Abstract

We use a model of plate motions relative to major hotspots underneath the African, Indian, North American, South American, and Australian plates to compute the track of the Iceland hotspot after 130 Ma. The present-day hotspot is located under eastern Iceland offset about 240 km east of the Reykjanes and Kolbeinsey ridges. At 40 Ma, the Kangerlussuaq region of East Greenland would have been directly above the hotspot. The anomalous postdrift uplift of the East Greenland margin can also be explained by passage of the rifted margin over a hotspot. At 60 Ma, the Umanak Fjord region of the west coast of Greenland was above the hotspot, where picrites and hyaloclastites of nearby Disko Island are dated at ∼64 to 59 Ma. Our reconstruction shows Ellesmere Island above the hotspot between 130 and 100 Ma. Latest Albian to early Cenomanian volcanic rocks on Axel Heiberg Island and northern Ellesmere Island indicate a nearby hotspot at that time. At 130 Ma, our model locates the hotspot near the northern margin of Ellesmere Island, close to the intersection of the Alpha Ridge with the coast. The hotspot would have been located beneath the Arctic Alaska-Chukotka plate when it formed the Mendeleyev Ridge, and as the spreading center migrated over the hotspot, it transferred to the North American plate, where it formed the Alpha Ridge. Our model suggests that the initiation of the Iceland hotspot predates the opening of the North Atlantic by at least 70 m.y. and that the massive early Tertiary volcanism along the North Atlantic plate margins reflects the effect of rifting in the vicinity of existing thinned crust, rather than the arrival of a plume head.

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