MGS Guidance on the Coon Valley Member
Drill cuttings sample of poorly sorted sandstone from a Coon Valley Member deposit in Washington County, Minnesota.

The Minnesota Geological Survey has released new guidance on how best to recognize the Coon Valley Member (Oneota Dolomite, Prairie du Chien Group) and how to differentiate it from the underlying Jordan Sandstone in southeastern Minnesota.

Click to view/download MGS Guidance on the Coon Valley Member (PDF)

The intended audience is the water well drilling community, as there are rare situations where precise recognition of the Coon Valley Member is important for code compliance (per Minnesota Rules, Chapter 4725).

Generalized stratigraphic column of the St. Peter Sandstone, Prairie du Chien Group, and Jordan Sandstone.
Generalized stratigraphic column describing the vertical location of the St. Peter Sandstone, members of the Prairie du Chien Group, and the Jordan Sandstone units in relation to one another. To the right are summarized descriptions of the common rock types associated with each unit.
Bedrock core from Ramsey County showing the Coon Valley Member and underlying Jordan Sandstone.
An interval of drill core from Ramsey County that passes through the Coon Valley Member (Prairie du Chien Group) and Jordan Sandstone. Note how this single deposit of the Coon Valley Member is composed of a mixture of thinly bedded rock types (primarily dolostone and sandy dolostone in this example) while the Jordan Sandstone is entirely well sorted sandstone. Up is towards the left.

Questions?

For questions regarding the geology of the Coon Valley Member, please contact:

Minnesota Geological Survey
[email protected]
612-626-2969

For all other questions regarding the laws and rules for construction and sealing of wells and borings in Minnesota, please contact:

Minnesota Department of Health, Well Management Section
651-201-4600 or 800-383-9808
[email protected]

Related news releases

Share

Last updated on