tonstein

tonstein

[′tän‚shtīn]
(geology)
Kaolinitic bands in certain coalfields which have characteristic fossil fauna from short-lived but widespread marine invasions.
References in periodicals archive ?
The slight evidence of volcanic activity in the shape of tuffaceous "tonstein" bands within the lacustrine shales, suggests a possible genetic link with the more substantial volcaniclastic interval in the lower part of the Valdeviar succession, but this cannot be regarded as a foregone conclusion.