PALYNOLOGY OF THREE SECTIONS ACROSS THE UPPERMOST CRETACEOUS/PALEOCENE BOUNDARY IN THE YUKON TERRITORY AND DISTRICT OF MACKENZIE, CANADA
Wilson, Malcolm Alan
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The palynomorphs found in the three sections located in the lower Mackenzie River valley permit the establishment of zonal schemes with potential local value and suggest a position for the Cretaceous/Tertiary boundary. Two of these sections, Police Island in the Mackenzie River and the Big Fish River area adjacent to the Mackenzie Delta, are surface samples and the third, the I.O.E. Atkinson Well (from 1440- 3970 feet), is a subsurface section. From a total of 64 samples, four, all from the Big Fish River area, were barren; the rest yielded palynomorphs, with numerical returns ranging from very poor to good. In general, the preservation and numerical returns of the palynomorphs were poorer from the Big Fish River area samples. The sections contain reworked forms. These are particularly abundant in the Maastrichtian of the Police Island section and the Campanian and Maastrichtian of the Big Fish River area. The source for these reworked specimens contained Lower Carboniferous and Lower Cretaceous sediments. Topographically the source areas for these samples were low-lying. The sediments in the Big Fish River area and Atkinson Well indicate formation in a swampy area, as shown by the presence of Taxodiaceaepollenites hiatus. The Police Island samples contain only a small number of this species suggesting that the source area for these samples was drier. Dinoflagellatesare present at two levels in the Campanian of the Big Fish River area indicating at least two advances and retreats of the sea during the Campanian. All three sections span the Cretaceous/Tertiary boundary. (The section from the Big Fish River area extends from the Campanian to the Paleocene.) The location of the boundary is based on the disappearance of certain key taxa, particularly the aquiloid pollen and Wodehouseia spinata. The study indicates that the species Cingulatisporites scabratus may prove to be a useful Maastrichtian index fossil in the Arctic. There is a local reduction in the micro floral diversity close to the boundary suggesting a climatic deterioration at this time.