|North Pacific||AKSR-NASR||Anadyr-Koryak||Verkhoyansk-Chukotka||Okhotsk-Chukotka||N. Alaska||Yukon||Chignik|
|Phytostratigraphy||Images of fossils characteristic of the Type Taphoflora|
The Kaivayam Phase of Floral Evolution
Corresponding to this phase, distinguished by Herman (1988), are the Kaivayam taphofloras of northwestern Kamchatka (localities of the Konglomeratovyi and Valizhgen capes), the Yelistratov Peninsula, and the Poperechnaya and Tylpegyrgynai taphofloras from the eastern and western flanks of the Pekul'nei Ridge. The type taphoflora of the phase is that of the Konglomeratovyi Cape locality (Herman and Lebedev, 1991). In addition, the taphoflora of the Pel-El Formation in the areas surrounding the mouths of the Mameta and Esgichninvayam rivers seems to correspond to this phase or to a time spanning both the Kaivayam and Penzhina phases. However the Pel-El taphoflora is impoverished and its affinity with the floral phases of the AKSR is ambiguous.
The boundary between the Penzhina and Kaivayam phases is approximately at the level of the Turonian–Coniacian boundary based on a succession of taphofloras in continuous sections of the Valizhgen Formation, exposed in the Konglomeratovyi Cape and Yelistratov Peninsula areas (Herman and Lebedev, 1991). The beginning and end of the Kaivayam phase corresponds to the beginning and end of the Coniacian age; a duration of 3 m.y. However the phase could include the terminal Turonian and/or the earliest Santonian.
Plant taxa characteristic of the flora are listed in the panel to the right. Not less than half of the plant species is represented by angiosperms. Large-leaved platanoids remain dominant, especially the genus Paraprotophyllum, although species of the genus Ettingshausenia also occur but are relatively rare. Pseudoprotophyllum is, however, known in taphofloras of the Pekul'nei Ridge. The abundance of Menispermites and Celastrophyllum is notably less than before, being compensated by a higher content of entire-margined leaves of the genus Magnoliaephyllum. Abundant and diverse are plant remains of Trochodendroides (5–7 species), "Zizyphus" (four species), and Araliaephyllum (five species). Ferns dominated by Ruffordia and Arctopteris are generally not abundant. Cycadophytes (rare Nilssonia or occasional Ctenis) are known only in taphofloras of the Pekul'nei Ridge, and Ctenis sp. from the Poperechnaya taphoflora likely represent the youngest forms of the genus in Northeastern Asia. Ginkgo ex gr. adiantoides is the only taxon of ginkgoaleans. Sequoia and Cephalotaxopsis, the dominant genera of conifers, occur in association with Elatocladus, Metasequoia, Glyptostrobus, and Cupressinocladus.
The flora of the Kaivayam phase is comparable with that of the Penzhina owing to the prevalence of platanoids and the presence of species in common belonging to ferns, gymnosperms and angiosperms, although it is dominated by distinctive other genera and species. Metasequoia is a persistent component, and newcomers typical of the phase are Paraprotophyllum pseudopeltatum, Trochodendroides sachalinensis, and as yet infrequent representatives of genera Glyptostrobus, Ternstroemites, Celastrinites, Grewiopsis, Smilax (?), and Hollickia. Cycadophytes also occur.
The Valizhgen phase (stratoflora), in the sense of Samylina (1986, 1988), incorporates taphofloras of the Penzhina and Kaivayam phases and is obviously incorrect in terms of classification and nomenclature. Despite the limited time spans of both phases, their taphofloras have clear distinctive features that are traceable throughout the AKSR territory. Moreover, in uniting two phases into one, it would be more correct in terms of nomenclature to use one of two former names, but not to introduce the new one. This is particularly so because the name "Valizhgen" has already been given to a taphoflora that is assignable to the (Barykov) phase in floral evolution, recovered from the Valizhgen Cape (Herman and Lebedev, 1991).