Unique Location Reveals How Soils Developed

Unique Location Reveals How Soils Developed

Side-by-side parent materials unusual find.

There is a road cut made to make a road years ago through a side hill in Morgan County just north and east or Paragon in Morgan County that reveals a lot about how soils formed. Randy Staley, a private soil scientist, discovered the unique location several years ago. When the state soils contest was held in Morgan County recently, the Morgan County highway department recut the sides of the road cut so the parent materials were evident.

Bedrock

The parent material is what soils formed on thousands of years ago. It’s important to know because it can explain why some soils are underlain with gravel. Those are typically outwash soils just up from large streams where sand and gravel were laid down by water. When roots get into those zones, the sand and gravel become a limiting layer, limiting root growth, especially in very dry years because there is no moisture underneath.

Many central Indiana soils formed in till material left behind by the Wisconsin glacier. An earlier glacier, the Illinoian glacier, also formed some till soils. They are characterized by scattered, rounded rocks that pushed ahead of the glacier. Some of the most productive farmland on timber soils formed on these soils.

Soils that developed in wind-blown silt are called loess soils. Sometimes they formed over deeper till or another material underneath. These soils can be high in silt, but can be farmed successfully.

Old lakebed soils formed in what’s known as lacustrine material. It was laid down by water. Many of these soils, due to their location and heavy texture, are somewhat poorly to poorly drained.

Then there are soils that were made of wind- blown, fine sand during the Glacian age. These are said to be formed in eolian sand. Often these soils are doughty, but perform better if irrigated. If these soils are on a slope, they are referred to as dunes. The dune consist nearly entirely of wind-blown sand, and is not conducive to crop growth without irrigation.

Finally, some soils formed on top of bedrock. In the road cut, very heavy limestone is evident on one end of the cut, and more common layers of shale stacked upon each other are evident in a different location. Sometimes roots can grow through the shale layers, and they are not limiting layers. Often, however, they are limiting layers to root growth.

All of these materials are laid in side by side within 150 feet of each other side by side in the road cut, about 1.5 miles north of Highway 67, just off Duckworth Road on Grounds Road. The site is so unique that Chris Parker, Morgan County Extension ag educator, believes someone should nominate it as a point of geologic interest.

One are in the cut actually has eolian sand in layers, with darker layers over lighter layers. These are called lamellae. In some cases, they are fingers dipping up and donw. Here, they are horizontal.

If you’re in the area, it’s worth your drive off the beaten path to better udneerstand characterisitcs of soils you farm.
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