page_title: Maquoketa Group
section_title: Economic uses
hierarchical_section_title: Maquoketa Group / Economic uses
caption_attribution_description: English: Tentaculite fossils. Steven Baumann taken on 1-22-2006. This photo is entirely my work.
context_page_description: The Maquoketa Group is an assemblage of several geologic formations. It is Upper Ordovician in age and named for the Maquoketa River in Iowa. It exists in Missouri, Wisconsin, Iowa, Illinois, and Indiana. It is equivalent to the all but the basal formations of the Cincinnati Group in Ohio. Illinois and Indiana are the only states where the Maquoketa is considered a group. In other states it is a formation. The Maquoketa was deposited in a shallow intercontinental sea. Most of the clastic sediments are derived from the Appalachians, which were being raised at the end of the Ordovician. To a lesser degree some of the sediments were derived from the Ozark highlands to the southwest.
context_section_description: The Maquoketa has almost no economic use since it is dominantly a weak shale interbedded with thin dolomite, it is not good for track ballast or concrete aggregate and is often stripped and piled as waste in open-pit quarries.  The main exception is at the Neda's type section in Wisconsin, where it was once mined for iron ore. In Illinois the Neda is too thin and patchy to be economic.  The Brainard is too soft to be used as anything other than fill soil.  The Fort Atkinson is used to a limited degree as a decorative stone. The Scales is buried too deep and contains too much dolomite to be used for oil shale.
  The unit has been identified as a massive hydrocarbon reservoir. Recently legislation was passed in Illinois allowing horizontal drilling in the shale.
  The Maquoketa group is also a major aquitard.  This means that it is very impermeable, and therefore water only measurably flows through it on geologic time-scales. For this reason, it cannot serve as a source of groundwater.
  Although not useful to industry, it does contain rare and diverse fossils, some of which are only known in Illinois such as Tentaculites oswegoensis, a small unclassified fossil named after Oswego, Illinois and found in the basal Brainard.
caption: Tentaculites oswegoensis
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