Quaternary geology and glacial history of Bylot Island, Northwest Territories

Abstract

The Quaternary geology of Bylot Island records glaciation by regional ice sheets and by local mountain glaciers, and marine and glaciomarine sedimentation around its margins. The geological evidence for the last major foreign glaciation, Eclipse glaciation, is widespread in surficial deposits and landforms and is used as a basis for recognition of other glacial events and for establishing their relative ages. Four distinct foreign glaciations are recognized. The oldest and most extensive, named Baffin glaciation, occurred prior to a period of interglacial weathering, named Salmon River interglaciation, and ice could have moved northward across the topographic divide of Bylot Island. During the later Eclipse glaciation, ice was less extensive, although it fully occupied the channels around the island and attained elevations of 270 to 370 m a.s.l. from 10 to 20 km inland on the south coast, and 500 to 600 m a.s.l. against the northern coastal mountains. Eclipse glaciation occurred prior to 43 000 radiocarbon years ago and is older than marine shells having amino acid ratios (D-alloisoleucine to L-isoleucine) of 0.20 to 0.25. Evidence of the younger Button glaciation is restricted to coastal areas of Bylot Island below 140 m a.s.l., and foreign ice was restricted to the marine channels and was likely floating. Button drift is bounded stratigraphically by shells having amino acid ratios of about 0.15 and 0.10. Cape Hatt glaciation is of Late Wisconsinan or early Holocene age during which time ice extended across Baffin Island to the northern mouth of Milne Inlet. Three periods of native glaciation are known. The oldest, named Bylot glaciation, was most extensive and covered most of the island prior to Baffin glaciation. Late during Eclipse glaciation, native glaciers that had been dammed on the island by foreign ice underwent major expansion as part of Aktineq glacial phase as they re-established normal outward directions of flow. Modern glaciers appear to be either stationary at, or retreating from, Neoglacial maximum positions attained within the last 100 years that represent their greatest extent since Eclipse glaciation. Five periods of change in relative sea level are recognized, the oldest of which predates Salmon River interglaciation and is represented in sections by marine sediments containing in situ shells with amino acid ratios of 0.55 to 0.60. Younger marine sediments of pre-Eclipse age occur in two stratigraphic sections and contain shells having amino acid ratios of about 0.4 to 0.35. Surficial marine sediments of pre-Holocene age are related to periods of higher relative sea level subsequent to Eclipse glaciation and to Button glaciation. They contain shells having amino acid ratios of about 0.2 and 0.1, respectively. Eclipse marine sediments may extend to 90 m a.s.l. near Canada Point. On northern Bylot Island, Button marine sediments extend to 35 m a.s.l. Holocene emergence is 100 mat the southern end of Milne Inlet, 80 mat Cape Hatt, 50 to 60 m near Pond Inlet townsite, and 35 to 45 m on southern Bylot Island. No raised Holocene marine sediments are known on northern Bylot Island and there the modern coast appears to be submerging.

Long‐term sensitivity of a High Arctic wetland to Holocene climate change

“…The change from inferred drier soil moisture conditions during Period II to wetter conditions during Period I is also supported by evidence for a pronounced climatic effect at other High Arctic sites. Period I is coeval with geomorphological evidence for the effects of the LIA in the Qunguliqtut Valley (Klassen 1993;Allard 1996) and paleolimnological evidence for LIA cooling from Baffin Island (Hughen et al 2000) and Ellesmere Island (Lamoureux & Bradley 1996). The direction of change is also consistent with evidence for colder though wetter LIA climatic conditions from Cornwall Island in the Canadian Arctic Archipelago (Lamoureux 2000;Lamoureux et al 2001) and from central west Greenland (Bennike 1992).…”

“…1995), which occur on Bylot Island adjacent to and within the catchment area of the sampling site (Klassen 1993). A sediment sample of c. 2 cm 3 was washed in distilled water and filtered through a 0.3-mm mesh sieve.…”

The Laurentide and Innuitian ice sheets during the Last Glacial Maximum

“…The general impression arising from these studies, therefore, is that Laurentide ice extended to near the fiord mouths along eastern Baffin Island during both the Early Wisconsinan and the Late Wisconsinan, but the Late Wisconsinan fiord ice was thinner and of lower gradient. Klassen (1993) placed the Late Wisconsinan Laurentide ice limit on northern Baffin Island to the south of Bylot Island, slightly beyond the position illustrated by Dyke and Prest (1987), and concluded that Late Wisconsinan alpine glaciers on Bylot Island were of similar size to those of the present. He assigned the Eclipse Moraines along the south shore of Lancaster Sound on Bylot Island to the Early Wisconsinan along with younger moraines between the Eclipse position and his Late Wisconsinan limit.…”

“…First, there are several natural processes that can render exposure ages too young or too old. Second, the fiord-mouth moraine system between the Duval Moraines in the south and the Eclipse Moraines along Lancaster Sound in the north (Klassen, 1993) are nowhere directly associated with ice-contact marine deposits of Late Wisconsinan age, despite the common occurrence of ice-contact raised deltas along them. Furthermore, many raised marine deposits thought in earlier studies to be associated with these moraines have yielded pre-Late Wisconsinan radiocarbon ages (Andrews, 1989; see for date list).…”

Modern to millennium-old greenhouse gases emitted from ponds and lakes of the Eastern Canadian Arctic (Bylot Island, Nunavut)

“…The Byam Martin Mountains run southeast-northwest across the island, and the plains that stretch out on either side of the mountains belong to the Arctic Lowlands physiographic region (Bostock, 1970). The numerous valleys formed in the lowlands were shaped during the successive Pleistocene glaciations (Klassen, 1993). Since the Holocene, these valleys developed highly dynamic biogeosystems rich in permafrost ground ice, peat, and aquatic environments (Fortier and Allard, 2004).…”