Back

Our observation of soil and soil section at this spot proved that Cheyenne Bottoms have hydric soils, typical soil for wetlands.  Hydric soils are those soils that are sufficiently wet in the upper part to develop anaerobic conditions during the growing season (http://soils.usda.gov/use/hydric/overview.html).  We found three critical factors which classify the soil as hydric: saturation, reduction, and presence of redoximorphic features.

Two images below show that top soil is high organic, dark gray-brown color.  Such a layer of decomposing organic matter accumulates at the soil surface when the soil is saturated for extended periods of time.  Saturation, the typical characteristic for hydric soil, occurs when enough water is present to limit the diffusion of air into the soil.

This picture illustrated the difference 

in color for A horizon and B horizon.  

While A horizon is dark gray brown, 

B horizon is brown-red containing clay, 

sand, and silt, rich in iron.

The mobilized iron tends to collect 

in aerobic zones within the soil 

where it oxidizes, or combines with 

additional oxygen, to form splotches 

of bright red brown color called mottles 

(source: http://www.na.fs.fed.us/spfo/pubs/n_resource/wetlands

/wetlands5_soils.htm)

 

This picture shows the strong gray matrix color all the way to the soil surface. Fluctuating water levels in the soil allow air to fill the larger pores as the water level lowers and then trap the air as the water level rises again.  When the iron dissolved in the water encounters a zone of trapped air, it farms a strong, red-brown colored precipitate. The precipitated colors are known as concentrations or mottles and are evident here in the AB and B layers. The gray matrix with bright mottles extending to very near the soil surface indicates a hydric soil

(source: http://www.na.fs.fed.us/spfo/pubs/n_resource/wetlands/

wetlands5_soils.htm)

 

The blue-gray layer with mottling generally describes wetland mineral soils. However, where saturation is prolonged, the slowed decomposition rate results in the formation of a dark organic layer over the top of the blue?gray mineral layer. Although classification criteria are somewhat complex, soils with less than 20 percent organic matter are generally classified as mineral soils and soils with more than 20 percent organic matter are classified as organic soils. For the purposes of this document, the organic layer becomes important when it reaches a thickness of approximately 16 inches. Under the right conditions, the layer can grow 

to many feet in thickness (source: http://www.na.fs.fed.us/spfo/pubs/n_resource/wetlands/wetlands5_soils.htm

wetlands5_soils.htm)

We notices white and brown red spots in the soil section which was calcium  iron. 

        

This picture shows salt accumulation in A (7-24 cm), mudcrack is formed probably from drought.  "Shrink and dry, wet and moist" pattern is typical for wetlands.       

 

Our group discussed the types of deposit found in this spot:

* wind blow deposit (sand dunes)

* river channel deposit

* flood deposit

* river bank deposit]

 

Back to the Cheyenne Bottoms map