Ancell Group
  

Champlainian Series,

Ordovician System


Type locality: The composite type section of the Ancell Group (Templeton and Willman, 1966, p. 29) was designated in the bluffs north of Ancell, between Dutchtown and Rock Levee, Mo. In the type locality the sandstones and carbonate rocks of the group overlie the Everton Dolomite and underlie the carbonate rocks of the Platteville Group.

Description: The Ancell Group of Indiana (Droste, Abdulkareem, and Patton, 1982) consists of three formations, the St. Peter Sandstone, the Dutchtown Formation, and the Joachim Dolomite. These three formations are in partial facies relationships with one another. The Ancell lies with unconformity on the rocks of the Knox Supergroup as follows: in northwestern Indiana on the Potosi Dolomite (Trempealeauan), in southwestern Indiana on the Everton Dolomite (Whiterockian), and elsewhere in the state on the Prairie du Chien Group (Canadian). On some of the highest erosion remnants along the unconformity at the top of the Knox, the Ancell rocks may be entirely missing, so that rocks of the Black River Group lie superjacent to Knox rocks. Generally the Ancell Group thickens from less than 50 feet (15 m) in northern Indiana to more than 450 feet (137 m) in southwestern Indiana. Lower Ancell rocks are Chazyan in age, and the upper Ancell is early Blackriverian. Rocks of the Ancell are present in faulted blocks in the Kentland structure in Newton County, Ind. (Gutschick, 1986).

Correlation: The Ancell Group of Indiana correlates with the Ancell Group of Illinois with the St. Peter Sandstone and the Glenwood Formation of Michigan; with the lower part of the Black River Limestone, the Wells Creek Formation, and the St. Peter Sandstone of Ohio; and with the lower part of the High Bridge Group and the Wells Creek Dolomite of central Kentucky and the St. Peter Sandstone and the Dutchtown Formation of western Kentucky (Droste and Shaver, 1983; Shaver and others, 1985).






 
 
 
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