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TitleLower Cretaceous cold snaps led to widespread glendonite occurrences in the Sverdrup Basin, Canadian High Arctic
AuthorGrasby, S E; McCune, G E; Beauchamp, B; Galloway, J M
SourceGeological Society of America Bulletin vol. 129, no. 7-8, 2017 p. 771-787,
Alt SeriesEarth Sciences Sector, Contribution Series 20160219
PublisherGeological Society of America
Mediapaper; on-line; digital
File formatpdf
NTS69C; 69D; 69E; 69F; 69G; 69H; 79E; 79H
AreaEllef Ringnes island
Lat/Long WENS-106.0000 -98.5000 79.5000 77.7500
Subjectsgeochemistry; Nature and Environment; climate effects; climate, arctic; cold regions research; host rocks; Valanginian; Aptian; carbon isotopes; organic carbon; deposition; Sverdrup Basin; glendonites; Cretaceous
Illustrationslocation maps; geological sketch maps; stratigraphic sections; tables; plots; photographs; photomicrographs; histograms
ProgramWestern Arctic Sverdrup Basin, GEM2: Geo-mapping for Energy and Minerals
Released2017 02 10
AbstractDramatic global climate change in the Early Cretaceous suggests that numerous boreal cool events perturbed otherwise warm conditions. Abundant glendonites in Valanginian and Aptian strata are thought to be key markers of cold conditions; however, their use as climate indicators has been questioned. Therefore, a detailed study of glendonites in the context of host-rock geochemistry was conducted on Cretaceous strata exposed on Ellef Ringnes Island, Sverdrup Basin, Canadian High Arctic, to elucidate paleoenvironment controls on periodic glendonite occurrence throughout the Early Cretaceous. Two prominent glendonite zones were identified in Valanginian and Aptian strata. Data for carbon stable isotopes show delta13Ccarb values of -29.5permil to -10.5permil, consistent
with a carbon source from organic matter within the surrounding shale. Trace metal data suggest deposition occurred under an overall
oxidizing water column in a setting with higher than average phosphorus and highly degraded organic matter. There is no variation in the geochemical parameters of the mudstones with or without glendonites. Glendonite-bearing zones are coincident, however, with regional evidence for brief periods of colder climate conditions within the otherwise warm Early Cretaceous. We conclude that while the overall conditions for glendonite formation were prevalent throughout the Cretaceous, it was the brief cold periods that provided the final range of
stability for their preservation in discrete zones of Valanginian and Aptian strata. These results support the model of an overall warm Early
Cretaceous climate being punctuate by several "cold snaps" of as-yet uncertain origin.
Summary(Plain Language Summary, not published)
An unusual crystal structure known as 'glendonite' is found commonly in shales of Cretaceous age across the high arctic. The origin of these features has been largely debated. GSC scientists conducted a detailed study of the geochemistry of the rocks that host glendonites and are able to show that they reflect short-term climate events, 'cold-snaps' that occurred in an otherwise overall warm period of earth history. What factors drove these cold snaps remains uncertain but the results show that rapid periods of climate instability occurred during the Cretaceous.