Polygenetic (Polyphase) Karsted Hardground Omission Surfaces In Lower Silurian Neritic Limestones: Anticosti Island, Eastern Canada
Bibliographic record
Abstract
Abstract: Exquisitely preserved and well-exposed rocky paleoshoreline omission surfaces in Lower Silurian Chicotte Formation limestones on Anticosti Island, Québec, are interpreted to be the product of combined marine and meteoric diagenesis. The different omission features include: 1) planar erosional bedding tops, 2) scalloped erosional surfaces, 3) knobs, ridges, and swales at bedding contacts, and 4) paleoscarps. An interpretation is proposed that relates specific styles of omission surface to different diagenetic–depositional processes that acted in separate terrestrial–peritidal–shallow neritic zones. Such processes were linked to fluctuations in relative sea level with specific zones of diagenesis such as: 1) karst corrosion, 2) peritidal–shallow subtidal erosion, 3) subtidal seawater flushing and cementation, and 4) shallow subtidal deposition. Most surfaces are interpreted to have been the result of initial extensive shallow–water synsedimentary lithification forming hardgrounds that were, as sea level fell, planed by inner-neritic abrasion, successively altered by exposure and subaerial corrosion, only to be buried by sediments as sea level rose again. This succession was repeated several times, resulting in a suite of recurring polyphase omission surfaces through many meters of stratigraphic section. Synsedimentary cloudy marine cements are well preserved and are thus interpreted to have been calcitic originally. Aragonite components are rare and thought to have been dissolved just below the Silurian seafloor. Large mollusks that survived such seafloor removal were nonetheless leached and the resultant megamolds were filled with synsedimentary calcite cement. These Silurian inner-neritic–strandline omission surfaces are temporally unique. They are part of a suite of marine omission surfaces that are mostly found in early to middle Paleozoic neritic carbonate sedimentary rocks. These karsted hardgrounds formed during a calcite-sea time of elevated marine carbonate saturation and extensive precipitation of marine cement. The contemporaneous greenhouse atmosphere was supercharged with CO2, leading to profound surface karst under strongly acid rain. Younger peritidal omission surfaces, although potentially formed during aragonite-sea or calcite-sea times, would have been subject to very different terrestrial diagenetic process with lower atmospheric pCO2 values but increasingly complex biogenic soils producing dissimilar alteration features.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".