Dumitrica 1973a

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23. PHAEODARIAN RADIOARIA IN SOUTHWEST PACIFIC SEDIMENTS CORED D URINGLEG 21 OF THE DEEP SEA DRILLING PROJECT

Paulian Du mitrica, Geological Institute, Bucharest, Romania

INTRODUCTION

Although occurrences of phaeodarian remains in a fossilor subfossil state have been recorded long ago by Bailey(1856), Wallich (186 9), Borgert (19 01), and Cocco (1903),the discovery of most fossil phaeodarians isincontestablyan achievement of micropaleontological researches of thelast few years. As a consequence of these researches, a seriesof well-preserved phaeodarian shells have been found in thelast decade in Recent and Pleistocene sediments (Riedel,1963;Reschetnjak, 1969,1971;Stadumand Ling, 1969;Dumitrica, 1972), and in some Middle Miocene deposits(Dumitrica, 1964, 19 65).

It is indeed true that, due to their chemical nature,phaeodarian skeletons are very or extremely rare insediments as compared withpolycystinsor with thephaeodarians in living plankton. However they are muchmore frequent than was previously believed. Our observa-tions on the cores drilled in Leg 21 and on some samplesdrilled in Legs 5 and 7 of the DSDP or coming from variousMiocene deposits, proved that most of them contain usuallyrare fragments of phaeodarian skeletons. It is true that theyare generally indeterminable and that the chances of findingentire shells are rather small. For this reason, the satisfac-tions of such finds are so much the greater. In spite of theirscarcity, the very few species recorded in sediments ofvarious ages give information, quite fragmentary indeed,about some taxa having constituted some fossil phaeodarianassemblages.

The investigations of theradiolarian-bearingsedimentscored in Leg 21 have provided interesting new dataconcerning the resistance forfossilizationof several phaeo-darian groups. The described phaeodarian remains havebeen found associated with polycystine radiolarians,immaterially whether the latter were perfectly preserved inopaline silica or in probably finely crystallized silica. Forexample, in the Upper Miocene at Site 205 and the UpperMiocene and Pliocene sediments at Site 206 the initiallyopaline silica of the polycystins appears to be crystallized,the skeletons being of milky white color in air and ratherdark in Canada balsam. In spite of this alteration of the

structure of the silica, phaeodarian remains are not lacking.On the contrary, it is just within these intervals where themost and best preserved phaeodarians occur. They arepractically absent only in the Lower Miocene and Oligocenesediments, where some polycystine tests are partlycorroded.

The coring of an almost continuous radiolarian sequencefrom Oligocene to Quaternary enabled us to follow theoccurrence of phaeodarian remains within a long period oftime. The result is that the range of some living taxa wasthus extended to various levels of the Quaternary, Pliocene,

or Miocene. A few species probably extinct or, at any still undescribed, were also found at some levels of sequence.

Generally speaking, almost all suborders and familiePhaeodaria are represented in the cores studied. The racharts of the skeletal remains ofphaeodariansshow that,besides some species whose occurrence is limited particular stratigraphic levels, probably because of bepossibilities for preservation, there are a few groups remains of which are resistant enough to occur alongwhole sequence. These are especially small shellsofLirella,remains of shells of castanellids, and spines of coedendrids andAtlanticella.

PHAEODARIANS AT EACH SITE

In the SW Pacific sediments cored during Leg 21 ofDeep Sea Drilling Project, phaeodarian skeletons have recorded at the following Sites: 203, 204, 205, and 206

Site 203(lat. 2209 .22'S, long.17732.77'W; water depth 2720 m)

A rather rich phaeodarian fauna occurs associated wpolycystine radiolarians throughout Cores 1 and 2 dribetween 0 and 15 meters below the sea floor. The sedimconsists of iron-oxide-richnannofossilooze with twointercalations of volcanic glass, and is Upper Pleistocen

Holocene in age.In the two intercalations of volcanic glass the phadarians are practically lacking, not because of their distion but because of the dissemination caused by the rsedimentation of the volcanic glass. As a matter of fwithin this interval of 15 meters there is no indicationdissolution of the phaeodarian skeletons with depth. Oncontrary, the richest fauna occurs approximately at middle part of the sequence, where the richest assembof polycystine radiolarians occurs also at this site. Ashown in Figure 1, the most frequent remains of phadarians belong to challengerids{Protocystis, Lithogromial),lirellids(Lirella, Borgertell), castanellids(Castanidium,etc.),medusettids(Euphysett), and coelodendrids (inde-terminable spines).Site 2 04(lat. 24 57.27'S, long. 17406.69'W, water depth 5354 m)

Phaeodarians occur only in the superficial layer Recent sediment(204-1-1,0-2 cm). They disappear rapidlywith depth in sediment so that at 45 cm below the surfthey are practically absent. In the sample cited abophaeodarian remains are rare, being represented by following taxa:Aulographis taumorpha, Aulospathis vari-abilis, Protocystis harstoni, Lirella marina, L. melo,

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P . D U M I T R I C A

Taxa

Aulographis taumorpha

Aulographonium candelabrum

Aulographonium pulvinatum

Aulographonium cf. indicum

Aulocantha ? spp. (spines)

Castanidium ? fenestratum

Castanidium sp.

Castanea ? sp. 1

Castanea ? sp. 2

Porospathis holostoma

Protocystis xiphodon

Protocystis harstoni

Protocystis cf. thomsoni

Lithogramia ? sp. 1

Lithogromia ? sp. 2

Lirella marina

Lirella melo

Borgertella caudata

Medusetta inflata

Euphysetta elegans

Euphysetta lucanii

Euphysetta pusilla

Euphysetta cf. nathorstii

Coelodendrids gen. et sp. ind.

Sample

o

enooJLfoo_?, _ !AEGenus LIRELLA (Ehrenberg)Loeblichand Tappan

Two species,L. marina andL. melo, the most common speciesof this genus, have been recorded in the cores investigated.

Lirellamarina (Bailey)(Plate 6, Figures 6-8; Plate 9, Figure 8; Plate 12 , Figures 10-

Cadium marinum Bailey, Btschli, 1882,pi. 32, fig. 15; Haecker,1908,p. 281,pi . 51 , fig. 416; Reschetnjak, 1966, p. 174, fig106.Remarks: This species was commonly encountered in th

sediments cored at four sites: 203, 204, 205, and 206 of Leg was almost uninterruptedly recorded not only in the Quaterwhere it had already been found by some previous workers, buin the Pliocene and Upper Miocene at S ite 206.

Two morphological varieties have been recognized: one hthick wall, an unmodified convex outline, and an ornamentconsisting of 10 to 11 thick longitudinal ridges on half a diamthe ridges are continuous from the oral end to the aboral (PlFigures 6, 8; Plate 12, Figure 10). The other variety haspindle-shaped form, a longer peristome, and many more ltudinal ridges(18-22on a semicircle) (Plate 6, Figure7; Plate 9,Figure 8; Plate 12, Figures11, 12). The ridges seem to disappear tothe oral end. It is not clear whether they are simple morpholovarieties or two independent taxa. The longitudinal ridges arsmooth; they are constituted of two rows of alternatingtubercules(see Plate6, Figure6, a scanning electron micrograph taken by J. P

Caulet in the Geological Laboratory of the National Natural HMuseum in Paris.Lirella m elo (Cleve)

(Plate 7, Figures3,4; Plate 12, Figure 9)Cadium melo (Cleve),Jrgensen,1905, p. 142,pi . 18, fig. 13;

Haecker, 1908, p. 282,pi.51 , fig. 415 ; Schroder, 1913, p. 168,text-fig. 10; Stadum and Ling, 1969, p. 484,pi . 1, figs. 6-8;Reschetnjak,1971,fig. 11 .Remarks: Presence of this species in Recent and Pleistocen

sediments has already been recorded by Reschetnjak (1969,1Stadum and Ling (1969) , and Dumitrica (1972). In the SW Pawas encountered in Quaternary, Pliocene, and Late Miocsediments. It is much m ore rare thanL. marina.

Genus BORGERTELLA new genusType species:Cadiumcaudatum Wallich.

Diagnosis: Shell constituted of two main parts: an egg-shapechamber closed at the aboral end and armed with a hollow sand a long, more or less curved, trumpet-like peristome. The cavities of the two parts are separated by a diaphragm communicate only through a narrow tube entering the peristcavity. If the curvature of the peristome is considered as bventral, the tube is situated by the right wall of the shell (PlatFigure 15) and is directed dorsally. Surface smooth or wlongitudinal ridges.

Remarks: Borgertella is proposed forCadium caudatumWallich,C. nauris Borgert, and the new species,Borgertella erectostoma. Itdiffers fromLirella in having the diaphragm mentioned. Apparentlprevious authors did not observe this peculiar inner tube whiclearly visible in ahnost all species observed both in Quaternarin Upper M iocene sediments.

Borgertella caudata (Wallich)(Plate 8, Figures 6-8; Plate 12, Figures13-17)

Cadium caudatum Wallich, Btschli, 1882 ,pi .32, fig. 15a.Cadium inauris Borgert, 1910, p. 402 ,pi .30, figs. 4-10.

Remarks: Mosts pe c i m e n s fit the description given by Borgertfor C. inauris, except for the arch connecting the oral spine with taboral one. It is broken in the fossil material, the spines bpreserved only by their proximal parts. In the specimens resemB, caudata no oral spine was observed. As, except for the oral spthe shells of the two species are quite similar, they appear tsynonymous. Borgert (1910) himself recognized that they difficult to separate.Borgerfsdescription should be completed withdescription of the diaphragm separating the shell cavity fromperistomalone.The diaphragm is generally perpendicular or slight

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P. DUMITRIC

oblique to the axis of the shell chamber. The diaphragmatic tube isshort and directed slightly dorsally.

D. caudata was found in the Quaternary sediments at Sites 203and 206.

Borgertella erectostomanew species(Plate 8, Figures9,10; Plate 12, Figures 18-21)

Description: The first segment oval with the ventral side muchmore inflated than the dorsal. The aboralspm e ln and curvedventrally. The diaphragm between the two cavities is oblique to theaxis of the shell, so that the ventral part of the first segment is muchlonger than the dorsal. In the ventral part the diaphragm is locatedat the constriction between the shell and peristome. The diaphragm-atic tube is long, dorsally directed, and located near the right side ofthe shell. The peristome is generally straight and deviates from thelongitudinal axis at an angle of about 40 to 45. The rim of theperistome is expanded as a trumpet. No oralspine Surface of wholeshell covered with numerous long itudinal ridges.

Dimensions: Length of shell without aboral spine47-52 ,diameter 19-21.

Remarks: Ten specimens have been observed in the UpperMiocene samples205-6-1,80-82 cm; 205-6-5, 70-72 cm; and205-7-3,70-72 cm.

B. erectostoma differs fromB. caudata in its straight peristomeand longer diaphragmatic tub e. Because of its stratigraphic positionit can be considered as the ancestor of the latter.

Family MEDUSETTIDAERemarks: The shells of some medusettids, particularly of

Euphysetta, are well preserved in sediments. Riedel (1963) illus-trated the first medusettid in a Quaternary Pacific sediment.Recently, Reschetnjak (1969, 1971) andStadumand Ling (1969)have recorded three species:Euphysetta elegans, E. amphicodon,andE. nathorstii.

In SW Pacific sediments, shells, or fragments of shell andspm e sof Medusetta, Euphysetta, Atlanticella,and probablyPlanktonettahave been recorded in Q uaternary, Pliocene, and Miocene.

Genus MEDUSETTA HaeckelMedusetta inflata Borgert

(Plate 1 3, Figure 1)Medusetta inflata Borgert, 1906, p. 146, pl. 11, figs. 10, 11;

Haecker, 1 908, p. 30 5, pl. 53, fig. 437 .Remarks: A single brokens pe c m i e n withthe oral pole moder-

ately well preserved was found in Sample203-1-1,81-83cm.

Medusetta ? costata n.sp .(Plate 5, Figures 7,9,10; Plate 13, Figures 2, 3)

Description: Ovoid shell with the aboral end acute and pro-longed into a long spine. The oral end is almost always damaged.One specimen, however, preserves an incomplete oral spine. Thenumber of such spines is not known but, judging by the remainspreserved in thes pe c m i e n mentioned, it seems that there are nomore than four oral spines, which would correspond toEuphysettaor Medusetta. What is most characteristic of this species is thestructure and ornamentation of the shell wall. The surface of theshell is covered on the oral half with 25 to 30 slender longitudinalridges. The wall is clearlybilamellar(see Plate 5, Figure 10) andperforated by minute poresquincunciallyarranged in transverserows, about 8 to 10 pores in the distance between two ridges.

Dimensions: Length of shell without aboral spine90,diameter60.

Remarks: Only three specimens have been found in the UpperMiocene in Samples205-6-1,80-82 cm and 205-6-5, 70-72 cm. Inspite of the small number of specimens and their poor preservation,the species is erected because of its structural characteristics, whichmake it very easily recognizable, and of its age. Apart fromEuphysetta sp. it is the oldest medusettid known at present.

Genus EUPHYSETTA HaeckelEuphysetta elegans Borgert

(Plate 5, Figure 8; Plate 6, Figures1-3; Plate 12 , Figure 8)Euphysetta elegansBorgert, 1906, p.154, pi.11 , figs. 7-9; Haecke

1908,p. 307,pi.53, figs. 435, 438 .Remarks: Shell quite conformable toBorgerfsdescription and

illustration.E. elegansis the most frequent species of this gethe cores studied, particularly at Site 203, where aspecimens have been counted. Its occurrence is limitQuaternary.

Euphysetta sp.(Plate 6, Figures4, 5)Remarks: A single brokenspecimenw a s found in the Uppe

Miocene Sample205-6-1,80-82 cm. Its shape and superfornamentation is similar to that ofE. elegans, E. amphicodon, andE. staurodon.

Euphysetta lucaniBorgert(Plate 9, Figure 1; Plate 12, Figure 6)

Euphysetta lucaniBorgert, Haecker, 1908, p. 306,pi.53, figs. 436 ,439,442.Remarks: Two complete specimens have been found

Pleistocene Sample203-2-1,94-96 cm.Euphysetta pusilla Cleve

(Plate 9, Figure6; Plate12 ,Figure 5)

Euphysetta pusillaCleve, 1900, p. 7,pi.3, fig. 16.Remarks: One specimen of this extremely rare specifound in the small fraction of Sample203-2-1,94-96 cm. It is fairlsimilar to the specimen illustrated and described by ClevNorth Atlantic. The superficial ornamentation consists olongitudinal lines, which seem to disappear toward the The very small alveoli quincuncially disposed in the spalines, mentioned by Cleve, were not observed in this spec

Dimensions: Length of shell without spines 62, diameEuphysetta cf. nathorstii Cleve

(Plate 9, Figure 7; Plate 12 , Figure 7)Euphysetta nathorstiiCleve, Stadum and Ling, 1969, p. 485pi. 1,

fig.5.Remarks: In spite of the lack of the oral spines, whi

brokenoff, there is little doubt as to the specific name of thThe long aboral spine, the fine superficial ornamentatiosimilar size are arguments in favor of this assignmspecimens have been recorded in the small fraction o203-2-1,94-96 cm.

Dimensions: Length of shell without spines63,diameter42.Genus ATLANTICELLA Borgert

Remarks: The primary skeleton ofAtlanticella, reduced to aperistome with long chambered spines, is constituted of or without traces of organic substance (Borgert, 1905, p119).Thisexplains their preservation in sediments.

At Sites 205 and 206 the remainsof Atlanticellaare some of themost resistant phaeodarians. They consist of fragmentsspines and may be very easily recognized by their peculiaAlmost all the fragments recorded are straight and elliptical in cross section, because they are lying in slidsameside-that which displays the alternate disposition comma-shaped chambers. Such adisposition,characteristicto Atlanti-cella, is quite similar to that of the grains in an ear oChambers are evidently open at the acute end, which directed to the distal extremity of the spines. The inseparating the chambers forms a zigzag line whose ampfrequency vary withspm e s M o s t frequently the spines are whthe corners of the zigzag are closer to the longitudinal athe right and left sides. Also, most fragments come from parts of the spines (Plate 9, Figures3-5;Plate 10 , Figures2-5;Plate13,Figures 7, 9), very few from the d istal ends (Plate 10 ,This type of spine was considered asAtlanticella sp. 1. It wasrecorded almost uninterruptedly from Quaternary to Mcene at Site 206, and also in the Upper Miocene at Site205,andHolocene at Site 204.

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The second type , determined asAtlanticella sp 2 (Plate 10,Figures 6 , 8; Plate 1 3, Figures 4-6), is distinguished from the formerby its curved shape. The chambers are also alternately open, but onone side and on another of the plane of curvature, and generallymore or less toward the convex side. These spines are less frequentat Site206.

It is not possible at present to establish whether the two types ofspines come from several species, from tw o species, or from thedifferent kinds ofspines of onespecies Thedifficulty is due to theabsence in the literature of a description of the spine structures ineach species.

GenusPLANKTONETTABorgertPlanktonetta ? sp

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Dumitrica 1973a