Sedimentary controls on Ediacaran macrofossil distributions
Bibliographic record
Abstract
Late Ediacaran sedimentary successions (c. 579–539 Ma) record a wide diversity of complex macrofossils in exclusively marine environments. These macrofossils document diverse multicellular eukaryotes, including the first recognisable animals. Global compilations of species occurrence reveal trends that have been interpreted as a deep marine (slope and basinal) origination for animals, and potentially Earth’s first mass extinction event. Despite the remarkable preservation of these fossils in multiple global localities, shallow marine Ediacaran deposits in Newfoundland (Canada) and Shropshire (U.K.), coeval with the earliest fossiliferous deep-water Avalonian deposits, have so far yielded no macrofossils. Such deposits have been overlooked from a palaeontological and sedimentological perspective. Without detailed characterisation of these depositional environments, alternative preservational, ecological, geochemical, or environmental explanations for late Ediacaran trends in biodiversity, for example variation in the likelihood of preserving substrates amenable to fossil preservation, remain possible, and their bearing on interpretations of global ecological trends is not yet understood. In this thesis, I address this problem by assessing local, regional and global sedimentary factors that control the suitability of an environment for both the colonisation and preservation of Ediacaran macrobiota. In Chapters 2 and 3, I assess the facies-level depositional environments of both the base-of-slope to shoreface stratigraphy of eastern Newfoundland, and the basin floor to shoreface stratigraphy of the Long Mynd, Shropshire. The distribution of substrates amenable to the preservation of Ediacaran macrofossils is found to exert a control on their apparent distribution. The depositional settings of the Long Mynd are revised, and formation mechanisms of several abundant surface textures within this succession, previously attributed to biological activity, are reinterpreted as abiotic. Comparing specific palaeoenvironments from these regions to those of other contemporaneous fossil-bearing successions through a global palaeoenvironmental study in Chapter 4, I then resolve palaeoenvironmental controls on global patterns of fossil distribution and palaeocommunity composition. This work refines understanding of the depositional environments of understudied late Ediacaran successions; identifies the palaeoenvironments that favoured the habitation, evolutionary development, and preservation of the first known animals; and establishes the sedimentary framework for interpreting global fossil distribution patterns.
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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) | 0.000 | 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".