Diatom Assemblages From Pleistocene Interglacial Beds at Toronto, Ontario

Duthie, H. C.; Rani, Rony

doi:10.1139/b67-246

Cited by 23 publications

(14 citation statements)

References 2 publications

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“…(1981) surmised from Scarborough Formation chironomid, beetle and caddisfly assemblages that the climate of southern Ontario was slightly cooler than at present during presumed Early Wisconsinan times. Williams & Morgan (1977) concluded from a caddisfly as semblage that the southern Ontario climate was at least as warm as at present during the last interglacial, agreeing with conclusions reached from pollen (Terasmae, 1960) and diatoms (Duthie & Mannada Rani, 1967). Elias & Wilkinson (1983) inferred from both beetle and caddisfly assemblages, that a cold tundra environment existed at Lobsigensee, Switzerland, about 13 500 B.P.…”

Section: Discussionsupporting

confidence: 54%

Factors affecting the interpretation of caddisfly assemblages from Quaternary sediments

Williams

1989

J Paleolimnol

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The use of assemblages of caddisflies (Trichoptera) in paleoecology has been explored over the past ca. 12 years. During this time, sites in North America, Great Britain and Europe have been studied and progress has been made in both the mechanics of identification and in the understanding of factors relevant to the interpretation of assemblages of this wholly aquatic group. Quaternary caddisfly fossils are abundant and usually well-preserved in waterlaid sediments. Individual larval sclerites can be identified by reference to shapes, textures, colour patterns muscle scar patterns and setal distributions. The flat frontoclypeus is particularly easily identified.Study of the biological and distributional data relevant to a caddisfly assemblage yields information at two levels. First the probable local habitat and second the climate can be described. This information is derived from both modern collections and the literature as the morphology of species, and hence it is assumed their environmental requirements, have not changed during the Quaternary. Comparisons with fossil assemblages of other plant and animal groups suggest that there are important factors to be considered in interpreting caddisfly assemblages, particularly those from sediments deposited during cold periods: for example, caddisflies may be slower to migrate than certain terrestrial insects, in particular the beetles (Coleoptera), and some glacial assemblages may therefore be dominated by 'hangers on'. Lotic and lentic species also may migrate at different rates.Although caddisflies have not yet been fully exploited as paleoecological indicators, they have already contributed to our understanding of past environments and warrant much greater use.

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Section: Discussionsupporting

confidence: 54%

Factors affecting the interpretation of caddisfly assemblages from Quaternary sediments

Williams

1989

J Paleolimnol

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“…Unpublished amino-acid determinations yield ratios compatible with a last interglacial age (see Karrow 1984). Ostracode, diatom, cladocera, and caddisfly populations have been described by Duthie and Mannadu Rani (1967), Williams and Morgan (1977), Poplawski and Karrow (1981), and Hann and Kmow (1984).…”

Section: Stratigraphy Of Site and Previous Investigationsmentioning

confidence: 95%

Last interglacial sediments of the Don Valley Brickyard, Toronto, Canada, and their paleoenvironmental significance

Eyles¹,

Clark²

1988

Can. J. Earth Sci.

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The Don Valley Brickyard in Toronto is an internationally designated type site in recognition of diverse faunal remains in the Don Beds of last (Sangamonian) interglacial age; pollen in overlying strata record the climatic deterioration marking the onset of the last (Wisconsinan) glacial cycle. New sedimentological descriptions show that the Don Beds, about 8 m thick, were deposited in a lacustrine lower shoreface environment subject to episodic storms. Storm-deposited sand facies are interbedded with peaty muds that are extensively bioturbated. Water depths, derived from wave-formed ripples using linear wave theory, appear to have increased during deposition of the Don Beds from about 2 m to about 18 m (12 -28 m above the modem lake level), a change that is recorded by an overall fining-up sequence. Increasing water depths may have been the result of isostatic recovery of the lake outlet to the east. The Don Beds overlie a thin bouldery deposit, possibly a remnant of older Illinoian glacial sediments (York Till). The interglacial beds pass up into prodelta rhythmites (Scarborough Clays) of a regionally extensive delta body, indicating continued deepening. Deepening was accompanied by steadily decreasing mean annual temperatures; upper deltaic sediments (Scarborough Sands), exposed to the east along lakeshore bluffs, were deposited in a cold-climate setting during the opening phase of the Wisconsin glaciation.La briqueterie Don Valley B Toronto est reconnue intemationalement comrne un site type de faune fossile diversifike incorporee dans les lits Don laissks par le demier stade interglaciaire sangamonien; les pollens inclus dans les strates sus-jacentes documentent le refroidissement du climat qui marque le dCbut du demier cycle glaciaire (wisconsinien). Une Ctude kcente kvkle que les lits Don, d'environ 8 m d'kpaisseur, furent dt5posCs sur les rives inferieures d'un environnement lacustre sujet aux effets des tempCtes Cpisodiques. Les faciks arknacks accumulks lors des tempCtes sont intercalks avec des boues tourbeuses intenskment bioturbkes. L'application de la thkorie des ondes lineaires h I'ktude des rides de vagues indique que 1'6paisseur de la tranche d'eau a augment6 de 2 m h 18 m (12-28 m au-dessus du niveau actuel du lac) durant la pCriode d'accumulation des lits Don, changement qui est reflkte dans la sCquence ~Cdimentaire par un grano-classement normal. L'augmentation de 1'Cpaisseur de la tranche d'eau peut avoir result6 du recouvrement isostatique de 1'Cmissaire est du lac. Les lits Don reposent sur un dkpbt mince riche en blocs, possiblement des ksidus laissks par la glaciation plus ancienne de 1'Illinoien (Till de York). De bas en haut, les lits interglaciaires ckdent la place aux rythmites prodeltaiques (argiles de Scarborough) d'un vaste delta rkgional, tCmoignant d'un accroissement continu de l'kpaisseur de l'eau. Un diminution continue des tempCratures annuelles moyennes accompagnait cette augmentation de 1'Cpaisseur de la tranche d'eau; les sCdiments deltaiques superieurs (sables de Scarboroug...

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“…Terasmae (1960) also listed 20 diatom taxa from the middle of the unit. More detailed work by Duthie and Mannada Rani (1967) extended the list to 200 taxa (Table II). Varied river mouth assemblages typical of temperate regions were identified, although interpretations were handicapped by limited knowledge of living assemblages.…”

Section: Plant Macrofossilsmentioning

confidence: 99%

Interglacial Beds at Toronto, Ontario

Karrow¹

2007

gpq

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Interglacial sediments have been known to occur at Toronto for about a century. There have been two main periods of attention: first by A. P. Coleman in the early twentieth century; and second mostly by the author and co-workers in the past quarter century. Attention was focussed early on the Don Formation because of its rich fossil assemblages. The Don Formation, consisting of gravel, sand, and clay, is commonly 6 to 9 m thick and has been encountered in outcrop only along the DonValley. However, excavations and borings indicate its presence under much of southern Metropolitan Toronto; it may continue northward along the Laurentian River Valley. Its only continuing, accessible exposure has been the Don Valley Brickyard. Early paleontological study emphasized molluscs, wood, leaves, and a few bones, which suggested a climate warmer than present. More recent studies have stressed microfossils. including pollen, diatoms, ostracodes. molluscs, Cladocera, insects, plant macrofossils, and microvertebrates. Altogether about 500 species have been identified, and the list is growing. Climatic indicators show that the Don Formation represents the declining temperatures of the waning half of an interglaciation. Although the Don Formation is beyond the range of radiocarbon dates and is undated, amino acid analysis on wood and shells support assignment to Sangamonian time. The overlying Scarborough Formation clay and sand, and the Pottery Road Formation sand contain mainly cold-climate fossils. These are in turn overlain by Early, Middle, and Late Wisconsinan tills and interbedded lacustrine sediments with corresponding radiocarbon and thermoluminescence (TL) dates.Les sédiments interglaciaires de Toronto, connus depuis environ un siècle, ont fait l'objet de recherches au cours de deux périodes principales; au début du siècle, d'abord, par A. P. Coleman, puis par l'auteur et ses collègues depuis les 25 dernières années. La Formation de Don a d'abord attiré l'attention en raison de ses riches assemblages de fossiles. Cette formation, constituée de gravier, de sable et d'argile, a habituellement de 6 à 9 m d'épaisseur. On ne l'observe que sous forme d'affleurements ici et là dans la vallée de Don. Toutefois, les excavations et les sondages montrent qu'elle est présente à peu près partout dans le sud de la région métropolitaine; elle pourrait se poursuivre le long de la vallée de la Laurentian River. Le seul endroit où l'on puisse l'observer de façon continue est à la Don Valley Brickyard. Les premières études paléontologiques sur les mollusques, le bois, les feuilles et quelques os indiquaient un climat plus chaud que maintenant. Des études plus récentes ont surtout porté sur les microfossiles, dont le pollen, les diatomées, les ostracodes, les mollusques, les Cladocera, les insectes, les macrofossiles de végétaux et les microvertébrés. Jusqu'à maintenant on a identifié 500 espèces. Les indicateurs climatiques montrent que la Formation de Don reflète les températures en baisse de la moitié déclinante d'un interglaciaire. Bien ...

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Diatom Assemblages From Pleistocene Interglacial Beds at Toronto, Ontario

Cited by 23 publications

References 2 publications

Factors affecting the interpretation of caddisfly assemblages from Quaternary sediments

Factors affecting the interpretation of caddisfly assemblages from Quaternary sediments

Last interglacial sediments of the Don Valley Brickyard, Toronto, Canada, and their paleoenvironmental significance

Interglacial Beds at Toronto, Ontario

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