| Titre | Early Cretaceous palynology of the Scotian Margin (Atlantic Canada) |
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| Auteur | Correia, V ;
Fensome, R A; MacRae, R A; Williams, G L; Dafoe, L |
| Source | Abstracts of the annual meeting of AASP - the Palynological Society; 2022 p. 107-108 |
| Image |  |
| Année | 2022 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20220085 |
| Éditeur | The Palynological Society |
| Réunion | 54th Annual Meeting of AASP; Manizales; CO; août 07-11, 2022 |
| Document | livre |
| Lang. | anglais |
| Media | papier; numérique; en ligne |
| Formats | pdf |
| Province | Nouvelle-Écosse |
| Région | Le Canada atlantique |
| Sujets | biostratigraphie; palynologie; pollen; spores; stratigraphie; Sciences et technologie; Nature et environnement; Crétacé; Mésozoïque; Cénozoïque |
| Illustrations | photographies |
| Programme | Géosciences de l'énergie La coordination du programme |
| Diffusé | 2022 08 07 |
| Résumé | (disponible en anglais seulement)
Biostratigraphic studies of Mesozoic-Cenozoic strata along the Scotian Margin began in the early 1970s, with the works focussing on zonation schemes for
separate disciplines. Subsequent studies over the past 25 years, however, have evolved into an event stratigraphic approach, with the publication of significant multidisciplinary event-stratigraphic frameworks that combined palynologic with
micropaleontologic and nannofossil events, as well as seismic horizons. Extensive taxonomic treatments of Late Cretaceous and Cenozoic palynomorphs from the Scotian Margin were also undertaken, but did not encompass the Triassic to Lower Cretaceous
interval. We are thus developing a comprehensive event-stratigraphic scheme for this earlier interval on the Scotian Margin based on palynology, integrated with paleoenvironmental changes and sequence stratigraphy. In addition to detailed taxonomic
and event stratigraphic studies, we also aim to investigate the impact of varying paleoenvironmental conditions, including brackish environments and global stress events (e.g. Oceanic Anoxic Event 1a). Our main focus is on conventional cores (e.g.
Panuke B-90, Cohasset A-52 and Alma K-85), aiming to develop a composite Lower Cretaceous section to avoid problems with down-hole sample contamination (caving). Nevertheless, we are also using cuttings from deeper wells that penetrate pre-Cretaceous
strata (e.g. Argo F-38, Bittern M-62, comprising a Triassic to Paleogene succession) to provide a broader context. The sedimentary facies and trace fossils at the base of the Panuke B-90 core indicate a transition from a shoaling marine to a mainly
fluvial-estuarine setting, followed by a transgressive cycle through the Upper Mississauga Formation that culminates in normal marine environments again near the base of the overlying Naskapi Member (Logan Canyon Formation). This trend is supported
by initial palynologic results from the base of the Upper Mississauga Formation that suggest a marginal marine depositional setting based on: abundant foraminiferal test linings and acritarchs, including Leiosphaeridia and Nummus; common records of
the prasinophyte Pterospermella; presence of the freshwater alga Schizosporis; and low species richness and abundance of dinoflagellate cysts, with common Subtilisphaera spp. Furthermore, there is a general trend up section of increasing
dinoflagellate cyst richness and abundance, with frequent occurrences of the areoligeraceans Circulodinium distinctum and Tenua spp., the ceratiaceans Muderongia spp. and Pseudoceratium spp., Cribroperidinium spp., Druggidium rhabdoreticulatum,
Kiokansium spp., Kleithriasphaeridium spp. and Oligosphaeridium spp. (Plate I); the dinoflagellate cyst assemblage indicates a neritic depositional setting. Terrestrial palynomorphs, such as the pollen Araucariacites australis, Cerebropollenites
macroverrucosus, Clavatipollenites sp. and bisaccates, as well as the spores Cicatricosisporites spp., Concavissimisporites spp., Deltoidospora spp., Dictyophyllidites spp., Gleicheniidites senonicus and Ruffordiaspora spp. (Plate I), are also
abundant and support a relatively proximal position for this well during the middle Early Cretaceous. These assemblages from the lower part of the Panuke B-90 core (Upper Mississauga Formation) are typical of the Early Cretaceous, most probable
Barremian. An Aptian age is expected for the overlying Naskapi Member based on previous studies and the presence of age-diagnostic ammonites such as Deshayesites sp. Ongoing work on this Lower Cretaceous core and coeval successions will contribute to
a comprehensive event-stratigraphy framework for the Scotian Margin. |
| Sommaire | (Résumé en langage clair et simple, non publié)
La datation des roches de la marge néo-écossaise est en grande partie fondée sur des événements (principalement les origines et les extinctions
d'espèces) déterminés au moyen de l'analyse de microfossiles. Les palynomorphes (microfossiles à parois organiques), en particulier les kystes de dinoflagellés d'origine marine et les spores et pollens d'origine terrestre, sont des outils importants
pour la datation des dépôts et sont également des indicateurs des environnements passés. La présente étude comporte des analyses palynologique, paléoenvironnementale et sédimentaire des sections carottées des puits sous-marins de la marge allant du
Trias au Crétacé inférieur. Les premiers résultats des échantillons de carottes du puits Panuke B 90 indiquent une transition d'un milieu fluvio estuarien à un milieu plus marin. Les preuves à cet effet sont éloquentes dans la partie centrale des
carottes provenant d'un milieu marin à circulation libre. Les assemblages palynologiques de la partie inférieure des carottes sont caractéristiques du Crétacé inférieur et très probablement du Barrémien (il y a 131 à 126 millions d'années). Les
travaux en cours sur les carottes du Crétacé inférieur et les puits contemporains contribueront à l'élaboration d'un cadre stratigraphique exhaustif axé sur les événements. Un tel cadre s'avère essentiel pour mener des études appliquées, par exemple
des études liées au captage de carbone. |
| GEOSCAN ID | 330104 |
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