Galena Group
Encyclopedia
The Galena Group or Galena Limestone refers to a sedimentary sequence of Ordovician
limestone
that was deposited atop the Decorah Shale
. It is part of the Ordovician stratigraphy of the Upper Midwestern United States. It was deposited in a calm marine environment, and is fossiliferous.
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
that was deposited atop the Decorah Shale
Decorah Shale
The Decorah Shale is a fossiliferous shale that makes up the lower most formation in the Galena Group. The Decorah lies above the Platteville Limestone and below the Galena Limestone in the sedimentary sequence that formed from the shallow sea that covered central North America during Ordovician Time...
. It is part of the Ordovician stratigraphy of the Upper Midwestern United States. It was deposited in a calm marine environment, and is fossiliferous.