Palynology and Stratigraphy of an Upper Cretaceous Sedimentary-Volcanic Sequence, Emma Fiord, Northwest Ellesmere Island, N.W.T, Canada.
MacRae, R. Andrew
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Terrestrial sedimentary units (lignite and siliclastics) are interbedded with bimodal volcanic units (alkali basalts, silicic volcanics and pyroclastics) on an unnamed peninsula between Audhild Bay and Emma Fiord (81o30'N, 90oW), northwest Ellesmere Island, Canadian Arctic Islands. The complete section is over 300 metres thick, and is complicated by interfingering of the volcanic and sedimentary units. The units were deposited within the Sverdrup Basin during the Late Cretaceous. They correlate lithologically with the lower part of the Eureka Sound Group, and are time- equivalent to the upper Kanguk Formation. Seven palynology samples display a rich palynomorph assemblage (over 30 species). Forms include the age-diagnostic pollen species Wodehouseia edmontonicola Wiggins, 1976 and Wodehouseia gracile (Samoilovitch, 1961). Comparing to the biostratigraphic framework of western North America, these indicate an early to middle Mastrichtian age for part of the sequence. Other forms present are Cranwellia, Erdtmanipollis, and several species of triprojectate (Aquilapollenites) pollen. The assemblage has affinities with the western North American and Siberian paleofloral provinces. Plant megafossils include Parataxodium, Ginkgo, and undetermined angiosperms. Whole-rock 40Ar/39Ar age dating of the bracketting volcanic units (G.K. Muecke and P. Reynolds, pers.comm.)has yielded dates of 80Ma ± 2Ma. This is mid-late Campanian according to the currently accepted time scales. There is a minimum discrepancy of several million years between the biostratigraphic and radiometric ages. A conservative estimate is a discrepancy of 5 million years. One explanation is that some of the pollen forms (i.e. Wodehouseia) were appearing earlier at high latitudes than at more southerly areas (western North America). Another explanation is an error in the currently accepted time scale, or the biostratigraphy in western North America. In light of work by other authors (Nichols and Sweet, in press) indication heterochronities in the appearance of Wodehouseia in western North America, a biotic heterochroneity seems most likely. Examination of other units in the Canadian Arctic Islands may be able to test this hypothesis. Keywords: Pages: 212 Supervisors: Gunter Muecke and Graham Williams