Late Cretaceous (Cenomanian to Campanian) Dinoflagellate Cyst Assemblages and Palaeoproductivity Signals from the Kanguk Formation, Sverdrup Basin, Nunavut, Canada
Bibliographic record
Abstract
The response of the polar sea to Cretaceous carbon perturbations is poorly understood and palaeotemperature data from the Arctic are limited.To help understand high latitude palaeoceanographic dynamics, sediment samples containing dinoflagellate cysts (dinocyst) assemblages were collected from a composite Cenomanian to Campanian section from the Bastion Ridge and Kanguk formations within the Sverdrup Basin at Glacier Fiord, Axel Heiberg Island, and at Slidre Fiord, Ellesmere Island.Dinocyst assemblages were compared to recent carbon isotope and benthic foraminiferal age data taken from the same lithographic section.These multiproxy correlations allowed for a more constrained placement of dinocyst biozones, palaeoenvironmental changes, planktic/benthic coupling, and indicate that local age ranges for several Late Cretaceous dinocyst taxa need regional revision within the Sverdrup Basin.At Glacier Fiord a change from a restricted marine to an open marine setting before the Cenomanian/Turonian boundary and a polar expression of the globally recognized OAE 2 is revealed through a turnover in dinocyst and acritarch assemblages, an increase in relative abundance of angiosperm and bisaccate pollen, and an increase in amounts of gelified, dark amorphous organic matter derived from microbial degraded terrestrial material.At Slidre Fiord, depositional settings transition from open marine to deltaic; recognized by an overall increasing sporomorph index trend.Taxa-specific dinocyst peaks are recognized in the Coniacian (Chatangiella sp.), late Santonian (Heterosphaeridium difficile) and middle Campanian (Manumiella sp.).The Coniacian Chatangiella acme is a correlative event across the Canadian Arctic that likely contributed to an increased organic matter supply, causing dysoxic to anoxic benthic redox conditions, which resulted in an increase in the benthic foraminifera This study would not have been possible without the suggestion, supervision and guidance of Dr. Claudia Schröder-Adams.I express my gratitude to Drs.Rob Fensome and Graham Williams who taught me the nuances of dinocyst identification.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".