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TitleEarly Cretaceous palynology of the Scotian Margin (Atlantic Canada)
AuthorCorreia, VORCID logo; Fensome, R A; MacRae, R A; Williams, G L; Dafoe, LORCID logo
SourceAbstracts of the annual meeting of AASP - the Palynological Society; 2022 p. 107-108
Alt SeriesNatural Resources Canada, Contribution Series 20220085
PublisherThe Palynological Society
Meeting54th Annual Meeting of AASP; Manizales; CO; August 07-11, 2022
Mediapaper; digital; on-line
File formatpdf
ProvinceNova Scotia
AreaAtlantic Canada
Subjectsstratigraphy; Science and Technology; Nature and Environment; biostratigraphy; palynology; pollen; spores; Scotian Margin; Cretaceous; Mesozoic; Cenozoic
ProgramEnergy Geoscience Program Coordination
Released2022 08 07
AbstractBiostratigraphic 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.
Summary(Plain Language Summary, not published)
Age determinations for rocks of the Scotian Margin have largely been determined through analysis of microfossils, using events (mainly originations and extinctions of species). Palynomorphs (organic-walled microfossils), especially dinoflagellate cysts of marine origin and spores and pollen of terrestrial origin, are important tools in dating deposits, and are also indicators of past environments. This study involves palynologic, paleoenvironmental and sedimentary analysis of the Triassic to Lower Cretaceous cored sections of offshore wells on the Margin. Initial results from core samples from Panuke B-90 well indicate a transition from a fluvial-estuarine setting to a more marine setting, culminating in evidence from the middle part of the core of an open marine environment. The palynologic assemblages from the lower part of the core are characteristic of the Early Cretaceous, most likely of Barremian age (131 to 126 million years ago). Ongoing work on this Lower Cretaceous core and coeval wells will contribute to a comprehensive event-stratigraphic framework, critical for more applied studies, for example related to carbon capture.

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