ABSTRACT: The relative sea level history of southwestern Newfoundland: Implications for regional deglaciation

CGRG Bibliography of Canadian Geomorphology
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Abstract

Three relative sea level (RSL) curves are presented from St. George's Bay and the Humber Arm on the west coast of Newfoundland. Migration of the crustal forebulge, characteristic of areas peripheral to the Laurentide Ice Sheet, controls the RSL history of this part of Newfoundland. Previously published isobase maps show a pronounced tilt up to the north. Compilation of new and existing data from St. George=s Bay allows a separation of the sea level history between the northern and southern parts of the bay. Marine limit around St. George's Bay is about 45 m. Deglaciation may have been delayed in the north by several hundred years compared to the south. The southern part of St. George=s Bay, south of Bank Head, shows a steep Type B curve, dropping from the marine limit estimated at 14.0 ka to below modern sea level at about 13.0 ka. The northern part of the bay shows a well-constrained Type B curve. The curve is less steep than that to the south, dropping from the marine limit at about 13.4 ka, to below modern sea level at about 11.9 ka. Previous studies suggested a single curve described the sea level history adequately for this area. This study suggests that a single RSL curve for a large bay, such as St. George's Bay, that is oriented parallel to the direction of isostatic recovery is an over-simplified characterization of sea level history. The response of tidewater glaciers along the coastal margins of St. George's Bay during deglaciation to rapid sea level fall is uncertain. The seaward migration of the grounding line may have been sufficient to induce local reactivations of the ice front. A climatic forcing thus may not be required to explain late-glacial fluctuations of the ice front previously described in the area. The data shows northward forebulge migration, at an estimated rate of 35 km per 1000 years. These data are in accordance with a Type B RSL curve presented from the Humber Arm area, located 75 km north of St. George's Bay. This curve shows a transition to below modern sea level at 10.0 ka from a marine limit of 60 m asl dated at about 13.2 ka.

Bibliography of Canadian Geomorphology