Paleoenvironment of the Morrison Formation in the Bighorn Basin of Montana, USA
Bibliographic record
Abstract
The Morrison Formation is one of the most prolific dinosaur-bearing formations in the world, ranging from the Kimmeridgian-Tithonian in age. Stretching from northern New Mexico throughout much of the western United States and into southern Canada, the units of this Formation have been explored, particularly for dinosaur fossils, since the 1800s (Foster, 2003). However, the majority of research has focused primarily on exposures in Colorado, Utah, and Wyoming, where many of the most famous Jurassic- aged dinosaurs were initially found (Foster et al., 2016). The northern areas of the Morrison, however, have not been thoroughly explored until more recently, and have revealed a mix of unique and relatively common dinosaur species of the Jurassic age (Maltese et al., 2018). An exposure of the Morrison Formation located in the Bighorn Basin of Montana, here referred to as the Suuwassea Morrison Formation Site (SMFS), provides an excellent location to explore and compare to other northern sites within the Morrison Formation, as well as the longer-studied southern areas. In addition to more typical Morrison specimens of apatosaur, stegosaur, and allosaur material, a relatively unique specimen of the sauropod Suuwassea emilieae was initially discovered at this site (Harris and Dodson, 2004). The geology of this site, however, has remained largely unstudied, and the question remains if Suuwassea emilieae is unique to the area due to rarity, temporal differences, or environmental differences restricting its range. The primary goal of this research was determine the local paleoenvironment of the SMFS, particularly in comparison to the rest of the Morrison Formation. In order to accomplish this, I first explored the sedimentology and stratigraphy of the area, describing the sedimentology in detail, with special focus on areas with fossils. In addition, I drafted a detailed stratigraphic column, and identified paleosols, fossils, and photographed localities. I then focused further on the paleosols of the area, with detailed field descriptions, x-ray diffraction analysis, and thin section analysis, to determine the types of soils these profiles originally represented. Based on these data, I conclude the Morrison exposure of the SMFS represents an overall wet, seasonal environment, with fluctuating water tables enhanced by a combination of low base level related to the proximity of this region to the Sundance Sea.
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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 | 0.000 | 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".