Re: re: geological periods

[Thomas_R_HOLTZ@umail.umd.edu (th81)]

>
>A point worth noting, please use early, middle or medial, and late for 
>subdivisions of time and lower, middle, and upper for subdivisions of the 
>rock sequences.

Furthermore, only capitalize those that are formal subdivisions.  For
example, the "Upper Maastrichtian" refered to below should be "upper
Maastrichtian", as there are no formal subdivisions for that stage.

For future reference, the important subdivisions for dinosaur workers are
the Lower (Early), Middle, and Upper (Late) Triassic, the Lower (Early),
Middle, and Upper (Late) Jurassic, and the Lower (Early) and Upper (Late)
Cretaceous.  Note that there is *no* formal Middle Cretaceous (despite it
showing up, among other places, in Lucas' textbook and Upchurch's sauropod
phylogeny paper.  There is an alternative to the twofold division of the
Cretaceous, but these subunits are NOT Lower, Middle, and Upper.  They must
be refered to by name: Neocomian, Gallic, and Senonian.

Hope this helps,
> ----------
>From: dinosaur
>To: Multiple recipients of list
>Subject: re: geological periods
>Date: Mon, Jan 22, 1996 6:03PM
>
>The reason periods (eg. Maastrichtian) are used instead of dates is
>because the dates will change as better radiometric (or other)
>techniques are developed. Therefore don't worry about the dates. Every
>author can use a different set of dates, as long as they reference time to
>the standard stratigraphic periods (this IS standardized, fortunately, with
>minor differences across the Atlantic not worth worrying about). If you
>need a more specific time reference, use Upper, Middle, and Lower. eg.
>Upper Maastrichtian.
>


Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Dept. of Geology
University of Maryland
College Park, MD  20742
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Fax: 301-314-9661
Phone:301-405-4084