The Yermak Plateau: Formed at a triple junction

Abstract

The Yermak Plateau is an arcuate marginal plateau located seaward of northwestern Spitsbergen. The plateau is divided into two zones based on bathymetric trends and magnetic characteristics that have roughly coincident boundaries. North of latitude 82°N where the bathymetric contours trend NE, the magnetic amplitudes are large, whereas the southern portion strikes NNW and exhibits a subdued magnetic signature. Beneath the northern section of the plateau crustal refraction velocities of 5.0 km s−1 underlain by 7.2 km s−1 are recorded, while farther south velocities of 4.3, 6.0, and 8.0 km s−1 are measured. The 6.0 km s −1 velocity is similar to ones reported on the continental shelf south of Spitsbergen. Dredged material, gravity, heat flow, and seismic reflection and refraction data indicate the northern region of the plateau is oceanic and formed in conjunction with the Morris Jesup Rise. In contrast, the southern section is thinned continental crust formed by the initial rifting process at a triple junction north of Greenland. Plate reconstructions for anomalies 24 and 13 are consistent with this interpretation. Little space is required for the Yermak Plateau at anomaly 24 because it is composed of oceanic and thinned continental crust. The development of the Yermak Plateau and the Morris Jesup Rise, paired aseismic ridges, took place when the North American, Eurasian, and Greenland plates were moving independently.