2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 15
Presentation Time: 8:00 AM-4:45 PM

The Heterogeneous Shear Model to Explain Polyphase Folding in the Baraboo Syncline Located around Baraboo, Wisconsin

SNIDER, Alex, Geology, Grand Valley State University, Allendale, MI 49401 and ZDAN, Stephen, Geology, Grand Valley State University, 1 Campus Drive, 125 Padnos, Allendale, MI 49401-9403, snideral@gmail.com

The Baraboo Syncline is a macroscale fold that deforms both Baraboo Quartzite and associated layers of phyllite. Syndeformational shearing of the limbs of the Baraboo Syncline created parasitic mesoscale folds that show a normal sense of vergence. These folds are also associated with a set of anti-parasitic mesoscale folds showing a reverse sense of vergence. Two models were proposed to explain the formation and kinematic significance of these anti-parasitic folds. The gravitational slump model falls apart when no deformed parasitic folds were present. The kink band model does a good job explaining the structures but falls apart when the scale of deformation is considered. The heterogeneous shear model introduced in this paper better explains the anti-parasitic structures.