Polo Syncline (New Name)

Old Name: Polo Basin

Location

Southwestern Ogle County (B-4)

References

Horberg 1946, Willman and Templeton 1951, Templeton and Willman 1952, Kolata and Buschbach 1976, Kolata et al. 1983

Description

Willman and Templeton (1951) indicated a circular enclosed depression in west-central Ogle County on their structure-contour map of the top of the Galena Group. They named this depression the Polo Basin. Their structure map was modified from the Horberg (1946) map that shows a syncline open to the southwest in the same area. The state geologic map (Willman et al. 1967) and the Galena structure map of Bristol and Buschbach (1973) indicate the top of the Galena to be eroded in most of Ogle County. Small outliers of the Maquoketa Group in southern T24N, R8E, and northern T23N, R8E, indicate a structurally low area approximately coincident with Willman and Templeton's (1951) Polo Basin. Structure maps by Kolata and Buschbach (1976) of the top of the Glenwood Formation and by Kolata et al. (1983) of the top of the Franconia Formation show an open syncline much like the one originally mapped by Horberg (1946). The name Polo Basin is modified to Polo Syncline because the structure apparently lacks the internal closure needed to define a basin.