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> From: Mike Keesey [mailto:email@example.com]
> Anyone know what time period "Portlandian" refers to? (Or is it a time
The Portlandian Stage is part of an alternative English geochronology for
the Late Jurassic-Early Cretaceous system.
The International system goes: Kimmeridgian - Tithonian - Berriasian -
Valanginian, with the J-K boundary at the base of the Berriasian.
The alternative English system goes: Lower Kimmeridigian (= Kimmeridgian in
the International system), Upper Kimmeridgian ( = Lower, Middle, and part of
the Upper Tithonian), Portlandian ( = rest of Upper Tithonian and Lower
Berriasian), Ryanzanian (= Middle and Upper Berriasian, and lowermost
Valanginian), and Valangianian. The J-K boundary is at the top of the
To make matters worse, the Russians sometimes use the term Volgian for a
unit equivalent to the Tithonian and Lower Berriasian of the International
system (or the Upper Kimmeridgian and Portlandian of the English).
Happy New Year, folks!
Thomas R. Holtz, Jr.
Department of Geology Director, Earth, Life & Time Program
University of Maryland College Park Scholars
College Park, MD 20742
Phone: 301-405-4084 Email: firstname.lastname@example.org
Fax (Geol): 301-314-9661 Fax (CPS-ELT): 301-314-7843