Dennis Formation

Dennis Formation
Dennis Formation
Stratigraphic range: Carboniferous
Type	Formation
Location
Region	Missouri
Country	United States

The Dennis Formation is a geologic formation in Missouri. It preserves fossils dating back to the late Carboniferous period. The formation is part of the Kansas City Group, Missourian Stage, Pennsylvanian subperiod of the Carboniferous period.

The formation members, from bottom to top, are Canville Limestone, Stark Shale, and Winterset Limestone.

The three members form the major part of a cyclothem, created as sea water rise quickly and then gradually fall again over millions of years.

Dennis Formation Examples

Railroad cut showing Winterset Limestone, Dennis Formation, Upper Bronson Subgroup, Kansas City Group, Missourian Series, Pennsylvanian System. Note thin horizontal partings - very thin layers of shale separating the limestone periodically - a characteristic of many Kansas City Group limestone members. The thin shale layers represent a short period of time under different environmental conditions, or perhaps even a single catastrophic or large-scale event. Raytown, Missouri.
Railroad cut showing Winterset Limestone, Dennis Formation, Upper Bronson Subgroup, Kansas City Group, Missourian Series, Pennsylvanian System. Note the Stark Shale Member beneath the limestone - the softer shale has eroded and undercut the limestone above. Raytown, Missouri.
Railroad cut showing new rockfall Winterset Limestone next to older cliffs. Note the gray color of the weathered limestone vs the buff color of the new rockfall. Raytown, Missouri.
Detail of Winterset Limestone, Dennis Formation, Upper Bronson Subgroup, Kansas City Group, Missourian Series, Pennsylvanian System. Raytown, Missouri.