TY - GEN
T1 - Character of faulting beneath the western edge of the LaSalle Anticlinorium, central Illinois Basin; insight from a new seismic-reflection profile and a structure-contour map
AU - Kamp, Tyler P.
AU - Leetaru, Hannes E.
AU - Marshak, Stephen
N1 - Geological Society of America, North-Central Section, 50th annual meeting
PY - 2016
Y1 - 2016
N2 - The LaSalle Anticlinorium (or LaSalle Deformation Belt), is an overall N-S- to NE-SW-trending, 320 km by 130 km, zone of tectonic deformation along the axis of the Illinois Basin. Where exposed in northern Illinois, the western margin is a west-facing monocline. A new 15-km long E-W-trending seismic-reflection profile, that crosses the county line between Champaign and McLean Counties in east-central Illinois, provides insight into the configuration of underlying faults. This seismic line extends below the Great Unconformity (the Cambrian/Precambrian contact). It reveals a fault that dips steeply to the east, and penetrates Precambrian basement. The Great Unconformity has been uplifted by about 300 m on the hanging wall (eastern) side of the fault. A steeply dipping antithetic fault splays from the main fault just below the Great Unconformity. This splay also displays a reverse-sense component of displacement, but it dies out below the Late Cambrian-Early Ordovician Knox Dolomite. Two new structure-contour maps, one on the base of the Devonian-age New Albany Shale, and one on the top of the Ordovician-age Galena Dolomite, delineates the 3-D shape of the LaSalle Anticlinorium in the central Illinois Basin. Notably, an overall west-dipping slope, trending N-W, defines the western edge of the La Salle Anticlinorium. Across this boundary, the base of the New Albany drops from an elevation of +120 m (+400') -600 m (-2000') over a horizontal distance of 9 km (30,000'). The uplift appears to consist of several N-S-trending en echelon splays. The study area is underlain by a fault that cuts across and displaces the basement-cover contact, splays up-dip into a positive flower structure in the sedimentary cover, and dies out up-dip into monoclinal folds. It may represent inversion of Proterozoic normal faults. The presence of a flower structure, and of en echelon second-order folds, may indicate a component of strike-slip displacement along the overall belt (i.e., the LaSalle Anticlinorium transpressional). Movement on the faults in the LaSalle Anticlinorium occurred during distinct events in the Paleozoic.
AB - The LaSalle Anticlinorium (or LaSalle Deformation Belt), is an overall N-S- to NE-SW-trending, 320 km by 130 km, zone of tectonic deformation along the axis of the Illinois Basin. Where exposed in northern Illinois, the western margin is a west-facing monocline. A new 15-km long E-W-trending seismic-reflection profile, that crosses the county line between Champaign and McLean Counties in east-central Illinois, provides insight into the configuration of underlying faults. This seismic line extends below the Great Unconformity (the Cambrian/Precambrian contact). It reveals a fault that dips steeply to the east, and penetrates Precambrian basement. The Great Unconformity has been uplifted by about 300 m on the hanging wall (eastern) side of the fault. A steeply dipping antithetic fault splays from the main fault just below the Great Unconformity. This splay also displays a reverse-sense component of displacement, but it dies out below the Late Cambrian-Early Ordovician Knox Dolomite. Two new structure-contour maps, one on the base of the Devonian-age New Albany Shale, and one on the top of the Ordovician-age Galena Dolomite, delineates the 3-D shape of the LaSalle Anticlinorium in the central Illinois Basin. Notably, an overall west-dipping slope, trending N-W, defines the western edge of the La Salle Anticlinorium. Across this boundary, the base of the New Albany drops from an elevation of +120 m (+400') -600 m (-2000') over a horizontal distance of 9 km (30,000'). The uplift appears to consist of several N-S-trending en echelon splays. The study area is underlain by a fault that cuts across and displaces the basement-cover contact, splays up-dip into a positive flower structure in the sedimentary cover, and dies out up-dip into monoclinal folds. It may represent inversion of Proterozoic normal faults. The presence of a flower structure, and of en echelon second-order folds, may indicate a component of strike-slip displacement along the overall belt (i.e., the LaSalle Anticlinorium transpressional). Movement on the faults in the LaSalle Anticlinorium occurred during distinct events in the Paleozoic.
KW - ISGS
U2 - 10.1130/abs/2016NC-275297
DO - 10.1130/abs/2016NC-275297
M3 - Conference contribution
VL - 48
BT - Abstracts with Programs - Geological Society of America
PB - Geological Society of America (GSA), Boulder, CO, United States
ER -