| Title | An integrated paleoenvironmental study of Lower Cretaceous to lower Cenozoic strata of the Labrador margin, offshore eastern Canada |
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| Author | Dafoe, L T ;
Williams, G L |
| Source | The 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 |
| Links | Online - En ligne (complete volume - volume complet, PDF, 1.12
MB)
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| Image |  |
| Year | 2021 |
| Alt Series | Natural Resources Canada, Contribution Series 20200739 |
| Publisher | Atlantic Geoscience Society |
| Meeting | The Atlantic Geoscience Society-La Société Géoscientifique de l'Atlantique 47th Colloquium and Annual Meeting; February 5-6, 2021 |
| Document | book |
| Lang. | English |
| Media | on-line; digital |
| File format | pdf |
| Province | Newfoundland and Labrador; Eastern offshore region |
| Area | Labrador; Labrador Sea |
| Subjects | tectonics; 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 |
| Program | GEM2: Geo-mapping for Energy and Minerals Baffin Region |
| Released | 2021 02 01 |
| Abstract | Rifting 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. |
| GEOSCAN ID | 328087 |
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