Morphology and magnetic anomalies north of Iceland

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P.R. Vogt
G.L. Johnson
L. Kristjansson

Abstract

Detailed low-level aeromagnetic data between Iceland and 70° N are combined with published bathymetric, seismic reflection, and other data to yield a new tectonic synthesis of this region of anomalously shallow sea floor. On Kolbeinsey Ridge short transform faults have repeatedly formed and disappeared over the last 7-8 Ma. Spreading from Kolbeinsey Ridge began about anomaly 6C time (24 Ma); total opening rates increased from 1.5 cm/a to 2 cm/a about 12-13 Ma ago. The Intermediate-Iceland- Plateau extinct axis thus does not exist, and oceanic crust must underlie much of the Greenland margin, perhaps up to the coast itself. This in turn implies locally over 100 km prograding, much of which probably occurred during Plio-Pleistocene glacial periods. The Iceland shelf has been prograded locally 25 km or more. The plate acceleration a 12-13 Ma ago correlates with time-transgressive basement ridges or escarpments previously found on Reykjanes Ridge and here identified north of Iceland as well. The features are proposed to reflect an abrupt mid-Miocene increase in discharge from the Iceland plume. Other time-transgressive basement structures are found on younger Kolbeinsey Ridge crust. Lower Tertiary anomalies 13 to at least 22 are identified in the Denmark Straits, ruling out the hypothesis that the Iceland platform resulted from a westward jump of the spreading center at anomaly 7 time. The magnetic smooth zones being formed where the Kolbeinsey and Reykjanes Ridges enter Iceland have a multiple origin: degassing at depths less than 500 m, coupled with crustal reheating as a result of burial by sediment may be the most important processes.


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Vogt, P.R., G.L. Johnson, and L. Kristjansson. 1980. “Morphology and Magnetic Anomalies North of Iceland”. Journal of Geophysics 47 (1), 67-80. https://journal.geophysicsjournal.com/JofG/article/view/74.
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