Paleomagnetism of a Late Cretaceous island arc complex from South Sakhalin, East Asia - Convergent boundaries far away from the Asian continental margin?

The Hokkaido-Sakhalin fold system stretches for about 1500 km along the eastern coast of Asia and consists of several N-S trending tectonic belts. Studies in South Sakhalin show that the northern part of the Tonino-Aniva Peninsula (Ozersk unit) is a counterpart of the Tokoro belt on Hokkaido, Japan. In the eastern part of the Ozersk unit, 195 hand samples were sampled at 20 sites from Campanian-Maastrichtian tuffaceous siltstones and sandstones of the Chavka Formation of island arc affinity. Stepwise thermal demagnetization isolates a postfolding low- to intermediate-temperature component (B) of normal polarity. A high-temperature component (A) is isolated from about half the samples. Component A is mostly of reversed polarity: a few samples of normal polarity are found at three sites. (Author)