Glacial and Sea Level History of Lowther and Griffith Islands, Northwest Territories: A Hint of Tectonics

Abstract

Lowther and Griffith islands, in the centre of Parry Channel, were overrun by the Laurentide Ice Sheet early in the last glaciation. Northeastward Laurentide ice flow persisted across at least Lowther Island until early Holocene déglaciation. Well constrained postglacial emergence curves for the islands confirm a southward dip of raised shorelines, contrary to the dip expected from the ice load configuration. This and previously reported incongruities may indicate regionally extensive tectonic complications of postglacial rebound aligned with major structural elements in the central Canadian Arctic Islands.Les îles Lowther et Griffith, situées au centre du chenal de Parry, ont été recouvertes par l'Inlandsis laurentidien tôt au cours de la dernière glaciation. Un écoulement glaciaire vers le nord-ouest a persisté à l'île Lowther, tout au moins, jusqu'à la déglaciation au début de l'Holocène. Les courbes d'émersion bien identifiées de l'île confirment une inclinaison des plages soulevées vers le sud, contrairement à l'inclinaison prévue à partir de la configuration de la charge glaciaire. Ce fait ainsi que d'autres anomalies déjà signalées pourraient indiquer des complications d'ordre tectonique à l'échelle régionale au moment du relèvement isostatique postglaciaire correspondant aux principaux éléments structuraux des îles du centre de l'Arctique canadien.Die im Zentrum des Parry-Kanals gelegenen Insein Lowther und Griffith wurden zu Beginn der letzten Vereisung durch die laurentidische Eisdecke bedeckt. Der laurentidische EisfluB in Richtung Nordosten hat zumindest ùber die Insel Lowther hinweg bis zur frùhen Holozan-Enteisung gedauert. Die deutlich erkennbaren postglazialen Auftauchkurven der Insein bestâtigen eine Neigung der angehobenen Kùstenlinien nach Sùden, entgegen der Neigung, die man entsprechend der Eismassenkonfiguration erwartet hàtte. Dies und zuvor schon aufgezeigte Anomalien kônnten auf regional extensive tektonische Komplikationen beim postglazialen isostatischen Rùckprall hinweisen, entsprechend den wichtigsten strukturellen Elementen der Insein im Zentrum der kana-dischen Arktis

Raised Gravel Beaches as Proxy Indicators of Past Sea-Ice and Wave Conditions, Lowther Island, Canadian Arctic Archipelago

“…notwithstanding the issue of marine reservoir corrections for whale bone radiocarbon dates in the CAA (cf. Dyke, 1993), there is very good correspondence between index points derived from driftwood and whale bone on Lowther Island. As a result, the emergence curve is well constrained, especially below 60 m asl, and "among the best available for the central Arctic Islands" (Dyke, 1993:141).…”

“…3; Dyke et al, 1991;Dyke, 1993). One additional bowhead whale ear bone not included in previous compilations provided a radiocarbon age of 4295 ± 20 14 C BP (UCIAMS-29238), corrected for 13 C fractionation to a base of -25‰.…”

“…3). (Dyke, 1993; this study). thick black lines along the horizontal axis represent periods of light sea-ice conditions as derived from the spatio-temporal distribution of bowhead whale bones on raised marine deposits of Barrow Strait and Peel Sound (Dyke et al 1996).…”

“…The island has a thin but extensive till cover that was deposited by the Laurentide Ice Sheet during the Wisconsinan glaciation. the till has an average of 10% to 50% stone content, mostly sourced from local carbonate rocks (Dyke, 1993). Taylor (1978b) presents a general overview of the coastal geomorphology of Lowther Island.…”

Comment: Holocene palaeoceanographic changes in Barrow Strait, Canadian Arctic: foraminiferal evidence. T. R. Gregory, C. W. Smart, M. B. Hart, G. MassÉ, L. L. Vare and S. T. Belt (2010). Journal of Quaternary Science 25: 903–910

“…(2010) make little or no mention of these widely recognised events, nor do they consider in detail these previously proposed regional changes when developing their own interpretations. For example, they ignore entirely previously published and well‐constrained emergence curves for their study area (Dyke, 1983, 1987, 1993, 1999; Dyke et al ., 1991, 1992), rather citing an ‘exceptional’ emergence rate from a location some 700 km distant (England, 1997) that was subsequently revised (England, 1999). In a region spanning ∼2.5 million km 2 , single and distant emergence curves should not be assumed to be meaningful, considering the critical role water depth plays in CAA circulation (Jones and Coote, 1980; Melling, 2000; Michel et al ., 2006).…”