On the Appalachian Plateau of New York, ENE striking joints parallel the mid‐continent contemporary stress field and do not correlate with other structures. Joints within Ohio, Indiana, Michigan, and West Virginia also parallel the mid‐continent maximum horizontal compression as indicated by hydraulic fracture measurements. In northern Indiana, where the contemporary stress field deviates significantly from the orientation of the mid‐continent stress, the attitude of the joints deviates accordingly. In addition to joints, structures on several scales from subcontinent size fracture systems to microfabrics in shales apparently parallel the mid‐continent stress field. From this I conclude that these joints are mode I cracks whose orientation corresponds to the contemporary tectonic stress field. In itself, the formation of these structures constitutes a tectonic event that has often been overlooked in favor of tectonic events that produce the more spectacular but less pervasive faults and folds.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology