Illinois Glacial Drift Thickness Contours and Polygons

Contour lines and polygons map the thickness of glacial drift deposits across Illinois, ranging from less than a few feet to approximately 600 feet. The dataset is derived from ISGS Circular 490 by Piskin and Bergstrom (1975), Plate 1, with a nominal scale of 1:500,000. It was digitized into an SDE feature dataset and is hosted by NASA Earthdata.

Use Cases

• Model subsurface geology by analyzing thickness contours and polygon-coded thickness ranges.
• Identify regions of thick drift in major preglacial valleys using the coded thickness attribute.
• Map areas of thin drift (less than 25 feet) intersected by bedrock outcrops in southern and western Illinois.
• Classify deposit types (e.g., till, loess, glaciofluvial) based on the documented character of the drift.

Strengths

• Thickness data spans a wide range from under a few feet to approximately 600 feet.
• Includes both contour lines with specific thickness and polygons representing thickness ranges.
• Original source is a published geological circular (ISGS Circular 490) from a state survey.

Limitations

• Data originates from a 1975 source, which may not reflect current surface conditions or measurements.
• The nominal map scale of 1:500,000 limits fine-grained spatial resolution.
• Specific row counts, column details, and sample data are unavailable for assessment.

Provenance

Source

ISGS Circular 490 by Piskin and Bergstrom (1975), Plate 1.

Collection Method

Digitized from a published geological map into an SDE feature dataset.

Time Range

Publication date 1975; temporal coverage of the underlying geological data is null.

Freshness

null

Geography

State of Illinois, United States.