Vityaz Ridge Research Articles

Miocene radiolarian assemblages from the submarine Vityaz Ridge, Northwest Pacific: Biostratigraphy and paleoceanography

This study presents the first data on radiolarian fauna from Miocene deposits of the submarine Vityaz Ridge (SVR) and paraxial zone of the Kuril-Kamchatka Trench. Twenty-two dredge samples were studied, and 214 radiolarian taxa were identified. Taxonomic composition allowed their assignment to Miocene assemblage zones, including Lipmanella japonica conica-Gondwanaria dogieli, Pentactinosphaera hokurikuensis, Dendrospyris sakaii, Eucyrtidium inflatum Subzone a, Lychnocanoma magnacornuta, and Lychnocanoma parallelipes zones. These radiolarian assemblages correlate with studied sequences of many deep-sea cores in the northern Pacific and some sections of onshore Japan. As a result, we designed a biostratigraphic scheme of Miocene radiolarians for the SVR and reconstructed the environmental conditions in this area. In particular, two Miocene climatic optima that were previously established in the northern Pacific were identified in the Middle and Upper Miocene sediments of the southern plateau and Middle Miocene sediments of the northern plateau of the SVR.

New Isotope-Geochemical Data on the Cenozoic Volcanism and the Geodynamics of the Underwater Vityaz Ridge (Pacific Slope of the Kuril Island Arc)

New Isotope-Geochemical Data on the Cenozoic Volcanism and the Geodynamics of the Underwater Vityaz Ridge (Pacific Slope of the Kuril Island Arc)

НОВЫЕ ИЗОТОПНО-ГЕОХИМИЧЕСКИЕ ДАННЫЕ ПО КАЙНОЗОЙСКОМУ ВУЛКАНИЗМУ И ГЕОДИНАМИКЕ ПОДВОДНОГО ХРЕБТА ВИТЯЗЯ (ТИХООКЕАНСКИЙ СКЛОН КУРИЛЬСКОЙ ОСТРОВНОЙ ДУГИ)

Original analytical data on rare elements and radiogenic Nd and Pb isotopes in volcanic rocks of the Southern and southwestern part of the Northern Plateau of the underwater Vityaz Ridge are presented. Interpretation of these data and a comparative analysis with published materials on volcanic rocks from the southern and northern parts of the Kuril Island Arc (KOD), which formed on two basement blocks of different genetic nature, allow us to draw the following conclusions. The tholeiite varieties of volcanic rocks of the Southern Plateau and the southern part of the KOD have similar isotope-geochemical features, which point at the general geodynamic conditions of formation and the identical degree of influence of low-temperature fluid on magma-generating processes. The geochemistry of the volcanic rocks of the Northern Plateau, which are mainly represented by subalkaline varieties, indicates a more pronounced participation of the mantle component in magmagenesis and a greater degree of influence of high-temperature melt compared to the rocks of the Southern Plateau, but less compared to the rocks of the northern part of the arc. The volcanics of both plateaus are derivatives of a single mantle source, the MORB of the Indian Ocean (Indian MORB), and were formed together with the rocks of the southern part of the KOD within the lithospheric block transformed by tectonomagmatic processes that accompanied the opening of the Kuril Basin.

Seasonal variability of characteristics of nonlinear internal waves in the Kuril-Kamchatka region by Sentinel 1 data

The seasonal variability of the surface manifestations of nonlinear internal waves (NIW’s) in the Kuril-Kamchatka region from December 2018 to November 2019 was investigated based on the analysis of the Sentinel 1 satellite imagery archive. On 827 satellite images, 1876 manifestations of NIW’s were registered with a wavelength from 80 to 1900 m, containing from 2 to 18 waves in a packet. It was identified that the number of NIW’s registered in the water area varied significantly during the year. The minimum number of manifestations was recorded from January to March, and the maximum number of manifestations was observed from July to September. Areas of the frequent occurrence of NIW’s manifestations were identified: near the Kunashir Island, over the Vityaz ridge, near Cape Shipunsky and in Kamchatka Bay. Manifestations of NIW’s in these areas were recorded in all seasons of the year. These areas accounted for about 53% of all registered manifestations of NIW’s, and their area was about 20% of the study region area. The calculation of the tidal body force criterion for the main diurnal and semidiurnal tidal harmonics made it possible to identify potential generation sites of internal tidal waves. About 70% of NIW’s manifestations in August were detected in areas close to potential generation sites of diurnal internal tidal wave K1. This is explained by closeness of the generation and the disintegration sites of internal tidal waves under conditions of being beyond the critical latitude, where the tidal frequency coincides with the inertial one. Using the example of the area above the Vityaz ridge, the connection between the seasonal variability in the number of recorded manifestations and the annual variations in the tidal body force for harmonics K1, O1 and P1, mixed layer depth, the surface wind speed and the Brunt-Vaisala frequency was shown. This is consistent with the results of studies carried out in the adjacent regions of the Pacific Ocean. The existing archives of the Sentinel-1 radar image and the continuation of this satellite mission in the future will make it possible to estimate the long-term variability of NIW’s characteristic and to assess the impact of climate change on them.

Pleistocene radiolarian biostratigraphy of the submarine Vityaz Ridge, Northwest Pacific

This study presents new data on radiolarian fauna from the Pliocene–Quaternary sediments of the submarine Vityaz Ridge (SVR) and the paraxial zone of the Kuril– Kamchatka Trench (KKT): 60 taxa from 32 genera of Spumellaria, 50 taxa from 34 genera of Nassellaria, and 6 taxa from 2 genera of Collodaria were observed. An analysis of taxonomic compositional of the radiolarians revealed the Pleistocene radiolarian zone assemblages Cycladophora sphaeris, Eucyrtidium matuyamai, Stylatractus universus, and Lychnocanoma sakaii on the SVR and in the paraxial zone of the KKT. We also determined geographical distributions of these zones in the North Pacific. In addition, based on our and other previously published data, we inferred that two hiatuses occurred (during the Late Pliocene and the Middle–Late Pleistocene) in the study area. We established that the southern and northern plateaus of the SVR developed in different tectonic and sedimentation regimes at the end of the Early–beginning of the Middle Pleistocene.

On the Possibility of Age Correlation of the Geological Complexes in the area of the Kuril Island Arc System from Seismoacoustic Parameters

The results of P-wave velocity measurements in the basement and sedimentary cover rocks of the submarine Vityaz Ridge and surrounding morphostructures, used for age correlation of the geological complexes, are presented. The numerical values of the seismoacoustic parameter were obtained under laboratory conditions by direct measurements of the samples collected in the area of the Central Kuril Islands. In addition, the data derived from the seismic methods in the studied region in expeditions of previous years were used. The obtained results suggest that the sedimentary cover of the Kuril Basin is of the Paleocene or Eocene age, and the interarc basin is dated as the Paleocene.

New Radiolaria Species from the Cenozoic Deposits on the Island Slope of the Kuril–Kamchatka Trench

Descriptions of four new radiolarian species from the material collected from the Cenozoic deposits of the submarine Vityaz Ridge (the island slope of the Kuril–Kamchatka Trench) are provided in the article. The descriptions of the new species Amphistylus gladiusiacus sp. nov. and Thecosphaerella tochilinae sp. nov. from the Upper Eocene–Lower Oligocene deposits are based on the criteria established for the class of spherical porous Sphaerellaria: the number of skeletal shells, the shape of the cortical shell, and the development of the system of spines and axopodial complex. The new species Stylotrochus bipedius sp. nov. and S. tripedius sp. nov. from the Lower Pleistocene are considered among stauraxon radiolarians of the class Stauraxonaria due to the discoid geometric shape of their skeleton. The history of changes in the systematic position of the family Spongodiscidae is reviewed, and a proposal is made to restore the name of the order Discoidea Haeckel, 1862.

Structure, Matter Composition, and Deep Structure of the Oceanic Slope of the Central Kuril Islands: New Evidence

The results of reinterpretation of the geophysical data obtained during the study of the central sector of the Kuril Island Arc (2005–2010) are reported. The new boundaries of the shallow bedding of the basement and its block uplifts of varied composition are defined within the previously discovered zone of tectonic stretching and destruction of the Vityaz submarine ridge and interarc trough. Interblock depressions filled with sedimentary and volcanogenic-sedimentary rocks are distinguished. Areas represented by volcanoplutonic complexes including basic and sialic series (up to granite) are distinguished within the unbroken basement of the Vityaz Ridge. Intrusions and volcanic edifices composed of basic rocks are registered on the whole area studied. The relationship between the formation of the destruction zone and the geodynamic processes in the mantle is illustrated by the map of the Moho relief and structural-density model of the Earth’s crust.

Upper Oligocene-Lower Miocene diatom assemblages of the submarine Vityaz Ridge (Island slope of the Kuril-Kamchatka trench)

The diatom assemblages of the Upper Oligocene-Lower Miocene Rocella gelida (28.2-24.0 Ma, Thalassiosira praefraga (24.0-20.3 Ma), and Thalassiosira fraga (20.3-18.4 Ma) zones established in the sed� imentary section of the southern plateau in the submarine Vityaz Ridge of the Northwest Pacific include 123 species and intraspecific taxa belonging to 55 genera. The assemblages are correlated with their coeval analogs from sections of the Northwest Pacific. Taking into consideration the fact that Lower Oligocene dia� tom assemblages were previously documented in the Vityaz Ridge area, it is assumed that the sedimentary section with wellpreserved siliceous microfossils observ able in the southern plateau of the ridge corresponds to the continuous Oligocene-Lower Miocene interval.

Geochemistry of granitoids from the basement of the Kuril island arc system

This paper reports the characteristics of granitoids from the Pacific slope of the Kuril island arc system, which were discovered by the authors during geological and geophysical operations in three cruises of the R/V Akademik M. Lavrent’ev. The major and trace element compositions of these rocks were determined, their role in the formation of the submarine Vityaz Ridge was evaluated, and they were compared with granitoids from the Brouton group of submarine volcanoes and xenoliths from Simushir Island and the Sea of Okhotsk. Granitoids from various structures of the basement of the Kuril island arc system are hypabyssal rocks derived from andesite magmas. Their common features are related to the formation on the continental crust under convergent geodynamic conditions involving compression due to the movement and subduction of the Pacific plate beneath the Asian continent. The problem of the basement of the Kuril island arc system was discussed, the composition and age of its rocks were determined, and the history of the geologic development of the Pacific slope of the arc starting from the Late Mesozoic was briefly described.

Granitoids in the basement of the Kurile island arc system

The Kurile island arc system consists of three large structural elements: the frontal zone, the Greater Kurile Ridge, and the backrc zone adjacent to the latter on the side of the Sea of Okhotsk in the form of submarine volcanic ridges. The frontal zone includes the Pacific slope of the Kurile arc consisting of the underwater Vityaz Ridge and islands of the Lesser Kurile Ridge. It touches the Pacific Plate, and the sea bottom in this area hosts outcrops of the basement of the entire island system. The data on the composition and age of the basement are of importance for solving the problem of the origin of the island arc, since they allow the onset of its formation and evolution to be reconstructed. The evidence for interpreting the composition of the basement beneath the Greater Kurile Ridge was provided only by single finds of metamorphic and intrusive rocks occurring in the form of xenoliths in lavas of the Kurile Islands (1). Based on these findings, Sergeev (2) assumed the presence of the Hercynian or Mesozoic folded basement under this structure, while Vasil'ev (3) believes that the entire island block and Vityaz Ridge represent constituents of the folded domain formed at terminal stages of the Mesozoic orogeny.

Volcanism as an indicator of a depth mechanism for the formation of the Seas of Japan and Okhotsk

The results of the geochemical studies of the Late Oligocene-Pleistocene volcanic rocks that accompanied the formation of the deep-water basins of the Seas of Japan and Okhotsk are presented. These rocks have an initially mantle origin that is a derivative of a single source—spinel perodotites. They formed as a result of the partial melting of secondary plumes located in the head part of the major mantle plume. This plume rose very closely to the surface in the area of the Japanese (Central) basin, where the marginal-sea basaltoids with chemical properties of HIMU (OIB) sources were established. The continental lithosphere (the upper mantle and the crust) was involved in the magma formation in the area of the Kuril basin and the Vityaz Ridge at the earliest rifting stage in the Late Oligocene-Early Miocene and at the final stage in the Pliocene-Pleistocene.

Palynological characteristics of the sediments of the Malokuril’skaya formation (Maastrichtian-Danian), Shikotan Island

A spore-pollen assemblage was established for the first time in the sediments of the Malokuril’skaya Formation (Khromova Bay, Shikotan Island, Lesser Kuril Range, Kuril island arc system). This find enabled dating of the sediments of the uppermost part of the Malokuril’skaya Formation, which, based on this data, are referred to the Maastrichtian-Danian boundary. The assemblage of radiolarian species was identified for the entire section of the Malokuril’skaya Formation. In sediments of the lower part of the section, members of the Inoceramus group were described. These findings add new information to the paleontological characteristics of the Malokuril’skaya Formation. Moreover, our work allowed detailed correlation of the palynological assemblage studied with coeval palynological assemblages of adjacent areas. The similarity of Cretaceous-Paleogene sections of the Ust-Palanskaya (West Kamchatka), Uchir (Sakhalin Island) and Malokuril’skaya Formations, the Upper Cretaceous basement and the Cenozoic cover of the underwater Vityaz Ridge support the shared history of the development of the entire transition zone from the marginal Sea of Okhotsk to the Pacific at the Maastrichtian-Danian boundary.

Late Mesozoic and Cenozoic volcanosedimentary complexes from the submarine Vityaz Ridge, the Island Arc slope of the Kuril-Kamchatka trench, and its evolution

This work is a continuation of the geological studies and presents the results of the petrographic, Xray, diatom, and spore-pollen analyses of the rocks aimed at reconstructing the geological evolution of the sub� marine Vityaz Ridge area. Abstract—This paper describes the volcanosedimentary complexes of different ages (Late Cretaceous-Early Paleocene, Paleocene-Eocene (?), Oligocene-Early Miocene, and Pliocene-Pleistocene) that compose the basement and sedimentary cover of the submarine Vityaz Ridge. It was found that the Upper Cretaceous sedimentary rocks from the basement of the Vityaz Ridge (felsic) and the Lesser Kuril Ridge (mafic) have dif� ferent compositions. Matrix mineral assemblages corresponding to the smectite and corrensite stages of epi� genesis of Cenozoic rocks were distinguished, and a scheme of the Late Cretaceous-Pleistocene geological evolution of the region was proposed.

Geochemistry of the submarine Vityaz Ridge at the pacific slope of the Kurile island arc

This paper reports the results of geological studies at the submarine Vityaz Ridge carried out during cruises 37 and 41 on the R/V “Akademik Lavrent’ev” in 2005 and 2006. The studied area is located at the near-island trench of the slope in the central part of the Kurile island arc. Morphologically, it consists of two parts: inner volcanic arc represented by the Great Kurile Range and outer arc corresponding to the submarine Vityaz Ridge. Diverse rocks that compose the basement and sedimentary cover of the ridge were recovered by dredging. Based on K-Ar dating and geochemistry, the volcanics were divided into Paleocene, Eocene, late Oligocene, and Pliocene-Pleistocene complexes. Each of the distinguished complexes reflects the tectonomagmatic stage in the ridge evolution. The geochemical and isotope data on the volcanics indicate the contribution of ancient crustal material in magma source and, correspondingly, the formation of this structure on the continental basement. Two-stage model ages, TDM2, vary in a wide range from zero values in the mafic rocks to 0.77 Ga in felsic varieties, pointing to the presence of Precambrian protolith in the source of the felsic rocks of the Vityaz Ridge. The Pliocene-Pleistocene volcanics are classed with the tholeiitic, calc-alkaline, and subalkaline series, which differ in alkali contents and REE fractionation. The values of (La/Sm)N and (La/Yb)N ratios vary from 0.74 and 0,84 in the tholeiitic varieties to 1.19 and 1.44 in the calcalkaline and 2.32 and 3.73 in the subalkaline rocks. All three varieties occur within the same volcanic edifices and were formed during differentiation of magmatic melt that were channeled along fault zones from the mantle source slightly enriched in crustal component

Pliocene sediments of Shikotan Island (Lesser Kuril Ridge)

Shikotan Island of the Lesser Kuril Ridge forms, together with the Vityaz Ridge, the outer arc of the Kuril island-arc system. Marine Pliocene sediments first registered on the island contain diatoms and palynomorphs, which allow their dating. The thin Pliocene semiconsolidated sediments constitute the upper part of sections in the coastal and central areas of the island. They rest with the erosional surface and stratigraphic hiatus upon the Upper Cretaceous-Lower Paleogene (Campanian-Danian) Malokuril’sk Formation. The Pliocene sediments were deposited in relatively shallow-water environments of open sea near the shore, with a forest-free landscape and freshwater basins. The occurrence of reworked marine Oligocene and Miocene diatoms in these sedimentary rocks indicates their development in the Lesser Kuril Ridge area and contribution of their eroded material to the formation of Pliocene sequences. Wide development of Pliocene Marine sediments on Shikotan Island is evidence for ascending movements in the region during the post-Pliocene period, which is also characteristic of the Greater Kuril Ridge islands. The composition and formation conditions of the Pliocene sediments in the outer arc of the Kuril island-arc system suggest that the southwestern (Lesser Kuril Ridge) and northeastern (Vityaz Ridge) segments of this single anticlinal structure evolved under different tectonic regimes through the Pliocene.

Geology and volcanism of the underwater Vityaz Ridge (Pacific slope of the Kuril Island Arc)

This paper presents the results of geological studies carried out during the two marine expeditions of the R/V Akademik M.A. Lavrent’ev (cruises 37 and 41) in 2005 and 2006 at the underwater Vityaz Ridge. Dredging has yielded various rocks from the basement and sedimentary cover of the ridge within the limits of three polygons. On the basis of the radioisotope age determinations, petrochemical, and paleontological data, all the rocks have been subdivided into the following complexes: the volcanic ones include the Paleocene, Eocene, Late Oligocene, Middle Miocene, and Pliocene-Pleistocene; the volcanogenic-sedimentary ones include the Late Cretaceous-Early Paleocene, Paleogene undifferentiated, Oligocene-Early Miocene, and Pliocene-Pleistocene. The determination of the age and chemical composition of the rocks has enabled us to specify the formation conditions of the extracted complexes and to trace the geological evolution of the Vityaz Ridge. The presence of young Pliocene-Pleistocene volcanites allows one to come to a conclusion about the modern tectono-magmatic activity of the central part of the Pacific slope of the Kuril Islands.

Magmatism of the submarine Vityaz Ridge (Pacific slope of the Kuril Island Arc)

Original results of igneous rock studies are presented. The rocks were dredged during a marine expedition (cruise 37 of R/V Akademik M.A. Lavrent’ev in August–September, 2005) in the region of the submarine Vityaz Ridge and Kuril Arc outer slope. Several age complexes (Late Cretaceous, Eocene, Late Oligocene, Miocene, and Pliocene-Pleistocene) are recognizable on the Vityaz Ridge. These complexes are characterized by a number of common geochemical features since all of them represent the formations of island arc calc-alkali series. At the same time, they also have individual features reflecting different geodynamic settings. The outer slope of the Kuril Arc demonstrates submarine volcanism. The Pliocene-Pleistocene volcanic rocks dredged here are similar to the volcanites of the Kuril-Kamchatka Arc frontal zone.

Geological structure of the submarine Vityaz Ridge within the Seismic Gap area (Pacific slope of the Kurile island arc)

Results of geological research conducted by the Pacific Oceanological Institute of the Far East Division of the Russian Academy of Sciences and the Institute of Oceanology of the Russian Academy of Sciences on the submarine Vityaz Ridge during Cruise 37 of R/V Akademik M.A. Lavrentyev in 2005 are discussed. Various rocks constituting the basement and sedimentary cover of the ridge were dredged in three areas of the ridge. Based on isotope geochronology, petrogeochemical, petrographic, and paleontological data and comparison with similar rocks available from the adjacent land and Sea of Okhotsk, they are subdivided into several age complexes. Late Cretaceous, Eocene, Late Oligocene, Miocene, and Pliocene-Pleistocene complexes are defined among the igneous rocks, while volcanogenic-sedimentary rocks are united into Late Cretaceous-Early Paleocene (late Campanian-Danian), undivided Paleogene (Paleocene-Eocene?), Oligocene-early Miocene, and Pliocene-Pleistocene complexes. The obtained data on the age and formation settings of the defined complexes made it possible to reconstruct the geological evolution of the central Pacific slope of the Kurile island arc.