High-resolution analysis of the varved succession at Crawford lake across the base of the proposed Crawfordian stage and Anthropocene series

Four years after the Anthropocene Working Group (AWG) voted to work toward defining the Anthropocene series/epoch with a base in the mid-20th C, the varved sediments of Crawford Lake (Milton, ON, Canada) were selected as the Global boundary Stratotype Section and Point (GSSP) candidate. The initial major rise in activity of 239 + 240 Pu had been selected as the primary chronostratigraphic marker to define the base of the Anthropocene, but the precise year when this occurred could not be determined from measurements of samples combining multiple varves. Individual varves from freeze cores collected in April 2023 provide annual resolution for bomb radionuclides, allowing the varve age model to be refined, former assignments determined to have been 1 year too old. The increase in 239 + 240 Pu activities (calculated from atom concentrations of 239 Pu and 240 Pu measured using Accelerated Mass Spectrometry) of 0.0031 Bq/g between varves now assigned to 1951 and 1952 is consistent with the onset of thermonuclear weapons testing on November 1, 1952, so the proposed base for the Anthropocene is at the contact between the light- and dark-coloured laminae deposited in 1952 CE (17.5 cm in core CRA23-BC-1F-B). Sharply lower 239 + 240 Pu and 137 Cs activities capture the moratorium from November 1958 to September 1961 before rising quickly to peak activities of 239 + 240 Pu in 1963 CE. Analysis of individual varves with varying amounts of organic matter and inorganic calcite illustrates the influence of lithology on organic proxies, but the upcore trend toward depleted values of δ 15 N through the 20th C reflects increased fossil fuel combustion worldwide. An inflection point in δ 15 N around 1911 CE is attributed the global impact of the Haber-Bosch process and establishment of nearby steel mills, and another in the early 1950s attributed to the Great Acceleration to which the tipping point in the Earth system is attributed

Anthropocene · Chronology · Geochemistry · Geography · Global Boundary Stratotype Section and Point · Interglacial · Marine isotope stage · Physical geography · Quaternary · Radiometric dating · Sediment · Series (stratigraphy · Stage (stratigraphy · Stratotype · Varve · Isotope Analysis in Ecology · Radioactive contamination and transfer · Radioactivity and Radon Measurements · Geology · Paleontology

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  Open Access•R Carroll, G E Jacobsen et al.•Anthropocene•2026

  Incluir item

• Understanding the end of the Holocene

  Open Access•Mohammed H Dore, M Rosario Marín et al.•The Anthropocene Review•2026

  Incluir item

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  Open Access•Samuel R Ribeiro•Anthropocene•2026

  Incluir item

• Historical developments of Anthropocene concepts

  Open Access•R N Spengler•Quaternary International•2026

  Incluir item

• Response to Damianos—Anthropocene angst

  Open Access•Colin N Waters, J Zalasiewicz et al.•Social Studies of Science•2025

  Incluir item

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  Open Access•Jeremy Davies•The Anthropocene Review•2025

  Incluir item

• A Possible Varving Mechanism for Meromictic Lakes

  Open Access•M Dickman, M D Dickman•Quaternary Research•1979

  Incluir item

• Fungal spores record Iroquoian and Canadian agriculture in 2nd millennium a.d. sediment of Crawford Lake, Ontario, Canada

  Open Access•John H Mcandrews, Charles L Turton•Vegetation History and…•2010

  Incluir item

• Siliceous algae response to the “Great Acceleration” of the mid-20th century in Crawford Lake (Ontario, Canada)

  Open Access•Cale Ac Gushulak, Matthew Marshall et al.•The Anthropocene Review•2021

  Incluir item

• The Anthropocene

  Will Steffen, Paul J Crutzen et al.•AMBIO•2007

  Incluir item

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  Open Access•Francine Mg Mccarthy, Francine M G Mccarthy et al.•Anthropocene•2018

  Incluir item

• Humans and technology in the Anthropocene

  Open Access•Peter Haff, P K Haff•The Anthropocene Review•2014

  Incluir item

• Candidate sites and other reference sections for the Global boundary Stratotype Section and Point of the Anthropocene series

  Open Access•Colin N Waters, D Turner et al.•The Anthropocene Review•2023

  Incluir item

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  Open Access•Yongming Han, Zhaolong An et al.•The Anthropocene Review•2023

  Incluir item

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  Open Access•Barbara Fiałkiewicz-Kozieł, Edyta Łokas et al.•The Anthropocene Review•2023

  Incluir item

• Evidence and experiment

  Open Access•Christoph Rosol, Gary N Schafer et al.•The Anthropocene Review•2023

  Incluir item

• Beppu Bay, Japan, as a candidate Global boundary Stratotype Section and Point for the Anthropocene series

  Open Access•Michinobu Kuwae, B Finney et al.•The Anthropocene Review•2023

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  Open Access•Francine Mg Mccarthy, Robert T Patterson et al.•The Anthropocene Review•2023

  Incluir item

• The trajectory of the Anthropocene

  Open Access•Will Steffen, Wendy Broadgate et al.•The Anthropocene Review•2015

  Incluir item