Welcome to the GeoWhen Database, an attempt to sort
out the mess that man has made of the geologic timescale. This project
aims to reconcile the international stratigraphic standards with many of
the regional and archaic naming schemes that appear in the literature.
In the process, the most recent ICS time scale has been combined with information on
the estimated placement and length of other stages
in order to put approximate dates on all of the stratigraphic intervals recorded
here. In this way, we have sought to reconcile all of the various geologic time
scales into a single self-consistent whole.
What is this information based on?
The central stratigraphic classification and dates
are based on the 2004 time
scale endorsed by the International Commission on
Stratigraphy (ICS) and documented in Gradstein, Ogg, Smith, et al., A
Geologic Time Scale 2004, forthcoming
from Cambridge University Press. This has been augmented by consulting a
number of other reference works, including:
- Harland et al., A Geologic time scale, Cambridge University Press, 1982.
- Harland et al., A Geologic time scale
1989, Cambridge University Press, 1990.
- Gradstein and Ogg, "A Phanerozoic time scale",
Episodes, v.19, no.1&2, 1996.
- Haq and Eysinga, Geological Time Table,
Elsevier Science, 1998.
- Palmer and Geissman, 1999 Geologic Time Scale, Geological
Society of America, 1999.
- An Atlas of Life on Earth, Barnes and
Noble Books, 2001.
Database Conversion Tables
- and others...
The information provided by these sources on
regional and archaic stage nomenclatures has been correlated
with the international standards while taking care to preserve stage ordering
and common boundaries. Future versions of this database will be augmented
with direct input from the ICS working groups.
How reliable are the dates?
Dates are provided
for all boundaries, but they clearly vary in accuracy and reliability.
The best available dates have been listed with reference and error information. Most of the others represent some
form of approximation. This may amount to either copying the approximate values
given in other reference works or performing interpolations based on
estimates of the length and position of a particular
stage. In doing this, it is assumed that
the boundaries and relations between various stages are generally better known
than their exact ages. It should also be acknowledged that for many of the more obscure
regional and faunal stages the exact boundaries are not only poorly
known, but historically have been poorly defined. For these reasons, whenever
precise dates are needed, it is recommended that work be done in
reference to the ICS time scale.
I found an error or would like to make a contribution, what should I do?
project of this size, it is natural to expect that some errors will exist, and
that many of the relations and dates will improve with further study. If you find something that needs improvement, particularly missing
stages or stages out of order, feel free to contact Robert Rohde at firstname.lastname@example.org. It
is greatly preferred that you provide reference(s) to published literature relating to what you feel is wrong or incomplete
with this list. If you feel a stage is missing from the timeline, make sure you look at the A-Z stage list,
as many stages are synonymous and only one name appears on the timeline. Thanks for the help.
This work has been supported by funds from the Gordon Getty Foundation and the
Folger Foundation. Web hosting and resources are funded by the National
Science Foundation under the auspices of the CHRONOS Project. We also
wish to acknowledge that this work could not possibly exist without the
dutiful efforts of hundreds of geologists from whose years of study this compilation is
Robert A. Rohde
University of California at Berkeley