New U-Pb detrital zircon ages from the Upper Cambrian – Lower Ordovician Cow Head Group in the Humber Arm allochthon, Western Newfoundland: continental-scale drainage, local deformation, and global stratigraphy
Bibliographic record
Abstract
The Cambro-Ordovician Cow Head Group is an allochthonous sedimentary succession situated in the Humber zone of Western Newfoundland, the westernmost outer domain of the Appalachian orogenic belt in North America. It records submarine carbonate and rare siliciclastic deposits on a fault-bounded basin Laurentian margin shelf. It is characterized by interstratified carbonate conglomerate, mudstone, grainstone, packstone, wackestone, and lime mudstone. Mega-conglomerate along the Cambro-Ordovician boundary with anomalously coarse clasts are attributed to slope failure of the adjacent carbonate platform. While most authors agree that the transport and deposition of mega-conglomerate was related to seismicity and slope failure, their sedimentation have also commonly been linked to eustatic regression.To try and better understand the tectonic vs. eustatic forces driving the stratal evolution of the Cow Head Group, detrital zircon U-Pb ages were obtained from the Furongian Tuckers Cove and coeval Martin Point members of the Cow Head Group, and used to better constrain the tectonic, eustatic, and stratal evolution of the Laurentian passive margin. The Tuckers Cove Member is particularly significant due to its record of quartz sand influx into an otherwise carbonate- and mud-dominated basin, and because it underlies megaconglomerate sedimentation linked to terminal Cambrian faulting. Moreover, its sedimentation was coeval with the Furongian Steptoean positive carbon isotope excursion (SPICE), and with shelf regression and the delivery of quartz sand documented in otherwise carbonate-dominated intracratonic basins throughout Laurentia, including in central Iowa, Utah, and coeval shelf carbonates in Western Newfoundland. Such a correlation is supported by preliminary detrital zircon U-Pb results from the Tuckers Cove and Martin Point members, revealing a mixture of typical Laurentian cratonic populations including Archean (ca. 2.73 Ga), Paleoproterozoic (ca. 1.9 Ga), Mesoproterozoic (ca. 1.1 Ga), and Neoproterozoic (ca. 593 Ma) detrital zircons. This implies continental-scale erosion and sediment flux, with sediment sourced from a widespread Laurentian cratonic catchment during the Furongian, including Archean and Proterozoic sources like the Superior, Makkoviak and Grenville provinces, and Ediacaran rift-related strata from the western Newfoundland - Quebec Appalachians. At present these zircon data do not resolve tectonic versus eustatic controls on Cow Head Group sedimentation. Nevertheless, they validate the concept of continental-scale weathering, drainage, and clastic sedimentation across Laurentia during the Furongonian. More work is needed to understand the relationship between such punctuated and widespread sediment generation and Late Cambrian plate tectonics, eustasy, and SPICE.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| 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 | 0.001 |
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".