Abstract
This study investigates the postglacial sea-level history of eastern Cumberland Peninsula, a region of Baffin Island, Nunavut, where submerged terraces were documented in the 1970s. The elevation gradient of emerged postglacial marine-limit deltas and fiord-head moraines led Arthur Dyke to propose a conceptual model for continuous postglacial submergence of the eastern peninsula. Multibeam mapping over the past decade has revealed eight unequivocal submerged deltas at 19–45 m below present sea level (b.s.l.) and other relict shore-zone landforms (boulder barricade, spits, and sill platform) at 16–51 m b.s.l. Over a distance of 115 km from Qikiqtarjuaq to Cape Dyer, the submerged coastal features increase in depth toward the east, with a slope (0.36 m/km) less than that of the marine-limit shoreline previously documented (0.58–0.62 m/km). The submerged ice-proximal deltas, deglacial ice limits, and radiocarbon ages constrain the postglacial lowstand between 9.9 and 1.4 ka cal BP. The glacial-isostatic model ICE-7G_NA (VM7) computes a lowstand relative sea level at 8.0 ka, the depth of which increases eastward at 0.28 m/km. The difference between observed and model-derived lowstand depths ranges from 1 m in the west to 10 m in the east and the predicted tilt is significantly less than observed (p = 0.0008). The model results, emerging data on Holocene glacial readvances on eastern Baffin Island, and evidence for proglacial delta formation point to a Cockburn (9.5–8.2 ka) age for the lowstand, most likely later in this range. This study confirms the 1970s conceptual model of postglacial submergence in outer Cumberland Peninsula and provides field evidence for further refinement of glacial-isostatic adjustment models.
Highlights
Submerged postglacial coastal landforms are predicted by glacial-isostatic adjustment (GIA) models (Quinlan and Beaumont 1981; Tarasov and Peltier 2004) and documented around the margins of lateQuaternary ice sheets (e.g., Hill et al 1985; Shaw and Forbes 1995). Andrews (1980) identified easternmost Baffin Island as a region with potential for a preserved Holocene submerged sea-level record.At the northeastern limit of the Laurentide Ice Sheet (LIS) in the Canadian Arctic, Baffin Island (Fig. 1) has a postglacial history of punctuated ice recession, isostatic adjustment, and relative sea level (RSL)change
With the use of multibeam echosounder technology, the first highresolution maps of these uncharted waters in eastern Cumberland Peninsula were surveyed aboard MV
The results of these surveys were the discovery and documentation of eight submerged ice-proximal deltas (19-45 m bsl), and other submerged coastal landforms. Each of these represents a depth of formation at a lowstand in the sea-level history, and can be used to constrain the shoreline gradient resulting from GIA across northern and eastern Cumberland Peninsula
Summary
Submerged postglacial coastal landforms are predicted by glacial-isostatic adjustment (GIA) models (Quinlan and Beaumont 1981; Tarasov and Peltier 2004) and documented around the margins of lateQuaternary ice sheets (e.g., Hill et al 1985; Shaw and Forbes 1995). Andrews (1980) identified easternmost Baffin Island as a region with potential for a preserved Holocene submerged sea-level record.At the northeastern limit of the Laurentide Ice Sheet (LIS) in the Canadian Arctic, Baffin Island (Fig. 1) has a postglacial history of punctuated ice recession, isostatic adjustment, and relative sea level (RSL)change. At the northeastern limit of the Laurentide Ice Sheet (LIS) in the Canadian Arctic, Baffin Island (Fig. 1) has a postglacial history of punctuated ice recession, isostatic adjustment, and relative sea level (RSL). Synchronous early Holocene raised deltas at the postglacial marine limit indicate an eastwarddipping shoreline with a gradient of 0.58-0.62 m/km, hypothesized to continue below sea level in eastern Cumberland Peninsula (Fig. 2; Dyke 1979; Andrews 1980, 1989; Clark 1980). The absence of documented raised early Holocene marine features, a few depth soundings of submarine terraces in fiords, and output from GIA models all support the hypothesis of postglacial submergence in eastern Cumberland Peninsula (Miller and Dyke 1974; Miller 1975; Peltier 2020). Considerable additional information on the distribution of raised marine shorelines and late glacial ice margins in southern and eastern Cumberland Peninsula has been published since
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