Paleomagnetism and tectonics of Karaginsky Island, Bering Sea

Abstract Rocks from Karaginsky accretionary prism (Karaginsky Island, Bering Sea) yield both prefolding (close to original) and postfolding magnetic vectors. The prefolding vectors suggest that the Maastrichtian–Paleocene volcanic–terrigenous sequences of Karaginsky Island formed at approximately 40°N to 50°N ( n = 45, D _G = 325, I _G = 57, K _G = 6, α_95G = 8, F _G = 15.06, D _S = 332, I _S = 63, K _S = 20, α_95S = 4.5, F _S = 0.3297, F _cr = 2.64) and were not originally part of either Eurasia ( F = 19, Δ F = 6.5) or North America ( F = 17, Δ F = 4.4). The geologic blocks rotated insignificantly counterclockwise about the horizontal plane, suggesting that the structure of Karaginsky Island arose without major strike-slip motions. Analysis of secondary magnetizations (for example, n = 28, D _G = 311, I _G = − 50, K _G = 9, α_95G = 8.7, F _G = 2.44; D _S = 293, I _S = − 41, K _S = 5, α_95S = 11, F _S = 12.04, F _cr = 2.65) reveals that the development of this framework involved at least two stages of deformation. During the second stage the sequences must have been tilted to west-northwest and northwest directions at 45–65°. This agrees with the northwest vergence of the structure of Karaginsky Island.