S1: The Geologic Time Scale 2020

Felix M. Gradstein,
Universities of Oslo, Norway and Portsmouth, UK

Lecture on 8 December 2020 for the AstroGeo Seminar

The standard global Geologic Time Scale (GTS) is the framework for deciphering and understanding the long and complex history of our planet, Earth. As Arthur Holmes, the Father of the Geologic Time Scale wrote in 1965: ‘To place all the scattered pages of earth

history in their proper chronological order is by no means an easy task’. Ordering these pages, and understanding the physical, chemical and biological processes that acted on them since Earth appeared and solidified, requires a detailed and accurate time scale. This deep time

scale is the tool “par excellence” of the geological trade, and insight in its construction, strength and limitations greatly enhances its function and its utility. All earth scientists should understand how the time scale is constructed and how the myriad of physical and numerical data in it are calibrated, rather than merely using the numbers in them, plucked from a convenient wall chart or laminated wallet card.

This calibration to linear time of the succession of events recorded in the rocks on Earth has three components:

  1. The international stratigraphic divisions with correlation in the global rock record,
  2. The means of measuring linear time or elapsed durations from the rock record, and
  3. The methods of joining the two scales, the stratigraphic one and the linear one.

The standard global Geologic Time Scale, version 2020, under the auspices of the Geologic Time Scale Foundation is soon to be published, as researched, written and designed by over 80 scientists worldwide. The litho-bio-chemo-magneto-cyclo-chronostratigraphy and astro- and radiogenic geochronology for the 91 stages in the 538 Ma long Phanerozoic Era has been substantially updated in GTS2020, since the previous standard GTS versions in 2004 and in 2012.

Why a new geologic time scale since 2012:

  • Much improved Precambrian – Phanerozoic stratigraphy with over 30 stage of 91 boundaries changing age of 0.5 – 6 Ma.
  • 72 of 100 Phanerozoic stage boundaries formally defined, versus < 60 in 2012
  • Cenozoic orbitally tuned (20 – 40 kyr accuracy) and detailed cycle scaling in Cretaceous, Jurassic, lower Triassic and Carboniferous
  • Much more accurate and precise age dating with 330 U/Pb and Ar/Ar ages with a majority < 0.5 myr external uncertainty
  • Improved statistical interpolations and more detailed error analysis
  • Sixteen more chapters (now 45) with Phanerozoic Eustasy,

Chemostratigraphy, Evolution/Biostratigraphy and Crustal Events

For the first time, twelve mini ‘Deep Time’ chapters’ outline the state of the art in taxonomy, evolution and biostratigraphy in Trilobites, Graptolites, Conodonts, Chitinozoans, Ammonoides, Plants, Spores and Pollen, Dinoflagellates, Nannofossils, Foraminifers and Microcrinoids. Fundamental new research by Andrew Gale is highlighting the rapid evolution and global correlation in Cretaceous of the fascinating Microcrinoids, well-worth looking for in petroleum well samples.

Two new and fascinating short chapters for GTS2020 deal with Major Evolutionary Radiations and Extinctions and the Influence of Large Igneous Provinces on all fundamental aspects of Earth Science.

Dr. Gabi Ogg is again doing an outstanding job on the publication and artistic layout of the two hefty volumes. We trust that with its digital sister products ‘Time Scale Creator’ and ‘Time Scale Creator Pro’, the Geologic Time Scale 2020 will be of much benefit to the petroleum, academic, cultural and high school educational communities.

Note: Major updates of the standard Geologic Time Scale have now appeared every 8 years, since 2004. This publishing stability is important, bearing in mind that the standard time scale is the result of tight and loyal LONG TERM academic cooperation of stable isotope geochemists, geophysicists and radiogenic isotope experts, an astronomer, a geomathical- statistical specialist and many ‘different discipline’ biostratigraphers, chronostratigraphers and geomagnetic specialists. To maintain this specialist geo-network is vital. What is currently needed for future versions of the standard geologic time, which may lead to a potential more final version of this common deep time scale, is the creation of a burocratic body in Earth

Sciences that controls and communicates standards and conventions. Such a ‘Bureau of Geo- standards’ ultimately will maintain a master and more final version of the standard Global Geologic Time Scale under advise and service of a group of impartial, non-nationalistic scientific specialists. Hence, numeric time scale stability is taken care of to the benefit of science, economy and culture on Earth.

Reference: Felix Gradstein, James Ogg, Mark Schmitz, Gabi Ogg, Jaques Laskar, John McArthur, Bernard Peucker-Ehernbrink, Greg Ravizza, Adina Paytan, Ethan Grossman, Ian Jarvis, Bradley Cramer, Mike Simmons, Ken Miller, Selen Esmeray-Senlet, Richard Ernst, David Bond, Shuan-hong Zhang, Frits Agterberg, Ken Tanaka, Thomas Platz, Rob Strachan, Graham Shields, Galen Halvorsen, Suzanne Porter, Shuai Xiai, Guy Narbonne, Shanchi Peng, Loren Babcock, Per Ahlberg, Dan Goldman, David Harper, Pete Sadler, Steve Leslie, Mike Melchin, Thomas Becker, John Marshall, Anne-Christine da Silva, Marcus Aretz, Hans-Georg Herbig, Xiangdong Wang, Charles Henderson, Zhong Chen, Andrew Gale, Jim Kennedy, Sietske Batenburg, Robert Speijer, Heiko Pälike, Isabelle Raffi, Bridget Wade, Phil Gibbard, Martin Head, Bradley Singer, Jan Zalasiewicz, Colin Waters, Mark Williamson, Anthony Butcher, Maria Rose Petrizzo, Hans Kerp, Gun Mangerud, Robbert S. Gradstein, David Watkins and Dirk Munsterman, in press. The Geologic Time Scale 2020. Elsevier Publishing Co., 2 volumes.

The Geologic Time Scale 2020 flyer (with 30% discount code).