Ostracodes and paleoenvironments of the late Quaternary Don and Scarborough Formations, Toronto, Ontario

Popławski, Szymon; Karrow, P. F.

doi:10.1139/e81-140

Cited by 18 publications

(12 citation statements)

References 7 publications

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“…Eyles and Clark conclude (p. 1120) that the "Don Beds accumulated in a lower shoreface setting, probably adjacent to a large river." This conclusion is quite similar to those reached on the basis of fossil evidence (Duthie and Mannada Rani 1967; Poplawski and Karrow 1981;Hann and Karrow 1984).…”

Section: Don Formation and The Don -Scarborough Contactsupporting

confidence: 91%

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

Karrow¹

1989

Can. J. Earth Sci.

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Section: Don Formation and The Don -Scarborough Contactsupporting

confidence: 91%

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

Karrow¹

1989

Can. J. Earth Sci.

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“…Unpublished amino-acid determinations yield ratios compatible with a last interglacial age (see Karrow 1984).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: 94%

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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“…Poplawski and Karrow (1981) reported a dozen species with Candona rawsoni and Candona caudata as most abundant. The ostracode assemblage was interpreted as indicating combined river and lacustrine environments with a climate similar to the present (Table II).…”

Section: Ostracodesmentioning

confidence: 99%

Interglacial Beds at Toronto, Ontario

Karrow¹

2007

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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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Ostracodes and paleoenvironments of the late Quaternary Don and Scarborough Formations, Toronto, Ontario

Cited by 18 publications

References 7 publications

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

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

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

Interglacial Beds at Toronto, Ontario

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