Farmdale Soil

Lithostratigraphy: Farmdale Soil
Chronostratigraphy: Cenozoic Erathem >>Quaternary System >>Pleistocene Series

Primary source

Willman, H. B., and John C. Frye, 1970, Pleistocene Stratigraphy of Illinois: Illinois State Geological Survey Bulletin 94, 204 p.

Contributing author(s)

H. B. Willman and John C. Frye

Name

Original description

Farmdale Soil (Willman and Frye 1970).

Derivation

It is named for Farmdale, Tazewell County.

History/background

The Farmdale Soil has not previously been described formally as a soil-stratigraphic unit though the peaty deposits of the Farmdale Silt (now the Robein Silt) and the Farmdalian Substage were described many years ago.

Type section

Type location

Its type section is the Farm Creek Section (table 6), NE SW SE Sec. 30, T. 26 N., R. 3 W., Tazewell County, which was the type section for the Farmdale Loess and Farmdale Silt and also serves as the type section for the Robein Silt and the Farmdalian Substage.

Table 6 -- Stratigraphic Sections (partial)
The following stratigraphic sections illustrate exposures in Illinois and document type localities and analytical samples for Pleistocene units.

• 
  Enion Section (cont.), Farm Creek Section, and Flat Rock Section

Stratigraphic relationships

The accreted organic-rich Farmdale Soil generally rests on Roxana Silt and is overlain by Morton Loess, Peoria Loess, or the Wedron Formation.

• 
  Fig. 8 -- Diagrammatic cross section showing the relations of formations and members of Wisconsinan age in northern and western Illinois.

Table 6 -- Stratigraphic Sections (partial)

• 
  Cache Section and Campbells Hump Section
• 
  Pulleys Mill Section, Rochester Section, and Tindall School Section
• 
  Tindall School Section (cont.) and Toulon Section

In-situ profiles of the Farmdale Soil, where they occur in relatively thick loess sections and, particularly, close to the valleys of the Mississippi and Illinois Rivers, are nearly everywhere truncated into or below the B₂-zone of the soil. The episode of widespread erosion that coincided with the advance of the Woodfordian glaciers was particularly effective in areas of sharp topographic relief adjacent to major valleys, whereas poorly drained locations where the Farmdale Soil accumulated were less affected. Therefore, the Farmdale Soil in thick loess sections commonly consists of a deeply leached CL-zone overlain at an erosional contact by calcareous Peoria or Morton Loess.

Table 6 -- Stratigraphic Sections (partial)

• 
  Chapin Section and Cottonwood School Section
• 
  Cottonwood School Section (cont.) and Enion Section
• 
  Flat Rock Section (cont.), Gale Section, and Jubilee College Section
• 
  Jubilee College Section (cont.), Lewistown Section, and Malden South Section
• 
  Pleasant Grove School Section
• 
  Pulleys Mill Section, Rochester Section, and Tindall School Section
• 
  Wedron Section (cont.) and Zion Church Section
• 
  Zion Church Section (cont.)

A fully developed in-situ Farmdale Soil can be observed only in areas of relatively thin loess on flat uplands remote from major drainage. In such places the profile generally displays a reddish brown, clayey B₂-zone that grades downward and is overlain by Peoria Loess.

The Farmdale Soil is exceeded only by the Sangamon Soil in its use as a widespread stratigraphic datum within the Pleistocene deposits of Illinois.

Age and correlation

The Farmdale Soil has yielded more than 20 radiocarbon dates ranging from approximately 21,000 to 27,000 years before present.

• 
  Table 1 -- Selected Stratigraphically Significant Radiocarbon Dates From Illinois (94 dates from 30 counties).

Environments of deposition

The Farmdale Soil formed as an organic-rich, intrazonal soil through accumulation of organic debris and silt in poorly drained environments, with contributions from sheetwash and eolian deposition.

ISGS Codes

ISGS Code and Symbol

Stratigraphic Code	Geo Unit Designation
0590	--