Timescale References

Allaby A. & Allaby M., eds., "A Dictionary of Earth Sciences," [1990], Oxford University Press: Oxford UK, Second Edition, 1999.

Harland W.B., et al., "A Geologic Time Scale 1989," Cambridge University Press: Cambridge UK, Revised Edition, 1990.

Huff WD, D Davis, SM Bergström, MPS Krekeler, DR Kolata, & C Cingolani (1997), A biostratigiaphically well-constriained K-bentonite U-Pb zircon age of the lowermost Darriwilian Stage Middle Ordovician) from the Argentine Precordillera. Episodes 20: 29-33.

Cloud, P. (1988) Oasis in space: Earth history from the beginning. Norton, New York.
Precambrian

Goldblatt, C., Zahnle, K. J., Sleep, N. H., and Nisbet, E. G.: The Eons of Chaos and Hades, Solid Earth, 1, 1-3, doi:10.5194/se-1-1-2010, 2010. abstract pdf
The Geological Timescale

Felix M. Gradstein, James G. Ogg, Alan G. Smith (Editors); A Geologic Time Scale 2004, Cambridge University Press, 2005, (ISBN 0-521-78673-8).

Hofmann, H.J. 1990, Precambrian time units and nomenclature - the geon concept. Geology, v. 18, p. 340-341.
Geon

Hofmann, H.J. 1992, New Precambrian time scale: Comments. PDF
Geon

Hofmann, H.J., 2003. Eons and geons - a simple planetary time scale. Geological Association of Canada, Nuna Conference on Time and Time scales. Mt. Tremblant, Abstracts, p. 3-6, and poster.
Geon

IUCS (2004), International Stratigraphic Charts, International Union of Geological Sciences: International Commission on Stratigraphy, 2004.

Judson S. & S.M. Richardson, Earth: An Introduction to Geologic Change, (Englewood Cliffs, NJ, Prentice Hall, 1995) (Englewood Cliffs, NJ, Prentice Hall, 1995).

Mitchell CE, X Chen, SM Bergström, Y-D Zhang, Z-H Wang, BD Webby & SC Finney (1997), Definition of a global boundary stratotype for the Darriwilian Stage of the Ordovician System. Episodes 20: 158-166.

Brad Pillans Talking about time: the Geological Time Scale In: Roach I.C. ed. 2004. Regolith 2004. CRC LEME, pp. 276-278. PDF
Geon

Poling J, Geologic Ages of Earth History page. Uses periods and dates from A Geologic Time Scale 1989 by Harland, W. Brian, Richard Armstrong, Allan Cox, Craig Lorraine, Alan Smith and David Smith, and from "A Triassic, Jurassic and Cretaceous time scale," by Gradstein, F.M., F.P. Agterberg, J.G. Ogg, J. Hardenbol, P. van Veen, J. Thierry and Z. Huang. 1995.in pp. 95-126 of W.A. Bergrgren, D.V. Kent, M.-P. Aubry & J. Hardenbol (eds.), Geochronology, Time Scales, and Global Stratigraphic Correlation. SEPM Special Publication No.54).

Rudwick, M.J.S. 1985. The Meaning of Fossils: Episodes in the History of Palaeontology. Second edition. University of Chicago Press, Chicago.
Deep time, geology, and paleontology

Walker, J.D., and Geissman, J.W., compilers, 2009, Geologic Time Scale: Geological Society of America, doi: 10.1130/2009.CTS004R2C. pdf

Woodward, H.P. 1929, Standardization of geologic time-units. Pan-American Geologist, v. 51, p. 15-22.
Geon