Dinoflagellata cysts of the shallow marine Neogene succession in the Kalmthout well, northern Belgium

STEPH EN LO U W Y E & PIETER LAGA

DGF Louwye, S. & Laga, P.: D inoflagellata cysts o f the shallow marine N eogene suc­cession in the K alm thout w ell, northern Belgium . Bulletin o f the G eological So­ciety o f D enm ark, Vol. 45, pp. 73 -86 . Copenhagen, 1998-09-25.

The dinoflagellata cyst associations from the Neogene succession in the Kalmthout well allow a correlation w ith biozonations and key dinocyst events from the N orth Sea area and the eastcoast o f the USA. The recovered cyst assemblages suggest that an Early M iocene (late A quitanian - early Burdigalian) age can be attributed to the Berchem Formation, while the D iest Formation is o f Late M iocene (late Tortonian - M essinian) age. T he age of the K attendijk Form ation rem ains unclear. The L illo Form ation in the K alm thout w ell is o f Pliocene age and possi­bly no t younger than early Late Pliocene.

Keywords: D inoflagellates, N eogene, Southern N orth Sea, Belgium .

S. Louwye [stephen.louw ye@ rug.ac.be], Laboratory fo r Palaeontology, Univer­sity o f Ghent, K rijgslaan 281/S8, B -9000 Ghent, Belgium.P. Laga [pieter.laga@ pophost.eunet.be], G eological Survey o f Belgium, Jenner- straat 13, B -1000 Brussels, Belgium . 8 A pril 1998.

N eogene sedim ents in Belgium are only found in the area north o f A ntw erp and the Cam pine area (Fig. 1). The deposition took place along the southernm ost rim of the N orth Sea B asin in nearshore environm ents. The lithologies are dom inated by m edium - to coarse­grained sands, often very glauconitic and intercalated w ith shell beds. D écalcification can locally be im por­tant. T he occurrence o f gravel layers in the Neogene sequence points to a d iscontinuous sedim entation, which started in the E arly M iocene after a long p e­riod o f non-deposition caused by L ate O ligocene tec­tonic up lift (Vandenberghe e t al. in press). A ccording to these authors, the com bined effect o f tectonic up­lift o f N orthern B elgium with fluctuating sea levels caused the N eogene units to be incom plete, at least in the base o f the succession. The generally monotonous, uniform lithology and the patchy distribution o f the units ham per a correlation on a regional scale.

The N eogene succession o f Northern Belgium have been the subject o f m arine m icrofossil biostratigraphi- cal studies since 1970. P lanktonic foram iniferal asso­ciations from outcrops and boreholes in the Antwerp area w ere described by D e M euter & L aga (1970) and H ooyberghs & De M euter (1972). S ix benthic fo­ram iniferal assem blage zones fo r the M iocene and Pliocene succession of the A ntwerp area were defined by De M euter & Laga (1976). A correlation between the benthic foram iniferal biostratigraphy o f the near­

Louw ye & Laga: N eogene dinoflagellate cysts

shore N eogene deposits o f the Antwerpen area with the deeper m arine N eogene o f The N etherlands is given by D oppert et al. (1979). Nuyts (1990) com ­m ented upon the distribution o f benthic foram inifera in P liocene deposits at K allo near A ntw erpen. M ore recently, H ooyberghs (1996) has dealt w ith the plank­tonic foram iniferal associations and the stratigraphi- cal position o f the early M iocene E degem Sands (B erchem Form ation). All these m icropalaeontologi- cal studies led to but restricted chronostratigraphical interpretations for the B elgian Neogene. Correlation w ith the international standard biozonations is diffi­cult due to the boreal character of the foram iniferal associations in the A ntwerp area. No biostratigraphi- cal data on calcareous nannofossils or dinoflagellate cysts have been published so far. This paper describes the dinoflagellate cyst associations from the N eogene form ations in the K alm thout well. The N eogene suc­cession in the K alm thout well is considered to be a reference section for the A ntw erp area.

Lithostratigraphy and lithologyD e M euter & Laga (1976) redefined and form alised the lithostratigraphic fram ew ork o f the N eogene sed­iments based on observations o f large tem porary out-V LIZ ( VZW)

r w . . . MAR,NE IN S T IT U TE

73

S o u th e rn N o rth S ea

T h e N e th e r la n d s

K a lm th o u t

' i A n tw e rp

C a m p in e

51 °N

B e lg iu m

10 Km

F ra n c e

Fig. 1. Location of the Kalmthout well. Dashed line = southern limit of Neogene deposits in northern Belgium (modified after Tavernier & De Heinzelin 1963).

crops in the A ntw erp area (Fig. 2). T he cored K alm t­hout well (no. 6E-110 o f the G eological Survey of Belgium ) is located north o f A ntw erp near the border w ith The N etherlands (Fig. 1). M arine N eogene sedi­m ents are present between 52.7 m and 137 m depth (Fig. 3). The Berchem Form ation rests unconform able

Lithostratigraphy Series

A n tw e rp area

Lillo F orm ationZ a n d v lie t S a n d s M e rk s e m S a n d s K ru is s c h a n s S an d s

U pper

P liocene

O o rd e re n S a n d s L u c h tb a l S a n d s

K a tte n d ijk F o rm ationLow er

D ies t F o rm ationD e u rn e S a n d s

U ppe rM iocene

B erchem F orm ation M idd leM iocene

A n tw e rp e n S a n d s

K ie l S a n d s E d e g e m S a n d s

(B u rc h t g ra v e l)

L ow erM iocene

Fig. 2. Lithostratigraphy of the Neogene of the Antwerp area, northern Belgium (after De Meuter & Laga 1976).

on the O ligocène Boom Form ation and consists o f glauconitic m edium -grained sands w ith phosphate nodules and m arine shell beds. D e M euter & Laga (1976) redefined three mem bers (Edegem Sands, Kiel Sands and A ntw erp Sands) in the type area around Antwerp. This form ation is interpreted as a d iscon­tinuous un it characterised by short hiatuses (W outers & Vandenberghe 1994). The unconform ity between the Berchem Form ation and the overlying Diest F or­m ation is m arked by a gravel intercalation at 112 m. The D iest Form ation is 35 m thick and consists o f coarse-grained non-calcareous glauconitic sands and scattered fragm ents o f m arine shells. The sedim ents o f this form ation are considered to be gully deposits. A ccording to Wouters and V andenberghe (1994), the gully form ed during M iddle M iocene tim es and is the result o f strongly eroding tidal currents parallel to the coast. T he infilling of the gully is thought to be of L ate M iocene age. T he K attend ijk Form ation lies unconform ably on the D iest Form ation and is found between 77 m and 75 m. The lithology consists o f m e­dium - to coarse-grained glauconitic sands with nu­m erous D itrupa. The L illo Form ation com prises the upper part o f the N eogene sequence between 75 m and 52.7 m and consists of fine- to m edium -grained sand w ith clay intercalations, shell layers and scat­tered shells. The members o f the Lillo Formation (Fig. 2) were no t identified in the K alm thout well. The Lillo Form ation is considered to have been deposited in a very shallow m arine environm ent.

74 B ulletin o f the G eological Society of D enm ark

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Louw ye 8c Laga: N eogene dinoflagellate cysts 75

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76 Bulletin o f the G eological Society of Denmark

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Louw ye & Laga: N eogene dinoflagellate cysts 77

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78 Bulletin o f the G eological Society o f Denm ark

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M aterial and m ethodsTw enty-three co re sam ples distributed over the m a­rine N eogene sequence w ere prepared for palynologi- cal analysis using standard maceration techniques.The preservation of th e dinoflagellate cysts ranges from m oderate to good and 243 species w ere recorded. Ta­ble 1 gives in alphabetical order the percentage o f the species recorded in the investigated section (see also PI. 1-2). Four sam ples w ere not rich enough to count a m inim um o f 200 specim ens. Rew orked dinocysts are m arked w ith an asterisk. Rew orking is never im ­portant, but m ost apparent in the Berchem and Lillo Form ations. A fu ll account dealing w ith d inocyst tax­onom y is in preparation. We follow ed Lentin & W il­liam s (1993) for the nom enclature of the dinocysts. Two barren sam ples (114 m and 116 m) are located at the top of the B erchem Form ation and another tw o at the top o f the L illo Form ation (58 m and 54.5 m).

T he recovered associations allow a com parison and interregional correlation with contiguous areas. We re­ferred to zonations, dinocyst events and other studies from northw est E urope (C osta & M anum , 1988; Pow ell, 1992), northern G erm any (Lund e t al. 1993), England (Flead 1993, 1996, 1997), The N etherlands (Hem green, 1987) and the Norw egian Sea (M anum et al., 1989). The com prehensive biozonation of Powell (1992) was calibrated w ith earlier biozonations from the B ritish Isles and northw est Europe. A com parison w ith the eastcoast o f the U SA (de Verteuil & Norris, 1996) is also proposed. The dinocyst associations and biostratigraphy are discussed per form ation.

D inoflagellate cyst associations and correlationBerchem Formation (136.6 to 118 m)The basal two sam ples contain species w ith a known highest occurrence (HO) in the Low er M iocene, such as Caligodinium amiculum, Cordosphaeridium can­tharellus, Cribroperidinium tenuitabulatum, D eflan­drea p hosphoritica phosphoritica , D inopteryg ium cladoides sensu M orgenroth (1966), H om otryblium vallum, and Sum atradinium hamulatum. A break in the d inocyst associations is noted between sam ples 118 and 112 m (Fig. 3). The following stratigraphically sig­nificant species have their H O in the top o f the B er­chem Form ation: Apteodinium spiridoides, Chiropte- ridium galea, Cousteaudinium aubryae, Exochosphae­ridium. insigne, L ingulodinium multivirgatum, Oper­cu lod in ium longisp in igerum , O percu lod in ium p i ­aseckii, Palaeocystodinium golzowense, Sum atradin­ium druggii and Sum atradinium soucouyantae. It is not c lear whether Chiropteridium galea, D. phospho­ritica phosphoritica and H. vallum are rew orked or not in the Berchem Form ation, de Verteuil & Norris (1966) give an overview of the occurrences of these

L ouw ye & Laga: N eogene dinoflagellate cysts 79

4

10

12 13Plate 1. Fig. 1. Apteodinium, australiense, sample 126.4, 500 x. Fig. 2. Sumatradinium soucouyantae, sample 126.4, 500 X . Fig. 3. Barssidinium wrennii, sample 101.5, 500 x. Figs 4-5. Apteodinium spiridoides, sample 126.4, 500 x. Fig. 6. Selenopemphix brevispinosa brevispinosa, sample 112, 500 x. Fig. 7. Selenopemphix armageddonensis, sample 87, 500 x. Fig. 8. Selenopemphix dionaeacysta, sample 107.5, 500 x. Fig. 9. Sumatradinium druggii, sample 126.4, 500 x. Figs 10-11. Ataxiodinium zevenboomii, sample 70.7, 500 x. Fig. 12. Systematophora placacantha, sample 126.4, 500 x. Fig. 13. Caligodinium amiculum, sample 126.4, 500 x.

Neogene (marine)

B e rc h e m

M\'x:

D ie s t

-r~~rn J X T T T T

B L illo

“ i rÍS 3

i—r-r-rWWW'¿P ílf g 8 »

S S N ^ 31

S ystem

F o rm a t io n

L ith o lo g y

S a m p le s

D e p th (m )

0 0 1 1 13 2.

H om otryb lium vallumS um atrad in ium ham ulatumD eflandrea phospho ritica phospho riticaC aligod in ium am iculumC ordopshaerid ium can tha re llusC rib roperid in ium tenuitabu la tumD inop teryg ium c lado ides sensu M orgenroth 1966C ousteaud in ium aubryaeL ingu lod in ium m ultiv irgatumS um atrad in ium drugg iiA pteod in ium sp irido ides P a laeocystod in ium go lzow ense C hirop terid ium galea E xochosphaerid ium insigne H ystrichosphaerops is obscura O percu lod in ium long isp in ige rum O percu lod in ium p iase ck ii Sum atrad in ium soucouyantae System atophora p iacantha Selenopem phix a rm ageddonensisD apsillid in ium pseudoco lligerum Selenopem phix b rev isp inosa brev isp inosa R eticu la tosphaera actinocoronata B atiacasphaera m inuta B atiacasphaera sphaerica B itecta tod in ium serratum O percu lod in ium ? e irik ianum A chom osphaera anda lousiensis suttonensis B itecta tod in ium raedw a ld iiH abibacysta? sp. Head 1994 Inve rtocysta lacrym osa G eonettia? sp. Head 1997 O percu lod in ium tegulatum A taxiod in ium zevenboom ii A m icu losphaera um bracu la H ystrichosphaeropsis rigaud iae rigaudiae Tuberculodin ium vancam poae Achom osphaera an da lous iens is anda lousiensis M elitasphaerid ium choanophorum

Tva Aum Mch P ow ell 1992 (no rth w e s t E u ro p e )

D16 - D 16/17 (pars)

D19 (pars) - D20 C osta & M anum 1988 (n o rth w e s t E u rope)

patu­lum Z.

A. sp iri­do ides Z A. anda lous iens is Zone M an u m e t al. 1989 (N o rw e g ia n S ea )

DN 2 to p D N 9 - D N 10 de V e rte u il & N orris 1996 (e a s tc o a s t U S A )

Fig. 3. Stratigraphy, lithology, distribution of selected dinoflagellate cysts in the Kalmthout well and comparison with other biozonations (R: probably reworked; Kt: Kattendijk; Pg: Paleogene; BF: Boom Formation).

Louw ye & Laga: N eogene dinoflagellate cysts 81

9 < 10 12

Plate 2. Fig. 1. Amiculosphaera umbracula, sample 70.7, 500 x. Fig. 2. Distatodinium paradoxum, sample 126.4, 500 x. Fig. 3. Achomosphaera andalousiensis andalousiensis, sample 112, 500 x. Fig. 4. Tuberculodinium vancampoae, sample 126.4, 500 x. Fig. 5. Operculodinium? eirikianum, sample 101.5, 500 x. Fig. 6. Batiacasphaera minuta, sample 126.4, 1400x. Fig.7 .Reticulatosphaera actinocoronata,sample 101.5,500x.Fig. 8.Bitectatodinium serratum, sample 82,500x. Figs 9-10. Sumatradinium hamulatum, sample 130.5, 500x. Figs 11-12. Bitectatodinium raedwaldii, sample 82, 500 x.

82 Bulletin o f the G eological Society of Denm ark

species in Low er M iocene strata from several locali­ties. A n indirect argum ent for possib le rew orking is the occasional occurrence in the B erchem Form ation o f other pre-N eogene species, such as H om otryblium pallidum , Homotry blium p lectilum and Chiropteri- dium lobospinosum.

The Berchem Form ation can be p laced w ithin the Tuberculodinium vancampoae (Tva) Interval Biozone of Powell (1992) (Fig. 3). The low er boundary o f this zone is m arked by the first appearance of the nom i­nate species, w hich has its low est occurrence (LO) in 136.6 m at the base o f the formation. The upper bound­ary of this zone is defined by the first occurrence of Labyrinthodinium truncatum truncatum., a species ab­sent in the K alm thout well. A. spiridoides and C. can­tharellus d isappear resp. w ith in and a t the upper boundary of the T va Biozone. No diagnostic species o f the above ly in g L a b yrin th o d in iu m trunca tum truncatum (LTr) Interval Biozone are recorded. Powell (1992) calibrated his biozonation w ith the biozonation o f Costa & M anum (1988) and correlates the T va In­terval B iozone with Biozone D 16 and biozonal unit D 16/17 (pars).

T he lower part o f the Berchem Form ation (136.6 to 126.4 m) falls w ithin the Impagidinium patulum Zone o f M anum et al. (1989), even though the nom inate species which defines the low er boundary o f the zone, is absent. The HO o f C. cantharellus m arks the upper boundary of this zone and the low er boundary o f the next Apteodinium spiridoides Zone. The upper part of the Berchem Form ation can placed w ithin the A p te­odinium spiridoides Zone, although the upper bound­ary cannot be recognised because of the absence o f L. truncatum truncatum.

T he associations allow to place the Berchem F or­m ation in de Verteuil & N orris’ (1996) Sum atradin­ium soucouyantae Z one DN2, if C. galea, D. phos­phoritica phosphoritica, H. vallum are regarded as re­worked. S. druggii co-occurs w ith characteristic spe­cies o f the Z one D N 2, w here in the type locality (eastcoast o f the USA) its LO is at the low er bound­ary o f the overlying Cousteaudinium aubryae Zone DN3. The absence in the B erchem Form ation o f other species such as Cerebrocystapoulsenii, Impagidinium arachnion, L. truncatum truncatum and Labyrin tho­dinium truncatum m odicum exclude the presence of Zones DN3 and DN4.

Diest Formation (112 to 78 m)Few species have their HO near or at the top o f the D iest Form ation, such as D apsilidinium pseudocol- ligerum and Reticulatosphaera actinocoronata. Strati- graphical im portant species appearing in the base of the D iest Formation are Achom osphaera andalousien­sis andalousiensis and O perculodinium? eirikianum. H ystrichosphaeropsis obscura, Palaeocystodinium golzowense and System atophora placacantha are spe­

cies w ith a know n HO in the M iddle or Upper M io­cene; they disappear at the top of the Berchem For­m ation and w ere not encountered in the D iest Form a­tion. Stratigraphical im portant species with a restricted range and a LO in the M iddle or U pper M iocene, such as C annosphaeropsis passio (= Cannosphaeropsis utinensis sensu Brow n & D ow nie 1985), C. poulsenii (= Gen. et sp. nov. o f Piasecki 1980), Gramocysta verricula, Labyrinthodinium truncatum truncatum and U nipontedinium aquaductum are not found in the D iest and Berchem Form ations in the K alm thout well. The ranges of Selenopem phix arm ageddonensis and Selenopem phix brevispinosa brevispinosa are limited to the D iest Form ation. N o other stratigraphically im­portant species w ith a HO or LO in this form ation are noted.

T he D iest F orm ation falls w ith in the A m iculos­phaera umbracula (Aum ) Interval B iozone o f Powell (1992), based on diagnostic indices, such as Am icu­losphaera umbracula, Reticulatosphaera actinocoro- nata and Selenopemphix brevispinosa brevispinosa (= Selenopem phix sp. A sensu B row n & D ow nie 1985) and the absence o f others, such as A pteodinium tec- tatum, G erlachidinium aechmophorum, G. verricula, P. golzowense, S. placacantha and U. aquaductum. The upper part o f the A um Interval biozone (above the HO o f R. actinocoronata) is m ost probably not present in the D iest Form ation. The nom inate species o f the A um Interval B iozone has its LO in sam ple 82 and is poorly represented in the D iest Formation. Its absence in the low er sam ples could be environm en­tally controlled, since this form ation w as deposited in a nearshore environm ent. A ccording to H ead (1996), A. umbracula has an oceanic to outer neritic prefer­ence. T he A um In terval B iozone is ca lib ra ted by Powell (1992) w ith B iozones D 19 (pars) and D20 of Costa & M anum (1988).

The D iest Form ation can be correlated w ith the Achom osphaera andalousiensis Zone o f M anum et al. (1989), based on the LO of the nom inate species. The upper boundary of this zone is not defined. R. actino­coronata has its HO w ithin this zone according to M anum et al. (1989).

The presence of A. andalousiensis andalousiensis, D. pseudocolligerum , OP. eirikianum and S. brevi­spinosa brevispinosa and the H O ’s o f H. obscura, Operculodinium piaseckii, P. gohowense, Sumatradin­ium soucouyantae, Sum atradinium druggii place the D iest Form ation w ithin the upper part o f de Verteuil & N orris’ (1996) H ystrichosphaeropsis obscura Zone DN9 and in the Selenopemphix armageddonensis Zone DN10.

A correlation of the D iest Form ation w ith deposits o f the regional M iocene G ram and Sylt stages in the N ieder O chtenhausen w ell (Lund et al. 1993) is based on the occurrences o f S. brevispinosa brevispinosa and R. actinocoronata (Fig. 4). The absence o f H. obscura in the D iest Form ation ham pers a m ore detailed cor­relation.

Louw ye & Laga: N eogene dinoflagellate cysts 83

Broeksittard well SE Netherlands

Herngreen (1987)

Formations

216 m .

inden

Breda

Kalmthout well Northern Belgium

Formations

L iilo

78 m

r>'.-

260m- :̂ °nset>'...—

1 18m

D ie s t

B erchem

Nieder Ochtenhausen well Northern Germany Lund et al. (1993)

"Stufe"

Ä sl> .^ 92 m

Gram

_angen- felde

Fig. 4. Correlation of the Neogene Formations in the Kalmthout well with the Neogene Formations in the Broeksittard well (SE Netherlands) and the Nieder Ochtenhausen well (north­ern Germany) (Kt.: Kat­tendijk; Q: Quaternary).

T he occurrences o f P. golzow ense and Pentadinium laticinctum laticinctum in the B roeksittard w ell in SE N etherlands (Herngreen 1987) correlate tentatively the deposits o f the D iest Form ation partly with the Breda F orm ation and the Inden Form ationin the Ruhr Val­ley G raben (Fig. 4).

Kattendijk Formation (76 m)Batiacasphaera sphaerica is the only species w ith a HO in the K attendijk Formation. The jo in t occurrence w ith Achom osphaera andalousiensis andalousiensis p laces the K attendijk Form ation also in the A chom o­sphaera andalousiensis Zone of M anum et al. (1989). The H O of Reticulatosphaera actinocoronata at 78 m suggest that the K attendijk Form ation may be co r­related w ith the M elitasphaeridium choanophorum (M ch) Interval B iozone o f Powell (1992).

Lillo Formation (73.3 to 62.6 m)The L illo Form ation is characterised by the HO o f Ataxiodinium zevenboomii, B itectatodinium raedwal- dii, Bitectatodinium serratum, HabibacystaP. sp. H ead (1994), Hystrichokolpom a rigaudiae rigaudiae and Invertocysta lacrym osa. The range o f three stra ti- graphical im portant species is restricted to the L illo Form ation (Achom osphaera andalousiensis suttonen-

sis, G eonettia? sp. H ead (1997) and O perculodinium tegillatum).

The L illo Form ation falls w ithin the M elitasphaer­id ium choanophorum (M ch) In terv a l B iozone o f Powell (1992), even though the species defining the low er and upper zonal boundaries are no t recognised (resp. Spiniferites cf. pseudofurcatus and Spiniferites elongatus). The diagnostic species o f this zone w ith a HO in the L illo Formation are H. rigaudiae rigaudiae, I. lacrym osa and M. choanophorum.

A ge o f the form ations in the K alm thout wellAn early M iocene age can be proposed for the B er­chem Form ation (Powell 1992, Costa & M anum 1988 and M anum et al. 1989). The correlation w ith the DN 2 Zone of de Verteuil & Norris (1996) indicates a late Aquitanian to early Burdigalian age for th e formation (Fig. 5).

The correlation o f the D iest Formation w ith the Aum Interval B iozone o f Powell (1992) points to a Torto- nian - M essinian age, while a correlation w ith the u p ­per part o f de Verteuil & N orris’ (1996) DN9 Zone and with the succeeding DN 10 Zone indicates a late Tortonian - M essinian age.

A com parison w ith the zonation o f M anum et al. (1989) indicates a possible Late M iocene age for the

84 B ulletin o f the Geological Society o f Denm ark

O)

i o r a «Lillo

Kt.i rc c ?

D ie s t

5.2

O)_j

16.4

B erchem

cr23.

Fig. 5. Age of the Neogene Formations from the Kalmthout well. Time scale after Berggren et al. (1995) (Kt.: Kat­tendijk). The question marks indicate the uncertain posi­tion of the Kattendijk Formation.

K attendijk Form ation. The assignm ent o f the K at­tend ijk and L illo Form ations to the M ch In terval B iozone of Powell (1992) indicates thus a Pliocene age.

H ead (1993,1996,1997) has described the dinoflag­ellate cyst associations o f several P liocene deposits in outcrops and boreholes in East A nglia and gave a detailed overview of the ranges of the stratigraphi- cally im portant species found there in the L illo F or­m ation (see above). T he ranges allow to attribute to the sequence below 64 m an age not younger than the early la te P liocene (early P iacenzian). A younger age for 62.6 m cannot be excluded. If the presence o f A. zevenboom ii (as “A taxiodinium elongatum ” in Zeven­boom 1995 M S) in the Late M iocene o f T he N ether­lands proves indeed to be doubtful, then a P liocene age (Zanclean to Piacenzian) can be attributed to the K attendijk Form ation and Lillo Form ation.

A cknow ledgem entsWe are indebted to J. D e Coninck for stim ulating dis­cussions on dinoflagellate cyst taxonom y and m or­phology. J. P ow ell, S. Piasecki, J. Sam uelsson and J. Vernieres are thanked for their constructive reviews of the m anuscript.

Dansk sam m endragNeogene dinoflagellat selskaber i K alm thout borin­gen i det nord lige Belgien beskrives pá basis a f 23 p rp v er f ra B e rc h em , D ies t, K a tten d ijk og L illo Form ationem e. D isse selskaber kan korreleres med dinoflagellat zonationer og vigtige dinoflagellat events kendt fra N ordspen og pstkysten af USA. P â grund- lag af d inoflagella t selskaberne kan B erchem For­mationen henf0res til N edre M iocæn (0 v re Aquita- nien-N edre B urdigalien), mens D iest Form ationen er fra 0 v re M iocæn (0 v re Tortonien-M essinien). Alde- ren af K attendijk Form ationen er usikker. L illo For­mationen i K alm thout boringen er a f Pliocæ n alder and sandsynligvis ikke yngre end tidlig Sen Pliocæn.

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86 Bulletin o f the Geological Society o f Denm ark