Tectonostratigraphy and allochthonous salt tectonics of Axel Heiberg Island, central Sverdrup Basin, Arctic Canada
Notice bibliographique
Résumé
Axel Heiberg Island (northern Nunavut) contains the thickest Mesozoic section in Sverdrup Basin. The approximately 370 km long island is second only to Iran in its concentration of exposed diapirs. Forty-six diapirs of Carboniferous evaporites and associated minibasins are impressively exposed on the island. Regional anticlines, which formed during the Paleogene Eurekan Orogeny, trend roughly north on a regular approximately 20 km wavelength and probably detach on the autochthonous Carboniferous Otto Fiord Formation evaporites. These evaporites comprise halite overlain by thick anhydrite containing thin limestone beds. Unlike the rest of the island, a 60 km wide area, known as the wall-and-basin region, has bimodal fold trends and irregular (<10 km) fold wavelengths. Here, crooked, narrow walls of superficially gypsified anhydrite crop out in tight anticline cores, which are separated by wider synclinal minibasins. We interpret the wall-andbasin region to detach on a shallow, partly exposed canopy of coalesced allochthonous evaporite sheets. This inference is based on four lines of evidence: 1) a halving of fold wavelength relative to folds outside the wall-and-basin region, 2) the exposure of anomalously young strata of Paleogene and Late Cretaceous age, 3) the occurrence of clustered equant minibasins having similarities to those in the northern Gulf of Mexico, and 4) a strikingly uniform level of piercement pointing to a stratiform allochthonous source layer. A canopy would require an evaporite depocentre, which may have ponded in a sinistral pull-apart basin of Carboniferous age. Strata record a salt-tectonic history spanning the Late Triassic (Norian) epoch to the Paleogene period. Stratigraphic thinning against diapirs and angular unconformities up to 90° indicate mild regional shortening in which diapiric roof strata were bulged up and flanking strata steepened. This bulging culminated during Hauterivian times, when diapiric evaporites broke out and coalesced at the surface to form a canopy. As the canopy was buried, it yielded second-generation diapirs, which rose between minibasins subsiding into the canopy. A consistent high emplacement level indicates that all exposed diapirs inside the wall-and-basin region rose from the canopy. In contrast, diapirs along the wall-and-basin margins were sourced in autochthonous salt as first-generation diapirs. Apart from the large diapir-centred unconformities, Jurassic-Cretaceous depositional evidence of salt tectonics also includes submarine debris flows and boulder conglomerates shed from at least three emergent diapirs. The report area's geological history includes six main tectonostratigraphic phases in the wider Arctic area, beginning with Carboniferous rifting and ending with the Paleogene Eurekan Orogeny. Extreme local relief, tectonic slide blocks, steep talus fans, and subaerial debris flows suggest that many wall-and-basin diapirs continue to rise today. Freeboard calculations suggest that the rise of diapirs having surface relief of even 400 m could be driven purely by gravitational loading, but additional mild tectonic shortening cannot be ruled out. The Axel Heiberg canopy is one of only three known exposed evaporite canopies, each revealed at a different structural level: above the canopy (Axel Heiberg), through the canopy (Great Kavir, Iran), and possibly beneath a canopy (Sivas Basin, Turkey).
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».