This illustrates the relatively poor preservation of stem casts of Calamites cisti when the cast medium is shale.
While calamites foliage can be well-preserved in shale, the stems in such rock matrix are generally more deformed and more difficult to recover-- partly because they weather so quickly, but also the original sediments of clay and fine silt compact and lose much more of their original volume on their way to becoming shales, than do sand sediments on their way to becoming sandstone. Consequently, these shale casts of inner pith cavites of Calamites cisti are generally of lesser quality than their counterparts in sandstone.
Rock Type: Sandstone
Interval: Coalburg seam
Age: Middle Pennsylvanian Period, approx. 307 million years.
Location: Nicholas County, West Virginia; Alex Energy. Inc., Robinson
North Surface Mine, located about 10 miles west of Summersville, West Virginia,
just north of Route 39. It is an active surface mine and requires permission