radiolaria - Marum

Bibliography - 1991 Radiolaria 14
The "Bonarelli Horizon", of Cenomanian to Turonian age, is a
thin (approximately one metre) layer within the Scaglia Bianca
Formation of the Umbria sequence of central Italy. It consists of
black mudstones rich in organic matter, silty shales and beds of
radiolarian siltstones and fine sandstones. The abundance of organic
matter reflects the anoxic conditions prevailing during its
deposition.
Several sections (Valle del Bottaccione, Valle della Contessa,
Monte Petrano, Valle del Burano and Gola del Furlo) show that the
Bonarelli Horizon includes a "lower" radiolarian assemblage
characterized by the presence of Novixitus mclaughlini, Thanarla
pulchra, Holocryptocanium astiensis, Archaeodictyomitra sliteri,
Pseudodictyomitra carpatica, and an "upper" assemblage where
Alievium superbum is present in association with Crucella cachensis
and Pseudoaulophacus putahensis. The transition between the
"lower" and "upper" assemblages represents a faunal event that, on
the basis of current knowledge of radiolarian biostratigraphy,
suggests a correlation with the Cenomanian-Turonian boundary.
Matsuda, T. & Isozaki, Y. 1991. Well-documented
travel history of Mesozoic pelagic chert in Japan; from
remote ocean to subduction zone. Tectonics, 10/2, 475-499.
The Mino-Tanba belt in southwest Japan, a segment of the
Cordilleran-type orogenic chain of Jurassic east Asia, is composed
mainly of a Middle-Upper Jurassic subduction-accretion complex in
which Triassic and Lower Jurassic bedded radiolarian cherts occur as
large allochthonous units structurally interlayered with Middle-Upper
Jurassic clastic rocks. High-resolution microfossil (conodont and
radiolaria) research has identified very low average sedimentation
rates of about 0.5 g/cm 2 /1000 yr in the chert units, similar to
those of modern pelagic sediments accumulated in open ocean
environments. Judging from the low average sedimentation rate, high
purity of biogenic silica, long duration of continuous deposition (>50
m.y.), and wide along-strike extent (>1000 km), the bedded
radiolarian cherts in the Mino-Tanba belt are best understood as
ancient pelagic sediments that accumulated in open ocean
environments; accordingly, the alleged origin in smaller marginal
basins is untenable. Upward lithologic change from bedded chert to
overlying siliceous mudstone in the uppermost portion of chert
sequences suggests the gradual landward approach of the oceanic
plate toward a trench. The tectonic interlayering of these cherts and
coarse-grained terrigenous clastics is a secondary feature that was
added through duplexing-underplating in the subduction zone. On the
basis of the primary stratigraphy and field occurrence of Triassic
bedded chert in the Mino-Tanba belt, newly proposed are an idealized
oceanic plate stratigraphy and a generalized travel history of a
Cordilleran-type bedded chert from its birth at a mid-oceanic ridge
to its demise at a subduction zone.
Matsuoka, A. 1991a. Early Jurassic radiolarians from the
Nanjo Massif in the Mino Terrane, central Japan. Part 1.
Tricolocapsa, Stichocapsa and Minocapsa, n. gen. Trans.
Proc. palaeont. Soc. Japan, n. Ser., 161, 720-738.
Well-preserved Early Jurassic radiolarians are obtained from a
manganese band in the Nanjo Massif, Mino Terrane, central Japan.
This paper is Part I of a serial descriptive work on an Early Jurassic
radiolarian fauna from the Nanjo Massif and deals with nassellarians
which possess a constricted or closed distal end. One new genus,
Minocapsa, is erected, and 9 new species and 2 new subspecies are
described: Tricolocapsa minoensis, T. (?) megaglobosa, T. (?) fera,
Stichocapsa plicata plicata, S. plicata semiplicata, S. elegans, S.
biconica, S. nanjoensis, Minocapsa cylindrica and M. globosa.
The fauna from the Nanjo Massif is very similar to that of the
upper Archicapsa pachyderma Zone of Jurassic radiolarian zones in
Japan. The fauna is correlative with the lower Toarcian fauna in eastcentral
Oregon, North America.
Matsuoka, A. 1991b. Middle Jurassic radiolarians from the
western Pacific. In: Proceedings of the International
Symposium on Shallow Tethys. Eds.), vol. 3. Saito Ho-on
Kai Special Publication, Sendai, Japan. pp. 163-173.
Middle Jurassic radiolarians have been recovered from the
western Pacific for the first time. The oldest faunas are assigned to
the middle and upper Tricolocapsa conexa Zone, indicating a
Bathonian/Callovian age. The faunas contain more than 30 species
and are characterized by an abundance of small nassellarians with a
constricted distal end. The faunas compare well with Tethyan faunas,
and are especially similar to Japanese faunas.
Minoura, K., Nakaya, S. & Takemura, A. 1991.
Origin of manganese carbonates in Jurassic red shale, central
Japan. Sedimentology, 38/1, 137-152.
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Manganese carbonate deposits in Japanese Jurassic
sedimentary rocks were studied petrogeochemically. The deposits
are characteristically composed of spheroidal micronodules, up to 1
mm in diameter, and always contain well-preserved radiolarian
shells. Chemical elemental composition and mineralogical
characteristics indicate that the micronodules contain rhodochrosite
in a mixed carbonate phase composition (Mn86.7-92.2Ca2.2-2.9Mg2.6- 6.7Fe2.6-5.6 )CO3. Carbon and oxygen isotope values, which range
from —7.99 to —4.78‰ and —4.05 to 0.28‰ relative to PDB,
respectively, suggest that the manganese carbonate was
precipitated in a suboxic zone. The micronodules closely resemble
agglutinated benthic foraminifera in shape. We suggest that
agglutinated foraminiferal tests composed of radiolarian shells
accumulated selectively on the sediment surface during redeposition
of bottom sediments and were replaced by manganese carbonate in
suboxic diagenetic conditions of manganese reduction.
Misík, M., Jablonsky, J., Ozvoldová, L. &
Halásová, E. 1991. Distal turbidites with pyroclastic
material in Malmian radiolarites of the Pieniny Klippen Belt
(Western Carpathians). Geologica carpath., 42/6, 341-360.
Acid and intermediary Upper Oxfordian volcanic material
transported from distant centres (probably the Eastern Alps) by
bottom currents (distal turbidites, or contourites) forms
intercalations in radiolarites of the Klippen Belt. The study of
radiolarians (U.A. 7-8 and U.A.9) and partly also of calcareous
nanoplankton allowed to determine a wider-stratigraphic span of red
radiolarians (Buwald Member) - minimally Upper Oxfordian—Lower
Kimmeridgian. The correlation between the thicknesses of
alternating silicite and pelite beds is insignificant (0.266). Fourteen
types of radiolarian preservation, various types of veinlets, the
presence of spheroids and slide structures allow to reconstruct to a
certain extent the processes of sedimentation and diagenesis.
Mizutani, S. & Yao, A. 1991. Radiolarians and terranes:
Mesozoic geology of Japan. Episodes, 14/3, 213-216.
Nobody can understand the geology of Japan without the
knowledge of radiolarian biostratigraphy and the concepts of
terranes. In the past decade, considerable research has been carried
out on radiolarian fossils, particularly those in the basement rocks
of Paleozoic and Mesozoic ages. The results indicate that Jurassic
formations are widespread and that they constitute an accretionary
complex. After establishing a new series of radiolarian fossil zones,
we have reexamined the stratigraphy of the basement rocks and
have recognized many tectonostratigraphic terranes in the Japanese
Islands. Discussion on the tectonic history of the Mesozoic terrain is
extended to that of eastern Asia in relation to accretion and
dispersion processes.
Molina-Cruz, A. 1991. Holocene palaeo-oceanography of
the northern Iceland Sea, indicated by Radiolaria and sponge
spicules. J. Quaternary Sci., 6/4, 303-312.
The micropalaeontological analysis of 49 samples, from three
box cores collected from the northern Iceland Plateau, indicates that
radiolarian and sponge remains are rare in glacial sediments but are
common after deglaciation; mostly during the first half of the
Holocene. Fluctuations in radiolarian abundance, and the first
occurrence of each of the species inhabiting the Iceland Sea at
present, coincide with changes in oceanographic conditions that
occurred during the Holocene
Morley, J.J., Heusser, L.E. & Shackleton, N.J.
1991. Late Pleistocene/Holocene radiolarian and pollen
record from sediments in the Sea of Okhotsk.
Paleoceanography, 6/1, 121-131.
In two cores with oxygen isotope stratigraphy from the
southern Okhotsk Sea, marine pollen and siliceous microfauna record
concurrent late glacial through Holocene variations in regional
terrestrial and marine environments. Glacial vegetation around the
southern Okhotsk basin, which resembles the present tundra/steppe
of the northwest coast of this marginal sea, yields to spruce
dominated boreal forests during the glacial/interglacial transition.
Temperate forest components, such as oak, peak during the mid-
Holocene. Decreasing oak accompanied by increasing spruce
reflects the effect of global cooling on local vegetation during the
last 4 kyr. Although the radiolarian fauna in the Okhotsk Sea
samples is similar to that present in the northwest Pacific, the
dominant species in both regions differ. Concentrations of
radiolarians are low in latest glacial samples, with higher
concentrations occurring above and below this interval.
Cycladophora davisiana, the dominant radiolarian species in the
majority of Holocene Okhotsk Sea sediments, is present at lower
percentages in late glacial samples from our two sites. Thus, this
species' Holocene/latest Pleistocene abundance pattern in Sea of
Okhotsk sediments is the reverse of that recorded in high-latitude