Mesoproterozoic seafloor authigenic glauconite-berthierine: Indicator of enhanced reverse weathering on early Earth
Notice bibliographique
Résumé
Abstract Sedimentary records suggest that the mid-Proterozoic (ca. 1.8–0.8 Ga) was persistently characterized by a greenhouse climate despite significantly lower solar luminosity compared to modern levels. To maintain greenhouse conditions, the partial pressure of carbon dioxide (pCO2) must have remained elevated, possibly indicative of key differences in the complexities of the carbon cycle compared to the modern. Modeling has suggested that high pCO2 was likely maintained by elevated rates of “reverse weathering:” marine authigenic clay formation, a process that consumes alkalinity and generates CO2. This process is kinetically slow in modern marine environments, yet is hypothesized to have been enhanced during the mid-Proterozoic due to the greater availability of important species for clay authigenesis such as silica and ferrous iron. This hypothesis is testable using the geological record, because enhanced reverse weathering would lead to the formation of abundant marine authigenic clays. However, the distribution of marine authigenic clays in the Proterozoic sedimentary record has not been paid sufficient attention. In this study, we report the presence of authigenic clays (glauconite and berthierine) from the Xiamaling Formation (ca. 1.4 Ga), North China. The glauconite-berthierine horizons occur as millimeter-to centimeter-thick laminae interbedded with muddy siltstone and feature detrital grains supported by the clay matrix. In places, these layers were partially reworked to form soft and cohesive intraclastic sands, suggesting a syndepositional origin. We hypothesize that marine iron cycling in the iron- and silica-rich mid-Proterozoic oceans may have facilitated the formation of authigenic iron-rich clay during the deposition of the Xiamaling Formation. The formation of iron-hydroxides on the seafloor—and the local increase in pH caused by subsequent dissimilatory iron reduction—could have resulted in the absorption of SiO2, Al(OH)3, and Fe(OH)2 to form soft, cohesive and noncrystalline Fe(OH)3-SiO2-Al(OH)3-Fe(OH)2 gels. These gels would have subsequently converted to glauconite/berthierine through aging. The transformation from glauconite-rich layers to berthierine-rich laminae was likely facilitated by a greater availability of Fe(II), and therefore higher Fe(II)/TFe and Fe/Si ratios. We suggest that the relatively rapid formation of syndepositional, seafloor berthierine and glauconite layers in the basal Xiamaling Formation is the result of enhanced reverse weathering during this time. This study provides an important geological support for carbon cycle models that invokes enhanced reverse weathering rates in the mid-Proterozoic ocean that may have helped to maintain a high-baseline pCO2 during this time.
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) | 0,001 | 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 ».