Refining the depositional model of the lower Permian Carynginia Formation in the northern Perth Basin: anatomy of an ancient mouth bar
Bibliographic record
Abstract
The late early Permian coincided with a short-lived cold episode in Western Australia, which occurred long after the demise of late Paleozoic ice sheets, and is manifested by conspicuous dropstones in corresponding marine strata. In the northern Perth Basin, this time interval is represented by the Carynginia Formation, which has long been regarded as a record of low-energy marginal-marine sedimentation. The low-diversity body-fossil content and impoverished trace-fossil assemblages in the formation were recognised as evidence of low salinities, low dissolved-oxygen levels and high suspended-sediment concentrations presumably related to freshwater influxes into a restricted basin. However, sedimentary facies indicative of river processes have yet to be documented to explain the sedimentological and paleontological character of the formation. This study examines an overlooked sandstone-rich interval of the Carynginia Formation in the Irwin Sub-basin, a marginal half graben faulted against crystalline basement of the Yilgarn Craton and forming part of a series of late Paleozoic intracratonic rift basins in Western Australia. Facies analysis indicates that the lower part of the interval is dominated by storm-generated deposits containing extraformational pebbles and boulders. These deposits are interpreted as recording lower-shoreface sedimentation under the influence of seasonal sea ice, and constitute a shallower, sandstone-rich equivalent of mudstone-prone strata that otherwise characterise the Carynginia Formation. The upper part of the interval consists of river-borne deposits representing friction-dominated deposition of a river-mouth bar, the first direct record of deltaic sedimentation in the Carynginia Formation. The stratal organisation of mouth-bar bedsets is likely the result of successive sediment-laden pulses related to seasonal floods in a shallow marine basin, and the autogenic evolution of the mouth-bar complex in response to fluctuating river discharge and compensational stacking. Formative runoff events were arguably responsible for reductions in salinity and the introduction of turbid buoyant plumes into the shallow sea that were adverse to faunal development. A fluvial influence may explain the sedimentary character and fossil content of coeval mudstone-prone formations in Western Australian rift basins, especially in the vicinity of cratonic margins.KEY POINTSThe lower Permian (late Artinskian–Kungurian) mudstone-prone Carynginia Formation in the northern Perth Basin has long been regarded as the record of low-energy, marginal-marine conditions in a cold-water seaway.The low-diversity fossil content in the lower part of the formation indicates stressed physico-chemical conditions influenced by freshwater, sediment-laden influxes.The described mouth-bar deposits are the first direct evidence of deltaic sedimentation in the Carynginia Formation, demonstrating that river outflows likely controlled water chemistry and impacted faunal development.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".