Facies heterogeneity of ‘Black Shales’—implications for depositional processes of organic-carbon-rich sediments in the Turonian Second White Specks Formation, Alberta, Canada
Bibliographic record
Abstract
ABSTRACT Historically, geologists have interpreted organic-carbon-rich deposits associated with Ocean Anoxia Events (OAEs) as low-energy, suspension-settling deposits. Recent research, on the controls on organiccarbon enrichment in epicontinental-basinal settings more broadly indicates that many factors including elevated organic carbon production, limited clastic dilution, and episodic burial must be optimized for such sediment attributes to develop. Importantly, such conditions are commonly found in association with transgressions. With these observations in mind, we tested the sedimentological controls on organic-carbon enrichment in early Turonian OAE2 associated sediments preserved in the Second White Specks Formation in southern Alberta. This succession is an ideal natural laboratory for such an investigation as rock samples are available from both exposures and core over a wide area at different maturities. To meet these aims well-preserved core, thin sections, and wireline log data were evaluated to determine grain size attributes, compositions, depositional textures, and distinguish grain origins of the sampled strata. These analyses were specifically designed to constrain the depositional and diagenetic controls responsible for organic-carbon enrichment in this unit and how these varied stratigraphically. The organic-rich interval overlies a significant transgressive surface, represented by a facies change from wave-rippled quartz sandstones to organic-rich mudstone. Significantly, in the organic rich mudstones of the Second White Specks Formation, the primary organic matter is contained in nannoplankton-rich pellets, and sand-sized mud aggregates organized into ripples. These rippled beds are sharp based, sometimes bioturbated, and sharply overlain by thin beds of fine-grained clay-mineral-rich mudstones rich in recycled organic-matter. This indicates that organic-carbon enrichment was a function of high biological productivity, with at least some transport of organic-rich pellets and aggregates, and rapid burial of the sediment rather than being controlled by pervasive bottom-water anoxia. High relative sea level trapped clastic sediments in near-shore areas reducing organic-matter dilution but periodic burial by thin (~1 mm) storm event deposits allowed for preservation.
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 | 0.000 | 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 | 0.000 | 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) | 0.000 | 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".