Ice Marks in Newfoundland: A History of Ideas

Abstract

This essay traces the evolution of ideas on the origin of features in Newfoundland now ascribed to glaciation, through the period 1822-1981. It identifies "Pre-cognitive," "Drift," and "Glacial" phases, with the last phase divided into seven sub-phases. In the Glacial Phase, debate centred on 1) the relative roles of Labrador ice and ice from the island of Newfoundland, 2) the areal and vertical extent of ice masses, and 3) the number and chronology of glacial episodes. Alexander Murray is credited with first recognizing glaciation in Newfoundland in 1866, and the background to his perspicacity is discussed. The evolution of ideas from the late-nineteenth century to the present is related to improving access, exploration by increasingly widely experienced scientists, the import of concepts from outside the region, the development of chronological tools, and improvements in glaciological theory.Le présent article retrace l'évolution de la pensée quant à l'origine des formes, qu'on sait aujourd'hui glaciaires, à Terre-Neuve, pour la période allant de 1822 à 1981. On y reconnaît trois phases: la phase dite « précognitive », la phase au cours de laquelle on attribuait les formes à l'action des glaces flottantes et, enfin, la phase au cours de laquelle on reconnut l'action des glaciers. Dans la section traitant de cette dernière phase, dont on a dégagé sept étapes, la discussion porte: 1) sur l'influence relative des glaces du Labrador et de Terre-Neuve; 2) sur l'extension régionale et altitudinale des masses glaciaires; 3) sur le nombre de glaciations et leur chronologie. Alexander Murray fut, en 1866, le premier à reconnaître l'action des glaciers à Terre-Neuve. On expose ici son interprétation du phénomène. L'évolution de la pensée, de la fin du XIXe siècle jusqu'à nos jours, tient à une plus grande accessibilité du terrain, à une intensification des explorations par des scientifiques de mieux en mieux préparés, à l'influence d'idées venues de l'extérieur, à la mise au point d'outils permettant d'établir des chronologies et à l'amélioration des théories de glaciologie

Geographic pattern of genetic diversity inPinus resinosa: contact zone between descendants of glacial refugia

“…Thus, while it may be possible to construct other more complicated nonequilibrium processes that are consistent with the data or to invoke various selection models, we focus on this possibility as more parsimonious. Geologists have increasingly emphasized that there were unglaciated areas in the northeast (Grant, WALTER AND EPPERSON-GENETIC DIVERSITY IN PINUS RESINOSA 1977;Ives, 1978;Brookes, 1982). Many ecologists have long been convinced that terrestrial ecosystems persisted there as refugia throughout the Wisconsinian (e.g., Fernald, 1911;Pielou, 1992).…”

“…During the glacial maximum, a series of large islands and extensions of the mainland were exposed due to the reduced level ocean. Some parts of Newfoundland, Gulf of St. Lawrence, and Nova Scotia, as well as then-exposed land that is presently below sea level, was free of all glaciers (e.g., Grant, 1977;Ives, 1978;Brookes, 1982;Josenhans and Lehman, 1999). Studies of fossil flora from that region and time have rarely if ever been done, but the possibility that a red pine refugium existed there should not be discounted.…”

The Middle Wisconsinan History of the Laurentide Ice Sheet

“…The lithologically distinct tills are linked to separate ice flow events and source areas. Although all tills were originally assigned to the Late Wisconsinan, according to the convention of the time (PREST and GRANT, 1969;PREST, 1977), studies on weathering zones (GRANT, 1977;BROOKES, 1982), and growing awareness of a longer time scale in other areas led the principal investigators to position events into a longer time framework. In this newer (and still unproven) context, the tills and striae indicate that ice flow shifted during the course of the Wisconsin glaciation and that local ice caps prevailed during the Middle and Late Wisconsinan {i.e.…”

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).…”