MarineMicropaleontology, 21 (1993) 369-383 369 Elsevier Science Publishers B.V., Amsterdam

Biozonation, diagenesis and evolution of radiolarians in the Lower Carboniferous of Germany

Andreas Braun a and Reinhard Schmidt-Effing b alnstitut j~r PaliLontologie der Rheinischen Friedrich-Wilhelms-Universitiit, Nuflallee 8, 5300 Bonn 1, Germany

blnstitut flir Geologie und Paliiontologie der Philipps-Universitiit Marburg, Lahnberge, 3550 Marburg/Lahn, Germany

(Received January 10, 1992; revision accepted October 9, 1992 )

ABSTRACT

Braun, A. and Schmidt-Effing, R., 1993. Biozonation, diagenesis and evolution of radiolarians in the Lower Carboniferous of Germany. In: D. Lazarus and P. De Wever (Editors), Interrad VI. Mar. Micropaleontol., 21: 369-383.

Based on radiolarian faunas recovered from sequences of siliceous shales and dark claystones in the Lower Carbonifer- ous of the Rheinisches Schiefergebirge (Germany), a radiolarian biozonation is proposed. Diagenetic alteration of faunas is documented and the stratigraphic distribution of more resistent taxa is given. For closely spaced samples a gradual shift of morphotype abundance has been found for Albaillella cartalla in the Visean, but no gradual transition between species of Albaillella has been found.

Introduction

Siliceous shales and dark claystones with phosphorite nodules, being widespread in the Lower Carboniferous "Kulm-facies" of Ger- many, have been systematically investigated for radiolarians in the past few years [cf. Table 1 for stratigraphic range and Braun and Gur- sky (1991) for further discussion of occur- rence and lithology]. Won (1983) carded out a detailed taxonomic analysis on well pre- served material but did not supply data on faunal succession and age control.

In addition, we have investigated complete and partial rock sequences to find out more about biostratigraphic distribution of radiolar- Jan species (Braun and Sehmidt-Effing, 1988; Braun, 1990b). The resulting biozonation (Braun, 1990b) is as detailed as Conodont chronology. Conodonts and calcareous fora- minifera occurring in various parts of the se- quence helped to independently date single ra-

diolarian faunas and to correlate different chronologies. However, it still remained un- clear how "quickly" new index species occur in the sequence and whether or not they are connected with older species by transitional forms.

Our biozonation has been based on well pre- served and taxonomically varied faunas which occur at various levels in the section about 5 m apart. However, such well preserved and com- plete faunas are in general rare. More often the assemblages obtained after dissolution of the rock are altered by diagenetic dissolution pro- cesses and contain only skeleton parts and whole skeletons of more resistant taxa. The differences in total preservation state and comparisons of faunas from different parts of one single rock layer clearly indicate, that the differences in composition are exclusively due to diagenetic processes and are not the result of presedimentary dissolution or transport phenomena. In order to develop a strati-

0377-8398/93/$06.00 © 1993 Elsevier Science Publishers B.V. All rights reserved.

370 A. BRAUN AND R. SCHM1DT-EFFING

TABLE 1

Stratigraphic scheme showing different stratigraphic subdiv is ions o f the Early Carboniferous and thei r correla t ion as adopted

in this paper. Modi f ied from Braun and Gursky ( 1991 )

Belgium ~ England 2 North America ~ Goniatites 4 Conodonts 5 Lithostratigraphy ~ Radiolarians

III

V3e

V3b ..~

v 3a

V2

V lb

V la

Warnantian Brigantmn

Asbian

Livian Hoikerian

Arundian Moliniacian

Tn 3 lvorian

Tn2 =

T n l b H a s t a r i a n

I ITntal I

Chadian

Courceyian

Chesterian

Meramecian

Osagean

Kinderhookian

Co L

Goct

Pe b

Pe 7

Pe [$

Pe ct

j{ CoP

G a ct

bilineatus zone

not named

t e x a n u s zone

anchoralb z o n e

O~incus z o n e

iso~cha Upper cmlud~a z o n e

Lower crenulata z o n e

san~,~ zone Upper dapBcata zone

Lower duplicata zone

sulcata zone

Kulm-

G r a u w a e k e &

Kulm-Tonschiefer

Kiesellge Ubergangmchiehten

Helle Kleselschlefer /

Kleselkalke

Schwarze Lydlte

Liegende Alaunschlefer

Albaillella i n a z a r o v i z o n e i

Albaillella rockensis zone

l~ftterd~J'ulala concentrica z o n e

AIbaillella cartalla zone

Eostylodictya rota zone

Albaillella indens/s zone

AIbaillella d e f l a n d ~ i z o n e

A Ibaillella ~ a , a d o x a z o n e

graphic scheme based on such resistant species we followed and documented the change of faunal composition due to differential diagen- esis and established stratigraphic ranges of re- sistant species.

Radiolarian biozonation

Position of samples, locations and species compostion of the best preserved samples on which this zonation is based are given in Fig. 1 and Table 2. For more detailed information see Braun (1990b).

Besides taxa with longer stratigraphic ranges (Entactiniidae with some exceptions, Palaeos- ceniidae) the bilaterally symmetrical radiolar- ians (Ceratoikiscum, Albaillella) have been found to show quick morphologic changes in time during Late Devonian through Permian times. Especially Albaillella is present in suffi- cient numbers of samples throughout the sec-

tion. Therefore, we have decided to establish a "framework" of phylozones based on the first occurrences of succeeding species of Albail- lella. A more detailed subdivision has been possible by inclusion of species belonging to other genera and families. Albaillella also played a major role in previous radiolarian biozonations in the Early Carboniferous. Compared with these zonations our subdivi- sion covers a larger total stratigraphic range (Gourmelon, 1987), is more refined (Hold- sworth and Jones, 1980) and for the first time completely documented within one area (Cheng, 1986).

Radiolarian biozones (Plates 1-111)

Remarks: For correlation of different strati- graphic subdivisions see Table 1. The "cooc- curring species" are commonly found in faunas of the zone under discussion. Their total stra-

BIOZONATION AND EVOLUTION OF RADIOLAR1ANS: GERMANY 371

17

16

10

7 , 9

5 , 6

2 , 3

2 m

. . . . 2z = . . . .

=

= = : = =

; =Z~2

N

N

~ 2 5 5 2

% 4

::72

: i

: T : 5 7

"Hangende Alaunschiefer"

"Kieselige 0bergangsschichten"

"Helle Kieselschiefer"

S "Lydite"

"Liegende Alaunschiefer"

Fig. 1. Schematic presentation of the rock sequence in the Lower Carboniferous of the Rheinisches Schiefergebirge show- ing index-fossil groups cooccuring with radiolarians and numbers of most important radiolarian samples. For age infor- mations of lithologic units compare Table 1 and Braun and Gursky (1991). Numbers refer to sample numbers in Table 2.

372 A. BRAUN AND R. SCHMIDT-EFFING

T A B L E 2

O c c u r r e n c e o f s p e c i e s a n d s a m p l e l o c a l i t i e s . F o r m o r e d e t a i l e d i n f o r m a t i o n o n g e o g r a p h i c s i t u a t i o n see B r a u n ( 1 9 9 0 b )

All~illella canatla A. ddlandrei A. furcata A. sp. n. aft'. fmcata A. indeusis indmsis A. sp. n. aft. indensis A. nazarovi A. ouac, bilaenhs

A. I~a~xa A. roekensis A. spilaoea A. thomasi A. undulata C~ra~kiacum sp. C. avimexpectans C. bergl~m~ C. ~;~erlmmum C . f ~ C. omiero,a C. r~undum C. tmabracuhm~ umbracultma C. d. mnbr~adum A~tr~lactima biaciculata A. di~it~a A. ? miro~a A. multispmosa A. r'~iala A. ~t iosa He l i omnm.? imlyacaatlaaa Belowea variabilis B. vmal~'lis? Callda? C.? hexactinia C. s~qlaesin3~lis

Eatactinia tonispu~ E. sp. n. aft. tortispina E. vario~pina E. vulga~ris vulg~ns

~ ~ , , ,,, 8= g O 0 0 0 " D ' O CO00

r~ ~.1 0 ..,,,4 w v

e e • e e e e •

e @ • o e o

• O O l l ,

ol *

• • •

• O @ O

O 0 • • •

• • O O 0 0

• 'O O @ @ O

• •

O O 0

o o

i l | I 1 [ I l l I l l

tigraphic range, however, has not been estab- lished, and hence individual occurrences can only be taken as indicative of a certain age. They do not form part of the definition of the zone.

Albaillella paradoxa Zone Definition: Range of Albaillella paradoxa

Deflandre 1952 before the first occurrence of A. deflandrei Gourmelon, 1987 (=upper boundary).

B I O Z O N A T I O N A N D E V O L U T I O N O F R A D I O L A R I A N S : G E R M A N Y 373

E.~.

Emactinmplmera? altasulcata E. palimbo/a Meschedea hirmta M. pymmispin~a

T~iaenosp~ra tebes T. sicarius Latentifistula sp. I

L, concen~ca

L. i m ~ L. ~ , - a o ~ i , ~ , a L. na~stae L. tmrg~da L. sp. aft. tt~gida L. sp. n.

Te~Igtegno~ syc. sycamocm~s

Eo~ylod/ctya ro~ E.? cf. eccentrica E.? speculm A. c~llimo~hum A. castuligenan A. dlductum A. eupectum A. fmeum A. lagabnellei A. pulchrum A. dedeli A. eL neddi Cyaisl~eractemtma rurae C. cf. sen~nsis Polyentactinia ranam P. polygoma

P.? sp. n.

Pylemonema ~tiqua P. racheboeufi P. typica

Palaeo~emdim cladophocum Polmf~kyellum cf. pu lchn~

Cubaxoniuura? octaa~slmugiosu~"

- ~ ~ ~ ~ ' ~ - ' i ' = 3 ~ _ ~

oooo :. ~ 0 D fo ~" OD ~r ~r ~r - • : I r ~ 3

~ m o - 4 3 v

Cooccurring species: Entactinia vulgaris Won, 1983, Entactinosphaera palimbola Fore- man, 1963, Triaenosphaera sicarius De- flandre, 1973. Species of Cyrtisphaeractenium Deflandre, 1972, have been present before the first occurrence of A. paradoxa and continue up to at least the Albaillella indensis Zone.

Albaillella deflandrei Zone

Definition: Range of Albaillella deflandrei Gourmelon, 1987, up to the first occurrence of A. indensis Won 1983 ( =upper boundary).

Cooccurring species: Diverse Ceratoikiscum faunas have been found in faunas of this age

374 A. BRAUN AND R. SCHMIDT-EFFING

( Ceratoikiscum avimexpectans Deflandre, 1953, Ceratoikiscum berggreni Gourmelon, 1987, Ceratoikiscum rotundum Braun, 1990). Entactinids with long bladed spines (ex. gr. tortispina Ormiston and Lane, 1976) are for the first time present in larger numbers. Entac- tinosphaera palimbola Foreman, 1963 contin- ues from the Albaillella paradoxa Zone.

Albaillella indensis Zone

Definition: Range of Albaillella indensis Won, 1983, up to the first occurrence of Eos- tylodictya rota (Won, 1983 ).

Cooccurring species: Ceratoikiscum umbra- culum Won, 1983, Cubaxonium? octaedros- pongiosum Won, 1983, Archocyrtium laga- briellei Gourmelon, 1987, and Albaillella n. sp. aft. A. furcata Won, 1983. Palaeoscenidium Deflandre, 1953, is missing.

Eostylodictya rota Zone

( = Upper Albaillella indensis Zone in Braun, 1990b)

Definition: Range of occurrence of Albail- lella indensis besides Eostylodictya rota up to the first occurrence ofAlbaillella cartalla.

Cooccurring species: Several species of Ar- chocyrtium Deflandre, 1972, are present in large numbers, as is Cyrtisphaeractenium rurae Won, 1983. The first representatives of Laten- tifistulidae are known from faunas of this age.

Albaillella cartalla Zone

Definition: Range of Albaillella cartalla Or- miston and Lane, 1976 up to the first occur- rence of Latentifistula concentrica (Riist, 1892).

Cooccurring species: Entactinia tortispina (Ormiston and Lane, 1976 ) and Eostylodictya eccentrica Ormiston and Lane, 1976 are com- mon throughout this zone.

Latentifistula concentrica Zone

( = Upper Albaillella cartalla Zone in Braun, 1990b)

Definition: Range of Albaillella cartalla to- gether with a broad morphologic range of spe- cies of Latentifistula ( Latentifistula turgida Ormiston and Lane, 1976-Latentifistula con- centrica Riist, 1892 ) up to the first occurrence of Albaillella rockensis Cheng, 1986.

Albaillella rockensis Zone

Definition: Range of Albaillella rockensis Cheng, 1986 up to the first occurrence of AI- baillella nazarovi Cheng, 1986.

Cooccurring species: Albaillella spinosa Cheng, 1986, and Ceratoikiscum cancermi- mum (Ormiston and Lane, 1976; the latter continuing from the Upper Albaillella cartalla Zone ).

PLATEI

Common radiolarian species from the Albaillella paradoxa Zone (locality: Marsberg-Giershagen, figs. 6-9) and the Al- baillella deflandrei Zone (locality: Am~Snau, figs. 1-5 ) of the Rheinisches Schiefergebirge, Germany. 1. Entactinia tortispina (Ormiston and Lane, 1976). REM 18. Scale bar = 100/tm. 2. Astroentactinia biaciculata Nazarov, 1975. REM 6. Scale bar = 100 #m. 3. Albaillella deflandrei Gourmelon, 1987. CU 55 (8019 ). Scale bar = 100/~m. 4. Ceratoikiscum avimexpectans Deflandre, 1953. REM 6. Scale bar= 30/tm. 5. Ceratoikiscum berggreni Gourmelon, 1987. REM 6. Scale bar= 30 #m. 6. Albaillella paradoxa Deflandre, 1952. REM 2. Scale bar = 100/tm. 7. Entactinosphaera palimbola Foreman, 1963. REM 2. Scale bar--- 100/~m. 8. Entactinia vulgaris Won, 1983. REM 2. Scale bar= 100 :tm. 9. Triaenosphaera sicarius Deflandre, 1973. REM 2. Scale bar= 100 :tm.

BIOZONATION AND EVOLUTION OF RADIOLARIANS: GERMANY 3 7 5

376 A. BRAUN AND R. SCHMIDT-EFFING

Albaillella nazarovi Zone

Definition: Range ofA. nazarovi Cheng, 1986 up to the first occurrence ofAlbailleUa pennata Holdsworth, 1966.

Remarks: The upper boundary of this zone remains to be established in a continuous se- quence, since material ofAlbaiUelta pennata is only known from the Lower Namurian of Great Britain (Holdsworth, 1966) and not in the Rheinisehes Sehiefergebirge.

MorlpimleOc develolmmt of species within zonetl tuld R c r o ~ ~mul~] ]lM~mM]hwies

Up to now we have not been able to find well preserved faunas in every single layer of the section. Thus despite the faunal differences be- tween samples taken every few meters, little is known about how new index species replace the older ones, whether the morpholosic change is gradual or occurs abruptly, and to which ex- tent succeeding species overlap each other in their stratigraphic ranges (Fig. 2 ).

In one sample we found the older index spe- cies cooeeuring with the younger one (Albail- lella deflandrei besides Albaillella indensis). Both species are morphologically easily distin- guished, and no transitional characters are present. In general, we did not fred a gradual

transition between two succeeding index spe- cies up to now.

We found on the other hand that specimens from early stages of a zone differ slightly from those of later stages. Our example (Fig. 5) shows two specimen of Albaillella indensis Won, 1983 from two different horizons of the AlbailleUa indensis Zone. To investigate whether these morphologic changes within the range of one zone are gradual shifts of charac- ters in allochronous populations, we sampled an interval of about 20 m of siliceous shales, the vertical distance between each sample being about 20 cm. Only about a mean number of 30 stapiae of Albailletla cartalla have been ob- tained from the samples. The schematic rep- resentation of our observations (Fig. 3 ) shows that the number of specimens possessing up to seven apophyses on the stapia increases to- wards younger horizons, whereas specimens with only four apophyses first decrease in number and later totally disappear in the samples.

Age control

The stratigraphic range of the radiolarian- bearing sequence has been known since some decades (Fig. 4). It has been determined pri- marily on the basis of goniatites and cono- donts (cf. Braun and Gursky, 1991, for review

PLATE II

Common radiolarian species from the Albaillella indensis Zone through Albaillella cartalla Zone. A. indensis Zone speci- mens (figs. 8-11 ) come from the Frankenwald, Eostyiodictya rota Zone specimens (figs. I, 4-7) come from Braunau (Kellerwald), A. cartalla Zone specimens ( figs. 2 and 3 ) come from Wallau ( Rheinisehes Schiefmgebirge).

I. Beiowea variabilis Won, 1983. REM 20. Scale bar = 30/~m. 2. Albaillella cartalla Ormiston and Lane, 1976. REM 1. Scale bar = 30/zm. 3. Latentifistula concentrica (Riist, 1892), REM 1. Scale bar= 100#m. 4. bar=Albaillella indensis Won, 1983. REM 8115 9/11. Scale bar= 30/zm. 5. Eostylodictya rota (Won, 1983). REM 8115. Scale bar = 100 #m. 6, 7. Latentifistula?. sp. REM 8115 blI/1. Scale bar= 100/an. 8. Ceratoikiscura umbraculum Won, 1983. REM 10, Scale bar= 30/an. 9. Archocyrtiurn lagabriellei Gourmelon, 1987. REM t0. Scale bar= 30/zm.

10. Cubaxonium?octaedrospongiosum Won, t983. REM 10. Scale bar= 30/~m. 11. Albaillella sp. nov. aft. A. furcata Won, 1983. REM I 0. Scale bar = 30/tm,

BIOZONATION AND EVOLUTION OF RADIOLARIANS: GERMANY 377

378 A. BRAUN AND R. SCHMIDT-EFFING

and discussion). Subsequently, we tried to fix our radiolarian chronology by a further search for mierofossils. Conodonts were obtained by etching siliceous samples with concentrated hydrofluoric acid. The specimen are fluori- tized and brittle but usually well preserved. Beds of allodapie limestones intercalated in the siliceous sequence also yielded conodonts (Bender et al., 1991 ) but more often contain calcareous foraminifera (Braun and Amon, 1991 ). Siliceous shales adjacent to such beds of calcareous sediments often contain abun- dant calcified radiolarians. As described mainly for clayey limestones (Pessngno, 1977) radiolarians can be extracted by chemical transformation into fluorite if the rock sample is treated with concentrated hydrofluoric acid. This technique is only successful if exclusively the original skeleton has been replaced by cal- cite embedded in a matrix of different com- position (siliceous, argillaceous). In samples in which skeletons and internal mould are filled or replaced by calcite, only structureless spher- ical internal moulds are found in the residue.

One bed of allodapic limestone containing radiolarians yielded conodonts from three dif- ferent conodont zones. The cooccuring radi- olarian fauna does not contain index species occuring in the two older conodont zones (Bender et al., 1991 ). Seemingly there has been reworking to some extent, which apparently

only effected the conodonts. Redeposition of skeletons within clasts of siliceous rocks being highly resistant to weathering is commonly ob- served in breccias and conglomerates. We have also found reworked phosphorite nodules con- taining well preserved radiolarians embedded in a limestone matrix of different age.

Diagenetic influences

During diagenesis, radiolarian skeletons are subjected to selective dissolution, successive stages of opal-quartz transformation and var- ious replacements. Replacing minerals may be hematite, pyrite, organic substance (Braun, 1990 ), dolomite (Holdsworth, 1966), calcite (Pessagno, 1977) and chlorite (Dehmer et al., 1989 ). Such processes of recrystallisation and transformation influence the taxonomic com- position of radiolarian faunas, and many of them lead to coarsely crystalline undetermin- able aggregates. Sufficient morphological de- tails for close determinations have been found in skeletons replaced by pyrite (Braun, 1990 ), calcite (Braun and Amon, 1991 ), dolomite (Holdsworth, 1977; Braun, 1990) and organic substance. Preservation of details in pyritized skeletons ranges from fine to almost non exis- tent (of. entactinids replaced by large pyrite crystals; Plate III, 5). Amorphous organic sub- stance, recently found to replace radiolarian

PLATE IlI

Examples of dkfferent preservation stages of skeletons and residues (figs. 1-5 ) and important Albaillella species from the A. rockensis and A. nazarovi Zones (figs. 6-8). All specimens from the Rheinisches Sehiefergebirge, Germany. 1. Polyentactinia potygonia Foreman, 1963, a species highly susceptible to diagenetic solution and present only in well

preserved samples. REM 8078 10/37. Eostylodictya rota Zone, Frankenwald. Scale bar= 30/~m. 2. Residue from siliceous shales of the Latentifistula concentrica Zone of Wallau. Only the more resistant skeletons of E.

variospina and sponge spicules are left after diagenetic alteration. Scale bar = 100 #m. 3, 4. Entaetinid skeletons replaced by large crystals of pyrite. Upper Vis6an, Wuppertal-Aprath. Scale bar= 30/~m. 5. SEM detail of entaetinid pore-frames, replaced by amorphous organic substance and showing their original shape.

Upper Visean, Wuppertal-Aprath. Scale bar= 3 #m. 6. Albaillella rockensis Cheng, 1986. REM Go-alpha 3/1. Scale bar= 30/tm. Albailletla rockensis Zone of Wuppertal-

Aprath. 7. Albaillella spinosa Cheng, 1986. REM Go-alpha 3/1. Scale bar = 30 ltm. A. rockensis Zone of Wuppertal-Aprath. 8. A lbaillella nazaroviCheng, 1986. REM Go-gamma. Scale bar = 30 #m. A. nazarovi Zone of Wuppertal-Aprath.

BIOZONATION AND EVOLUTION OF RADIOLARIANS: GERMANY 379

380

• ~: N U

A. BRAUN AND R. SCHMIDT-EFFING

younger lo. Latentifistula concentrica zone) s.

. o ,

Fig. 2. Presence of groups at family level depending on preservation state of the sample residue in phosphorite nodules from one horizon. With progressive crystal size of the replacing mineral Latentifistulids and Entactinida successively disappear from the sample residues.

10"

5"

older (A. cartalla zone)

g,) 1o c--

E s ID

0

E Z

4 5 6 7

Number of apophyses on stapia

Fig. 3. Schematic presentation of changing abundances with time of morphotypes of Albaillella cartalla possess- ins 4 to 7 apophyses on the stapia. Section investigated: Wallau near Biedenkopf (Albaillella cartalla Zone and Latentifistula concentrica Zone), Germany.

skeletons from Upper Visean phosphorite nodules of Wuppertal-Aprath (Germany) even preserves such details like the shape of the lattice bars, tiny projections of spines or deli- cate wall structures (Plate III, 5).

Replacement most probably took place at an early diagenetic stage.

Remnants of early diagenetic silica transfor- mation processes are present as small lepis- pheres on the skeletons [cf. Braun (1990a) for Upper Devonian and Braun (1990b) for

BIOZONATION AND EVOLUTION OF RAD1OLARIANS: GERMANY 3 81

Albaillella rockensis zone

_<.

--s

Latentif istula concentrica zone

Albaillella cartalla zone

Eostylodictya rota zone

-N 0

3

Albaillella indensis zone

Albaillella deflandrei zone

Albaillella paradoxa zone

Fig. 4. Stratigraphic distribution of radiolarians resistent against diagenetic solution and recrystalization. Figured species and genera from left to right: Different parts of Albaillella skeleton, Eostylodictya, Latentifistula impella, Latentifistula concentrica, Entactinia variospina, Entactinia tortispina, entactinids with lateral apophyses on spines.

Lower Carboniferous radiolarians ]. Selective diagenetic dissolution of more del-

icate skeletons (Polyentactinia polygonia Fo- reman, 1963, spicular radiolarians) and skele- ton parts (caveae or stapiae of different species of Albaillella, internal structures of entactinid skeletons) in rocks of slightly different silica and clay content is commonly observed. The residue of samples more strongly influenced by diagenetic dissolution consists only of coarse radiolarian skeletons and sponge spicules (Plate II, 2). Besides progressive transforma- tion and homogenization processes of the sili-

i f =

2 2

\

Fig. 5. Different morphotypes ofAlbaillella indensis from the Albaillella indensis Zone (left) and the Eostflodictya rota Zone (fight) of the Rheinisches Schiefergebirge. Numbers indicating characters changed.

382 A . BRAUN A N D R. S C H M I D T - E F F I N G

increasing resistance

i b v

Polyentactinia Palaeoscenidium Pylentonema Entactinia Entactinia sponge polygonia cladophorum Archoeyrtium tortispina variospina spicules

Fig. 6. Resistivity of different radiolarian species and genera against diagenetic processes.

ceous skeletons embedded in a siliceous-argil- laceous rock matrix, mineral replacements lead to selective preservation of faunal constitu- ents. We compared radiolarian faunas from Upper Visean Phosphorite nodules coming from one single layer and found differences in preservation state between different nodules (Fig. 6 ). Skeletons can be preserved as coarsely crystalline pyrite, finely crystalline pyrite or organic substance. Assemblages replaced by organic substance are most completely pre- served whereas whole groups at family level disappear from the record if only pyritized faunas from this layer are considered (Fig. 2 ).

Acknowledgements

The research was supported for one of the authors (A.B.) by grants from the Konrad-Ad- enauer-Stiftung and the Deutsche Forschungs- gemeinschafi. We gratefully acknowledge the

help of K. Fecher (Marburg), G. Oleschinski (Bonn) and E. Wolf (Bonn) for their assis- tance with SEM photography and figures. H.- J. Gursky (Marburg) and D. Walossek (Bonn) made helpful comments on an early version of the paper. We are grateful to M. Caridroit and P. De Wever for their comments and reviews of the manuscript.

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BIOZONATION AND EVOLUTION OF RADIOLARIANS: GERMANY

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