The Stratigraphy and Geochemistry of the Crescent Formation Basalts and the Bedrock Geology of Associated Igneous Rocks Near Bremerton, Washington
Notice bibliographique
Résumé
A stratigraphic section developed for the Bremerton rocks in the Kitsap Peninsula suggests formation by rifting in a marine environment. Basal gabbro, dated by 40Ar/39Ar at 49.8 Ma plus or minus 0.8 Ma, and associated mafic to felsic plutonics, appear to be the source of a mafic dike complex that composes 100% of the stratigraphic level above the plutonics. These dikes are the apparent feeders to overlying submarine and subaerial volcanics. The previously unrecognized submarine sequence consists of interbedded basaltic breccia, tuffs, basalt flows, and basaltic sandstone, siltstone, and conglomerate. Approximately 1 km of columnar basalt flows cap the sequence. Structures in the Bremerton rocks suggest that as many as four deformations may have affected these rocks. In the middle Eocene, extension to the north or northwest caused rifting and emplacement of the mafic dikes and lavas; several faults show that this extension was joined or followed by northeast-directed compression. Small faults and shears may have formed later by compression to the northwest. Reactivation of one of these faults and emplacement of northwest-striking Cascade arc(?) dikes suggest the latest deformation was extension to the northeast. The gabbro and basalts have chemistry transitional between N-type MORB and enriched ocean island basalt. Large-ion-lithophile to high-field-strength trace element ratios are similar to those of back-arc basin basalt. Felsic plutonics are enriched in elements (especially Zr) indicative of an arc influence. Several dikes intruding the gabbro are chemically indistinguishable from P-type (plume) ocean island basalt. Stratigraphic sections were developed in the basalts of the Crescent Formation and for basalts near Port Townsend in the Olympic Peninsula. Comparison to the subaerial basalts near Bremerton shows that the latter are quite similar to the upper subaerial Crescent Formation basalts and Port Townsend basalts. New chemical data for 16 flows of the Olympic Peninsula basalts are also similar to that of the Bremerton rocks. Stratigraphic and chemical similarities imply that rocks of all three areas are coeval. Deposition of the Crescent Formation basalts on a continentally-derived fan, stratigraphic and structural characteristics of the Bremerton rocks, and geochemical data on rocks of ail three areas suggest that these rocks formed by rifting of the western margin of the North America continent. Following rifting and basalt generation, the rocks may have moved north due to oblique convergence of the oceanic and continental plates, where they were thrust under Vancouver Island along the Leech River Fault. Thrusting moved outboard of the basalts and underlying fan; continued convergence thrust marine sediments that make up the Olympic core rocks beneath the basalts and underlying fan.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
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 | 0,001 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 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 ».