Rethinking the “Grenville Flood” of Laurentian detrital zircon: Proximal sources, not continental rivers
Bibliographic record
Abstract
Abstract The widespread presence of Mesoproterozoic detrital zircon in western Laurentia has long been interpreted as evidence for transcontinental river systems transporting sediment from the Grenville orogen. This model asserts that Grenville-age zircon were carried across Laurentia during the Neoproterozoic and Paleozoic, but recent isotopic and provenance data challenge this interpretation. Here, we show that detrital zircon age distributions and Hf isotopic compositions east and west of the Transcontinental Arch remained distinct until the late Paleozoic, inconsistent with repeated sediment mixing by a long-lived transcontinental river system. Instead, multiple Stenian magmatic sources in western Laurentia, including the Llano Uplift, Pikes Peak batholith, and the Southwestern Laurentia Large Igneous Province, provide plausible proximal sources of zircon. Additionally, the Pearya terrane, the northern Yukon, and formerly adjacent Antarctic crust may have contributed detrital zircon to western Laurentia’s sedimentary record. Post-Devonian sediment redistribution may have been accomplished by a combination of fluvial, shallow marine, and eolian processes, or indirect sediment routing. These findings suggest that late Paleozoic processes, rather than a Proterozoic transcontinental river(s), were responsible for distributing Grenville-age zircon across Laurentia. This revised model fundamentally alters the prevailing understanding of sediment routing in deep time and highlights the importance of reevaluating long-assumed geodynamic and provenance frameworks.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".