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TitleAn integrated paleoenvironmental study of Lower Cretaceous to lower Cenozoic strata of the Labrador margin, offshore eastern Canada
AuthorDafoe, L TORCID logo; Williams, G L
SourceThe Atlantic Geoscience Society (AGS), 47th Colloquium and Annual Meeting, program with abstracts/La Société Géoscientifique de l'Atlantique, 47th Colloquium and Annual Meeting, program with abstracts; 2021 p. 17-18 Open Access logo Open Access
LinksOnline - En ligne (complete volume - volume complet, PDF, 1.12 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20200739
PublisherAtlantic Geoscience Society
MeetingThe Atlantic Geoscience Society-La Société Géoscientifique de l'Atlantique 47th Colloquium and Annual Meeting; February 5-6, 2021
Mediaon-line; digital
File formatpdf
ProvinceNewfoundland and Labrador; Eastern offshore region
AreaLabrador; Labrador Sea
Subjectstectonics; sedimentology; paleontology; Nature and Environment; Science and Technology; Paleogene; Paleocene; Eocene; Lower Cretaceous; continental margins; paleoenvironment; sedimentary basins; tectonic history; rifting; core samples; fossils; trace fossils; ichnology; ichnofacies; macrofossils; palynology; palynomorphs; miospores; microfossils; fossil assemblages; sedimentary structures; depositional environment; salinity; Labrador Margin; North American Plate; Greenland Plate; Hopedale Basin; Saglek Basin; Bisaccates; Dinoflagellates; Acritarchs; Cruziana; Methodology; Phanerozoic; Cenozoic; Tertiary; Mesozoic; Cretaceous
ProgramGEM2: Geo-mapping for Energy and Minerals Baffin Region
Released2021 02 01
AbstractRifting and opening of the Labrador Sea began in the Early Cretaceous and ceased in the latest Eocene as the Greenland plate separated from the paleo-North American plate. A record of this tectonism is preserved in the stratigraphic successions of the Hopedale and Saglek basins, respectively to the south and north along the Labrador margin. Previous paleoenvironmental studies of these strata have primarily focused on a single methodology using cuttings samples, typically microfossils or sedimentological observations, to define paleoenvironments. In this study, we use conventional core intervals to combine macroscopic observations of the sedimentology and ichnology with quantitative microscopic palynological analyses of bisaccates, other miospores, dinoflagellate cysts (dinocysts), acritarchs, and other palynomorphs to provide robust paleoenvironmental interpretations. The results are reported for 23 core intervals from 14 wells representing key intervals from the Early Cretaceous to basal Ypresian, with palynological counts from a total of 64 samples. The sedimentological and ichnological observations generally provide well defined interpretations of the paleoenvironment, while the palynomorph ratios indicate an approximate distance from the shoreline. Lower Cretaceous mudstones are typically devoid of dinocysts and acritarchs but contain bisaccates and other miospores: the palynological assemblages combined with low diversity and low abundance trace fossil suites indicate a restricted (brackish) marine embayment. Upper Cretaceous mudstones deposited in slope-equivalent and shelfal-equivalent water depths show high proportions of dinocysts and acritarchs relative to miospores, as expected. The slope strata are devoid of trace fossil suggesting reduced oxygenation, but fully marine Cruziana Ichnofacies characterize bioturbated shelfal strata. The Upper Cretaceous, and Selandian-basal Ypresian deposits are mostly deltaic, reflecting various depositional conditions. Storm- or wave-influenced deposits are characterized by low dinocyst and acritarch abundances and weakly stressed expressions of the Cruziana Ichnofacies. River-influenced deltaic strata mostly contain limited dinocyst and acritarch abundances with sedimentary structures prevalent and highly stressed expressions of the Cruziana Ichnofacies are present. River-dominated and tide-dominated (channel) strata lack marine palynomorph indicators, with sedimentary structures predominating. Dinocyst and acritarch results tend to parallel trace fossil diversity and abundance, but can be misleading in highly brackish settings where these marine indicators may not be present. Palynomorph counts can, however, help to refine paleoenvironments from strata that contain non-ubiquitous sedimentary features and can provide evidence of mixing of shallow and deeper water settings, such as progradation of a delta into deeper water. Overall, integration of the two methodologies, operating at very different scales, provides more robust paleoenvironmental interpretations.
Summary(Plain Language Summary, not published)
The record of geologic events relating to the formation of the Labrador Sea is recorded in stratigraphic layers found in the sedimentary basins along the Labrador margin. Core materials from the basins are assessed for paleoenvironments by combining different methodologies for a more robust interpretation.

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