Paleomagnetism and geochronology of the Late Cretaceous‐Paleogene island arc complex of the Kronotsky Peninsula, Kamchatka, Russia: Kinematic implications

The remnants of ancient island arcs are exposed in the Achayvayam‐Valagina and East Peninsulas tectonic zones of the Olutor‐Kamchatka region, northeast Russia. Geochemically, Late Cretaceous to Paleogene island arc complexes of the East Peninsulas zone are similar to intraoceanic island arcs, and the East Peninsulas zone is regarded as the extinct Kronotsky island arc. Paleomagnetic and biostratigraphic studies of Late Cretaceous and Paleogene island arc rocks were carried out at 21 sites in the eastern part of the Kronotsky Peninsula, which belongs to the East Peninsulas zone. Characteristic remanent magnetizations of both polarities isolated from most sites pass reversal and fold tests; the Cretaceous result is also supported by a positive conglomerate test on lava boulders from an intraformational conglomerate. Mean inclinations of Late Cretaceous, Ypresian and Bartonian rocks correspond to paleolatitudes of 44.8° ± 8.0°N, 38.6° ± 3.5°N, and 45.1° ± 7.0°N, respectively. These values are ∼20° lower than the corresponding reference values for the North American plate for the Cretaceous and Ypresian and ∼14° lower for the Bartonian. Therefore northward transport of the Kronotsky island arc is indicated. Kinematic evolution of the Kronotsky island arc in the Late Cretaceous‐Paleogene was reconstructed using published kinematic parameters. In addition, we incorporated into analysis the geological and published paleomagnetic data for the Late Cretaceous and Tertiary island arc complexes of the Cape Kamchatka Peninsula from the East Peninsulas zone and the Late Cretaceous island‐arc complexes of the Achayvayam‐Valagina zone. As a result, two alternative scenarios of kinematic evolution for the Kronotsky island arc are proposed. According to both of them, the Kronotsky island arc was moving with the continental plate in Late Cretaceous time and with the Pacific plate from the beginning of the Paleocene until docking with the Eurasian margin in Miocene‐Pliocene time.