Detrital zircon evidence for Paleoproterozoic West African crust along the eastern North American continental margin, Georges Bank, offshore Massachusetts, USA
Bibliographic record
Abstract
Basement rocks from the Continental Offshore Stratigraphic Test (COST) No. G-1 petroleum exploration well, Georges Bank, offshore Massachusetts, USA, show the first direct evidence for a fragment of Paleoproterozoic West African crust preserved along the eastern North American continental margin. Detrital zircon from two metawacke samples near the base of the core yielded ca. 3.05–1.90 Ga laser ablation–inductively coupled plasma–mass spectrometry dates, with a predominant 2.2–2.0 Ga population. This detrital zircon signature is consistent with that in the Taghdout Group of the Anti-Atlas region, which is part of the Paleoproterozoic passive margin rocks deposited directly on the Archean–Paleoproterozoic WAC shortly after its formation. African provenance has previously been recognized for the Suwannee and Meguma terranes in the southern and northern Appalachians, respectively. However, these areas represent Neoproterozoic–Paleozoic sedimentary basins, deposited well over a billion years after formation of the Paleoproterozoic WAC and cover rocks, including those in the COST No. G-1 well. The Paleoproterozoic rocks in the COST No. G-1 well were likely amalgamated with the North American margin during final closure of the Rheic Ocean and assembly of Pangea near the end of the Paleozoic.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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 teacher head, 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".