Cenozoic radiolarians of the Antarctic, Leg 29, DSDP, in

135 Pages·2007·23.82 MB·English

14. CENOZOIC RADIOLARIANS OF THE ANTARCTIC, LEG 29, DSDP
M. G. Petrushevskaya, Institute of Zoology, Academy of Sciences, Leningrad, USSR
INTRODUCTION1 contained in a small volume of bottom sediment cannot
be considered as remains of one population. Thus: (1)
Methods and Materials they accumulated for hundreds or even thousands of
years; and (2) these skeletons might belong to specimens
The samples from Leg 29 were mounted in balsam
which inhabited various depths and belonged to pop-
without additional shipboard processing, and then
ulations of various natures. Petrushevskaya (1969a,
studied and photographed by means of a light-
1971a) has stressed that using the term "population"
microscope. Since the details of the skeletal structure are
with regard to radiolarian remains in one bottom sedi-
frequently indistinguishable on the photographs, the
ment sample is not justified.
author made additional hand drawn illustrations. Four
The species characteristics in micropaleontological in-
samples were specially washed in order to study the
vestigations are generally rather poor. Thus, if an in-
radiolarian skeletons by means of a scanning electron
vestigator deals essentially with the peculiarities of the
microscope.
skeleton morphology, the question arises whether the in-
Special attention was paid to the almost continuous
vestigator is dealing with a biological species or with
and comparatively undisturbed sequence obtained at
some tentative unit, i.e. "morphotype," according to the
Site 278. Other sites of Leg 29 which were studied are
terminology of Riedel and some other American
shown in Figure 1.
authors.
These data were compared with the radiolarians in the
cores of bottom sediments, taken in the Antarctic and
Species Content
subantarctic by the R/V Ob and Eltanin. Such a com-
Aside from these problems, there is need to discuss
parison was necessary, since some of these cores (Ob
the question of species content in micropaleontological
Station 256, Eltanin, E-14-8, E-13-4) can be considered
investigations. In the present study, in tracing by sec-
as stratotypical for the Pleistocene, Pliocene, and even
tions (which, for example, encompass the Upper
the uppermost Miocene of high southern hemisphere
Oligocene-Pliocene) for the distribution of species such
latitudes. Neither the radiolarian species composition in
as Diplocyclas bicorona or Antarctissa capitata, it was
the studied area, nor the schemes of radiolarian
necessary to consider these species "sensu lato," i.e., in a
biostratigraphy were known from earlier (older) layers.
broader sense than in previous studies which were con-
As a result of the studies herein it was concluded that an
fined to a shorter time interval (Holocene or Recent).
age determination of Eocene, Oligocene, and Miocene
This is due not only to the fact that more specimens (at
deposits in the area between 45°-55°S lat is quite possi-
smaller magnifications) had to be analyzed, but also that
ble by means of radiolarians. For the Antarctic Miocene
a more detailed division of these taxonomic units and
deposits, a rather detailed stratigraphic scheme was
the isolation of subordinate groups within their range
suggested.
did not correspond to the task of the investigations. The
The discussion to follow is supported by data con-
term "species group" seems justified here. The term was
tained in Tables 1-8, and illustrations contained on
initially used by Riedel (Riedel and Sanfilippo, 1970,
Figures 1-10.
1971; Sanfilippo and Riedel, 1970, 1973). These are, of
Purpose and Investigative Problems course, not species, but groups of morphologically ex-
tremely closely related forms, which are clearly differen-
Since the stratigraphy and isolation of "radiolarian
tiated from other radiolarians encountered in the same
zones" is based on the temporal and spatial distribution
sediments. Such "species-groups" will probably corres-
of individual species, the goal of this micropaleon-
pond to the generic categories of biologists. The study of
tological study is to establish the limits and content of
the temporal and spatial distribution of such com-
the individual radiolarian species.
paratively easily distinguishable groups is a real problem
During recent years the word "population" is often
in view of the extremely short time available for the
used in the literature on fossil radiolarians. However,
work. On the other hand, the "species groups," (as has
the complex of skeletons in bottom sediments represents
been shown by the experience of a number of cruises)
a thanatocoenosis, whereas the skeletons of one species
yield a sufficiently reliable basis for the determination of
age and stratigraphic correlations.
Frequently the observed disappearance or reduced
numbers of one "morphotype" and the appearance of a
'Editor's footnote: We were unable to confirm from the author great number of specimens of another very close type
many of the reference citations used in this manuscript. Most of these
can be regarded as either a new state of the species, or
citations are those with the same reference year, while other references
were not found. All those unestablished will be noted with a (?). the appearance of a new species (Riedel and Sanfilippo,
541
M. G. PETRUSHEVSKAYA
ttob 268
Ob 256^ . T-
x
60 60
60 120
Recent radiolarian
Species: tropical transition subantarctic Antarctic
Figure 1. Recent radiolarian species distribution in the subantarctic southwest Pacific and Leg 29 site and sampling locations.
1971). Establishing the temporal limits of the taxon by phenomenon. In biology, it is also assumed that species
the numerical predominance of the corresponding evolution could have been "bouquet-like" when many
"morphotype" is really possible for such abundant species appeared at once.
forms as Stichocorys wolffii, S. delmontense, and S. Thus, the determination of the actual temporal limits
peregrinus, or such species as Cannartus. In these cases, of the species can, in some cases, be based on the fact
the appearance of only one taxon at a time is assumed. that there are two (rarely more) daughter species, which
Figure 2 shows how the boundaries of five species which came in as a replacement of the ancestral one.
consecutively replace one another are determined. The Very often in the study of continuous sections
appearance of one single species ("morphotype") which (especially in the case of a low rate of sediment ac-
replaced the original one actually occurred in the history cumulation), the traces and evidence of evolutionary
of Polycystina; for example, the development of the changes, which took place in the history of a particular
Pliocene Pterocanium prismatium Riedel from the radiolarian group, present a rather complicated picture.
Oligocene form described by Petrushevskaya (71973, fig. The more numerous the specimens of this group, the
5), or the derivation of Saccospyris antarctica from S. more complicated the picture. Consider the samples cor-
preantarctica (this study). responding to the time period "M" shown on Figure 3.
However, it is hard to assume that the consecutive It is difficult to decide (merely on the basis of the
replacement of the predominant "morphotype" morphological peculiarities and the numerical strength
("morphotypic-evolutionary" or "evolutionary" limits of the "morphotypes"), whether there is only the
between taxa [Sanfilippo and Riedel, 1973]) is the βasic ancestral species "P" with its characteristic
and only mechanism of radiolarian evolution. Beginning polymorphism, or whether there are three species (Pa;
with Darwin, divergence is considered as the basic Pb, c, d, e; Pf) or even six species (= morphotypes?): PA,
course of the evolution of all animals. Two forms, which PB, PC, PD, PE, and PF. The new state of the ancestral
most strongly differ from one another in all species, due to some cause ("q" on Figure 3) should not
characteristics, survive, whereas the intermediate forms necessarily have affected the morphology of all
sooner or later become extinct. The appearance of only morphological forms of the initial species with an equal
one single form is considered as a more infrequent degree of speed and distinctness. Later, when the two
542
CENOZOIC RADIOLARIANS OF THE ANTARCTIC
A
successively younger morphotype
forms:
a b c d e
W
I c i
abundant frequent Figure 4. Alternate phytogenies for species A and B.
rare
Figure 2. Boundaries of five species as determined by the
appearance of one taxon at a time. B, Figure 4), which is a food competitor of Species A,
becomes extinct. Species B might disappear not only
because it is forced out by Species A, but also because of
changes in temperature and salinity. In this case Species
B is unable to adapt in contrast to Species A which can
adapt easily. Consequently, when studying their remains
in bottom sediments, one gets the impression that
Species A originated much later than it actually did (i.e.,
at the moment when it became more numerous). If, in
addition, Species A and B are morphologically close, it
might appear that Species A derived from Species B,
whereas in fact they might have a more of less distant
common ancestor. The author believes that such cases
the change were most frequent during the evolution of new taxa of
because of polycystine radiolarians. Upon investigation of a great
"q"
number of samples, single specimens of a morphological
form which usually occurs in recent layers can be also
discovered in more ancient ones. An example of this can
be found with Clathrocyclas bicornis Popofsky.
Figure 3. Divergence of the characters of the parent species.
Geographic Distribution of Individual Species
Determining the geographical distribution of the
individual species is of primary importance, since the
daughter-species are more individualized, a differentia- zone which has been marked by the name of some
tion between them and the ancestral species as quite easy species can be traced within the range of the distribution
to determine. The determination of the temporal limit of of this species. The problems of the geographical dis-
the species "P" and "PA" and "PF" is also possible, tribution of radiolarians, the importance of the defini-
although on a comparatively larger temporal scale (ap- tion of subspecies, etc., has been dealt with in detail by
proximately time period "M"). The determination of Riedel (1973). However, it is important to note that a
such a period is not difficult, provided that all of the once widely distributed species can, with change of the
species are sufficiently numerous. hydrological regime, also change its area of distribution
However, cases are completely possible, when a (Figure 5). This is exemplified by Saturnalis circularis
species remains (upon having appeared) rather small in and Pterocanium trilobum, which were suggested by
number until such time as its numerical strength begins Hays (1965) as indicator-species of Zone x in subantarc-
suddenly to increase (Species A, Figure 4). The increase tic sediments. It was found (Petrushevskaya, 1971a, b;
continues up to the time when the other species (Species Petrushevskaya and Linjkova, 1972) that in S. circularis
543
M. G. PETRUSHEVSKAYA
developed, and that at the present time the various areas
of the world's oceans are inhabited by various species
50° 40°
and subspecies of each of these species groups.
However, there are among these taxa very distinct units
{Artostrobus annulatus, Cyrtolagena laguncula). It can be
assumed almost with certainty that they correspond to
the present biological species. The long period of their
existence (since the middle or even early Miocene) can
be explained by the fact that they are inhabiting abyssal
waters, where the hydrological conditions are com-
paratively stable; it can also be due to the predominance
of agamous reproduction, which does not yield great
possibilities for the development of forms. However, the
present wide distribution of these species can obviously
be ascribed only to their inhabiting deep waters.
The other of the present living species: Antarctissa
strelkovi, Triceraspyris antarctica, Lithelius? nautiloides,
Lithamphora furcaspiculata typ., Schizodiscus favus max-
ima, Spongurus? pylomaticus, and Saccospyris antarctica
are at the present time endemic to the Antarctic. Some
of these species became characteristic of the middle
Miocene in the Antarctic {Lithelius? nautiloides), others
of the late Miocene {Lithamphora furcaspiculata,
Schizodiscus favus maxima), and some {Spongurus?
pylomaticus, Saccospyris antarctica) of the Pliocene.
The probable ancestors of some of these presently liv-
ing species, can be defined: Ceratocyrtis sp. "r" for An-
tarctissa strelkovi; Lithelius? nautiloides form "p", for
Figure 5. Area of distribution o/Saturnalis circularis (ver- L.? nautiloides; Lithamphora sp. aff. L. corbula (Harting)
tical lines represent cores investigated). for L. furcaspiculata, and Saccospyris preantarctica for
S. antarctica. In all cases, the ancestral and daughter
species existed simultaneously in one area, followed by
the extinction of the ancestral species. Evidence of the
divergence, as well as of the appearance of two daughter
and possibly in P. trilobum, the area of distribution was species, could be noted only at the formation of
narrowed considerably during the Pleistocene (Figure Lithamphora furcaspiculata, i.e., in a form ancestral not
5A). Thus, the definition of stratigraphic zones by such only to L. furcaspiculata but also to L. corbula typ.
species is extremely difficult.
DATA ON EVOLUTIONARY LINEAGES
The above examples are obviously not unique. There
is reason to believe that in a more distant era (Oligocene, In the brief summary of data to follow, brief mention
early Miocene), areas of the Antarctic represented an ex- will be made of the history of the species (morphological
traordinary refuge for relics of the Eocene fauna. Thus, groups?). In some cases there obviously occurred sub-
the typical Amphymenium splendiarmatum Clark and stantial changes, which led to the formation of new
Campbell is widely represented in the Eocene deposits of species(?) or morphotypes. Most of the taxa have not
the tropics (Sanfilippo and Riedel, 1973); in the Antarc- been described yet and do not have binomial names.
tic, a very closely related morphological form (Plate 7, In the Cenosphaera cristata group, the Miocene in-
Figure 1) survived right to the middle of the Miocene. dividuals (form "B") had very delicate inner spheres
In reference to the species or species groups of (first shell); then the skeletal sphere was reduced, which
Polycystina which presently inhabit the Antarctic, it led to the formation of the typical C. cristata.
can, in the case of Spongodiscus resurgens, Stylodictya In the Stylosphaera hispida Ehr. group, some outer
stellata group, Artostrobus annulatus, Lithomitra radial spines (nonpolar) were reduced in the latest
arachnea, Cyrtolagena laguncula, Cornutella profunda, Miocene. The taxonomic status of the various forms of
Diplocyclas bicorona group, and Peripyramis cir- this species group still has to be investigated.
cumtexta (Plate 5) be assumed with certainty that these In the Lithelius? nautiloides group, the form "P" had a
taxa existed since the early Miocene. During the larger, elongated skeleton covered with a "mantle". In
Miocene they were widely distributed not only in the the descendant form L.? nautilus typ., the outermost
Antarctic but also in the central Atlantic and California parts of the skeleton (and the "mantle") are reduced
(Campbell and Clark, 1944a, b; Petrushevskaya, 1969a, (Plate 3, Figures 1, 3, and 5).
b; Petrushevskaya and Kozlova, 1972). Presently they In the Amphymenium? splendiarmatum group, the
are generally widely distributed. However, objections spongy meshes in the distal ends of the arms were more
might be raised (when speaking of groups of species), numerous in Antarctic early Miocene specimens than in
that the systematics of this group are not sufficiently the Eocene-Oligocene specimens.
544
CENOZOIC RADIOLARIANS OF THE ANTARCTIC
In the lineage group lineage, an increase in the number of chambered
rings and a reduction in the size of meshes (chambers)
Artostrobus sp. Cr.
might have taken place.
not only did the cephalis increase (elongate), but there In the lineage of segmented Paleocene Cyrtophormis
was also an elongation of the upper part of the thorax sp. Ch. (Plate 8, Figures 16, 22)—‰Stichopodium sac-
and the formation of a "pedestal." coi—' S. calvertense—‰-S. biconicum and the other
In the lineage multisegmented Miocene Stichopodium species, various
Gondvanaria sp. ^_^^—-*-G. dogeli (1) patterns of segmentation of the postthoracic part of the
(Plate 25, Figure 5)^ "~~.?—Dictyophimus hirundo (2), shell might have occurred.
there is a tendency toward a decrease of appendages (1), In the lineage of Thyrocyrtis bromia—l -Androcyclas
and perhaps a diminishing of appendages (2). heteroporous and some Lamprocyclas species described
In the Lychnocanella conica group, the Oligocene by Kung (1973)—‰~Androcyclas gamphonychos, there
specimens were larger and their cephalis globular. The seemingly occurred an elongation of the cephalis and the
Miocene specimens were smaller, with cephalis set on a development of its lateral lobes.
"pedestal." In the multisegmented lineage Clathrocyclas sp. aff.
In the C. nova (Plate 15, ?„<-—--~~C• universa group (1)
•L. corbula typ. (1) Figure 17) " *^C. titanothericeraos (2),
Lithamphora sp. aff. L. corbuia<
furcaspiculata (2) a reduction in the number of segments, and (2) the
lineage, different tendencies were observed: (1) in the development of the Vert-horn might have taken place.
tropic specimens stabilization in the segment shape and In the lineage
pore distribution; (2) in the Antarctic, more advanced, Ceratocyrtis sp. aff. C. cucullaris —VC. amplus—?—
thinner shells of irregular outline and pores. ^______——Ceratocyrtis sp. "f ~Antarctissa strelkovi,
In a large species group (in this paper referred to as -*~Antarctica clausa
the Anthocyrtella kruegeri group), the Oligocene-early various tendencies might have developed.
Miocene specimens had multisegmented shells (see In Antarctissa capitata—?- A. denticulata lineage, the
Petrushevskaya and Kozlova, 1972, pi. 25, fig. 3). The walls might have thickened.
skeleton of the late Miocene-Quaternary individuals
consists of only two to three segments. RADIOLARIAN STRATIGRAPHY
In the Ceratocyrtis sp. "r" —— Antarctissa strelkovi The time of the first appearance of new species among
lineage, a reduction in the thorax length and an elonga- fossil remains, the period of simultaneous existence of
tion of the eucephalic lobe seems to have taken place. the daughter and ancestral species, and the time of a
In the Desmospyris rhodospyroides - ~D. spongiosa complete disappearance of the ancestral species are (as
lineage, the walls of the shell become thick, the pores in- far as can be judged by the studied sections) rather ex-
crease in number, their distribution becomes less tensive periods. Tables 3-7, the sections corresponding
regular, and the surface becomes spongy. to those periods of time have a hachured symbol. In
In the Saccospyris preantarctica —*~S. antarctica order to substantiate stratigraphic boundaries, not only
lineage, the skeletons become larger, the walls thicker, were frequently lengthy evolutionary changes in the
and the appendages weaker. radiolarian fauna used but also the appearance or dis-
appearance of other species (morphotypes) in the
Questionable Evolutionary Changes
skeletal sediments. For the latter, the history of the
Lithelius? foremanae group—— ?L. nautiloides form evolution is so far completely unclear.
"p." It should be noted that the species characteristic for
Pylospira sp. A ~?Phorticium clevei (by reduction of the upper Miocene and Pliocene deposits in the tropics,
part of the external skeletal latticed plates). and used mostly as age indicators of these deposits, were
Lithocarpium sp. aff. L. monikae (Plate 4, Figures 6- not encountered any farther south than the Polar Front
10)- area. This has been shown by Petrushevskaya (71973)
^Lithocarpium monikae typ. ——?some for Stichocorys peregrinus and Pterocanium prismatium,
/ Plegmosphaera species as well as for some other species in the present article. In
-Lithocarpium titan (by reduction of internal the deposits of higher latitudes, otherwise well studied
spirals) species still cannot be identified with certainty.
Lithocarpium fragilis (the "mantle" becomes Therefore, a stratigraphic correlation of the Miocene
less regular). deposits investigated from the Antarctic with the more
The lineage (partly indicated by Sanfilippo and thoroughly studied tropical faunas is rather difficult. It
Riedel, 1973) Stylotrochus? alveatus Sanfilippo and is, however, feasible to assume that the stages of the
Riedel—η. Porodiscus? charlestonensis Clark and development of the climatic aspects of the earth had an
Campbell—7-^P. bergontianus Carnevale—?-—P.? cir- equal effect upon the development of radiolarians in the
cularis Clark and Campbell—7— Trematodiscus? ellip- tropics as well as upon those in the higher latitudes of
ticus Stöhr—η.- T.? microporus Stöhr. Here, an increase the southern hemisphere. In the sediments of the
in the size of the central meshes (chambers) and a reduc- middle-upper and upper Miocene of the Antarctic,
tion in their number seem to take place. sharp and extremely frequent changes are noticeable,
In the Xiphospyra ocellata—?-—X. splen- which probably correspond to five or even six
des—i÷-Stylodictya gracilis—l -Stylodictya stellata "radiolarian zones" (Stichocorys peregrinus, Ommatar-
545
TABLE 1 p
Radiolarian Events Used to Establish Radiolarian Zones at DSDP Leg 29, 256; and Eltanin 14-8 Sites
H
DSDP Leg 29 Eltanin Ob JO
a
14-8
Zone No Radiolarian Events 280A 281 278 280 13-17 256 268
, -j
/ Actinomma buspinigera (Hays) (top) n/Φ
/, Stylosphaera hispida Ehr.=
\^ Stylatractus universus Hays (top)
\ Perichlamidium sp. Q Petrush. (top)
^ / Pylospira sp. L. florish 4,CC 2-1 y 640 cm
/ Antarctissa cylindrica Petrush. (top) _ _ _ x
(2 Actinomma tetrapyla (Hays) (top) above? 3-5 7-6 x
\ Saccospyris preantarctica np. (top) 2-1 x
\ Octodendron sp. Hays (top) X
/ Clathrocyclas bicornis Hays (top) 3-2 5-6 xlΦ
<^3 Pterocanium prismatium Riedel (top) x
\. Stichopodium biconicum (Vinassa) (top) 3-2 3-2 1-2 xlΦ
/ Saccospyris antarctica Haecker (bottom) 7-4
<4 Diplocyclas davisiana (Ehr.) (bottom) 8-2
B \^ Spongurus pylomaticus Riedel (bottom) 7-6
/ Pseudocubus vema (Hays) (top) 0/7
/ Desmospyris spongiosa Hays (top) 8-5
/ Ommatodiscus haeckeli Stohr 6-3 8-5 below 1-2 7
( 5 (becomes untypical, dense or hollow)
\ Stichororays peregrinus (Riedel) (top) •)
\ Androcyclas heteroporus (Hays) (top) 3-2
\ Lychocanium grande Campbell and Clark (top) 3,CC 16-3 7
/ Clathrocyclas cabriloensis 9-3
I Campbell and Clark (top)
/ Perichlamidium sp. Q (bottom) Below 3, CC 2-1
/g Antarctissa cylindrica n. sp. (bottom) 9-3 T/T
\ Oroscena "digitate" Friend and Riedel (top)
\ Gondvanaria japonica (Nakaseko) (top) 9-3
\ Calocyclas ?redondoensis (Campbell 7/T
\ and Clark) (top)
/ Stichopodium inflatum (Kling) from 11-1
/ is present to 9-5
/ Astrompos Antkpenultimus from 6-3
j is present to 4, CC
V / j Heliodiscus sp. from 11-5
\ is present to 10-1
\ Lychnocanium sp. C 5-2 from 11-6 from 1,CC T
\ is present to 10-1 to 1-4
\ Haliommetta miucenica from 4, CC
\ (Campbell and Clark) florish to 3-5
/ Botryometra poljanskii n. sp. from 12-3
/ is present to 10-6
/ Desmospyris rhodospyroides n. sp. (top) 9,CC 10-6
/ Botryopyle sp. A (top) 10-6 T
( 8 Lithocarpium polyacantha (Campbell 2,CC above 10-6 below 1-2 T
\ and Clark (become dense, untypical)
\ Clathrocyclas humerus n. sp. (top) 11-1 1-2 T
\ Lithocampe subligata (Stohr) (top) 35 17-5 1-2 T
\ Lithocarpium fragilis (Stohr) (top) 11-2
/S Cricodiscus ellipticus (Stohr) (top) 11-4
\9 Lithocampe (Cyrtocapsella) from 9, CC from 12-1 ICC T
\^ Comiesse is present to 5-1 to 11-6
Astromma hughesi (Campbell and from 8-6
Clark) is present to 7-3
Sponguridae gen. sp. from 13-6
is present to 12-1
Actinomma golownini n. sp. (top) above 9-3 12-1 1,CC atyp
Antarctissa robusta n. sp. (top) 12-2 from 1,CC
to 1-2
Circodiscus microporus (Stohr) (top) 9-3 12-6
Astromma petterssoni (Riedel) is present 9,CC
Botry opera deflandrei n. sp. (top) 14-1 T
Clathrocyclas titanothericeraos 14-1
(Campbell and Clark) (top)
Schizodiscus cod rant n. sp. 14-3
is replaced by Sch. disymmetricus
Dogel and by Sch. favus var. maxima
Popof sky
Spongodiscus craticulatus (Stohr) 14-4
group (top)
Anthocyrtella kruegeri (Popofsky) 15-1
atyp (top)
Cannartus laticonus Riedel from 15-6
is present to 15-1
Desmospyris haysi n. sp. (top) atyp 3-2 16-4
Botryostrobus euporus (Ehr.) florished 15-5 1,CC
Lithamphora corbula (Harting) 15-4
spp. group gave rise to
L. furcaspiculata Popofsky
Lithocampe punctata (Stohr) (top) 1-4 1033 cm 115 cm
Theocorys longithorax n. sp. (top) 11-2 16-4
Lithocampe (Cyrtocapsella) compacta 11-2 17-2
(Haeckel) (top)
L. (Cyrtocapsella) cylindroides 8,CC 18-3 1074
(Principi) (top)
Artostrobus pretabulatus n. sp. (top) 18-3 no45
Artocyrtis punctatus (Ehr.) typ from 20-3
is present to 19-2 o
A. punctatus forma E from 11, CC
Zh is present to 11-2 N
Clathrocyclas bicornis Hays (bottom) 20-4
Stichopodium biconicum (Vinassa) gr. 9,CC 20-4
(bottom)
Lithelius nautiloides Forma P (top) 4.CC 20-6 115
Gondvanaria dogeli Petrush (bottom) 20-6
Clathrocyclas titanothericeraos 21-6
Campbell and Clark (bottom)
Amphymenium ? spledriarmatum above 2-2 21-6
Clark and Campbell atyp (top)
Desmospyris spongiosa Hays (bottom) 21-6
D. haysi n. sp. (bottom) 6,CC 22-1
Lithocampe (Cyrtocapsella) cylindroides Below? 22-1
(Principi) (bottom) 12, CC
Antarctissa strelkovi Petrush. (bottom) 22-3
2
H
>
5
n
-P> s
00
TABLE 1 - Continued p
S
DSDP Leg 29 Eltanin Ob
14-8 H
Zone No Radiolarian Events 28OA 281 278 280 13-17 256 268 d
on
y< Phorticium clevei (Jorgensen) (bottom) 23-3 WX
<^2 Theocotyle robusta (Clark and 24-2 CO
Z \^ Campbell) (top)
/ Desmospyris rhodospyroides n. sp. (bottom) 25-4
/ Lychnocanella conica (Clark and 25-4
α3 Campbell) (top)
\. Stylodictya targaeformis (Clark and 16-1 26-1
\ Campbell) (top)
/ Eucyrtidium sp. m is present from 6,CC from 16-3 from 26-4 1,CC
to 1, CC to 3-5 to 21-3
\! Botryopera triloba Ehrenberg group, 26-4
\ (bottom)
yS Saccospyris preantarctica n. sp. (bottom) 27-3
<25 Ommatogramma dumitrikae n. sp. from 29-4
N. is present to 27-3
<^f^~ The cosphaeralla ? ptomatus from 28-6
I ^ \^ Sanfilippo and Riedel is present to 25-6
/ Gondvanaria japonica (Nakaseko) 29-4
/Cj group (bottom)
\. Lithocampe (Cyrtocapsella) compacta 29-6
\^ (Haeckel) group (bottom)
/ Clathrocyclas humerus n. sp. (bottom) 30-1
/ Botryopyle dionisii n. sp. (bottom) 30-1
Xg Cenosphaera megachile Clark and from 32-4
\ Campbell is present to 30-2
\ Amphisphaera radiosa (Ehrenberg) 4,CC from 31-2
\ is present to 30-1
/ Botryocella appeninnica ? Vinassa 12-2 from 32-5
/ is present to 31-2
/ Perichlamidium limbatum Ehrenberg from6,CC 31-2
/ is present to 4-4
(29 Botryometra spongiosa n. sp. 6,CC 16-3 31-2
\ is present
1^ \ Actinomma medusa (Ehr.) group 14, CC from 33-6
\ is present to 31-2
\ Artostrobus pretabulatus n. sp. (bottom) 31-2
/ Cenosphaera cristata Form A 1-4 16-6 from 32-4
/ is present to 28-4
/ Stylodictya stellata Bailey group (bottom) 32-1
AQ Lithomitra arachnea (Ehr.) (bottom) 32-1
\ Spongodiscus resurgens osculosa 32-4
| \ (Dreyer) (bottom)
g \ Lychnocanella conica (Clark and 32-6
•& L \ Campbell) (bottom ?)
a; / Theocoryslongithorax n. sp. (bottom) 1,CC 11-5 33-2
/ Artostrobus annulatus (Bailey) (bottom) 33-1
A j Ommatodiscus haeckeli Stohr (bottom) 13-6 33-5
+n
\ Lithocarpium polyacantha (Clark and ? 1,CC 14-4 33-5
\ Campbell) (bottom)
\ Lithelius ? nautiloides Form P (bottom) ?atyp 33-2
\ 6,CC
1
/ Artostrobus pusillum (Ehrenberg) (top) above 4, CC 31-1*
/ Cladoscenium? advena (Clark and from 33-2
/ Campbell) is present to 32-3
/ Lithelius ? foremanae Sanfilippo and 1-4 above 16-3 32-4 atyp
/ Riedel (top)
/ Pylospira sp. A 14-3 from 33-6
/ is present to 32-6
/ Lithelius sp. E from 16, CC 33-1
/ is present to 14-1
/ Theocampe elizabetae (Clark and 33-1
/ Campbell) is present (top?)
i32+n Cenosphaera? oceanica Campbell and from 6, CC from 16-3 32-5
1 \ Clark is present to l.CC to 14-2
\ Diplocydas sp. A from 6-2 33-2
\ is present to 2-2
\ Theocampe minuta (Clark and ? above 33-2
\ Campbell) (top) 4,CC
\ Lithomitra eruca from 6-2 33-6
\ is present to 4, CC
<u \ Stylodictya rosella Kozlova, (top) 14-2
S \ Thyrsocyrtis sp. (top) 14-3
o \ Axopmnum liostylum (Ehrenberg) (top) 2,CC 14-2
\ Litheliusihexaxyphophoms (Clark and from6,CC from 16-3 32-5
u
"« \ Campbell) is present to 4, CC to 14, CC
/ Stylodictya targaeformis (Clark and from 16-2
/ Campbell) is present to 15, CC
/ Botryocella sp. K from 16, CC
/ is present to 15-2
/ Calocyclas ? semipolita Clark and 5-2 15-1
(33+n Campbell (top)
\ Calocyclas ? fragilis (Carnevale) (top) 5-2 above 14, CC
\ Lithomelissa sp. aff.
\ L. haeckeli Butschli (top) 5 2 15-1
\ Spongodiscus craticulatus Below 16, CC 27-6
2 \ (Stohr) (bottom) 4, CC
/ Corythomelissa sp. aff. Spongomelissa 4,CC 16-1 from 33-2
/ adunca Sanfilippo and Riedel to 21-2
/ is present
o4+n Lithocarpium monikae n. sp. from 6-2
\ is present to 2-2
n
\ Porodiscuslbergontianus Carnevale from6,CC
\ is present to 4, CC w
/ Xiphospyra ocellata (Ehr. is present 6,CC o
/ Botryostrobus joides n. sp. (bottom ?) 6,CC 16, CC ?21-3
N
/ Lithomelissa sp. aff. 6,CC 16, CC o
/ , L. haeckeli Butschli (bottom)
+ o
\ Axopmnum liostylum (Ehrenberg) Below 16, CC se
\ (bottom) 6-2 >
\ Lithocampana sp. aff. L. lithoconella from 6,CC 16-2 δ
\ Clark and Campbell is present to 1,CC
/ Ceratocyrtis sp. aff 7-2 >
<36+n ^*# cucu^ar's (Ehrenberg) is present 1—1
\^ Lithomitra sp. B from 7-2 >z
\ is present to5,CC
/ Stylodictya rosella Kozlova, bottom 16, CC CΛ
O
g / Calocyclas']fragilis (Carnevale) (bottom) 8-1
g <37+n Calocy clast semipolita Clark and Campbell 8-1 16, CC TI
(2 \ (bottom)
\^ Artostrobus pusillum (Ehrenberg) (bottom ?) 8-1 33-2
/ Amphimenium ? spledriarmatum Clark 10-5
? / and Campbell typ. (bottom)
/ Spongothrochus cruciferus Clark and 10-5
\ Campbell is present
\ Theflcampe minuta (Clark and 10-5 34-1
\ Campbell) (bottom)
M. G. PETRUSHEVSKAYA
tus penultimus, O. antepenultimus, Cannartus petterssoni no species has been discovered which existed only in the
and C. laticonus) in the tropics. last 400,000 yr (approximate age of the first horizon), in
Conversely, the sediments of the lower Miocene (the spite of the fact that the sediments of this age were quite
accumulation of which took twice as much time) the adequately studied.
changes of the radiolarian fauna the Antarctic are less Within the range of Quaternary Antarctic deposits,
sharply expressed and less frequent. Apparently, this Hays additionally isolated the Zones ^ and x It is
corresponds to one "radiolarian zone" with Calocyclet- Hays' opinion that the boundary between these zones is
ta virginis (or, more precisely, C. veneris?) and, partly to characterized by the disappearance of Saturnalis cir-
the zones with Calocycletta costata and Lychnocanium cularis (which occurs lower) and Pterocanium trilobum
bipes. More ancient Eocene deposits are probably easier (the content of which according to Hays is not always
to correlate. completely clear). However, as has been shown by
Since the number of sections studied in the Antarctic Petrushevskaya (1971c) and Petrushevskaya and Lin-
is rather small, it is difficult to decide how synchronous jkova (1972), these species gradually narrowed their area
the established periods of change of the radiolarian of distribution and the area where they ceased to exist
fauna are, and in what geographical ranges they oc- just 600,000 yr ago is rather narrow (Figure 5).
curred. Thus the author refrains from establishing such Therefore, the zonal boundary (^/x = 600,000 yr) can
"radiolarian zones" which are customarily used in the be defined only in very few Antarctic (more accurately,
reports of the Deep Sea Drilling Project. subantarctic) cores. The present author refrained from
Table 1 contains a list of events in the development of isolating Zones ^ and x in the Antarctic sediments, but
the radiolarian fauna which were noticed in the samples instead suggested (Petrushevskaya, 1972a) Horizons II
studied. Those events which seem to be synchronous are and III, which are divided by the second event (see
united under a single number. In essence, each number above). The second event is characterized by the extinc-
shows the substantiation of the boundary of a certain tion of several rather reliable species.
stratigraphic horizon; however, the significance of the
individual boundaries is unequal. The most distinctly Zone B
outlined horizons and their specific peculiarities are In the tropics, the Quaternary sediments are underlain
isolated as tentative zones and marked by letters. Table by the "zone with Pterocanium prismatium.'"The lower
2 compares those zones and events with the stratigraphy boundary is characterized by the disappearance of
of the DSDP Leg 29, Ob, and Eltanin sites. Spongaster pentas and Stichocorys peregrinus as well as
by an increase in the number of Pterocanium pris-
Zone A
matium.
The sediments, the age of which is considered as less In the deposits of the higher southern latitudes a zone
than 1.7-1.8 m.y. (Riedel et al., 1963; Hays et al., 1969; is distinguishable which can be correlated with the zone
Riedel and Sanfilippo, 1970) are considered Quaternary. with Pterocanium prismatium. The upper boundary of
In tropical areas (40°N to 40°S) the lower boundary of this Pliocene Antarctic zone is characterized by the dis-
these sediments is marked, according to the data of these appearance of Clathrocyclas bicomis Hays (which is
authors, by the disappearance of Pterocanium quite numerous in the lower boundary), and by the fre-
prismatium. It is also noteworthy that the skeletons of quently almost synchronous disappearance of
Pterocorys campanula disappear here and the typical Stichopodium biconicum (usually mentioned as Eucyr-
Pterocorys hertwigii appear. tidium calvertense). In other words, the upper boundary
In the 1.7 m.y. old sediments of 50°S-60°S lat, the oc- of this zone is the boundary established by Hays (1965)
currence of Clathrocyclas bicomis Hays becomes discon- for the Zones x/Φ The lower boundary of Zone B could
tinuous, whereas Saccospyris antarctica, Diplocyclas be determined by the last occurrence of Prunopyle titan.
davisiana and Spongurus? pylomaticus (Petrushevskaya, Bandy et al. (1971) state that it is just this moment that
71973, and present article) become more numerous. marks the boundary between the Miocene and Pliocene
Species common to the sediments of both high and low of the Antarctic. However, P. titan has obviously been
latitudes (the time-range of which would be confined to identified erroneously; the species referred to in this
a specific period) could not be discovered. paper as Lithocarpium titan has never been encountered
In the Quaternary deposits, there was success in deter- in the high latitude deposits, although Larcoidea (e.g.,
mining in the tropics (Nigrini, 1971; Petrushevskaya, the extinct Pylospira sp. L) are rather numerous. Such
71972), as well as in high latitudes, three or even four events in the history of Larcoidea as the transition of
stratigraphic horizons, characterized by various sets of Ommatodiscus haeckeli into an atypical form, and the
Tertiary species about to become extinct. The complete disappearance of Lithocarpium polyacantha,
radiolarian complexes in the uppermost of these are confined to the lower boundary of Zone B. Ap-
horizons differ only slightly from the distribution of parently, just these changes of the fauna were described
radiolarians in the surface layer of the Recent bottom as the extinction of L. titan. Lychnocanium grande and
sediments. The latter have been studied rather accurate- Androcyclas heteroporus usually also do not enter the
ly. In the Antarctic deposits, such an uppermost horizon zone, instead they occur (rather irregularly) below this
was marked by Hays (1965) as Zone ü, whereas zone. Desmospyris spongiosa and Pseudocubus vema
Petrushevskaya (71972) marked it as Horizon I. Its isola- might occur in the lower part of Zone B. On the whole,
tion into an independent zone is hardly justified, since the lower boundary of Zone B (= Event 5) completely
550