@misc{indiciaeb83030c89360,
  title = {Government Draw Bentonite Beds: a newly identified stratigraphic marker in the Virgin Creek Member of the Pierre Shale, central South Dakota ( USA).},
  author = {T. C. Nichols and A.F. Chleborad and D. S. Collins},
  year = {1987},
  url = {https://pubs.usgs.gov/publication/70015272},
  note = {Source identifier: 70015272}
}