Abstract

Sediments exposed along the outer coast of the Qivitu Peninsula record the advances and retreats of glaciers in the fiords bordering the peninsula and accompanying sea-level fluctuations during the Quaternary. Seven main lithofacies and 21 subfacies are recognized, based on texture, color, bed thickness and lateral extent, internal structures, and abundance of macrofossils. In contrast to earlier work in the area, the interpretation of lithofacies genesis using a model of fiord glaciomarine sedimentation suggests that all lithofacies are of marine or glaciomarine origin with no evidence of grounded ice extending seaward of the peninsula. The abundance and diversity of benthic foraminifera in selected samples and in situ subarctic molluscs shows that relatively warm water was present along the east Baffin Island coast during several periods of extensive fiord glaciers. Analysis of upward facies transitions in 54 stratigraphic sections suggests that facies sequences are cyclical. These sedimentation cycles are interpreted in terms of glacier-sea-level responses during glacial/interglacial cycles.

Detailed relative time control for the lithofacies sequence is provided by time-dependent amino-acid ratios on the common shell fragments in many stratigraphic units. Because the stratigraphic sequence is marked by significant unconformities due to relative sea-level regressions near the end of each glacial sedimentation cycle, amino-acid ratios on molluscs contemporaneous with particular cycles are statistically similar and distinct from ratios for older and younger cycles. Thus, although few stratigraphic units can be physically traced for more than 0.5 km, aminozones based on groups of animo-acid ratios allow chronocorrelation and relative dating of units in each sedimentation cycle.

The Qivitu stratigraphic sequence is divided into two formations consisting of a total of seven members for which formal names are proposed. Sediments predating the two most recent interglacials are lithologically similar to later beds, suggesting that events during these earlier periods were of the same character as those of later glacial/interglacial cycles. Biostratigraphic evidence suggests that a relatively mild climate prevailed in this region during the Clyde and Ayr Lake glaciations and intervening Cape Broughton aquatherm. The Quajon interstade is correlative With the marine sediments deposited near the end of the Ayr Lake glaciation rather than the Cape Broughton aquatherm. Soil horizons indicate regressions at the end of the Cape Broughton aquatherm and Ayr Lake glaciation, and pollen assemblages suggest that the terrestrial climate may have been warmer than the present climate. A reinterpretation of U-series dates and amino-acid ratios on shells suggests that the Cape Broughton aquatherm and earlier events predate marine oxygen-isotope substage 5e. The Ayr Lake glaciation may have occurred well before the major interglacial-glacial transition in more temperate latitudes, but evidence from ocean cores in the North Atlantic and ice cores from Greenland and Devon Island supports the interpretation of warm-water incursions into Baffin Bay during this ice advance following substage 5e. By inference, relative sea level during the period following the Ary Lake glaciation was lower than present sea level, and glacier extent was restricted; no evidence of an exceptionally cold, dry climate has been found, however. Distal glaciomarine sediments in the upper coastal cliffs suggest a limited readvance of fiord glaciers prior to the Holocene. Near the beginning of the Holocene (10,000 yr B.P.), warmer water extended into the area as relative sea level fell and subsequently rose again to 15 m about 8,200 yr B.P. Pollen assemblages in peat horizons suggest that during the earliest Holocene, a climate milder than that of the present day existed. Local deposition of eolian and soliflucted sediment may indicat deteriorating climate in late Holocene time.

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