Preglacial and Interglacial Environments of Banks Island: Pollen and Macrofossils from Duck Hawk Bluffs and Related Sites

Abstract

Sediments ranging in age from Tertiary to Late Quaternary are exposed at Duck Hawk Bluffs near Sachs Harbour on Banks Island (NWT). Fossil pollen and macrofossils of plants and arthropods from various nonglacial sediments at Duck Hawk Bluffs and related sites on Banks and Victoria islands make it possible to infer some of the climatic/biotic changes during that time span. At the time of deposition of the Miocene-Pliocene Beaufort Formation, southern Banks Island supported a rich coniferous forest, containing several species of conifers and various hardwoods. An upper member of the Beaufort Fm. is characterized by a more depauperate coniferous forest assemblage, yet still contains plants now foreign to the entire NWT. The late Tertiary/early Quaternary Worth Point Formation was deposited when larch-dominated forest-tundra characterized southern Banks Island. Larch may have grown on the island during the following Morgan Bluffs Interglaciation (>730 ka), but in other respects the flora and fauna of that time seem to have been low Arctic in character. Similar conditions existed during the Cape Collinson Interglaciation ( = Sangamon), though by that time, coniferous trees had definitely disappeared from the island.Les falaises Duck Hawk, près de Sachs Harbour, présentent des sédiments dont l'âge varie du Tertiaire jusqu'au Quaternaire supérieur. Le pollen et les macrorestes de végétaux et d'animaux fossiles, prélevés dans divers sédiments non glaciaires dans les falaises Duck Hawk et d'autres sites associés dans les îles de Banks et Victoria, enregistrent des variations climatiques et biotiques au cours de cette période. Au moment de la mise en place des dépôts miocènes-pliocènes de la Formation de Beaufort, une forêt coniférienne, composée de plusieurs espèces de conifères et de divers feuillus, existait au sud de l'île de Banks. Un membre supérieur de la Formation de Beaufort est caractérisé par une forêt coniférienne appauvrie bien que plusieurs plantes, maintenant disparues de l'ensemble des T.N.-O., ont été identifées. La Formation de Worth Point, datant de la fin du Tertiaire et du Quaternaire inférieur, a été mise en place lorsqu'une toundra forestière, dominée par le mélèze, caractérisait l'île de Banks méridionale. Le mélèze croissait peut-être dans l'île lors de l'interglaciaire subséquent de Morgan Bluffs (>730 ka BP), mais les autres indicateurs permettent de croire que la faune et la flore étaient caractéristiques de celle du bas Arctique. Des conditions semblables ont existé lors de l'interglaciaire de Cape Collinson ( = Sangamon), bien qu'à ce moment les conifères avaient définitivement disparu de l'île.An den Steilkùsten von Duck Hawk in der Nâhe von Sachs Harbour auf der Insel Banks (Nord-West-Territorien) befinden sich Sedimente, deren Datierung vom Tertiar bis zum spâten Quaternàr reicht. Fossiler Pollen und Makrofossile von Pflanzen und GliederfùBern von verschiedenen nichtglazialen Sedimenten der Steilkùsten von Duck Hawk und verwandten Standorten auf den Insein Banks und Victoria erlauben, auf e...

Quaternary geology of the Duck Hawk Bluffs, southwest Banks Island, Arctic Canada: a re-investigation of a critical terrestrial type locality for glacial and interglacial events bordering the Arctic Ocean

“…The largest concentrations of tree fragments and 177 stumps occur in coarser grained gravelly beds, particularly in matrix-supported gravel with sand, silt and 178 clay intraclasts. The floral and faunal assemblages within LFA 1 are diverse, as illustrated by lists 179 reported in Roy and Hills (1972), Hills et al (1974), Hills (1975), Matthews et al (1986) and Matthews 180 (1987). 181…”

“…The general lack of scour fills and an overall fining-upward 315 is indicative of an aggrading system initially characterized by high magnitude/high frequency events that 316 were gradually replaced by low magnitude/high frequency events (Marren 2005 The crudely bedded organic detritus and degraded tree fragments (stumps) in LFA 1 are clearly 326 reworked (cf. Matthews et al 1986;Fyles 1990;Vincent 1990). The finer grained detritus was deposited 327 in concentrated pockets during waning flow stages, whereas horizons of logs and larger tree fragments 328…”

Stratigraphy and Paleoecology of Quaternary Sediments Along Pasley River, Boothia Peninsula, Central Canadian Arctic

“…Supporting this conclusion is that needles of spruce (Picea), larch (Larix) and hemlock (Tsuga) (see Table IV) are also known to occur in the Miocene Beaufort Formation on Banks Island (MATTHEWS et al, 1986), and some other plants listed in Table IV, e.g., Hypericum and Selaginella ruprestris (Fig. 12h, 12f) have FIGURE 11.…”

“…2b) that parallel those of other plant taxa that occur commonly in the Beaufort Formation (HILLS, 1975 ;HILLS and MATTHEWS, 1974 ;MAT-THEWS, 1987 ;MATTHEWS et al, 1986). Such plants are too temperate in their distribution to have ever occurred in the Arctic Archipelago during the Pleistocene.…”

Glaciotectonic deformation and reinterpretation of the Worth Point stratigraphic sequence: Banks Island, NT, Canada

“…The framework documented up to eight continental glaciations and five interglaciations associated with multiple marine transgression/regression cycles that span the entire Pleistocene Vincent, 1990;Barendregt et al, 1998). Stratigraphic units exposed at Worth Point, southwest Banks Island, form a critical type section reported to include a 'layer-cake' sequence of preglacial organics assigned to the Worth Point Fm, till from the earliest glaciation on Banks Island, and marine deposits from a glacioisostatically forced marinetransgression during an intermediate glaciation (Vincent, 1982(Vincent, , 1983(Vincent, , 1984(Vincent, , 1989(Vincent, , 1990(Vincent, , 1992Vincent et al, 1984;Matthews et al, 1986;Barendregt et al, 1998). Magnetostratigraphic analyses of the Pleistocene units identified the BruhneseMatuyama magnetic reversal (0.78 Ma) at the contact between the Worth Point Fm and overlying till, forming an important marker horizon that permitted long distance correlations between the Banks Island framework, magnetically constrained Arctic Ocean records, and widespread North American Quaternary marine and terrestrial records (Clark et al, 1984;Barendregt et al, 1998;Darby, 2003;Ehlers and Gibbard, 2004;Ehlers et al, 2011).…”