Thermal History of the Frontenac Arch in Southeastern Ontario, Canada Constrained From Low-temperature Thermochronology
Bibliographic record
Abstract
The Frontenac Arch is an intraplate low-relief ridge of Precambrian rocks that connects the southeastern Ontario part of the Canadian shield with the Adirondack Massif in New York State. The NW-SE trending ridge is oriented perpendicular to the major tectonic fabric of the Grenville, Appalachian, and St Lawrence rift systems. This thesis research aims to understand the building mechanism(s) and timing of this basement topography. New apatite and zircon (U-Th)/He and apatite fission track data from 19 samples collected along three transects in the Frontenac Arch provide cooling ages ranging from 183.7 - 19.5 Ma (AHe), 196.2 - 109.6 Ma (AFT), and 732.5- 144.1 Ma (ZHe). The T-t paths for the Frontenac Arch define a thermal history dominated by one stage of progressive cooling since the post-Shawinigan phase of the Grenville Orogeny (~1140 Ma) to surface temperatures by ~525 Ma after the culmination of the breakup of Rodinia. This is followed by sediment burial (~ 3-4 km) and reheating to ~160 °C with heating peaks at different times during the Paleozoic resulting in partial resetting of the ZHe dates, and a third cooling stage (0.3-0.5 °C/Ma ) starting during the breakup of Pangea and opening of the Atlantic Ocean in the Early Mezosoic. \nThe last pulse of cooling in the thermal models between 175-225 Ma coincides with Mesozoic normal fault reactivation documented through AFT age discontinuities in the St. Lawrence and Saguenay fault system at ca. 200 -250 Ma caused by NW-SE extension and breakup of Pangea. A younger faulting event resulting in differential exhumation is likely recorded in the Frontenac Arch along the NE-trending Rideau-Lake normal Fault between 150-190 Ma. A period of differential unroofing started at least since the Late Cretaceous and eroded most of the Early Paleozoic sediments left in the last 120 Ma, as recorded by Devonian clasts in Cretaceous diatremes and kimberlites in Montreal and Lake Timiskaming, respectively.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.013 | 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 teacher head, 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".