@misc{indiciae81e4509ce6ba,
  title = {An Appalachian isochron: A kaolinized Carboniferous air-fall volcanic-ash deposit (tonstein)},
  author = {P.C. Lyons},
  year = {1992},
  doi = {10.1130/0016-7606(1992)104<1515:aaiakc>2.3.co;2},
  url = {https://pubs.usgs.gov/publication/70016921},
  note = {Source identifier: 70016921}
}