Geochemistry of C, O, and Sr isotopes in the Neoproterozoic carbonates from the southwestern Patom paleobasin, southern Middle Siberia
Notice bibliographique
Résumé
Scatter of δ13C (from −11.6 to 8.4‰) and sequence of carbon isotope events in the Vendian carbonates from the southwestern Patom paleobasin (Vitim, Bol’shaya Chuya, and Chaya rivers) are similar to those previously established in the reference northeastern sections. It was found that cap dolomites crowning the glaciogenic diamictites of the Dzhemkukan Formation are characterized by moderately low δ13C (from −7.4 to −5.1‰), while the limestones, marls, and calcareous aleurolites of the Zhuya Group (Nikol’skoe and Chencha formations) correlable with the Shuram-Wonoka event (580–650 Ma) have extremely low δ13C values (up to −11.9‰). Intervals with negative δ13C are separated by positive excursion of δ13C (most part of the Barakun, Valyukhta, and Uluntui formations) with extreme up to 8.4‰. One more positive excursion (δ13C up to 6.1‰) was identified in the dolomitic unit sandwiched between the limestones of the Chencha Formation and the sandstones of the Zherba Formation on the Vitim and Bol’shaya Chuya rivers; in the northeastern sections of the Patom Complex, the positive excursion corresponds to the hiatus, but occurs at similar level (∼550 Ma) in many sections of Oman, China, Namibia, Australia, and other regions. Ultrahigh δ13C (from 11.7 to 15.2‰) values were found in ∼150-m-thick succession of “coaly” carbonates in the Lokatyk Block (Bol’shaya Chuya River), which were presumably erroneously ascribed to the Barakun Formation. These carbonates likely marking the Neoproterozoic anoxic peak are not known among the Vendian (Ediakaran) successions, but have previously been described in the sediments with an inferred age of 720–650 Ma in the Bambui Group (eastern Brazil) and Keele Formation of the Neoproterozoic Windermere Group (northwestern Canada). Scatter of δ18O in the studied carbonates (from 6.3 to 28.5‰) was mainly caused by postsedimentary transformations. General correlation between δ18O and δ13C is absent. Both positive and negative correlations can be observed within limited intervals, indicating that the behavior of O and C isotope systems was not controlled by a common mechanism. The lowest 87Sr/86Sr = 0.7084 in the main chemostratigraphic marker (Chencha Formation) in the extreme west (Chaya River) does not differ much from the 87Sr/86Sr value in the Chencha Formation in the northeastern sections, which confirms the hydrological homogeneity of the Patom paleobasin. The lowest 87Sr/86Sr (0.70815) in the carbonates of the Uluntui Formation of the Chaya section, however, is much lower than in the carbonates from the stratotype area (0.70842) of the Uluntui Formation (Kuznetsov et al., 2013). This casts some doubts on the correlation of these stratigraphic units.
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 | 0,000 | 0,001 |
| 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) | 0,000 | 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 ».