RUSSIA 469 Figure 10 Tectonics of the Verkhoyansk Chukotka Orogenic Collage (compiled by Yakubchuk and Nikishin) Note oroclinal structure of the collage Mid Cretaceous Okhotsk Chukotka Arc stitched the terranes that constitute the collage Terranes of the Koryak Highlands represent an accretionary wedge that formed in front of this arc evolved from the Early to Middle Palaeozoic until the Cretaceous In the north, it is bounded by the Hyperborean Craton To the south-west is the Siberian Craton The eastern boundary of the collage coincides with the Okhotsk-Chukotka Andean-type arc that stitched various terranes in the Late Cretaceous The Hyperborean Craton is a possible fragment of the North American Craton It was incorporated into the collage after spreading in the Canadian basin in the Late Jurassic to Early Cretaceous Plate tectonic reconstructions suggest that its arrival in the Early Cretaceous was the major reason for the amalgamation of the Verkhoyansk-Chukotka Collage This craton occurs almost completely in the shelf zone, and its small fragments are exposed in eastern Chukotka, Novaya Sibir, and the Wrangel Islands In the south, it is bounded by the deformed passive margin terrane of Chukotka and Arctic Alaska It consists of Triassic-Jurassic terrigenous rocks deformed in the Early Cretaceous In the south, the Chukotka Terrane is bounded by the South Anyui Suture, hosting Late Palaeozoic to possible Early Mesozoic ophiolites and accretionary wedges The Verkhoyansk passive margin is a mirror image of the Chukotka Terrane, but it includes Ordovician to Middle Jurassic turbidite sequences which are present in the imbricated structure thrust onto the Siberian Craton These assemblages extend along the north-east margin of the Siberian Craton and can also be traced along the western flanks of smaller cratonal terranes of Okhotsk, Omolon, and Prikolyma, forming the Kolyma Orocline The Verkhoyansk passive margin rocks are structurally superimposed by the Jurassic accretionary terranes Inside them, in the core of the Kolyma Orocline, are the Early Palaeozoic carbonate terranes