Gas hydrate occurrences along the Haida Gwaii margin—Constraints on the geothermal regime and implications for fluid flow
Bibliographic record
Abstract
Abstract Seismic-reflection data along the Haida Gwaii margin collected from 1967 to 2013 were used to identify gas hydrate–related bottom-simulating reflectors (BSRs). The BSRs occur along the Queen Charlotte Terrace only, within more strongly folded and tectonically deformed sedimentary ridges. The BSRs are absent within well-bedded and sediment-filled minibasins. The BSR is modeled as the base of the phase boundary of the methane hydrate (structure I) stability zone and is used to estimate geothermal gradients. The P-wave velocity structure required to convert observed depths of the BSR in two-way time to meters below seafloor was constrained from ocean-bottom seismometers. The BSR-derived gradients are lower than data from heat-probe deployments in the region, as well as predicted values from previous modeling of the large-scale tectonic thermal regime. Lower values of the BSR-derived thermal gradients may be due to topographic effects across the ridges where BSRs were observed. The previously identified landward decrease in thermal gradients across the terrace was also identified to a lesser extent from the BSRs, in accordance with the effects of oblique convergence of the Pacific plate with the North American plate. Geothermal gradients decreased from south to north by a factor of two, which is likely an effect of plate cooling due to an increase in age of the underlying plate (ca. 8 Ma off southern Haida Gwaii to ca. 12 Ma at Dixon Entrance) as well as the fact that sediments triple in thickness over the same distance. This may be due to downward flexure of the underlying crust during transpression and/or a high flux of sediments through Dixon Entrance.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| 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".