Near Annual-Scale (1925-1985) Diatom Paleoecological Succession in Crawford Lake, Ontario: A Candidate Site for the Anthropocene Epoch Global Boundary Stratotype Section and Point (GSSP)
Bibliographic record
Abstract
The newly proposed Anthropocene Epoch, with a time stamp set in the mid-20 th century, is based on the recognition that human induced environmental influences are distinct enough to be preserved in the geologic record.New geologic units require establishment of a Global Boundary Stratotype Section and Point (GSSP), with many sites around the world being considered as the GSSP for the Anthropocene Epoch.The excellent record of a Holocene-Anthropocene boundary preserved in Crawford Lake, near Milton, ON, is a leading Anthropocene Epoch GSSP candidate and as such requires extensive multidisplinary research if it is to be designated as such.There is considerable evidence to support the unique nature of Crawford Lake as a leading Anthropocene GSSP contender, including it being a protected site, with preserved laminae in the benthic sediments, and evidence indicative of 1950s nuclear testing.Diatoms have been used as bioindicators for freshwater lakes since the early 1900s and can be used to develop a long-term baseline regarding the health of a lake.To help detect any changes before and after the start of the Anthropocene in the early 1950s, diatoms were analyzed at a near-annual resolution from 1925-1985.Statistical diatom analysis revealed four assemblages and two subassemblages that characterized distinct depositional intervals through the 1925-1985 interval, with the second assemblage being broken up into two sub-assemblages: Assemblage 1 (1925-1942), Assemblage 2a (1943-1951), Assemblage 2b (1952-1959), Assemblage 3 (1960-1971), and Assemblage 4 (1972-1985).Populations shifted from predominantly centric planktic species in Assemblage 1, to an araphid Fragilaria-dominant Assemblage 2. A notable increase in specimen numbers was seen from Assemblage 2a to Assemblage 2b, which lines up with the beginning of the "Great Acceleration" that occurred in the late 1940s and early 1950s.A partial recovery of the centric community that included species such as Cyclotella distinguenda and Lindavia bodanica was seen in Assemblage 3. Assemblage 4 saw another decline in centric planktic species and the establishment of Fragilaria spp., representing littoral attached, and benthic taxa.Based on the population increases seen in the late 1940s and early 1950s, as well as the fluctuations seen in the
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".