Summary of Arctic Geophysics

Abstract

The Cenozoic history of the Eurasian Basin is well understood because it involves the Eurasian (EU) and North American (NA) plates and is therefore constrained by data from more southerly regions and contains a readilly decipherable magnetic pattern. Reconstruction of the older portion of the Arctic Ocean is more difficult; however, information collected on ice station CESAR in 1983, interpreted in conjunction with regional geologic and geophysical data, provides insight into its oceanic affinities and age. A dredged outcrop of the Alpha ridge, consisted of weathered fragmental alkaline volcanic rocks. Refraction data reveal a thick crust nearly 40 km and a high velocity lower crust on this ridge. The basal layer velocity is typical of all plateaus known to be oceanic crust. It is hypothesized that Alpha Ridge therefore represents a late Cretaceous oceanic plateau. A more recent analogue is the Iceland-Faeroe Ridge. The magnetic information are shown to be consistent with this interpretation of oceanic crust. The Amerasia Basin is closed by rotating the Arctic-Alaska plate against NA during the Cretaceous. This reconstruction, its timing and its position are consistent with the geology of the Canadian Arctic Islands and Alaska.