Established Series


The St. Ignace series consists of shallow, well drained soils formed in loamy drift underlain by fractured limestone or breccia on glacial lake beaches, lake terraces, and lake benches. Slope ranges from 0 to 70 percent. Mean annual precipitation is about 762 mm (30 inches), and mean annual temperature is about 6.1 degrees C (43 degrees F).

TAXONOMIC CLASS: Loamy, carbonatic, frigid Lithic Haprendolls

TYPICAL PEDON: St. Ignace silt loam, on a 5 percent slope in a forested area. (Colors are for moist soil unless otherwise stated.)

A--0 to 13 cm (5 inches); black (10YR 2/1) silt loam, dark gray (10YR 4/1) dry; strong medium granular structure; friable; many fine to coarse roots; about 10 percent gravel; moderately alkaline; clear wavy boundary. [10 to 15 cm (4 to 6 inches) thick]

Bw--13 to 38 cm (5 to 15 inches); yellowish brown (10YR 5/4) gravelly silt loam; moderate medium granular structure; friable; common fine and medium roots; about 30 percent gravel; strongly effervescent; moderately alkaline; clear wavy boundary. [10 to 30 cm (4 to 12 inches) thick]

2Cr--38 to 64 cm (15 to 25 inches); fractured limestone breccia.

TYPE LOCATION: Mackinac County, Michigan; 100 yards west of Park Avenue on the south side of Mackinac Island (no section no.) T. 40 N., R. 3 W.

Depth to a paralithic contact: 25 to 50 cm (10 to 20 inches)
Rock fragment content: 2 to 35 percent gravel and 0 to 20 percent cobbles; total rock fragment averages from 5 to about 35 percent
Texture: fine-earth fraction is loam, silt loam, or sandy loam

Ap horizon, where present:
Thickness: 15 cm (6 inches)
Hue: 10YR
Value: 3
Chroma: 2 or 3
Reaction: slightly acid to moderately alkaline

A horizon:
Hue: 10YR
Value: 2
Chroma: 1 or 2
Reaction: slightly acid to moderately alkaline

Bw horizon:
Hue: 5YR to 10YR
Value: 3 to 5
Chroma: 3 to 6
Reaction: moderately alkaline

COMPETING SERIES: There are no other series in the same family. Closely related series are the Summerville soils which do not have a mollic epipedon.

GEOGRAPHIC SETTING: The St. Ignace soils are on nearly level to steep topography on the glacial Lake Algonquin beach and rock terraces, as well as on some higher glacial lake benches that are controlled by bedded limestone. Slope gradients commonly are 2 to 12 percent slope but range from 0 to about 70 percent. These soils are near the present shore line of Lake Michigan and Lake Huron and the climate is modified by these bodies of water. Mean annual precipitation ranges from 686 to 787 mm (27 to 31 inches). Mean annual temperature ranges from 5.6 to 6.7 degrees C (42 to 44 degrees F).

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Alpena, Longrie and Ruse soils. The excessively drained Alpena soils contain bedrock at depths greater than 152 cm (60 inches) and are on similar landscape positions with the St. Ignace soils on glacial lake benches and lake beaches. The well drained Longrie soils are contain bedrock at depths from 50 to 102 cm (20 to 40 inches) and are on similar landscape positions. The poorly drained or very poorly drained Ruse soils are in depressions and in association with the St. Ignace soils.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained. Potential for surface runoff is negligible to high depending on slope. Saturated hydraulic conductivity is moderately high or high through the soil material. Permeability is moderate or moderately rapid through the soil material.

USE AND VEGETATION: The greater part is in forest with a small part used for hay and pasture. Native vegetation consists of Northern Hardwoods with some balsam fir and northern white cedar.

DISTRIBUTION AND EXTENT: MLRAs 94A and 94B in the northern part of Lower Michigan and southeastern part of the Upper Peninsula of Michigan. The series is of small extent


SERIES ESTABLISHED: Emmet County, Michigan, May, 1970.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon: from the surface to a depth of 13 cm (5 inches) (A horizon).
Cambic horizon: from a depth of 13 to 38 cm (5 to 15 inches) (Bw horizon).
Paralithic contact: at 38 cm (15 inches) (top of the 2Cr horizon).

The classification to Rendolls is based on laboratory data of surrounding soils that contained more than 45 percent of calcium carbonate equivalent in the horizon immediately below the mollic epipedon.

ADDITIONAL DATA: Soil Interpretation Record No.: MI0198.

National Cooperative Soil Survey