Late Cretaceous paleomagnetism of the East Ranges island arc complex, Kamchatka: Implications for terrane movements and kinematics of the northwest Pacific

Citations Over TimeTop 21% of 1997 papers

Abstract

A Campanian‐lower Paleocene island arc complex was sampled for paleomagnetic studies at 12 sites in the East Ranges tectonic zone of Kamchatka. After thermal demagnetization, a reversed polarity characteristic remanent magnetization (ChRM) was isolated from most volcanoclastic and basaltic units as well as from lava debris from intraformational conglomerates. The fold and conglomerate tests are positive, and the ChRM in the studied rocks is likely primary. The formation‐mean inclination of 66.3°±3.7° corresponds to a paleolatitude of 48.7°±5.0°N which is about 20° lower than the Late Cretaceous North American reference values. Because northward displacement of the studied terrane is indicated by the paleomagnetic data, we examine several models of intraoceanic transport with the Pacific and/or Kula plates and coastwise transport after terrane accretion, far to the south of the present‐day position of Kamchatka. Our preferred interpretation is that the studied island arc complex accumulated at about 83–79 Ma; the island arc, to which the studied terrane had originally belonged, was active between this time and 65–60 Ma. According to geological data, the docking time nearly coincided with cessation of volcanic activity, and northward movement of the island arc took place simultaneously with the volcanic activity. The absolute motion of a subduction zone should have the same direction as the overriding plate; therefore, the subduction zone related to the East Ranges island arc is inferred to have moved northward with the Kula plate or with the Kula and Pacific plates, successively, consuming either the oceanic periphery of a continental plate or some unknown minor oceanic plate. This process went on until 65–55 Ma when the island arc and related subduction zone approached the continental margin and became extinct. The proposed models also place additional constraints on kinematics of the Kula‐Pacific transform plate boundary.

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