Exhumation and fluid flow history of the eastern Denali fault zone, Yukon, Canada, from multi-method thermochronometry
Bibliographic record
Abstract
Reconstructing the spatial and temporal patterns of deformation along fault zones is a critical component of understanding the long-term evolution and seismic hazard of major faults. The ~2,000-km-long Denali fault zone (DFZ) extends from the Bering Sea, through south-central Alaska, and into Yukon, Canada. The 2002 Mw 7.9 earthquake on the DFZ indicates there are significant modern seismic hazards. We examine the timing, tempo, and spatial variation of rock exhumation within the DFZ-bounded Kluane Range in southeastern Yukon with new and previously published low-temperature thermochronology data from different locations and elevations within a zone of DFZ-related distributed deformation. Zircon (U-Th)/He (He), apatite fission-track, apatite He, and hematite He thermochronometers record exhumation from depth and cooling through temperatures of 220-20 °C, 120-80 °C, and 90-30 °C, and 250-25 °C, respectively. All thermochronometric dates increase in a non-linear fashion with distance from the modern-day trace of the DFZ. The youngest dates from the highest temperature thermochronometers are immediately adjacent to the DFZ. Thermal history models of thermochronometric dates suggest episodes of apparent rapid cooling in the Cretaceous and Late Oligocene. Cretaceous cooling is temporally coincident with documented magmatism and contractional tectonism in the area and likely reflects rapid post-magmatic cooling and/or accelerated exhumation. Spatial patterns of thermochronometric dates require a ≥2x increase in the magnitude of Late Oligocene differential exhumation over a ≤3 km-width zone. Alternatively, date patterns may be explained by localized circulation of hydrothermal fluids that perturbed and variably reset thermochronometric dates adjacent to the fault. Brittle faults within this locality exhibit evidence for extensive fluid flow and hematite mineralization, supporting this notion. Hematite He dates from fault surfaces hosted within this zone suggest fluid circulation may have occurred at ~7 Ma, in-tandem with fault activity. Ongoing apatite, zircon, and hematite He dating will further test and refine this hypothesis.
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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 | 0.002 |
| 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) | 0.001 | 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".