Hi Bill,
It looks most likely to be ripple marks. Here are some references I found:
Ripple marks and trace fossils in the Rose Hill Formation
I would certainly contact this geology professor as he seems knowledgeable in the area.
https://ngmdb.usgs.gov/Geolex/UnitRefs/RoseHillRefs_3632.html
Of the fossils mentioned here (brachiopods, ostracodes, trilobites, and tentaculitids) it does not match most of these. Only perhaps some ostracod marks.
https://www.osti.gov/biblio/5791090-origin-middle-silurian-keefer-sandstone-east-central-appalachian-basin
It definitely looks like it was formed on an old shoreline.
When taking pictures also try to include something for scale. Are there any more edges of this pattern or does it pretty well cover the whole rest of the sample?
Let me know what you find out. I have enjoyed collecting fossils in MD. It has something from every geological period. I have attached a list of MD fossil sites were I collected in 2015.
Let me know what you find out.
Jim Chandler
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