THE GLACIAL PERIOD IN NORTH AMERICA

Author(s):  
Charles Lyell
Keyword(s):  
1992 ◽  
Vol 70 (11) ◽  
pp. 2247-2259 ◽  
Author(s):  
Nicholas E. Mandrak ◽  
E. J. Crossman

The present-day distributions of 117 native freshwater fishes in Ontario have been shaped by processes active following the Wisconsinan glacial period, 80 000–10 000 years before present. During this glacial period, these species survived in unglaciated réfugia. To understand the processes that resulted in the recolonization of Ontario by fishes following the last glacial period, the refugial areas occupied by each species were determined using a refugial index, and glacial water bodies used as dispersal routes were identified. The refugial origins of the Ontario populations of 91 species were resolved. Seventy-two species resided in the Mississippian refugium, 13 species in the Atlantic Coastal refugium, 4 species in dual Atlantic Coastal – Mississippian refugia, 1 species in a Missourian refugium, and 1 species in Atlantic Coastal, Mississippian, and Missourian refugia. These conclusions differed significantly from those of other studies. Five general patterns were identified from the distributions of 104 species. In addition, there are 13 species that do not fit any of the general patterns. Most species with similar distributions in Ontario shared the same refugia and dispersal routes in eastern North America, therefore it is hypothesized that historical processes were important in shaping the present-day distributions of Ontario freshwater fishes.


1944 ◽  
Vol 187 (6) ◽  
pp. 121-121
Author(s):  
William Harcourt-Bath
Keyword(s):  

ARCTIC ◽  
1957 ◽  
Vol 10 (2) ◽  
pp. 66 ◽  
Author(s):  
J.D. Ives

Considers role of these mountains in glaciation of Labrador-Ungava, assessing particularly events in late-Wisconsin times with respect to final disappearance of both continental and local ice masses. Conflicting theories are discussed, and evidence presented, based on physiography and findings from summer 1956 field work, including unmistakable erratics on summits at 4,000-5,000 ft. The highest summits were completely submerged by eastward moving continental ice during the Wisconsin glaciation; local glaciers never reached significant dimensions; rapid melting in situ of thick masses of ice occurred during the final Wisconsin stages. Two or three separate glacial periods are recognized from the morphology of the area. Instantaneous glaciation of a large area of the Labrador-Ungava Plateau probably initiated a continental ice sheet in northeastern North America at the onset of each glacial period. Also pub. in International Union of Geodesy and Geophysics, Association of Scientific Hydrology, 11th assembly report of proceedings 1958, v. 4, p. 372-86.


1883 ◽  
Vol 10 (4) ◽  
pp. 169-171
Author(s):  
John Brysen

Having resided for some years past on Long Island, the terminal moraine of the Great American continental glacier, and having given considerable attention to the drift phenomena, I am convinced that no oscillation of the continent has taken place subsequent to the Glacial period; and that the river kames, with their assorted gravel, etc., can be accounted for, without resorting to any such doubtful interpretations. I am aware that the presence of shells in the Boulder-clay argues in its favour; but that shells become mixed with the drift while the glacier is in motion is evident from what Prof. Geikie saw in Scandinavia. I will now try in a brief way to give your readers the result of my observations; and, though the sketch may be somewhat crude and imperfect, it may serve to throw a little light on this difficult problem.


1923 ◽  
Vol 13 (3) ◽  
pp. 489
Author(s):  
Frank Leverett ◽  
F. C. Baker
Keyword(s):  

ARCTIC ◽  
1957 ◽  
Vol 10 (4) ◽  
pp. 243
Author(s):  
J.D. Ives

... The central area of study lay athwart the Labrador-Quebec boundary on the watershed between Nakvak Brook, which drains into Saglek Fiord, and the Koroksoak (Korok) River, which flows westwards into Ungava Bay. ... Attention was concentrated on an extensive system of lateral moraines and kame terraces which slope eastwards from the watershed towards the head of Saglek Fiord. Similar systems were examined in the through-troughs to the south. The whole complex represents the late-Pleistocene limits of trunk glaciers flowing through the mountains towards the east and supplied by an ice cap of continental proportions west of the height of land. At this stage the higher summits stood as nunataks well above the level of the ice, and an extensive series of ice-dammed lakes was held against the western slopes of the highland finding outlets over ice-free cols into the Atlantic. Detailed studies in the watershed area provide a chronology of the final emergence of the area from the last ice sheet, and the draining of the ice-dammed lakes. A final stage was represented by a mass of ice in the lower valley of the Koroksoak which dammed a lake to the level of the col, at 1,050 feet, whence it drained into Nakvak Brook and ultimately into the Atlantic. Glacial erratics, found on summits up to 4,000 feet above sea level, corroborate the conclusions of the previous summer's work suggesting that at some stage the highest summits were inundated by ice flowing from the west. The data compiled from the two summers' work prompt the conclusion that during late-Pleistocene times the Torngat Mountains were influenced by two distinct glaciations, separated by an interglacial period of considerable intensity. The final glaciation, during which large areas remained ice-free, is tentatively correlated with the "classical" Wisconsin of central North America whereas the date of the preceding glacial period is uncertain. It may be the equivalent of the Illinoian Glaciation, or even be of post-Sangamon age, and in this case be comparable with a cold phase tentatively identified in central North America, which is older than the "classical" Wisconsin Glaciation, and is separated from the latter by a warmer period. Reconnaissance from the air during flights along the Labrador coast and some distance inland suggests that these general conclusions might well be applicable to the entire coastal zone of Labrador. ...


1890 ◽  
Vol 7 (11) ◽  
pp. 492-497
Author(s):  
Warren Upham

The article by Prof. J. W. Spencer in the last May number of this Magazine brings together many evidences of high continental elevation of North America preceding the Pleistocene or Glacial period. Though Professor Spencer has not proceeded to interpret these observations as revealing in continental elevation the probable cause of the severely cold climate and accumulation of ice-sheets during the Glacial period, I believe that this is a legitimate conclusion, and that it strongly re-enforces the arguments long ago advanced by Lyell and Dana, and recently emphasized anew by Wallace.


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