MIS13-01

Japan Geoscience Union Meeting 2016

Lithology of Cambrian to Ordovician radiolarian chert in Kazakhstan with special reference
to trace fossils*Yoshitaka Kakuwa1, Olga I Nikitina2, Tatiana J Tolmacheva3
1.Gas Hydrate Laboratory, Organization for the Strategic Coordination of Research and Intellectual
Properties, Meiji University, 2.Sarpaev Institute of Geological Sciences, Almaty, Kazakhstan,
3.A.P. Karpinskii Russian Geological Research Institute, St. Petersburg, Russia
Introduction
Trace fossils have been examined in the upper Cambrian to upper Ordovician radiolarian bedded
cherts in Australia, Scotland and Newfoundland to clarify both the evolution of benthic animals andthe change in environment of pelagic realm (Kakuwa and John, 2001; 2010; Kakuwa, 2014a; Kakuwa,
2014b). The result is summarized that Darriwilian is the age when benthic animals colonized widelyon the pelagic deep ocean bottom. The other important and well-dated successions of radiolarian
bedded chert (ribbon radiolarite) in Kazakhstan are studied to verify the result.
Examined bedded chert belongs to the Burubaital Formation that exposed in the southwest of Lake
Balkhash, southern Kazakhstan. Age constraints of the examined two successions of bedded chert are
given by Tolmacheva et al. (2001; 2004; unpublished data) who studied conodont fossils in detail.
Outline of the examined successions
Locality 89101
Upper Cambrian and Lower Ordovician chert is measured as thick as 36 meters. The succession isdivided into three. The lower part consists of pale gray crystalline chert of upper Cambrian. The
middle part consists of red chert of Tremadocian, and the upper part consists of pale gray, red andblack cherts of Tremadocian to Floian. Radiolarians and sponge spicules are observed under the
microscope. Thin laminations consistently develop in the cherts of this locality.
Locality 9706
Lower to Middle Ordovician bedded chert continuously exposed as thick as 70 meters. The lower halfof the section consists of pale to dark gray, black and red cherts. The upper half of thissuccession, Dapping and Darrwilian in age, consists of red chert with some intercalations of white
crystalline chert.
Characteristic knobby bedding planes that are considered as trace fossils by Tolmacheva et al.
(2001) develop in the middle to upper part of the section. Several beds and laminations ofsandstone and oligomicitic conglomerate (breccia) occur in the same horizon. The grains ofsandstone and conglomerate are composed of angular to subrounded chert, and are cemented by
microcrystalline quartz. Sponge spicules are closely associated with the clastic rocks.
Trace fossils
No convincing trace fossils are found in the Upper Cambrian to Tremadocian chert of the locality
89101, while trace fossils are found in the Darriwilian red chert of the locality 9706. Trace
fossils found are horizontal tunnel on bedding planes. They are as long as 10 cm and a few
millimeters in diameter. Some tunnels are bifurcated and some are sinuous. Curious tubes aredensely crowded in cherts of some limited horizons. They run oblique, parallel and vertical to thebedding plane. The tubes are 3 to 8 mm in diameter and as long as 2 cm in compacted length. The
tubes are filled with chalcedonic quartz. Various relieves on the knobby bedding planes include
probable trace fossils and diagenetic deformations.
Implications of trace fossils
Trace fossils are found in the radiolarian bedded chert of Darriwilian in Kazakhstan. This result
is common to the other examined areas of Australia, Scotland and Newfoundland, but the trace©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

fossils found in Kazakhstan are different from those found in the aforementioned areas.
Acknowledgement
This study is financially supported by the Ministry of Education, Culture, Sports, Science andTechnology of Japan (No.24540496).
References
Kakuwa, Y., Web, J., 2001. SEPM Special Publication No. 88, 267-276.
Kakuwa, Y., Web, J., 2010. Australian Journal of Earth Sciences 57, 615-625.
Kakuwa, Y., 2014a. Annual Meeting of The Sedimentological Society of Japan (Tsukuba).
Kakuwa, Y., 2014b. Japanese Geosciences Union Meeting 2015 (Chiba).
Tolmacheva, T.J., Danelian, T., Popov, L.E., 2001. Geology 29, 755-758.
Tolmacheva, T.J., Holmer, L, Popov, L., Gogin, I., 2004. Geological Magazine 141, 699-715.
Keywords: trace fossils, Cambrian, Ordovician, radiolarian chert, Kazakhstan, evolution©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

The origin of plate tectonics , the origin of the deep sea floor , elucidation of thedriving force , with Multi- Impact Hypothesis*Akira Taneko1
1.SEED SCIENCE Lab.
From the fact that A Wegenr is in North and South America's and Africa coastal profile of thecontinent to match, and advocates the continental drift hypothesis,I was trying to prove thecontinuity of the paleontology and geology in the grounds.Now it has become plate tectonics in theempirical observations such as inversion and seabed tape recorder hypothesis of seafloor spreading
hypothesis and mantle convection hypothesis and of the Mid-Atlantic Ridge discoveries and transform
fault of discoveries and geomagnetism is almost dogma.However, the driving force of continental
drift, which failed to show is Wegener remains still a mystery even in plate tectonics. Wegener had
been pointed out, the origin of the formation origin and plate boundary of the deep sea floor,
which accounts for 70% (-5km), efforts to explore the origin of plate tectonics had beenforgotten.Arc-shaped archipelago and the basin of origin is also remains a mystery. The newparadigm can clarify this all unified manner has been desired.
It was mentioned in the "elucidation of the Earth and the moon of the missing link" from the earth
physics and solar system planets science by the multi-impact hypothesis by abduction.According toit, in addition to the origin of this plate tectonics, the origin of the formation and deep sea
Yosoko of the month, the origin of the origin or Mercury or Pluto of eccentricity or Jupiter large
red rice of the core, meteorites and even more was the origin and differentiation of the asteroid
belt also of origin is a proposal of a new paradigm that can be unified elucidated.Abduction is theidea that conclusion, according to some hypotheses about possible if you can explain the multipleof the current situation the correctness of the hypothesis is guaranteed.In the hypothesis that
there is a physical meaning, If it is correct ideas, dramatic progress can be obtained.
CERRA passed since the birth of the solar system up to about 40 billion years ago and track
deformed by Jupiter perturbations, when the tearing with tension of Jupiter and the sun, CERRA andthe earth had been differentiated coagulation.In this hypothesis that multiple mantle debris
collides almost the same orbit around briefly to Earth, it became a repeated species large
extinction of the rationale, and stripped of mantle and the sea of 5km depth by isostasy.When
Darwin raised happened to collision mantle defect by isostasy, plate the surrounding crust was
peeling is recessed concave, the boundary cracks to form an arcuate archipelago.Arc-shaped
archipelago and Tethys Java island, etc. at the time of the formation of the sea, which wascentered on the Pacific Ocean, trench arc connected to the outside of the arc-shaped archipelago
plate shows the dive under the arc-shaped archipelago.Plate boundary is due to the cracking of thetime in which a plurality of cross-sectional mantle lobe collides with the Earth.In this hypothesis, because the Earth is rotating on its axis , when the mantle was missing by the collision became
convex in isostasy , moment of inertia in the earth that became non-uniform ( unbalanced) , thedriving force for the moment of inertia to the minimum occurs .
Only one of the hypothesis, that can be described as evolution unified all of the mystery is theresult of the abduction.
Keywords: The origin of plate tectonics , The origin of the deep sea floor, Elucidation of thedriving force, Multi- Impact Hypothesis, Bimodal frequency of earth height, The moon
formed by collision of CERRA mantle Ruptured debrislobe©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

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Japan Geoscience Union Meeting 2016

Reconsideration of sedimentary place of the Triassic Muyinhe Formation in the
Changning–Menglian belt of Southwest China*Tsuyoshi Ito1, Xin Qian2, Qinglai Feng2
1.Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 2.China Universityof Geosciences, Wuhan
Siliceous rocks of the Triassic Muyinhe Formation in the Changning–Menglian belt in southwestern
Yunnan Province in Southwest China had been considered to be pelagic deposits. We observed them andanalyzed their geochemistry, and recosidered the sedimentary place.
The observation revealed that the siliceous rocks are characterized by inclusion of abundantradiolarian test (e.g., Triassocampe Dumitrica, Kozur, and Mostler, Pseudostylosphaera Kozur andMostler, Eptingium Dumitrica, and Paroertlispongus) and the lack of rhythmical bedding. The
geochemical results are as follows: the samples have high concentrations of SiO2; most of thesamples were plotted in the non-hydrothermal field on the Al–Fe–Mn diagram; most of the samples
were plotted in the continental margin field on the Fe2O3/TiO2–Al2O3/(Al2O3+Fe2O3) and (La/Ce)N–Al2O3/(Al2O3+Fe2O3) diagrams. In addition, the samples show a flat rare earth element pattern normalized
to North America shale composite.
These observational and geochemical results strongly suggest that the siliceous rocks are unlikely
to represent pelagic deposits, indicating that the extent of the pelagic ocean basins in the
Paleotethys during the Triassic is probably less than previously believed. These non-pelagic
deposits may represent the closure stage of the Paleotethys.
Keywords: Geochemistry, Triassic, siliceous rock, radiolaria, Paleotethys, Changning–Menglian belt

©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Micrometeorites from Triassic and Jurassic bedded cherts of the Mino and Chichibu belts,
Southwest Japan.
*Mitsutaka Miura1, Tetsuji Onoue1
1.Department of Earth and Environmental Sciences, Faculty of Science, Kumamoto University.
Micrometeorites, which are submillimeter-sized extraterrestrial particles that survive atmosphericentry, originate from dust-producing objects such as comets and asteroids. Ancient micrometeorites
found in sedimentary rocks are of key interest as a historical record of meteoroid populations inthe solar system. We report the recovery of well-preserved micrometeorites, older than 240 Ma, inradiolarian chert from the Chichibu Belt on Ajiro Island (Middle Triassic) and Mino Belt on Inuyama
area (Late Triassic to Early Jurassic). These study sections consist of rhythmic alternations ofchert and shale beds. Samples were mechanically crushed and passed through 1.0 mm mesh sieve until
less than 5 g of the fine fraction was collected. We also used a hydrofluoric acid dissolution
method for determining micrometeorite content of chert samples. However, no micrometeorites havebeen recognized using this method. Magnetic components were separated using the method for
liquid-suspended particles with a magnetic field strength of ~500 mT. Micrometeorites werehandpicked from the magnetic components. The collection of micrometeorites comprised 72 cosmic
spherules, which are particles that totally melted during atmospheric entry. Analysis of theaccretion rate for cosmic spherules reveals high accretion rates of small spherules in the Middle
Triassic (Anisian) and Early Jurassic (Hettangian). However, the possible link between theenhancements in the accretion rate of cosmic spherules and variations in the flux ofextraterrestrial matter to the Earth requires further scrutiny.
Keywords: micrometeorite, Middle Triassic, Early Jurassic, Chichibu Belt, Mino Belt, beded chert©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Marine osmium isotope record across the Middle-Upper Norian transition in the Upper
Triassic deep-sea deposits from the Mino Belt, Japan*Honami Sato1, Tatsuo Nozaki1, Tetsuji Onoue2, Jun-Ichi Kimura1, Qing Chang1, Yutaro Takaya3,
Yasuhiro Kato4, Katsuhiko Suzuki1
1.Japan Agency for Marine-Earth Science and Technology, 2.Kumamoto University, 3.Waseda University,
4.The University of Tokyo
Instead of a single mass extinction at the Triassic-Jurassic boundary, extinctions in major pelagicgroups, such as radiolarians and conodonts, occurred stepwise during the last 15 Myr of theTriassic. Although a marked diversity decline on such pelagic fauna began in the end of Middle
Norian, the cause of this extinction has been uncertain. In order to assess the Middle to the Late
Norian environmental changes in the Panthalassa Ocean, we examined secular changes in the marine
osmium isotope compositions (187Os/188Os) recorded in the Triassic bedded chert succession of the
Mino Belt, central Japan. The osmium isotope compositions of seawater reflect contributions of theriverine (187Os/188Os ≈1.4), hydrothermal, and extraterrestrial (187Os/188Os ≈0.12–0.13) inputs ofosmium to the global ocean. Given the distinctive 187Os/188Os compositions of these inputs and therelatively short residence time of Os in the ocean (several tens of thousand years), seawater 187Os/
188

Os compositions are highly sensitive to changes in these fluxes. The Os isotope compositions show

a gradual increase in 187Os/188Os during the Middle Norian. Two negative Os isotope excursions areobserved within a ~2 m stratigraphic interval located between the Middle and the Upper Norian. The
onset of the first negative Os excursion is roughly located at the base of the Epigondolellabidentata conodont zone in the late Middle Norian. The timing of this Os isotope excursion
coincides with both the abrupt increase in Os concentration and low Re/Os ratios, all of whichsuggest a significant input of extraterrestrial Os into the sediments. The Os isotope compositions
exhibit the second negative Os isotope excursion from the initial Os isotope composition of ~0.7 tounradiogenic values of ~0.4 in the early Late Norian. However, it is difficult to specify the cause
for the second negative excursion with the dataset acquired in this study. Additional research isneeded to clarify the cause for this record in the upper Norian.
Keywords: osmium isotope, chert, Upper Triassic, Mino Belt

©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Origin of the Lower Triassic deep-sea chert gap*Shun Muto1, Satoshi Takahashi1, Satoshi Yamakita2, Masayuki Ikeda3, Tetsuji Onoue4
1.Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo,
2.Department of Earth Sciences, Faculty of Education and Culture, University of Miyazaki,
3.Department of Earth Science, Shizuoka University, 4.Department of Earth and Environmental
Sciences, Kumamoto University
Carboniferous to Jurassic pelagic deep-sea sediments that accumulated in the pelagic Panthalassa
Ocean are mostly composed of bedded chert lithofacies (Matsuda and Isozaki, 1991). Among them, theLower Triassic interval is characterised by siliceous claystone dominant lithofacies instead of
bedded chert lithofacies (the deep-sea chert gap) (Ishiga and Yamakita, 1993; Isozaki, 1997). The
age of the deep-sea chert gap (ca. 252–247 Ma) corresponds to the time interval of ecosystem
recovery from the end-Permian mass extinction, the largest mass extinction event in the Phanerozoic(Chen and Benton, 2012). Therefore, the deep-sea chert gap may reflect anomalous environmental
conditions during the Early Triassic that possibly delayed the re-establishment of complex
ecosystems after the mass extinction. The deep-sea chert gap may either be a result of an increasein burial flux of fine clastic material, or a decline in burial flux of biogenic silica in the
Early Triassic pelagic Panthalassa. However, previous studies have not calculated burial fluxes offine clastic material and biogenic silica based on well-dated sedimentary sequences. In order to
identify the mechanism that led to the formation of the deep-sea chert gap, we estimated the burial
fluxes of clastic material and biogenic silica in deep-sea sedimentary sequences, which were newly
described in this study.
Detailed geological mapping and reconstruction of lithostratigraphy was carried out at Ogama in the
Kuzuu area, Tochigi Prefecture, and in the Tsukumi area, Oita Prefecture, and consequently, several
continuous sections were identified. Based on conodont biostratigraphy, the studied sections arecorrelated to the triangularis-collinsoni Zone, the homeri Zone, the timorensis Zone and thebulgarica Zone of Koike (1981), which corresponds to the Spathian (upper Olenekian; uppermost Lower
Triassic) to middle Anisian (lower Middle Triassic). Using the conodont biostratigraphic framework,
absolute ages of volcanic tuff beds in South China were projected onto the reconstructed
lithostratigraphic columns of the deep-sea sections. Consequently, the lower limit of the linear
sedimentation rate (LSR) was obtained for the Spathian and lowermost Anisian siliceous claystone
dominant lithofacies.
In addition, major element concentrations were measured for rock samples obtained from the studiedsections by X-ray fluorescence (XRF) analysis. The SiO2 and Al2O3 concentrations were were combinedwith measured rock density data and the lithostratigraphic data of the studied sections to
calculate the burial fluxes of clastic material and biogenic silica for the stratigraphic intervals
for which LSR was estimated. For the lowermost Anisian in Ogama, the minimum burial fluxes ofclastic material and biogenic silica are 1030 g/cm2·m.y. and 1040 g/cm2·m.y., respectively. For the
Spathian in the Tsukumi area, the minimum burial fluxes of clastic material and biogenic silica are
960 g/cm2·m.y. and 1130 g/cm2·m.y., respectively. The estimated minimum burial flux of clastic
material for the deep-sea chert gap greatly exceeds the burial flux calculated for the Anisianbedded chert lithofacies in the Tsukumi area (80 g/cm2·m.y.), calculated based on LSR by Soda etal. (2015). The estimated minimum burial flux of biogenic silica for the deep-sea chert gap is also
higher than that of Anisian bedded chert in the Tsukumi area (390 g/cm2·m.y.), calculated based on
LSR by Soda et al. (2015). These results indicate that, during the deposition of sediments in the
deep-sea chert gap, burial fluxes of clastic material and biogenic silica were both elevated, but©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

the increase is greater in the former. Hence, the deep-sea chert gap is a result of anomalously
high flux of clastic material to the pelagic realm, which diluted biogenic silica in deep-sea
sediments.
Keywords: Lower Triassic, deep-sea chert gap, conodont, clastic burial flux, biogenic silica burial
flux©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Phylogeny of Middle Jurassic Striatojaponocapsa and middle Cretaceous Turbocapsula, andpotential of reliable radiolarian zonation*Atsushi Matsuoka1, Xin Li2
1.Department of Geology, Faculty of Science, Niigata University, 2.Graduate School of Science andTechnology, Niigata University
The four-segmented Stichocapsa tegiminis Yao group gave rise to three-segmented Striatojaponocapsa

plicarum (Yao). The evolutionary first appearance biohorizon defines the base of theStriatojaponocapsa plicarum Zone of Bajocian-early Bathonian age. In turn, Striatojaponocapsa
plicarum (Yao) evolved into Striatojaponocapsa conexa (Matsuoka) through Striatojaponocapsa
synconexa O’Dogerty, Gorican and Dumitrica. The evolutionary first appearance biohorizon ofStriatojaponocapsa conexa defines the base of Striatojaponocapsa conexa Zone of late
Bathonian-early Callovian age. This is a well-known evolutionary lineage of Middle Jurassic
radiolarians and contributes to offer a reliable chronological framework. An evolutionary trend
similar to the Striatojaponocapsa lineage is recognized in middle Cretaceous radiolarians belonging
to the genus Turbocapsula. Four-segmented forms of Turbocapsula evolved into three-segmented
Turbocapsula figitiva O’Dogerty by reducing segment number. Turbocapsula figitiva gave rise to
Turbocapsula costata (Wu) by acquiring widely-spaced costae. This speciation is characterized bycladogenesis. The Turbocapsula lineage has a potential to produce a reliable radiolarian zonal
scheme for the middle Cretaceous (Barremian-Aptian).
Keywords: radiolaria, phylogeny, zonation©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Lithostratigraphy and radiolarian age of pelagic sediments in the Wadi Hilti area of the
Oman Ophiolite: age constraint for eruption of the V2 lava
*Toshiyuki Kurihara1, Kousuke Hara1, Yumi Agui1
1.Graduate School of Science and Technology, Niigata University
The Oman Ophiolite is the most complete preserved section of upper mantle to oceanic crustworldwide (e.g., Lippard et al., 1986). The ophiolite forms a huge thrust sheet that crops out fora length of 500 km and a width of approximately 80 km in the Oman Mountains. Ernewein et al. (1988)
summarized the subdivision of volcanic rocks and recognized that V1, which has a normal MORB
(N-MORB)-like signature, was erupted around a spreading ridge and that V2 formed by intra-oceanicarc volcanism. In addition, thick lava flows of V3, ascribed to intra-plate volcanism, were
emplaced onto pelagic sediments (Umino, 2012).
The V2 and V3 lavas are widely distributed in the Wadi Hilti area, about 25 km west of Sohar,
northern Oman Mountains. Recently, Kusano et al. (2014) reexamined the volcano-stratigraphy of theV2 lava in this area, consisting of lower LV2 (IAT) and upper UV2 (boninite) units, based on theirgeochemical composition and stratigraphic relationship. The eruption and emplacement mechanism of
the V3 lava were studied by Umino (2012). Metalliferous and pelagic sediments overlie the UV2 lava
and are covered by the V3 lava. Based on our field examination for several sections in the Wadi
Hilti area, the stratigraphy of the sediments on the UV2 lava consists of metalliferous sediments,
red mudstone and micritic limestone, in ascending order. We obtained Guttacapsa gutta and Thanarla

pulchra from red mudstone. According to O’Dogherty (1994), the co-occurrence of these species isrestricted to be middle to late Cenomanian. From red mudstone and micritic limestone,
Rhopalosyringium scissum and Hemicryptocapsa polyhedra were recovered, which can be assigned to a
Turonian age (O’Dogherty, 1994).
Very recently, high-precision U–Pb zircon datings were conducted by Rioux et al. (2012, 2013, 2014)
on gabbros, tonalites, and trondhjemites. According to them, the rocks fall into two groups interms of their structural positions, dates, and isotopic composition: the older group, dated at ca.
96.5–95.5 Ma, is attributed to ridge magmatism (V1 lave), whereas the younger group (ca. 95.5–95.0
Ma) is related to post-ridge magmatism (V2 lava). Hara and Kurihara (2015) reported the maximum ageof sediments on the V1 lava to middle–late Cenomanian. In the present study, the sediments on the
UV2 lava can be correlated with the middle to late Cenomanian. These findings reveal that theactivity from the V1 to UV2 lavas was terminated in late Cenomanian. In addition, these radiolarian
ages are consistent with the high-precision U–Pb zircon ages of crustal rocks formed by ridge andpost-ridge magmatisms. These age constraints imply that the change of tectonic setting progressed
rapidly in a short period of middle–late Cenomanian.
Keywords: Oman Ophiolite, radiolarians, Cretaceous, Cenomanian©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Radiolarian biostratigraphy of Late Cretaceous pelagic sediments in the Wadi Jizzi area of
the Oman Ophiolite*Kousuke Hara1, Toshiyuki Kurihara1
1.Graduate School of Science and Technology, Niigata University
The Cenomanian–Coniacian radiolarian biostratigraphy of pelagic sediments overlying basaltic
extrusive lavas of the Oman Ophiolite was studied in the Wadi Jizzi area, about 40 km west ofSohar, northern Oman Mountains. Pelagic and metalliferous sediments commonly occur on lavas and at
the boundaries between different volcanic units. The most thickly accumulated sediments, which rest
directly on the V1 lava formed by ridge magmatism, were named the Suhaylah Formation (Fleet andRobertson, 1980; Woodcock and Robertson, 1982). The Suhaylah Formation is overlain by the Zabyat
Formation (Woodcock and Robertson, 1982; Robertson and Woodcock, 1983). This formation consists ofophiolite debris, redeposited sandstone- to siltstone-sized volcaniclastic rocks, and pelagic
mudstone. From the occurrence patterns and stratigraphic ranges of radiolarians, the species
clearly make up three distinct assemblages. Based on the occurrences, we defined the following
three biostratigraphic zones (interval zones): Guttacapsa gutta zone (basal part of the Suhaylah
Formation; middle Cenomanian to latest Cenomanian), Rhopalosyringium scissum zone (main part of
the Suhaylah Formation; latest Cenomanian to Turonian), and Archaeospongoprunum bipartitum (Zabyat
Formation; Coniacian). In previous studies (e.g., Tippit et al., 1981), the Suhaylah Formation was
dated as early Cenomanian to Coniacian–Santonian. We revised the age of this formation to
middle–late Cenomanian to Turonian. The radiolarian age of the sediments overlying the V1 lava (ca.
96 Ma) is consistent with the high-precision U–Pb zircon age of crustal rocks formed by ridgemagmatism (96.0-95.5 Ma) (Rioux et al., 2014).
Keywords: Oman Ophiolite, radiolarians, biostratigraphy, Cretaceous©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Ecology and diversity of phaeodarians (unicellular zooplankton) around Japan*Yasuhide Nakamura1, Rei Somiya2, Akihiro Tuji3, Noritoshi Suzuki4, Rie Hori, S.5
1.Hokkaido Univ., 2.Nagasaki Univ., 3.NMNS, 4.Tohoku Univ., 5.Ehime Univ.
Phaeodarians are a group of unicellular zooplankton dwelling in pelagic ocean from the at least
Triassic to the present. Phaeodaria have long treated as members of “Radiolaria”, however molecularstudies revealed that the group in question belongs to Cercozoa. Phaeodarians occasionally become
abundant in ocean, and they are thought to have important roles in the marine food web and thematerial cycles. We will present the results of our investigations concerning this group during thelast five years and discuss about the importance of phaeodarians.
Plankton were sampled from several depths at ca. 40 stations around Japan during 2011–2015. The
zooplankton in the samples were sorted and identified under a stereomicroscope in order to clarify
the composition of each sample. The 18S rDNA sequences of phaeodarians were determined bysingle-cell PCR method. Some phaeodarians caught in the East China Sea were cultured to observe
their behavior.
The microscopic and genetic analyses revealed that two undescribed phaeodarians live in the deep
waters in the Sea of Japan, and they were described as Aulographis japonica and Auloscena

pleuroclada. The former species was abundant through the year, occupying ca. 22% of the total
zooplankton biomass on average. The abundance of phaeodarians was also seen in the Kuroshio region,
where two species, Aulosphaeridae sp. 1 and Sagosphaeridae sp. 1, occupying 10.2–13.9% of thezooplankton biomass. Another unicellular zooplankton, Thalassothamnus sp. 1, was also found in
this region. This genus is classified as Entactinaria (Radiolaria) in the current classification
system. Our molecular and morphological analyses, however, revealed that the present species is amember of Phaeodaria. Thus, phaeodarians can occasionally become abundant around Japan, but theirinformation is still limited. Further research on unicellular zooplankton near the JapaneseArchipelago is necessary for considering the evolution of unicellular organisms in the pelagic
ocean.
Keywords: Cercozoa, Phaeodaria, plankton, present, protist, silica©2016. Japan Geoscience Union. All Right Reserved.

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Japan Geoscience Union Meeting 2016

Parameter identification of mathematical models based on three dimensional information ofplanktic foraminiferal shell structure obtained by Microfocus X-ray CT*Naoko Kishimoto1, Katsunori Kimoto2
1.Setsunan University, 2.Japan Agency for Marine-Earth Science and Technology
Morphological variations in microfossils like foraminifers and radiolarians might have the meaningof various functions for their evolution and adaptation in the geological history. In order toquantitatively understand such morphological variations, it is important to parameterize themorphological features in microfossils. We obtained precise morphology of a modern planktic
foraminifera Globigerinoides ruber (d’Orbigny) using Micro-Xray Computed Tomography (Micro-XCT)
technique, and developed numerical approximate models to validate the parameterization byexperimental rules used the sequentially connected spheres. Our approximate spherical modelclarified that several parameters including radius ratio, distances of geometric centers in eachchambers are almost constant, and others such as revolving angle between adjacent chambers aregradually transformed associated with growth of G. ruber, It indicates that previous numericalmodel could not interpret whole morphology of this species. The coupling of mathematical model andMicro-XCT technique has the great potential to realize various forms of microfossils and understandits functional morphology.
Keywords: Microfocus X-ray CT, Mathematical Model, functional morphology, Planktic foraminifera©2016. Japan Geoscience Union. All Right Reserved.

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