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Communication of IUGS Geological Standards

Episodes 2024; 47(2): 381-389

Published online June 1, 2024


Copyright © International Union of Geological Sciences.

Ratification of the base of the ICS Geological Time Scale: the Global Standard Stratigraphic Age (GSSA) for the Hadean lower boundary

Jaana Halla1*, Nora Noffke2, Humberto Reis3, Stanley Awramik4, Andrey Bekker5, Alexander Brasier6, Flávia Callefo7, Adrita Choudhury8, Jan-Peter Duda9, Christopher Fedo10, Douglas Galante11, Jessica Haddock2, Peter Haines12, Linda Hinnov13, Axel Hofmann14, Martin Homann15, David Huston16, Simon Johnson12, Linda Kah10, Alan Kaufman17, Alex Kovalick5, Matheus Kuchenbecker18, Juha Köykkä19, Donald Lowe20, Noah Nhleko21, Barry Reno22, Evelyn Sanchez18, Yogmaya Shukla8, Albertus Smith14, Mark Van Zuilen23, Frances Westall24, Martin Whitehouse25

1 Finnish Museum of Natural History, Jyrängöntie 2, 00014 University of Helsinki, Finland
2 Old Dominion University, Ocean and Earth Sciences, 4600 Elkhorn Avenue, Norfolk, VA 23529, USA
3 HR Consulting Energy and Geosciences Ltda. Rua Leopoldina, Santo Antonio, Belo Horizonte, Minas Gerais, Brazil – ZIP code 30330-230
4 University of California, 1210 Cheadle Hall Santa Barbara, CA 93106-2014
5 University of California Riverside, 900 University Ave, Riverside, CA 92521, USA
6 University of Aberdeen, Meston Building, King’s College, Aberdeen AB24 3UE, UK
7 University of Campinas, Cidade Universitária Zeferino Vaz - Barão Geraldo, Campinas - SP, 13083-970, Brazil
8 Birbal Sahni Institute of Palaeobotany, 53, University Rd, Babuganj, Hasanganj, Lucknow, Uttar Pradesh 226007, India
9 University of Göttingen, Geoscience Center, Department of Geobiology, Goldschmidtstr. 3, 37077 Göttingen, Germany
10 The University of Tennessee, Knoxville, TN 37996, USA
11 Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, Cidade Universitária, São Paulo, ZIP code 05508-080, Brazil
12 Geological Survey of Western Australia, Mineral House, 100 Plain Street, EAST PERTH WA 6004, Australia
13 Johns Hopkins University, Baltimore, Maryland 21218, USA
14 University of Johannesburg, APK-campus, Rossmore, Johannesburg, 2092, South Africa
15 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, 91125 California, USA
16 Geoscience Australia, 101 Jerrabomberra Ave, Symonston ACT 2609, Australia
17 University of Maryland, College Park, Maryland 20742, USA
18 Universidade Federal dos Vales do Jequitin e Mucuri, R. Cruzeiro, 01 - Jardim Sao Paulo, Teófilo Otoni - MG, 39803-371, Brazil
19 Geological Survey of Finland, Vuorimiehentie 5, 02151 Espoo, Finland
20 Stanford University, 450 Jane Stanford Way, Stanford, CA 94305, USA
21 Swaziland Geological Survey and Mines Department, P.O. Box 57, Mbabane, Eswatini
22 Northern Territory Geological Survey, Level 3 Paspalis Centrepoint, 48-50 Smith Street, Darwin, Australia
23 CNRS Orleans Campus Centre de Biophysique Moléculaire (CBM), Rue Charles Sadron, 45071, Orléans, France
24 Institut de physique du Globe de Paris, 1 Rue Jussieu, 75005 Paris, France
25 Swedish Museum of Natural History, Frescativägen 40, 114 18 Stockholm, Sweden

Correspondence to:*E-mail: jaana.halla@helsinki.fi

Received: December 13, 2023; Revised: January 30, 2024; Accepted: January 30, 2024

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.


The base of the ICS (International Commission on Stratigraphy) Geological Time Scale was ratified in 2022 by defining a new Global Stratigraphic Standard Age (GSSA) for the lower boundary of the Hadean Eon (formerly 4000–3600 Ma); the age of the Solar System based on the oldest solids, calcium-aluminium inclusions (CAIs), generated in the protoplanetary disk. The formal GSSA for the Hadean base is the oldest reliable, weighted mean Ucorrected Pb–Pb age of 4567.30 ± 0.16 Ma obtained for CAIs in primitive meteorites Allende and Efremovka. This age is supported by the 4568–4567 Ma U-corrected Pb–Pb ages of chondrules in Northwest African meteorites. The boundary sets an upper lifetime for the protoplanetary disk and timing of planet formation. The Hadean Eon encloses the accretion and differentiation of the Earth and other planets, the Moon-forming Giant Impact, the beginning of the suggested Late Heavy Bombardment, and the formation of the Earth’s protocrust. Due to the Moon-forming Giant Impact that occurred after the differentiation of the proto-Earth and the fact that Earth’s first crust has been destroyed, the age of the planet Earth itself remains an open question. However, many pieces of astronomical, chemical, physical, and chronological evidence point to the very fast formation of the Solar System and rapid accretion and differentiation of the proto-Earth in only a few million years. Compared to the half-billion-year duration of the Hadean, it is reasonable to set the age of the Earth at the beginning of the formation of the Solar System. This communication explains and justifies the selection of the GSSA for the Hadean base.