Depositional and sequence stratigraphic model of transgressive shelf sandstone: The Late Cretaceous Tocito Sandstone, San Juan Bain, New Mexico, U.S.A.
Bibliographic record
Abstract
ABSTRACT There has long been debate about the origin of long, linear, isolated shallow marine sandstones. In the 1980s these were routinely interpreted as wave- or tide-modulated shelf sandstones. With the advent of sequence stratigraphy, many of these sandstones were reinterpreted as top-truncated forced-regressive to lowstand delta or shoreface, inviting the question regarding whether the concept of a shelf sandstones remain a viable depositional model. More recent syntheses demonstrate that shelf sands tend to be derived by reworking of underlying sediment through transgressive erosion and show varying levels of detachment and reworking into discrete ridges and bars by wave and tidal processes as they become more evolved. The Late Cretaceous Tocito Sandstone in the Western Interior Seaway, which overlies the regressive Gallup Formation, is a candidate for a transgressive shelf sandstone. In this study, we present detailed facies analysis, based on sedimentological sections measured from well-exposed outcrops of the Tocito Sandstone and its related stratigraphic units in northwest New Mexico, USA. With high-resolution sequence stratigraphic control, facies analysis, detrital-zircon anatomy, and petrographic analysis are integrated to investigate the sequence stratigraphic evolution and depositional processes of the Tocito Sandstone. Detrital zircons indicate that the Tocito, Torrivio, and Gallup deposits are derived from different source areas, and therefore imply separate sequence stratigraphic origins. The Tocito Sandstone is interpreted to have been deposited as shelf sand ridges in retrogradational estuarine to drowned-barrier-system environments with tidal and wave influence, characterized by intense bioturbation. The Tocito was deposited in an overall transgressive systems tract and sourced from reworking of the underlying Torrivio and Gallup units through processes of transgressive erosion.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".