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Glacilacustrine Environment of Part of the Oak Ridges Moraine, Southern Document generated on 10/02/2021 12:20 p.m. Géographie physique et Quaternaire Glacilacustrine environment of part of the Oak Ridges Moraine, Southern Ontario Le mileu glaciolacustre d’une partie de la Moraine d’Oak Ridge, dans le sud de l’Ontario Glaziallimnische Umwelt eines Teils der Oak Ridge-Moränen im Süden von Ontario Robert Gilbert Volume 51, Number 1, 1997 Article abstract Glacilacustrine sediments in a 112 m core recovered from the Oak Ridges URI: https://id.erudit.org/iderudit/004824ar Moraine near Vandorf, Ontario are used to assess the environment at the time DOI: https://doi.org/10.7202/004824ar of deposition. Varves in the upper 23.7 m are of two types: thinner (20-110 mm) varves in groups of 29 and 23 at two levels. These are dominated by deposition See table of contents of silt in summer, with lesser amounts of laminated silts and sands representing turbidity current deposition. Thicker (0.18-1.02 m) varves at the base and top of the deposit as well as in a group of 27 between the thin varves Publisher(s) have a greater fraction in summer of coarser sediment deposited from gravity flows. Winter deposits of both are dominated by the clay- size fraction and Les Presses de l'Université de Montréal most show at least one parting of silt or sand associated with periods of increased meltwater inflow during winter. Carbonate content varies from ISSN 25-55 % with the highest proportion in the thinner deposits in winter and in the summer deposits of thin varves. It is proposed that a large, deep (greater 0705-7199 (print) than 100 m at least in the early phases) glacial lake was dammed on the Oak 1492-143X (digital) Ridges Moraine between the retreating Simcoe and Ontario lobes to the north and south, respectively, and the Niagara escarpment to the west. This lake Explore this journal existed as a relatively stable feature for at least 100 years. Cite this article Gilbert, R. (1997). Glacilacustrine environment of part of the Oak Ridges Moraine, Southern Ontario. Géographie physique et Quaternaire, 51(1), 55–66. https://doi.org/10.7202/004824ar Tous droits réservés © Les Presses de l'Université de Montréal,1997 This document is protected by copyright law. Use of the services of Érudit (including reproduction) is subject to its terms and conditions, which can be viewed online. https://apropos.erudit.org/en/users/policy-on-use/ This article is disseminated and preserved by Érudit. Érudit is a non-profit inter-university consortium of the Université de Montréal, Université Laval, and the Université du Québec à Montréal. Its mission is to promote and disseminate research. https://www.erudit.org/en/ Géographie physique et Quaternaire, 1997, vol. 51, no 1, p. 1-12, 8 fig., 2 tabl. GLACILACUSTRINE ENVIRONMENT OF PART OF THE OAK RIDGES MORAINE, SOUTHERN ONTARIO Robert GILBERT, Department of Geography, Queen's University, Kingston, Ontario, K7L 3N6, [email protected]. Manuscrit reçu le 8 janvier 1996 ; manuscrit révisé accepté le 21 mai 1996 ABSTRACT Glacilacustrine sediments in a RÉSUMÉ Le mileu glaciolacustre d'une ZUSAMMENFASSUNG Glaziallimnische 112 m core recovered from the Oak Ridges partie de la Moraine d'Oak Ridge, dans le Umwelt eines Teils der Oak Ridge-Moränen Moraine near Vandorf, Ontario are used to sud de l'Ontario. Une carotte de 112 m de im Süden von Ontario. Glaziallimnische Sed- assess the environment at the time of depo- sédiments glaciolacustres en provenance de imente aus einem 112 m langen Bohrkern sition. Varves in the upper 23.7 m are of two la Moraine d'Oak Ridge, près de Vandorf, en von der Oak Ridge-Moräne bei Vandorf, On- types: thinner (20 - 110 mm) varves in Ontario, a servi à reconstituer le milieu à tario, dienen bei der Bestimmung der Um- groups of 29 and 23 at two levels. These are l'époque de sa mise en place. Les varves welt zur Zeit der Ablagerung. In den oberen dominated by deposition of silt in summer, des 23,7 m supérieurs sont de deux types. 23.7 m gibt es zwei Typen von Warwen: with lesser amounts of laminated silts and Les varves fines (20-110 mm), en groupes Dünnere Warwen (20 - 110 mm) in Gruppen sands representing turbidity current deposi- de 29 et de 23 à deux niveaux, sont car- von 29 und 23 in zwei Niveaus. Diese sind tion. Thicker (0.18 - 1.02 m) varves at the actérisées par le dépôt de limon en été, avec von Schlammablagerung im Sommer be- base and top of the deposit as well as in a de moins grandes quantités de silt et de sa- herrscht, mit geringeren Mengen von blättri- group of 27 between the thin varves have a ble laminé, ce qui témoigne d'un dépôt dans gem Schlamm und Sand, was eine greater fraction in summer of coarser sedi- un courant de turbidité. Les varves plus Ablagerung bei Dichtigkeitsströmung bedeu- ment deposited from gravity flows. Winter épaisses (0,18-1,02 m) situées à la base et tet. Dickere Warwen (0.18 - 1.02 m) an der deposits of both are dominated by the clay- dans la partie supérieure du dépôt, ainsi que Basis und im oberen Teil der Ablagerung wie size fraction and most show at least one dans un groupe de 27 varves situé entre les auch in einer Gruppe von 27 Warwen zwis- parting of silt or sand associated with periods varves fines, comprennent davantage de chen den dünnen Warwen enthalten einen of increased meltwater inflow during winter. sédiments plus grossiers déposés en été à größeren Teil von gröberem Sediment, das Carbonate content varies from 25 - 55% with partir de glissements de terrain. Les dépôts im Sommer während Erdrutschen abge- the highest proportion in the thinner deposits d'hiver dans les deux cas sont caractérisés lagert wurde. Die Winter-Ablagerungen sind in winter and in the summer deposits of thin par la fraction argileuse et la plupart montre in beiden Fällen von der Lehm-Fraktion be- varves. It is proposed that a large, deep au moins un plan de séparation de silt ou de herrscht, und die meisten weisen mindes- (greater than 100 m at least in the early sable associé à des périodes d'augmenta- tens einen abgeteilten Strang von Schlamm phases) glacial lake was dammed on the tion du débit d'eau de fonte pendant l'hiver. oder Sand auf, den man auf Perioden ver- Oak Ridges Moraine between the retreating La teneur en carbonates varie de 25 à 55% stärkten Schmelzwasserflusses während Simcoe and Ontario lobes to the north and avec les proportions les plus élevées dans des Winters zurückführt. Der Gehalt an Kar- south, respectively, and the Niagara escarp- les dépôts les plus minces d'hiver et dans les bonaten variiert von 25 - 55 % mit dem höch- ment to the west. This lake existed as a rel- varves fines de l'été. Nous supposons qu'un sten Anteil in den dünneren Ablagerungen atively stable feature for at least 100 years. grand lac glaciaire profond (de plus de 100 m im Winter und in den Sommer-Ablagerungen au moins au cours des premières phases) a dünner Warwen. Es wird angenommen, daß été barré par la Moraine d'Oak Ridge, entre ein großer, tiefer (über 100 m, mindestens in les lobes récessifs de Simcoe et d'Ontario, der frühen Phase) glazialer See durch die respectivement au nord et au sud, et l'es- Moräne von Oak Ridge eingedämmt wurde, carpement de Niagara, à l'ouest. Ce lac est zwischen den jeweils nach Norden und demeuré une entité relativement stable pen- Süden zurückweichenden Loben von Sim- dant au moins 100 ans. coe und Ontario und dem Niagara-Steilhang nach Westen. Dieser See existierte in relativ stabiler Form mindestens hundert Jahre lang. 2 R. GILBERT INTRODUCTION diameter core was recovered by rotary drilling from 21 - 132.9 m below the surface (290 - 176 m a.s.l.) in 1.5 m long The Oak Ridges Moraine (ORM) in south central Ontario sections with missing portions up to 3 m between respective (Fig. 1 inset) was the locus of deposition over a relatively sections, some represented by small bulk samples of mixed long period of time, especially associated with the Simcoe sediment. The core was split and logged in the field and and Ontario lobes of the Laurentide Ice Sheet to the north returned to the laboratory where it was rewetted to obtain and south, respectively (Chapman and Putnam, 1966; maximum contrast of the laminations for photography and White, 1975; Duckworth, 1979; Sharpe et al., 1994b). As the subsampled for sedimentary texture and carbon content. ice withdrew from the moraine between about 13.5 - 12.5 ka BP a complex geography of ice-dammed, ice-contact, and Seven sedimentary facies can be distinguished in the proglacial lakes formed between the ice lobes and the Nia- core (Table I). The diamictons (facies 3 and 5) are thought gara Escarpment to the west (Chapman, 1985). Mapping of to be the Newmarket drift overlying earlier non-glacial or gla- these lakes in detail is impossible because much of their cilacustrine deposits (facies 1 and 2), and ascribed to a shorelines was along ice fronts and so they have not been near-ice or ice-contact environment during the Port Bruce preserved; our understanding of their paleogeography Stade. Facies 4 between the diamicton beds represents an comes mainly from the deep-water glacilacustrine deposits ice-proximal or subglacial glacifluvial and glacilacustrine throughout the moraine. This paper reports on this glaciola- environment of the same period. The thick deposit of mas- custine sedimentary environment from an assessment of a sive, layered and cross-bedded sands (facies 6) originated core recovered from the ORM.
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