radiolaria - Marum

Bibliography - 1992 Radiolaria 14
Guex, J. 1992. Origine des sauts évolutifs chez les
ammonites. Bull. Soc. vaud. Sc. nat., 82/2, 117-144.
Ammonoid lineages frequently start with evolute
representatives which become more involute during their evolution.
From a geometrical point of view, this trend can be regarded as an
increase of the dimensionality of the shells. During periods of
ecological stress, this trend is often reversed. In extreme cases,
some end-forms can generate new groups which are globally
simplified and of atavistic aspect. Such atavistic groups are the
source of new evolutionary lineages. Temporal variations in the
morphological complexity of ammonites are compared with those
known in some other groups of invertebrates (i.e.:Radiolaria,
Foraminifera).
Gupta, S.M. & Srinivasan, M.S. 1992. Late Miocene
radiolarian biostratigraphy and paleoceanography of Sawai
Bay Formation, Neill Island, Andamans, India.
Micropaleontology, 38/3, 209-235.
Stichocorys peregrina Didymocyrtis penulrima and
Didymocyrtis antepenultima Late Miocene radiolarian zones are
encountered from mudstone strata of Sawai Bay Formation, Neill
Island, Andamans. Percentage data of forty-five coarser taxonomic
groups of radiolarians were subjected to Q-mode cluster analysis.
Cluster A comprises Stichocorys, Phormospyris, Eucyrtidium,
Lamprocyclas, Acrosphaera and Cycladophora groups. Cluster B was
divided into subclusters at 0.83 level of clustering. Subcluster B1
comprised Didymocyrtis-Diartus, Pyloniids, Collosphaera,
Phacodiscids, Pterocorythids, Pterocanium and Spongodiscids,
whereas subcluster B2 comprised Porodiscus, Euchitonids,
Stylodictya-Stylochlamydium, Spongopyle, Phormostichoartus,
Lophophaenids and Lithelius groups.
Based on the ecology of the modern homeomorphs of the
dominant radiolarian groups, it is suggested that cluster A and
cluster B indicate colder and warmer periods, respectively.
Subcluster Bl indicates surface-water fauna and subcluster B2
represents subsurface water fauna. Dominance of subcluster B2 in
Didymocyrtis antepenultima zone (8.5-7.2 Ma) suggests that
subsurface fauna was thriving more probably due to the monsoonal
upwelling during warmer periods. This finding is also substantiated
with diatom/radiolaria ratio. Presence and absence of deep (1200-
2000m) and intermediate (700-1200m) water dwelling radiolarians
like the Plectopyramids, Botryostrobus and Sethoperinids groups
indicate basinal shallowing during Late Miocene. It may be due to
subduction of the Indian plate below the Asian plate, coupled with
huge sediment discharged from the Irrawaddy River of Burma during
monsoon dominated warmer periods (5.0-6.3 and 8.5-7.7 Ma) in
Late Miocene.
Hada, S., Sato, E., Takeshima, H. & Kawakami,
A. 1992. Age of the covering strata in the Kurosegawa
Terrane: dismembered continental fragment in southwest
Japan. In: Significance and application of Radiolaria to
terrane analysis. (Aitchison, J.C. & Murchey, B.L., Eds.),
vol. 96/1-2. Special Issue: Palaeogeogr. Palaeoclimatol.
Palaeoecol., Elsevier, Amsterdam. pp. 59-70.
Along with the rapid development of radiolarian biostratigraphy,
introduction of the new concept of tectonostratigraphic terranes has
urged us to reexamine "geosynclinal complexes" which contain
various radiolarian-rich rocks such as fine-grained clastic, siliceous,
and tuffaceous rocks. Entirely new age data have been discovered
from these hitherto poorly known formations. However, until
recently, little attention has been paid to the age of geologic units
consisting mainly of orderly stratigraphic sequences and coarsegrained
clastic rocks such as the "Usuginu-type Conglomerate" in
the Kurosegawa terrane, which is characterized by the presence of
abundant clasts of granitic rocks. Accurate dating of conglomeratebearing
formations in the Kurosegawa terrane using radiolarian
fossils provides a basis for tectonic reconstructions of the
Kurosegawa terrane. These formations are fairly well-bedded
sequences of mudstone, sandstone and conglomerate, without any
exotic clasts of oceanic affinity. They range in age from mid-Permian
to Middle Jurassic. Integration of these results indicates that the
Kurosegawa terrane originated as a fragment of continental margin
characterized by the presence of crystalline basement and coherent
covering strata. However, the elements of the Kurosegawa terrane
were subsequently severely disrupted into a zone of melange.
Harms, T.A. & Murchey, B.L. 1992. Setting and
occurrence of Late Paleozoic radiolarians in the Sylvester
allochthon, part of the proto-Pacific ocean floor terrane in
the Canadian Cordillera. In: Significance and application of
Radiolaria to terrane analysis. (Aitchison, J.C. & Murchey,
B.L., Eds.), vol. 96/1-2. Special Issue: Palaeogeogr.
- 80 -
Palaeoclimatol. Palaeoecol., Elsevier, Amsterdam. pp. 127-
139.
Late Paleozoic radiolarians have been used to establish the
ages or age ranges of fourteen lithotectonic units in the Sylvester
allochthon of the Slide Mountain terrane in British Columbia, and
have thereby greatly clarified the geology and tectonic history of the
terrane. As the Sylvester radiolarian fauna is limited, age
assignments were based on a few distinctive and diagnostic robust
forms. Radiolarians occur in cherts from a wide variety of different
oceanic sequences that are structurally juxtaposed within the
Sylvester allochthon. Like others in a suite of correlative terranes
that lie along the length of the Cordillera, the Sylvester allochthon
and the radiolarian bearing cherts in it derive from the telescoping
together of slices from what was, in the late Paleozoic, a large area
of the proto-Pacific ocean.
Hashimoto, H. & Ishida, K. 1992. The radiolarian
assemblages and its age from the Sotoizumi Group, eastern
Shikoku. J. geol. Soc. Japan, 98/1, 61-63. (in Japanese)
Haslett, S. 1992. Early Pleistocene glacial-interglacial
radiolarian assemblages from the eastern equatorial Pacific. J.
Plankton Res., 14/11, 1553-1563.
Polycystine radiolaria from ODP Hole 677A in the eastern
equatorial Pacific were examined at isotopically identified Early
Pleistocene glacial maxima and minima. Two distinct radiolarian
assemblages are recognized, characterizing glacial and interglacial
optima. The Glacial Assemblage is characterized by high abundances
of Theocalyptra davisiana, Botryostrobus auritus, Anthocyrtidium
zanguebaricum and Hexacontium enthacanthum. The Interglacial
Assemblage is characterized by Tetrapyle octacantha, Octapyle
stenozoa and Theocorythium vetulum. A comparison of these fossil
assemblages with modern radiolarian distribution suggests that the
Glacial Assemblage represents intensified upwelling of cold
advected water via the Eastern Pacific Boundary Current, whilst the
Interglacial Assemblage indicates climatic amelioration in the
eastern equatorial Pacific, with the prevalence of warm (>21°C)
tropical/subtropical surface waters. The recognition of these
radiolarian assemblages could be successfully applied to studies of
adjacent east Pacific areas where other palaeoecological indicators
are lacking.
Hirano, H., Tanabe, K., Ando, H. & Futakami, M.
1992. Cretaceous forearc basin of Central Hokkaido:
lithofacies and biofacies characteristics. In: Paleozoic and
Mesozoic Terranes: Basement of the Japanese Island Arcs.
29th IGC Field Trip Guide Book. (Adachi, M. & Suzuki, K.,
Eds.), vol. 1. Nagoya University, Nagoya, Japan. pp. 45-80.
Hisada, K., Igo, H. & Arai, S. 1992. Mesozoic
melanges and associated rocks in the Kanto mountains. In:
Paleozoic and Mesozoic Terranes: Basement of the Japanese
Island Arcs. 29th IGC Field Trip Guide Book. (Adachi, M. &
Suzuki, K., Eds.), vol. 1. Nagoya University, Nagoya,
Japan. pp. 115-141.
Hisada, K.I., Karata, Y. & Kishida, Y. 1992.
Geology of the Yasudo area, northeastern part of the Kanto
mountains, central Japan. Annu. Rep. Inst. Geosci., Univ.
Tsukuba, 18, 53-58.
The northwest trending Chichibu Paleozoic- Mesozoic
sedimentary complex is widely underlain in the Chichibu terrane of
the Kanto mountains (Fig. 1). The Chichibu terrane is bounded on the
north by the Sambagawa high P/T type metamorphic rocks and on the
south by the Shimanto sedimentary complex terranes. The Shimanto
complex, which is composed of Cretaceous and Paleogene sandy
flysch and melange-like disturbed beds, is in fault contact with the
Chichibu complex. This fault has been traditionally called the
Butsuzo tectonic line and considered to be a southward vergent
thrust. The Sambagawa terrane comprises two-fold stratigraphic
units, namely the Mikabu green rocks in the upper part and the
Sambagawa crystalline schist in the lower. The Mikabu green rocks
usually occur just to the north of the Chichibu complex, and the
stratigraphical relationship between them was reported by some
authors (e.g. Uchida, 1981; Hisada, 1984). Their interpretations are
variously offered.
In the geologic map of the Kanto mountains (Fig. 1), it can be
recognized that the north-south width of the Sambagawa
metamorphic terrane widens remarkably in the Yasudo area, the
northeastern corner of the Kanto mountains, and that the Chichibu
sedimentary complex isolately crops out within the exposure area of
the Sambagawa terrane. This peculiar distributional pattern is an
interesting problem from the viewpoint of stratigraphy and