Kema Fm

Kema zone of Eastern Sikhote-Alin Basin

Based on lithological composition it is subdivided into three members (Malinovsky et al., 2002). Lower member consists of gravelstones, conglomerates, sandstones and mixtites with a total thickness of more than 1500 m. Middle member conformably overlies the lower member and consists of basalts, pyroclastic and sedimentary rocks and their alternation, mixtites and underwater landslide deposits with a total thickness of 440 m. Upper member conformably rests on the middle member. It is composed of rhythmically alternated sandstones and siltstones and beds of sandstones, siltstones and underwater landslide deposits with a total thickness of up to 1700 m.

Lower member is characterized by bivalves Dosiniopsis sp. ind., Aucellina caucasica and A. aptiensis suggesting an Aptian range. Moreover, a spore-pollen assemblage is reported from the siltstones of the upper part of the unit (Malinovsky et al., 2002). It is characterized by domination of spores and contains Gleicheniidites laetus, G. carinatus, G. senonicus, G. dicarpoides, G. circinidites, Plicifera delicata, Cyathidites minor, C. australis, Cicatricosisporites tarsus, C. dorogensis, C. multicostatus, Appendicisporites tricostatus, A. imperfectus, A. macrorhyzus, Concavissimisporites asper, Trilobosporites mirabilis, Taxodiaceaepollenites spp., Alisporites similis, A. aequalis, A. sp., Pityosporites aliformis, Pinuspollenites minimus, Rugubivesiculites aralicus, Araucariacidites sp., Ginkgocycadophytus spp., Classopolis sp. (determination of V.S. Markevich). This spore-pollen assemblage is similar to the Aptian assemblage from the Partizansk coal basin and to the Rioseki Flora of Japan (Malinovsky et al., 2002). Thus, the member is Aptian.

The range of the Middle member is determined based on its position in the section as upper Aptian-lower Albian.

Upper member: Bivalves Aucellina caucasica, A. anthulai, Cuspidaria sp., Variamussium sp. and ammonites Puzosia sp. ind. and Tetragonites cf. timotheanus were reported from the middle part of the upper member suggesting an lower-middle Albian range (Markevich et al., 2000; Malinovsky et al., 2002). Also, a spore-pollen assemblage was reported from the upper part of the member (Malinovsky et al., 2002). The assemblage is characterized by domination of spores Cyathidites australis, C. minor and Leiotriletes spp. Pollen of gymnosperms Classopolis. Taxodiaceaepollenites hiatus, Inaperturopollenites dubius, Ginkgocycadophytus, Alisporites similis are also abundant in the assemblage. It also contains Podocarpus multesimus, P. sp., Araucariacidites australis, Gleicheniidites laetus, G. senonicus, Cicadotricosisporites dorogensis, C. multicostatus, C. minor, Appendicisporites variverrucatus, Concavissimisporites asper, C. apiverrucatus, Impardecispora imperfectus, Laevigatosporites ovatus, L. ovoideus, Stereisporites stereoides, St. antiquasporites, St. glabellus, Concavisporites junctus, Tripartina variabilis, Kuylisporites lunaris, Taurocusporites reduncus, Coptospora paradoxa, Klukisporites variegatus, Osmundacidites wellmanii, Dictyophyllum harrisii, Tricolpites spp. (determination of V.S. Markevich). This assemblage is similar to the upper Albian assemblage from the lower member of the Naiba Fm of Sakhalin Island and to the assemblage of the upper part of sedimentary unit of the submarine Yamato Rise in the Sea of Japan (Malinovsky et al., 2002). The similarity is underlined not only in taxonomical composition but also in domination of the pollen Classopolis.