Abstract

The East Greenland continental margin is inferred to have formed in three stages during the Tertiary evolution of the adjacent North Atlantic Ocean. The East Greenland basaltic volcanism occurred over a period of 2–3 Ma, which was just prior to the probable date of onset of seafloor spreading in the Early Eocene shortly before magnetic anomaly 24B (52 Ma). The associated coastal flexure is interpreted as marking the edge of a zone of stretched and thinned continental crust beneath the inner Denmark Strait shelf and Jan Mayen microcontinent; this represents a short-lived rifting phase just prior to break-up. According to the evolutionary model, the initial break-up produced the margins south of the Faeroe Transform Fault (68.5°N) and north of the Jan Mayen Fracture Zone (72°N), but in the intervening region the microcontinent remained attached to East Greenland. After break-up, the outer shelf of Denmark Strait formed from anomalously thick oceanic crust complementary to the Iceland-Faeroe Ridge. The Blosseville Kyst margin (68.5°N to 70°N) was initiated after anomaly 20 time (42 Ma) as the Jan Mayen microcontinent started to separate from Greenland with spreading on both sides. The new split occupied the line of the pre-existing coastal dyke swarm and flexure. The Liverpool Land margin (70°N to 72°N) was also initiated at this time, but the main separation of the northern part of the microcontinent only commenced after anomaly 7 time (26 Ma) when a single spreading axis was relocated west of the microcontinent.

It is suggested that the Blosseville lavas subsided during deposition by loading and slight crustal stretching. Doming occurred near Kangerdlugssuaq at the time of break-up. Otherwise the topography of the lavas remained subdued until the relocation of the spreading axis at 26 Ma, after which the main regional uplift took place.

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