CGRG Bibliography of Canadian Geomorphology
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Author : Stea, R.R; Scott, D.B.; Godfrey-Smith, D.; Mott, R.J.; and Dredge, L.
Date : 2003.
Title : Sangamonian (Mis 5) sea levels of +20 m in Maritime Canada.
Publication : XVI INQUA Congress. July 23 - 30, 2003. Reno Hilton Resort & Conference Center Reno, Nevada USA .
Issue :
Page(s) :
Abstract
During the last interglacial, relative sea level (RSL) in eastern Canada was at least between +4 and +6m, based on the elevation of wave-cut rock platforms. Sections in Nova Scotia exposed during a severe winter storm revealed a rock platform at + 4m, overlain by two peat layers, and then a well-sorted, parallel-laminated sand to +12 m, capped by Wisconsinan till. The pre-Wisconsinan sand unit can be traced along the northern coast of Nova Scotia and attains an elevation of +25 m. The overlying Wisconsinan till contains a reworked interglacial molluscan fauna including Mercenaria mercenaria and Ostrea. OSL dating of the base of the sand unit at Cape George, Nova Scotia, produced an age of 115 ± 10 ka. Ostrea virginica shells were found in a correlative sand unit on the Īles de le Madeleine, Quebec, where the sand and wave-cut platforms indicate an interglacial sea level between +13 and +20 m. Here, salt tectonics was invoked to explain the apparently anomalous interglacial sea levels. Sections along the Bras D'Or Lakes in Cape Breton reveal a organic silt unit with marine diatoms underneath till, which attains an elevation of +18m. The anomalous relative sea-level at this locality was explained by glacio-isostatic subsidence in front of an advancing ice sheet or an ice dam. Similar arguments were advanced for a massive sand unit at Salmon River, in southern Nova Scotia, which contains an interglacial marine molluscan fauna indicating a paleo-sea level between + 16 and + 31 m. Local tectonics or glacio-isostasy cannot explain the age, sedimentology and distribution of these marine sand units and, therefore, we must conclude that interglacial sea-levels were higher than previously thought. Pollen studies and new OSL data suggest that the highest RSL occurred during a cooler climate interval (MIS 5a?) after the thermal maximum. The stratigraphic record suggests an RSL oscillation with an early rise to ~4-6 m (rock bench), RSL fall (peat layer), and then subsequent RSL rise (sand units) to as high as 20 m. This RSL record suggests the combined effects of climate change and forebulge collapse.
Bibliography of Canadian Geomorphology