The pattern of glaciation on the Avalon Peninsula of Newfoundland

Abstract

The pattern of glaciation on the Avalon Peninsula has been established through study of geomorphic features, striations, and erratic provenance. Three phases in a continuum of glaciation are recognized. The initial phase involved the expansion of ice from several centres. Ice thickness and extent reached a maximum during the subsequent Phase 2 event, correlated with the Late Wisconsinan. Lowered sea level permitted the development of the St. Mary's Bay ice centre. Ice from the Newfoundland mainland coalesced with Avalon Peninsula ice inPlacentia Bay, on the Isthmus, and in Trinity Bay. Rising sea level, triggered by the retreat of Laurentide ice in Labrador, resulted in destabilization of the St. Mary's Bay ice cap, marking Phase 3. Final deglaciation of theAvalon Peninsula began before 10,100 ± 250 BP. The Avalon Peninsula ice caps were controlled by regional and hemispheric events, and by the response of the Lauren- tide glaciers.L'histoire de la glaciation de la presqu'île d'Avalon a été établie à partir de l'étude des caractéristiques géomorphologiques, des stries et de la provenance des blocs erratiques. On distingue trois phases dans un continuum de glaciation. Pendant la première phase, il y a eu accumulation et dispersion de la glace à partir de plusieurs centres. Au cours de la deuxième période, qui correspond au Wisconsinien supérieur, les glaciers ont atteint un maximum en étendue et en épaisseur. Le niveau marin abaissé a permis la formation d'un centre glaciaire à l'emplacement de la baie St. Mary. Le glacier en provenance de la partie continentale de Terre-Neuve a fusionné avec celui de la presqu'île d'Avalon dans la baie de Plaisance, sur l'isthme et dans la baie de la Trinité. La troisième phase, caractérisée par la remontée du niveau marin et déclenchée par le recul de l'Inlandsis laurentidien au Labrador, a déséquilibré la calotte glaciaire de St. Mary. La déglaciation finale de la presqu'île d'Avalon a commencé avant 10 100 ± 250 BP. L'évolution des calottes glaciaires de la presqu'île d'Avalon a été déterminée par des événements régionaux et hémisphériques et par la réponse des glaciers laurentidiens.Das Schema der Vereisung auf der Avalon-Halbinsel wurde mittels des Studiums der geomorphologischen Merkmale, der Schrammen und der Herkunft der erratischen Blöcke nachgezeichnet. In der Anfangsphase dehnte sich das Eis ausgehend von mehreren Zentren aus. Das Eis erreichte ein Maximum an Dicke und Ausdehnung in der folgenden 2. Phase, die dem späten Wisconsin entspricht. Der niedrigere Meeresspiegel ermöglichte die Entwicklung des Eiszentrums der St. Mary's -Bai. Das Eis vom Festland Neufundlands vereinigte sich mit dem Eis der Avalon-Halbinsel in der Placentia-Bai, auf dem Isthmus und in der Trinity-Bai. In Phase 3 führte ein ansteigender Meeresspiegel, ausgelöst durch den Rückzug des laurentischen Eises in Labrador, zur Destabilisierung der Eiskappe der St. Mary's-Bai. Die endgültige Enteisung der Avalon-Halbinsel begann vor 10 100 ± 250 v.u.Z

The subglacial imprint of the last Newfoundland Ice Sheet, Canada.

“…The LIS formed the central parts of the North American Ice Sheet Complex and during its maximum extent ( 27 14 C ka BP and 24 14 C ka BP; Dyke et al, 2002) coalesced with the smaller regional ice sheets including the NIS with the convergence zone being along Newfoundland's northern and western margins (Figure 1; Dyke, 2004;Grant, 1989Grant, , 1994Kleman et al, 2010;Stokes, Tarasov, & Dyke, 2012). A southward ice flow from Labrador crossed the Strait of Belle Isle onto northern parts of the Great Northern Peninsula, while further to the south, the LIS advanced as far as the Long Range Mountains before being deflected into the Gulf of St. Lawrence (Brookes, 1982;Catto, 1998;Grant, 1977Grant, , 1989Putt, Bell, Batterson, & Smith, 2010;Shaw et al, 2006;Tucker, 1974). At this time, the NIS is understood to have maintained a complex of local ice caps with ice cover having advanced to the continental shelf (Dyke et al, 2002;Shaw, 2003Shaw, , 2006Shaw et al, 2006).…”

Topographically-controlled Deglacial History of the Humber River Basin, Western Newfoundland

“…A strong relationship is evident between striation observations and bedrock type, with finer grained rock types showing striated surfaces more commonly than coarse rock types. Striations on limestone surfaces weather quickly following removal of Quaternary sediment, as in other areas of boreal Newfoundland (Catto, 1998a).…”

“…Relatively low topographic divides influence ice flow from individual ice caps throughout Newfoundland (e.g., Grant, 1974;Catto, 1998a). The northwestern part of Birchy Ridge shows striations from a relatively early eastward flow that may be a southern extension of the eastward flow deduced in the upper Humber River.…”

“…The exact location of The Topsails dispersal centre is uncertain, and may have migrated during the Late Wisconsinan, similar to other parts of Newfoundland and Labrador (e.g., Klassen and Thompson, 1993;Catto, 1998a (Whalen and Currie, 1988) clasts across the Humber River basin.…”

“…Throughout Newfoundland, the hypothesis of multiple glacial ice caps was established through numerous investigations (e.g., Grant, 1974Grant, , 1977Grant, , 1989aBrookes, 1982;Catto, 1998a). Assessment of the directions of ice movement necessary to support the hypothesis requires careful examination of all glacigenic depositional and erosional features.…”