[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Public Database of Geologic Formation Ages?



from Fowler (in prep):

Lower Maastrichtian:
top: 69.23
base 70.6 +/- 0.6
(Ogg et al, 2004)

Lower-Upper Maastrichtian boundary is only informally defined (Ogg et al, 
2004), 
but the definition shown here (Fowler, in prep) is the appearance of H. 
birkelundi (Landman & Waage, 1993; Cobban, 1993). Alternatives include 
magnetostratigraphy, exinction of rudist reefs, or inoceramid extinctions (Ogg 
et al, 2004)

Upper Maastrichtian:
top: 65.5 +/- 0.3
base: 69.23
(Ogg et al, 2004)

Base of the Upper Maastrichtian (Europe) correlated with the base of the H. 
birkelundi zone by Machalski et al (2007).

Dodgy enough?

 ----------------------------------
Denver Fowler
df9465@yahoo.co.uk
http://www.denverfowler.com
-----------------------------------



----- Original Message ----
From: "Thomas R. Holtz, Jr." <tholtz@umd.edu>
To: mrvivianallen@googlemail.com
Cc: Dinosaur Mailing List <dinosaur@usc.edu>
Sent: Tue, 23 August, 2011 16:48:04
Subject: Re: Public Database of Geologic Formation Ages?

On Tue, August 23, 2011 5:43 pm, Vivian Allen wrote:
> To the OP - just round to the nearest Ma? I need some dates for
> spreading continuous characters over a phylogeny at the moment, that's
> what I'm doing. So Late Maastrichtian would be ~66 Ma. Being more
> precise than that seems a bit dodgy - others here seem to agree, but
> if anyone has any opinions to the contrary I for one would welcome
> them.
>
I would say that you are probably being as precise as possible in nearly
all cases. In fact, it can be the case where you can't even tell if you
are in the Aptian or Albian, much less a mid-Aptian or late Albian or
whatever.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu    Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661

Faculty Director, Science & Global Change Program, College Park Scholars
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

Mailing Address:    Thomas R. Holtz, Jr.
            Department o
y of Maryland
            College Park, MD 20742 USA