New Geologic Time Scale 2004
(Note: Since publication of this article, a reader has informed us that the chart shown is not the chart available from the source mentioned. Please see the addendum at the end of this article for his comments.)
A new geologic time scale is to be officially published in February 2005 (Gradstein et al. 2004). A brief explanatory note has already been posted on the official website of the International Commission on Stratigraphy. A 232 Kb PDF of the new chart is available here for download.
A large number of specialists working with astronomical cycles, radiogenic and stable isotopes, stratigraphy, palaeontology, magnetic polarity reversals and geomathematics have co-operated on the mammoth task of incorporating all the new data which has been acquired since the time scale that was published by Harland et al. 1990. A few highlights of the new timescale are listed below:
- Nearly 50 of the 90+ Phanerozoic stage boundaries are now defined, compared with 15 in 1990.
- More accurate and more precise age dating, with over 200 Ar/Ar and U/Pb dates ( > 50% were not available for GTS 89)
- 40Ar-39Ar ages have had to be re-computed due to the revised ages for laboratory monitor standards.
- Orbital tuning of cyclic sedimentary sequences has been employed. For example, the Neogene astronomical scale is directly tied to the Present giving an accuracy of 20 k yr (assuming the cycles are all correctly identified).
- Improved mathematical/statistical techniques that combine zones, polarity chrons, stages and ages to calculate the time scale.
This new time scale represents a great step forward in our geological knowledge, and we are greatly indebted to authors for the time and effort spent on this unprecedented collaborative project. It is hoped that individuals, companies and organisations will adopt the new timescale as soon as possible. Otherwise we are left to grapple with using a confusion of different out-dated timescales which can be more than 10 million years different at certain stage boundaries. A comparison of these differences is available at www.stratigraphy.org, to see just how far out you may be using an outdated scale. The worldwide web and e-mail should ensure that all geologists are aware of this important new development in geology, even before it is officially published, so please pass the message on to your colleagues.
Wall charts of the new timescale can be purchased at the Commission for the Geological Map of the World website address. That website is also the source of other nice maps and CD-ROMs like "The break-up of Pangaea and continental drift over the past 250 million years in ten steps."
References:
Gradstein, F.M..Ogg, J.G., Smith, A.G., Agterberg, F.P., Bleeker W., Cooper R.A., Davydov, V., Gibbard P., Hinnov, L., House, M.R., Lourens, L., Luterbacher, H-P., McArthur, J., Melchin, M.J., Robb, L.J., Shergold, J., Villeneuve, M., Wardlaw, B.R., Ali J., Brinkhuis, H., Hilgen, F.J., Hooker, J., Howarth R.J., Knoll, A.H., Laskar J., Monechi, S., Powell J., Plumb K.A., Raffi, I., Röhl, U., Sadler, P., Sanfilippo A., Schmitz, B., Shackleton, N.J., Shields, G.A., Strauss, H., Van Dam, J., Veizer, J., van Kolfschoten, Th., and Wilson, D.. 2004. A Geologic Time Scale 2004. Cambridge University Press, p. 500.
Harland, W.B., Cox, A.V., Llwellyn, P.G., Pickton, C.A.G., Smith, A.G., and Smith, D.G., 1990. A geological time scale 1989. Cambridge University Press, p. 263.
Addendum:
Many thanks to each of you who helped me search for the new Geologic Time Scale 2004 wallchart. To each of you, I wanted to follow up with my findings, for whatever they are worth.
The article entitled "New Geologic Time Scale 2004" printed in the Houston Geological Society Bulletin Volume 47 Number 8 April, 2005 [this article] mentions that "wall charts of the new timescale can be purchased at the Commission for the Geological Map of the World website address: http://ccgm.free.fr/index_gb.html." This website for CGMW does not offer the same wall chart as identified in the April Bulletin. The chart offered at http://ccgm.free.fr/index_gb.html is a different version, and not the identical Geologic Time Scale 2004 wallchart pictured in the [HGS Bulletin].
The publisher of the new book entitled "A Geologic Time Scale 2004" is Cambridge University Press. They indicate that the only way to purchase the wallchart is to purchase the book, either in paperback form ($70) or hardback form ($140). The chart is actually a "pull-out poster" according to Cambridge U. Press and is not sold separately...
Billy Forney III
McCombs Energy, L.L.C.