Late Cretaceous intra-arc transpression and thrusting in the Southern California batholith support moderate “Sierra–British Columbia” translation models
Notice bibliographique
Résumé
ABSTRACT The Late Cretaceous paleogeography of southern California potentially plays a central role in resolving conflicting models for postulated large-magnitude dextral translations along the western margin of North America (the Baja–British Columbia hypothesis) and the beginning of the Laramide orogeny. The Mount Pinos sector of the Southern California batholith (SCB) provides a unique window into this time because it preserves evidence for a kinematically partitioned fault system that includes a ductile shear zone (the Tumamait shear zone) and a ductile-to-brittle thrust fault (the Sawmill thrust). These two structures accommodated intra-arc strain during the Late Cretaceous to Paleocene during two phases of deformation (D3-D4) that are superimposed on older (D1 and D2) structures. D1 structures only occur in pre-Mesozoic rocks and provide a reference frame for understanding subsequent deformation phases. D2 structures form part of a previously unmapped dextral-normal shear zone that predates the Tumamait shear zone. The initiation of displacements within the Tumamait shear zone is recorded by the formation of D3 mylonites, which everywhere record reverse-sinistral movement. Petrochronology of syn-D3 titanites gives lower-intercept 206Pb/238U dates ranging from 77 to 74 Ma and upper-amphibolite-facies temperatures ranging from 699 °C to 718 °C. D3 fabrics also occur in peraluminous granites as young as 70 Ma, indicating that D3 deformation was synchronous with high-temperature intra-arc processes from 77 to 70 Ma. D4 fabrics involve folding of D3 mylonites and thrusting of upper-plate gneisses over the Pelona schist. Near the Sawmill thrust, the D4 event resulted in an S4 crenulation cleavage and asymmetric, overturned folds that record top-to-the-NE tectonic displacements. NE-directed thrusting along the Sawmill thrust occurred after 70 Ma and during the latest Cretaceous to early Paleocene based on 40Ar-39Ar cooling ages in the upper plate. We interpret deformational fabrics in the Mount Pinos area to record a transpressional system that involved sinistral-reverse shearing (D3) closely followed by folding and arc-directed thrusting (D4). We speculate that D3 structures developed in response to opening of the Kula-Farallon plate boundary, and we hypothesize that the Kula–Farallon–North American plate triple junction was located at the present-day location of the Garlock fault at ca. 85 Ma, thereby segmenting the California arc at this location. This geometry resulted in dextral shearing in the Sierra Nevada Batholith (and northward) and sinistral shearing in the SCB and Baja California. Continued subduction of the Farallon plate beneath the SCB led to a major arc flare-up event from 90 to 70 Ma, which was synchronous with D3 sinistral transpression. We interpret D4 structures to record oblique convergence and the underthrusting of the conjugate Hess oceanic plateau beneath the SCB after 70 Ma. Our model for the segmentation of the California arc is compatible with a moderate (1000–1600 km) “Sierra–British Columbia” translation model in which the Insular superterrane was located north of the SCB in the Late Cretaceous.
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) | 0,001 | 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 | 0,001 | 0,001 |
| 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 ».