volcanic ash horizons interbedded with US Western
Interior ammonites with adjustments for cycle stratigraphy of some intervals provides a high-resolution
numerical scale for the Cenomanian through early
Maastrichtian. The late Maastrichtian correlations rely
on microfossil data calibrated to a spline and cycle fit
of C-Sequence marine magnetic anomalies.
4. Astronomical tuning of cyclic sediments was used for
Neogene, Oligocene, Paleocene, and most of Eocene
and portions of the Cretaceous, Jurassic, and
Triassic. The Oligocene through Neogene astronomical scale is directly tied to the Present (Hilgen et al.,
2012; Vanden Berghe et al., 2012); the older astronomical scale provides linear duration constraints on polarity chrons, biostratigraphic zones, and entire stages.
5. Proportional scaling was undertaken relative to component biozones or subzones. This procedure was necessary in portions of the Triassic and Jurassic. Devonian
stages were scaled from approximate equal duration of
a set of high-resolution subzones of ammonoids and
conodonts and tentative estimates of sedimentary
cycles’ duration, fitted to an array of dates.
The actual statistical procedures and error analysis
employed for the above proportionally scaled zones and
stages in major parts of GTS2012 were programmed and
executed by O. Hammer (in Agterberg et al., 2012). The
uncertainties on older stage boundaries systematically
increase owing to potential systematic errors in the different radiogenic isotope methods, rather than to the analytical precision of the laboratory measurements. In this
connection we mention that biostratigraphic error is fossil
event and fossil zone dependent, rather than age
dependent.
Ages and durations of Neogene stages derived from
orbital tuning are considered to be accurate to within a precession cycle (~20 kyr) assuming that all cycles are correctly identified and that the theoretical astronomical
tuning for progressively older deposits is precise. Paleogene dating combines tuning, radiometrics, and
C-sequence splining; hence, stage age uncertainty is larger
and varies between 0.2 and 0.5 Ma.
The Geologic Time Scale GTS2012 is displayed in
Figure 3 (from Gradstein et al., 2012).
Stratigraphic charts and tables
The plethora of names for time and time-rock units in local
regions lends itself to the production of wall charts and
stratigraphic lexicons that visualize the links between
regional schemes and the standard scale. The international
standard is developed in collaboration with officers of the
International Commission on Stratigraphy (ICS). The
Commission for the Geological Map of the World
(CGMW) in Paris and ICS closely collaborate on the
map and color coding of chronostratigraphic units on the
standard chart. The updated charts in PDF format are
freely available from websites https://engineering.
purdue.edu/stratigraphy/ and www.nhm2.uio.no/stratlex
and also are distributed by the CGMW.
A sophisticated, albeit easy time scale, graphics program for GTS2012 is called TSCreator @. This popular
software, with its large time scale dataset, is freely available from https://engineering.purdue.edu/Stratigraphy/
tscreator/. Now there are more than 25,000 Cambrian
through Holocene biostratigraphic, sea-level, magnetic,
and geochemical events in the public software database,
all calibrated to GTS2012. Cross-correlations are in place
for trilobites, conodonts, graptolites, ammonoids, fusulinids, chitinozoans, megaspores, nannofossils, foraminifers, dinoflagellates, radiolarians, diatoms, strontium
isotope, C-org and oxygen curves, eustatic sea-level
curves, etc. Scalable vector graphics output of any time
scale interval is an easy option. A majority of linear scale
drawings, with its calibrated event and zonal data in the
GTS2012 book, were initiated in TSCreator, before being
drafted in a final format.
Summary
The geologic time scale (GTS) provides the framework for
the physical, chemical, and biological processes in time on
Earth. The most up-to-date GTS is available since October
2012. Geoscientists can easily create and print time scale
charts, utilizing the freely available software package
“Time Scale Creator @.”
Bibliography
Agterberg, F. P., Hammer, O., and Gradstein, F. M., 2012. Statistical
procedures. In Gradstein, R., et al. (eds.), The Geologic Time
Scale 2012. Amsterdam: Elsevier, pp. 269–275.
Cooper, R. A., and Sadler, P. M., 2012. The Ordovician period. In
Gradstein, R. M., et al. (eds.), The Geologic Time Scale 2012.
Amsterdam: Elsevier, pp. 489–525.
Davydov, V. I., Korn, D., and Schmitz, M. D., 2012. The Carboniferous period. In Gradstein, R. M., et al. (eds.), The Geologic
Time Scale 2012. Amsterdam: Elsevier, pp. 603–653.
Gradstein, F. M., and Ogg, J. G., 1996. A Phanerozoic time scale.
Episodes, 19, 3–5. with insert.
Gradstein, F. M., Ogg, J. G., Smith, A. G., Agterberg, F. P., Bleeker,
W., Cooper, R. A., Davydov, V., Gibbard, P., Hinnov, L. A.,
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., Sanfilippo, A., Schmitz, B.,
Shackleton, N. J., Shields, G. A., Strauss, H., Van Dam, J.,
Veizer, J., van Kolfschoten, T. H., and Wilson, D., 2004. A Geologic Time Scale 2004. Cambridge University Press, 589 pp.
Gradstein, F. M, Ogg, J. G., Schmitz, M. D., Ogg, G. M., Agterberg,
F. P., Anthonissen, D. E., Becker, T. R., Catt, J. A., Cooper,
R. A., Davydov, V. I., Gradstein, S. R., Henderson, C. M.,
Hilgen, F. J., Hinnov, L. A., McArthur, J. M., Melchin, M. J.,
Narbonne, G. M., Paytan, A., Peng, S., Peucker-Ehrenbrink,
B., Pillans, B., Saltzman, M. R., Simmons, M. D., Shields,
G. A., Tanaka, K. L.,Vandenberghe, N., Van Kranendonk,
M. J., Zalasiewicz, J., Altermann, W., Babcock, L. E., Beard,
B. L., Beu, A. G., Boyes, A. F., Cramer, B. D., Crutzen, P. J.,
van Dam, J. A., Gehling, J. G., Gibbard, P. L., Gray, E. T., Hammer, O., Hartmann, W. K., Hill, A. C., Paul F. Hoffman, P. F.,
Hollis, C. J., Hooker, J. J., Howarth, R. J., Huang, C., Johnson,
GEOLOGIC TIME SCALE
287
Interior ammonites with adjustments for cycle stratigraphy of some intervals provides a high-resolution
numerical scale for the Cenomanian through early
Maastrichtian. The late Maastrichtian correlations rely
on microfossil data calibrated to a spline and cycle fit
of C-Sequence marine magnetic anomalies.
4. Astronomical tuning of cyclic sediments was used for
Neogene, Oligocene, Paleocene, and most of Eocene
and portions of the Cretaceous, Jurassic, and
Triassic. The Oligocene through Neogene astronomical scale is directly tied to the Present (Hilgen et al.,
2012; Vanden Berghe et al., 2012); the older astronomical scale provides linear duration constraints on polarity chrons, biostratigraphic zones, and entire stages.
5. Proportional scaling was undertaken relative to component biozones or subzones. This procedure was necessary in portions of the Triassic and Jurassic. Devonian
stages were scaled from approximate equal duration of
a set of high-resolution subzones of ammonoids and
conodonts and tentative estimates of sedimentary
cycles’ duration, fitted to an array of dates.
The actual statistical procedures and error analysis
employed for the above proportionally scaled zones and
stages in major parts of GTS2012 were programmed and
executed by O. Hammer (in Agterberg et al., 2012). The
uncertainties on older stage boundaries systematically
increase owing to potential systematic errors in the different radiogenic isotope methods, rather than to the analytical precision of the laboratory measurements. In this
connection we mention that biostratigraphic error is fossil
event and fossil zone dependent, rather than age
dependent.
Ages and durations of Neogene stages derived from
orbital tuning are considered to be accurate to within a precession cycle (~20 kyr) assuming that all cycles are correctly identified and that the theoretical astronomical
tuning for progressively older deposits is precise. Paleogene dating combines tuning, radiometrics, and
C-sequence splining; hence, stage age uncertainty is larger
and varies between 0.2 and 0.5 Ma.
The Geologic Time Scale GTS2012 is displayed in
Figure 3 (from Gradstein et al., 2012).
Stratigraphic charts and tables
The plethora of names for time and time-rock units in local
regions lends itself to the production of wall charts and
stratigraphic lexicons that visualize the links between
regional schemes and the standard scale. The international
standard is developed in collaboration with officers of the
International Commission on Stratigraphy (ICS). The
Commission for the Geological Map of the World
(CGMW) in Paris and ICS closely collaborate on the
map and color coding of chronostratigraphic units on the
standard chart. The updated charts in PDF format are
freely available from websites https://engineering.
purdue.edu/stratigraphy/ and www.nhm2.uio.no/stratlex
and also are distributed by the CGMW.
A sophisticated, albeit easy time scale, graphics program for GTS2012 is called TSCreator @. This popular
software, with its large time scale dataset, is freely available from https://engineering.purdue.edu/Stratigraphy/
tscreator/. Now there are more than 25,000 Cambrian
through Holocene biostratigraphic, sea-level, magnetic,
and geochemical events in the public software database,
all calibrated to GTS2012. Cross-correlations are in place
for trilobites, conodonts, graptolites, ammonoids, fusulinids, chitinozoans, megaspores, nannofossils, foraminifers, dinoflagellates, radiolarians, diatoms, strontium
isotope, C-org and oxygen curves, eustatic sea-level
curves, etc. Scalable vector graphics output of any time
scale interval is an easy option. A majority of linear scale
drawings, with its calibrated event and zonal data in the
GTS2012 book, were initiated in TSCreator, before being
drafted in a final format.
Summary
The geologic time scale (GTS) provides the framework for
the physical, chemical, and biological processes in time on
Earth. The most up-to-date GTS is available since October
2012. Geoscientists can easily create and print time scale
charts, utilizing the freely available software package
“Time Scale Creator @.”
Bibliography
Agterberg, F. P., Hammer, O., and Gradstein, F. M., 2012. Statistical
procedures. In Gradstein, R., et al. (eds.), The Geologic Time
Scale 2012. Amsterdam: Elsevier, pp. 269–275.
Cooper, R. A., and Sadler, P. M., 2012. The Ordovician period. In
Gradstein, R. M., et al. (eds.), The Geologic Time Scale 2012.
Amsterdam: Elsevier, pp. 489–525.
Davydov, V. I., Korn, D., and Schmitz, M. D., 2012. The Carboniferous period. In Gradstein, R. M., et al. (eds.), The Geologic
Time Scale 2012. Amsterdam: Elsevier, pp. 603–653.
Gradstein, F. M., and Ogg, J. G., 1996. A Phanerozoic time scale.
Episodes, 19, 3–5. with insert.
Gradstein, F. M., Ogg, J. G., Smith, A. G., Agterberg, F. P., Bleeker,
W., Cooper, R. A., Davydov, V., Gibbard, P., Hinnov, L. A.,
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., Sanfilippo, A., Schmitz, B.,
Shackleton, N. J., Shields, G. A., Strauss, H., Van Dam, J.,
Veizer, J., van Kolfschoten, T. H., and Wilson, D., 2004. A Geologic Time Scale 2004. Cambridge University Press, 589 pp.
Gradstein, F. M, Ogg, J. G., Schmitz, M. D., Ogg, G. M., Agterberg,
F. P., Anthonissen, D. E., Becker, T. R., Catt, J. A., Cooper,
R. A., Davydov, V. I., Gradstein, S. R., Henderson, C. M.,
Hilgen, F. J., Hinnov, L. A., McArthur, J. M., Melchin, M. J.,
Narbonne, G. M., Paytan, A., Peng, S., Peucker-Ehrenbrink,
B., Pillans, B., Saltzman, M. R., Simmons, M. D., Shields,
G. A., Tanaka, K. L.,Vandenberghe, N., Van Kranendonk,
M. J., Zalasiewicz, J., Altermann, W., Babcock, L. E., Beard,
B. L., Beu, A. G., Boyes, A. F., Cramer, B. D., Crutzen, P. J.,
van Dam, J. A., Gehling, J. G., Gibbard, P. L., Gray, E. T., Hammer, O., Hartmann, W. K., Hill, A. C., Paul F. Hoffman, P. F.,
Hollis, C. J., Hooker, J. J., Howarth, R. J., Huang, C., Johnson,
GEOLOGIC TIME SCALE
287