radiolaria - Marum

Bibliography - 1990 Radiolaria 14
preserved Radiolaria were recovered not only from strata overlying
the Josephine ophiolite, but also from within the volcanic member of
the ophiolite. U/Pb geochronometric data constrain the age of the
Mirifusus first-occurrence event to after 162 ± 1 Ma and to being
157 ±1.5 Ma or slightly older. Radiolarian faunal data indicate that
the Josephine ophiolite originated at Central Tethyan paleolatitudes
during the latest Callovian (162 Ma) and was carried northward to
Northern Tethyan and Southern Boreal paleolatitudes during the
Oxfordian.
Petercáková, M. 1990. Radiolarian from cherts of the
Kalisco limestone formation of the Manin unit (Butkov,
West Carpathians). Geol. Sb. (Bratislava), 41/2, 155-169.
The work deals with the first occurrence of radiolarians in the
Lower Cretaceous pelagic sediments of the Manin unit of the West
Carpathians. The radiolarians come from cherts of Kalisco
Limestones that in the past were stratigraphically investigated by
means of ammonites and tintinnoid organisms (Vasicek—Michalik,
1986; Borza et al., 1987). Radiolarian species characterizing the
zone Mirifusus chenodes (sensu SCHAAF, 1984) were identified,
which stratigraphically corresponds to the uppermost part of the
Lower Hauterivian.
Petrushevskaya, M.G. & Swanberg, N.R. 1990.
Variability in skeletal morphology of colonial Radiolaria
(Actinopoda: Polycystinea: Collosphaeridae).
MIcropaleontoloy, 36/1, 65-85.
Skeletal morphology is used to determine species in almost all
Radiolaria, and in many cases relatively fine differences between
morphotypes are used to distinguish between species. While many
Radiolaria have been described from very few specimens we have
little knowledge of variability of Radiolaria because we have been
able to study few known biological populations of a species. This
problem has been addressed by examining the variation occurring
within colonies of collosphaerid Radiolaria, and comparing it to that
occurring between colonies of the same and other species. As far as
we know the cells within such colonies are genetically identical and
therefore intra-colony variation must be caused by other than
species-level phenomena.
Both quantitative and qualitative features were considered in a
detailed study of a total of 2922 skeletons in 44 colonies
representing 12 species. The results of this analysis have revealed
substantial variation in both quantitative and qualitative features,
both between and within colonies of a species. Furthermore, typically
1-5% and sometimes even 10-20% of the individuals in a colony
possess some structures which are absent in the majority of
individuals of the species. The structures which are characteristic
for one species, typically occurred at a low rate in another. No
smooth transition between species was seen provided that one
considered the whole suite of diagnostic morphological features and
not just a single character. Caution is strongly urged in uncertain
species assignments and it is asserted that it is absolutely
impossible to erect new species on the basis of a few specimens
which are non-identical, or on the appearance of a single feature.
Raymond, D. & Lethiers, F. 1990. Signification
géodynamique de l'événement radiolaritique dinantien dans les
zones externes sud-varisques (Sud de la France et Nord de
l'Espagne). C.R. Acad. Sci. (Paris), Sér. II, 310, 1263-1269.
In the South of France and the North of Spain the radiolarites
from Dinantian age have been deposited in a narrow basin initiated
since the Frasnian times and bordered by emerged areas. The
starting of the siliceous deposition would be related to the
installation of cold deep-water currents coming from a Late
Devonian-Early Carboniferous glacial North-Gondwanian area.
Special ostracod faunas corroborate these paleoecologic changes.
Renz, G.W. 1990. Ordovician Radiolaria from Nevada and
Newfoundland a comparison at the family level. Mar.
Micropaleontol., 15/3-4, 393-402.
Two Ordovician radiolarian assemblages from North America
are examined and compared at the family (group) level. In the
material from Newfoundland (Middle Ordovician—Llanvirnian, after
Bergstrom, 1974), well-preserved specimens are common, 92%
being spherical polycystines. In the Nevada material (Upper
Ordovician—Caradocian, after Dunham and Murphy, 1976), wellpreserved
specimens are abundant and coated with iron oxide. Here
species of spherical polycystines constitute only 42% of the
population while species of Palaeoscenidiidae, after their appearance
and radiation within the preceding 25 million years, constitute 47%.
Results of this comparison at the family level suggest that for
radiolarians, evolutionary change during the Ordovician was not slow
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as previously thought. Rather, this was a time of growth, radiation
and experimentation.
Riedel, W.R. 1990. Quantitative description of pore
patterns in radiolaria. Micropaleontology, 36/2, 177-181.
The arrangement of pores in the lattice-shells of radiolarians
can be an important descriptor of the skeletons, if the pattern can
be characterized quantitatively. An image analysis system
integrated with a personal computer provides a convenient means of
measuring distances between pores, and their angular relations,
together with the variability of those measures. Both regular and
irregular patterns can be quantified. The procedure is adaptable to a
wide spectrum of patterns in the organic world.
Sanfilippo, A. 1990. Origin of the subgenra
Cyclampterium, Paralampterium and Sciadiopeplus from
Lophocyrtis (Lophocyrtis) (Radiolaria, Theoperidae). Mar.
Micropaleontol., 15/3-4, 287-312.
Work on the exceptionally well-preserved, rapidly accumulating
Bath Cliff Section, Barbados and supplementary Deep Sea Drilling
Project samples, has revealed the evolutionary origins of three
stratigraphically useful species in the Cryptoprora ornata Zone
straddling the Eocene/Oligocene boundary and demonstrated the
origin of the genus Cyclampterium. Elucidation of the origin of
Cyclampterium milowi necessitates a revision of the genera
Lophocyrtis and Cyclampterium. Lophocyrtis (Lophocyrtis) jacchia is
the ancestor of L. (Cyclampterium) hadra, the earliest member in the
subgenus Cyclampterium which comprises the anagenetic lineage
leading from L. (C.) hadra to L. (C.) neatum. The monotypic subgenus
Sciadiopeplus branches off from an early member in the
Cyclampterium lineage. The new species L. (L.) exitelus and L. (S.)
oberhaensliae terminate the subgenera Lophocyrtis and
Sciadiopeplus, respectively. During the investigation it also became
clear that morphotypes resembling early L. (C.) milowi could be
found in mid and high latitude assemblages in the late Early and late
Middle Eocene. The origin of one these morphotypes was also traced
to L . (Lophocyrtis) jacchia giving rise to the new subgenus
Paralampterium. This lineage includes the new species L .
(Paralampterium) dumitricai and two species questionably assigned
to it, L. (Paralampterium) ? Iongiventer and the new species L.
(Paralampterium) ? galenum. The relationship of L. (P.) dumitricai to
L. (P.) ? Iongiventer and L. (P.) ? galenum is unknown.
Schwartzapfel, J.A. 1990. Biostratigraphic
investigations of Late Paleozoic (Upper Devonian to
Mississipian) Radiolaria within the Arbuckle Mountains and
Ardmore. Ph.D Thesis. Programs in Geoscience, University
of Texas at Dallas, p. (unpublished)
Sedlock, R.L. & Isozaki, Y. 1990. Lithology and
biostratigraphy of Franciscan-like chert and associated rocks
in west-central Baja California, Mexico. Geol. Soc. Amer.,
Bull., 102, 852-864.
We present the result of biostratigraphic and lithologic studies
of ribbon chert and associated rocks in a Mesozoic subduction
complex in west-central Baja California, Mexico. The subduction
complex terrane is divided into three subterranes, each of which
consists of an originally coherent sequence of interbedded oceanic
rocks, including ocean-floor basalt, terrigenous siliciclastic
turbidites, radiolarian ribbon chert, and limestone. Parts of the
original stratigraphy are preserved in the least deformed, least
metamorphosed subterrane. Ocean-floor pillow basalt on Cedros
Island is overlain by about 40 m of radiolarian ribbon chert ranging in
age from Early Jurassic or older to Early Cretaceous; the chert is
overlain by thin-bedded turbidites. On San Benito West Island,
radiolarian ribbon chert is interbedded with volcanogenic rocks,
including a megabreccia that contains blocks of metabasites, folded
Late Jurassic-Early Cretaceous chert, and marble in a mid-
Cretaceous radiolarite matrix. Chert samples from tectonically
thinned sequences elsewhere on Cedros and San Benito Islands
contain Late Triassic to Early Cretaceous radiolarian assemblages.
The 40-m-thick chert section on Cedros Island probably
accumulated atop oceanic crust in a large ocean basin for at least
65 m.y. and was later capped by terrigenous turbidites as it
approached the subduction zone along the western margin of North
America. Faulted chert sections on Cedros and San Benito Central
and West Islands are subsets of the main section on Cedros Island.
The chert/megabreccia section on San Benito West Island is
interpreted to have accumulated at the foot of a volcanic edifice on
the ocean floor (for example, seamount, fracture zone) or during
extension and normal faulting of the downgoing oceanic plate in a
subduction zone. Sedimentary structures and stratigraphic relations
indicate that all ribbon chert in this subduction complex was
deposited by sediment gravity flows; that is, they are turbidites.