A C T A P A L A E O N T O L O G I C A --

P O L O N I C A - - -- - - -

Vol 26 1 9 8 1 No. 1

COCCOLITHS AND 1NDE:X FORAMINIFERA FROM THE UPPER CRETACEOUS CHALK OF MIELNIK REGION, EASTERN

POLAND

GAZDZICKA E.: Coccoliths and index foraminifera from the Upper Cretaceous chalk of Mielnik region, Eastern Poland. Acta Palaeont. Polonica. 26, 1, 73-83. October 1981.

The abundant but weakly diversifxed calcareous nannoplankton has been stated in the chalk of the Mielnik region. Large forms of massive structure dominate: Kamptnesius magniftcus Deflandre, Broinsonia parca (Stradner), Reinhardtites anthophorus (Deflandre), Lucianoshabdus cayeuri Deflandre. Two biostratigraphic zones: Bsotnsonia parca and Quadsum trifldum have heen distinguished. Fora- minifera were examined in order to make a correlation with the coccolith zones.

K e y w 0 r d s: Coccoliths, foramhitera. Campanian, stratigraphy, Poland.

Eltbieta Gafdzicka, Instytut Geologii Podstawowej. Uniwersytet Warszawskt, Al. Zwirki i Wigltrv 93, 02-089 Warszawa, Poland. Received: September 1980.

INTRODUCTION '

The chalk deposits at Mielnik on the Bug River (Eastern Poland) were the subject of several geological and palaeontological papers. The first petrographic characteristic of those sediments and descriptions of the micro- and macrofossils contained have been given by Sujkowski (1930). Basing on the foraminifer assemblages Bieda (1958) has divided the chalk complex into the Upper Campanian and Lower Maastrichtian. Pozaryski (1960) regarded the hard-ground level as Campanian - Maastrichtian boundary. On the basis of brachiopods Bitner and Pisera (1979) correlated those sediments with the zones 2 and 3 of the chalk in Denmark (the lowermost Maastrichtian) established by Surlyk (1970).

The present analysis of calcareous nannoplankton assemblages has been done aiming at their stratigraphic values. For comparative reason, in addition to the samples from Mielnik two chalk samples from Kornica have been examined, a locality situated 18 km SW of Mielnik. Several species of foraminifera have been determined as well, in order to make a comparison with the coccolith zonation.

The calcareous nannoplankton has been studied under the light mi- croscope and the scanning electron microscope. All the SEM micrographs were taken at the Laboratory of Electronic Microscopy, the Nencki In- stitute of Experimental Biology in Warsaw.

The material studied and SEM micrographs are housed in the Institute of Geology of the Warsaw University. Acknowledgements. - The author thanks Mrs. M. Bitner and Mr A. Pisera for making available for examination the material from the Mielnik sec- tion and for discussion. Thanks are also due to Dr. R. Marcinowski for valuable remarks and information concerning the belemnoids occurring in the Mielnik chalk.

CALCAREOUS NANNOPLANKTON

Abundant and well preserved calcareous nannoplankton occurs com- monly in the chalk at Mielnik (fig. l ) , except for the hard-ground hori- zon. There, the coccoliths are less numerous (both in taxa and individuals) and difficult to separate from the hard rock. Complete lack of nanno- plankton has been stated in the grey marls overlying the chalk complex. Inspite of the coccolith abundance in the chalk, the species diversity is relatively low and ranges from 20 to 30 species in most samples. Other authors (e.g. Verbeek 1977, Manivit 1971, Gartner 1968) stated 40-60 species in different Campanian sediments. Similar number of taxa as that found at Mielnik has been reported from the Maastrichtian chalk in Den- mark (Hakanson, Bromley and Perch-Nielsen, 1974).

The frequency of species in not uniform. In some samples only several species (sometimes dozen or so) occur abundantly while the remaining species are rare. Larger, massive forms dominate: Kanzptnerius nutgnificus Deflandre, Reinhardtites anthophorus (Deflandre), Broinsonia parca (Stradner), Lucianorhabdus cayeuxi Deflandre. Some coccoliths attain enormous size due to the overgrowth of some structural elements (e.g. Prediscosphaera cretacea (Arkhangelsky), Kanzptnerius nzagnificus De- flandre, Tranolithus orionatus (Reinhardt), Micula decussata Vekshina, Tetralithus obscurus Deflandre.

In two samples taken at Kornica altogether 38 coccolith species have been found. This assemblage is more diversified than these at Mielnik and small forms are more abundant: Biscutunz ignotum (G6rka) and the re- presentatives of genera Vekshinella and Zygodiscus. Most of them are present a t Mielnik but there are some different species: Broinsonia bevieri Bukry, B. furtiva Bukry, Corollithion rhombicum (Stradner and Adami- ker), Vekshinella elliptica Gartner, Lithraphidites quadratus Bramlette et Martini.

UPPER CRETACEOUS COCCOLITHS AND FORAMINIFERA

I ~ j ~ ~ l glacif l u v i a l sands and gravels

glauconitic sands with phospha t i c nodules

hard-ground h o r i z o n with phosphatic p i e c e s

1 ~ 4 cherts

Fig. 1. Columnar section of deposits exposed at Mielnik (after Bitner and Pisera 1979; modified), and sampling sites (1-11) for the coccoliths.

A h m u e l l e r e l l a a c t o r a d l a t a A r k h a n g e l s k i e l l a c y m b i f o n n i s

A r k h a n ~ e l s k i e l l a s a e c i l l a t a B i s c u t m c o r r s t a n s l j i s c u t u m i f l o t - B r a a r u d o s p h a e r a b i ,? rL,wi

U r o i n s o n i a p a r c a

B r o i n s o n l a e n o n i s C h i a s t o z y e u s l i t t e - a r i u s C r e t a r h a b d u s c r e n u i a t u s

C r i b r o s p h a e r a ehre11ba:'gi C r i c o l i t h u s s o l i d u v C y l i n d r a l i t h u s s o r r a t u s

.Uodekapodorhabdus n o e i;lr

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Yrediscoept~a!!Pn spinu.,a k r e r I i s c o s p h a e . ^ a 3 t o v e r i Cuadrmn p ~ t l l i c u ~ i i

Relnhar.lLitc; irrltiiop!loruS

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'ret?Pi: ~ I I U B q u : ~ t i r a t I S

I,>. . r i i . m r u s p ~ m c r c l sp.

' I ' r a ~ ~ o i i t h u s c n a n l f r u r u n V c k s h i n c l i a c r u x 'datznsut!.-ia Larni~Rar,

Z J R O ~ ~ S ~ U S 3CantllUt: Z y g o d i s c u s Dussoni . Z y g o d i s c u s d ig lor : "amnurr C ~ r a t o l i t t l o i d e s a c u i n u s k u a d r - m t r i f i d u m H a i n h a r d t i t c r , l e v 1 3 N h ~ m t r o a s t r r c u a p i s ' Jeks t , in . : l la ot:'iata

- - -

S t a g e s

UPPER CRETACEOUS COCCOLITHS A N D FORAMINIFERA 7 7

All the here identified species were described many times in the lite- rature and for this reason only the list is given here (Table 1) as well as the occurrence in the section. The most common species are illustrated on plates 15-21.

STRATIGRAPHIC REMARKS

A typical Campanian assemblage occurs in the lower part of the sec- tion (samples 1-4, fig. 1). It contains Broinsonia parca (Stradner). Cera- tolithoides aculeus (Stradner) is absent here, at least in its typical form concordant with the holotype (Stradner 1961). But some forms were ob- served which were determind by Verbeek (1977) as Ceratolithoides acu- leus type I, I1 and regarded by this author as early evolutionary stages of the species. This part of the section can be determined as the Broinso- nia parca coccolith Zone. According to Thierstein (1976) this biozone em- braces the Lower Campanian. The occurence of Reinhardtites anthophorus (Deflandre) and Arkhangelskiella specillata Vekshina, with the simulta- neous lack of Marthasterites furcatus (Deflandre) points to the upper part of Lower Campanian. The presence of belemnoids Belemnellocamax ma- millatus (Nilsson), Belemnitella mucronata mucronata (Link) and Gonio- teuthis gracilis (Stolley) determined by Prof. D. P. Naidin of the Moscow University (Dr. R. Marcinowski - oral information) points also to the up- permost part of the Lower Campanian.

The following foraminifera species have been found in the part of the section in question: Globotruncana fornicata Plummer, G. arca (Cushman), G. lapparenti Brotzen, G. bulloides Vogler, Heterohelix globulosa (Ehren- berg), Globorotalites michelinianus (Orbigny), Bolivinoides decoratus de- coratus (Jones), Gavelinella clementiana (Orbigny), Stensioina exculpta gracilis Brotzen, Stensioina pommerana Brotzen, Neoflabellina rugosa (Orbigny). (See pl. 22).

Identical assemblage occurs in the sediments regarded as the upper- most Lower Campanian in NW part of the Federal Republic of Germany (Koch 1977) and defined as the Bolivinoides decoratus decoratus Zone which is a counterpart of the cephalopod gracilislmucronata Zone.

Starting from the sample 5 (0,5 m below the hard-ground) there ap- pear in the coccolith assemblage: Ceratolithoides aculeus (Stradner), Quadrum trifidum (Stradner) and Reinhardtites levis Prins and Sissingh. Beside that, no other quantitative nor qualitative changes were noted in the nannoplankton. Broinsonia parca (Stradner) is still very common. Only in the uppermost part of the section (sample 10) there is a notable increase of Arkhangelskiella cymbiformis Vekshina as compared to other compon- ents of the assemblage. Hence the part of the section from about 0,5 m below the hard-ground up to the grey marls inclusively has been defined

78 E. GAZDZICKA

as the Quadrum trijidum coccolith Zone. I t covers an interval between t he first occurrence of Quadrum trifidum (Stradner) and the first occurrence of Lithraphidites quadratus Bramlette et Martini and it comprises the Upper Campanian and lowermost part of the Maastrichtian (Thierstein 1976, Verbeek 1977).

Simultaneous appearance of Ceratolithoides aculeus and Quadrum tri- fidum in the Mielnik chalk does not allow to separate two different biozo- nes here, as it has been done by many authors. Nor is it possible to distin- guish the Ceratolithoides (= Tetralithus) aculeus Zone (Cepek and Hay, 1969 emend. Martini, 1976) as an interval between the first appearance of Ceratolithoides aculeus and the first appearance of Quadrum gothicum (Deflandre) because the latter species occurs in the section in question earlier than the former. Analogous situation has been observed by Barrier (1980) in the Upper Cretaceous in Texas.

According to Salaj and Gagparikova (1979) the lower boundary of the Quadrum (= Tetralithus) trifidum Zone corresponds to that of Campa- nian - Maastrichtian. I n the section considered this cannot be accepted because Quadrum trifidum appears there below the hard-ground just above the sediments containing a nannoplankton assemblage characteristic of the Lower Campanian. Thus the Upper Campanian age has been accep- ted here after Thierstein (1976).

Reinhardtites levis Prins and Sissingh stated only in samples 5, 8, 9, is limited to the Uppermost Campanian - Lower Maastrichtian interval (Sissingh 1977, Perch-Nielsen 1979).

No changes occur in the coccolith assemblage above the hard-ground as compared to this derived from samples taken just below that horizon. Thus, basing only on the calcareous nannoplankton, it is impossible to find out whether these sediments represent the Upper Campanian or Lower Maastrichtian. Taking for granted Pozaryski's (1960) point of view, accor- ding to which there is a sedimentary hiatus in the hard-ground horizon, it can be accepted that the sediments lying just above that horizon are of the Lower Maastrichtian age.

Appearance of some new coccolith species just below the hard-ground is accompanied by changes in the foraminifera composition; the following foraminifera appear: Neoflabellina numismalis (Wedekind), N. buticula (Hiltermann), Bolivina incrassata incrassata (Reiss) and rare Bolivinoides draco miliaris Hiltermann and Koch. Among the planktic foraminifera, the quantity of representatives of Globotruncana rapidly decreases but Heterohelix globulosa (Ehrenberg), Globigerina cretacea (Orbigny) and Globigerinelloides asper (Ehrenberg) dominate. The presence of the above species points to the Upper Campanian age (Koch 1977).

Above the hard-ground, there appear more stratigraphically younger forms. In samples 7, 8, 9 the following foraminifera has been stated: Globigerinelloid~es asper (Ehrenberg), Heterohelix striata (Ehrenberg),

UPPER CRETACEOUS COCCOLITHS AND FORAMINIFERA 79

Bolzvina decuwens (Ehrenberg), B. incrassata incrassata (Reiss), Bolivinoi- des draco miliaris Hiltermann et Koch, B. delicatulus regularis (Reiss), Stensioina pommerana Brotzen and in sample 10 (grey marls): Neoflabel- lzna preretzculata Hiltermann, Bolivina incrassata crassa Vasilenko et Myatliuk. (See pl. 22).

Most of the above mentioned species are known both from the Upper Campanian and from the Lower Maastrichtian. Only Heterohelix striata (Ehrenberg) is known entirely from the Lower Maastrichtian (Masters 1980).

In two samples of the chalk from Kornica, only the calcareous nanno- plankton has been studied. In both, the presence of Lithraphidites quadra- tus Bramlette et Martini has been stated on the basis of which the age of these sediments can be defined as the higher part of the Lower Maast- richtian or the Middle Maastrichtian (Manivit 1971, Thierstein 1976, Ver- beek 1977, Gazdzicka 1978). Hence these sediments are younger than those cropping out at Mielnik. There are also the Upper Campanian and Lower- most Maastrichtian sediments in the Kornica area (Alexandrowicz 1965) which, however, were not accessible in the outcrop from which derives the material studied by the present author.

FINAL REMARKS

The calcareous nannoplankton assemblages which occur in the Mielnik chalk are typical for the Upper Cretaceous epicontinental seas of the bo- real province (Thierstein 1976). Mass occurence of coccoliths points to exceptionally favourable physico-chemical conditions for the phytoplank- ton (abundance of light, CO,, P, N). The abundance of nannoplankton is associated here with that of foraminifera and predominance of the filter feeders among the macrofossils (Bitner and Pisera 1979). A definite pre- valence of benthic foraminifera over the planktic ones (the latter make about 25 per cent of the assemblage in the Kornica chalk: Alexandrowicz 1965) suggests a depth of the basin of about 100 meters. There are, howe- ver, some horizons at Mielnik in which the quantity of planktic foramini- fera increases greatly. This phenomenon suggests periodical coming of currents from the open sea that brought the planktic forms rather than changes in bathymetry.

REFERENCES

ALEXANDROWICZ, S. W. 1965. Stratygrafia mikropaleontologiczna warstw granicz- nych kampanu i mastrychtu w Kornicy kolo Bialej Podlaskiej. - Sc. Bull. Acad. Mining Metal. Cracow, 81, 6, 5-28.

BARRIER, J. 1980. A revision of the stratigraphic distribution oY some Cretaceous coccoliths in Texas. - J. Paleontol., 54, 2, 289-308.

80 E. CAZDZICKA

BIEDA, E. 1958. Otwornice przewodnie i wiek kredy piszqcej Mielnika. - Btul. Inst. Geol., 121, 3, 11-49.

BITNER, M. A. and PISERA, A. 1979. Brachiopods from the Upper Cretaceous chalk of Mielnik (Eastern Poland).-Acta Geol. Polonica, 29, 1, 67-88.

CEPEK, P. and HAY, W. W. 1969. Calcareous nannoplankton biostratigraphic sub- division of the Upper Cretaceous. - Trans. Gulf Coast Assoc. Geol. Soc., 19, 323- 336.

GARTNER, S. 1968. Coccoliths and related calcareous nannofossils from Upper Cre- taceous deposits of Texas and Arkansas. - Univ. Kansas Paleont. Contr., 48, 1, 1-56.

GAZDZICKA, E. 1978. Calcareous nannoplankton from the uppermost Cretaceous and Paleogene deposits of the Lublin Upland. - Acta Geol. Polonica, 28, ,3, 336-375.

HAKANSSON, E., BROMLEY, R. and PERCH-NIELSEN, K. 1974. Maastrichtian chalk of north-west Europe-a pelagic shelf sediment. In: K. J. Hsu and H. C. Jenkyns (eds), Pelagic Sediments: on Iand and under the sea. - Intern. Assoc. Sediment., Spec. Publ., 1, 211-233.

KOCH, W. 1977. Biostratigraphie in der Oberkreide und Taxonomie von Foraminife- ren.- Geol. Jb., A, 38, 11-123.

MANIVIT, H. 1971. Nannofossiles calcaires du Crktaci: Franqais (Aptien - Maestrich- tien). Essai de Biozonation appuyee sur les Stratotypes. These, Faculte des Science d'Orsay, Universite de Paris, 1-187.

MARTINI, E. 1976. Cretaceous to recent calcareous nannoplankton from the central Pacific Ocean. In: S. 0 . Schlanger, E. D. Jackson et a1.- Init. Rep. DSDP, 33, 383-423.

MASTERS, B. A. 1980. Reevaluation of selected types of Ehrenberg's Cretaceous planktonic foraminifers. - Ecl. geol. Helvetiae, 73, 1, 95--107.

PERCI-I-NIELSEN, K. 1979. Calcareous nannofossils from the Cretaceous between the North Sea and the Mediterranean. In: Aspekte der Kreide Europas. IUGS Series A, 6, 223-272.

POZARYSKI, W. 1960. Zjawisko twardego dna w profilu kredy Mie1nika.-Kwarf. Geol., 4 , 1, 105-112.

SALAJ, J. and GASPARIKOVA, V. 1979. Microbiostratigraphy of the Upper Creta- ceous of the West Carpathians based on foraminifers and nannofossils and the question of relations and migrations of Boreal and Tethyan elements. In: Aspekte der Kreide Europas. IUGS Series A, 6, 279-292.

SISSINGH, W. 1977. Biostratigraphy of Cretaceous calcareous nannoplankton. - Genl Mijnbouw, 56, 1, 37-65.

STRADNER, 11. 1961. Vorkomen von Nannofossilien im Mesozoikum und Alttertiar. - Erd. Zt., 3, 77-88.

SUJROWSKI, Z. 1931. Petrografia kredy Polski. Kreda z glebokiego wiercenia w Lubliliie w porownaniu z kredq niekthych innych obszar6w Polski.-Spraw. Pc.1 Inst. Geol., 6, 3, 485-628.

SURLYX, F. 1970. Die Stratigraphie des Maastricht von Danemark und Norddeut- chland aufgrund yon Brachiopoden. - Newsl. Stratigr., 1, 2, 7-16.

THIERSTEIN, H. R. 1976. Mesozoic calcareous nannoplankton biostratigraphy of marine sediments. -- Mar. Micropaleontol., 1, 4, 325-362.

VERBEEii, .J. W. 1977. Calcareous nannoplankton biostratigraphy of Middle and TJppcr Cretaceous deposits in Tunisia, Southern Spain and France. - Bull. Utrecht Mlc:.op~~ieontol., 16, 1-157.

UPPER CRETACEOUS COCCOLITHS A N D FORAMINIFERA

ELZBIETA GAZDZICKA

KOKKOLITY I PRZEWODNIE OTWORNICE Z KREDY PISZACEJ MIELNIKA NAD BUGIEM

Przedmiotem pracy jest analiza zespol6w nannoplanktonu wapiennego z osadow

kredy piszqcej z Mielnika nad Bugiem. W badanym profilu (fig. 1) kokkolity wy-

stepujq masowo, z wyjqtkiem poziomu twardego dna oraz szarych margli wystepu-

jqcych w stropie kompleksu kredy piszqcej. Zroinicowanie gatunkowe w zespolach

kokkolitow jest stosunkowo male; w poszczeg6lnych prbbach zidentyfikowano od 20

do 30 gatunk6w. Dominujq formy duie, o masywnej budowie: Kamptnerius magnifi-

cus Deflandre, Broinsonia parca (Stradner), Reinhardtites anthophorus (Deflandre),

Lucranorhabdus cayeuxi Deflandre (pls 15-21).

Ansliza skladu zespolow nannoplanktonu wapiennego (tabela 1) pozwolila na

wyr6inienie 2 poziom6w biostratygraficznych: Broinsonia parca (dolny kampan) oraz

Quadrum trifidum (gorny kampan-dolny mastrycht) (por. Thierstein 1976). Dla celbw

porownawczych oznaczono takie niektore gatunki otwornic (pl. 22). W najniiszej czq-

Sci profilu sklad zespolu otwornlc wskazuje na wyiszq czeSC dolnego kampanu-

poziom Bolizjinoides decoratus decoratus (por. Koch 1977), co potwierdza wnioski wy-

ciqgniete na podstawie kokkolitbw. Natomiast obecnoSC gatunku Heterohelix striata

(Ehrenberg) w najwyiszej czeSci profilu sugeruje dolnomastrychcki wiek osadbw.

Potwierdza to sugestie Poiaryskiego (1960) o istnieniu luki stratygraficznej w bada-

nym profilu. W zespolach otwornic zaobserwowano takie zdecydowanq przewagc

form bentonicznych nad planktonicmymi, co Swiadczy o nieduzej glebokoSci zbior-

nika, rzedu 100 m. Osady kredy piszqcej z Kornicy sq mlodsze n i i osady z Mielnika - reprezentujq

wyiszq czeSC dolnego mastrychtu, poziom kokkolitowy Lithraphidites quadratus.

EXPLANATION OF THE PLATES 15-22

All specimens from the chalk of Mielnik

Plate 15

1. Zygodiscus bussoni (Noel), proximal view, electron micrograph M I14 N, X6000. 2. Vekshinella crux (Deflandre and Fert), distal view, electron micrograph M 1111

N, X6000. 3. Ahmuellerella octoradiata (Gorka), distal view, electron micrograph M I16 N,

X5009.

4. Same species, distal view, electron micrograph M I112 N, X6000. 5. Helicolithus anceps (Gorka), distal view, electron micrograph M 115 N, X5000. 6. Rizagodiscus plebeius Perch-Nielsen, proximal view, electron micrograph M 1/8 N,

X 5000. 7. Eiffellithus turriseiffeli (Deflandre), distal view, electron rnicrograph M I17 N,

X5000. 1,3.5-7 Broinsonia parca Zone 3.1 Quadrum trifidunt Zone

Plate 16

1. Zygodiscus acanthus (Reinhardt), distal view, electron micrograph M 113 N, X5000.

2. Tranolithus orionatus (Reinhardt) proximal view, electron micrograph M 11/10 N, X 10 000.

3. Reinhardtites levis Prins and Sissingh, distal view, electron micrograph M I1113 N, X5000.

4. Same species, distal view, electron micrograph M I113 h', X5000. 5. Reinhardtites anthophorus (Deflandre), distal view, electron micrograph M 11111

N, X6000. 1 Broinsonia parca Zone 2-5 Quadrunt trifidum Zone

Plate 17

I . Arkhangelskiella cymbiformis Vekshina, proximal view, electron rnicrograph M 1115 N, X6000.

2. Arkhangelskiella specillata Vekshina, distal view, electron micrograph M 11118 N, X6000.

3. Broinsonia parca (Stradner), proximal view, electron micrograph M 1114 N, X6000 4. Same species, distal view, electron micrograph M 1/14 N, X6000. 5. Same species, distal view, electron micrograph M 1/13 N, X5000. 6. Same species, proximal view, electron micrograph M 11117 N, X6000.

1-3, 6 Quadrum trifidum Zone 4, 5 Broinsonia parca Zone

Plate 18

1. a Kamptnerius magnificus Deflandre, proximal view, electron micrograph M 1/17 N, X5000; b Biscutum constans (Gorka), proximal view.

2. a Kamptne~ius magnificus Deflandre, distal view, electron micrograph M I18 N, X5000; b Watznaueria barnesae (Black), distal view.

3. Kamptnerius magnificus Deflandre, distal view, electron micrograph M I116 Pi, X6000.

4. Central process of Parhabdolithus sp., electron micrograph M 1/22 N, X3000. 1,3.4 BToinsonia parca Zone 3 Quadrum trifidum Zone

Plate 19

1. Prediscosphaera cretacea (Arkhangelsky), distal view, electron micrograph M 1/11 N, X6000.

2. Prediscosphacva stoceri (Perch-Nielsen), distal view, electron micrograph M 1/12 N, X6000.

.3. a Prediscosphaera cretacea (Arkhangelsky), proximal view, electron micrograph M 1/10 N, X6000; b Zygodiscus diplo~rammus (Deflandre), distal view.

U P P E R CRETACEOUS COCCOLITHS A N D FORAM1NIFE:RA 83

4 Predzscosphaera cretacea (Arkhangelsky), side view, electron mxrograph A1 I I I / i N, X5500

5. Watznauerza barnesae (Black), distal view, electron inlcrograph M 1/20 N, X5OOO 6 Manzmtella pemmatoldea (Deflandre), proximal vie\\, electron m~crograph M 1/19

N, X6000. 1-3.5,6 Broznsorua parca Zone 4 Quadrum trzfzdum Zone

Plate 20

1. Biscutum constans (Gorka), distal view, electron micrograph M I117 N, X I 0 000. 2. a , b Watznaueria barnesae (Black) proximal view, electron micrograph IVI 1/21 K,

X6000; c Watznaueria barnesae (Black) distal view; d Zygodiscus diplogrammus (Deflandre), proximal view.

3. a Wataaaueria barnesae (Black), proximal view, electron microzraph M I119 N. X6000; b Prediscosphaera cretacea (Arkhangelsky), distal view.

4. a Watznaueria barnesae (Black), coccosphaere, electron micrograph M 1118 N. X6000; b Prediscosphaera cretacea (Arkhangelsky), distal view; c Tetralithus quadratus (Stradner); d Zggodiscus sp.

1 , 3. 4 Quadrum trifidum Zone 2 L3roinsonia parca Zone

Plate 21

1. a Micula clecussata Vekshina, electron micrograph M IIIIlO N, X6000. 2. a , b Same species, electron micrograph M 1/23 N, X5000; c Lucianorhabclus cag-

euxi Deflandre. 3. Thoracosphaera sp., electron micrograph M I11111 N, X4000. 4. Typical assemblage of coccoliths from Mielnik, electron micrograph M 111 N,

X2000. 1. 3 Quadrum trlfldum Zone -3,4 Bromsonia parca Zone

Plate 22

1. Globotruncana arca (Cushman), dorsal view, I G P M4Sll F, X80. 2. Globotruncana lapparenti Brotzen, dorsal view, IGP M4S/2 F, X100. 3. Clobigerinelloides asper (Ehreilberg), side view, IGP M5S/Z F, X200. 4. Globotruncana fornicata P!ummer, dorsal view, IGP M-IS14 F, X90. 5. Same species, ventral view, I G P M4S/5 F, X100. 6. Heterohelicc globulosa (Ehrenberg), side view, I G P M5S/3 F, X200. 7. Heterohelir striata (Ehrenberg), side view, IGP M8Sl2 F, X200. 8. Boli~inoides decoratus decoratus (Jones), side view, I G P M3Sl5 F, X70. 9. Stensioina eccculpta gracilis Brotzeil, dorsal view, I G P M3S/10 F, X80.

10. Cacelinella clementiana (Orbigny), dorsal view, I G P M3Sl8 F, X7O. 11. Same species, ventral view, I G P M3S/9 F, X70. 12. Neoflabellina rugosa (Orbigny), side view, I G P M3Sl16 F, X80.

l ? 2 , 4 , 5 , 8-12 Broinsonia parca Zone 3,6,7 Quadrum tr i f idum Zone

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