Neoproterozoic Extension on the Scottish Promontory of Laurentia: Paleogeographic and Tectonic Implications
Bibliographic record
Abstract
The Hebridean shield, the northwest foreland of the Caledonian Orogen of Scotland, is a small fragment of Laurentia detached during the Cenozoic opening of the North Atlantic Ocean and is now part of Europe. The shield was at the tip of a major promontory of the ancestral core of North America, between the Newfoundland (Appalachian) and Greenland (Caledonian) margins. Its history is important to understanding late Precambrian and early Paleozoic global paleogeography and tectonics. Isotopic ages and structural complexities in the Moine and Dalradian Supergroups of the Caledonian Orogen have been interpreted as reflecting Neoproterozoic orogenic episodes overprinted by early Paleozoic deformation and metamorphism. A critical body of rock in the Scottish Highlands, the West Highland Granite Gneiss, has been viewed as a synorogenic intrusion into Moine metasedimentary rocks, and its ∼870‐Ma U‐Pb zircon age as dating a Riphean “Knoydartian” orogeny. However, field evidence shows that the granitic protolith of the gneiss was emplaced before a regional suite of tholeiitic dikes was intruded into brittle fractures. The dikes carry all the ductile regional deformation. The zircon age thus reflects the crystallization of an anatectic melt, not its subsequent gneissification. Melting is thought to have resulted from advection of heat by emplacement of basaltic magma deep within the Moine sedimentary pile. In this new scenario, deformation and gneissification took place during the early (Grampian/Taconic) phase of the Caledonian Orogeny, not during the Neoproterozoic. Our interpretation is that all the Knoydartian events were extensional. This leads to a substantial simplification of the pre‐Caledonian history of the Scottish Promontory of Laurentia. Protracted rifting in the Neoproterozoic was concentrated in two phases, with episodes of major extension and bimodal magmatism in the Riphean (∼900–750 Ma) and Vendian (∼600 Ma). These episodes coincide with the two‐stage breakout of Laurentia as a discrete continent during the Neoproterozoic, hypothetically from the Rodinian and Pannotian supercontinents, respectively.
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 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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".