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40Ar/39Ar whole-rock data constraints on Acadian diagenesis and Alleghanian cleavage in the Martinsburg Formation, eastern Pennsylvania

American Journal of Science

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Abstract

A comparison of 40Ar/39Ar age spectra of whole-rock mudstone and slate samples from the Ordovician Martinsburg Formation at Lehigh Gap, Pennsylvania, and stratigraphic and thermal constraints support an Alleghanian age for regional slaty cleavage and a late Acadian age for diagenesis in these rocks. Age spectra from mudstones have a sigmoidal shape, with slopes that climb steeply from apparent Mesozoic ages to intermediate saddle regions with Devonian apparent ages, and then climb steeply again to Late Proterozoic apparent ages. The steps with these oldest apparent ages are interpreted to be dominated by Late Proterozoic detrital muscovite. The saddle region of the mudstone samples gives very Late Silurian to earliest Devonian ages, which are maximum ages of diagenetic micas and which eliminate a Taconic age for the cleavage. The ages of the saddle regions of the slate samples containing cleavage-forming muscovite is

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
40Ar/39Ar whole-rock data constraints on Acadian diagenesis and Alleghanian cleavage in the Martinsburg Formation, eastern Pennsylvania
Series title:
American Journal of Science
Volume
296
Issue:
7
Year Published:
1996
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
766
Last page:
788
Number of Pages:
23