radiolaria - Marum

Radiolaria 14 Bibliography - 1992
structural geology of the Chichibu and Sambagawa terranes in the
Kanto mountains. We already presented two papers relating the
stratigraphy and structural geology to the south of the Yasudo area
(Hisada and Kishida, 1988; Hisada 1989). In this paper, we will deal
with the stratigraphy of the Chichibu sedimentary complex in the
Yasudo area and discuss the structural implications.
Hisada, K.I., Ueno, H. & Igo, H. 1992. Geology of
the Upper Paleozoic and Mesozoic sedimentary complex of
the Mt Ryokami area in the Kanto Mountains, central Japan.
Sci. Rep. Inst. Geosci., Univ. Tsukuba, Sect. B: geol. Sci.,
13, 127-151.
The Upper Paleozoic and Mesozoic sedimentary complex
constituting the Chichibu terrane extensively crops out in the Mt.
Ryokami area of the Kanto Mountains. This complex comprises the
Nakatsugawa Group including four tectonostratigraphic units, such
as the Nogurizawa. Ryokami. Ogamata, and Ryokami-yama chert.
Early to Middle Jurassic radiolarians were recovered from shaly
matrix of these units except for the last unit.
The Nogurizawa unit is subdivided into five subunits, α to ε, and
composed mainly of chaotic rocks consisting of chert, greenstone,
and others with shaly matrix, which yielded the radiolarians of the
Parahsuum simplum Zone-Tricolocapsa conexa Zone. The Ryokami
unit consists mainly of chaotic rocks characterized by frequent
association of fusulinacean limestone blocks. The shaly matrix of
the Ryokami yielded the radiolarians assigned to the Tricolocapsa
plicarum Zone. The Ogamata unit is composed mainly of sandstone
intercalating thick chert blocks and subdivided into α and β subunits.
The shaly matrix of the Ogamata yielded the radiolarians. which are
correlative to the Tricolocapsa plicarum Zone to T. conexa Zone. The
Ryokami-yama chert units consists mainly of chert with frequent
intercalations of greenstone and thrust over other underlying units.
Thick chert of this unit yielded Permian radiolarians as well as
Triassic and Early Jurassic ones.
Sedimentological and structural geologic data suggest that the
Nogunzawa Group constitutes the Mesozoic accretionary wedge.
Namely, chaotic rocks assignable to melange may be produced in
various settings on or within as accretionary wedge.
Holdsworth, B.K. & Nell, A.R. 1992. Mesozoic
radiolarian faunas from the Antarctic Peninsula: age,
tectonics and palaeoceanographic significance. J. geol. Soc.
London, 149/6, 1003-1020.
New assemblages of Radiolaria, including some of the few
occurrences of high southern latitude Jurassic and Cretaceous
radiolarian faunas, show that several localities in the LeMay Group
of Alexander Island range in age from latest Jurassic earliest
Cretaceous to at least Albian. By demonstrating that sedimentation
and deformation in the LeMay Group was diachronous, younging
oceanwards to the northwest, these new age assessments support
the model of the LeMay Group as an accretionary complex. The
polarity of subduction beneath Alexander Island was not affected by
arc collisions from at least the Lower Jurassic to the Oligocene, and
such a long period of continuous accretion appears to be unusual.
Deposition of the LeMay Group spans the Kimmeridgian to Albian
sedimentation in the Fossil Bluff Group fore-arc basin, thus making
the earlier concept of the LeMay Group as pre-Jurassic 'basement'
untenable.
Allochthonous latest Jurassic-earliest Cretaceous radiolarian
assemblages with some supposed Tethyan affinities are present in
the LeMay Group. In contrast, an in situ latest Jurassic assemblage
from the Nordenskjöld Formation of the back-arc basin and a further
Jurassic assemblage from a probable trench-slope basin have
characteristics believed diagnostic of high latitudes. The
biogeographic affinities of radiolarians from cherts in the LeMay
Group accretionary complex suggest that both these cherts, and
associated basalts, are far-travelled slices of the Phoenix plate.
Rocks from the probable trench-slope basin, formerly assigned
to the younger Fossil Bluff Group fore-arc basin sequence, now
appear to be part of a new, previously unrecognized formation.
Hori, R. 1992. Radiolarian biostratigraphy at the
Triassic/Jurassic Period boundary in bedded cherts from the
Inuyama area, Central Japan. J. Geosci. Osaka City Univ.,
35, 53-65.
Vertical distributions of microfossils such as radiolarians and
conodonts across the Triassic-Jurassic (T/J) boundary were clarified
through the biostratigraphic study of two continuous sequences of
bedded cherts in the Inuyama area, central Japan. Three types of
taxons were recognized around the T/J boundary, 1) Upper Triassic
type such as Squinabolella, 2) Upper Triassic-Lower Jurassic type
such as Canoptum, and 3) Transition type (possibly earliest Jurassic
type) such as Parahsuum and Bipedis. The radiolarian fossils
- 81 -
changed gradually, not drastically, from Triassic type into Jurassic
ones during the interval (ca. 7 m.y.) from the extinction of
conodonts to the first appearance of a species of Bagotum.
Ishida, K., Hashimoto, H. & Kozai, T. 1992. Lithoand
bio-stratigraphy of the lower Cretaceous Hanoura
formation in East Shikoku. Part 1. Hiura and Tsukigatani
routes in Katsuuragawa area. J. Sci., Univ. Tokushima, 26, 1-
57. (in Japanese)
Ishida, K., Yamashita, M. & Ishiga, H. 1992. P/T
boundary in pelagic sediments in the Tanba Belt, southwest
Japan. Geol. Rep. Shimane Univ., 11, 39-57. (in Japanese)
Ishiga, H. 1992. Middle Paleozoic radiolarians of the
genus Ceratoikiscum from Japan. In: Centenary of Japanese
Micropaleontology. (Ishizaki, K. & Saiti, T., Eds.). Terra
Scientific Publishing Company, Tokyo. pp. 389-397.
Iwata, K., Akamatsu, M. & Hirama, M. 1992.
Radiolarian fossils from the pre-Tertiary chert in the Tonin-
Aniva Peninsula, Sakhalin Island. Mem. hist. Mus.
Hokkaido, 31, 11-16. (in Japanese)
Iwata, K. & Tajika, J. 1992. Early Paleogene
radiolarians from green and red mudstones in the Yubetsu
Group and reconsideration of the age of their sedimentation.
Rep. geol. Surv. Hokkaido, 63, 23-31.
Reexamination of the radiolarian fossils included in the red and
green mudstones of the Yubetsu Group in the northeast Hokkaido
was carried out. As the results, the red and green mudstones of the
Toyosato Formation and the red siliceous shales of the Asahino
Formation indicate early early Paleocene, and green mudstones of
the Asahino Formation indicate late early Paleocene.
Iwata, K., Watanabe, Y. & Tajika, J. 1992.
Radiolarian biostratigraphic study of the Hakobuchi Group in
the Nakatonbetsu area, north Hokkaido. Rep. geol. Surv.
Hokkaido, 63, 1-21.
Radiolarian biostratigraphic study of the Hakobuchi Group and
the Upper Yezo Group in the Nakatonbetsu area, north Hokkaido, was
carried out to establish radiolarian zones of the uppermost
Cretaceous System in northern Japan. We have provisionally
recognized the following two zones; Protoxiphotractus perplexus and
Chlathrocyclas hyronia zones. The former and the latter indicate
early to middle Campanian and middle Campanian to early
Maastrichtian, respectively.
Iwata, K., Yamada, G. & Hirama, M. 1992.
Radiolarian fossils from chert boulders occurred in the eastern
coast of the Urup Island, Kuril Arc. Mem. hist. Mus.
Hokkaido, 31, 17-24. (in Japanese)
Jones, G., De Wever, P. & Robertson, A.H.F.
1992. Significance of radiolarian age data to the Mesozoic
tectonic and sedimentary evolution of the northern Pindos
Mountains, Greece. Geol. Mag., 129/4, 385-400.
Radiolarians were extracted from siliceous sediments of the
northern Pindos Mountains. in an attempt to establish the chronology
of tectonic and stratigraphic events related to the evolution of the
Pindos ocean basin. Three separate phases of siliceous
sedimentation were identified: (i) (mid-) late Triassic; (ii) mid-late
Jurassic and (iii) mid-late Cretaceous. The first two phases are also
known from the Pindos and Sub-Pelagonian zones of southern and
central Greece, and elsewhere in the Dinarides and Hellenides.
However, the occurrence of Cretaceous radiolarites in the west
central Tethyan region is somewhat unusual. Field observations
suggest that from the mid-late Triassic through to the mid Jurassic,
radiolarites were deposited on volcanic basement, or were
interbedded with sediments associated with the late
rifting/spreading stages in the development of the Pindos ocean.
Radiolarites of mid-late Jurassic age are commonly interbedded with
clastic sediments of ophiolitic derivation. This coincides with a
phase of significant compression within the Hellenides, which caused
intra-oceanic deformation of the Pindos ophiolite. The ophiolite was
subsequently emplaced onto the margin of the Pelagonian
microcontinent in latest Jurassic time (Kimmeridgian-early
Tithonian), as evidenced by transgressive marine carbonates.
However, the Pindos basin survived in reduced form until the early
Tertiary, allowing radiolarites to accumulate again within Cretaceous
post-tectonic clastic sequences.