The study of wetland soils is frequently the most detailed and frustrating party of this assessment. Soils are the cummulative result of the all the conditions that the components have been exposed to over a long period of time. While the soils are still composed of only 2 basic ingredients (minerals and humus), the variety of possible combinations and manifestaions is enough to boggle the mind!
However, there is some good news. You, the investigator, don't usually need to be a soils expert to make a wetland determination. Certain "rules of thumb" may be enough to get you through the basics.
Below are some soils profile examples. In the first one, note gleying along entire profile. While certain horizons are sometimes difficult identify, the presence of this gleying is a very good indicator that wetland hydrology conditions exist. Note also the depth of the holes. The top 18 inches is the area required to be examined by the Corps of Engineers delineation manual.
Anaerobic indicators, such as this gleying and sometime the congretions and nodules associated with certain types of soils, are more difficult to locate in sandy / mineral soils. These indicators are most often found in more humic soils. Certain soils with red "parent material" will not show gleying at all and may not show mineral concretions so other anaerobic indicators must be used.
Soil descriptions are usually dependent upon acurate color descriptions. Colors are usually characterized by descriptors used by Munsell®. The page shown below is one of the "YR" series of Munsell colors.
Other pages are used to described those soils that are typically submerged. The page shown below is the "gley set" of the Munsell color plates. Complete sets of Munsell color plates are available commercially through many outlets.
The compilation of the final report on your wetland investigation will most certainly require some description of the soils and soil color. Again, many good references are available to assist in developing your skills in recognizing and describing wetland soils.