Morphology, petrography, age and origin of the Fogo Seamounts, eastern Canada
Bibliographic record
Abstract
The Fogo Seamounts are located approximately 500 km offshore from Newfoundland to the southwest of the Grand Banks of Newfoundland. This complex seamount chain is Early Cretaceous in age and is partially buried under later continental slope deposits. The seamounts are developed along the northeastern transform margin of the Jurassic central Atlantic Ocean. The Narwhal F-99 well was drilled in 1986 on the continental slope into one buried seamount. In this study, we have compiled unpublished data on the bathymetry, seismic-reflection character, and distribution of the Fogo Seamounts and interpret new petrographic, geochemical and geochronological data from a dredge sample from seamount G in the central part of the seamount chain and from the Narwhal F-99 well. Petrographically, the seamount samples consist of vitrophyric basalt, with clinopyroxene at Narwhal and kaersutite in the dredge sample. Chemically, the samples are olivine basalt with a low Mg number and low concentration of transition metals. Trace element and REE abundances are similar to those of other early Cretaceous volcanic rocks on the southeast Canadian margin, except that LILE are more enriched in basalts on the continental shelf. Sm/Nd isotopes suggest mantle derivation, with ,Nd ranges from 2.3 to 4.7. Overall, the Narwhal basalts are more tholeiitic whereas the basalts at seamount G are more alkalic, showing OIB characteristics, and their range of compositions is well matched by basalts from Hawaii. The dredge sample at seamount G gave a 40Ar/39Ar age of 130.3 ± 1.3 Ma on kaersutite (top Hauterivian on the Gradstein et al. 2004 time scale). A K/Ar age from the Narwhal F-99 well of 127 ± 6 Ma is inconsistent with biostratigraphic zonation, which shows that sedimentary rocks overlying basalt in the well are at least as old as early Berriasian (ca. 145 Ma). Seismic reflection profiles show that a series of coastal transgressions can be recognised above the basalt, with final submergence probably in the Berriasian. Distribution of the seamounts, based on bathymetry and in the case of buried seamounts, magnetic and seismic data, shows that there is no clear linear trend, but rather a broad zone within which seamounts have formed. New bathymetric data shows that flat tops to seamounts, resulting from coastal erosion prior to subsidence and platform carbonate deposition, show no systematic pattern. The broad extent of the seamounts on the margin probably results from the influence of a series of upper crustal faults along the transform margin.
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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 | 0.002 |
| Science and technology studies | 0.002 | 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) | 0.002 | 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".