Pleistocene Molluscs from Lake Iroquois Deposits in Ontario

1972 ◽  
Vol 9 (5) ◽  
pp. 589-595 ◽  
Author(s):  
P. F. Karrow ◽  
A. H. Clarke ◽  
H. B. Herrington
Keyword(s):  
Shallow Water ◽  
Glacial Lake ◽  
Freshwater Snails ◽  
Lake Algonquin ◽  
Water Conditions ◽  
Eastern Ontario ◽  
Shallow Water Sediments ◽  
River Mouths

Nearly 30 taxa of Pleistocene freshwater snails and sphaeriids have been found in recent years at eight localities in glacial Lake Iroquois deposits. Older reports of molluscs from Lake Iroquois deposits by Ami (1900) and Coleman (1899, 1933) probably represent confusion with shells from Lake Algonquin and Wisconsinan interstadial deposits at Toronto.Molluscs are most abundant in shallow-water sediments deposited in former lagoons and near former river mouths in Lake Iroquois. A northeastward limit of occurrences near Oshawa, Ontario may reflect the influence of the retreating ice-margin in eastern Ontario 12 000 years ago. Shells have been found occasionally in deposits of lower level, post-Iroquois (but pre-Champlain Sea) lake stages in eastern Ontario. The Lake Iroquois fauna suggests the presence of vegetation both on land and in the water with water conditions at individual sites varying from oligotrophic to eutrophic.

scholarly journals Ice Scours in the Sediments of Glacial Lake Iroquois, Prince Edward County, Eastern Ontario

2007 ◽  
Vol 46 (2) ◽  
pp. 189-194 ◽  
Author(s):  
Robert Gilbert ◽  
Karen J. Handford ◽  
John Shaw
Keyword(s):  
Shallow Water ◽  
Ice Sheet ◽  
Ground Surface ◽  
Laurentide Ice Sheet ◽  
Glacial Lake ◽  
Lake Ice ◽  
Prince Edward County ◽  
Westerly Direction ◽  
Eastern Ontario

ABSTRACT Straight or slightly curved ice scours are found in thin glacilacustrine sediment of eastern Lake Iroquois, especially near the crest of an escarpment in Prince Edward County. They are large (to 3.57 km long and 174 m wide), shallow (about 1 m deep) and oriented in a nearly westerly direction. Irregular ridges of sediment have been pushed up along the sides and at the western end of some scours. Bedrock is near the ground surface, but had little influence on the formation of the scours. Based on their shape, location and pattern, we conclude that the scours were most likely formed in shallow water of the short-lived Sydney phase of Lake Iroquois by lake ice driven by prevailing northeasterly winds from the retreating Laurentide Ice Sheet.

Glacial-Lake Outburst Erosion of the Grand Valley, Michigan, and Impacts on Glacial Lakes in the Lake Michigan Basin

1993 ◽  
Vol 39 (1) ◽  
pp. 36-44 ◽  
Author(s):  
Alan E. Kehew
Keyword(s):  
Lake Level ◽  
Lake Michigan ◽  
Laurentide Ice Sheet ◽  
Glacial Lake ◽  
Michigan Basin ◽  
Lake Agassiz ◽  
Lake Algonquin ◽  
Lake Michigan Lobe ◽  
Possible Cause ◽  
Glacial Lake Algonquin

AbstractGeomorphic and sedimentologic evidence in the Grand Valley, which drained the retreating Saginaw Lobe of the Laurentide Ice Sheet and later acted as a spillway between lakes in the Huron and Erie basins and in the Michigan basin, suggests that at least one drainage event from glacial Lake Saginaw to glacial Lake Chicago was a catastrophic outburst that deeply incised the valley. Analysis of shoreline and outlet geomorphology at the Chicago outlet supports J H Bretz's hypothesis of episodic incision and lake-level change. Shoreline features of each lake level converge to separate outlet sills that decrease in elevation from the oldest to youngest lake phases. This evidence, coupled with the presence of boulder lags and other features consistent with outburst origin, suggests that the outlets were deepened by catastrophic outbursts at least twice. The first incision event is correlated with a linked series of floods that progressed from Huron and Erie basin lakes to glacial Lake Saginaw to glacial Lake Chicago and then to the Mississippi. The second downcutting event occurred after the Two Rivers Advance of the Lake Michigan Lobe. Outbursts from the eastern outlets of glacial Lake Agassiz to glacial Lake Algonquin are a possible cause for this period of downcutting at the Chicago outlets.

scholarly journals Upper Arenig trilobite biostratigraphy and sea-level changes at Lynna River near Volkhov, Russia

2003 ◽  
Vol 50 ◽  
pp. 105-114
Author(s):  
T. Hansen ◽  
A.T. Nielsen
Keyword(s):  
Shallow Water ◽  
Sea Level Rise ◽  
Sea Level ◽  
Abundance Ratio ◽  
Basal Part ◽  
Sea Level Changes ◽  
Faunal Turnover ◽  
Lower Ordovician ◽  
Water Conditions ◽  
Tentative Interpretation

Over 5000 trilobites have been collected from Lower Ordovician rocks exposed at the Lynna River in the Volkhov region, east of St. Petersburg, Russia. Bed-by-bed sampling has been carried out through the upper part of Volkhov Formation (top of Jeltiaki Member and the entire Frizy Member), the Lynna Formation and the basal part of the Obukhovo Formation. This interval, which is 7.5 metres thick, correlates with the upper part of the Arenig Series, and presumably even ranges into the very base of the Llanvirn. A preliminary biostratigraphical investigation of top Jeltiaki Member (BIIβ), Frizy Member (BIIγ) and basal Lynna Formation (BIIIα) reveals a rather continuous faunal turnover lacking sharp boundaries, and the biostratigraphical zonation (BIIβ–BIIIα) is primarily defined by the index trilobite taxa. The trilobite ranges are generally in agreement with the pattern described by Schmidt in 1907. The abundance ratio between Asaphus and the ptychopygids seems to be related to changes in relative sea level with Asaphus preferring the most shallow water conditions. A tentative interpretation of sea-level changes suggests an initial drowning at the base of BIIγ, immediately followed by a lowstand that in turn was succeeded by a moderate sea-level rise and then a significant fall. The last marks the BIIγ/BIIIα boundary. Correlation with sections in Scandinavia suggests that the basal part of BIIγ is strongly condensed.

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