Stratigraphy of the Middle to Upper Ordovician foreland-basin succession, Ottawa Embayment: emphasis on the Turinian-Chatfieldian succession
Bibliographic record
Abstract
New contributions are presented concerning the character of the depositional systems and stratigraphic architecture of the Middle to Upper Ordovician foreland-basin succession, and in particular the Turinian-Chatfieldian succession, that underlies the Ottawa Embayment, central-east Canada.The Ordovician foreland succession is the local expression of the cratonic Tippecanoe I Megasequence that extends across southern Laurentia, and developed within a retro-arc basin arising from distal plate-boundary convergence.This study investigates craton-interior intrabasinal response of sedimentation to tectonic, climatic, depositional and eustatic controls, and compares the basin's stratigraphic fabric with equivalent strata along strike, to the south, in the much larger Appalachian Basin.The embayment's foreland stratigraphy is divided into platform and basin successions: in ascending order, seven (I-VII) transgressive-regressive (T-R) depositional sequences and one (VIII) transgressive sequence comprise a Middle to Upper Ordovician (Dariwillian to Edenian) platform succession whereas an incomplete regressive sequence (IX) forms the basin succession (Edenian through Richmondian).Combined, they define a tectonic cycle of net platform deepening over ~15 my and subsequent basin-fill spanning ~3 my.Thisasymmetry characterizes the local expression of diachronous foundering of the regional southern Laurentian margin related to orogen migration and erosion, then basin fill.My study reaffirms placement of the Sauk-Tippecanoe I (S-T) Megasequence boundary within the upper Beekmantown Group: it is timed with significant synsedimentary structural events that appear to predate regional regression, then flooding, previously v formation-specific 13 C excursions suggest local modulation of regional (or global) 13 C excursions in response to changes in circulation, productivity, and accumulation rates.In summary, when compared to laterally equivalent sedimentary basins in southern Laurentia, the Middle to Upper Ordovician foreland succession of the Ottawa Embayment illustrates elevated syndepositional structural control on sedimentation.This is likely a far-field response to contemporary changes in subsidence rates and tectonic events along the distal convergent Laurentian plate, that were focused into the craton interior along an axis of inherited weakened continental crust defined by a late Precambrian intracratonic fault system that underlies the embayment.Tectonism played an important role in influencing higher order base-level changes along this part of the Laurentian platform that were superimposed on an otherwise net eustatic rise through the Middle and Late Ordovician.vi
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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 | 0.001 | 0.001 |
| 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 | 0.000 |
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".