High-energy seafloor processes and biological reworking as first-order controls on mudstone composition and geochemistry
Bibliographic record
Abstract
This PhD research project aims to develop a better understanding of how physical \nseafloor reworking and macrofaunal bioturbation control the lithofacies variability of \nmudstones deposited under high-energy seafloor conditions. To address this aim, \nbioturbated and unbioturbated mudstones from two natural laboratories in Newfoundland, \nCanada and Baja California, Mexico were investigated. Sections of interest were logged \nat a cm-scale and organic and inorganic geochemical measurements were performed on \nbioturbated and unbioturbated mudstones within both successions. To improve the \nfidelity of paleoenvironmental reconstructions these geochemical measurements were \ncombined with high-quality sedimentological and ichnological datasets at a range of \nlength scales. Unbioturbated mudstones in the Early Ordovician Bell Island Group, \nNewfoundland, previously reported to have been deposited under anoxic conditions, \ninstead, most likely originated as hyperpycnal flows and wave-enhanced sediment gravity \nflows. The proximity to a fluvial source and residence time of rock components in the \nnear-surface zone are interpreted to be the primary control on the compositional \nheterogeneity of mudstones within this Ordovician mud-dominated shoreface \npaleoenvironment. Following this, high-energy seafloor conditions are a more realistic \nexplanation for the high presence of unbioturbated mudstones in the heterolithic Bell \nIsland Group. Additionally, the formation mechanism of shrinkage (‘synaeresis’) cracks, \nwhich are sedimentological prime indicators for salinity fluctuations in marginal-marine \nenvironments, has been re-evaluated. Sediment cracking is proposed to form as an \nexclusively intrastratal process, independent of fluctuations of pore water salinity. Spatial \nrheological inhomogeneities associated with microbial mat decay shortly after burial are proposed to produce intrastratal shrinkage cracks. The effect of bioturbation on the \ngeochemical variability of mudstones has been investigated within mudstones and finegrained \nsandstones of the Rosario Formation, Mexico. The spatial distribution of organic \ncarbon and redox-sensitive trace elements is controlled by the feeding activity of grainsize \nselective vermiform animals and associated in-vivo alteration of weatheringsusceptible \nminerals. The reactivity of organic carbon is proposed to be a critical variable \ncontrolling pathways of diagenesis in bioturbated mudstones. It is imperative that \npaleoenvironmental analyses consider the long-term effects of bioturbation and highenergy \nseafloor processes to fully understand the compositional variability of mudstones \nwithin a basin-wide context.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".