Pre-Neogene non-marine diatom biochronology with new data from the late Eocene Florissant Formation of Colorado, USA
Notice bibliographique
Résumé
Studies of the non-marine diatom assemblages from Eocene deposits in North America extend the fossil record of a number of extant freshwater diatom lineages. These and other accounts show that the earliest documented appearances of non-marine diatoms consisted of 7 genera from late Cretaceous deposits, followed by 36 more from the Eocene, and 4 additional genera from Oligocene to early Miocene localities. A total of 47 diatom genera, 45 of which are extant, therefore, are known from pre-Neogene (>23.8 Ma) non-marine deposits. The chronological extension of these first-occurrences of genera has implications for terrestrial diatom biostratigraphy, paleoclimate, and diatom phylogenetic studies. An overview of the pre-Neogene non-marine diatom biochronology from published records and original work provides the geologic and geographic context for the more current findings. Two geologic range charts synthesize the data from the pre-Neogene non-marine (fresh and brackish water) diatom floras from the 9 published localities, supplemented by additional findings from a recent floristics study of the Florissant site in Colorado. These charts allow easy comparison of the timing, floral composition, and taxon-richness at the genus level and higher for the 9 sites. Among the pre-Neogene sites discussed here are early and middle Eocene deposits in Canada and middle Eocene deposits in Idaho andWyoming that provide evidence of an early pulse in the post-Cretaceous radiation of freshwater diatoms. The survey of the fossil diatoms from lake sediments of the Florissant Formation in Colorado showed that this deposit contains the most diverse (genus-rich) early freshwater diatom flora on record. This late Eocene flora suggests a later pulse in freshwater diatom radiation during pre-Neogene time that contributed to the rich taxonomic diversity of today. The Florissant fossil diatom investigations yield a total of 33 freshwater diatom genera. This number exceeds by 20 genera any other single known non-marine diatom-bearing Eocene and older deposit. The Florissant diatom flora consists of taxa with decidedly modern affinities, has superior diversity (taxon-richness), and yields the first-reported occurrence in the geologic record of 14 freshwater genera. From the 9 featured pre-Neogene sites, genera of centric, araphid, biraphid, and monoraphid morphologic groups are represented. While the findings of these studies are not inconsistent with the previously predicted timing of the first appearance of the major morphological diatom groups, the actual known fossil record post-dates the presumed timing of such morphological differentiation. Although the first occurrences in these deposits must be treated as apparent first occurrences due to the innate incompleteness of the fossil record, such findings confirm that species of many of the modern non-marine diatom genera had evolved prior to the end of the Eocene. It is anticipated that this synthesis of the pre-Neogene non-marine diatom floras will provide necessary paleontological evidence for interpreting the true geologic ranges of several diatom lineages. This work could facilitate future application of diatoms in biostratigraphic studies of fossil lake beds in hydrologic and climate change studies and in hydrocarbon exploration. Perhaps such data will generate insights to diatom phylogenetics that may lead to a greater understanding of their evolutionary histories. Further research could potentially relate changes in diatom forms to global events that might include climate shifts.
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 | 0,000 |
| Communication savante | 0,000 | 0,001 |
| Science ouverte | 0,001 | 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 ».