radiolaria - Marum

Bibliography - 1990 Radiolaria 14
Species constituents, relative species contributions, and seasonal
flux patterns of diatoms and other siliceous plankton are very much
alike at the two sites. The level of similarity between the two sites is
as close as that between two different depths at Station Papa,
suggesting tightness of covariance between the two sites. It is
possible to conclude that the oceanic flux province of the two sites
is nearly the same and that the processes responsible for such
similar export productions must be similar. Although quality of the
fluxes is similar, the flux levels are not exactly the same at the two
sites. Overall diatom export production at Station Papa was about
twice that at Station C. Flux levels of Radiolaria and silicoflagellates
were also higher at Station Papa than at Station C. Seasonal flux
maxima at Station C were generally delayed by 2 1 weeks over those
at Station Papa. The lower flux levels and delayed flux peaks at
Station C are correlated with density structure of upper water
masses.
Takami, M., Isozaki, Y., Nishimura, Y. & Itaya,
T. 1990. Geochronology of weakly metamorphosed Jurassic
accretionary complex (the Kuga Group) in eastern Yamaguchi
Prefecture, Southwest Japan. J. geol. Soc. Japan, 96, 669-
681.
Weakly metamorphosed Jurassic accretionary complex called
the Kuga Group in eastern Yamaguchi Prefecture is composed mainly
of olistostromal complex with matrices of mudstone and with
allochthonous blocks of chert, sandstone, siliceous mudstone, black
mudstone and greenstones. The northern part of this group
(Northern Unit) is separated from the southern part (Southern Unit)
by a north-dipping fault and is characterized by phyllitic nature of
the rocks. Microfossil researches clarified that the
Northern Unit contains Late Carboniferous to Late Triassic chert,
Early Triassic and Late Triassic to Early Jurassic siliceous mudstone,
and Early Jurassic black mudstone. Reconstructed primary
stratigraphy of these rocks is identical to that of modern trench
sediments. Although the age of matrices of mudstone has not been
fixed, it is considered that the Northern Unit formed as an
accretionary complex probably at early Middle Jurassic subduction
zone. The rocks in the Northern Unit have undergone a high pressure
type metamorphism of the pumpellyite-actinolite facies. K-Ar ages
of recrystallized white micas from 18 phyllitic pelites in the
Northern Unit concentrate in the range of 170-150 Ma (middle
Middle to early Late Jurassic).
Above-mentioned facts indicate that the Northern Unit of the
Jurassic complex formed as an accretionary complex in early Middle
Jurassic time and successively underwent a high pressure type
metamorphism at the depth of subduction zone in middle Middle to
early Late Jurassic time
Takemura, A. 1990. Paleogene radiolarian biostratigraphy
in the Antartic Ocean regions. Kaiyo Monthly, 22, 263-270.
(in Japanese)
Tan, Z.Y. & Chen, M.H. 1990. Some revisions of
Pylonidae. Chinese J. Oceanol. Limnol., 8/2, 109-127.
The three faces of the Pylonid are similar to one another but
actually have obvious differences. Their similarities and obvious
differences in dorsal. Iateral, and apical views are the criteria for the
author in species identification and redefinition of the Subfamilies
Diplozonaria and Triplozonaria (6 species in all) and description of 7
new species.
Tipper, H.W. & Carter, E.S. 1990. Evidence for
defining the Triassic-Jurassic boundary at Kennecott Point,
Queen Charlotte Islands, British Columbia. Geol. Surv.
Canada, curr. res., Pap., 90-1F, 37-41.
At Kennecott Point in Queen Charlotte Islands, a minor
discordance within sediments of the Sandilands Formation, Kunga
Group is proposed as the Triassic-Jurassic boundary. Ammonites and
radiolarians above the unconformity strongly indicate that the beds
are earliest Hettangian in age; ammonites, conodonts, and
radiolarians below the unconformity indicate that these beds are
probably latest Triassic in age.
Tominaga, R. 1990a. Jurassic accretionary prism of the
northern part of the Chichibu Belt, eastern Shikoku. J. geol.
Soc. Japan, 96/7, 505-522. (in Japanese)
Geology of the Sawadani area, Eastern Shikoku, is described.
And the province underlain by the Jurassic strata in the northern
part of Chichibu Belt is redefined as an independent terrane based on
the investigation in the Sawadani area. The Jurassic strata
distributed in the Sawadani area are divided into three units, the
Kenzan unit, the Higashiura unit and the Sawadani unit in ascending
order. All boundaries of the units are thrust faults which dipped
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south and were formed before the deposition of the Lower
Cretaceous series over the Chichibu Belt.
The Sawadani unit, which consists mainly of olistostromes with
pelitic or psammitic matrices, is characterized by the occurrence of
large amounts of greenstones, limestone and stratified serpentinite
bodies associated with crystalline schists as olistoliths. The
Higashiura unit is composed mainly of alternation of olistostromes
with pelitic and psammitic matrices, and characteristically contains
thick chert olistoliths associated with dolomite. The Kenzan unit also
consists chiefly of olistostromes with pelitic matrices and abundant
chert olistoliths, and contains intercalated acid tuff. Judging from
radiolarian fossils obtained from the Sawadani area, the Sawadani,
Higashiura, and Kenzan units are dated as early to middle Early
Jurassic, middle to late Early Jurassic, and Middle Jurassic age,
respectively. In the Sawadani area, these units show the following
four regularities regarding the ages of the constituent rocks: (1)
Whithin each unit, sedimentation took place in the order of limestone
⇒ chert ⇒ siliceous mudstone ⇒ mudstone. (2) Whithin each unit,
there tends to be periods of overlapping sedimentation between
limestone and chert, chert and siliceous mudstone, and siliceous
mudstone and mudstone. (3) Of the same rock species, those in the
lower unit are younger than those in the upper unit. (4) The rocks of
the same kind in different units tend to have the overlapping periods
of sedimentation. It is common among the accretionary prisms of
other belts that constituent rocks have such regularities and that
the unit boundaries are imbricated thrust faults. The model, which
explains the regularity regarding the ages of the constituent rocks
of the three units in the Sawadani area, illustrates the process of
accumulation of the accretioary materials.
Judging from the age polarity among the units, and from the
content of the terigenous materials in each unit, the Sawadani unit,
the Higashiura unit and the Kenzan unit are inferred to have
accreted along the northern front of the land consisting mainly of
the Kurosegawa rocks, during Early and Middle Jurassic time.
Therefore, I propose to redefine the province, underlain by such
Jurassic strata, as a terrane and to call the "Sawadani Terrane".
Tominaga, R. 1990b. Tectonic development of the
Chichibu belt, southwest Japan. J. Sci. Hiroshima Univ., Ser.
C: Geol. Min., 9/2, 377-413.
Tectonic development of the Chichibu belt, Southwest Japan
was discussed in this paper. on the basis of analysis of
tectonostratigraphic units and tectonic development of individual
units of the Chichibu belt in Shikoku, clarifying following points.
The Chichibu belt in Shikoku consists of three terranes, the
Sawadani Terrane, the Kurosegawa Terrane and the Sambosan
Terrane. The Sawadani Terrane is composed of three
tectonostratigraphic units, which develop as nappes separated by
southward dipping thrusts and show the northward younging age
polarity. They in Eastern Shikoku correspond to the Sawadani unit of
early to middle Early Jurassic time, Higashiura unit of middle to late
Early Jurassic time and Kenzan unit of Middle Jurassic time in
descending order, respectively. The Ohnogahara and Kanogawa
nappes in Western Shikoku are correlated with the Sawadani and
Higashiura nappes respectively. The ages of the constituent rocks of
the nappes show following rules: (1) In each unit the age of the
constituent rocks arrange in the order of limestone, chert, siliceous
mudstone and mudstone from older to younger. (2) Each pair of
limestone and chert, chert and siliceous mudstone and siliceous
mudstone and mudstone of individual units tends to show the overlap
of age. (3) The rocks of a kind in the lower unit are younger in age
than those of the same kind in the upper unit. (4) The same sort of
rocks in the different units tend to show the overlap of age. The
Sawadani Terrane in Shikoku is defined as a belt occupied by Early to
early Middle Jurassic accretionary prism formed along the northern
(inner) front of the Kurosegawa Island-arc. The Kurosegawa Terrane
is defined as a realm converted through Jurassic diastrophism from
an older island-arc (Kurosegawa Island-arc), which consists of the
Siluro-Devonian basement complex of continental crust type, Permo-
Triassic continental shelf type sediments, Permo-Triassic
accretionary prism etc. The Sambosan Terrane of the Hiradani-
Shiraishi area, Eastern Shikoku, has been divided from north to south
into the Torinosu Group and the A, B1, B2 and C tectonostratigraphic
units. The A, B1, B2 and C units have lithological and chronological
sequences regarded as accretionary prisms which show a younging
age polarity from north to south. The Sambosan Terrane is defined as
a belt which is occupied by Middle Jurassic to Early Cretaceous
accretionary prism formed along the southern front of the
Kurosegawa Terrane.
Late Paleozoic to Mesozoic tectonic development of the
Chichibu belt, Southwest Japan, is divided into nine stages. The initial
structure of the Sawadani Terrane and the Sambosan Terrane were
built up during the stages from 2 to 4 and the stages 5 to 7,
respectively. And the diastrophism throughout the Chichibu belt had
a climax at the change of the accretionary site from the northern
(inner) side to the southern (outer) side across the Kurosegawa
Terrane.