radiolaria - Marum

Radiolaria 14 Bibliography - 1992
lower Tithonian banded chert have an average sedimentation rate of
7 m/m.y.: (2) a discontinuity of probable late Tithonian-early
Berriasian age terminates the Tithonian banded chert; the overlying
Berriasian through Valanginian radiolarite has a mean sedimentation
rate of 11.5 m/m.y. These computed sedimentation rates and
interpreted discontinuities are consistent with the stratigraphy of
the recovered sediments and the uncertainties in the geological time
scale.
Eccentricity cycles identified in the gamma-ray signal were
matched to corresponding features on the Formation MicroScanner
high-resolution imagery of clay content and degree of silicification.
Eccentricity cycles are manifested as groupings of beds of higher
radiolarian content and silicification. Milankovitch climate cycles
may affect the intensity of equatorial Pacific upwelling, hence the
surface productivity of radiolarians, and the amount of eolian dust
and clay contributed to the sediments.
Momoi, H., Ishida, K. & Yamasaki, T. 1992.
Radiolarian geological ages of some host cherts of bedded
manganese ore deposits in the Chichibu belt of Ehime
Prefecture, Japan. Mem. Ehime Univ. nat. Sci., Ser. D (Earth
Sci.), 1, 71-89. (in Japanese)
Montgomery, H., Pessagno, E., Soegaard, K.,
Smith, C., Muñoz, I. & Pessagno, J. 1992.
Misconceptions concerning the Cretaceous/Tertiary boundary
at the Brazos River, Falls County, Texas. Earth and planet.
Sci. Lett., 109, 593-600.
Detailed biostratigraphic analysis (planktonic foraminifera and
nannofossils) of sixteen K/T (Cretaceous/Tertiary) boundary
sections in and near the Brazos River, Falls County, Texas indicates
that a lithologically distinctive, coarse clastic event bed previously
attributed to a meteorite impact-generated tsunami at the end of the
Cretaceous was actually deposited during the early Tertiary (Danian:
K/T + at least 230,000 years). A tsunami origin for this event bed
is doubtful, but if a bolide-splashdown tsunami did generate the
event bed, this putative meteorite impact must have occurred well
into the Danian during the post-extinction, faunal recovery phase
having little effect on extant foraminiferal and coccolith populations.
Montgomery, H., Pessagno, E.A.J. & Muñoz,
I.M. 1992. Jurassic (Tithonian) Radiolaria from La Désirade
(Lesser Antilles): preliminary paleontological and tectonic
implications. Tectonics, 11/6, 1426-1432.
Jurassic (upper Tithonian) Radiolaria recovered from bedded,
red ribbon cherts on La Désirade, Guadeloupe, are the oldest fossils
yet discovered in the Lesser Antilles. This age not only corroborates
contested isotopic ages for the igneous basement of La Désirade but
also demonstrates that previously reported differences in basement
ages for the central and eastern end of the island are invalid. In
addition, La Désirade chert yielded a higher-latitude, Northern
Tethyan to Southern Boreal Realm radiolarian assemblage (indicating
deposition at a minimum of 22° north or south of the Jurassic
paleoequator). Because Northern Tethyan or Boreal Jurassic oceanic
crust did not exist in the spreading gap between North and South
America, or east to Eurasia, we conclude that La Désirade oceanic
crust formed in the Pacific. The fact that no Upper Jurassic red
ribbon chert has been found in the Atlantic Ocean or in the Caribbean
aside from in displaced oceanic fragments in Puerto Rico and the
Dominican Republic lends additional support to a Pacific origin for
the oldest crustal fragment in the Lesser Antilles.
Mori, K., Okami, K. & Ehiro, M. 1992. Paleozoic
and Mesozoic sequences in the Kitakami 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. 81-114.
Motoyama, I. 1992. Neogene radiolarian stratigraphy in
the Tsugaru Peninsula, Aomori Prefecture, northern Japan. In:
Proceedings of the Third Radiolarian Symposium. (Sakai, T.
& Aita, Y., Eds.), vol. 8 . News of Osaka
Micropaleontologists, special Volume, Osaka. pp. 89-100.
(in Japanese)
Radiolarians have been analyzed from an middle Miocene
through Pliocene sequence of marine siliceous sediments exposed on
the Tsugaru Peninsula, northernmost Honshu. The middle to upper
Miocene diatomaceous mudstone contains well preserved siliceous
microfossils. Six radiolarian events were selected. Based on three of
them, five radiolarian zones were recognized: Eucyrtidium asanoi,
Eucyrtidium inflatum, Lychnocanoma nipponica magnacornuta,
"Anthocorys akitaensis" and Thecosphaera japonica. "A. akitaensis"
- 85 -
Zone is a new zone proposed for the middle upper Miocene. This
radiolarian stratigraphy was combined with the diatom stratigraphy
proposed by AKIBA (1986). A brief comment was made on the late
Miocene radiolarian assembrage.
Murchey, B.L. & Jones, D.L. 1992. A mid-Permian
chert event: widespread deposition of biogenic siliceous
sediments in coastal, island arc and oceanic basins. 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. 161-174.
Radiolarian and conodont correlations of Permian siliceous
rocks from twenty-three areas in the circum-Pacific and
Mediterranean regions reveal a widespread Permian Chert Event
during the middle Leonardian to Wordian. Radiolarian- and (or)
sponge spicule-rich siliceous sediments accumulated beneath high
productivity zones in coastal, island arc and oceanic basins. Most of
these deposits now crop out in fault-bounded accreted terranes.
Biogenic siliceous sediments did not accumulate in terranes
Iying beneath infertile waters including the marine sequences in
terranes of northern and central Alaska. The Permian Chert Event is
coeval with major phosphorite deposition along the western margin
of Pangea (Phosphoria Formation and related deposits).
A well-known analogue for this event is middle Miocene
deposition of biogenic siliceous sediments beneath high productivity
zones in many parts of the Pacific and concurrent deposition of
phosphatic as well as siliceous sediments in basins along the coast
of California. Interrelated factors associated with both the Miocene
and Permian depositional events include plate reorientations, small
sea-level rises and cool polar waters.
Murray, R.W., Jones, D.L. & Buchholtz-ten-
Brink, M.R. 1992. Diagenetic formation of bedded chert:
Evidence from chemistry of the chert-shale couplet. Geology,
20/3, 271-274.
Theories concerning the formation of bedded chert traditionally
have emphasized either depositional or diagenetic processes. Major
and rare earth element data from Franciscan assemblage (Mesozoic)
and Claremont Formation (Miocene) bedded chert sequences, along
with physical observations such as the presence of rare and highly
corroded radiolarians in shale interbeds, are most consistent with a
dominantly diagenetic origin of chert-shale couplets and are
incompatible with many depositional theories. Chemical distributions
between Franciscan and Claremont bedded chert-shale closely
match chemical fractionations recorded by Monterey Formation and
Deep Sea Drilling Project-sampled cherts formed by diagenetic SiO 2
dissolution, transport and reprecipitation, suggesting that diagenetic
migration of SiO 2 from proto-shale to proto-chert is also largely
responsible for chert-shale couplets. Identical Ce anomalies
(Ce/Ce*) found in immediately adjacent chert-shale layers indicate
that turbidites or other transport mechanisms are not responsible
for the alternating beds. Neither the chemistry of the chert-shale
couplet nor the overall stratigraphy of the sequences is consistent
with couplet formation being caused by productivity fluctuations.
Chemical mass balance calculations reconstructing the total bulk
sediment composition suggest that modern siliceous sequences do
not contain enough labile biogenic SiO 2 to form entire stratigraphies
of bedded chert.
Musashino, M., Imoto, N., Shimizu, D. &
Ishiga, H. 1992. Mesozoic accreted terranes of
northwestern Kyoto. 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. 205-212.
Nagai, H. & Mizutani, S. 1992. Jurassic (Bathonian)
radiolarians from the Snowshoe Formation, east-central
Oregon, North America. In: Proceedings of the Third
Radiolarian Symposium. (Sakai, T. & Aita, Y., Eds.), vol. 8.
News of Osaka Micropaleontologists, special Volume,
Osaka. pp. 47-61. (in Japanese)
We examined radiolarian fossils in the upper part of the
Snowshoe Formation of Oregon. Their geological age is assigned by
ammonite biostratigraphy to be late Bathonian. Eucyrtidiellum
pustulatum and Pantanellium foveatum, both being common in the
Japanese Jurassic formations, are found in the upper Bathonian part
of the Snowshoe Formation. On the basis of the concurrent
occurrence of these species and the evolutional trend of
Eucyrtidiellum as well, we reached the following conclusion: the
Japanese Upper Bathonian stage is located in a formation younger
than the Unuma echinatus assemblage zone and older than, or in the