Significant changes are made in stratigraphic nomenclature for the
Paleozoic formations of Minnesota that reflect subsurface data acquired
since 1969 and accord with changes in nomenclature in adjoining states.
For the Cambrian section, dolostone that intertongues with the lower
part of the Eau Claire Formation in the subsurface of south-central and
southwestern Minnesota is interpreted to be a tongue of the Bonneterre
Formation of northwestern Iowa. The Reno Member of the Franconia Formation,
together with the Birkmose Member, is now interpreted to compose most of
the formation, whereas the Tomah Member is now interpreted to have very restricted
subsurface distribution; an additional dolostone member, here informally
named the Davis, is recognized in the subsurface in south-central
Minnesota. The uppermost member of the overlying Jordan Sandstone is here
renamed the Coon Valley Member.
For the Ordovician section, the Galena is now elevated to group status.
The Cummingsville Formation, Prosser Limestone, and Stewartville Formation-formerly
members of the Galena--now correspond in rank with their equivalents
in adjoining states.
In the Devonian sequence, formerly classified as entirely Cedar Valley
Formation in Minnesota, the recently named Spillville Formation is recognized
in the base of the sequence, and the Wapsipinicon Formation is now
known to extend into Minnesota from Iowa. The name Cedar Valley is retained
for the overlying Devonian rock unit.
Mossler, John H..
RI-36 Paleozoic Lithostratigraphic Nomenclature for Minnesota.
Minnesota Geological Survey.
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