Angiosperm leaves and other plant fossils from the Lower Cantwell Formation, Denali National Park Alaska—Implications for a Late Cretaceous paleoecology and climate in Interior Alaska - Abstract
Bibliographic record
Abstract
Landscape and climate associations can be made on the basis of sedimentological and paleoecological information. In the summer of 2006, a series of dinosaur footprints, fossilized leaves and wood, and a variety of invertebrate tracks were discovered in the Sable Mountain and Double Mountain areas in the Lower Cantwell Formation in Denali National Park (Fiorillo et al., 2006). This Campanian/Maastrichtian (Ridgway et al., 1997) formation has the unique quality of being the only non-marine sedimentary unit in Interior Alaska and, as such, harbors valuable information about transient environmental conditions and forms of life for this time. The recent discoveries of hadrosaur and theropod footprints in the Lower Cantwell Formation (Fiorillo et al., 2006) show that biologic productivity was sufficient to create the habitats that these large creatures required. The appearance of leaves is a sign of the arrival and establishment of deciduous angiosperm shrubs and trees in Interior Alaska. Preliminary results from the study of a limited number of specimens show that the leaves appear to correspond to some of the older Cenomanian specimens described by Spicer (1987), Spicer and Parrish (1990), and Spicer and Herman (2001) from the North Slope and the Yukon-Koyukuk Basin. Accordingly, the Cantwell Formation bears several different kinds of hamamelid platanoid forms some of which show acrodromous venation patterns. These leaves were grown by small trees and shrubs that coexisted with the small-leafed deciduous conifer Metasequoia, equisitites and ferns. Climate deteriorated drastically in the Maastrichtian on the North Slope resulting in a floral turnover during which diversity declined and angiosperms disappeared (Spicer and Parrish, 1990). By comparison platanoid-leafed plants continued to thrive in the ancient Cantwell Basin. Metasequoia fossils dominate the stream deposits while angiosperm shrubs and trees appear to have grown on more elevated parts of the floodplain. Leaves show no signs for a lesser, more primitive organization of veins and although only a few specimens have been found so far, we may yet conclude that diversity was less adverse affected and that the Late Cretaceous cooling trend recorded from the North Slope was much less pronounced for this part of Alaska.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".