[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
RE: Public Database of Geologic Formation Ages?
Not always enough of them. Comparative anatomy isn't even trained in MODERN
paleontological students to the degree it used to be. The cross-discipline
position now is a smattering of both geo and bio, without the emphasis on the
principles of either to get the researcher comprehensive _enough_ in both to be
an earnest researcher in both. Nor should he. We can't all be polymaths. That's
why you get people who know some crud about the disciplines you are not too
comprehensive on (as Tom said), and maybe they should just be coauthors rather
than just editors -- I know, don't want to share the limelight and the stage.
Jaime A. Headden
The Bite Stuff (site v2)
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion
> Date: Tue, 23 Aug 2011 14:18:59 +0100
> From: email@example.com
> To: firstname.lastname@example.org
> CC: email@example.com; firstname.lastname@example.org
> Subject: Re: Public Database of Geologic Formation Ages?
> On 23 August 2011 14:01, Thomas R. Holtz, Jr. <email@example.com> wrote:
> >> -----Original Message-----
> >> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu]
> >> On Behalf Of Saint Abyssal
> >> Sent: Monday, August 22, 2011 11:03 PM
> >> To: Dinosaur Mailing List
> >> Subject: Public Database of Geologic Formation Ages?
> >> I'm having a surprising amount of trouble finding precise
> >> ages for geologic formations. Is there a public database
> >> available with the ages of a significant number of
> >> stratigraphic units? I'm creating timelines for Wikipedia
> >> showing the duration of times represented by different units
> >> but having to hunt down ages for each one is exhausting.
> >> Worse, I'm having trouble finding exact numbers for many
> >> units. I understand the gist of say, "late Maastrichtian" but
> >> I need exact numbers to enter into the timeline template and
> >> to enter guesstimates as to what exact numbers the authors
> >> meant by this would violate Wikipedia's policy forbidding
> >> original research.
> > There are some regional ones, such as for Australia
> > (http://www.ga.gov.au/products-services/data-applications/reference-databases/stratigraphic-units.html)
> > or the US
> > (http://ngmdb.usgs.gov/Geolex/geolex_qs.html).
> > However, several things to keep in mind:
> > 1) Formations and other lithostratigraphic units are NOT time units and
> > their boundaries are NOT time boundaries: that is, the
> > boundary between Formation X and overlying Formation Y can be one age at
> > one location, but a different age at other ones.
> > Formational boundaries represent changes of depositional environment, not
> > depositional time. Classic example: the boundary between
> > the lower (nearshore sand deposits) Tapeats Sandstone and the upper
> > (offshore mudbank) Bright Angel Shale happened during the Early
> > Cambrian in the western part of the Colorado Plateau, but during the Middle
> > Cambrian further East. The formational boundaries shift
> > throughout time: they are diachronous or "time transgressive".
> > 2) As David pointed out, the vast majority of units do not have radiometric
> > dates, and they age is determined by interpolation
> > between datable units and by biostratigraphic, magnetostratigraphic, or
> > other means.
> > In other words, DON'T PUT IN NUMBERS when you don't have justification for
> > them! That is unscientific. Use the units that the
> > geologists use: that is the reason we use geochronologic terms like "late
> > Maastrichtian": they are accurate if not precise.
> > Also makes sure that you get the aid of someone who has studied
> > stratigraphy to do the editing of the stratigraphic entries.
> > (Just want to add that there are a lot of even professional
> > paleontologists--more today than in the past, actually--who actually are
> > lacking in basic knowledge of historical geological disciplines. This is
> > what comes from the field shifting to being predominently a
> > biological one rather than a shared geological-biological one).
> On the positive side, a lot more palaeontologists understand anatomy now!
> -- Mike.