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The Geology of Hillsdale County

Geology  [Click here to view full size picture] Information on the geology of our area covers a range of topics from soils and minerals, to floodplains, watersheds and topography.  The history of this area is a fascinating combination of glacial phenomena, weather and human impacts.

Surface Geology of Hillsdale County
Soils
Minerology
Floodplains
Watersheds
Bedrock
Museums

Surface Geology of Hillsdale County

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The topography of Hillsdale County is the result of four periods of glaciation, weathering, and recent human activity. The last period of glaciation, Wisconsin, completed recession about 10,000 - 14,000 years ago. The motion, deposition, and outwash from Wisconsin's lobes created the topography and some of the mineral features of the surface of Hillsdale County. The moraine distribution is the major source of the topography, and is responsible for some of the prominent local industries (e.g. sand, gravel, and cement) and some of the local health concerns(radon).

The dominant parent material of the soils of Hillsdale County is glacial till. The County soils are about 54% glacial till, 25% outwash, and about 1% alluvium. Residuum, material that has weathered in place from sedimentary rock, is a very small percentage of the soils because glacial till covers most of the bedrock up to a depth of about 300 feet. A very small amount of the Marshall Sandstone
Formation portion of the bedrock is exposed or close to the surface.

Ther Huron and Huron-Erie (Also called Saginaw and Erie) lobes of the glacier alternately covered Hillsdale County. The contact zone between the two lobes ran diagonally through the county from Somerset to Camden Townships. The resulting geographic landforms were till plains, moraines, glacial spillways and interlobate moraines. The rates of advance and melting determined the steepness of the slopes.

The Huron Lobe carried material derived from acidic sandstone and produced sandy and sandy loam soils. The Huron-Erie Lobe carried materials derived from limestone and the soils formed were loam and clay textured and relatively basic. The interlobate materials are mixed both vertically and horizonatally. This helps to explain the distinct natures of the soils in the northwest and southeast parts of the County and the diversity of the soils in the central part.

Hillsdale County has about 350 ponds, 42 lakes and is the headwaters for five of Michigan's major rivers. These sources of surface water provide recharge of the groundwater to the County's many wells.

Soils

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Hillsdale County has a wide variety of soil types. Textures can range from 35% stone to over 50% clay. Typically well drained sandy and sandy loam soils are found in northern Hillsdale County and poorer drained clay and silt based soils in the south part. For detailed soils information contact: United States Department of Agriculture, Natural Resources Conservation Service, 588 Olds St., Building #2, Jonesville, Michigan 49250, Telephone 517-849-9890.

Minerology

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Click for Animation of Oil Well. Minerals obtained and processed in Hillsdale County are sand, gravel, and stone from glacial deposits (i.e., surface mining) and oil, gas and brine. The glacial materials are further processed locally into sand, gravel and cement for road and construction materials. Oil, gas and brine are produced by drilling in the Albion-Scipio Field of the Trenton/Black River Formation at depths of about 200 to 12,000 feet. The oil and gas are found in pools in the Ordovician dolomite. The Albion-Scipio Field is a narrow (about 1 mile wide) strip and passes through Calhoun, Jackson, and Hillsdale Counties. It is the most productive field in Michigan.

Brine, a by product of crude oil recovery, is used in the County as dust control and maintenance on gravel roads. The excess brine is injected deep into the earth using Michigan Department of Environmental Quality (MDEQ) aprroved practices. Hydrogen sulfide, a noxious gas and potentially toxic, is a by-product of sour gas wells that must be recovered by approved MDEQ practices.

Radon gas, a carcinogen, is produced by the radioactive decay of a naturally occurring urainium isotope that exists in the minerals in Hillsdale County. The glaciation process excavated and pulverized rock and gravel to make a more permeable soil and substructure thereby allowing the radon gas to escape to the surface more easily. Unsafe accumulations of radon gas can occur in below ground enclosurers with little air circulation (i.e. basements) and is most severe in structures built on moraines.

Floodplains

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Flooding does not present much of a problem for County residents. Although there are several miles of floodplain geology soils only a few acres are subject to flooding (see map). Hard copy maps are alvailable from the United States Department of Agriculture, Farm Service Agency, 588 Olds St., Building #2, Jonesville, Michigan 49250, Telephone # 517-849-9890.

Watersheds

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Click here to view full size picture A watershed is all the area of land that drains water to a given point. Hillsdale County is the headwaters of 5 major watersheds: The Grand, Kalamazoo, River Raisin, St. Joseph, and Maumee.

Bedrock

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Bedrock of Hillsdale County consists of the eroded edges of the bowl-like formation that makes up the Michigan Basin. The oldest rock directly beneath the glacial drift veneer is the Coldwater Shale, which underlies the entire County and is the uppermost bedrock in the southern and eastern parts. It is overlapped in the northcentral part of the County by Marshall Sandstone that, in some places, is exposed or very near the surface.

Museums

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Geology, and minerolgy, plant, and animal collections from Hillsdale and the U.S. can be observed at the Hillsdale Cllege Museum.
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