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Sediments
On August 30, 2009 we sent a stainless steel core sampler plunging through the darkness into the deepest point of the lake, twice. A 13" and 15" core were retrieved. The
fine silty gelatinous goo was black in color. The picture at left shows the sample. Viewed under the microscope, the sediment particles are small and uniformly shaped. The sediment contained 70% water and 30% solids. When the resulting solids were heated to 650 decrees Celsius, 30% of the dry solids burned off and 70% remained. This suggests that the solids are primarily of mineral (inorganic) origin and only 30% organic. [NOTE THESE VALUES NEED VERIFICATION].The picture at right gives a sense of the consistency of the sediments found at the deepest point of the lake. Here it slowly oozed out of the core tube into my hand. A core was also taken just outside the entrance of the northeast channel around Jones Island. This core contained 8" of black sediment over 6" of clean, brown peat.The peat is shown at left stuck in the core sampler's nose cone. Below is a picture of the peat under a microscope.It is so clean and consistent. It amazes me because I believe this has been buried beneath the lake's sediments for decades. This finding gives us a hint of this area's geography. [More to come].Above the peat layer is a layer of sediment. It is also a black ooze but differs from the sediments recovered from the deepest point. Instead of very fine black material, under the microscope the sediment from the channel entrance contains a variety of material as seen in the photo below left. Gravel retrieved from this area is shown below.
Much of the lake bed is covered with vegetation. However, the east end of the lake, near where it historically overflowed, is covered largely with gravel The murky picture below wasntaken August 30, 2009 about 100 feet off of George Street.SoilsIn a 1989 report by the Lakes Management Unit of the Lake County Health Department, the soils underneath the lake include 230 feet of clay over 15 feet of sand and gravel which lies on top of limestone bedrock. The last glaciers to leave the area left deposits of glacial till that were eventually covered with wind blown silt. These deposits form the gentle morains found the lake.
This is a map of the soils that surround Grays Lake. It comes from a report called "Soil Survey of Lake County, Illinois" published by the National Resources Conservations Service and the US Department of Agriculture. It is available here:
http://gis2.co.lake.il.us/output/Reports/LakeCountySoils.pdf
153A - Pella Silty Clay Loam 4.7% of the county - lake plaines, ground morains and outwash plains. Except for wetland plants, The type of soil is rated "fair" for most plants because it is too wet.
189A - Martinton Silt Loam 0.1% of the county - lake plain, ground and end morain
232A - Ashkum Silty Clay Loam 5.8% of the county - ground morain and end morain. Except for wetland plants, this type of soil is rated fair.
330A - Peotone Silty Clay Loam 1.4% of the county - ground morain.Rated "poor" for growth of most plants except for wetland plants.
530C - Ozaukee Silt Loam 2% of the county - ground and end morains.
531C2 - Markham Silt Loam ground and end moraines 3% of the county. Common trees are Northern Red Oak, White Oak, Black Walnut, and Shagbark Hickory.
698B - Grays Silt Loam 1.2% of the county - outwash plains and stream terrace
805B - Orthents Clayey Undulating 1.3% of the county - ground morain
978A - Wauconda and Beecher Silt Loams 1.2% of the county - ground morains, lake plains and outwash plains. Common trees are Northern Red Oak, White Oak, Black Walnut, and Shagbark Hickory.
979B - Grays Silt Loam 1.9% of the county- outwash plain, lake plain Common trees are Northern Red Oak, White Oak, Black Walnut, and Shagbark Hickory. This type of soil is rated "good" for grains, grasses, wild herbacious plants, hardwood trees, coniferous plants, and has "good" potential for woodland and wetland wildlife.
989A - Mundelein and Elliot Silt Loams
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