Helderbergian | Article about Helderbergian by The Free Dictionary
A North American stage of geologic time, in the lower Lower Devonian.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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The lower two units of dark shale, chert, and cherty limestone did not yield diagnostic fossils, but were provisionally placed in the earliest Devonian (Helderbergian
) by Wilson and Majewske (1960).