The varved sediment succession of Crawford Lake, Ontario, Canada: GSSP for the proposed Anthropocene Epoch 
Bibliographic record
Abstract
The Crawford Lake sedimentary sequence in Milton, Ontario, Canada, has been chosen as the Global Boundary Stratotype Section and Point (GSSP) for the proposed Anthropocene Series/Epoch, with its inception occurring at 1952 CE in the mid-20th century. This sequence consists of seasonally deposited layers of organic matter capped by summer-deposited calcite, forming in alkaline surface waters when pH and temperature rise above 7.76 and ~15°C, respectively. These sediments preserve a range of proxies that mirror environmental shifts spanning from local, to regional, global scale, indicative of the Anthropocene's onset. Notably, a significant uptick in industrial fossil fuel combustion in the early 1950s is recorded by increased spheroidal carbonaceous particles and a shift in the sediment's nitrogen isotope composition. During the 1960s, the ratios of 239Pu:240Pu and 14C:12C peak, aligning with heightened radioactive fallout from atmospheric nuclear weapons testing, counterbalancing the old carbon effect in Crawford Lake's dolomitic basin. Post-World War II industrial growth in the Great Lakes region, part of the so-called Great Acceleration, led to acid rain that diminished calcite deposition and impacted primary productivity in the lake. This change is reflected in thinner calcite layers concurrent with the proposed GSSP. These varve thickness variations correlate with climate patterns and lake productivity trends, influenced by cycles like the Quasi-biennial Oscillation, El Nino-Southern Oscillation, the 11-year Schwabe sunspot cycle, and the Pacific Decadal Oscillation. The absence of pigments from anaerobic purple sulfur bacteria suggested an oxygen-rich monimolimnion but with elevated bottom-water salinities that was subsequently confirmed by water property data collected through the modern lake water column in all seasons. Such an aerobic depositional environment is highly atypical for a meromictic lake and it was the elevated alkalinity and higher salinity conditions that resulted in preservation of varves. The oxygenated bottom waters serendipitously prevented the mobilization of 239Pu in the lake sediments, a key primary stratigraphic marker for the Anthropocene.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.004 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.009 | 0.001 |
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".