Controls on facies variability and distribution during the Pennsylvanian glacial period from the lower Strawn Group, Fort Worth basin, Texas
Bibliographic record
Abstract
Abstract The lower Strawn Group (Desmoinesian) in Jack and Wise Counties of the Fort Worth basin, Texas, comprises laterally and vertically heterogeneous deltaic to shelfal deposits that include sandstone, siltstone, and shale, with thin, discontinuous carbonate and coal seams that reflect variable icehouse condition controls on sedimentation and facies distribution. This study highlights the relationships between component facies of the lower Strawn Group by defining five distinct depositional environments in core, develops a high-resolution stratigraphic framework consisting of 11 regressive–transgressive cycles, and identifies depositional controls on stratal characteristics to improve reservoir predictability. Depositional environments of the lower Strawn Group include prodelta, medial delta front, interdistributary bays, channel-mouth bars, and distributary channels. These environments, their wire-line log patterns, and facies relationships indicate dominantly fluvial-driven deltaic depositional systems. Wire-line log correlations using regionally extensive maximum flooding surfaces provide the basis of a stratigraphic framework identifying 11 regressive–transgressive, fluvio-deltaic sequences each between 90 and 240 ft (27 and 73 m) thick, with an overall thickness ranging between 1000 and 2700 ft (305 and 823 m), and progradation of the deltas to the south-southwest. The depocenters of these sequences are similar in size and geometries to modern analogues that include select parts of the fluvio-deltaic systems of the Mississippi and Yukon Rivers, with primary depocenters ranging from 8 to 25 mi (13–40 km) in lateral extent. This study provides improved predictability for targeting hydrocarbons in the Strawn Group and analogous systems in the Fort Worth basin through high-resolution mapping and identification of elevated porosity trends in homogeneous channel-mouth bar and distributary channel deposits.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.017 | 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 teacher head, 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".