Tonstein | Article about tonstein by The Free Dictionary
Kaolinitic bands in certain coalfields which have characteristic fossil fauna from short-lived but widespread marine invasions.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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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.