Postcollision exhumation of Northern Kamchatka complexes (Lesnovskii uplift)

The Eocene collision of the Cretaceous Achai� vayam–Valagin ensimatic island arc with the north� eastern margin of the Asian continent was an impor� tant event in the tectonic history of development of the northwestern framework of the Pacific. The collision was diachronic: collision of the southern part of the island arc with the continental margin occurred in the Early Eocene (55–53 Ma); collision of the northern part of the island arc with the continental margin was com� pleted by the Middle Eocene (about 45 Ma ago) [1, 2]. The age of the collision and the lateral variability of collision structures has been studied well [2]. The col� lision zone in North Kamchatka (an area of the Kam� chatka Isthmus) is one of the most thoroughly studied areas in Kamchatka (Fig. 1). In this area, the boundary between the Lesnovskii–Ukelayat and Achaivayam– Valagin terrains is represented by the Lesnovskii– Vatynskii thrust fault, formation of which was com� pleted about 45 Ma ago [3]. In order to reconstruct the postcollision geological history of the region, the fis� sion track dating method was first applied. This method allowed us to estimate the exhumation rate of complexes of the Lesnovskii uplift. Thus, the rates of the Post–Middle Eocene Orogeny in Northern Kam� chatka were calculated for the first time.