Seismotectonic maps in the vicinity of the lower Wabash Valley, Illinois, Indiana, and Kentucky - Digital Spatial Database: Magnetic dikes

Hildenbrand and Ravat (1997) inferred the locations of near-surface dikes from
analyses of high-resolution aeromagnetic data. The lines represent locations
of magnetic highs that they interpreted as dikes. Modeling indicates the
dikes are vertical, extend to within 200 m of the surface, and have the
magnetic properties of mafic or ultramafic rock. Some of the interpreted
dikes coincide with the easternmost Early Permian, mica peridotite and
perhaps lamprophyre dikes that Nelson mapped (these are in cover lampdike.)
Hildenbrand and Ravat concluded that the interpreted dikes are
also probably Early Permian ultramafic intrusions.