Deglaciation chronology and revegetation in northwestern Ontario

1985 ◽  
Vol 22 (6) ◽  
pp. 850-871 ◽  
Author(s):  
Svante Björck
Keyword(s):  
Black Spruce ◽  
Lake Superior ◽  
The South ◽  
Migration Routes ◽  
White Pine ◽  
Cool Period ◽  
Radiocarbon Dates ◽  
Northwestern Ontario ◽  
History Of ◽  
Ice Retreat

Along a 420 km transect in northwestern Ontario, Canada, sediments from four lakes were analyzed with respect to lithology, pollen, and macrofossils. Radiocarbon dates show that the region was deglaciated between ca. 11 500 and 8000 years BP, and periods of both rapid ice retreat and readvance influenced the history of Glacial Lake Agassiz. In the south the ice sheet was succeeded by a lengthy interval of park–tundra with stands of spruce, ash, and elm. The ash and elm seem to have disappeared during a suggested cool period (11 100–10 200 years BP). Farther north the park–tundra phase lasted not more than 50–100 years after ca. 10 200 years BP before boreal trees dominated. The climatic change around 10 200 years BP permitted the very rapid migration of spruce, larch, birch, and jack or red pine into northwestern Ontario from northern Minnesota. The migration routes for Pinus strobus (white pine), Alnus rugosa, and A. crispa were divided, however: one from the south (south of Lake Superior) and one from the east-southeast (north of Lake Superior). White pine reached its maximum distribution 6500–6000 years BP, when the limit was probably 150–200 km north of today's. The composition of the boreal forest during the altithermal was only slightly changed, but the influx of presumed prairie pollen reached a peak ca. 8000–7000 years BP. Since then Picea mariana (black spruce) gradually became the dominating tree species.

Late Quaternary Glacial History of the South Orkney Plateau, Antarctica

1990 ◽  
Vol 33 (3) ◽  
pp. 265-275 ◽  
Author(s):  
Margaret J. Herron ◽  
John B. Anderson
Keyword(s):  
Late Quaternary ◽  
The South ◽  
Ice Shelf ◽  
Radiocarbon Dates ◽  
Orkney Islands ◽  
Ice Cap ◽  
History Of ◽  
Seismic Records ◽  
Ice Conditions ◽  
History Of The South

AbstractPiston cores from the South Orkney Plateau penetrated overcompacted diamictons in water depths of up to 250 m. Detailed textural and petrological analyses of these diamictons indicate that they are basal tills. Seismic records from the plateau show a widespread surface of glacial erosion and provide additional evidence of an ice cap grounded to a depth of 250 m. Piston cores from the slope of the plateau penetrated diatomaceous muds resting directly on poorly sorted muds with very little to no biogenic material. The ice-rafted debris in these glacial-marine sediments is composed almost exclusively of material derived from the South Orkney Islands. This implies deposition beneath an ice shelf as opposed to iceberg rafting. In contrast, diatomaceous muds contain relatively abundant exotic iceberg-rafted material and reflect a glacial-maritime setting similar to that of today. The sharp contact separating diatomaceous surface sediments from basal tills and sub-ice shelf deposits indicates that the ice cap and ice shelf retreated from the plateau rapidly. Radiocarbon dates for diatomaceous muds from a glacial trough on the plateau indicate that the ice cap and ice shelf retreated from the plateau prior to 6000 to 7000 years ago. The homogeneity of surficial diatomaceous sediments suggests that sea ice conditions over the plateau have not changed radically since that time.

Feeding Sites of Aphids of the Genus Cinara Curtis (Homoptera: Aphididae) in Northwestern Ontario

1959 ◽  
Vol 91 (10) ◽  
pp. 670-671 ◽  
Author(s):  
G. A. Bradley
Keyword(s):  
Black Spruce ◽  
Jack Pine ◽  
Red Pine ◽  
Balsam Fir ◽  
White Pine ◽  
White Cedar ◽  
Feeding Sites ◽  
Red Lake ◽  
Northwestern Ontario ◽  
Common Juniper

While working at Cedar Lake in Northwestern Ontario in the summers of 1957 and 1958 the author was able to observe the feeding sites of various species of Cinara. Most of the observations were made within an area of a few square miles on either side of Highway 105, between Red Lake Road and Ear Falls, Ontario. This area is fairly typical of the Laurentian Shield, with numerous lakes, rocky ridges, sandy patches, and small bogs. The principal coniferous trees in this locality are black spruce, jack pine, and balsam fir. White spruce, white cedar, white pine, red pine, and common juniper are also present.

GLACIAL FEATURES OF THE NORTH-CENTRAL LAKE SUPERIOR REGION, ONTARIO

1967 ◽  
Vol 4 (3) ◽  
pp. 515-528 ◽  
Author(s):  
S. C. Zoltai
Keyword(s):  
Lake Superior ◽  
Field Work ◽  
Aerial Photographs ◽  
Northern Ontario ◽  
Radiocarbon Dates ◽  
North Central ◽  
The North ◽  
Glacier Ice ◽  
History Of ◽  
Differential Uplift

The surficial glacial features and glacial events of a 13 000 square mile area in northern Ontario are described, based on field work and study of aerial photographs. Ice-laid and glaciolacustrine materials suggest a complex history of stationary ice fronts and glacial lakes during deglaciation. Lakes in the Lake Nipigon and Lake Superior basins inundated large areas. Post-Minong lake stages in the Superior basin intruded far to the north, dammed by ice at the largest moraine, the Nakina. The northern part of this lake was later separated from the post-Minong lake by differential uplift and was named Lake Nakina. After the withdrawal of the ice, Glacial Lake Barlow–Ojibway occupied the northeastern part of the area, and much of it was later overridden by the last glacial readvance. Stratigraphic correlations with radiocarbon dates suggest that the Nakina moraine was built some 9 400 years ago, and that the last glacier ice disappeared before 6 390 years ago.

The Life-History of Pineus pinifoliae (Fitch) (Homoptera: Phylloxeridae) and its Effect on White Pine

1950 ◽  
Vol 82 (6) ◽  
pp. 117-123 ◽  
Author(s):  
R. E. Balch ◽  
G. R. Underwood
Keyword(s):  
Life History ◽  
Black Spruce ◽  
Life Cycles ◽  
White Pine ◽  
Complex Life Cycles ◽  
Return Migrants ◽  
Winged Form ◽  
Typical Species ◽  
History Of

Pineus pinifoliae (Fitch) belongs to the Adelginae, a group characterized by unusually complex life-cycles. The typical species have at least five distinct forms, one bi-sexual and the others parthenogenetic. They alternate between two coniferous hosts, one of which is always a species of spruce (Picea). Galls are formed on spruce by a modification of the growth of the new shoot.The life-history of P. pinifoliae is only partially known. Patch has reported on observations in Maine which showed that the gall-making form flew from “black spruce” to the needles of white pine and that its offspring settled on the new shoots. She also described a morphologically similar winged form which developed on white-pine shoots and which she believed to be the return migrants. Annand made similar observations in Oregon and gave careful descriptions of three forms: the fundatrix, the gallicola migrans, and the exulis.

Radiocarbon Dates on Deglaciation, Cordillera Central, Northern Peruvian Andes

1989 ◽  
Vol 32 (1) ◽  
pp. 111-113 ◽  
Author(s):  
P.W. Birkeland ◽  
D.T. Rodbell ◽  
S.K. Short
Keyword(s):  
Late Glacial ◽  
Glacial Maximum ◽  
Radiocarbon Dates ◽  
Cordillera Central ◽  
Peruvian Andes ◽  
Relative Dating ◽  
History Of ◽  
Ice Retreat ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractThree radiocarbon dates along with relative-dating criteria place limits on the deglaciation history of Manachaque Valley, Cordillera Central. Ice retreated from the late-glacial maximum by at least 12,100 yr B.P. During ice retreat numerous moraines were deposited throughout the valley. Glacier cover was reduced to about half that of the last glacial maximum by at least 9700 yr B.P. and to less than a tenth by at least 6450 yr B.P. Because all dates are minimum, the dates and field data are consistent with little or no ice remaining by early Holocene. No unambiguous Younger Dryas moraines are present.

scholarly journals Late-Pleistocene and Holocene palynology in southeastern Québec

2010 ◽  
Vol 31 (1-2) ◽  
pp. 139-149 ◽  
Author(s):  
R. J. Mott
Keyword(s):  
Late Pleistocene ◽  
Balsam Fir ◽  
Appalachian Region ◽  
White Pine ◽  
Deciduous Species ◽  
Radiocarbon Dates ◽  
Watershed Area ◽  
Closed Forest ◽  
History Of ◽  
Forest Conditions

Several relative and absolute pollen profiles from the Appalachian Region outline the vegetational history of the region. The earliest reliable date of 11,200 radiocarbon years BP, from the watershed area of the Mégantic Hills on the Québec-Maine border, dates the spruce pollen maximum, indicative of spruce woodland conditions. A second site in the same area shows tundra conditions existed prior to this time, but no radiocarbon dates are available to indicate the length of time these conditions persisted. About 10,000 radiocarbon years BP or less, the character of the vegetation changed and closed forest conditions prevailed. Spruce was still present, but balsam fir and birch increased and other deciduous species appeared. The continued increase in thermophilous deciduous species and hemlock and white pine during early- and mid-Holocene resulted in forests in which these taxa were more prominent than at present. An increase in spruce and decline in thermophilous taxa in the last few millenia produced the extant forests types.

scholarly journals A Standard Method for Evaluating Radiocarbon Dates of Local Deglaciation: Application to the Deglaciation History of Southern Labrador and Adjacent Québec

2007 ◽  
Vol 39 (2) ◽  
pp. 163-182 ◽  
Author(s):  
George A. King
Keyword(s):  
Lake Sediments ◽  
Standard Method ◽  
Glacial Geology ◽  
Southeastern Part ◽  
Radiocarbon Dates ◽  
North Shore ◽  
Peat Deposits ◽  
Accuracy And Precision ◽  
History Of ◽  
Ice Retreat

ABSTRACT Sixty-two radiocarbon dates of marine shells, basal lake sediments, and basal peat deposits from the southeastern part of the Labrador-Ungava Peninsula, Canada, were evaluated for their accuracy and precision in estimating local deglaciation time. A procedure for the consistent evaluation of basal dates of lake sediments was developed after consideration of the problems with dating early-postglacial sediments. Of the 62 dates, 42 were selected to construct the regional déglaciation chronology, interpreted in the context of the glacial geology of the area. Late Wisconsin ice stretched to or beyond the present-day coastline throughout the study area, except in southeastern Labrador where the extreme southeastern coast was probably ice-free during Late Wisconsin time. Déglaciation began in southeastern Labrador by 13.OK. It proceeded slowly at first, and between 9.7K and 10.5K the retreating ice formed the Paradise Moraine, which parallels the southeastern Labrador coastline. In contrast, the coast at Sept-îles was not ice-free until about 9.4K. Shortly thereafter the extensive Québec North Shore Moraine System developed, although its precise age is uncertain. The position of the ice margin at 8.0K is uncertain, but may still have been near the Québec North Shore Moraine System. After 8.0K ice retreat was rapid, although extensive ice persisted at 6.5K in western Labrador and adjacent Québec. Final wastage of ice occurred in two localities in the center of the Labrador-Ungava Peninsula just after 6.OK. The precision of the well-dated glacial isochrones is estimated to be about ± 23 km.

scholarly journals Anomalous Radiocarbon Dates from Easter Island

Radiocarbon ◽  
2004 ◽  
Vol 46 (1) ◽  
pp. 395-405 ◽  
Author(s):  
Kevin Butler ◽  
Christine A Prior ◽  
John R Flenley
Keyword(s):  
Sample Selection ◽  
South Pacific ◽  
Easter Island ◽  
The South ◽  
Depositional History ◽  
Radiocarbon Dates ◽  
Organic Components ◽  
Scirpus Californicus ◽  
History Of ◽  
Age Determinations

The largest volcanic crater on Easter Island in the South Pacific contains a lake 1 km in diameter with large floating mats of vegetation, mainly Scirpus californicus. A core taken through a mat near the center produced anomalous dates, with older dates above younger ones. The possibility that the mat had become inverted was considered, but palynological evidence refutes this idea because it shows a progressive upward decline of forest pollen, which is well known from other swamp cores on the island. A new series of radiocarbon dates made directly on pollen concentrates was obtained. These dates also produced inconsistencies, particularly when pollen concentrate ages were compared with 14C ages on plant fragments from the same depth. This series of 14C ages seems to indicate that both old and young organic components in the sediment are deposited contiguously and that the depositional history of these cores is more complex than previously known. Previous age determinations on bulk sediments from Easter Island, which also show anomalous dates, may be too simplistic. This paper provides a warning to other researchers dating sediments from Easter Island. We suggest that sample selection and dating procedures be carefully considered for these sediments.

The Deglaciation History of the Lake Superior Region and its Climatic Implications

1974 ◽  
Vol 4 (3) ◽  
pp. 316-339 ◽  
Author(s):  
Matti Saarnisto
Keyword(s):  
Lake Superior ◽  
Cold Climate ◽  
Northern Ontario ◽  
The North ◽  
Lake Algonquin ◽  
Western Lake ◽  
History Of ◽  
Ice Retreat ◽  
Main Lake ◽  
High Level

A zone of synchronous end moraines has been recognized in the Lake Superior region across northern Ontario and Michigan. The moraines were formed between 11,000 and 10,100 y.a. as cold climate resulted in successive halts in the general ice retreat. The cold climate is also indicated by the presence of tundra near Lake Superior until about 10,000 y.a. This episode is here referred to as the Algonquin Stadial. It was preceded and followed by rapid deglaciation. The Algonquin Stadial is comparable in age with the Younger Dryas Stadial of Europe, and indicates a reversal in the continuous trend toward a warmer climate during Late-Wisconsin (an) time. The apparent conflict between the present result (based on geologic evidence) and earlier pollen stratigraphical studies with no reversal is discussed.Glacial Lake Duluth formed in the western Lake Superior basin before 11,000 BP, followed by a series of Post-Duluth lakes between approximately 11,000 and over 10,100 BP. The Main Lake Algonquin stage in the Huron and Michigan basins terminated approximately 11,000 BP. The subsequent high-level post-Main Algonquin lakes, which were contemporaneous with the Post-Duluth lakes, existed in the southeastern Lake Superior basin. When the ice margin was along the north shore 9500 BP Lake Minong occupied the whole Lake Superior basin. By 9000 BP the ice had retreated north of Lake Superior-Hudson Bay divide.

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