Geologic Time Scale 2012 publication Arthur Holmes, the Father of the Geologic Time Scale once wrote (Holmes 1965, p. 148): “To place all the scattered pages of earth history in their proper chrono- logical order is by no means an easy task”. Ordering these scattered and torn pages requires a detailed and accurate time scale. This will greatly facilitate our un- derstanding of the physical, chemical and biological processes since Earth appeared and solidified. Calibration to linear time of the succession of events recorded in the rocks on Earth has three components: Newsletters on Stratigraphy, Vol. 45/2, 171–188 Article Stuttgart, July 2012 On The Geologic Time Scale Felix M. Gradstein 1 , James G. Ogg 2 , and Frits J. Hilgen 3 With 6 figures and 1 table Abstract. This report summarizes the international divisions and ages in the Geologic Time Scale, pub- lished in 2012 (GTS2012). Since 2004, when GTS2004 was detailed, major developments have taken place that directly bear and have considerable impact on the intricate science of geologic time scaling. Precambrian now has a detailed proposal for chronostratigraphic subdivision instead of an outdated and abstract chrono- metric one. Of 100 chronostratigraphic units in the Phanerozoic 63 now have formal definitions, but stable chronostratigraphy in part of upper Paleozoic, Triassic and Middle Jurassic/Lower Cretaceous is still want- ing. Detailed age calibration now exist between radiometric methods and orbital tuning, making 40 Ar- 39 Ar dates 0.64 % older and more accurate. In general, numeric uncertainty in the time scale, although complex and not entirely amenable to objective analysis, is improved and reduced. Bases of Paleozoic, Mesozoic and Ceno- zoic are bracketed by analytically precise ages, respectively 541  0.63, 252.16  0.5, and 65.95  0.05 Ma. High-resolution, direct age-dates now exist for base-Carboniferous, base-Permian, base-Jurassic, base-Ceno- manian and base-Eocene. Relative to GTS2004, 26 of 100 time scale boundaries have changed age, of which 14 have changed more than 4 Ma, and 4 (in Middle to Late Triassic) between 6 and 12 Ma. There is much higher stratigraphic resolution in Late Carboniferous, Jurassic, Cretaceous and Paleogene, and improved in- tegration with stable isotopes stratigraphy. Cenozoic and Cretaceous have a refined magneto-biochronology. The spectacular outcrop sections for the Rosello Composite in Sicily, Italy and at Zumaia, Basque Province, Spain encompass the Global Boundary Stratotype Sections and Points for two Pliocene and two Paleocene stages. Since the cycle record indicates, to the best of our knowledge that the stages sediment fill is strati- graphically complete, these sections also may fulfill the important role of stage unit stratotypes for three of these stages, Piacenzian, Zanclean and Danian. Key words. Geologic Time Scale, Precambrian, Stratotype, Standard chronostratigraphy © 2012 Gebrüder Borntraeger, Stuttgart, Germany DOI: 10.1127/0078-0421/2012/0020 www.borntraeger-cramer.de 0078-0421/2012/0020 $ 4.50 Authorsʼ addresses: 1 Past Chair – International Commission on Stratigraphy (ICS), Geological Museum, University of Oslo, N-0318 Oslo, Norway. E-Mail: felix.gradstein@nhm.uio.no 2 Past Secretary General – ICS, Department of Earth & Atmospheric Sciences, Purdue University, West Lafayette, Indiana 47907-2051, USA 3 Chair – Subcommision on Neogene Stratigraphy of ICS, Department of Earth Sciences, Utrecht University, 3584 CD Utrecht, Netherlands