scholarly journals Paleoecology of Organic Deposits of Probable Last Interglacial Age in Northern Ontario

2007 ◽  
Vol 44 (3) ◽  
pp. 309-318 ◽  
Author(s):  
Robert J. Mott ◽  
Ronald N. W. DiLabio
Keyword(s):  
Deep Sea ◽  
Hudson Bay ◽  
Last Interglacial ◽  
Northern Ontario ◽  
Hudson Bay Lowlands ◽  
Organic Sediment ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
Organic Deposits ◽  
River Valleys

ABSTRACT Nonglacial deposits in northern Ontario that may date to the last interglacial interval are well known from the Hudson Bay Lowlands where they have been described in sections along several river valleys. Soil horizons, peat beds and other organic sediment sequences comprise the Missinaibi Formation of the Moose River Basin studied for pollen and macrofossils. Results suggest that the climate was as warm or warmer than present, and spruce woodlands prevailed among broad expanses of bog and fen. The Beaver River peat records conditions similar to the present in the Fort Severn area with open spruce woodlands dispersed in peatlands. South of the Lowlands in the Timmins area, a widespread organic-silt horizon termed the Owl Creek beds is stratigraphically equivalent to the Missinaibi Formation. The waning phase of a warm interval is represented, with early climate possibly similar to the present and the later climate much cooler. Correlation of the Missinaibi Formation with substage 5e of the deep-sea oxygen isotope record is corroborated by amino acid results on marine shells from some associated units. Analysis of shells from beneath the Beaver River peat bed indicate that this interval may be considerably younger, possibly substage 5c or, more likely, 5a. The Owl Creek beds may relate to sub-stage 5e, or to one of the younger intervals, 5c or 5a.

scholarly journals Pre-Late Wisconsinan Paleoenvironments in Atlantic Canada

2007 ◽  
Vol 39 (3) ◽  
pp. 239-254 ◽  
Author(s):  
Robert J. Mott ◽  
Douglas R. Grant
Keyword(s):  
Deep Sea ◽  
Coniferous Forests ◽  
Atlantic Canada ◽  
White Pine ◽  
Previous Cycle ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
Late Wisconsinan ◽  
Organic Deposits ◽  
Palynological Records

ABSTRACT Numerous Quaternary organic deposits of various lithologies beneath one or more till units of Wisconsinan age have been discovered in boreholes and exposures in coastal bluffs, quarries and river banks at widespread localities throughout Atlantic Canada. Ongoing palynological and macro-fossil studies, still in a preliminary stage at many sites, reveal a variety of environments from forests dominated by thermophilous hardwood genera and white pine, to mixed temperate hardwood and conifer forests, to boreal coniferous forests of spruce and balsam fir, and forest tundra and tundra communities characterized by spruce, shrubs and herbs. Lithologie and pollen stratigraphie relationships and radiocarbon, amino acid and Thorium/Uranium dating allow a tentative assignment to the Sangamonian Stage and possibly to Early and Middle Wisconsinan time. Three intervals of organic accumulation are apparent: an early interval, when climate became warmer than the present; a second interval, when climate was similar to the present; and a third interval, with cooler climate. The latter interval is characterized by at least three climatic cycles, each one cooler than the previous cycle. Tentative correlations with the deep-sea oxygen isotope record and continental palynological records are presented.

scholarly journals Sangamonian Forest History and Climate in Atlantic Canada

2007 ◽  
Vol 44 (3) ◽  
pp. 257-270 ◽  
Author(s):  
Robert J. Mott
Keyword(s):  
Atlantic Canada ◽  
Last Interglacial ◽  
Cape Breton Island ◽  
Green Point ◽  
Sequence Of Events ◽  
Cape Breton ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
Climatic Optimum ◽  
Organic Deposits

ABSTRACT Seven of the more than twenty five buried organic deposits in Atlantic Canada assigned to pre-Wisconsinan non-glacial intervals possibly relate to the climatic optimum of the Sangamon Interglaciation, that is substage 5e of the deep-sea oxygen isotope record. These sites are East Bay and Green Point on Cape Breton Island. Addington Forks and East Milford in mainland Nova Scotia. Le Bassin and Portage-du-Cap on the Iles de la Madeleine, Québec, and Woody Cove, Newfoundland. Except for Woody Cove, none of the sites records a complete climatic cycle, and the sequence of events must be pieced together from their disparate records. The spectra, characterized by significant amounts of thermophilous taxa that are not as abundant or present in the region today, are similar in general to Holocene spectra at sites immediately south of the lower Great Lakes. Comparison of the fossil spectra from five sites with modern surface spectra from eastern North America yields modern analogs which, if valid, indicate that the climate in Atlantic Canada during the climatic optimum of the last interglacial interval was more continental in character and considerably warmer than present.

Constraining the age of the last interglacial–glacial transition in the Hudson Bay lowlands (Canada) using U–Th dating of buried wood

2012 ◽  
Vol 7 ◽  
pp. 37-47 ◽  
Author(s):  
G. Allard ◽  
M. Roy ◽  
B. Ghaleb ◽  
P.J.H. Richard ◽  
A.C. Larouche ◽  
...  
Keyword(s):  
Hudson Bay ◽  
Last Interglacial ◽  
Hudson Bay Lowlands

Speleothems, Travertines, and Paleoclimates

1983 ◽  
Vol 20 (1) ◽  
pp. 1-29 ◽  
Author(s):  
G. J. Hennig ◽  
R. Grün ◽  
K. Brunnacker
Keyword(s):  
Oxygen Isotope ◽  
Deep Sea ◽  
Clear Relationship ◽  
Sufficient Data ◽  
Geographic Position ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
Age Range ◽  
Stimulation Of ◽  
Frequency Curves

AbstractAge data for about 660 speleothems and about 140 spring-deposited travertines were collected, including many unpublished results. These data were plotted as histograms and also as error-weighted frequency curves on a 350,000-yr scale. These plots clearly show periods of increased speleothem/travertine growth as well as times of cessation. The periods of most frequent speleothem growth were between approximately 130,000 and 90,000 yr ago and since about 15,000 yr ago. Such periods before 150,000 yr ago, however, cannot be yet recognized because of a lack of sufficient data and the associated uncertainties of dates in this age range. A comparison with the oxygen-isotope record of deep-sea core V28–:238 shows a clear relationship, indicating that terrestrial calcite formation is controlled by paleoclimatic fluctuations. The evident climatic stimulation of Quaternary calcite formation is readily explained geochemically and is substantiated by the obvious difference in speleothem/travertine growth as a function of geographic position.

Eemian Climatic and Hydrographical Instability on a Marine Shelf in Northern Denmark

1997 ◽  
Vol 47 (2) ◽  
pp. 218-234 ◽  
Author(s):  
Marit-Solveig Seidenkrantz ◽  
Karen Luise Knudsen
Keyword(s):  
Ocean Circulation ◽  
Atlantic Water ◽  
Water Masses ◽  
Last Interglacial ◽  
Large Shift ◽  
The North ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
First Millennium ◽  
Holocene Record

Benthic foraminifera and stable isotope data from the last interglaciation (Eemian, substage 5e) from a borehole at Skagen, Denmark, provide evidence for major environmental and hydrographic changes during this period. During the first millennium of the Eemian, water masses covering northern Denmark became gradually warmer. Temperate conditions prevailed during most of the interglaciation, but these were interrupted by two periods with decreased water temperatures. The first cooling (Event S-1) was not very distinct at Skagen, but the second (Event S-2), seen in both the foraminiferal and oxygen isotope record, represents a large shift to subarctic conditions. Carbon isotopes indicate a change in ocean circulation during both events. No comparable climate variations are seen within the Holocene record at the site. The final cooling of the water masses associated with the substage 5e/5d boundary occurred within a few hundred years. These last interglacial climatic changes were probably caused by variations in strength and/or position of the North Atlantic Drift, possibly as a result of varying vigor of the Atlantic conveyor. In addition, minor variations in the fossil assemblages also indicate fluctuations in the inflow of Atlantic water to the Skagerrak–Kattegat area during the warm intervals of substage 5e.

scholarly journals Hydrological instability during the Last Interglacial in central Asia: a new diatom oxygen isotope record from Lake Baikal

2013 ◽  
Vol 66 ◽  
pp. 45-54 ◽  
Author(s):  
Anson W. Mackay ◽  
George E.A. Swann ◽  
Nathalie Fagel ◽  
Susanne Fietz ◽  
Melanie J. Leng ◽  
...  
Keyword(s):  
Central Asia ◽  
Oxygen Isotope ◽  
Lake Baikal ◽  
Last Interglacial ◽  
Oxygen Isotope Record ◽  
Isotope Record

AN AUTOMATIC LEAST‐SQUARES MULTIMODEL METHOD FOR MAGNETIC INTERPRETATION

Geophysics ◽  
1973 ◽  
Vol 38 (2) ◽  
pp. 349-358 ◽  
Author(s):  
Peter H. McGrath ◽  
Peter J. Hood
Keyword(s):  
Least Squares ◽  
Magnetic Anomalies ◽  
Magnetic Data ◽  
Model Parameters ◽  
Hudson Bay ◽  
Northern Ontario ◽  
Magnetic Interpretation ◽  
Hudson Bay Lowlands ◽  
Sverdrup Basin ◽  
Best Fit

The magnetic anomalies caused by such diverse model shapes as the finite strike length thick dike, the vertical prism, thes loping step, the parallelepiped body, etc., may be obtained through an appropriate numerical integration of the expression for the magnetic effect produced by a finite thin plate. Using models generated in this manner, an automatic computer method has been developed at the Geological Survey of Canada for the interpretation of magnetic data. Because the magnetic anomalies produced by the various model shapes are nonlinear in parameters of shape and position, it is necessary to use an iterative procedure to obtain the values for the various model parameters which yield a least‐squares best‐fit anomaly curve to a set of discrete observed data. The interpretation method described in this paper uses the Powell algorithm for this purpose. The procedure can sometimes be made more efficient using a Marquardt modification to the Powell algorithm. Examples of the use of the method are presented for an elongated anomaly in the Moose River basin of the Hudson Bay lowlands in northern Ontario, and for an areally large elliptical anomaly in the Sverdrup basin of the Canadian Arctic Islands.

Middle Pleistocene age of the Nome River glaciation, northwestern Alaska

1991 ◽  
Vol 36 (3) ◽  
pp. 277-293 ◽  
Author(s):  
Darrell S. Kaufman ◽  
Robert C. Walter ◽  
Julie Brigham-Grette ◽  
David M. Hopkins
Keyword(s):  
Middle Pleistocene ◽  
Laser Fusion ◽  
Basaltic Lava ◽  
Last Interglacial ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
Order Of Magnitude ◽  
Nearshore Sediments ◽  
The Mean ◽  
Basaltic Lava Flow

AbstractDuring the middle Pleistocene Nome River glaciation of northwestern Alaska, glaciers covered an area an order of magnitude more extensive than during any subsequent glacial intervals. The age of the Nome River glaciation is constrained by laser-fusion 40Ar/39Ar analyses of basaltic lava that overlies Nome River drift at Minnie Creek, central Seward Peninsula, that average 470,000 ± 190,000 yr (±1σ). Milligram-size subsamples of the lava were dated to identify and eliminate extraneous 40Ar enrichments that rendered the mean of conventional K-Ar dates on larger bulk samples of the same flow too old (700,000 ± 570,000 yr). While the 40Ar/39Ar analyses provide a minimum limiting age for the Nome River glaciation, maximum ages are provided by a provisional K-Ar date on a basaltic lava flow that underlies the Nome River drift at nearby Lave Creek, by paleomagnetic determinations of the drift itself at and near the type locality, and by amino acid epimerization analysis of molluscan fossils from nearshore sediments of the Anvilian marine transgression that underlie Nome River drift on the coastal plain at Nome. Taken together, the new age data indicate that the glaciation took place between 580,000 and 280,000 yr ago. The altitude of the Anvilian deposits suggests that eustatic sea level during the Anvilian transgression rose at least as high as and probably higher than during the last interglacial transgression; by correlation with the marine oxygen-isotope record, the transgression probably dates to stage 11 at 410,000 yr, and the Nome River glaciation is younger still. Analyses of floor altitudes of presumed Nome River cirques indicate that the Nome River regional snowline depression was at least twice that of the maximum late Wisconsin. The cause of the enhanced snowline lowering appears to be related to greater availability of moisture in northwestern Alaska during the middle Pleistocene.

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