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Sanfilippo, A. and
Nigrini, C., 1995. Radiolarian stratigraphy across the Oligocene/ Miocene
transition. Mar. Micropaleontol., 24:239-285.
Abstract
Recently the
International Union of Geological Sciences (Commission on Stratigraphy,
Working Group on the Paleogene/Neogene Boundary) proposed that the
Oligocene/Miocene boundary be placed at the base of Chron C6Cn2n at 23.8
Ma on the Cande and Kent (1992) magnetic time scale, where it is
approximated by planktic foraminifera at the first occurrence of
Globorotalia kugleri, and by calcareous nannofossils at the last
occurrence of Sphenolithus ciperoensis and the first and last
occurrences of Sphenolithus delphix and S. capricornutus. Herein
we show that, in terms of radiolarians, the base of Chron C6Cn2n can be
correlated with the upper part of the Lychnocanoma elongata Zone
between the last occurrence of Artophormis gracilis (23.94 Ma)
and the first occurrence of Cyrtocapsella tetrapera (23.69 Ma).
Since the proposed
stratotype at Lemme—Carrosio (Italy) does not contain radiolarians at
the boundary, we re-examined 13 DSDP sites and established the
stratigraphic sequence of 29 first and last radiolarian occurrences and
one evolutionary transition across the boundary. Nine of these sites
contain both calcareous and siliceous microfossils and thus allow for an
integrated biostratigraphy. Paleomagnetic stratigraphy is not available
for any of the DSDP cores examined. However, use of Hodell and
Woodruff's (1994) strontium isotope curve from DSDP Site 289 has
permitted calibration of several low latitude microfossil datum levels
against the geomagnetic polarity scale. Two new species, Lychnocanoma
apodora and Eucyrtidium plesiodiaphanes, are described.
© Copyright
1999-2000, Elsevier Science, All rights reserved.
Sanfilippo, A. and
Nigrini, C., 1998. Code numbers for Cenozoic low latitude radiolarian
biostratigraphic zones and GPTS conversion tables. Mar. Micropaleontol.,
33:109-156.
Abstract
Code numbers for
the radiolarian zonation for the tropical Pacific, Indian and Atlantic
oceans (RP1—RP22 for the Paleogene and RN1—RN17 for the Neogene) are
standardized and introduced. Thirty-nine zones are recognized from the
Lower Paleocene to the Holocene. Revision of previously separate upper
Neogene zonations for the Pacific and Indian oceans, in which the same
zonal names were applied to different stratigraphic intervals, resulted
in a single tropical zonation. We change four upper Neogene Indian Ocean
zones to subzones and refer to them simply by their code numbers (RN12b
= Pterocanium prismatium, RN12a = Anthocyrtidium jenghisi, RN11b
= Stichocorys peregrina, RN11a = Phormostichoartus fistula).
We introduce the name Lychnodictyum audax Interval Zone (RN11)
for the interval stratigraphically equivalent to the combined Stichocorys
peregrina and Phormostichoartus fistula zones in the Indian
Ocean, and to the Anthocyrtidium jenghisi Zone in the Pacific
Ocean. Two Paleocene zones, Bekoma bidartensis (RP7) and B.
campechensis (RP6), and two subzones, Stylotrochus nitidus—Pterocodon
(?) poculum (RP6c) and Orbula discipulus (RP6b), are
emended. Each zone is formally defined and we include a
stratigraphically ordered list of radiolarian events falling within each
zone. Mean numerical ages for zonal boundary events were culled from
previous literature and converted to the geomagnetic polarity time scale
(GPTS). References to the original description and concept herein
applied of all included taxa, and tables which allow for accurate
conversion in simple increments between the different published GPTSs
are included in this paper.
Keyword(s):
Radiolaria; Cenozoic; tropical zonation; biostratigraphy; numerical
ages; code numbers
© Copyright
1999-2000, Elsevier Science, All rights reserved.
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Morley, J.J. and
Nigrini, C., 1995. Miocene to Pleistocene radiolarian biostratigraphy of
North Pacific Sites 881, 884, 885, 886 and 887. In Rea, D.K., Basov,
I.A., Scholl, D.W. and Allan, J F. (Eds.). Proc. ODP Sci. Results,
145: College Station, TX (Ocean Drilling Program), 55-91.
Abstract
Ocean Drilling
Program Leg 145 recovered sediments from seven sites in the North
Pacific, all of which contained radiolarians. The northernmost sites,
Site 884 on the eastern flank of the Detroit Seamount (Emperor Chain)
and Site 887 on the Patton-Murray Seamount Platform (Gulf of Alaska),
contained the oldest radiolarian-bearing sediments of lower Miocene age.
Radiolarian sediments from the central (885 and 886) and western (881)
North Pacific sites ranged in age from late Miocene to Pleistocene.
Based on their
stratigraphic potential, we selected 39 radiolarian species and
determined their abundance and preservation (entire radiolarian
assemblage) in Leg 145 sediments. The high-latitude North Pacific
Miocene through Pleistocene radiolarian population is described and
classified in detail, with the identification of a new species, Dictyophimus
bullatus, and subspecies, Lychnocanoma nipponica sakaii. This
research provides the critical stratigraphic link in the previously
disconnected Miocene and Pliocene siliceous faunal sequences from the
western and eastern margins of the North Pacific. Because of the nearly
complete sections recovered at the Leg 145 sites, many of which contain
excellent paleomagnetic records, it is possible to estimate with a
fairly high degree of accuracy the age of specific faunal events in the
various regions of the North Pacific. The results of this comprehensive
survey of the temporal and spatial distribution of radiolarians in
high-latitude North Pacific sediments are compared with those reported
previously from the North Pacific and other ocean regions, thereby
refining and expanding the siliceous faunal stratigraphy.
Shilov, V.V., 1995.
Miocene-Pliocene radiolarians from Leg 145, North Pacific. In Rea,
D.K., Basov, I.A., Scholl, D.W. and Allan, J.F. (Eds.). Proc. ODP Sci.
Results, 145: College Station, TX (Ocean Drilling Program), 96-116.
Abstract
Studies of
radiolarian assemblages from holes drilled during Leg 145 have revealed
the distribution pattern of species in the Miocene–Pliocene deposits
of the North Pacific. A brief revision of the application of
biostratigraphic zones Stichocorys peregrina (Riedel and
Sanfilippo, 1970, 1978) and Sphaeropyle langii (Foreman, 1975) in
the North Pacific has been conducted. A new Miocene–Pliocene zonation
based on radiolarians is proposed, which is correlated with diatom
biostratigraphic zones and paleomagnetic evidence. New species Acrospyris
lingi and Cenosphaera coronataformis are described.
Shilov, V.V., 1995.
Eocene-Oligocene radiolarians from Leg 145, North Pacific. In Rea,
D.K., Basov, I.A., Scholl, D.W. and Allan, J.F. (Eds.). Proc. ODP Sci.
Results, 145: College Station, TX (Ocean Drilling Program), 117-132.
Abstract
During the cruise
of ODP Leg 145 in the North Pacific Ocean, well-preserved Paleogene
radiolarians had been obtained from Holes 883B, 883E and 884B. Their
distribution pattern in these sections has been revealed and high-
latitude radiolarian assemblages in the North Pacific are described.
Biostratigraphic schemes proposed in low latitudes and other northern
hemisphere regions are not applicable on these assemblages, because most
zone marker species of other regions are absent in the North Pacific.
Two new species, Dictyomitra amygdala and Lithomitra micropore
have been described.
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