Chapter C2d Dinoflagellate cysts in the Campanian-Maastrichtian succession of Tercis les Bains (Landes, France), a synthesis

The Campanian-Maastrichtian Boundary G. S. Odin (editor) 2001 Elsevier Science B.V.

CHAPTER C2d

Dinoflagellate cysts in the Campanian-Maastrichtian succession of Tercis les Bains (Landes, France), a synthesis E. Antonescu, J.-C. Foucher, G. S. Odin, P. Schi0ler, A. Siegl-Farkas & G. J. Wilson

Sommaire Trois investigations independantes des kystes de dinoflagelles de la succession de Tercis ont permis de mettre en evidence divers signaux biostratigraphiques. Parmi ceux-ci, certains presentent des caracteres permettant de supposer qu'ils sont, en partie au moins, lies a des phenomenes evolutifs. Environ 11 disparitions pen vent etre citees: celles de "Exochosphaeridium? masureae'\ Odontochitina porifera, du genre Odontochitina (avec les deux especes O. operculata et O. costata), de Palaeohystrichophora infusorioides, Xenascus ceratioides, Chatangiella robusta, Corradinisphaeridium horridum, Raetiaedinium truncigerum {~R. evittigratium), "Chytroeisphaeridia solida'\ Samlandia carnarvonensis, Samlandia mayii\ huit apparitions sont signalees dans le meme intervalle de depot: celles de Cerodinium diebelii et Microdinium carpentierae, Trithyrodinium evittii, Alterbidinium sp. cf. A. acutulum, Alterbidinium minus, Alterbidinium sp., Alterbidinium varium\ peut-etre aussi celle de Pyxidinopsis bakonyensis mais la distinction entre ce taxon et les 2 especes de Samlandia serait a preciser tout le long de la serie. La majorite de ces dix-neuf signaux semble potentiellement utile pour des correlations locales, regionales ou interregionales. Ceci fait des kystes de dinoflagelles un outil biostratigraphique particulierement efficace pour caracteriser la succession de Tercis et elaborer des correlations avec le domaine boreal, avec lequel de nombreux taxons sont communs, comme avec le domaine tethysien. En particulier, la limite d'Etages pent etre reperee

grace a 5 criteres tres proches: 1- la disparition de Corradinisphaeridium horridum a la cote 112,4±2A, 2- rapparition commune de Alterbidinium sp. cf. A. acutulum a 112,4 ± 2,4 suivie de r apparition de Alterbidinium minus et de Alterbidinium sp. a 118,6 ± 3,8 elle-meme suivie, un peu plus haut, par 1'apparition de A. varium, 3- la disparition de Raetiaedinium truncigerum a 118,6 ±3,8, 4- la disparition de "Chytroeisphaeridia solidd' a 126,9 ±4,5 et 5- la double disparition de Samlandia mayii et de S. carnarvonensis audessus de la cote 122,4. Ces changements de microflore sont rassembles dans un intervalle de depot dont la duree serait de I'ordre de 0,5 Ma. Avec ce nombre remarquable de marqueurs potentiels, les dinoflagelles se revelent etre le groupe fossile le plus interessant pour la caracterisation et la reconnaissance de la limite Campanien-Maastrichtien. 1. Introduction The study of the dinoflagellate cysts (and acritarchs) of the Campanian-Maastrichtian succession at Tercis has been undertaken by E. Antonescu following treatment of 45 samples; 20 of these samples were also requested by A. Siegl-Farkas for a quick comparison with the Hungarian deposits; finally, 11 selected samples were submitted to P. Schi0ler and G. J. Wilson for more intensive study and comparison with the material known from the historical stratotypes and the Pacific Area. Following these three studies, 71 taxa, 22 taxa, and 100 taxa, respectively, could be identified and the total

254

list of fossils (appendix 1) comprises about 145 names. Taxonomic problems still remain to be solved for definitive combination of the taxa distribution observed during the different studies. However, the vertical distribution of the species shows a significant renewing of the microflora with a number of taxa disappearing and others appearing along the studied Campanian-Maastrichtian succession. These signals can be compared from one study to another allowing an estimate of the ease for their recognition in the studied succession. Comparison with the record in other sections allows the documentation of potential correlative events.

cession at Tercis. An exact number cannot be given for several reasons including taxonomic problems, or the sporadicity of the concerned taxon (which may produce apparent FO or LO as a result of variation in abundance), or difference in sampling density. Figure 1 gives a summary of the possible criteria which can be of interest for correlation; figure 2 shows the distribution of the studied samples and of the events along the succession. The criteria are briefly discussed below.

2.1. Listing

1- LO genus Nelsoniella Schi0ler & Wilson (chap. C2b) acknowledge the presence of this taxon in lower and middle Campanian strata elsewhere from central and northwest Europe. The absence from the Tercis section may be environmental but it may also suggest that the Campanian stage is locally represented by its upper part only.

There are about 20 apparent first occurrences (FO) or last occurrences (LO) which seem to be located in the upper Campanian-lower Maastrichtian suc-

2- LO ''Exochosphaeridium? masureae'' Antonescu et al. and Schi0ler & Wilson indicate a sub-continuous presence of this taxon up to level

2. Dinoflagellate bio-signals

Biosignal

Author(s)

1

LO Nelsoniella

2

LO "Exochosphaeridium?

3

LO Odontochitlna porifera

masureae"

4

LO genus Odontochitlna

5

LO Palaeohystrichophora infusorioides

Siegl-Farlcas

Schioler & Wilson

Antonescu et al.

Conclusion

-

below section

.

below section

n.d.

23.8-37.5

23.8-34.8

n.d.

23.8-37.5

22.5-23.3

n.d.

37.5-65.0

76.0-80.6

(86.9?)

6.4-13.7

23.8-37.5

34.8-39.5

(->97.7)

29.3

±5.5

30.6 ±6.8 78.3

±2.3

LOO 37.1 ±2.3

6

FO Cerodinium diebelii

n.d.

65.0-76.0

(0.5) 80.6-86.9

7

FO Microdinium carpentlerlae

n.d.

65.0-76.0

n.d.

8

FO Trithyrodinium evittii

n.d.

(Cf. at 23.8/37.5)

9

LO Xenascus ceratioides

n.d.

86.5-95.6

n.d.

91.0 ±4.5

10

LO Chatangiella? robusta

n.d.

95.6-110.0

n.d.

102.8 ±7.2

11

LO Corradinisphaeridium

horridum

12 FO Alterbidinium sp. cf. A. acutulum 13 FO Alterbidinium minus +Alterbidinium sp.

110.0-122.4

n.d. n.d.

(15.8)

110.0-122.4

n.d.

(37.5)

110.0-122.4

(74.0)

77.5-80.6

99.0-109.5

±5.5

70.5 ±5.5 79.0 ±1.6

112.4

±2.4

110.0-114.8

FCO 112.4 ±2.4

114.8-122.4

FCO 118.6 ±3.8

14

FO Alterbidinium varium

n.d.

(23.8) (154)

152.47-155.1

15

LO Raetiaedinium

n.d.

110.0-122.4

114.8-122.4

16

LO "Chytroeisphaeridia solida"

n.d.

122.4-154

122.4-131.4

truncigerum

70.5

? 154 118.6

±3.8

126.9 ±4.5

17

LO Samlandia carnarvonensis

n.d.

122.4-154

n.d.

>122.4

18

LO Samlandia mayli

n.d.

122.4-154

(single at 80.6)

>122.4

19

LO. Samlandia/Pyxidinopsis

122.4-154

155.1? (160)

above quarry

97.2-110

(155)

Fig. 1. Location of key dinoflagellate first and last occurrences observed in the succession at Tercis les Bains. The events are listed with their uncertainty interval resulting from the combined observations in the three independent studies. The inferred average position is shown in the far right column. The most significant (and best established) features are shown with bold types. In addition, the FO of P. bakonyensis (as observed by one of us, A.S.F.) could be considered at a level coincident with the LO of the genus Odontochitina. Bracketted numbers mean isolated occurrences.

255

23.8 and an absence above. The LO is thus well documented between levels 23.8 and 34.8.

& Wilson. Its LO can thus be located in the interval 23.8-37.5.

3- LO Odontochitina porifera This taxon is recorded from low levels (14.8, 22.5, and 23.8) by Antonescu et al. and by Schi0ler

4- LO genus Odontochitina The two taxa O. costata and O. operculata are combined by Schi0ler & Wilson and recorded

E 3 "c •5

""•

a H Z D 0) lU

.^

< .2 A

1— J c5 T3

w

I

CD

o

2 § i .1E

H

E d

'^ 1 :

LO Samlandia mayii & S. carnarvonensis

i

"" >

^

CO LU -J

LU

5

< €

1 i

""A^ l i i j '; f j -

T—

l!:i-:;i

0)

•

LO Corradinisphaeridium horridum •£ E i (D

J :

x>

1? L i [-

1

00

z D

• 1

o_ ^

C7)

CVJ

~Si

& —Q

p

CT <

1
is

® Q.

E 11 05
«

w *c 'E D

Q.

g o o

(5 E

Z3 3 W

O CO (])

2

O

'•°

1 L

CM

i

L^ 2 S

^

o

2

"5

1

O "c

•cj

u-

1 i1

1 LO "Exochosphaeridium? Yk masureae

1 o_

z < z

i X

o

o o o.

^

1 ! ^

1

8 3 (0

1

4^ ! 8

FO Cerodinium diebelii

_

c

—> < —Q

r

CD

O LU

CO

1 ^ LO genus Odontochitina

-

"o>

'"

J

§• 1 i » o 8 ? 5 <=>i ^ = 1 e""

o ^ oo o "^ _

r-

2

o< L

LO Raetiaedinium truncigerum ^ 1 (= R. evittigratium)

o

fe 52

'
3 W

z

V- -

1-

0) _

oJ col

0 r"

z <

^ •§ •= w

8

3

(0 c:

— CO

^ti

UJ Q-

' o_ CJ T-

o

o 8 "i. _ 0_J— - iO- E.O O

w

o

^

-J

S iS (0

o

'-'

(0 (0

c

CL

TJ

O

JD

O -J

—

< o

dramng.GSO 99-

1

x: (0

2 t5 c

2 JZ

O

Fig. 2. Key dinoflagellate events in the sedimentary succession at Tercis. The most significant are shown close to the columns to the left. The leftmost three columns show the location of the samples independently investigated in the this volume by Siegl-Farkas (ASF), Schi0ler & Wilson (S & W) and Antonescu et al. (A et al).

256

consistently as O. costata/operculata up to level 37.5 (absent at level 65.0), while Antonescu et al. quote O. costata consistently up to level 39.5 (absent at their next levels up at 41.2 and 45.1). Only a poor microflora has been obtained from the latter two samples and this might have resulted in an apparent absence. Antonescu et al. quote the LO of Odontochitina sp. at level 76.0 and the LO of a questionable form (cf.) at level 86.9. The next sample studied by Antonescu et al. above their level 76.0 is at level 77.5 but it contains a poor microflora. The next rich flora is located at level 80.6 with no Odontochitina quoted from it. In short, we can suggest the interval 76.0-80.6 for location of the LO of the genus Odontochitina with well identified forms present up to level 39.5 only. The LO of the genus Odontochitina is considered a key one by Schi0ler & Wilson who note that it is commonly recorded from around the Campanian-Maastrichtian boundary and that the species O. porifera usually disappears slightly before the other species of the genus. The same pattern is true in Tercis and this supports the possible evolutionary meaning of the last occurrences. The LO of the genus can be used for correlation between Tercis and the historical stratotypes of the Campanian and Maastrichtian stages. In Charente, Wilson (1971) quotes the taxon from Aubeterre. This is important because the latter section plays an important role in the historical definition of the Campanian (and thus on the location of the Campanian-Maastrichtian boundary) though it is not the "type section of the Campanian" as commented by Neumann & Odin (this volume, chap. Fl). Correlation can also be achieved with the Maastrichtian in Limburg where the genus has been quoted by different authors (see Wilson, 1974). According to the review by Slimani (1995 and references therein), the genus (with the two forms O. costata and O. operculata) seems to disappear in the Beutenaken Member of the Gulpen Formation from Limburg. 5- LO Palaeohystrichophora infusorioides This taxon is quoted from all three studies. However, it is considered very rare in two of them. Antonescu et al. record the taxon consistently up to

level 34.8 with additional occurrences at levels 56.1 and 97.7. This may point to a LO at the latter level (between samples 97.7 and 98.0) with a last common occurrence between levels 34.8 and 39.5. 6- FO Cerodinium diebelii The taxon seems to be the first new species appearing in the succession. It is relatively rare in the sediments of Tercis and is present from level 86.9 upward according to Antonescu et al. but there is another disjoined old occurrence at level 0.5. Schi0ler & Wilson quote the species from level 76.0 at Tercis and the FO may thus be located between sample 76.0 and their previous sample at level 65.0. The old occurrence would need to be confirmed. Schi0ler & Wilson (this volume) note that the FO of the taxon is commonly located in Maastrichtian deposits from central and northern Europe except in the North Sea where it is quoted from the late Campanian. The FO is precisely located within the late Campanian from Tercis; compared to its often quoted Maastrichtian FO this comparatively old occurrence most probably represents an evolutionary appearance of biostratigraphical interest. 7- FO Microdinium carpentierae Schi0ler & Wilson suggest that this otherwise infrequently quoted species might serve as a marker for the upper Campanian. They record its FO between levels 65.0 and 76.0 at Tercis. This criterion is thus contemporaneous with the former one. 8- FO of Trithyrodinium evittii Antonescu et al. observe the FO of T. evittii (see pictures 54 & 55 of these authors) between levels 77.5 and 80.6 with a possibly related form slightly below, at level 74.0. This occurrence in late Campanian deposits is commented on by the authors as the oldest known to date for this taxon: the FO is usually considered a criterion for the basal Maastrichtian in North America or at Hemmoor (see Slimani, 1995). The FO observed at Tercis can thus represent the evolutionary appearance of the taxon and the event has a good correlation potential. Schi0ler & Wilson do not record T. evittii proper from the Tercis quarry but illustrate a T. cf. evittii (picture 9 in their contribu-

257

tion, this volume). In the absence of a clearly visible periphragm on that specimen, it may alternatively be an endocyst of another peridinoid dinoflagellate. 9- LO Xenascus ceratioides It may be that the high occurrences (level 86.9) of cf. Odontochitina quoted by Antonescu et al. (criterion 4 above) refer in fact to that species which is morphologically affiliated and usually survives the LO of the genus Odontochitina. Schi0ler & Wilson quote the taxon Xenascus ceratioides continuously from the base of the main section up to level 86.5. The LO between levels 86.5 and 95.6 is documented at Tercis in the upper Campanian portion of the succession, about 1 Ma before the stage boundary according to the scale favoured in this volume (Odin, chap. E5c). As far as we can judge, this location seems to be subcontemporaneous with that in Limburg (late Campanian Beutenaken Member, Slimani, 1995) and in Denmark (there, however, within the early Maastrichtian Belemnella lanceolata Zone according to Wilson, 1974). 10- LO Chatangiellal robusta This taxon is considered by Schi0ler & Wilson (chap. C2b) to have a restricted range entirely comprised in the upper to uppermost Campanian portion of the Tercis succession. The LO of the species is observed between levels 95.6 and 110.0. This LO is located very near the stage boundary as it is defined in this volume. This marker may have a regional (Aquitaine Basin) correlation potential according to the authors but a wider application could be considered given the quotation of this taxa from contemporaneous deposits from NW Europe (Wilson, 1974) and the East coast of North America (Benson, 1976; Slimani, 1995). 11- LO Corradinisphaeridium horridum This taxon is quoted in the two contributions by Antonescu et al. and Schi0ler & Wilson. Combination of the two studies indicates a LO between levels 110.0 and 114.8. As discussed by Schi0ler & Wilson, this marker seems to be a very good candidate for a stage boundary approximation and for correlation because it is present at Tercis, in

northern Italy (Corradini, 1973) and in southern Germany (Kirsch, 1991). 12- FO Alterbidinium cf. acutulum Schi0ler & Wilson quote it from two disjoined levels (15.8 where it is rare and 122.4 where it is common) while Antonescu et al. observe a more grouped occurrence above level 114.8. Combined with the former information, the latter distribution would seem to document a first common occurrence (FCO) between levels 110.0 and 114.8,Ue chronostratigraphic implication of which remains to be discussed. According to one of us (P.S.) A. acutulum is present (although rare) in the Coniacian Arnager Limestone of Bomholm (Denmark) and occurs sporadically in what is strongly believed to be the Santonian-Campanian of New Zealand (Schi0ler, 1992; Roncagha et al., 1999). However, Kirsch (1991) sees only a single representative of the genus Alterbidinium with a FO below the Campanian-Maastrichtian boundary in the Tethyan realm. The occurrence of several species of this genus might thus characterise Maastrichtian levels and thereby have a good potential as a stage boundary approximation. 13-FO Alterbidinium minus (and Alterbidinium sp.) In the study by Schi0ler & Wilson (this volume) Alterbidinium minus is recorded at levels 37.5, 95.6, and 122.4 where a large number of specimens are encountered. Antonescu et al. note the taxon at and above level 122.4. In the latter work, the distribution is considered to document a FO of A. minus which would approximate the stage boundary between level 114.8 and 122.4. Thus, it may be considered that the taxon has a first common occurrence in the interval 118.6 ±3.8 where the stage boundary is located at Tercis. Antonescu et al. quote Alterbidinium sp. from level 122.4 and above. Following the FCO of A. cf. acutulum (at level 112.4 ±2.4), there is thus a significant increase in occurrence of species of the genus Alterbidinium in the lowermost Maastrichtian samples investigated. The significance of this increase may be local and related to environmental features such as the opening of the Aturian Basin towards the ocean; however, it is possible that the common occurrence of several species of the genus Alter-

258

bidinium is useful in regional and possibly tethyan correlation. 14- FO of A. varium The species A. varium is quoted from slightly higher in the succession (levels 154 and 155.1 in the studies by Schi0ler & Wilson and Antonescu et al., respectively). A disjoined occurrence at level 23.8 might weaken the value of this index. Kirsch (1991) quoted the FO of this taxon from the lower Maastrichtian of south Germany and this is generally consistent with the obervation at Tercis. 15-LO Raetiaedinium truncigerum (~ R. evittigratium) The only species of the genus Raetiaedinium quoted by Schi0ler & Wilson is R. evittigratium\ it is quoted from six out of eight samples in the interval from the lowest sample studied by them (at 15.8) up to the highest Campanian sample (at level 110.0). The only species of the genus quoted by Antonescu et al. is R. truncigerum; its distribution is not continuous, but the taxon is documented up to, and including, level 114.8, the highest Campanian sample studied by these authors. From the relevant descriptions, and from the illustrations (compare picture 34 of Schi0ler & Wilson and pictures 30-31 of Antonescu et al.), it is clear that the two species are very similar (only separated by the presence/absence of granulation on the endocysts). Herein, we have chosen to group the two taxa under the older name R. truncigerum with a LO within the stage boundary interval between levels 114.8 and 122.4 (at 118.6 ±3.8). The LO of R. truncigerum is generally considered an upper Campanian event in Limburg (Slimani, 1995, p. 56); therefore, the observation at Tercis probably represents an evolutionary extinction useful for correlation purpose between the tethyan and the boreal domain. 16- LO "Chytroeisphaeridia solida'' This taxon was initially established by Wilson (1974, unpublished). It is recorded, described and illustrated by Antonescu et al. Its distribution is spotty from the base of the d'Avezac Unit up to, and including, level 122.4. The LO observed between levels 122.4 and 131.4 follows an absence of observation in the samples investigated from the

previous 20 metres of the succession. In the Limburg province, the taxon is given as present in the Zeven Wegen and Beutenaken Member (at Beutenaken) by Foucher (in Robaszynski et al., 1985) and absent above. The taxon can thus be considered as mostly a Campanian index with a very short presence in the Maastrichtian. Schi0ler & Wilson have recorded a distinctive species, Cassiculosphaeridia? intermedia which was initially established by Wilson (1974, unpublished) and pubhshed later by Slimani (1994). Its distribution is from the base of the d'Avezac Unit up to, and including, level 122.4. But the taxon is also known from throughout the Maastrichtian (P. S., personal observation) and even the Danian of Limburg (Brinkhuis & Schi0ler, 1996) and thus, the apparent LO in Tercis only documents a locally dependent distribution. 17 and 18- LO Samlandia carnarvonensis and LO Samlandia mayii These two taxa are recorded by Schi0ler & Wilson up to and including the lowermost Maastrichtian sample studied by them from Tercis (at level 122.4). According to these authors, this distribution corresponds to what is documented in the literature i.e. a LO within the earliest Maastrichtian Belemnella lanceolata Zone of NW Europe. Therefore, the LO of the two taxa seems to be very valuable for establishing a correlation between the stage boundary as defined at Tercis and the belemnite succession of NW Europe. Up to now, the precise location of their LO is poorly constrained as no samples were studied by Schi0ler & Wilson between level 122.4 and level 154 and because Antonescu et al. did not systematically identify those taxa. However, the facts that the two species of Samlandia are absent above the B. lanceolata Zone and that they are present at Tercis at least in the first 6 or 7 metres attributed to the Maastrichtian, strongly suggest that the conventional point accepted by the Working Group correlates with a level within (or immediately below) the B. lanceolata-htaxing beds of NW Europe. 19- LO Samlandia/Pyxidinopsis In the study by Antonescu et al., the name Pyxidinopsis bakonyensis has been used to provi-

259

sionally designate several forms which probably include this taxon as documented by Siegl-Farkas in her work as well as other morphologically nearby forms of the genus Samlandia as documented by Schi0ler & Wilson from Tercis. Pictures of S. carnarvonensis and of P. bakonyensis show obvious similarities. The only difference between the two genera Pyxidinopsis and Samlandia is the absence/presence of an external wall layer (ectophragm) kept up by processes. In the samples studied by Schi0ler & Wilson, there is a morphological continuum from specimens of Samlandia with a closely appressed ectophragm CPyxidinopsis-likQ'' but ectophragm still visible at the apex: see Schi0ler & Wilson herein, picture 51) to specimens with a detached ectophragm, forming a cavity between ectophragm and inner body (compare Schi0ler & Wilson, this volume, pictures 51-53). If one considers that they all have an ectophragm (although sometimes so closely appressed to inner body that it is hardly visible), this means that they all are Samlandia. Alternatively, it may be held that specimens like the one in picture 51 belong to P. bakonyensis. If one adds that the distinction between 5. carnarvonensis and S. mayii is mainly based on the width of the cavity between inner body and the ectophragm, it may be suggested that there exists a morphological transition from members of Pyxidinopsis over S. carnarvonensis to S. mayii. The true relationship between the two genera awaits taxonomic studies to be resolved. The FO of P bakonyensis is quoted from between levels 64.8 and 77.5 in the preliminary study by Siegl-Farkas (chap. C2a). The significance of this FO is still unknown. Pyxidinopsis bakonyensis is quoted from the highest sample studied by Siegl-Farkas (level 155) but is absent from the lower four samples collected from between levels 110 and 131. Antonescu et al. also indicate the presence at level 155.1 which is the highest sample where a significant number of dinoflagellates has been observed. As a result, the LO of P. bakonyensis is probably located above the levels investigated from the main section at Tercis but, as explained above, further taxonomic studes will be needed to establish a definitive distribution pattern for the Samlandia/Pyxidinopsis group.

2.2. Possible subdivision of the succession at Tercis Based on the evidence from the three independent studies, we suggest a subdivision of the local succession which considers both the best established local features (shown in bold types in figure 1) and the possible future application for correlation with other basins. The data are shown graphically in figure 2 along a stratigraphic column of the succession at Tercis. We propose three major biostratigraphic boundaries associated with 1- the LO of "E.l masureae'\ 2- the contemporaneous FO of C. diebelii and M. carpentierae, and 3- the LO of R. truncigerum. This proposal should not be considered a formal biozonal subdivision but simply a grouping of beds. The first boundary is close to the LO of O. porifera or the last continuous occurrence of P. infusorioides. The second boundary is sub-contemporaneous with the LO of the genus Odontochitina and of the FO of T. evittii; it may also correspond to the base of the P. bakonyensis assemblage suggested by Siegl-Farkas (this volume). The third boundary is supported by a variety of sub-contemporaneous (the word sub-contemporaneous is used here in the sense that the apparent age difference known to us does not exceed about 0.3 Ma) features such as the LO of C. horridum, the FO or strong increase in abundance of several species of Alterbidinium and the last occurrences of Samlandia mayii, of S. carnarvonensis and of "Chytroeisphaeridia solidd' (which are all located slightly above). 3. Correlation 3.1. Limburg and belemnite-bearing chalk Correlation with the historical stratotype of Limburg can be suggested using many taxa present in both areas as documented by Wilson (1971, 1974), Foucher (in Robaszynski, 1985), Slimani (1995). Potential markers are listed below in stratigraphic order and from base to top. - The LO of "£".? masureae'' (key marker 2 in figure 1) coincides with the limit between the mucronata and the mucronata "minor" Zones in Limburg. At Tercis, it is located at about level 29.3;

260

- The LO of P. infusorioides (key marker 5 in figure 1) occurs within the base of the mucronata "minor" Zone in Limburg. At Tercis it is located at about level 37.1 (possibly up to level 97.7). - The LO of the genus Odontochitina (key marker 4 in figure 1) occurs within the B. langei zone of Limburg (for O. costata) and between the top of the B. langei Zone and the base of the pseudobtusa to obtusa Zones (for O. operculatd). At Tercis the last specimens of the genus are known from about level 78.3. - The LO of R. truncigerum (key marker 15 in figure 1) is also located between the top of the B. langei Zone and the base of the pseudobtusa to obtusa Zones of Limburg. At Tercis the last specimen of the taxon is recorded from about level 118.6. - The FO of T. evittii (key marker 8 in figure 1) is quoted from the same two previously mentioned belemnite zones. At Tercis, it is located at about level 79.0. - The FO of A. varium (key marker 14 in figure 1) is also quoted from the same interval as the three above in Limburg. At Tercis, it is located at about level 154. The comparison indicates that a number of the dinoflagellate events considered in the list above fall within the Beutenaken Member of the Gulpen Formation in Limburg. This is due both to the fact that the stage boundary is within this Member (Jagt, this volume), and to the fact that the Beutenaken Member includes a condensed succession apparently comprising the B. langei and the B. lanceolata zones (Jagt, this volume, chap. E2). Dinoflagellates seem to be the best tool for correlation of Tercis with the belemnite-bearing deposits. 3,2. Charente and the Campanian historical stratotype area Correlation with the Campanian historical stratotype of Charente can be achieved using dinoflagellates as described by Wilson (1971). Neumann & Platel (1983) noted that the LO of P. infusorioides (criterion 5 in figure 1) occurs below the FO of the large benthic foraminifera Orbitoides

media. The latter is the key marker in the biozonation of the stratotypic succession of Champagne charentaise: for years, this FO was supposed to "define" the Campanian-Maastrichtian boundary. Large benthic formaminifera are absent from Tercis but indirect correlation with this zonation is made possible thanks to dinoflagellates. 3.3. Mediterranean connection Floral exchanges through the mediterranean connection can be documented in Rumania and Hungary. In Rumania, there are two main depositional areas: the Carpathian and the platforms (Moesian, Moldavian, and Dobrogea considered to be part of the East-European platform). These areas were parts of the Tethyan domain during the Cretaceous time. Some of these sedimentary areas may have been submitted to sub-boreal influence. However, the so-called Rumanian "chalk" (in the local use) is not a true chalk in Hthological terms. The possibility to undertake correlation between SW France and Rumania using the distribution of dinoflagellates has been advocated by Antonescu et al. in this volume. A study on the "Chalk of Dobrogea" has been initiated on two drill holes (unpublished work, E.A.). In this area, located more than 2.000 km to the East of Tercis, this study of the microflora indicates that several key species from Tercis are also present in Rumania; that very similar assemblages can be recognised from the two areas, and that the chronology of the assemblages is remarkably similar. Therefore, the succession of palaeontological events described at Tercis for characterisation of the local depositional series may be used for correlation with Rumania. In Hungary, there are two megatectonic units named the Pelso and Tisza units. These units were situated in the northern part of the Mediterranean Domain of the Tethys Realm (Bilotte et al., this volume, chap. A4) during the Late Mesozoic time. They were not too far but separated from each other. Different Late Cretaceous formations were deposited in both units but they can well be correlated using palynomorphs (Siegl-Farkas, 1999). The most complete classical late Cretaceous transgressive profile in the Pelso Unit is 900 m

261

thick including 750 m of continuous marine formations. The latter were subdivided into two dinoflagellate zones: the O. operculata and the P. bakonyensis Assemblage zones and 6 subzones (Siegl-Farkas, 1997). These zones were correlated with the CC 17b-CC 22c nannoplankton zones used in the mediterranean domain from the Santonian to the late Late Campanian (Siegl-Farkas & Wagreich, 1996a). The combination of data thus allow reliable micropalaeontological correlations. The dinoflagellate assemblages of the Pelso Unit show more similarity to the French areas (Tercis and Paris Basin) than to the nearby Tisza Unit. The microflora in common includes A. deflandrei, C. utinensis, Chatangiella spp., Dinogymnium spp., Gillinia hymenophora, Manumiella spp., Odontochitina spp., T. castanea, T. ginella, T. evittii, P. infusorioides, P. cingulatum, P. bakonyensis, S. angustispinum, and the acritarch Tarsisphaeridium geminiporatum, amongst others. In the Pelso Unit (Hungary) the LO of the genus Odontochitina and the FO of P. bakonyensis coincide and the same is probably true in Tercis where the latter form has only been identified at and above level 77.5 by one of us (A.S.F.). The profile from Pelso was obtained using 3 boreholes, the monotypic species Odontochitinopsis molesta (Deflandre 1937) Eisenack 1961 was found in this profile at the boundary between the two dinoflagellate zones. O. molesta was described from the Paris Basin and, to our knowledge, only found in Hungary since that time. Finally, T. geminiporatum is also a potential mean for connection from Hungary to Spain and to Tercis. 3.4. Pacific connection Mao & Mohr (1992) and Mohr & Mao (1997) records the LO of P. infusorioides from the Campanian/Maastrichtian transition in the Kerguelen area (southern Indian Ocean). In Australia, Helby et al. (1987) records the LO of the species in the Xenikoon australis Zone (Lower Campanian), possibly extending up to the Isabelidinium korojonense Zone (Middle Campanian to Lower Maastrichtian). However, in the New Zealand East Coast Basin its LO is in the basal Haumurian

(probably near the Santonian-Campanian boundary). This latter observation is based on results from analyses of closely spaced sample successions from several sections covering the Teratan-Haumurian (Coniacian-Maastrichtian) interval (Schi0ler & Wilson, 1998; Roncagha et al., 1999). At Tercis, the LO of P. infusorioides has been located near the top of the late Campanian d'Avezac Unit but the taxon becomes rare above level 34.8. Kirsch (1991) reports the LO in the mid Campanian. Roncaglia & Schi0ler (1997) and Roncaglia et al. (1999) record Alterbidinium varium and Alterbidinium minus from the mid Waipara section. New Zealand, of Haumurian age, correlating with a level low in the mid-late Campanian; both species seem to appear much later (in the Maastrichtian) in Europe (criteria 13 & 14, figure 1). However, one of us (PS.) observed the species in ditch cuttings from the late Campanian in the North Sea (Dutch sector). Mohr & Mao (1997) report A. varium as appearing in the lower Campanian in the Kerguelen area. Southern Indian Ocean. The range of this fairly newly established (1991) species appears to be somewhat longer in the south seas than in Europe. As noted by Schi0ler & Wilson (chap. C2b) the events LO Odontochitina, FO C. diebelii, and LO Xenascus may prove useful for correlation of the Campanian-Maastrichtian boundary interval between Europe and Australasia. 4. Conclusions The dinoflagellate assemblages extracted from the sediments deposited at Tercis have been successfully investigated. Eleven last occurrences have been documented: "Exochosphaeridium? masureae'\ Odontochitina porifera, genus Odontochitina, Palaeohystrichophora infusorioides, Xenascus ceratioides, Chatangiellal robusta, Corradinisphaeridium horridum, Raetiaedinium truncigerum (-R. evittigratium), "Chytroeisphaeridia solida'\ Samlandia carnarvonensis, Samlandia mayii. Seven additional first occurrences are also recognised: Cerodinium diebelii, Microdinium carpentierae, Trithyrodinium evittii, Alterbidinium sp.

262

cf. A. acutulum, Alterbidinium minus, Alterbidinium sp., Alterbidinium varium. The majority of these locally observed events are potentially useful both for local and world-wide correlation. This set of events makes the dinoflagellates a very powerful biostratigraphical tool for correlating the succession at Tercis with other basins both in the boreal and the tethyan domains. In particular, the stage boundary itself seems to be determinable by using at least five bracketing events including (listed from the base up): 1) the LO of Corradinisphaeridium horridum at 112.4 ±2.4, 2) the FCO of Alterbidinium sp. cf. A. acutulum at 112.4 ±2.4 followed by the FO of Alterbidinium minus-\-Alterbidinium sp. at 118.6 ± 3.8, followed by the FO of A. varium, 3) the LO of Raetiaedinium truncigerum at 118.6 ± 3.8, 4) the LO of "Chytroeisphaeridia solida'' at 126.9 ±4.5, and 5) the contemporaneous LOs of Samlandia mayii and S. carnarvonensis above level 122.4. These floral changes are concentrated in an interval which is estimated to represent about 0.5 Ma. With this high number of potential markers, the dinoflagellates may be the most powerful tool for characterisation and recognition of the Campanian-Maastrichtian boundary in the Tercis succession and for correlation between the tethyan and the boreal domains. (Prepared: March 1999; revised: April 1999) 5. Appendix 1: List of the dinoflagellate taxa quoted from the succession at Tercis les Bains (Antonescu et al.: EA, Siegl-Farkas: SF, Schi0ler & Wilson: SW) Dinoflagellates, possible dinoflagellates and acritarchs from the Tercis outcrops, are listed alphabetically. Illustrated taxa are asterisked, and followed by picture number(s). The generic allocation of taxa follows WilHams et al. (1998). The genera Cyclopsiella, Fromea, Membranosphaera, Palaeostomocystis, Paralecaniella and Tarsisphaeridium are considered acritarchs, following Fensome et al. (1990). Cleistosphaeridium spp. of Antonescu et al. is shown under Downiesphaeridium spp.; Alterbia acuminata of the study by Siegl-Farkas is shown

under Isabelidinium spp. with /. acuminatum', cf. Xenicodinium rugulatum of the study by SieglFarkas is shown under Tectatodinium. Achomosphaera ramulifera (Deflandre, 1937) Evitt, 1963, SW, EA Alisogymnium assamicum (Jain et al., 1975) Lentin & Vozzhennikova, 1990, SF Alisogymnium euclaense (Cookson & Eisenack, 1970) Lentin & Vozzhennikova, 1990, SF*13-14, SW*17, EA*13 Alisogymnium sp., EA*59 Alterbidinium cf. acutulum (Wilson, 1967) Lent. & Will., 1985; em. Khowaja-Ateequzzaman et al., 91, SW*6, EA*l-2;56 Alterbidinium minus (Alberti, 1959) Lentin & Williams, 1985; em. Khowaja-Ateequzzaman et al., 1991, SW*5, EA*3-6 Alterbidinium varium Kirsch, 1991, SW*4, EA*57(cf.) Alterbidinium sp., EA*58 Apteodinium deflandrei (Clarke & Verdier, 1967) LucasClark, 1987; emend. Lucas-Clark, 1987, SW*54, EA Apteodinium spp., EA*37-38 Areoligera coronata (O. Wetzel, 1933) Lejeune-Carpentier, 1938, SW*20 Areoligera medusettiformis O. Wetzel, 1933 ex LejeuneCarpentier, 1938, SW*21 Areoligera senonensis Lejeune-Carpentier, 1938, SW*23 Areoligera spp., EA*65 Batiacasphaera spp., SW Biconidinium reductum, (May, 1980) Kirsch, 1991, SW*3, EA*45(cf.) Canningia sp., SW*30 Cannosphaeropsis utinensis O. Wetzel, 1932; emend. Marheinecke, 1992, SW, EA*9; 68 Cassiculosphaeridial intermedia Slimani, 1994, SW*69 Cerodinium diebelii (Alberti, 1959) Lentin & Williams, 1987, SW*12,EA*14 Cerodinium spp., EA*75 Chatangiellal robusta (Benson, 1976) Stover & Evitt, 1978, SW*13 Chatangiella victoriensis (Cookson & Manum, 1964) Lentin & Williams, 1976, EA*11-12 Chatangiella cf. manumii (Vozzhennikova, 1967) Lentin & Williams, 1976, EA* 10 Chatangiella spp. (pars), SW, EA ''Chytroeisphaeridia solidd' in Wilson, 1974, EA*7-8 Cladopyxidium saeptum (Morgenroth, 1968) Stover & Evitt, 1978, SW Conneximura fimbriata (Morgenroth, 1968) May, 1980; emend. Marheinecke, 1992, SW*39

263 cf. Cordosphaeridium varians May 1980, SF*6 Coronifera oceanica Cookson & Eisenack, 1958; emend. May, 1980, SW*40 Coronifera striolata (Deflandre, 1937) Stover & Evitt, 1978, EA Corradinisphaeridium horridum (Deflandre, 1937) Masure, 1986; emend. Masure, 1986, SW*43, EA*1517 Corradinisphaeridium personatum (Corradini, 1973) Masure, 1986; emend. Masure, 1986, SW*44 Cribroperidinium cf. wetzelii (Lejeune-Carpentier, 1939) Helenes 1984, SW Cribroperidinium wilsonii (Yun, 1981) Poulsen, 1996, SW*70 Cyclonephelium spp., EA Cyclopsiella spp., SW*73 Dapsilidinium pseudocolligerum (Stover, 1977) Bujak et al., 1980, SF*7 Dapsilidiniuml cf. pumilum (Davey & Williams, 1966) Lentin & Williams, 1981, SW*61 Deflandrea cf. galeata (Lejeune-Carp., 1942) Lentin & Williams, 1973; emend. Lejeune-Carp. & Sarjeant, 1981, SW*14 cf. Dingodinium cerviculum Cookson & Eis., 1958; emend. Khowaja-Ateequzzaman et al., 1990, SF*8 Dinoflagelle sp. X in chap. C2c, EA*64 Dinoflagelle sp. Y in chap. C2c, EA*62 Dinoflagelle sp. Z in chap. C2c, EA*66 Dinogymnium acuminatum Evitt et al., 1967, SF, SW*19, EA*20 Dinogymnium digitus (Deflandre, 1935) Evitt et al., 1967, SF Dinogymnium longicorne (Vozzhennikova, 1967) Harland, 1973; em. Lentin & Vozzhennikova, 1990, SW*18, EA*18 Dinogymnium nelsonenso (Cookson, 1956) Evitt et al., 1967, SF Dinogymnium undulosum Cookson & Eisenack 1970, SF Dinogymnium spp. (pars), SF, SW*22, EA*19 Downiesphaeridium spp., SW*62, EA Eatonicysta pterococcoides (O. Wetzel, 1933) Sarjeant, 1985, SW*29 Exochosphaeridium bifidum (Clarke & Verdier, 1967) Clarke et al., 1968; em. Davey, 1969, SW*35 Exochosphaeridium phragmites Davey et al., 1966, SW Exochosphaeridium spp., EA ''Exochosphaeridium! masureae'' in Slimani, 1996, SW*36, EA*21-22 Flandrecystafurcata SUmani, 1994, SW*50 Florentinia aculeata Kirsch, 1991, SW*41

Florentinia ferox (Deflandre, 1937) Duxbury, 1980, SW*42, EA Florentinia spp., EA Fromea chytra (Drugg, 1967) Stover & Evitt, 1978, SW*79 Fromea staveia Elsik, 1977, SW*78 Fromea spp., EA*72 Genus 1 in Schi0ler & Wilson, this volume, SW*82-83 Genus 2 in Schi0ler & Wilson, this volume, SW*81 Genus 3 in Schi0ler & Wilson, this volume, SW^ll Gillinia hymenophora Cookson & Eisenack, 1960, SF*16-17, SW Glaphyrocysta cf. perforata Hultberg & Malmgren, 1985, SW*25 Glaphyrocysta sp., SW*32 Hafniasphaera septata (Cookson & Eisenack, 1967) Hansen, 1977; emend. McLean, 1971, SW*46 Hystrichodinium pulchrum Deflandre, 1935, SW*38, EA Hystrichosphaeridium recurvatum (White, 1842) Lejeune-Carpentier, 1940, SW*59 Hystrichosphaeridium salpingophorum (Deflandre, 1935) Deflandre, 1937; em. Davey & WilHams, 1966, SW*58 Hystrichosphaeridium tubiferum tubiferum (Ehrenberg, 1838) Deflandre, 1937; em. Davey & Wilhams, 1966, SW Hystrichosphaeridium spp. (pars), EA*60 Hystrichostrogylon coninckii Heilmann-Clausen in Thomsen & Heilmann-Clausen, 1985, SW Hystrichostrogylon membraniphorum Agelopoulos, 1964, SW Impagidinium rigidaseptatum Slimani, 1994, SW*47 Impagidinium spp., EA*70-71 Impletosphaeridium spp., SW Isabelidinium cooksoniae (Alberti, 1959) Lentin & Wilhams, 1977, SW*7(cf.), EA*27-29 Isabelidinium spp. (pars), SW*8, EA*61(?) Isabelidinium spp. with /. acuminatum (Cookson & Eisenack, 1958) Lentin & Wilhams, 1976, SF*5 Kallosphaeridiuml granulatum (Norvick, 1976) Stover & Evitt, 1978, SW*72 Manumiella cf. Manumiella sp. 3 of Askin, 1988, SW*1 Manumiellal cretacea (Cookson, 1956) Bujak & Davies, 1983, EA*23 Membranosphaera maastrichtica Samoilovich in Samoilovich & Mtchedhshvih, 1961, SW*71 Microdinium carpentierae Slimani, 1994, SW*74 Microdinium cf. ornatum Cookson & Eisenack, 1960, EA Microdinium sp. A, EA*32-33 Microdinium sp. B, EA*24

264 Microdinium group (pars), SW Montanarocysta aemiliana Corradini, 1973, SW*45 Odontochitina costata Alberti, 1961; emend. Clarke & Verdier, 1967, SW, EA*25 Odontochitina operculata (O. Wetzel, 1933) Deflandre & Cookson, 1955, SW*27 Odontochitina porifera Cookson, 1956, SW*28, EA*26 Odontochitina spp., EA Oligosphaeridium complex (White, 1842) Davey & Williams, 1966, SW, EA Oligosphaeridium sp., EA*69(?) Palaeocystodinium spp., SW*15(?), EA*40 Palaeohystrichophora infusorioides Deflandre, 1935, SF, SW, EA*49 Palaeostomocystis reticulata Deflandre, 1937, SW, EA*34-35 Palaeotetradinium silicorum Deflandre, 1936; emend. Deflandre & Sarjeant, 1970, SW*76, EA Palynodinium helveticum Kirsch, 1991, SW*24 Paralecaniella indentata (Deflandre & Cookson, 1955) Cookson & Eisenack, 1970; em. Elsik, 1977, SW Pervosphaeridium cf. monasteriense Yun, 1981, SW*37 Pervosphaeridium pseudhystrichodinium (Deflandre, 1937) Yun, 1981, SW, EA*36 Pervosphaeridium spp., EA Phanerodinium cayeuxii (Deflandre, 1935) Deflandre, 1937,EA*51 Pterodinium aliferum Eisenack, 1958; emend. Sarjeant, 1985, SW Pterodinium cingulatum (O. Wetzel, 1933) Below, 1981, SW, EA*39 Pyxidinopsis bakonyensis (Goczan, 1962) Stover & Evitt, 1978, SF* 10-12, EA*41-44; 78-79(cf.) Raetiaedinium evittigratium Kirsch, 1991, SW*34 Raetiaedinium truncigerum (Deflandre, 1937) Kirsch, 1991,EA*30-31 Rigaudella apenninica (Corradini, 1973) Below, 1982, SW*33 Rottnestia wetzelii (Deflandre, 1937) Slimani, 1994, ssp. wetzelii Slimani, 1994; emend. Schi0ler et al., 1997, SW*49 Samlandia camarvonensis McMinn, 1988, SW*51-52 Samlandia mayii McMinn, 1988, SW*53, EA*46; 67 Senoniasphaera sp., SW*31 Spinidinium angustispinum in Wilson, 1974, SF*3, EA*47^8 Spinidinium echinoideum (Cookson & Eisenack, 1960; Lentin & Williams, 1976; emend. Sverdlove & Habib, 1974), SW*2 Spinidinium spp., EA Spiniferella cornuta (Gerlach, 1961) Sarjeant, 1970, SW

Spiniferites foveolatus Schi0ler, 1993, SW Spiniferites pseudofurcatus pseudofurcatus (Klumpp, 1953) Sarjeant, 1970; em. Sarjeant 1981, SW*48 Spiniferites ramosus granomembranaceus (Davey & Williams, 1966) Lentin & WilHams, 1973, EA*73-74 Spiniferites ramosus granosus (Davey & Williams, 1966) Lentin & WilUams, 1973, SF, EA*81 Spiniferites ramosus ramosus (Ehrenberg, 1838) Mantell, 1854, SW, EA*80 Spiniferites ramosus reticulatus (Davey & Williams, 1966) Lentin & WilHams, 1973, SW Spiniferites sp. Q of Schi0ler & Wilson, 1993, SW Spiniferites spp., SF, EA Spongodiniuml sp., SW*63-68 cf. Subtilisphaera pontis-mariae (Deflandre 1936) Lentin & Williams 1976, SF*4 Subtilisphaera spp., SW*16(?), EA*50(cf.) Surculosphaeridiuml longifurcatum (Firton, 1952) Davey et al., 1966, SW*60 Tanyosphaeridium spp., SW*56-57, EA*63 Tarsisphaeridium geminiporatum Riegel, 1974, SF*9(cf.) cf. Tectatodinium rugulatum (Hansen, 1977) Mc Minn, 1998, SF Trichodinium castanea Deflandre, 1935, SW*55, EA Trigonopyxidia ginella (Cookson & Eisenack, 1960) Downie & Sarjeant, 1965, SF*1, SW*75, EA Trithyrodinium evittii Drugg, 1967, SW*9(cf.), EA*5455 Trithyrodinium suspectum (Manum & Cookson, 1964) Davey, 1969, SW*10(cf.), EA*52-53 Trithyrodinium sp., SF, EA*76-77 Trithyrodiniuml cf. quinqueangulare Marheinecke, 1992, SW*11 Xenascus ceratioides (Deflandre, 1937) Lentin & Williams, 1973, SW*26 Xenikoon sp. A of Foucher & Robaszynski, 1977, SW*80

Acknowledgements RS. acknow^ledges a research grant from the Danish Natural Science Research Council and publishes with the permission of the Geological Survey of Denmark and Greenland. G.J.W. publishes with the permission of the Chief Executive Officer, IGNS, Lower Hutt. The WG leader is very thankful to the experts who accepted or requested samples from the Tercis Quarry: he learned from them that this fossil group was a fascinating one with extraordinarily well-preserved cysts able to give valuable and diversified stratigraphical information.