Lake Iroquois and the Glaciofluvial Deltaic Deposit at Joes Lake, Lanark Highlands, Ontario

About 18,000 years ago the Laurentide Ice Sheet reached its maximum thickness and  southward extent, covering Eastern Ontario with a thickness of over two kilometers of ice, and extending southward to New York City.   The southern edge of the glacier then started to retreat northward.  In the 1,500 year period starting about 12,500 years ago eastern Ontario changed from ice covered to ice free.   As the edge of the glacier retreated northward melt water from the retreating glacier formed a proglacial lake,  Lake Iroquois, a precursor of Lake Ontario.  Lake Iroquois covered all of present day Lake Ontario and extended northward abutting on the retreating glacier.   In its early stages Lake Iroquois covered Kingston and all of Prince Edward County, and then grew larger and extended northward as the glacier retreated.   There were two factors that allowed Lake Iroquois to extend northward and cover what is now dry land.   First, the weight of the Laurentide Ice Sheet had depressed much of Eastern Ontario from 175 to 230 meters.  Second, the retreating glacier formed an ice dam that prevented Lake Iroquois from draining down what is now the St. Lawrence River.  (The lake drained from an outlet at Rome, New York and then to the Hudson River.)

Twenty-two years ago Inez M. Kettles of the Geological Survey of Canada issued a report on the glacial deposits in Lanark, Frontenac and Leeds Counties.   (See:  Kettles, I.M., 1992, Glacial Geology and glacial sediment geochemistry of the Clyde Forks - Westport area of Ontario, Geological Survey of Canada, Paper 91-17.  The report can be downloaded from:
http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=133492).  

Inez Kettles  reports that glacial Lake Iroquois covered much of Lanark County, extending at least as far northward as Joes Lake in the Township of Lanark Highlands.   (Joes Lake is the name of both a lake and small village.  It is about 45 kilometers north west of Perth and is known for its fishing and magnificent views.  It is named for an Algonquin who had a camping spot over the lake and was known to walk to and from Perth. I drove.)       

Inez Kettles reported a large delta at Joes Lake that she identified as a proglacial subaerial outwash that she believes was built within 3 km of the retreating ice margin.  She mentions that “The exact position of the ice margin as the delta  was forming, is however, uncertain and it is possible that the delta is an ice contact deposit.  The cobbly, bouldery texture of some foreset beds exposed at Joes Lake and the presence of a well developed kettle hole on the delta surface indicate that these sediments were deposited close to the ice.  It is also possible that some sediments mapped as ice contact glacial deposits in the channel north of and leading to the delta, were deposited as proglacial outwash.”

Last year Victoria Lee of the Ontario Geological Survey issued a report on the aggregate resources of Lanark County that covered the glacialfluvial deposits, including the gravel pit at Joes Lake.   (See, Lee, V.L. 2013, Aggregate resources inventory of the County of Lanark, southern Ontario: Ontario Geological Survey, Aggregate Resources Inventory Paper 189, 85 p.    Her report can be downloaded from:
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/ARIP189/ARIP189.pdf   )  

When discussing the deposit at Joes Lake Victoria Lee  mentions:   “The deposit is a large glaciolacustrine deltaic deposit.  The delta is inferred to have been deposited close to the ice margin ... The deposit material, ranging from cobble-sized to silt, is well sorted with distinct layers of cobbles, gravel, sand and silt-rich layers.  ... Well-defined terraces mark the boundaries of the deposit.  One licensed pit (Pit No. 3) and one unlicensed pit (Pit No. 55) have been developed in the resource area.  Face heights in the pits range from 4 to 10 m; however, available borehole records indicate the potential for more than 15 m of sand and gravel locally.  Calcite cementation within the deposit holds material 30 degrees off the vertical and cause potential problems during extraction...”

Below are photographs  taken at the sand and gravel pit in the proglacial subaerial outwash deposit just to the north of Joes Lake along the Lavant Darling Road.

The last two photos show underlying beds of cobbles and sand that are truncated by later deposited layered  beds of cobbles and sand.

Inez Kettles’ report covers large parts of Lanark, Frontenac and Leeds counties.  Figure 10 to the report is a map that covers Clyde Forks, Sharbot Lake, Tichborne, Westport, Morton, Smiths Falls and Carleton Place.   It shows selected glaciofluvial deposits and glacial striae, and gives a good indication of the direction the glacier was moving.   Figure 11 shows the distribution of drumlins in the Clyde Forks, Westport, Smiths Falls and Ottawa area.  Both figures are worth a look.

In 1936 A.P. Coleman of the Ontario Department of Mines published a report on Lake Iroquois with an accompanying Map No. 45f entitled Lake Iroquois and Related Ice Front at the Time of the Rome Outlet  (Scale, 5 miles to the inch).    It is worth a look.  Below I’ve provided a copy of the map.  The part shaded green is the retreating glacier.  The part in blue, which covers Prince Edward County and Kingston, is Lake Iroquois.

The copy doesn’t do justice to the map, which can be downloaded from http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/ARM45F/ARM45F.pdf

Christopher Brett
Perth, Ontario