factor' (Dreimanis et al 1989(Dreimanis et al : 1667.…”

Geological and geophysical studies of buried valleys and their fills near Elora and Rockwood, Ontario

“…7). Dreimanis et al 1989) remains unknown. The nature of the sediment would not require a long time for its deposition but, like the similar thick sequence in the Elora Valley hole (UWBH 34-78), it suggests a condition of drainage blockage in the buried valley with deposition in a long, narrow lake.…”