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Article Excerpt
(Received 14 April 2008; accepted in revised form 29 October 2008)
ABSTRACT. Palaeontological research on Herschel Island, Yukon, has yielded a diverse collection of Quaternary marine and terrestrial vertebrate fossils. The terrestrial faunal remains, which have largely been collected as allochthonous beach debris at Pauline Cove, are dominated by Yukon horse (Equus sp.), with fewer specimens of steppe bison (Bison priscus), proboscideans (Mammuthus primigenius and a single Mammut americanum specimen), and other large and medium-sized mammals. This pattern of a horse-dominated Late Pleistocene fauna is consistent with those from the North Slope of Alaska and further demonstrates that conditions in northernmost Beringia were more arid than those in interior areas such as Fairbanks or the Klondike. This paper presents new AMS radiocarbon dates on terrestrial vertebrate fossils and peat from the island that span the range from greater than 53 000 to modern [.sup.14]C yr BP. When considered with other data from the region, our new radiocarbon-dated fauna cannot adequately resolve whether the Herschel Island ice-thrust ridge was formed during the Early Wisconsinan or the Late Wisconsinan advance of the Laurentide Ice Sheet over the Yukon Coastal Plain.
Key words: Pleistocene, Yukon, Herschel Island, palaeontology, Beringia, mammals, fossils, Buckland Glaciation, Beaufort Shelf, chronology
RESUME. Des fouilles paleontologiques realisees sur l'ile Herschel, au Yukon, ont permis de prelever une collection variee de fossiles marins et de fossiles vertebres terrestres du quaternaire. Les restes de faune terrestre, qui ont surtout ete ramasses sous la forme de debris de plage allochtones a Pauline Cove, prennent la forme de restes de chevaux du Yukon en predominance (Equus sp.), parsemes de quelques specimens de bisons priscus (Bison priscus), de proboscidiens (Mammuthus primigenius et d'un seul specimen de Mammut americanum), ainsi que d'autres mammiferes de taille moyenne et de grande taille. La predominance de faune du type cheval du Pleistocene tardif correspond a celle enregistree sur le versant nord de l'Alaska et montre encore une fois que les conditions qui regnaient dans la partie la plus au nord de la Beringie etaient plus arides que les conditions qui prevalaient dans les regions de l'interieur, comme a Fairbanks ou au Klondike. Dans ce document, nous presentons de nouvelles dates etablies par le radiocarbone SMA quant aux fossiles de vertebres terrestres et a la tourbe de Pile, dates allant de plus de 53 000 [.sup.14]C annees BP a l'ere moderne. Lorsque ces donnees sont considerees a la lumiere d'autres donnees de la region, la nouvelle faune datee par le radiocarbone ne nous permet pas de determiner adequatement si la dorsale decoulant de la poussee des glaces de l'ile Herschel a ete formee pendant la progression du Wisconsinien precoce ou du Wisconsinien tardif de la nappe glaciaire laurentienne sur la plaine cotiere du Yukon.
Mots cles: Pleistocene, Yukon, ile Herschel, paleontologie, Beringie, mammiferes, fossiles, glaciation de Buckland, plateforme de Beaufort, chronologie
Traduit pour la revue Arctic par Nicole Giguere.
INTRODUCTION
Quaternary research on Herschel Island, Yukon, plays a key role in reconstructing the Pleistocene glacial chronology and palaeoenvironments of the Beaufort Sea coastlands. Mackay's (1959) pioneering research suggested that Herschel Island is composed of Beaufort Sea shelf sediments that were upthrust into a ridge by the northwestern lobe of the Laurentide Ice Sheet (LIS). Subsequent surficial geological mapping on the Yukon Coastal Plain and adjacent areas, including Herschel Island, indicated this area was covered by the "Buckland Glaciation," and Rampton (1982) postulated an Early Wisconsinan (ca. 90-65 ka) age for this ice advance (Fig. 1). Since these early studies, much research has attempted to resolve the chronology of the northwest margin of the LIS, especially in the Mackenzie Delta, Mackenzie Mountains, and Tuktoyaktuk coastlands. However, limited work has been conducted on the Yukon Coastal Plain or Herschel Island in recent years, and there is no definitive model of how the Quaternary deposits found there correlate with those from other areas covered by the northwest margin of the LIS. Furthermore, Herschel Island has yielded an impressive Quaternary fossil assemblage, and terrestrial mammal remains recovered there are considered to represent a far northeast corner of the Holarctic "mammoth-steppe" biome (Guthrie, 1990).
[FIGURE 1 OMITTED]
In this paper, we present new AMS radiocarbon ages from a variety of Pleistocene fauna that have important implications for the chronology of Herschel Island's glacier ice-thrust origin and regional palaeoenvironments of the Beaufort Sea coastlands.
The Study Area
Herschel Island or Qikiqtaruk is a Yukon Territorial Park, 100 [km.sup.2] in area, 3 km off the north coast of mainland Yukon Territory in the southern Beaufort Sea (Fig. 1 inset). The coastal shelf between the mainland and Herschel Island is submerged by as little as 2 m, and recent assessments suggest that the island was connected to the mainland as recently as ~650 years ago (Burn, 2009). The maximum elevation on the island is approximately 185 m above present sea level. Herschel Island is composed of a variety of ice-rich marine and terrestrial sediments that are typically deformed. Mackay (1959) suggested that the volume of the submerged Herschel Basin on the Beaufort Shelf is similar to that of Herschel Island, providing further evidence to support the proposed ice-thrust origin of Herschel Island. Although the island per se (a landmass surrounded by water) may have been formed only in the last two millennia following marine transgression...
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