The Volcanism of the Circum-Artic: Implications for the Evolution of the Amerasia Basin
Christopher J. Cooper and Elisabeth Bjerkebæk
Statoil ASA, Stavanger, Norway.
Here we propose that the ~ 200 to 180 Ma volcanics of the landmasses surrounding the Amerasia Basin relate to the initiation of rifting within the region, an interpretation supported by Hettangian sediments which lie uncomformably within the onshore Banks Basin. Over the past 30 years the academic community has undertaken numerous studies of the magmatic bodies of the circum-Arctic and it is these datasets which we have analysed here. Embry & Osadetz (1987) were the first to note that the circum-Arctic volcanism falls into discrete cycles, reporting four age ranges of Valanginian to early Barremian, Late Barremian to Aptian, Late Aptian to Early Cenemonian and Late Cenemonian to Maastrichtian. They accounted for these episodes through invoking two periods of rifting, followed by break-up and sea-floor spreading until the Maastrichtian. Here we propose five cycles of volcanism, based on the present-day dataset, which we relate to the tectono-stratigraphic evolution of the Amerasia Basin. Following the lower Jurassic rift related magmatism, which exists on Amund Ringes (Sverdrup), Axel Heiberg Island (Sverdrup) and Franz Josef Land, no circum-Arctic volcanism occurred until ~ 140 Ma. Buchan & Ernst (2006) propose three successive cycles, following this re-initiation of melting, aged Hauterivian to early Barremian, late Barremian to Aptian and Albian to Cenemonian. We support these ages, noting their agreement with the sea-floor spreading duration presented in Embry and Dixon (1992). The youngest volcanism of the region which is alkali in composition is observed at the De Long Islands, the Alpha and Mendeleev ridges, Northern Ellesmere Island and Northern Greenland. We propose that this alkali volcanism results from a plume. Numerous studies have suggested that the high-standing Alpha and Mendeleev Ridges of the Amerasia Basin also result from a plume, a hypotheisis supported by seismic 1-D velocity depth profiles from the ridges. The alkali volcanism young’s east, that of the De Long Islands is aged ~ 125 to 105 Ma, whilst samples from the Mendeleev and Alpha ridges are aged 89 and 82 Ma respectively, finally that of Northern Ellesmere Island and Northern Greenland is aged between 86 and 57 Ma. This plume could at present reside under Iceland. Alkali volcanism aged between 55 and 33 Ma is observed in Southern Greenland, whilst the oldest exposed volcanics of Iceland are aged ~ 16 Ma.
AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.