Comparative Stratigraphic and Geochronological Evolution of the Northern Damara Supergroup in Namibia and the Katanga Supergroup in the Lufilian Arc of Central Africa
Bibliographic record
Abstract
The Damara Supergroup in Namibia and the Katanga Supergroup in the Central African Copperbelt (some 1000 km apart) are characterized by rock successions indicative of almost coeval orogenic evolution through phases of intracontinental rifting, spreading, continental rupture, subduction, ocean closure and continental collision in what appears to have been a single, elongate orogenic belt. Rifting began at about 880 Ma and lasted until about 800 or 756 Ma. Post-rift thermal sag and marine transgression produced the first correlatable stratigraphic units, the argillaceous Beesvlakte and Ore Shale Formations, in northern, carbonate-dominated platformal successions on the Damaran Northern Platform and the Katangan Lufilian Arc or Fold Belt, respectively. Sturtian (~735 Ma) and Marinoan (635 Ma) glacial units are common to both successions as well as syntectonic molasse sequences (~595–550 Ma). Continental collision occurred at about 542 Ma and the post-tectonic peak of regional metamorphism was at about 535–530 Ma. Mineral ages record cooling to about 460 Ma. The extensive occurrence of stratabound, but not stratiform, copper mineralization, evaporitic minerals, salt and thrust tectonics, syntectonic breccias, and intense alteration in the Lufilian Arc have no significant equivalents in the Northern Platform. However, the Beesvlakte Formation has both concordant and strongly discordant styles of copper mineralization and the mode of occurrence of mineralization in the Copperbelt can be a guide to exploration in Namibia.SOMMAIRELe Supergroupe de Damara en Namibie et le Supergroupe de Katanga de la bande cuprifère d’Afrique centrale (distant de 1 000 km) sont caractérisés par des successions de roches montrant une évolution orogénique presque contemporaines dans leurs phases de distension intracontinentale, d’expansion, de rupture continentale, de subduction, de fermeture océanique et de collision continentale, dans ce qui semble avoir été une seule et même bande orogénique étroite. La distension a débutée il y a environ 880 Ma et s’est prolongé jusqu’à 800 Ma ou 756 Ma. Le fléchissement thermique post-distension et la transgression marine ont donné les premières unités stratigraphiques corrélables, soit la Formation argileuse de Beesvlakte et la Formation de Ore Shale, de la portion nord des successions de plateforme principalement carbonatées sur la Plateforme nord de Damaran et de l’Arc ou de la bande plissée de Katangan Lufilian respectivement. Les unités glaciaires de Sturtian (~735 Ma) et de Marinoan (635 Ma) sont communes aux deux successions, tout comme les séquences de molasses syntectoniques (~595–550 Ma). La collision continentale s’est produite il y a environ 542 Ma et le pic post-tectonique de métamorphisme régional a eu lieu il y a environ 535 à 530 Ma. Selon les datations minérales, le refroidissement s’est produit il y a environ 460 Ma. La prépondérance du contexte stratoïde plutôt que stratiforme des minéralisations de cuivre, des minéraux d’évaporites, de sel et de tectonique de compression, de brèches syntectoniques, et d’altération intense dans l’Arc de Lufilian, n’a pas d’équivalent dans la plateforme du nord. Cependant, la Formation de Beesvlakte présente des minéralisations de cuivre qui sont ou concordantes, ou fortement discordantes, et le mode d’occurrence de la minéralisation dans le bande cuprifère peut servir de guide à l’exploration en Namibie.
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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 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".