A spatiotemporal analysis of the trace element ratios and the isotopic composition of Sr, Nd and Pb in Cenozoic post-accretionary volcanic rocks in the east of the Koryak Highlands (Northeastern Russia) has been carried out. The Early Paleogene volcanic complex is shown to be represented by moderately Ti-rich aluminous tholeiites with elevated contents of high field strength elements (HFSE) (except for Ta and Nb), which makes them similar to E-MORBs. Low (La/Yb)n and high Zr/Nb (25–35) ratios characterize one of the source components as depleted and similar to MORBs. At the same time, low ratios of Nb/Ta, Ce/Pb, Nb/La with a high ratio of K/Nb were determined in basalts, which indicates the presence of a subduction component in the source. Low Zr/Hf and (Dy/Yb)n ratios indicate melting of the garnet-free substratum. The second (Miocene) stage is represented by the subalkaline basalt flows and dacite extrusions and dikes forming a bimodal series. Basalts are characterized by low concentrations of large ion lithophile elements (LILE), enrichment in HFSE, and fractionated distribution of REE, with (La/Yb)n ratios varying from the values characteristic of E-MORBs to the values corresponding to intraplate tholeiites. The Nb/Ta, Ce/Pb, La/Ta, and Hf/Th ratios tend to exhibit compositions of intraplate tholeiites. The (Dy/Yb)n and (La/Yb)pm - Ybpm ratios indicate the formation of Miocene basalts during the selective melting of garnet peridotite with varying garnet contents in the source. Dikes of dacites, in comparison with effusive facies, differ in calc-alkaline differentiation trends and other absolute concentrations of a number of elements. Early Quaternary alkaline olivine basalts and basanites of the Navarin area are high in HFSE, LILE, and REE and are compositionally similar to intraplate volcanics of oceanic islands and continental rifts. Data points of these rocks plotted on discriminant diagrams are confined to the field of the garnet-rich intraplate source with low degrees of partial melting. The initial isotopic ratios of Sr, Nd, and Pb in the Cenozoic basaltoids characterize the deep sources of Cenozoic rocks in the eastern part of the Koryak Highlands as depleted. The similarity of isotope ratios in the basalts of the Miocene and Early Quaternary stages of volcanism suggests that the mantle region was isotopically homogenized as a result of local convection.

An Erratum to this paper has been published: https://doi.org/10.1134/S0031030121340013

A general characterization of the Late Cretaceous floras of the Zeya-Bureya Basin is provided based on floristic assemblages from Russia (Amur Region) and China (Heilongjiang Province). Four phases of floral evolution were revealed: the Turonian-Coniacian (the Sutara flora), the Santonian (the Yong’ancun and Middle Kundur floras), the Campanian (the Taipinglinchang and Late Kundur floras) and the late Maastrichtian (Bureya flora). This long paleofloral succession provides possibility for investigation of different trends in the evolution of the Late Cretaceous taxa, flora, and climate.

A new fern Birisia mandshurica, sp. nov. (Dicksoniaceae) from the lower–middle Albian Frentsevka Formation of southern Primorye, Far East of Russia is described. This species is characterized by short-creeping rhizomes with closely spaced stipes and bipinnate fronds with narrow linear pinnules. A reconstruction of B. mandshurica is proposed. It comes from the autochthonous locality of ferns and herbaceous angiosperms and was a part of pioneer open community, which occupied low flat plains between river channels. Revision of ferns, described as Acanthopteris gothanii Sze from China, shows, that these ferns belongs to Birisia alata (Prynada) Samylina. The name Acanthopteris Sze should be abandoned, due to absence of spore-bearing pinnules and poor preservation of sterile pinnules in type specimens. Based on Chinese and Russian material of good preservation, we provide emended diagnoses of the genus Birisia Samylina and its type species B. alata. Re-examination of various species of the genus Birisia revealed that this genus was widely distributed in the Cretaceous floras (from the Barremian to the Coniacian) of Eastern Siberia, New Siberian Islands, North-East and Far East of Russia, China, Japan, Alaska and Western Canada. B. alata is the most widespread species.

The Chingandzha flora comes from the volcanic-sedimentary deposits of the Chingandzha Formation (the Okhotsk-Chukotka volcanic belt, North-East of Russia). The main localities of the Chingandzha flora are situated in the Omsukchan district of the Magadan Region: on the Tap River (basin of the middle course of the Viliga River), on the Kananyga River, near the mouth of the Rond Creek, and in the middle reaches of the Chingandzha River (basin of the Tumany River). The Chingandzha flora includes 23 genera and 33 species. Two new species (Taxodium viligense Golovn. and Cupressinocladus shelikhovii Golovn.) are described, and two new combinations (Arctopteris ochotica (Samyl.) Golovn. and Dalembia kryshtofovichii (Samyl.) Golovn.) are created. The Chingandzha flora consists of liverworts, horsetails, ferns, seed ferns, ginkgoaleans, conifers, and angiosperms. The main genera are Arctop teris, Osmunda, Coniopteris, Cladophlebis, Ginkgo, Sagenoptepis, Sequoia, Taxodium, Metasequoia, Cupressinocladus, Protophyllocladus, Pseudoprotophyllum, Trochodendroides, Dalembia, Menispermites, Araliaephyllum, Quereuxia. The Chingandzha flora is distinct from other floras of the Okhotsk-Chukotka volcanic belt (OCVB) in predominance of flowering plants and in absence of the Early Cretaceous relicts such as Podozamites, Phoenicopsis and cycadophytes. According to its systematic composition and palaeoecological features, the Chingandzha flora is similar to the Coniacian Kaivayam and Tylpegyrgynay floras of the North-East of Russia, which were distributed at coastal lowlands east of the mountain ridges of the OCVB. Therefore, the age of the Chingandzha flora is determined as the Coniacian. This flora is assigned to the Kaivayam phase of the flora evolution and to the Anadyr Province of the Siberian-Canadian floristic realm. The Chingandzha flora is correlated with the Coniacian Aleeky flora from the Viliga-Tumany interfluve area and with other Coniacian floras of the OCVB: the Chaun flora of the Central Chukotka, the Kholchan flora of the Magadan Region and the Ul’ya flora of the Ul’ya Depression.

The genus Hausmannia disappeared at end of the Early Cretaceous in most regions of the Earth, but in the North-East of Russia this genus was abundant during all the Late Cretaceous and even persisted into the Paleocene. In the Late Cretaceous the genus Hausmannia was represented by three endemic species: H. bipartita Samylina and Shczepetov (early Albian-Santonian), H. dublicato-crenata Samylina (Santonian-early Campanian) and H. olaensis Golovneva and Grabovskiy, sp. nov. (Santonian-early Campanian). A leaf fragment from the Paleocene Rarytkin Formation was determined only as Hausmannia sp. A high abundance of Hausmannia in the North-East of Russia was probably related with relict types of plant communities, dominated by Sphenobaiera, Baiera and Phoenicopsis, which survived in the highlands of the Okhotsk-Chukotka volcanic belt and its surroundings. (C) 2018 Elsevier Ltd. All rights reserved.

In the result of the re-examination of type material of the genus Birisia from the Cretaceous deposits of Siberia and North-East of Russia, we include only three species in this genus: B. alata (Prynada) Samylina (early-middle Albian — Coniacian), B. onychioides (Vassilevskaja et Kara-Mursa) Samylina (Aptian), and B. acutata Samylina (early-middle Albian). Species B. ochotica and B. alata are united under the name B. alata. Species B. jelisejevii, B. samylinae and B. oerstedtii are excluded from the genus Birisia as mismatching to the generic diagnosis. Species of Birisia are distinguished each other in size and degree of dissection of pinnules, in shape, presence and number of lobes, as well as the number of branches of the lateral veins inside the lobes. The pinnules of the Birisia are characterized by the significant variability and have a slightly different structure depending on their location on the leaf blade. Therefore, for a more accurate species identification of Birisia, it is necessary to have the most complete leaves with branching of two or three orders and the fertile pinnules.

A revision of Sphenobaiera biloba Prynada from Northeastern Asia is based on restudy of the type material from the Zyryanka River Basin (Prynada’s collection), as well as additional specimens from the type locality (Samylina’s collection) and collections from the Ul’ya and Anadyr rivers. A new extended diagnosis of S. biloba based on the leaf morphology and epidermal structure is proposed. Geographic and stratigraphic distribution of this species in Northern Asia is discussed. S. bilobais known in the Aptian of Eastern Siberia (Lena River Basin) and from the early-middle Albian to Coniacian of northeastern Russia. In the Late Cretaceous this species was considered as relict and related with volcanogenic deposits of the Okhotsk-Chukotka volcanic belt.

Cercidiphyllaceae-like leaves and fruits from the Lower Cretaceous deposits of Northeastern Asia were restudied. In the result one species of Jenkinsella fruits and five species of Trochodendroides leaves were recognized, including Trochodendroides potomacensis (Ward) Bell, T. buorensis Golovneva, T. sittensis Golovneva, sp. nov., T. vachrameeviana (Iljinskaja) Golovneva, comb. nov., and T. denticulata (Budantsev et Kiritchkova) Golovneva, comb. nov. Two new combinations and one new species are published. These plants had very small leaves and probably were shrubs. Fruits of Nyssidium orientale Samylina from the Barremian-Aptian Starosuchan Formation (Primorye, Russia) have no follicular characters as Jenkinsella fruits. Their affinity, not only to Cercidiphyllum-like plants, but to angiosperms in general, is doubtful. Leaves and fruits of Cercidiphyllum sujfunense Krassilov from the lower-middle Albian Galenki Formation (Primorye) also can not be assigned to Cercidiphyllaceae. Leaves have pinnate, brochidodromous venation and are comparable with those of Asiatifolium elegans Sun, Guo et Zheng, which were recorded from the Frentsevka Formation of the Partizansk coal basin, Primorye, Russia, and from the Chengzihe Formation, Northeastern China. Thus, the first reliable records of the genus Trochodendroides appear in the early-middle Albian. The relationship of these leaves with Cercidiphyllaceae is confirmed by finds of associated fruits Jenkinsella filatovii and by significant diversity of Trochendroides in the Late Albian-Cenomanian. In the early-middle Albian the genus Trochendroides was a minor component of the conifer-dominated Mesophytic floras. These fossils reflect the early radiation of Cercidiphyllaceae and indicate that this family began to diversify more then 30 million years before the Tertiary. Investigation of the early-middle Albian Cercidiphyllaceae provides important new data for our understanding of the early evolution of eudicots.

The genus Trochodendroides, recognized by its ovate or elliptical leaves with palmate brochidodromous venation, is well represented in the late Albian-Maastrichtian floras of North-East of Russia. The study of recently collected materials and revision of previous data allow us to introduce one new species (T. montana P. Alekseev, sp. nov.) and to offer 6 new combinations (T. ochotica (Vachr. et Herman) Golovn. et Gnilovskaya, comb. nov., T. barykovensis (Moiseeva) Golovn., comb. nov., T. gigantea (Moiseeva) Golovn., comb. nov., T. terranea (Moiseeva et Herman) Golovn., comb. nov., T. campanica (Abramova) Golovn. et Yudova, comb. nov., T. crenata (Herman) Golovn., comb. nov.). The new names were proposed for two species (T. samyliniae P. Alekseev, nom. nov., T. magadanica Golovn., nom. nov.). The diagnoses of 10 species are emended. The species Trochodendroides pekulneensis Philipp. and Zizyphus anadyrensis Philipp. are joined under the name Trochodendroides pekulneensis Philipp. emend. Yudova. The species Zizyphus microphylla Philipp. and Trochodendroides armanensis Philipp. are joined under the name T. magadanica Golovn. The species Macclintockia ochotica Vachr. et Herman and Trochodendroides longifolia Golovn. are joined under the name Trochodendroides ochotica (Vachr. et Herman) Golovn. et Gnilovskaya. In the whole, 21 species are recognized in the Late Cretaceous floras of North-East of Russia. Their stratigraphic and geographic ranges were analized. The systematic and morphology diversity of Trochodendroides was comparatively low in the late Albian–Turonian and the findings of these leaves are rare. During the Coniacian this genus reached the highest systematic and morphologic diversity. In the Santonian the abundance of Trochodendroides leaves was decreasing. In this time the lanceolate or narrow-ovate leaf morphotypes were most usual. The abundance of Trochodendroides leaves was increased again in the Campanian and decreasing in the Maastrichtian. Between 21 species, 18 species were distributed only in North-East of Russia. Many species were recorded only in single floristic assemblage. Species T. deminii and T. sachalinensis were characterised by wide stratigraphic ranges (from the late Albian to the Maastrichtian and from the Coniacian to the Campanian consequently).

On the basis of new records and reexamination of described fossils a revision of morphology and systematics of fructifications, found in co-occurrence with Trochodendroides Berry leaves was undertaken. The general construction of racemose infructescences and fruits of all known specimens is practically identical. This similarity indicates that these plants were closely related with minor differences that are not sufficient for separate generic designation. We suggest applying the name Jenkinsella Reid et Chandler for dispersed follicular fruits, to fruits in racemes and to infructescences attached to the shoots. This is the earliest appropriate generic name designated for fruits with distinguishable morphology and critical details of inner structures. The diagnosis of the genus Jenkinsella is emended and five new species are described: Jenkinsella krassilovii Golovneva et P. Alekseev, sp. nov., J. knowltonii Golovneva et P. Alekseev, sp. nov., J. conferta P. Alekseev et Golovneva, sp. nov., J. makulbekovii Golovneva et P. Alekseev, sp. nov., J. vilyuensis Golovneva et P. Alekseev, sp. nov. Three new combinations (J. filatovii (Samylina) Golovneva et P. Alekseev, comb. nov., J. jiayinensis (G.P. Feng, C.S. Li, Zhilin, Y.F. Wang et Gabrielyan) Golovneva et P. Alekseev, comb. nov., J. gardnerii (Chandler) Golovneva et P. Alekseev, comb. nov.) are created. Investigation of infructescence arrangement in different species of Jenkinsella provides new data, allowing reinterpretation of fertile shoots construction in Joffrea speirsii.

The analysis of the distribution of plant remains in deposits of the Aigur and Toptan formations (Omsukchan district of the Magadan Region) showed that the main part of the species that were included in the Toptan stratoflora (Samylina, 1976), in fact come from the Aigur Formation. Floristic assemblages of the Aigur and Toptan formations are very similar in systematic composition. Increasing the diversity of flowering plants and reduction of typical Cretaceous taxa (cycadophytes and Ginkgoales was not indicated on the boundary between these formation. Thus, there is no evidence of significant changes in the floristic composition at this stratigraphic level and the existence of independent Toptanian stage in the evolution of the mid-Cretaceous flora of the North-East of Russia. Floristic assemblages from the Galimyi, Aigur and Toptan formations are proposed to be merged into a single Sugoi flora, which should be attributed to the Buor-Kemus stage of floral development (lower-middle Albian). The description of the lectostratotype of the Toptan Formation is first published and distribution of this formation is illustrated.

U-Pb SHRIMP-dating of zircons from flora-bearing volcanic rocks of the Amka Formation stratotype (Ul'ya depression, Okhotsk-Chukotka volcanic belt) yield weighted mean 206Pb/238U age of 85.5 ±2 Ma (Santonian to Coniacian stage). This isotope dating is consistent with inferred Coniacian age of Ul’ya flora from the Amka Formation.

New findings of the genus Dalembia from Late Cretaceous sediments are described: Dalembia sp. from lower part of the Sym Formation (Coniacian – Santonian) of Eastern Siberia; Dalembia sp. from upper part of the Timmerdyakch Formation (Turonian – Coniacian) of Western Siberia; D. vachrameevii E. Lebedev et Herman and the new species D. argentea Yudova et Golovneva from the Chingandzha Formation (Turonian – Coniacian) of Okchotsk-Chukotka volcanogenic belt (Northeastern Russia). The stratigraphic range of the genus Dalembia stretch from the late Albian to Campanian. The geographical area includes the territories of Alaska, northern China, Northeastern Russia, Western and Eastern Siberia. The highest quantity of occurrences associated with Nothern Pacific region.

In the result of investigation of new findings, the variability of leaf shape and epidermal characters of Ginkgo pilifera Samyl. were studied. Geographical and stratigraphic ranges of this species were analyzed on the base of new material and earlier published data. This species was described by Samylina (1967) from the upper part of the Timmerdyakh Formation exposed in the Lena-Vilyui depression in Eastern Siberia. After that many new occurrences of this species were reported. G. pilifera was widely distributed from late Albian to Maastrichtian in Asian part of the Siberian-Canadian paleogeographical region. The earliest occurrence was documented from the late Albian-lower Turonian deposits of the Krivorechenskaya Formation, Grebenka River basin, Northeastern Russia. Approximately in the same time (in the Cenomanian) remains of G. pilifera appeared in the lower part of the Timmerdyakh Formation in the Lena-Vilyui depression. In Western Siberia in the late Albian and Cenomanian other species of Ginkgo were found: G. sertensis N. Nosova et Golovn. and G. chlonoviae N. Nosova et Golovn. were described from the Kiya Formation and G. ragosinii N. Nosova et Golovn. and G. tjukansis Kiritch. were described from the Simonovo Formation. In the Turonian and Coniacian G. pilifera was discovered in the upper part of the Timmerdyakh Formation, in the Valizhgen Formation of Yelistratov peninsula in Penzhina Bay area, in volcanogenic deposits of the Kolyma River basin and in the Derevyannye Gory Formation of New Siberia Island. In the Santonian-Campanian this species was reported from the Arkagala Formation of the Kolyma River basin and from two localities in the Amur River basin: from upper part of the Kundur Formation in Russia and from the Taipinglinchang Formation in China. The last occurrence is the most southern finding of this species. In Maastrichtian G. pilifera penetrated in Western Siberia, that significantly increased its area in western direction. The most variable character in G. pilifera morphology is the leaf shape. Leaves change from entire to deep-dissected into several wide lobes with rounded or truncate apices. Dissected forms occured from late Albian to Coniacian and predominated in the Krivorechenskaya (late Albian-lower Turonian) and the Valizhgen (Turonian-Coniacian) Formations Northeastern Russia.During Santonian-Maastrichtian only entire forms were distributed. The variability of epidermal characters is insignificant. The most variable characters are degree of undulation of the anticlinal cell walls, degree of development of cuticular thickenings and number of stomata on adaxial epidermises and number of trichomes on of abaxial and adaxial epidermises. The specific diagnosis of this species was emended. Remains of G. pilifera occur in allochtonous taphocenosis together with other plants characteristic to riparian habitats. Probably, this species was confined to river valleys and was not connected with swamp environments.Paleoecological implication of great number of papillae and trichomes is steel unclear. Emended diagnosis. Leaves broadly fan-shaped, entire with undulate upper margin with several shallow incisions, or, more rarely, dissected into several wide lobes with rounded or truncate apices. Leaves amphistomatic. Anticlinal cell walls of adaxial epidermis sinuous with amplitude up to 2–3 μm; in costal zones sometimes slightly sinuous or straight. Periclinal walls with cuticular dome-shaped thickenings and rare trichomes. Number and development of cuticular thickenings vary in different areas of leaf lamina and in different leaves. Weak development of thickenings usually correlates with increased number of trichomes. Stomata at abaxial epidermis rare; the papillae of subsidiary cells do not cover the stoma completely. Anticlinal cell walls of abaxial epidermis slightly sinuous or straight. Periclinal walls usually with papillae (12-20 μm long), more rarely, smooth. Trichomes (up to 60–100 μm long) occur rather often. Big trichomes usually consist of 2-3 cells. Stomata at adaxial epidermis orientated irregularly, without formation of regular rows, surrounded by five to seven subsidiary cells. Each subsidiary cell bears a proximal papilla up to 15–25 μm long. These papillae completely cover the stoma.

The Arman flora from the volcanogenic-sedimentary beds of the Arman Formation is systematically studied using materials from the Arman River basin and the Nelkandya-Khasyn interfluve (Magadan oblast, Northeastern Russia). Seventy-three species of fossil plants belonging to 49 genera are described. They consist of liverworts, horsetails, ferns, seed ferns, cycadaleans, bennettitaleans, ginkgoaleans, czekanowskialeans, conifers, gymnosperms of uncertain systematic affinity, and angiosperms. The Arman flora shows a unique combination, with relatively ancient Early Cretaceous ferns and gymnosperms occurring alongside younger Late Cretaceous plants, primarily angiosperms. The similarity of the Arman flora to the Penzhina and Kaivayam floras of northwestern Kamchatka and the Tylpegyrgynai flora of the Pekul’nei Ridge allows the Arman flora to be dated as Turonian and Coniacian (Late Cretaceous), which is corroborated by isotopic (U-Pb and 40Ar/39Ar) age determination for the plant-bearing layers.

The Ul’ya flora comes from the Coniacian volcanogenic deposits of the Amka Formation (the Ul'ya depression, southern part of the Okhotsk-Chukotka volcanogenic belt). Ginkgoaleans are diverse in this flora and represented by three genera: Ginkgo, Sphenobaiera and Baiera. All specimens have no cuticle and were assigned to morphotaxa. Genus Ginkgo includes two species: G. ex gr. adiantoides (Ung.) Heer with entire leaves and G. ex gr. sibirica Heer with dissected leaves. Genus Sphenobaiera also consists of two species: S. ex gr. longifolia (Pom.) Florin with 4–8 leaf lobes and S. ex gr. biloba Prynada with two leaf lobes. Genus Baiera is represented by new species B. lebedevii Golovn., sp. nov.Leaves of this species are 25–30 cm long and 13–16 cm wide, narrowly wedge-shaped with flat slender petiole, dichotomously dissected 4–5 times into linear segments 3–6 mm wide with 6–12 veins. The length of ultimate segments is equal to about a half of leaf length. Leaves attached spirally to ovoid short shoots about 2 cm long. Among the Late Cretaceous floras similar diversity of ginkgoaleans was recorded only in the Turonian-Coniacian Arman flora from middle part of the Okhotsk-Chukotka volcanogenic belt (Herman et al., 2016). Four species of ginkgoaleans from the Ul’ya flora (except G. ex gr. adiantoides) are considered as the Early Cretaceous relicts.

A revision of the angiosperm genus Menispermites from the Grebenka flora (the Krivorechenskaya Formation, late Albian-early Turonian) in Northeastern Russia based on our study of Kryshtofovich’s collection and our field observations allows us to recognize four species: M. minutus (Kryshtofovich) Shczepetov, Herman et Belaya, M. vasetskii Philippova, M. marcovoensis Philippova and M. orientalis Golovneva, sp. nov. A new extended diagnosis of M. minutus is proposed. Geographic and stratigraphic distributions of these species in Northern Asia are discussed. The use of the M. septentrionalis Hollick name for leaf fossils in Northern Asia is not recommended.