Alpha-Mendeleev Ridge 

(Late Early Cretaceous to Paleogene) 

(Arctic Ocean, Chukchi Sea, and adjacent areas, unit TKvm)

Consists chiefly of remarkably homogeneous crust that, on the basis of magnetic, gravity, and seismic-
refraction data, is as much as 38 km thick at the ridge crest. Magsat data show that the ridge forms 
one of strongest magnetic anomalies on Earth and may be a volcanic edifice. Magsat data suggest 
that the highly magnetic rocks of Alpha Ridge continue into the Mendeleev Ridge, where they 
thin and wedge out near the continental margin of the East Siberian Sea. Four cores and a dredge 
sample from the North American end of the Alpha Ridge show that the crust is overlain by a few 
hundred meters of sediment that includes Campanian-Maastrichtian black organic mud and 
Maastrichtian-Eocene biosiliceous ooze. In one area near the ridge crest, the sedimentary section 
contains Paleocene and Eocene volcaniclastic alkalic basalt that was erupted within a few hundred 
meters of the sea floor. Basalt chemistry suggests formation at a within-plate hotspot, but the 
composition and tectonic character of the homogeneous part of the ridge is unknown. 
REFERENCES: Taylor, 1983; Jackson, 1985; Mudie and others, 1986; Weber, 1986; Van 
Wagoner and others, 1986