Bulletin de la Société belge de Geologie 97-3/4(1988) pp.287-319 Bruxelles 1990 Bulletin van de Belgische Vereniging voor Geologie 97-3/4(1988) pp.287-319 Brussel 1990

YPRESIAN ORGANIC-WALLED PHYTOPLANKTON IN THE BELGIAN BASIN AND ADJACENT AREAS by

J. DE CONINCK

(w ith 1 0 figures and 6 plates)

ABSTRACT

In the Y presian deposits of the Belgian basin about 315 species of fossil, organic-w alled phytoplankton have up to now been found. Among these we have selected forty easily recognizable species which appear to be biostratigraphically useful. Their distribution in the Ypresian deposits of the Belgian basin, visualized in a projection on the compound profile of the Kallo-Woensdrecht reference section, has served as a base for the definition of eleven zones in this reference section. Assemblages of organic-walled phytoplankton from several outcrops and borings in the basin allow to make correlations with the zones in the Kallo-Woensdrecht reference sec­ tion. This reference section can furthermore be correlated with sections in the surrounding basins of London, Hampshire, Dieppe, Paris, North Germany and Denmark, in which organic-walled phytoplankton assemblages had been described. From these correla­ tions appears that the Ypresian sequence is nearly complete in the Danish basin, the northern Belgian basin and the Hampshire basin. The zonation of the Ypresian deposits in the Belgian basin, which we have introduced here, is somewhat more detailed than the zonations h ith e rto defined in the surrounding basins. It should be em phasized how ever th a t all these zonations rem ain tools to w ork w ith and th a t they w ill be adapted again in response to the grow ing insights in th e changes of sedim entation and in the histo ry of the life com ­ munities during the Ypresian times. Key words: Ypresian, organic-walled phytoplankton, zonation, biostratigraphy, correlations, N.W. Europe.

SAMENVATTING

In de afzettingen van het Ypresien in het Belgisch Bekken werden tot nog toe ongeveer 315 soorten van fossiel phytoplankton met organische wand teruggevonden. Onder die soorten hebben wij er een veertigtal uitgekozen die men gemakkelijk kan herkennen en die vanuit biostratigrafisch standpunt nuttig blijken. Hun verspreiding in de Ypresienafzettingen van het Belgisch bekken, gepro­ jecteerd op het samengesteld profiel van de referentiesektie van Kallo-Woensdrecht, heeft ais basis gediend voor de bepaling van elf zones in die sektie. A ssem blages van phyto p lan k to n m et organische wand die voorheen w erden bestudeerd in verscheidene ontslui­ tingen en boringen in het bekken, stelden ons in staat korrelaties te m aken m et de zones in de referentiesektie van Kallo-W oensdrecht. Daarenboven kan men die referentiesektie korreleren met sekties in de omliggende bekkens van Londen, Hampshire, Dieppe, Pa­ rijs, Noord-Duitsland en Denemarken, waarin assemblages van phytoplankton met organische wand waren beschreven. Uit die kor­ relaties komt naar voor dat de Ypresien sekwentie in het Deense bekken, het noorden van het Belgisch bekken en het Hampshire bekken praktisch volledig is. De zonering van de Ypresienafzettingen in het Belgisch bekken, die wij hier voorgesteld hebben, is iets meer gedetailleerd dan de zoneringen die tot nog toe gedefinieerd werden in de omliggende bekkens. Men mag echter niet uit het oog verliezen dat gelijk welke zonering slechts een werktuig is voor toepassing in de stratigrafie, en dat ze steeds weer aangepast dient te w orden naarm ate de in zich ten in de veranderingen van de sedim entatie en in de geschiedenis van de leefgem eenschappen tijdens het Ypresian groeien. Sleutelwoorden: Ypresien, phytoplankton m et organische wand, zonering, biostratigrafie, korrelaties, N.W. Europa.

RESUME

Dans les dépots yprésiens du Bassin beige, environ 315 espèces de phytoplancton fossile, à paroi organique ont été retrouvées jusqu'à présent. Parmi elles, nous en avons sélectionné quarante qui sont facilement reconnaissables et qui paraissent utiles du point de vue biostratigraphique. Leur d istrib u tio n dans les dépôts yprésiens du Bassin belge, visualisée dans une projection su r le profil composé de la section de référence de Kallo-Woensdrecht, a servi de base à la définition de onze zones dans cette section. Les assemblages de phytoplancton à paroi organique que l'on avait étudiés auparavant dans plusieurs affleurements et sondages dans le bassin, ont per- m i de faire des corrélations avec les zones dans la section ae référence de Kallo-W oensdrecht. Par ailleurs, on peut corréler cette sec­ tion de référence avec des sections dans les bassins de Londres, Hampshire, Dieppe, Paris, Allemagne du Nord et Danemark, dans lesquelles des assemblages de phytoplancton à paroi orgnique avaient été décrits. Ces corrélations m ettent en évidence que la sé­ quence yprésienne est quasi complète dans les bassins du Danemark, du nord de la Belgique et du Hampshire. Notre zonation des dépôts yprésiens du Bassin belge, que nous avons introduite ici, est un peu plus détaillée que les zonations qui avaient été définies jusqu'à p résen t dans les bassins avoisinants. Il faut toutefois in sister su r le fait que to u te zonation reste un o u til dans le travail strati- graphique et qu'elle sera sans cesse adaptée en réponse à la compréhension grandissante des changements de la sédimentation et de l'histoire des communautés de vie durant l'Yprésien. Mots-clés: Yprésien, phytoplancton à paroi organique, zonation, biostratigraphie, corrélations, Europe du N.W.

Laboratorium voor Paleontologie, Rijksuniversiteit Gent, Krijgskan 281/S8, B-9000 Gent, Belgium. 288

Number of species probably reworked from the Paleocene : Chlorophyceae : — Dinophyceae : 6 Prasinophyceae : ? Acritarcha : ?

II. DIVERSITY OF THE ASSEMBLAGES IN THE SAMPLES The species diversity of fossilized Dinophyceae cysts produced at the time of sedimentation varies between about 25 and 65 in one sample ; it attains an average of nearly 40 species. The number of fossilizable Chlorophyceae species fluctuates bet­ ween 0 and 2. Prasinophyceae attain between 0 and 10 species in one sample, with an average of 5 species. Acritarcha diversity fluctuates between 0 and 15 species, with an average of 8 species per Fig. 1 sam ple. Localisation of borings and outcrops. When an increase of the diversity is observed it occurs in general as well in Dinophyceae as in Prasinophyceae and Acritarcha. That possibly means that the stressing circumstances which Richly diversified assemblages of organic-walled favoured cyst formation among dinoflagellate phytoplankton, especially of dinoflagellate cysts, species, also incited other phytoplankton groups to characterize the Ypresian deposits in the Belgian produce cysts (Acritarcha) or phycomae Basin. Their stratigraphical distribution in these (Prasinophyceae). deposits allows the definition of eleven zones. Some trends in the changes of diversity can be These are characterized by forty species with commented: in the Mont Héribu Member, the biostratigraphic significance in the basin. Our Clay of Orchies and part of the Roubaix Clay, below zonation is aligned with the ones proposed in the the Glauconitic bed of Tielt, the diversity of Ypre­ adjacent areas (Paris Basin, Hampshire-Dieppe sian Dinophyceae + Prasinophyceae + Acritarcha is Basin, London Basin, North Germany and somewhat higher in the samples from Quenast, D enm ark). Mons-Mont Héribu, Orchies, Overijse, Mons- Ghlin and St Maur, averaging about 65 species, I. TOTAL DIVERSITY OF FOSSILIZED compared with the diversity in the samples from ORGANIC-WALLED PHYTOPLANKTON corresponding levels in the Kallo- and Tielt boring IN THE YPRESIAN OF THE BELGIAN (DE CONINCK 1976a) and Knokke boring BASIN (DUPUIS et alii, in press) averaging about 40 (localisation of borings and outcrops : fig. 1) species. It is probable that cyst production among many species was optimally favoured in the rather Chlorophyceae : 3 species marginal parts of the bassin (Overijse, Orchies...) Dinophyceae : 235 species in comparison with more offshore areas (Kallo, Prasinophyceae : 30 species Tielt, Knokke). Such a positive effect on the diver­ Acritarcha : 45 species sity of cyst species is noted too in recent sediments Number of fossilized species which lived at the of e.g. the Dutch Wadden Sea (personal observa­ time of deposition : tions) which contain cysts which probably were carried in the wadden area by the flooding waters Chlorophyceae : 2 D inophyceae : 171 coming from the open sea. These waters are in fact Prasinophyceae : probably between 25 and 30 a mixture of North Sea water and estuarine Acritarcha : probably about 35 Schelde, Maas and Rijn waters carried northwards along the Dutch coast towards the wadden areas. Number of species reworked from the Jurassic: Higher in the Ypresian deposits (above the Chlorophyceae : — Glauconitic bed of Tielt), when comparing the Dinophyceae : 21 species diversity in samples from different Prasinophyceae : ? localities in the basin, the differences observed Acritarcha : ? seem fortuitous, not related to the place in the basin. When we compare in these higher ypresian Num ber of species reworked from the Cretaceous : deposits samples from successive levels at one Chlorophyceae : — locality (e.g. Kallo or M erelbeke or W oensdrecht) Dinophycea : 36 (DE CONINCK 1976a, 1977) we can observe here Prasinophyceae : ? and there some marked differences in the number Acritarcha : ? of species. This might suggest us that locally the environmental circumstances fluctuated more all (above the Glauconitic bed of Tielt), and in the suc­ over the basin, becoming from place to place ceeding Aalbeke Clay, Kortemark Silt, Egem Sand favourable for cyst production among more species and Clay of Merelbeke, Impagidinium is regularly during relatively short periods. But it could also found in most of the borings and outcrops studied correspond with a patchy distribution of these but frequencies remain low. In higher Ypresian microfossils in the sediment, as we see that in one deposits it becomes again very scarce. When we Stratigraphie level at one locality, Quenast (DE compare for the Kallo boring our observations with CONINCK 1986), samples a few meters distant WILLEMS' interpretation (WILLEMS 1980, Ph.D. from each other clearly give different values for the thesis) of the oceanic influence in the area of the diversity of species living at that same time of basin, we see some correspondance only at sedimentation (Quenast A3: 77 species; Quenast -283,5m and -280m where frequencies of A4: 69 species). Impagidinium attain 2% and at which levels WILLEMS indicated a marked influence from open sea. At other levels in the leper Formation where III. PALEOECOLOGICAL SIGNIFICANCE according to WILLEMS [ibid. ) an open sea influence OF SOME SPECIES clearly comes forward, no Impagidinium were — Apectodinium homomorphum (DEFLAN- however found ( -329.5 m, -315m and -303.9m). DRE & COOKSON 1955) is considered as a species To be really paleoecologically significant, the fre­ which lived in near-shore waters with lowered quencies of Impagidinium spp. should probably salinity (COSTA & DOWNIE 1976, p. 607). Its fre­ attain higher values. quency is high to relatively high in the lowermost — Pediastrumsp. is a freshwater Chlorophyceae Ypresian beds in the Tielt- and Knokke borings (DE species. It is nearly absent from the base of the CONINCK 1976a; DUPUIS et alii 1985) but drops Ypresian deposits to the top of the Egem Sands. It soon to sporadic occurrences (for instance at suddenly appears in the Clay of Merelbeke (Kallo Knokke) immediately above these lowermost beds. boring, Melle-Heusden borings, Torhout Pot- Up to the higher part of the formation, but still tebezemhoek) and is regularly observed further in below the Egem Sand the frequency remains near the Upper Ypresian deposits (Kallo, Woensdrecht, this zero level in the Kallo- and Tielt borings in Melle-Heusden, Egem Ampe). Apparently the areas situated at that time in rather offshore posi­ paleogeographic conditions changed after the tion. In equivalent deposits at Quenast, Mont sedimentation of the Egem Sands and were accom­ Héribu, Orchies, Overijse, Ghlin and St Maur panied by freshwater influx in many parts of the however the frequencies of A. homomorphum fluc­ basin. Perhaps some "wadden islands" developed tuate between 1 and 6 % ; in these rather marginal temporarily in the very shallow basin and produced areas of the Belgian Basin the influx of watermasses a freshwater vegetation among which Pediastrum, with lowered salinity carrying A. homomorphum, which was transported into the sea (?). was apparently important. It maybe the reason too why relatively more species of the phytoplankton produced cysts (see Trends in the changes of diver­ IV. TRENDS IN THE DISTRIBUTION sity) in these parts of the basin in comparison with OF REWORKED SPECIES the areas of Kallo, or Tielt situated more offshore. We are going to consider here the reworked A. homomorphum comes back at Kallo, Tielt and dinoflagellate species only, not the eventually Heestert in the upper part of the Aalbeke Clay or reworked Prasinophyceae and Acritarcha. Species in the Kortemark Silt and remains well represented reworked from Paleocene deposits have only been in the Egem Sand, for instance at Kallo, Merelbeke encountered in the Mont Héribu Member at and Egem. Its frequency can attain high values such Orchies, St Maur, Mont Héribu and Quenast. as 8 till 9 or even 20 % (at Kallo - 259 m). Higher, Among the Mesozoic species, those reworked in the Clay of Merelbeke, the species is well from the Jurassic are rather restricted to the Mont represented in the Kallo boring and especially in the Héribu Member, the Orchies Clay and the lower Woensdrecht boring, but absent in the Melle- part of the Roubaix Clay below the Glauconitic bed Heusden borings. It is not clear to me how from of Tielt, while those reworked from the Cretaceous these data, the distribution of watermasses could are present from the Mont Héribu Member up to be sketched in the period following the deposition the base of the Egem Sand. They are found all over of the Glauconitic bed of Tielt. th e basin. — Impagidinium spp. are considered to be When counted together, the procentual frequen­ indicators of oceanic watermasses (WALL et alii cies of the reworked Jurassic and Cretaceous 1977, p. 168). In the low erm ost part of the Ypresian species average about 5% in the Mont Héribu deposits they have been found sporadically, only in Member and the Orchies Clay, below our the Knokke boring. At a biostratigraphically Eatonicysta ursulae zone (see the proposed zona­ somewhat higher position in the Mont Héribu tion under V), but can attain 10 % (Kallo - 337 m, M em ber Impagidinium was strange enough only Orchies; Ghlin, St. Maur) or exceptionally 18% encountered at Overijse, Ghlin, St. Maur situated (Mont Héribu). From the base of the Roubaix clay more near the border of the basin, and in the suc­ [Eatonicysta ursulae zone) up to the top of the ceeding massive clay packet at Tielt ( - 125.5m), Kortemark Silt, the frequencies of both species situated more offshore, each time very groups together average about 2.5 %. In the higher sporadically. In the upper part of the Roubaix Clay deposits reworked species were almost never 290

G» Ul 3 io g g E E a i 3 io 3 ZONATIuN OF THE YPRESIEN IN THE BELGIAN g •H 4 4 E XI 3 3 3 3 T l 4 4 • 0 E IO 4 G Ul 3 W io 3 G G — T l G G ifl c 0 G 3 G IO IO E ■H •C c —1 4J io (0 3 •H IO a i G E •G —1 Ul IO Ul ( 0 G G 3 Ul 44 a i io Ul X! C — G •rH G O -G G BASIN WITH ORGANIC WALLED PHYTOPLANCTON 3 —1 en IO (O 3 CU 'G 3 G C m C (0 ra Ul IO C 3 •H -H •H 3 •H G G G ■G o Ul U CnTI U 01 IO a i g (0 4J G o u a i G > G E Cri >4 C C 0 IO G CU CU O > 1 c C 3 IO •G B E Tl G u io a i g -G G O a i O 3 c IO io IO E •H G a i G G Ul Ul G G a i 3 G G G IO O IO . - I a i (0 U 0 4 m C n O 14 g a i E a i T t O G g Cl 3 a CU G m O Ul a i 44 c CU G e O E U C M•G 1-4 M m Xi a i 3 IO •H »H0 io en c Ul o IOG E E a i T) •G 0 a i E c i IO d ) 44 -G io a i G 0 ) 0 - 4 g g 1-4 E T ) I—1-1 a i N Cl i0 Tl i—1 Ü O 3 C Tl G Ul 3 G e C Ul tji g a a i 44 Ul a i 3 3 g ■H 3 -H 3 -1 •H G io E E >i IÖ E rH -G G C -G 3 projected on the Kallo and ‘H •H G > , v o Ul a -h •H 3 g •H 1-4 Ul m Cl g G E 0 3 E e n O Tl G E IO a i t ) IO 0 -1 E •G G G IO Ul g a i m C Tl •H •H C 0 M CU IO 3 IO O G •H m G G ■G G 3 G Tl -G G G 3 C Woensdrecht reference sections. G (11 -H IO IO g >4 IO •G -H T> Ul -H Ul 3 > •H H c u T ) i—1 IO 'G U IO CU-G G CU IO -G •G O »0 g G U G T l (4 *G ■ a E Xi U —1 g •G G G (0 E a i Ul T l IO u i a i G T l T l IO -H IO 3 o m 0 'H 0) 3 g •H E i0 3 E *H o 3 G ü a i 3 m E •rH G •G IO o m -g •G -G (0 X -1 •g g • i io g G io a i 3 g 3 G •G 3 Cl io 44 •H G IO io •G G 3 E G Ul m G E -4 G G Ul 0 1 > , G c CU G •r4 c u a i g IO•H 0) •rH Ul 1-4 ■H a i •H o 3 C IO G C CU -G 3 a i c u c u -g g a i a i (0 d a ® •H •r4 a i > •H CU C U G c c u c >iX) C IO > G ‘H IO •rH c u •rH 01 C G n) u O u i o a i io a g IO O •H T3 U l -H O Ul o Ul D.-H o *G U > 1- H G o U T l ü T) Ul O T ) o •rH G G o C 0 O - G G o o c C! -H 0 U l G rH Ul c 0 Ul T3 C T l •H Ul T l CU- 4 ■rH 0 O C O 1-4 O C T l Ul CU G •G G G r- CU C POSITION OF THE MEMBERS Z o n a tio n "0 (0 O a i 44 m a i a i io io 44 0 0 (0 O c G o Ul a i G G G IO •H a i G •H •H IO u i g t ) a i ■G Ul m 3 1—1 t j l N U G N Ul i—1 x i io i—1 U G ü o 0 u > 1 u i G d) a rH G Ul U > C ■G o a i •G G U 0 G M-l -G 44 Ul U l IN THE ZONATION d; 4-1 0) <0 44 Ul io C 1 i i0 G io G E IO <—1 G IO g G Ul a i —i *rH T l 0) G X CU 3 4 G G Ul C l G a i a . . c a i ■ H X X D io >4 G Ul IO 0 g O •H Í1 U •rH IO 3 •G CU 3 c u ai G ai > 1 g IO -G G Cu û f n S i Î H S X H CL.

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Fig. 2 Stratigraphie distribution of biostratigraphically useful species and proposed zonation. 291

recorded. From this trend we can conclude that ero­ distribution of these species in the Ypresian sion of Mesozoic deposits around the Belgian Basin desposits of the Belgian Basin is projected on the was more pronounced in the earliest times of the combined sections of the Kallo boring for the lower Ypresian than later in the Lower Ypresian, and that members up to the Merelbeke Clay and of the it almost stopped around the time when the Woensdrecht boring for the Merelbeke Clay up to sedimentation of the Egem Sand started. the Vlierzele Sand. From one area to another in the Belgian Basin the boundaries between the zones V. SPECIES WITH RESTRICTED may vary slightly with respect to the boundaries STRATIGRAPHIC DISTRIBUTION between the members (see VI, and fig. 9). IN THE BELGIAN BASIN 1. Pseudomasia trinemaZone Selection of biostratigraphically useful species This zone represents the lowermost part of the (fig- 2 ). Ypresian deposits in the Belgian Basin. The In DE CONINCK (1981, table 1) some forty acritarch P. trinem a DE CONINCK 1969 is chosen species are retained as useful tools for because it is easily recognisable and in the Belgian biostratigraphic correlations in the Ypresian Basin it has until now been encountered in the deposits only, and at the scale of the only Belgian lower part of the Ypresian sequence only and never Basin. Some of these species have been found in in older deposits. In the zone one occasionally finds Paleocene deposits and are still encountered in the Wetzeliella astra COSTA, DENISON & DOWNIE low er part of th e Y presian sequence (e.g. D eflan­ 1977. The upper lim it of the zone is defined by the drea phosphoritica, Alisocysta margarita, Apec­ appearance of Wetzeliella meckelfeldensis todinium hyperacanthum and Thalassiphora GOCHT 1969 and/or Kisselovia crassoramosa delicata ) ; or they left temporarily the Belgian Basin (WILLIAMS & DOWNIE 1966). In the P. trinem a and came back later in the Ypresian (e.g. Zone some other species which in other basins Thalassiphora pelagica, Phthanoperidinium have been found in older deposits too are worth crenulatum, Homotryblium sp., Polysphaeridium mentioning: Deflandrea oebisfeldensis ALBERTI zoharyii, Apectodinium homomorphum...). O ther 1959, Trigonopyxidia ginella (COOKSON St species are encountered in relatively short parts of EISENACK 1960), Thalassiphora delicata the sequence, in for instance the lower Ypresian WILLIAMS & DOWNIE 1966 and Apectodinium deposits, disappear temporarily and come back hyperacanthum (COOKSON & EISENACK 1965). near th e top of the Ypresian (e.g. Adnatosphaeri­ From observations in lower Ypresian deposits from dium robustum) or even later in th e L utetian (e.g. the Rockall Plateau (BROWN & DOWNIE 1984) it Phthanoperidinium crenulatum). It is quite certain seems that W. astra appears somewhat prior to P. that the presence or absence of these species dur­ trinem a. ing parts of the Ypresian time in the Belgian Basin must have been linked to the shifting distribution 2. Wetzeliella meckelfeldensis — of particular watermasses in which these species Kisselovia crassoramosa Zone produced cysts or to which they were restricted. Not only the Belgian Basin m ust have been affected At the base of the zone both W. meckelfeldensis by such a changing distribution of watermasses but and K. crassoram osa appear approximately also the adjacent areas. Hence it is normal that the together. K. crassoramosa seems restricted to this 'more the synchrone sequences are distant from zone. Pseudomasia trinema can still be found as each other or separated by paleogeographic barriers, well as the other species mentioned in the first the more the stratigraphie distribution of several zone. Thalassiphora pelagica (EISENACK 1954) species will differ from one area to another. Only which had left the basin near the end of the Thane- the most tolerant thus the more pronounced tian comes back in this zone. The top of the zone cosmopolitan species will be suitable for is defined by the come back of Phthanoperidinium biostratigraphic correlations on a large scale. More crenulatum (DE CONINCK 1976) which was data must however be assembled before selecting already present in part of the Thanetian deposits species combining a restricted stratigraphical (HEILMANN-CLAUSEN 1985, p. 25) in Denmark distribution and a marked cosmopolitan character and SE England. Proposal of a zonation of the Ypresian deposits 3. Phthanoperidinium crenulatum Zone in the Belgian Basin with organic-walled phytoplankton P. crenulatum is found at the base of the zone A few zonations whith organic-walled in company of Adnatosphaeridium robustum phytoplankton covering the Ypresian exist already : (MORGENROTH 1966) and Kallosphaeridium they take into account the dinolagellates (BUJAJK brevibarbatum DE CONINCK 1969. In the zone et alii 1980) or only one group of them, the we note the last occurrence of P. trinema, Wetzeliellaceae (COSTA & DOWNIE 1976, Trigonopyxidia ginella a n d W. astra. COSTA & MULLER 1978, CHATEAUNEUF & Thalassiphora pelagica remains present and will GRUAS-CAVAGNETTO 1978). In the zonation be found in the younger zones too. The top of the proposed here we have used 34 dinoflagellate cyst P. crenulatum Zone is defined by the first species, 3 species of acritarchs and one appearance of Dracodinium simile (EISENACK Chorophyceae species. In fig. 2 the stratigraphie 1954). 292

4. Dracodinium simile Zone EATON 1976. D. spinigerum, P. zoharyii, H. Together with the appearance of D. sim ile at the granulatum, K. clathrata, H. pallidum (?), E. base of this zone we note the first Phthanoperi­ u rsu la e , P. e c h in a tu m an d S a m la n d ia dinium echinatum EATON 1976. P. crenulatum chlamydophora remain present. W ithin the zone and K. brevibarbatum are still present. A. Apectodinium homomorphum, w h ic h is ro b u stu m leaves the assemblages near the top of sporadically present in the lower zones, becomes the zone while Thalassiphora delicata, w ith o u t more frequent. The top of the K. aff. clathrata Zone disappearing, becomes very scarce. The top is defined by the appearance of Areosphaeridium of th e Dracodinium simile Zone is defined by diktyoplokus (KLUMPP 1953). the first occurrence of Eatonicysta ursulae (M ORGEN RO TH 1966). 9. Areosphaeridium diktyoplokus Zone Together with the appearance of A. 5. Eatonicysta ursulae Zone diktyoplokus at the base of the zone we encounter Together with the appearance of E. ursulae at for the first time Spinidinium aff. essoi COOKSON the base of the zone we note the come back of & EISENACK 1967, P e d ia s tr u m sp., Homotryblium (probably H. pallidum) which had Pulvinosphaeridium sp., Cerebrocysta bartonensis already been observed in Upper Thanetian deposits BUJAK 1980 (sporadically) and Pyxidinopsis (DUPUIS & GRUAS-CAVAGNETTO 1985 and densepunctata DE CONINCK 1985 (= Tec­ DUPUIS et al., in press), and the appearance of tato d in iu m sp. in DE CONINCK 1977 or P yx­ Dracodinium solidum GOCHT 1955. P. idinopsis sp. 1 in DE CONINCK 1981). P. zoharyii crenulatum disappears in the base of the zone and leaves the basin temporarily at the base of the zone will temporarily come back in the Lutetian. D. and will appear again in the following zone. sim ile and D. solidum disappear near the top of the Pulvinosphaeridium sp. and S. aff. essoi disappear zone. K. brevibarbatum and P. echinatum rem ain well below the top of the zone and K. clathrata, T. resent. The top of the E. ursulae Zone is defined galatea and A. homomorphum near the top. P. y the appearance of Dracodinium varielongitu- echinatum, E. ursulae, H. pallidum (?), H. d u m (WILLIAMS & DOW NIE 1966). granulatum, D. spinigerum, K. aff. clathrata, S. chlamydophora and A. biformoides remain pre­ 6. Dracodinium varielongitudum Zone s e n t and Impletosphaeridium rugosum MORGENROTH 1966 appears in the lower part of Together with the appearance of D. the zone. The top of the A. diktyoplokus Zone is varielongitudum at the base o f the zone we note the defined by the appearance of Paucilobimorpha come back of Polysphaeridium zoharyii triradiata DE CONINCK 1986. (ROSSIGNOL 1962) which was already encountered in Upper Thanetian deposits in the 10. Paucilobimorpha triradiata Zone Knokke boring (DUPUIS et ah, in press). Hystrichokolpoma granulatum EATON 1976 and P. triradiata ( = Incertae Sedis B and C in DE Kisselovia clathrata (EISENACK 1938) [which cor­ CONINCK 1976a, b, 1977, 1985) appears at the responds quite certainly to K. coleothrypta base of the zone. Its frequency remains however (WILLIAMS & DOW NIE 1966)] m ake th eir first very low. P. zoharyii which had temporarily left the appearance. K. brevibarbatum disappears in the basin during deposition of the former zone comes lowermost part of the zone, while D. back, but rather sporadically. E. ursulae, H. varielongitudum disappears near its top. P. pa llid u m (?), H. granulatum, D. spinigerum, S. echinatum, H. pallidum (?) and Eatonicysta chlamydophora, A. biformoides, A. diktyoplokus, ursulae remain present. Tne top of the D. C. bartonensis, P. densepunctata and I. rugosum varielongitudum Zone is defined by the appearance remain present. K. aff. clathrata and Pediastrum of Ochetodinium romanum DAMASSA 1979. rarify near the base, then disappear. Together with P. triradiata appears W. aff. articulata EISENACK 7. Ochetodinium romanum Zone 1938 sen su CHATEAUNEUF & GRUAS- CAVAGNETTO 1978 ( = W. articulata — ovalis in O. rom anum appears at the base of the zone DE CONINCK 1977). The top of the P. triradiata together with Diacrocanthidium spinigerum DE Zone is defined by the appearance of CONINCK 1969. P. echinatum, H. pallidum (?), Litosphaeridium ? m a m ella tu m DE CONINCK E. ursulae, H. granulatum and P. zoharyii rem ain 1977. present while K. clathrata becomes more frequent. Samlandia chlamydophora EISENACK 1954 11. Litosphaeridium? mamellatum Zone appears within this zone. O. rom anum disappears at the top of the zone which is defined by the L. I m a m ella tu m appears at the base of the zone. appearance oí Kisselovia aff. clathrata (EISENACK Phthanoperidinium comatum (MORGENROTH 1938) [sensu DE CONINCK 1976a). 1966) which was encountered very sporadically in the A. diktyoplokus zone and the P. triradiata zone 8. Kisselovia aff. clathrata Zone becomes now rather frequent. H. granulatum, P. zoharyii, S. chlamydophora, A. biformoides, A. Together with the appearance of K. aff. clathrata diktyoplokus, C. bartonensis, P. densepunctata, 1. (sensu DE CO N IN CK 1976a) at the base of the zone rugosum, P. triradiata and W. aff. articulata (sensu we note the appearance of Turbiosphaera galatea CHATEAUNEUF & GRUAS-CAVAGNETTO 293

L e g e n d

, 2onr Members

Zone boundaries -Biostratigraphic position \altitude * within lim its ot precision \ ( T A W 1

30,2

P o p e rm q i

12,5

F’ !5

rssr

27,5 Conglc

W oensdrecht- 1 K a llo Fig. 3 Biostratigraphic correlations within the Belgian Basin with the Kallo-Woensdrecht reference section.

1978) remain present. In the zone disappears E. localities situated near the southeastern border of ursulae w hile H. pallidum (?) and D. spinigerum the basin, the transgression started at the time of rarify or disappear temporarily .The top of the zone deposition of the Wetzeliella meckelfeldensis — is defined by the appearance of Dracodinium Kisselovia crassoramosa Zone, thus a little later pachydermum (CARO, 1973). The transition Ypre- than at Kallo, Tielt or Knokke. At Quenast, sian/Lutetian is probably situated near the top of situated somewhat more centrally, the th e zone. microdioritic intrusion on which the Ypresian deposits were laid down, formed probably an island during the times when sediments of the Pseudomasia trinema Zone and the Wetzeliella VI. BIOSTRATIGRAPHIC POSITION OF meckelfeldensis — Kisselovia crassoramosa Zone THE YPRESIAN DEPOSITS IN THE were deposited in the surrounding sea. The BELGIAN BASIN volcanic intrusion m ust have been submerged and The assemblages of organic-walled microfossils reduced to some rocks in the Ypresian sea from the studied in the Ypresian deposits in several outcrops time when deposits of the Phthanoperidinium and borings in the Belgian Basin (fig. 1), m ake crenulatum Zone were found. biostratigraphic correlations possible with the zones in the combined reference section of the B. Some higher levels in the Ypresian sequence Kallo and W oensdrecht borings (fig. 3). 1. THE ROUBAIX CLAY. Apart from the Roubaix Clay in the Kallo, Ooigem and Tielt bor­ A. The base of the Ypresian deposits at Kallo, ings, this unit was studied near its type area at Tielt, Knokke, Overijse, Quenast, Mont Héribu Lauwe Knok in an abandoned claypit of the and Orchies "Céramiques et Briqueteries du Littoral". A sam­ In the borings of Kallo, Tielt and Knokke the ple, taken by MOORKENS in 1968 at about 4m base of the Ypresian deposits corresponds with the below a silty bed with numerous Turritella Pseudomasia trinema Zone which is grosso modo specimens, contains an assemblage of organic- the equivalent of the Wetzeliella astra Zone walled microfossils which has an intermediary defined by COSTA, DENISON & DOWNIE (1978). composition between the ones found in the Kallo In these localities of the northwestern part of the boring at -307 m and at -303,9 m, respectively Belgian Basin the transgression was almost syn­ below and above a glauconite level at -305 m chrone. At Overijse, Mont Héribu and Orchies, (Glauconiferous Bed of Tielt) (cf. DE CONINCK 294

1976b). The same sample from Lauwe Knok was the Kallo boring. Here again both microfossil studied by STEURBAUT (STEURBAUT & NOLF, groups suggest the same correlation. 1986). The calcareous nannofossil assemblage c) Steenhuize-Wijnhuize which he recovered corresponds more to the one at Kallo -301,5m than that at -304,6 m. It is cor­ In a boring of the Belgian Geological Survey related with in the base of the zone IV proposed by at Steenhuize-Wijnhuize (about halfway Ronse and STEURBAUT (ibid.). The transition between Aalst) the Sands of Mons-en-Pévèle were studied at zone Illb and zone IV is situated at Kallo between about 4,5 m below the local Aalbeke Clay - 304,6 m and - 301,5 m while the transition bet­ (VANHOVE, in prep.). The organic-walled w e e n th e E. u rsu la e Zone and the D. microfossils suggest a correlation with the E. varielongitudum Zone is situated at Kallo between ursulae zone at Kallo. STEURBAUT (ibid., 1986) - 307 m and 303,9m. From the study of both the has studied the calcareous nannofossils near the organic-walled microfossils and the calcareous nan- same level and can correlate the assemblage whith nofossils we are inclined to correlate the Lauwe his zone Illb (= lowermost part of NP12 Zone). sample with a part of the sequence at Kallo between From these data we can conclude that this level in -304,6m and -303,9m, in the middle of the the Steenhuize-Wijnhuize boring can be correlated Roubaix Clay encountered in that boring. with the uppermost part of the E. ursulae Z one at R em ark : As we shall see later, when correlating the Kallo. deposits in the Belgian Basin with those in the sur­ Conclusion : The Sands of Mons-en-Pévèle in the rounding basins, there exists probably a gap in southern part of East Flanders correspond for a large sedimentation in the Kallo area at the level of the part to (the upper part of) the E. ursuale Z one at Glauconiferous Bed of Tielt. Elsewhere in the Kallo, thus to the middle part of the local Roubaix Belgian Basin the corresponding sedimentary gap Clay. At the type locality Mons-en-Pévèle the sam­ may be more or less pronounced. It is probable that ple in the lower part of the unit corresponds to the in the Lauwe area the level studied corresponds to same middle part of the Roubaix Clay at Kallo. It a part of the sedimentary gap at Kallo. is possible that the higher parts of the Sands of Mons-en-Pévèle outcropping in the hill 2. THE SANDS OF MONS-EN-PEVELE have immediately to the northwest of the village of been studied at the type-locality, also in the Mons-en-Pévèle correspond to the higher part of the southern part of East Flanders, namely at Ronse Roubaix Clay at Kallo as well as in its type area. "Waaienberge" and at Steenhuize-Wijhuize. 3. AALBEKE CLAY. Apart from the Aalbeke a) Mons-en-Pévèle Clay in the Kallo boring, this unit was studied (DE A sample was taken by GEETS (doc­ CONINCK, 1976c) in a claypit situated at about torate thesis 1969) near the road from Mons-en- 1 km to the southeast of the center of Aalbeke, near Pévèle to Bersée, at a point situated about 1 km to the road from Aalbeke to Rollegem. The sample the east of the center of Mons-en-Pévèle. It comes studied was collected by GEETS (doctorate thesis, quite certainly from the lower part of the unit 1969) at 8,5mbelow the surface (at 43,5mT.A.W.). which rests there on the Orchies Clay. The Further research on organic-walled microfossil assemblage of organic-walled microfossils, studied assemblages from the Aalbeke Clay was done by by VANHOVE (in prep.), suggests a VLERICK (licentiate thesis, 1982) in a claypit at biostratigraphic correlation with the upper part of Heestert-Kwadestraat and by VANHOVE (in prep.) the E. ursulae Zone at Kallo. STEURBAUT, after in the boring at Steenhuize-Wijhuize. In all these studying the calcareous microfossils in the same studies of the Aalbeke Clay in its type-area and in sample of the Mons-en-Pévèle Sands (STEURBAUT the southern part of East Flanders, only the upper & NOLF, 1986), made a correlation with his part of the unit was investigated. The assemblages zone Illa in the Kallo boring ( = uppermost part of of dinoflagellates encountered in that upper part of the NP11 Zone) which corresponds to the upper the Aalbeke Clay in the southern part of the Belgian part of the E. ursulae Zone. Both microfossil groups Basin are comparable to these in the upper half of suggest thus the same correlation. the O. ro m anum Zone at Kallo, but in that boring b) Ronse “Waaienberge” the upper half of this zone is situated in the lower part of the local Kortemark Silt just above the local Two samples taken in the talud of an old Aalbeke Clay. The fact that the same upper half of railway cutting come from clayey sands with num- th e O. ro m anum Zone is found in the lower part mulite accumulations respectively at about 7 m of the Kortemark Silt in the Kallo boring and in the and 5 m below the local Aalbeke Clay at the top of upper part of the Aalbeke Clay in its type-area the talud. The assemblages of organic-walled illustrates the slight diachronism of the boundary microfossils studied by VANHOVE (in prep.) allow between both lithostratigraphic units when dif­ to make a biostratigraphic correlation with the ferent areas of the basin are compared with each upper part of the E. ursulae Zone in the Kallo bor­ other. ing. The same sands, studied again at about 7 m below the Aalbeke Clay, contain calcareous nan- 4. THE EGEM SANDS — MERELBEKE CLAY nofossils studied by STEURBAUT (STEURBAUT TRANSITION AT KALLO OR THE EGEM & NOLF, 1986) who proposes a correlation with his SANDS — PITTEM CLAY TRANSITION AT zone Illa ( = uppermost part of the NP11 Zone) in EGEM. In both localities a rather superficial 295

investigation of the changes of assemblages from higher deposits beyond the Ypresian-Lutetian tran­ the lower unit to the overlying one suggests that sition up to - 375 m in the Woensdrecht boring. We there may exist a sedimentary gap at this transi­ can conclude from this information that the upper tion. The number of samples covering that transi­ lim it of the Vlierzele Sands (i.e. the Aalterbmgge tion is in both cases however too small to be able Complex) becomes younger when going from the to evaluate such an eventual gap, if any. Further central area of the Belgian Basin towards its nor­ studies to elucidate the eventual existence of a thern part. sedimentary gap at the top of the Egem Sands and its importance at Kallo on the one hand, at Egem on the other hand, or eventually elsewhere in the VII. BIOSTRATIGRAPHIC POSITION OF THE basin, are in progress. YPRESIAN DEPOSITS IN THE ADJACENT BASINS 5. THE TRANSITION OF THE VLIERZELE A. London Basin SANDS TO THE OVERLYING AALTER SANDS AT HEUSDEN. The Vlierzele Sands — Aalter Several correlations between the Ypresian Sands transition was studied at Heusden (DE CON­ deposits in the Kallo-Woensdrecht section of the INCK, 1976c) in a boring about 6 km to the east of northern Belgian Basin and sections through the the center of Gent, halfway between Destelbergen Ypresian deposits in the London Basin are proposed and Laarne. We were able to demonstrate, after stu­ in fig. 4 (lithostratigraphy according to KING dying the organic-walled microfossil assemblages, 1981 & 1984 and HAWKINS 1955). They are based that the local top of the Vlierzele Sands corresponds on the first appearance or on the top of the range approximately to - 415 m in the Woensdrecht bor­ of some dinoflagellate species which are ing studied at the m ean tim e (DE C ONINCK 1977). encountered in these deposits. The overlying local Aalter Sands correspond In the western part of the London Basin informa­ approximately to - 375 m in the Woensdrecht bor­ tion is available on the succession of dinoflagellate ing. From this observation appears that an impor­ species in a few borings of the Enborne Valley : The tant sedimentary gap exists in the region of Baughurst boring n° 2 was described in HAWKINS Heusden between the local Vlierzele Sands and the (1955, pp. 409-430, text-fig. 6 ) and in KING (1981, overlying Aalter Sands. That gap corresponds pp. 67-69, text-fig. 21); its dinoflagellates were grosso-modo to the upper part of the P. triradiata studied by ISLAM (1983, pp. 74-75, text-fig. 2). The Zone, to the L. ? m a m e lla tu m Zone and to some Enborne boring n° 11 was figured by HAWKINS

Zones 'Members] W num. j 0

E m a m Vlierzele N

Puur trir 5 0

R

E A r e o s u h C d ik t (KING) H 5 h a p l e y - H e a th W n tp r Fm "Lyguiar T,. (KING)

Up B a q s h i ' E g e r B e d s , K iss (KING) (HAWKINS) Mid B a g stJ ft* a l t B e d s 1 c l a t h M id °'o,0c Oiv n Onp 0,0 *Qr '-0ng B e d s o* 0 ' q3 T i 1 1 1 1 1 i 1 1 B a g s h o l B e d s 'SSci°lhr. CS"H> O c h re m D iv E first Hystr granulata ^ ______C°'e°'V Í - " f i r s t Drac.varieiong. &7fyst, g r a n u la te

O ivD

U p p e r S ilt

D ivC

(KING) Div B ninnii] first. Orae D ra c .s tm Div ñ D iv 8 S t ilt ' ~ c l a y s f i r s t HomoUybl ] O rc h ie s Div A j first W etz.m eckeli. & Kiss crassoram osa T ile h u rs t L o w er S ilt M br O ld h a v e n Id h av

B a u g h u r s t ( E n b o r n e H e r n e B a y s i e o l W oensdrecht- b o r i n g 2 1 b o r i n g 11 S h e p p e y K a l t o

W estern London Basin Eastern London Basin Northern Belgian Basin

Fig. 4 Biostratigraphic correlations between London Basin sections and the Kallo-Woensdrecht reference section. 296

(1955, text-fig. 4) and its dinoflagellates were coleothrypta and H. granulata w hile D. sim ile studied by G.L. WILLIAMS and DOWNIE (in disappears. In the Isle of Sheppey section one notes DAVEY e ta l., 1966, pp. 20-27, table 1, text-fig. 7). th a t D. varielongitudum and H. granulata appear From an outcrop at Shapley-Health, a little more probably near the middle of Div. C while to the east, some information (ISLAM 1983, text- K. clathrata-coleothrypta appears near the middle fig. 3, p. 75), can be used. of Div. D and D. sim ile disappears around the base In the eastern part of the London Basin the sec­ of Div. E. From this picture one can conclude that tions at Isle of Sheppey and at Herne Bay have been the upper part of Div. C and probably the whole retained. At Isle of Sheppey the deposits are Div. D were deposited in the eastern London Basin described in KING (1981, pp. 52-54, text-fig. 15) and while at Kallo in the northern Belgian Basin the in KING, 1984. ISLAM (1984) studied the sedimentation was very slow if not interrupted. dinoflagellate assemblages. The Herne Bay section During this lapse of time the glauconitic level at is described in KING (1981, pp. 54-56, text-fig. 22) Kallo - 305 m was formed. This glauconite horizon and information about the appearance of some has been correlated with the one recorded at Tielt Wetzeliellaceae spp. was found in COSTA & - 101,5m and called Glauconiferous Bed of Tielt DOW NIE (1976, p. 600). (DE CONINCK, 1976a, p. 27). When we correlate this part of the sequence at Isle COMMENTS of Sheppey with the one in the Baughurst boring in the western London Basin we see that at Baughurst • Basal Ypresian deposits the corresponding sequence is much thinner and T he P. trinem a Zone in the lowermost part of situated in the lower part of Div. E (in the middle the Ypresian sequence at Kallo in the northern of the Bagshot Beds sensu HAWKINS, 1955). Belgian Basm corresponds with the lower part of If these lithostratigraphical and biostratigraphical the London Clay Div. A i (Walton Member) in the interpretations are correct, there exists a marked London Basin. It is grosso modo the equivalent of diachronism between the Divisions C, D and E in the W. astra Zone defined by COSTA, DENISON the eastern and western London Basin. In the & DOW NIE (1978). P. trinem a has been recorded eastern London Basin the upper part of Div. C and as Gen. et sp. indet. III by BROWN Si DOW NIE the whole Div. D correspond then biostrati- (1984, text-fig. 2) shortly higher than the earliest graphically with the lower part of Div. E in the appearance of W. astra in the Rockall area western London Basin. (N. Atlantic). • The K. aff. clathrata Zone In the London Basin the London Clay Div. Ai (Har­ wich Member and Swanscombe Member) are older In the Kallo boring (northern Belgian Basin) th an the P. trinem a Zone at Kallo, and older than th e K. aff. clathrata Zone corresponds with the the W. astra Zone. This Div. Ai and equivalent upper half of the Kortemark Silt and with the Egem deposits in the North Sea Basin are characterized Sand. At the base of this zone appear the first by the presence of volcanic ash deposits and T. galatea. At Isle of Sheppey (eastern London marked by peaks in the frequency (acme) of D eflan­ Basin) T. galatea appears in the upper part of Div. E. drea oebisfeldensis (KNOX Si HARLAND, 1979, At Kallo the top of the zone is marked by the regular pp. 465-466). They can however not be much older appearance of A. diktyoplokus in the overlying than the P. trinem a Zone. Indeed, relatively high deposits (Merelbeke Clay, Pittem Clay,...). At Isle frequencies of D. oebisfeldensis are noted in the of Sheppey A. diktyoplokus is recorded in one sam­ basal eighty cm of the Ypresian deposits in the ple only, situated at the top of Div. D. The species Kallo boring just below the first record of is however absent in the following Div. E and in the P. trinem a, and also in the basal four metres of the palynomorph bearing samples in the basal part of Ypresian sequence in the Knokke boring (Belgian the overlying Virginia Water Formation. For that coast) w here P. trinem a has been found only once reason I suppose that the uppermost part of Div. E at four metres above the base fo the Ypresian and at least the lower levels of the Virginia Water sequence (DUPUIS et al., in press). These data sug­ Formation at Isle of Sheppey are the equivalent of gest that the Zone with the D. oebisfeldensis acme some part of our K. aff. clathrata Zone at Kallo. situated in the London Clay Div. Ai, may even­ In the western London Basin sections no species tually correspond with the lowermost Ypresian have been mentioned which allow to decide deposits in the north-(western) Belgian Basin. whether the equivalent of our K. aff. clathrata Zone Further research is however needed before this can was deposited or not. be confirmed. • The A. diktyoplokus Zone, P. triradiata Zone • The E. ursulae Z one — D. varielongitudum and L. ? m am ellatum Z one Zone transition In the eastern London Basin sections at Isle of In the northern Belgian Basin (Kallo boring) it Sheppey and Herne Bay deposits corresponding seems that the sedimentation nearly stopped bet­ w ith our A. diktyoplokus Zone up to the w e e n th e E. u rsu la e Zone and the L. ! mamellatum Zone can not be indicated with D. varielongitudum Zone. Indeed, the following certainty. In the western London Basin sections we difference is seen between Kallo and Isle of Shep­ can only try a correlation of the outcropping Mid­ pey : At the base of the D. varielongitudum Zone dle Bagshot Beds at Shapley-Heath with the at Kallo appear D. varielongitudum, K. clathrata- Woensdrecht section in the northern Belgian 297

FISHER] EATON Fig. 5 Biostra tigraphic coirela tions XIX between the White Cliff section 19 (Isle of Wight-Hampshiie Basin) and the Kallo-Woensdrecht reference section. XVIII XVII □ XVI _ %v= XIII * !i

VIII vir

10 VI

Z o n e s M em bers W

0 Lit.? g a ra n ce 0f Ph r E m am . Vlierzele N ------IV Pauc.trir. S D iii u _ R E Pittem A reosph. C dikt. H

Merelbeke T_

O f n KING ; - % c . „ E gem Div. D " Fffe/ g Kiss, aff. clafh.

Kortemark

Div.C Och.rom . Aalbeke

Drac.var. rst Drac. vari

Roubaix Div. B E a t.u rs.

first Drac.solidurr^Eat.ursui & Homotr.

first Drac. simi D rac.sim .

Ph.cren. Div. A Orchies

W. meek. K iss.era s first Wetz, meckeli O ldhaven Fm. Mt.Héribu

I Whiteclif f ¡ Woensdrecht- Kalio

Hampshire Basin Northern Belgian Basin 298

Basin : P. com atum is recorded a first time at about scarce and the sudden difference in rate of sedimen­ 3,5m above the base of the Middle Bagshot Beds tation between White Cliff and Kallo may be w hile A. robustum disappears about 7 m higher. In overestimated. No doubt there was a difference the northern Belgian Basin the distribution of both because it is also noted at the same biostratigraphic species overlaps each other too in the lower part of level in our comparison of the Kallo sequence with our L. t m a m ella tu m Zone. From the distribution the one at Isle of Sheppey (eastern London Basin). of both species we suppose that the base of the Mid­ • The higher zones dle Bagshot Beds in the western London Basin may be somewhat older than our L. 1 m a m e lla tu m The succession of several biostratigraphically Zone ; maybe it corresponds to the transition bet­ significant species is the same in the Bracklesham w een our A. diktyoplokus Zone and P. triradiata Beds at White Cliff as in the higher Ypresian Z one (?). members of the Woensdrecht-Kallo section. R. glabrum was recorded at Kallo in our B. The Hampshire Basin O. rom anum Zone and recorded in White Cliff in the uppermost part of Brackesham Bed I. In the Hampshire Basin the reference section of The appearance of T. g a la tea and the Ypresian deposits is situated at White Cliff (Isle S. chlam ydophora near the base of our K. aff. of Wight). The studies on organic-walled clathrata Zone is situated at White Cliff in the mid­ microfossils from this section have been published dle of Bracklesham BedrV. by DAVEY et al. (1966), EATON (1976), COSTA & A. diktyoplokus is recorded for the first tim e in the DOW NIE (1976) and BUJAK et al. (1980). T he m ost northern Belgian Basin near the transition of the recent lithostratigraphy of these deposits was given Egem Sand to the Merelbeke Clay; its earliest by KING (1981) and EATON (1976). From the appearance at White Cliff is situated near the tran­ tables of distribution of dinoflagellates and from sition between Bracklesham BedsrV and V. In the comments presented in these publications it has northern Belgian Basin the top of the range of been possible to correlate the White Cliff section T. galatea is soon followed by the regular with our Woensdrecht-Kallo reference section in appearance of P. com atum . At White Cliff the the no rth ern Belgian Basin (fig. 5). ranges of both species overlap each other in the upper part of Bracklesham Bed V. This upper part COMMENTS of Bracklesham Bed V can best be correlated with • Basal Ypresian deposits our P. triradiata Zone. The transition of the Ypre­ sian to the Lutetian is situated near the top of our At White Cliff one notes at the base of Div. A 2 L. ¿mamellatum Zone and can be traced at White the presence of W. meckelfeldensis. This species Cliff at the base of the Bracklesham Bed VI in which appears in the Kallo section about three metres the Lutetian large foraminifer N u m m u lites above the base of the Ypresian deposits. The laevigatus has been recorded. equivalent of our P. trinem a Zone was not The rate of sedimentation was somewhat higher in deposited at White Cliff. The underlying Oldhaven the Bracklesham Beds I up to th e m iddle of IV at Formation is somewhat older. Indeed, our White Cliff than in the corresponding P. trinem a Zone is grosso modo the equivalent of D. varielongitudum + O. rom anum Zones in the th e W. astra Zone and neither P. trinem a or Kallo sequence. On the contrary, the sedimenta­ W. astra are recorded in the Oldhaven Formation. tion was less pronounced from the middle of • The E. ursulae — D. varielongitudum Z one Bracklesham Bed IV up to the top of BedV when transition compared with the corresponding K. aff. clathrata COSTA & DOWNIE (1976, p. 594) mention + A. diktyoplokus + P. triradiata + L. ¿ m a m e lla tu m Zones in the Woensdrecht-Kallo the record of D. varielongitudum near the top of reference section. the London Clay. According to KING (1981, p. 116) this record is situated at 71 m above the base of the London Clay in the uppermost part of Div. B. The C. Dieppe Basin (fig- 6 ) interval of the first record of D. varielongitudum In the Dieppe Basin the Ypresian deposits belong up tot the earliest appearance of K. clathrata- to the Varengeville Formation. The organic-walled coleothrypta covers the uppermost part of Div. B, microfossils in this formation were studied by the whole Division C and D,and the lowermost GRUAS-CAVAGNETTO and the results part of the Bracklesham Bed I. At Kallo (northern published in GRUAS-CAVAGNETTO (1970), Belgian Basin) D. varielongitudum an d AUFFRET & GRUAS-CAVAGNETTO (1975), K. clathrata-coleothrypta appear together. This CHATEAUNEUF & GRUAS-CAVAGNETTO means that the sedimentation nearly stopped for (1978) and GRUAS & BIGNOT (1985). T he studied a certain lapse of time at Kallo while at W hite Cliff samples come from the cliff sections to the west- it continued from the top of Div. B to the lower part southwest of Dieppe (Cap d'Ailly and Sotteville- of Bracklesham Bed I. That interval corresponds sur-Mer) and from offshore deposits in the Chan­ grosso modo with the glauconitic bed at Kallo nel at about 40 to 50 Km in face of the mentioned -305 m correlated with the one at Tielt - 101,5 m cliff sections. (Glauconiferous Bed of Tielt). A large part of this From the comments in GRUAS & BIGNOT interval at White Cliff contains no palynomorphs. (1985, pp. 119-120, text-fig. 2) it appears that the So the biostratigraphically valuable information is “Argiles glauconieuses inférieures“ at Cap d'Ailly, 299

Fig. 6 Zones ¡Members W

Biostratigraphic correlations I I I I i 11 I i 0 between the Dieppe Basin sections Lit? E and the Kallo-Woensdrecht reference section. m am . Vlierzele N I I I i I I i I i Pauc.trir. S ! I I I I I i I I D R E Pittem A reosph. C d ikt. H

Merelbeke T,

Kiss. aff. clath.

Kortemark I I I I I 11 I I O ch.rom . I I I I I I I i I K Drac.var. A

C hannel] L Roubaix E a t.u rs. (Lutetian ) L

V 0 I I I I I I I I i A R D rac.sim . E I I I I I 11 i i N G Ph.cren. E 11 V I I I I I i i I L Arg. glauc. W. m eek. L K iss.era s E first.Wetz.meckelf. Argiles à sablons first.Wetz.astra. V sA 'in' ' 'l Mt.Héribu F O R Sables fauves M Arg^glauc.jnt _ Woensdrecht- Kallo

Dieppe Basin Northern Belgian Basin

corresponding with the "Série de la Pointue" at K. clathrata has been recorded together with Sotteville-sur-Mer, are older than the W. astra P. zoharyii ( = P. su b tile in AUFRET & GRUAS- Zone. W. astra appears higher, in the base of the CAVAGNETTO, 1985, p. 650) and with "Argiles à sablons" which are separated from the Homotryblium species. In these samples one notes "Argiles glauconieuses inférieures" at Cap d'Ailly furthermore the absence of some significant by the "Sables fauves" in which no organic-walled species, namely D. simile, D. varielongitudum and microfossils have been found. These "Argiles à S. chlam ydophora. Such a species combination sablons", at least their upper part, can be correlated suggests us that the uppermost Ypresian deposits w ith our P. trinem a Zone. The age of the "Argiles in the Dieppe Basin correspond with the upper part glauconieuses inférieures" and perhaps of the of our D. varielongitudum Zone and the lower part "Sables fauves" too is thus older than the basal of our O. ro m a n u m Zone. Ypresian deposits in the Belgian Basin. From these correlations with the Kallo reference The transition to the next W. meckelfeldensis section in the northern Belgian Basin appears that Zone is recognised at Cap d'Ailly already near the an important hiatus corresponding at least to our transition of the "Argiles à sablons" to the "Argiles K. aff. clathrata + A. diktyoplokus + P. trira­ glauconieuses supérieures". Higher in the "Aagiles diata + L. ? m a m e lla tu m Zones separates the glauconieuses supérieures" one enters the Ypresian deposits in the Dieppe Basin from the D. sim ile Zone. In the uppermost Ypresian overlying Lutetian deposits. deposits sampled offshore in the Channel 300

D. Paris Basin • The gap between the E. ursulae Zone and the The Ypresian deposits in the Paris Basin have D. varielongitudum Zone been studied in several outcrops and borings In the Belgian Basin we have noted a gap mainly by GRUAS-CAVAGNETTO and by between the E. ursulae Zone and the D. CHATEAUNEUF. The information which was varielongitudum Zone. It corresponds with the D. published in CHATEAUNEUF & GRUAS- varielongitudum Zone sensu CPIATEAUNEUF & CAVAGNETTO (1968), GRUAS-CAVAGNETTO GRUAS-CAVAGNETTO [ibid., p. 73) in w hich D. (1968), CHATEAUNEUF & GRUAS- varielongitudum is not yet accompanied by K. CAVAGNETTO (1978) and LAURAIN e t al. (1983) coleothrypta-clathrata. is not as explicit as the information about the It corresponds in the Paris Basin with the upper­ dinoflagellate record in the corresponding deposits most part of the “Sables de Laon“ in the Cuise-la- of the London and Hampshire Basins. From the Motte boring and with some part of the lignitous available comments one can understand that the clays in a boring at La Défense (western part of the assemblages are in general rather poor, due to Paris agglomeration) (CHATEAUNEUF & marginal marine or brackish environmental con­ GRUAS-CAVAGNETTO, ibid., p. 62). ditions during sedimentation and probably too as a result of later oxidation of the deposits. • The D. varielongitudum Z one It was unfortunately not possible to present here In the lower part of this zone in the Belgian a figure illustrating correlations between a Basin D. varielongitudum is recorded. The species reference section in the Paris Basin with the is there accompanied by K. clathrata-coleothrypta. Woensdrecht-Kallo reference section in the nor­ This lower part corresponds thus with the lower­ thern Belgian Basin. most part of the K. coleothrypta Zone sensu The following, rather imprecise correlations are CHATEAUNEUF & GRUAS-CAVAGNETTO proposed between the Zones which we propose for [ibid., p. 73) which is situated in the “Sables the Belgian Basin and the Wetzeliellaceae Zones d'Aizy“ and the “Sables de Pierrefond“ (which form (cfr. COSTA, DENISON & DOWNIE, 1978) w hich together the “Sables de Cuise“ in the quarry at CHATEAUNEUF & GRUAS-CAVAGNETTO Cuise), and in the succeeding “Argiles de Laon“ (1978) have recognized in the Ypresian deposits of from a boring at Drancy (northeastern part of the the Paris basin. Paris agglomeration). In tnese “Argiles de Laon“ D. varielongitudum was recorded together with K. • The P. trinema Zone coleothrypta, D. simile an d D. s o lid u m In the Paris Basin the Ypresian sedimentation (CHATEAUNEUF & CRUAS-CAVAGNETTO, started at the time of deposition of the P. trinem a ibid., p. 64). Zone in the Belgian Basin. This zone corresponds • The O. romanum Zone up to the L. ? m am el­ grosso modo with the W. astra Zone which accor­ latu m Z one ding to CHATEAUNEUF & GRUAS- CAVAGNETTO ( 1978, p. 62) is situated in the base N o O. ro m anum nor other species characte­ of the “Sables de Laon“ from the Cuise-la-Motte rizing the O. ro m a n u m Zone and the following K. boring. aff. clathrata Zone, A. diktyoplokus Zone, P. triradiata Zone or L. 1 m a m e lla tu m Zone in the • The W.meckelfeldensis — K. crassoramosa + Belgian Basin have been recorded in the “Argiles de P. crenulatum Zones Laon“ or any other Ypresian deposits which in the These zones in the Belgian Basin are the equi­ Paris Basin are directly followed by the Lutetian valent of the W. meckelfeldensis Zone sensu deposits. We m ust think thus that in the Paris Basin CHATEAUNEUF & GRUAS-CAVAGNETTO an important sedimentary gap is recorded, which (ibid., pp. 71-72) and are represented in the lower corresponds probably with the O. rom anum Zone part of the “Sables de Laon“ from the borings at up to the L. ! mamellatum Zone in the Belgian Cuise-la-Motte and at Le Tillet, also in the “Argiles Basin. à lignites du Soissonnais“ in a boring at Mont Ber- non, the type locality of the Sparnacian (LAURAIN E. North Germany et al., 1983, pp. 244 and 250), and in the lignitous H. GOCHT (1969) has described the organic- clays in a boring at Pont de Puteaux (western part walled microfossils in Paleogene deposits from bor­ of the Paris agglomeration) according to ings at Meckelfeld, to the south of Hamburg. The CHATEAUNEUF & GRUAS-CAVAGNETTO deposits “Unter Eozän 1“ and the lower part of (1978, p. 62). “Unter Eozän 2“ were sampled in the boring • The D. sim ile + E. ursulae Zones Meckelfeld 8 6 ; the upper deposits of “Unter Eozän 3“ and a section through “Unter Eozän 4“ were These zones in the Belgian Basin correspond sampled in the boring Meckelfeld 87. In the table w ith the D. sim ile Zone sensu CHATEAUNEUF of species distribution (GOCHT, ibid., table 1) & GRUAS-CAVAGNETTO {ibid., p. 73) situated some species are noted which allow correlations in the higher part of the “Sables de Laon“ in the with the Woensdrecht-Kallo reference section in Cuise-la-Motte boring. th e n orthern Belgian Basin (fig. 7). 301

Unter Z o n e s M em b ers E ozän

Lit.?

Vlierzele

Pau c. tri r.

Pittem A reosph. dikt.

Unter

E ozän M erelbeke

E gem

Kiss. aff. clath.

Kortemark

Unter O ch .rom.

E ozän Orae.var.

Roubaix E a t.u rs.

D rac.sim .

Unter Ph.cren. Orchies Eozän

W. m ec k. K iss.era s

first Wetz, astra

Fig. 7 Woensdrecht- Biostra tigra phic correi a ti ons Kallo

Meckelfeld between the Meckelfeld borings sections Northern Belgian Basin (North Germany) and the Kallo-Woensdrecht North Germany reference section.

accepted until now, as the ash bearing deposits are • P. trinema Z one considered to be situated just below the base of the This zone corresponds, as we have seen higher, W. astra Zone. grosso modo with the W. astra Zone. W. astra was probably recorded by GOCHT [ibid., pp. 21-22, • W. meckelfeldensis — K. crassoramosa Zone pi. 10, fig. 8 , text-fig. 14) as Wetzeliella sp. 1 in the + P. crenulatum Z one + D. simile Zone samples 10 and probably too in sample 5, both from K. crassoramosa was recorded by GOCHT the "Unter Eozän 1" deposits. No other real [ibid., pp. 16-17, pi. 9, fig. 4) as W. clathrata. Its Wetzeliella spp. are observed in that part of the earliest appearance is situated in the sample 11 near "Unter Eozän 1". the top of "Unter Eozän 1" and accompanied by W. R em ark : Sample 10 is situated above volcanic ash lunaris. The base of our W. meckelfeldensis-K. (tuffit) layers; sample 5 below them. If the W. sp. crassoramosa Zone corresponds thus with the 1 from sample 5 corresponds also with W. astra, the upper part of the "Unter Eozän 1" deposits at first occurrence of that species is older than Meckelfeld. 302

® E. ursulae Z one western Limfjord area where it overlies the Upper Higher in the Meckelfeld deposits Paleocene Fur Formation (alias Mo Clay or Moe Homotryblium sp., recorded by GOCHT [ibid., Formation). The higher members of the R¿snaes p. 59, pi. 2, fig. 10) as Hystrichosphaeridium cf. Form ation (R^ up to R^j and the low er m em bers (L¡ siphoniphorum, and Dracodinium solidum are and L 2) of the Lilleoaelt Formation are well recorded for the first time near the middle of represented in clay pits at Gist and Hinge (eastern "Unter Eozän 3". part of Jutland) and in the Osterrende Store Baelt E. ursulae was not recorded but in the Belgian Basin borehole n° 83101 (western coast of Zealand). In Homotryblium spp. and D. solidum appear that area these Ypresian deposits rest on the Upper together at the base of our E. ursulae Zone. Thus Paleocene Ölst Formation which is a lateral the base of our E. ursulae Zone corresponds with equivalent of the Fur Formation (see HEILMANN- the levels midway the "Unter Eozän 3" deposits. CLAUSEN et al., 1985, text-figs. 4 and 8 ). From the comments ori the assemblages of • Sedimentary gap between oui E. ursulae Zone organic-walled microfossils in these deposits, a cor­ and D. varielongitudum Zone, + the D. relation scheme can be proposed between the Ypre­ varielongitudum Z one sian deposits in Denmark and the Woensdrecht- T he first D. varielongitudum was recorded Kallo reference section in the northern Belgian by G O C H T [ibid.] in samples a little below the Basin (fig. 8 ). In fig. 8 the vertical scale of the transition from "Unter Eozän 3" to "Unter Eozän deposits at Knuden and in the Österrende Store 4". The species was not recorded in the samples 30 Baelt boring has been exagerated ten times in com­ and 31 in the lower part of "Unter Eozän 4" but parison with the scale of the Woensdrecht-Kallo appears again more frequently in sample 32 and section. remains present in the assemblages of the follow­ ing fifteen metres of deposits. From this distribu­ e P. trinema Z one tion we can conclude that a part of the section in In the lowermost, silicified bed of the Knud­ the Meckelfeld boring 87 covering the uppermost shoved Member W. astra is recorded while W. levels of "Unter Eozän 3" and the lower half of meckelfeldensis or K. crassoramosa remain absent. "Unter Eozän 4" corresponds probably with the This lowermost bed of the Knudshoved Member sedimentary gap between our E. ursulae Z one and corresponds thus with our P. trinem a Zone D. varielongitudum Zone and with our following (equivalent of the W. astra Zone). D. varielongitudum zone. ® W. meckelfeldensis — K. crassoramosa Zone + P. crenulatum Zone In the Knudshoved Member dark grey, silty • O. romanum Z one + K. aff. clathrata Z one + clay is overlying the silicified lowermost bed. In A. diktyoplokus Z one + P. triradiata Z one + this clay W. meckelfeldensis and K. crassoramosa L. ? m am ellatum Zone appear for the first time. In the highest part of the In the higher "Unter Eozän 4" deposits no Knudshoved Member (a green clay) and in the significant species are recorded which characterize higher members Rj up to R 3 no D. sim ile nor th e O. rom anum Zone or higher zones in the typical E. ursulae have been recorded. Belgian Basin. No further correlations can be made. It is thus propable that the remaining part of the We think that the rest of "Unter Eozän 4" may cor­ Knudshoved Member, above its silicified lower­ respond with the higher part of our D. most bed, and the R¡ up to R 3 members correspond varielongitudum Zone and possibly to our O. with our W. meckelfeldensis — K. crassoramosa rom anum Zone. Z one + P. crenulatum Zone. It is improbable that deposits corresponding with our K. aff. clathrata Zone or higher zones are pre­ ® D. simile Z one + E. ursulae Z one sent in the Lower Eocene deposits at Meckelfeld T he first D. sim ile are recorded in the lower because several significant species which should p art of R 4 while in the upper part of that same R 4 normally have been found in that case, have not M em ber D. varielongitudum is already found. This been recorded there. suggests that the lower part of R 4 corresponds grosso modo with our D. sim ile Zone + E. ursulae F. Danish Basin Zone. The organic-walled microfossils in the Ypresian ® Hiatus between our E. ursulae Zone and our deposits of Denmark have been studied by D. varielongitudum Zone HANSEN (1979), HEILMANN-CLAUSEN (1982, As we have noted higher when correlating the 1983 and 1985), HEILMANN-CLAUSEN et al. Ypresian deposits of the Belgian Basin w ith those (1985) and NIELSEN et al. (1986). of the London Basin and Hampshire Basin, the The Ypresian deposits are grouped in the sedimentation was probably interrupted at Kallo Rdsnaes Formation (Knudshoved Member + R¡ up on the transition between our E. ursulae Z one and to Rg) and in the lower part of the overlying D. varielongitudum Zone. Lillebaelt Formation (L¡ and L 2). This hiatus corresponds with the interval between The lowermost part of the Rdsnaes Formation, the first record of D. varielongitudum and the first the Knudshoved Member, occurs only in the record of K. coleothrypta-clathrata. It corresponds 303

?R 6 Fig. 8 Biostratigraphic correlations between the sections in the Danish Basin and the Kallo-Woensdrecht reference section.

Zones 'Members

Lit.?

Vlierzele R5 Pauc.trir.

Pittem Areosph. dikt.

M erelbeke

R6

E gem

Kiss. aff. clath.

I Kortemark

O ch.rom . R5

Drac.var.

RA

Roubaix E a t.u rs.

iL ^ iD r a c simile Drac.sim .

R2 Ph.cren.

RI W. m eek. K iss.eras.

Mt.Héribu Knud­ sh oved Mb. Woensdrecht- Kallo Store Baelt Knuden boring 83101 Northern Belgian Basin Denmark w ith the higher part of R 4 and the lower part of R 5 higher part of Rg. From this distribution we con­ (K. coleothrypta-clathrata is recorded a first time clude that the top of R 5 and the lower half of Rg cor­ near the middle of R 5 ). respond to our O. ro m anum Z one + K. aff. clathrata Zone. ® D. varielongitudum Z one

Near the middle of R 5 appears K. coleothrypta- • A. diktyoplokus Zone + P. triradiata Zone + clathrata w hile O. rom anum is first recorded near L. I mamellatum Zone the top of R 5 . The major part of the upper half of R 5 A. diktyoplokus appears in the upper part of corresponds thus to our D. varielongitudum Zone. Rg. In the upper part of L 2 from the Osterrenden borehole n° 83101 occur three ash layers. Near the • O. romanum Z one + K. aff. clathrata Z one uppermost ash layer Dracodinium pachydermum Near the top of R 5 and in the lower part of Rg (CARO, 1973) is recorded for the first time while one encounters O. rom anum . K. aff. clathrata was K. colethrypto-cathrata has disappeared. not recorded but A. diktyoplokus appears in the (NIELSEN et al., 1986, fig. 6 , p. 245). 304

At 01st, somewhere between the second and the with a restricted stratigraphie range in that basin. third ash layer in unit L 2 , K. coleothrypta-clathrata Among these significant species, thirty-eight disappears (HEILMAN-CLAUSEN et al., 1985, which are easily recognizable have been retained p. 307). to define eleven zones ifig. 2). W hen com paring the In the Woensdrecht section (northern Belgian assemblages from different outcrops and borings Basin) K. coleothrypta-clathrata is absent from the we are able to make biostratigraphic correlations P. triradiata + L. ? m a m e lla tu m Zones) while D. (fig. 3), w hich attain a degree of precision com ­ pachydermum (CARO, 1973) (corresponding with parable with that seen in the correlations done by W. eocaenica in DE CONINCK, 1977, p. 44, pi. 3, STEURBAUT (in STEURBAUT & NOLF, 1986) on fig. 10; pi. 4, figs. 1-4) appears at the top of the the base of calcareous nannofossils. Studying the L. ? m a m e lla tu m Zone. investigations done in the surrounding basins, we This suggests us that the upper part of Ró, Lj and note several similarities between the species a large part of L2 can be correlated with our A. distribution of dinoflagellate cysts in the Ypresian diktyoplokus + P. triradiata + L. ? m a m ella tu m deposits from the Belgian Basin, London Basin, Zones and that the Ypresian-Lutetian transition is Hampshire Basin, Dieppe Basin, Paris Basin, North probably represented near the top of L 2 . Germany and the Danish Basin. These similarities make biostratigraphic correlations possible bet­ CONCLUSION w een these areas (figs 4-8) and the Belgian Basin. A scheme (fig. 9) resumes these correlations with the Ypresian organic-walled phytoplankton totals indication of the biostratigraphical position of the about three hundred species, about three fourths of principal members or divisions which were defined which are dinoflagellate cystforms. From their in the sourrounding basins, relatively to our distribution in the basal Ypresian deposits of the zonation. Belgian Basin it seems that near the margin of the This scheme gives also an idea of the represen- basin the environmental conditions at the time of tativity for the Ypresian of the deposits in each of sedimentation favoured production of fossilizable the basins. We see that the most representative sec­ forms. Reworked species, mainly derived from tions are found in the Hampshire Basin in the Mesozoic deposits, are encountered especially in reference section of White Cliff at Isle of Wight, in the lower members (Mont Héribu Member and the Belgian Basin in the combined reference section Orchies Clay); their frequency is lower in the of Kallo-Woensdrecht, and in the Danish Basin in overlying Roubaix Clay and Kortemark Silt and the combined section of Knuden (western Limfjord) becomes insignificantly low in the higher Ypresian area) and in the Store Baelt boring 83101 (western deposits. The succession of organic-walled Zealand coast). The combined section in Denmark phytoplankton in the Ypresian deposits of the is however about ten times thinner than the Belgian Basin is characterized by about fifty species

A»3ilr

30p

Reading Beds

Fig. 9 Correlations of the N.W. European Ypresian lithostratrigraphical units with the zones in the Kallo-Woensdrecht reference section. cj_i<>- ü-Ocr2

i— i__iLücn < u j—n—

- '■'o. r * - S - - - - OC? - o ^ y -Or

* i 1 o r o e c o

■C. a ,

< -o

o .Ï >, ° O .N

in \ \ v \\\

> u. o cc 2 < I- o z

UJ CD a: a o

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- J o z U.OK2 <1 OZ

'\V\ | # N 2 ? .S \- NNN

\a\QS> ^

< T ) O N a ni

LU tu in a. cc THANETIAN Rcal Plateau -Rockall varielongitudum coleothrypta lí & COSTA MÜLLER 1978 DOWNIE DENISON COSTA, Wetzeliella meckelfeldensis Wetzeliella astra Dracodlnium Zone Dracodinium Zone Kisselovia Zone Zone Zone simile NE Atlantic Atlantic NE Correlation o f the zones in the K allo-W oensdrecht reference section w ith the zones the ith w section reference oensdrecht allo-W K the in zones the f o Correlation w h ich were form erly proposed in the surrounding basins. surrounding the in proposed erly form were ich h w Cie area -Cuise CHATEAUNEUF CHATEAUNEUF varielongitudum coleothrypta GRUAS-CAVAGNETTO oudt Zono rotundata Wetzeliella Dracodinium Dracodinium coleothrypta Kisselovia Kisselovia Wetzeliella meckelfeldensis 1978 Zone simile Zone Zone astra Zone Zone Paris Basiri Basiri Paris ^ Kisselovia Kisselovia ^ \ fasciata fasciata \ >Zone i _ EATON & WILLIAMS WILLIAMS & ,EATON DOWNIE BUJAK, Cliff section hite -W Assemblage Assemblage Areosphaeridium Zone B-4 Zone arcuatum Assemblage Zone Zone Assemblage ursulae Assemblage abbreviatum Homotrvblium B-2 Zone Assemblage Pentadinium Assemblage comatum Phthanoperidinium 1980 Assemblage Zone Zone Assemblage phosphoritica Deflandrea LC-2 Eatonicvsta / B-l Zone lacticinctum B-3 Zone LC-1 a sie Basin pshire Ham 2 ._/ Assemblage Assemblage Kisselovia Zone LC-3 Zone reticulata i. 10 Fig. / / — / ? Areosphaeridium Areosphaeridium Zone pachydermis coleothrypta Zone diktyoplokus Dracodinium CLAUSEN HEILMANN va va r ielong itudum Kisselovia press in meckelfeldensis Zone ursulae Eatonicysta Dracodinium Dracodinium Zone Wetzeliella Wetzeliella Zone oiu Zone solidum Zone astra Zone -0lst-Hinge area -0lst-Hinge Limfjord -western area Basin Danish -W oensdrecht - Kallo - oensdrecht -W aeltm Zone mamellatum rpsd zonation proposed itolks Zone diktyoplokus Areosphaeridium Paucilobimorpha ? Litosphaeridium varielongitudum romanum Ochetodinium Kisselovia aff. clathrata Zone clathrata aff. Kisselovia rrdaa Zone triradiata Eatonicysta ursulae ursulae Eatonicysta Dracodinium Zone Zone Kisselovia crassoramosa crassoramosa Kisselovia meckelfeldensis Wetzeliella crenulatum Phthanoperidinium simile Dracodinium area Kallo the in gap sedimentary Zone Pseudomasia trinema trinema Pseudomasia Zone Zone Zone Zone reference section reference Belgian Basin Basin Belgian

305 306

reference sections in the Hampshire Basin and LITERATURE Belgian Basin. AUFFRET, J.P. & GRUAS-CAVAGNETTO, C. 1975 — Les for­ The basal Ypresian deposits in the northern m ations paléogènes sous-m arines de la M anche orientale. D on­ Belgian Basin and in Denmark are a little older than nées palynologiques. Bull. Soc. géol. France, 7C ser., XVII-5, in the Hampshire Basin. In the Kallo area (northern 641-655. Belgian Basin) we note the existence, in all pro­ BROWN, S. & DOWNIE, C. 1984 — 13. Dinoflagellate cystbiostratigraphy of Late Paleocene and Early Eocene bability, of a gap in sedimentation between our sediments from holes 552, 553A and 555, Leg 81, Deep Sea Drill­ local E. ursulae Zone and D. varielongitudum ing Project (Rockall Plateau). In ROBERTS, D.G., SCHNITKER, Zone. This gap corresponds grosso modo with the D. et al. (1984), Initial Reports of the Deep Sea Drilling Project, London Clay Divisions C and D at White Cliff vol. LXXX1, 565-579. (Hampshire Basin), and also with the upper part of BUJAK, J.P., DOWNIE, C., EATON, G.L. & WILLIAMS, G. 1980 — Dinoflagellate cysts and acritarchs from the Eocene of R4 + the lower part of R 5 in the Rdsnaes Forma­ Southern England. Spec. Pap. Palaeontology, 24, 100p. tion in Denmark. In the same scheme is also shown CHA TEAU NEUF, J.J. & GRU AS-CAVAGNETTO, C. 1968 — the change of position relatively to our zonation of Etude palynologique du Paléogène de quatre sondages du Bassin the boundaries between certain London Clay divi­ parisien. Chaignes, Montjavoult, Le Tillet, Ludes. M ém . sions in the London Basin when going from west B.R.G.M., 59, 113-159. to east, and also of the boundaries between certain CHATEAUNEUF, J.J. & GRUAS-CAVAGNETTO, C. 1978 — Les zones de Wetzeliellaceae (Dinophyceae) du bassin de Paris. members in the Belgian Basin when going from nor­ Bull. B.R.G.M., sect. IV, 2, 59-93. thern to central and southern areas. As a result of COSTA, L., DENISON, C. & DOWNIE, C. 1978 — The these correlations we can correlate our zones with Paleocene/Eocene boundary in the Anglo-Paris Basin, fl. geol. the different ones (based ondinoflagellates) which Soc. Lond., 135, 261-264. have been given for the Ypresian deposits in the dif­ COSTA, L. & DOWNIE, C. 1976 — The distribution of the ferent areas around th e N o rth Sea Basin (fig. 10). dinoflagellate Wetzeliella in the Palaeogene of north-western Europe. Palaeontology, 19, 591-614. As we see, the base of the W. astra Zone in the COSTA, L. & MÜLLER, C. 1978 — Correlation of Cenozoic Rockall Plateau deposits (N.E. Atlantic) might be dinoflagellate and n an n o p lan cto n zones from th e NE A tlantic somewhat older than the base of our P. trinem a and NW Europe. Newsl. Stratigr., 7, 65-72. Zone or of the W. astra Zone in the Paris, Hamp­ DAVEY, R.J., DOWNIE, C., SARJEANT, W.A.S. & WILLIAMS, shire and Danish basins. The sedimentary gap in G.L. 1966 — Studies on Mesozoic and Cainozoic dinoflagellate cysts. Bull. Brit. Mus. (Nat. Hist.) Geol., Suppl. 3, 248p. the Kallo area between the local E. ursulae Zone DE C O N IN CK , ƒ. 1965 — M icrofossiles Planctoniques du Sable and D. varielongitudum Zone corresponds with Yprésien à Merelbeke. Dinophyceae et Acritarcha. Verb. Ron. the D. varielongitudum Zone in the other basins. Acad. België, KL Wetenschappen, Verz. in 8, 36 (2), 54p. O ur ow n D. varielongitudum Zone at Kallo cor­ DE CONINCK, J. 1969 — Dinophyceae et Acritarcha de l'Ypré- responds with the lower part of the K. coleothrypta sien du sondage de Kallo. Verh. Kon. Belg. Inst. Natuurwet., Zone as defined by COSTA, DENISON & 151(1968), 67pp. DOWNIE (1978) and by HEILMAN-CLAUSEN (in DE CONINCK, J. 1973 — Application stratigraphique des m icrofossiles organiques dans l'Y présien du Bassin belge. Bull. press). Belg. Ver. Geol., Paleont., Hydrol., 81, 1-11. The Ypresian-Lutetian transition corresponds DE CONINCK, J. 1976a — Microfossiles à paroi organique de grosso modo with the upper limit of our l'Y présien du Bassin belge. Minist, econ., Serv. Géol. Belg., Pro­ 1 .1 mamellatum Zone and with the transition bet­ fessional Paper 1975-12, 151p. ween the A. diktyoplokus Zone and the D. DE CONINCK, J. 1976b — Een afzettingshiaat tussen het Ieperiaan en het Lutetiaan te Melle-Heusden. N atuurw et. pachydermum Zone in the Danish Basin. In the Tijdschr. 57 (1975), 224-229. other basins this transition is not reflected in the DE CONINCK, J. 1976c — Biostratigrafische korrelatie van corresponding zonations. Ieperiaanafzettingen te Aalbeke en te Lauwe, met de boring van Kallo. Natuurwet. Tijdschr., 57(1975), 230-235. DE CON INCK, J. 1977 — Organic-walled m icrofossils from the Eocene of the Woensdrecht borehole, southern Netherlands. Meded. Rijks. Geol. Dienst, N.S., 28(3), 33-64. DE CONINCK, J. 1980 — Biostratigraphic compilation: Dinoflagellate cysts in Paleogene deposits in Belgium, the ACKNOWLEDGEMENTS Southern Netherlands and Northern France. In VINKEN, R. & MEYER, K.J. (1980), IGCP Project 124, The N orthw est European The autor wishes to thank the technical staff of Tertiary Basin. Report n° 6, 93-97. the Laboratory of Paleontology (State University DE CONINCK, J. 1981 — Organic-walled microfossils in the Gent) : Mr. D. Bavay for drafting the many figures Clay of leper in the Overijse borehole. Bull. Belg. Ver. Geol., presented with this text, Mrs. N. Reynaert for 89(1980), 201-215. carefully typing the manuscript and Mr. T. Tem­ DE CONINCK, J. 1981 — Espèces indicatrices de microfossiles merman for assistance in reproducing the à paroi organique des dépôts de l'Y présien supérieur et du Luté- tien dans le sondage de Kallo. Tableau synthétique de la distribu­ photographs of the figures species. Their coopera­ tion d'espèces indicatrices dans l'Yprésien et le Lutétien du tion has been very much appreciated. Bassin belge. Bull. Belg. Ver. Geol, 89(1980), 309-317. 307

DE CONINCK, J. 1986 — Microfossiles à paroi organique de HEILMANN-CLAUSEN, C. 1985 — Dinoflagellate stratigraphy l'Yprésien inférieur à Quenast. Minist, écon., Serv. Géol. Belg., of the upperm ost D anian to Y presian in the Viborg 1 borehole, Professional Paper 1986/1, N°224, 59 p. central Jylland, Denmark. D.G.U., A 7, 1-69. DE CONINCK, J., DE DECKER, M., de HEINZELIN, J. & HEILMANN-CLAUSEN, C., NIELSEN, O. & GERSNER, F. WILLEMS, W. 1981 — L'Age des faunes d'Erquelinnes. Bull. Soc. 1985 — Lithostratigraphy and depositional environm ents in the belge de Géol., 90, fasc. 2, 121-154. U pper Paleocene and Eocene of D enm ark. Bull. Geol. Surv. Den­ DE C O N IN C K , J. & NOLF, D. 1979 — N ote sur les couches de m ark, 33, 287-323. base de la formation du Panisel. Bull. Soc. belge de Géol., 87 ISLAM, M.A. 1983 — Dinoflagellate cysts from the Eocene of (1978), 171-178. the London and the Hampshire Basins, southern England. DUPUIS, C., DE CONINCK, J. & ROCHE, E. 1984 — Remise Palynology, 7, 71-92. en cause du rôle paléogéographique du horst de l'A rtois à l'Ypré­ ISLAM, M.A. 1984 — A study of early Eocene palaeo- sien inférieur. Mise en évidence de l'intervention du Môle environments in the Isle of Sheppey as determined from transverse Bray-Artois. C.R. Acad. Sc. Paris, T. 298, Sér. II-2, microplankton assemblage composition. Tertiary Res., 6,11-21. 53-56. KING, C. 1981 — The stratigraphy of the London Clay and DUPUIS, C., DE C O N IN C K , J., GU ERN ET, Cl. & ROCHE, E. associated deposits. Tertiary Res. Spec. Paper, 6, 158 p. (in press) — Biostratigraphic data — Ostracods and organic KING, C. 1984 — The stratigraphy of the London Clay Forma­ walled microfossils of the Landen Formation and the base of the tion and Virginia Water Formation in the coastal sections of the leper Formation in the Knokke borehole. Isle of Sheppey (Kent, England). Tertiary Res., 5, 121-160. DUPUIS, C. & GRUAS-CAVAGNETTO, C. 1985 — The KNOX, R.W.O'B. &. HARLAND, R. 1979 — Stratigraphical rela­ Woolwich Beds et le London Clay de Newhaven (East Sussex), tionships of the early Palaeogene ash-series of NW Europe. /. données palynologiques et stratigráphiques nouvelles. Bull. Geol. Soc. London, 136, 463-470. Inform. Géol. Bassin de Paris, 22, 19-33. LAURAIN, M., BARTA, L., BOLIN, C., GUERNET, C., GRUAS- EATON, G.L. 1976 — Dinoflagellate cysts from the CAVAGNETTO, C., LOUIS, P., PERREAU, M., RIVELINE, J. Bracklesham Beds (Eocene) of the Isle of Wight, Southern & THIRY, M. 1983 — Le sondage et la coupe du Mont Bernon England. Bull. Brit. Mus. (Nat. Hist.) Geology, 26, 225-332. à Epernay ¡Mame). Etude sédimentologique et paléontologique GEETS, S. 1969 — Bijdrage tot de sedimentologische kennis van du stratotype du Sparnacien et de la série éocène. Géologie de het Paniseliaan. Doctorate thesis (not published). la France, 3, 235-254. GOCHT, H. 1969 — Formengemeinschaften alttertiären NIELSEN, O.B., BAUMANN, J., DEYU, Z., HEILMANN- Mikroplanktons aus Bohrproben des Erdölfeldes Meckelfeld bei CLAUSEN, C. & LARSEN, G. 1986 — Tertiär)’ deposits in Store H am burg. Palaeontographica B. 126, 1-100. Baelt. The Tertiary section of borehole D.G.I. 83101, öster- GRUAS-CAVAGNETTO, C. 1968 — Etude palynologique de renden, Store Baelt, Denmark. Geoskrifter, 24, 235-253. divers gisements du Sparnacien du Bassin de Paris. M ém . Soc. STEURBAUT, E. & NOLF, D. 1986 — Revision of Ypresian géol. France, N.S., XLVII, N° 110, 1-144. stratigraphy of Belgium and northwestern France. M eded. GRUAS-CAVAGNETTO, C. 1970 — Dinoplyceae, Acritarcha Werkgr. Tert. Kwart. Geol., 23, 115-172. et pollens de la Formation de Varengeville [Cuisien, Seine­ VANHOVE, H. 1986 — Mikrofossielen met organische wand maritime). Rev. Micropal. 13, 69-78. in het Onder-Eoceen te Herzele (Steenhuize-Wijnhuize) en te GRUAS-CAVAGNETTO, C. & BIGNOT, G. 1985 — La tran­ Ronse. State Univ. Gent, Licentiate thesis (not published). sgression cu isienne en H aute-N orm andie à Sotteville-sur-M er VLERICK, R. 1982 — Biostratigrafie van het Onder-Eoceen te (76-France) et le diachronisme des facies sparnaciens. Rev. Heestert (West-Vlaanderen) ; datering op basis van Paléobiol., 4, 117-132. mikrofossielen met organische wand. State Univ. Gent, Licen­ HANSEN, J.M. 1979 — Age of the Mo-Clay Formation. Bull, tiate thesis (not published). geol. Soc. Denmark, 17, 89-91. WALL, D., DALE, B., LOHMANN, G.P. & SMITH, W.K. 1977 HAWKINS, H.L. 1955 — The Eocene succession in the eastern — The environmental and climatic distribution of dinoflagellate part of the Enborne Valley. Quarterly f. Geol. Soc. London, 110, cysts in modern marine sediments from regions in the North 409-430. and South Atlantic Oceans and adjacent seas. M arine Micropal., HEILMANN-CLAUSEN, C. 1982 — The Paleocene-Eocene 1, 121- 200 . boundary in Denmark. Newsl. Stratigr., 11, 55-63. WILLEMS, W. 1980 — De foram iniferen van de leper Form atie HEILMANN-CLAUSEN, C. 1983 — Dinoflagellate zonation (Onder-Eoceen) in het zuidelijk Noordzee bekken and lithostratigraphy of Paleocene and Eocene sediments from [Biostratigrafie, Paleoekologie, Systematiek). State Univ. Gent, Doctorate thesis (not published). Denmark. Aarhus Univ. Licentiatthesis (not published). PLATE 1

Fig. 1 : Pseudomasia trinema DE CONINCK 1969. 500 x . Quenast Ala, +7501, slide 6 . Fig. 2 : Pseudomasia trinema DE CONINCK 1969. 500 x . Quenast Ala, + 75m, slide 5. Fig. 3 : Pseudomasia trinema DE CONINCK 1969. 500 x . Quenast A2, + 75 m, slide 4. Fig. 4 : Deflandrea oebisfeldensis ALBERTI 1959. 500 x . Overijse, +27m, slide 3. Fig. 5 : Deflandrea oebisfeldensis ALBERTI 1959. 500 x . Quenast A4, + 77m, slide 5. Fig. 6 : Deflandrea oebisfeldensis ALBERTI 1959. 500 x . Quenast Alb, + 75m, slide 4. Fig. 7 : Trigonopyxidia ginella (COOKSON & EISENACK 1960). 500 x . Q uenast B7, + 77m , slide 1. Fig. 8 : Trigonopyxidia ginella (COOKSON 3t EISENACK 1960). 500 x . Q uenast B7, + 77m, slide 3. Fig. 9 : Trigonopyxidia ginella (COOKSON & EISENACK 1960). 500 x . Overijse, + 33.7m, slide 4. Fig. 10 : Trigonopyxidia ginella (COOKSON 3t EISENACK 1960). 500 x . Q uenast B 8 , +77m, slide 1. Fig. 11 : Wetzeliella astra DENISON 1978. 500 x . Quenast A4, + 77 m, slide 5. Fig. 12 : Wetzeliella astra DENISON 1978. 500 x . St. Maur G240, + 69.5m, slide 5. Fig. 13 : Thalassiphora delicata WILLIAMS & DOWNIE 1966. 500 x . Q uenast A 6 , + 79 m, slide 2. Fig. 14 : Phthanoperidinium crenulatum (DE CONINCK 1976). 500 x . Overijse, + 38.5m, slide 2. Fig. 15 : Apectodinium hyperacanthum (COOKSON 3t EISENACK 1965). 500 Overijse, + 33.7m, slide 5. Fig. 16 : Phthanoperidinium crenulatum (DE CONINCK 1976). 500 x . Q uenast B 8 , + 77m, slide 3. Fig. 17-19 : Phthanoperidinium crenulatum (DE CONINCK 1976). 500 x . Quenast A4, + 77m, slide 4. Fig. 20 : Dracodinium solidum GOCFTT 1955. 500 x . Kallo, -329.5 m, slide 2. Fig. 21 : Thalassiphora delicata WILLIAMS & DOWNIE 1986. 500 x . Q uenast A 6 , + 79 m, slide 2. Fig. 22 : Apectodinium hyperacanthum (COOKSON 3t EISENACK 1965). 500 Tielt, -101.5m, slide 3. 309

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Fig. 1 : Adnatosphaeridium robustum (MORGENROTH 1966). 500 x . St. Maur G240, + 69.5m, slide 1. Fig. 2 : Wetzeliella meckelfeldensis GOCHT 1969. 500 x . Q uenast B 8 , + 77m, slide 1. Fig. 3 : Kallosphaeridium brevibarbatum DE CONINCK 1969. 500 x . Overijse, + 38.5 m, slide 3. Fig. 4 : Kallosphaeridium brevibarbatum DE CONINCK 1969. 500 x . Mons-Ghlin G245, + 49.3 m, slide 4. Fig. 5 : Wetzeliella meckelfeldensis GOCHT 1969. 500 x . Q uenast B 8 , + 77m, slide 1. Fig. 6 : Dracodinium simile (EISENACK 1954). 500 x . Overijse, + 38.5m, slide 5. Fig. 7 : Kallosphaeridium brevibarbatum DE CONINCK 1969. 500 x . St. Maur G240, + 69.5 m, slide 1. Fig. 8-9 : Phthanoperidinium echinatum EATON 1976. 500 x . Merelbeke sluice, +0.5m, slide 9. Fig. 10,12 : Kisselovia crassoramosa (WILLIAMS A DOWNIE 1866) 500 x O rchies, + 27.5 m, slide 3. Fig. 11 : Dracodinium simile (EISENACK 1954). 500 x . Mons-Ghlin G245, + 49.3 m, slide 2. Fig. 13-14 : Phthanoperidinium echinatum EATON 1976. 500 x . Merelbeke sluice, -3.5 m, slide 4. Fig. 15 : Phthanoperidinium echinatum EATON 1976. 500 x . M elle F-DB11, - 7 m, slide 2. Fig. 16 : Eatonicysta ursulae (MORGENROTH 1966). 500 x. M elle F-DB 11, + 5.5 m, slide 3. Fig. 17 : Kisselovia crassoramosa (WILLIAMS A DOWNIE 1966). 500 x . O verijse, + TI m , slide 3. Fig. 18 : Homotryblium pallidum ? DAVEY & WILLIAMS 1966. 500 x . M elle F-DB 11, - 5 m , slide 1 (filtered). Fig. 19 : Phthanoperidinium echinatum EATON 1976. 500 x . Woensdrecht, -459 m, slide 1. Fig. 20 : Phthanoperidinium echinatum EATON 1976. 500 x . Woensdrecht, -459 m, slide 3. 311

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Fig. 1 : Thalassiphora pelagica (EISENACK 1954). 500 x . Mont Héribu G246, + 53.3 m, slide 2. Fig. 2-3 : Eatonicysta ursulae (MORGENROTH 1966). 500 x . M elle F-DB 11, + 5.5m , slide 2. Fig. 4 : Homotryhlium pallidum ? DAVEY & WILLIAMS 1966. 500 x . M elle F-DB 11, - 5 m , slide 1 (filtered). Fig. 5 : Polysphaeridium zoharyii (ROSSIGNOL 1962). 500 x . Heusden F-DB 11, +0.5m, slide 1. Fig. 6 : Thalassiphora pelagica (EISENACK 1954). 500 x . Q uenast B 8 , + 77m, slide 1. Fig. 7 : Hystrichokolpoma granulatum EATON 1976. 500 x . Woensdrecht, - 441m, slide 6 . Fig. 8 : Hystrichokolpoma granulatum EATON 1976. 500 x . Woensdrecht, -429 m, slide 4. Fig. 9 : Hystrichokolpoma granulatum EATON 1976. 500 x . Egem-Ampe, + 38.2m, slide 5. Fig. 10-11 : Diacrocanthidium spinigerum DE CONINCK 1969. 1000 x . Kallo, -283.5m , slide 1. Fig. 12 : Polysphaeridium zoharyii (ROSSIGNOL 1962). 500 x . Aalbeke G80, + 43.5m, slide 2. Fig. 13 : Polysphaeridium zoharyii (ROSSIGNOL 1962). 500 x . Aalbeke G80, + 43.5 m, slide 1. Fig. 14 : Dracodinium varielongitudum (WILLIAMS & DOWNIE 1966). 500 Kallo, -288 m, slide 1. Fig. 15 : Dracodinium varielongitudum (WILLIAMS & DOWNIE 1966). 500 Lauwe-Knok, +26m, slide 1. Fig. 16 : Dracodinium varielongitudum (WILLIAMS & DOWNIE 1966). 500 Kallo, -288 m, slide 1. Fig. 17-19 : Kisselovia clathrata (EISENACK 1938). 500 x . Egem-Ampe, + 38.2m, slide 2.

316

PLATE 5

Fig. 1-2 : Glaphyrocysta exuberans (DEFLANDRE & COOKSON 1955). 500 x . Egem-ringbeek, + 28 m, slide 2. Fig. 3 : Spinidinium aff. essoi COOKSON & EISENACK 1967. 500 x . Torhout-Pottebezemhoek, +26m, slide 4. Fig. 4 : Spinidinium aff. essoi COOKSON & EISENACK 1967. 500 x . Torhout-Pottebezemhoek, + 26m, slide 2. Fig. 5-6 : Apectodinium homomorphum (DEFLANDRE & COOKSON 1955). 500 x . Egem-Ampe, + 38.2 m, slide 1. Fig. 7 : Apectodinium homomorphum (DEFLANDRE & COOKSON 1955). 500 x . Egem-Ampe, + 38.2m, slide 1. Fig. 8 : Apectodinium homomorphum (DEFLANDRE & COOKSON 1955). 500 x . Egem-Ampe, + 38.2m, slide 1. Fig. 9 : Spinidinium aff. essoi COOKSON & EISENACK 1967. 500 x . Melle F-DB 11, -7 m , slide 1 (filtered). Fig. 10 : P ediastrum sp. 500 x . Kallo, - 238 m, slide 2. Fig. 11 : P ediastrum sp. 500 x . Woensdrecht, -410m , slide 3 (filtered). Fig. 12 : P ediastrum sp. 500 x . Kallo, -239m , slide 3. Fig. 13 : Pulvinosphaeridium sp. 500 x. Kallo, - 238m, slide 3. Fig. 14 : Pulvinosphaeridium sp. 500 x . Kallo, - 238m, slide 2. Fig. 15 : Pulvinosphaeridium sp. 500 x . Torhout-Pottebezemhoek, +26m, slide 3. Fig. 16 : Areosphaeridium diktyoplokus (KLUMPP 1953). 500 x . Melle F-DB11, -4 m , slide 8 (filtered). Fig. 17-18 : Areosphaerdium diktyoplokus (KLUMPP 1953). 500 x. M elle F-DB 11, - 5 m, slide 4. Figs. 19-20 : Cerebrocysta bartonensis BUJAK 1980. 500 x . Heusden F-DB4, 0m, slide 2 (filtered). Fig. 21 : Cerebrocysta bartonensis BUJAK 1980. 500 x . Heusden F-DB4, 0m, slide 3 (filtered). Fig. 22 : Litosphaeridium / m a m e lla tu m DE CONINCK 1977. 500 x . Woensdrecht, -410m , slide 2 (filtered). Figs. 23-24 : Litosphaeridium i mamellatum DE CONINCK 1977. 500 x . Kallo, -208.9m , slide 1 (filtered). Fig. 25 : Paucilobimorpha triradiata DE CONINCK 1986. 500 x . Kallo, -208.9m , slide 1. Figs. 26-27 : Pyxidinopsis densepunctata DE CONINCK 1985. 500 x . Woensdrecht, - 459 m, slide 2. Fig. 28 : Pyxidinopsis densepunctata DE CONINCK 1985. 500 x . Woensdrecht, -401m , slide 2. Fig. 29 : Pyxidinopsis densepunctata DE CONINCK 1985. 500 x . Woensdrecht, -429 m, slide 1. Fig. 30 : Paucilobimorpha triradiata DE CONINCK 1986. 500 x . M elle F-DB 11, - 4 m , slide 10 (filtered). 317

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Fig. 1-2 : Impletosphaeridium rugosum MORGENROTH 1966. 1000 x . Woensdrecht, -410m , slide 1 (filtered). Fig. 3 : Impletosphaeridium rugosum MORGENROTH 1966. 500 x . M elle F-DB 11, x 5 m , slide 1 (filtered). Fig. 4 : Impletosphaeridium rugosum MORGENROTH 1966. 500 x . M elle F-DB 11, - 5 m , slide 1 (filtered). Figs. 5-6 : Phthanoperidinium comatum (MORGENROTH 1966). 500 x. Woensdrecht, -410m , slide 4. Figs. 7-8 : Impletosphaeridium rugosum MORGENROTH 1966. 1000 x . Woensdrecht, -441m , slide 2 (filtered). Fig. 9 : Wetzeliella aff. articulata (sensu CHATEAUNEUF & GRUAS-CAVAGNETTO 19T8). 500 x . Woensdrecht, -410m , slide 1 (filtered). Fig. 10 : Wetzeliella aff. articulata (sensu CHATEAUNEUF & GRUAS-CAVAGNETTO 1978). 500 x . Woensdrecht, -385m , slide 1. Fig. 11 : Phthanoperidinium comatum (MORGENROTH 1966). 500 x . Woensdrecht, -410m , slide 2 (filtered). Fig. 12 : Phthanoperidinium comatum (MORGENROTH 1966). 500 x . Egem-Ampe, + 40.3 m, slide 2. Fig. 13 : Wetzeliella aff. articulata (sensu CHATEAUNEUF & GRUAS-CAVAGNETTO 1978). 500 X. Woensdrecht, -410m , slide 2 (filtered). Fig. 14 : Wetzeliella aff. articulata (sensu CHATEAUNEUF & GRUAS-CAVAGNETTO 1978). 500 x . Woensdrecht, -416.5m , slide 1. Fig. 15 : Dracodinium pachydermum (CARO 1973). 500 x . Woensdrecht, - 385m, slide 5. Fig. 16 : Wetzeliella aff. articulata (sensu CHATEAUNEUF & GRUAS-CAVAGNETTO 1978). 500 X. Woensdrecht, -385m , slide 1. Fig. 17 : Dracodinium pachydermum (CARO 1973). 500 x. Woensdrecht, -380m , slide 7. Fig. 18 : Dracodinium pachydermum (CARO 1973). 500 x . Woensdrecht, - 380 m, slide 7. 319 FACULTE POLYTECHNIQUE DE MONS

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