I saw this in a huge sandstone rock in the Pennsylvanian deposits of Palo Pinto County, Texas. It is either the Mingus or Brazos River Formation where I saw lots of wood preserved. Calamites and stigmaria everywhere but also a brachiopod in a lower layer. It may just be geologic shatter marks but I can't make any sense out of it at all. This is the Strawn Group of the Des Moines Series. The whole photo shows a space about 20 X 30 cm.