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TitleBeaufort Formation chronostratigraphy and Pliocene landscape evolution - new insights into the formation of the Northwest Passages, Canada
AuthorStashin, S A; Gosse, J C; Smith, I R; Csank, A Z
SourceAtlantic Geoscience Society Abstracts: 44th Annual Colloquium & General Meeting 2018; Atlantic Geology vol. 54, 2018 p. 121, (Open Access)
Alt SeriesNatural Resources Canada, Contribution Series 20170338
PublisherAtlantic Geoscience Society
MeetingAtlantic Geoscience Society: 44th Colloquium and Annual General Meeting; Truro, NS; CA; February 2-4, 2018
Mediapaper; on-line; digital
File formatpdf
ProvinceNunavut; Northwest Territories
NTS69B; 69C; 69F; 69G; 77F; 77H; 78; 79; 87G; 87H; 88; 89; 97G; 97H; 98; 99
AreaCanadian Arctic Archipelago
Lat/Long WENS-128.0000 -103.0000 80.0000 71.0000
Subjectsstratigraphy; paleontology; geophysics; structural geology; geochronology; Pliocene; chronostratigraphy; depositional environment; depositional history; provenance; paleoenvironment; channels; fossils; fossil plants; vertebrates; paleoclimatology; seismic interpretations; structural analyses; source areas; erosion rates; Beaufort Formation; Beaufort Shelf; coastal plains; cosmogenic nuclides; Phanerozoic; Cenozoic; Tertiary
ProgramWestern Arctic Sverdrup Basin, GEM2: Geo-mapping for Energy and Minerals
Released2018 02 01
AbstractThe Pliocene Beaufort Formation in the western Canadian Arctic Archipelago is dominated by stream sediments forming a coastal plain and accretionary wedge that thickens westward into the Canada Basin. The Beaufort Formation contains extremely well-preserved peat, wood, and vertebrate fossils (e.g., beaver and camel), supporting paleoenvironmental records indicating a high Arctic boreal forest ecosystem was present during the Pliocene. However, records from various islands indicate environmental and climate variability among the sites; it is unclear if this is simply because the records are varying in age, or if there were actual climate differences between time-equivalent locations owing to, for example, contrasts in continentality.
Currently, the Beaufort Formation deposits are present on islands divided by inter-island channels. However, paleoflow and lithological provenance evidence collected on Prince Patrick Island in 2017 and reported previously by others suggest that the Beaufort Formation once formed a contiguous 1200 km-long coastal plain. Consequently, incision must have occurred in the waning stages or following Beaufort Formation deposition. Determining a depositional history of the Beaufort Formation would further inform the channel incision history. Additionally, the post-Pliocene mechanism of incision has yet to be properly resolved. Are the inter-island channels tectonic grabens that have been active since prior to the Pliocene, or were they opened after the Pliocene by incision by water and glaciers? Assessments of seismic data bounding M'Clure Strait do not reveal any normal faults that align with the strait's walls. The presence or absence of inter-island channels is important as their development may have affected onshore and offshore temperatures throughout the Archipelago, perhaps a factor influencing the observed climate variability between paleoenvironmental records.
New and revised ages have been determined for the depositional age of the Beaufort Formation on western Canadian Arctic Archipelago islands, within cuttings from petroleum well cores, and on chronostratigraphically similar fluvial deposits elsewhere in the Canadian Arctic. The geochronology will improve our ability to correlate the isolated paleoclimate records on different islands and test hypotheses regarding the paleoenvironmental changes and linking them to global and regional paleoclimate and paleoceanographic changes. Additionally, the cosmogenic nuclide concentrations provide paleo-erosion rates in the source areas to the Beaufort Shelf at particular times. Future work includes further refining the geochronology of the Beaufort Formation as well as using newly acquired seismic data to resolve the presence of faulting within the interisland channels and to locate the paleo shoreline.
Summary(Plain Language Summary, not published)
This conference presentation discusses new dating control on the age of the fluvial Beaufort Formation across the western Arctic Archipelago. Ages were determined by cosmogenic dating of quartz samples from well cores and collections from sections on Prince Patrick Island. Understanding differences in ages of this geological unit allows us to identify the timing with which the former continuous landmass became dissected by rivers and glaciers, forming inter-island marine channels. This geomorphic alteration of the landscape is then correlated with changes in the paleoenvironmental records preserved within the Beaufort Formation, and its transition from high Arctic Boreal, to a tundra bioclimatic zonation.