Basement palaeogeography of late Neoproterozoic Scotland: constraints from exotic clasts within the lower Dalradian Supergroup
Bibliographic record
Abstract
Synopsis U–Pb geochronology of exotic igneous cobbles, together with detrital zircons from a nearby sedimentary heavy mineral band from the Glenshirra Group (basal Dalradian Supergroup), provide information on the age and nature of the adjacent crystalline basement that supplied detritus to the Dalradian Basin in the late Neoproterozoic. The igneous cobbles were sampled from a metaconglomerate interpreted as debris-flow deposits from a local igneous basement hinterland. A granite cobble, and detrital zircons from a nearby psammite, gave c . 1800 Ma ages, indicating derivation from a presumed local Ketilidian–Makkovikian source akin to that exposed on Inishtrahull, Colonsay and the Rhinns of Islay. A syenite clast yielded crystallization ages of c . 1500 Ma (zircon cores), followed by a subsequent metamorphism at 1470 Ma (zircon rims). This corresponds to coeval Mesoproterozoic events that affected the Pinwarian terrane of SE Canada and Newfoundland. The Moine Supergroup and Glen Banchor Succession are unlikely sources of detritus for the Glenshirra Group, as palaeodrainage across the line of the future Great Glen Fault (in its pre-displacement disposition) would largely derive from local basement to the west of the Moine Supergroup. Whilst the existence of nearby Ketilidian–Makkovikian basement has been noted previously, this study provides evidence that Pinwarian basement also lay adjacent to Scotland during the deposition of the early Dalradian basin fills. These data should be incorporated into palaeogeographical reconstructions at the time of the break-up of the Rodinian supercontinent in the late Neoproterozoic. Supplementary material: Full U-Pb LA-MC-ICP-MS analytical results are provided at is http://www.geolsoc.org.uk/SUP18692 .
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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 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 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".