Grenville Foreland basin sedimentation in Scotland: structure, stratigraphy and sedimentology of the early Neoproterozoic Torridon and Morar group sequences
Bibliographic record
Abstract
The Grenville Orogen was pivotal in the amalgamation of the Rodinia Supercontinent and resulted from the \ncontinent-continent collision between Baltica-Laurentia and Amazonia. Detrital zircon geochronology has shown \na number of earliest Neoproterozoic (c. 1000 – 960 Ma) successions in Arctic Canada, East Greenland, Svalbard \nand Norway to be sourced from the Grenville Orogen. One of the most complete and most proximal of those \noccurs in Scotland, represented by the Torridon and (metamorphosed) Morar groups. Structural restoration of later Caledonian and Knoydartian deformation shows that the preserved part of this foreland basin measured at least \n250 x 250 km with a minimal stratigraphic thickness of 6-9 km. Following several years of structural, stratigraphic \nand sedimentological research, the following depositional evolution can now be reconstructed: \n \n1) an initial progradational episode marked by coarse, fluvial braidplain mollasse-type sediments deposited \ndirectly on basement and orogen-parallel (eastward) palaeocurrents (Applecross Fm of the Torridon Gp; Lower \nAltnaharra Fm of the Morar Gp); \n \n2) a switch to orogen-normal palaoecurrents (northward) concomitant with a transgression from fluvial (Aultbea \nFm of the Torridon Gp; Upper Altnaharra Fm of the Morar Gp) to tidally influenced distal fluvial and shallowmarine \nsand deposits (lower and upper Glascarnoch Fm, resp., of the Morar Gp) and then to finer-grained, \ndeeper-marine sediments (Vaich Pelite Fm of the Morar Gp); and \n \n3) a brief return to fluvial-deltaic deposition before resuming the shallow-marine transgressive trend (contained in the Crom Fm of the Morar Gp) into very fine-grained deep-marine deposits (Dibiedale Fm of the Morar Gp). \nGiven the tectonic stability of the underlying Archaean cratonic basement and the absence of evidence for rifting, \nwe interpret this depositional pattern to be primarily caused by fluctuations in sediment flux due to changes \nin the uplift rate within the Grenville Orogen. Both Scottish and Canadian Grenvillean eclogites underwent \nretrogression and exhumation shortly after 1000 Ma; in the fringing foreland basin this is coincident with the \ninitial progradational phase. Reduction in uplift rate (exhumation) associated with decreasing erosion resulted in \noverall lowering (albeit fluctuating) of sediment flux and onset of the transgressive phase. \n \nThe marine part of the basin may represent an inland branch of the newly proposed Asgard Sea between Laurentia \nand Baltica. We speculate that detritus of the Krummedal and Krossfjord sequences in East Greenland and \nSvalbard travelled via this branch from the Scottish part of the basin. The Torridon-Morar sequence thus represents \na transition between a Grenville foreland basin sensu-stricto and an associated marine basin, stretching away from \nthe orogen.
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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 | 0.005 | 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 | 0.000 | 0.003 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.003 |
| Research integrity | 0.000 | 0.002 |
| Insufficient payload (model declined to judge) | 0.034 | 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".