Abhandlungen Der k. k. Geologischen Reichsanstalt 41-0097-0108

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Abh. Geo l . B.-A.ISSN 0378-0864

ISBN 3-900312-61-3Band 41 S. 9 7 - 1 0 8 Wien , Apr i l 1988

C E N O Z O I C F O R A M I N I F E R A L B I O S T R A T I G R A P H Y O F T H E C E N T R A L

N O R T H SEA

by

F.M. GRADSTEIN, M.A. KAMINSKI and W.A. BERGGREN

With 2 figures and 2 tables

ZUSAMMENFASSUNG

An 29 Bohrungen aus dem Bereich der zentralen Nordsee wurde eine stratigraphische Analyse an 147 ben-

thonischen Foraminiferenarten mit über 60 agglutinierten Arten und einigen planktonischen Formen durchgeführt. Dazu wurde das RASC (ranking and scaling) Computerprogramm für Zonierung und Feststellung paläontologischer Ereignisse herangezogen. Die Tiefenwerte der physikalischen Log marker A-G in den Bohrungenwurden ebenso in das Computerprogramm einbezogen. Zehn Zonenabschnitte werden vorgeschlagen: 1) Subbo

tina pseudobulloides Zone - Danien; 2) Trochammina ruthven murrayi - Reticulophragmium paupera Zone - SelandCoscinodiscus spp. Zone - oberes Selandien/unteres Ypresien; 4) Subbotina patagonica Zone - Ypresien; 5) Reticulo

phragmium amplectens Zone - Mittel/Obereozän; 6) Globigerinatheka index Zone - Obereozän; 7) Rotaliatina bulimoidesne - Rupelien; 8) Globigerina ex gr. officinalis Zone - Oberoligozän/Untermiozän; 9) Globorotalia praescitula - G. zea

landica Zone - Unter/Mittelmiozän; 10) Cassidulina teretis Zone - Mittelpliozän/Pleistozän.Der Log marker A tritt am Ende der Kreide auf; Log marker B liegt allgemein im Danien; Log marker C und D

begleiten die Tuffe in der Nähe der Paleozän/Eozän-Grenze; Log marker E liegt am Top des Untereozäns; Log

marker F liegt nahe der Eozän/Oligozän-Grenze; und der Log marker G tritt am Ende des Bereichs Unter/Mittelmiozän auf. Eine Verbreitungstabelle zeigt die durchschnittliche und gesamte Reichweite von 30 agglutiniertenTaxa. Diese Tabelle ist mit geringen Veränderungen auch im offshore-Gebiet Kanadas anzuwenden.

A B S T R A C T

A stratigraphic analysis was made of 147 benthic foraminifera, including over 60 agglutinated ones and

some planktonic taxa in 29 wells, central North Sea. Use was made of the ranking and scaling (RASC)

computer program for zonation and normality testing of paleontological events. The depth picks of physicallog markers A-G in the wells were also included in the RASC input file. Ten interval zones are proposed,

including: (1) Subbotina pseudobulloides Zone - Danian; (2) Trochammina ruthven murrayi -

Reticulophragmium paupera Zone - Selandian; (3) Coscinodiscus spp. Zone - Late Selandian/Early

Ypresian; (4) Subbotina patagonica Zone - Ypresian; (5) Reticulophragmium amplectens Zone - Middle/Late

Eocene; (6) Globigerinatheka index Zone - Late Eocene; (7) Rotaliatina bulimoides Zone - Rupelian; (8)

Globigerina ex. gr. officinalis Zone - Late Oligocene/Early Miocene; (9) Globorotalia praescitula - G.

zealandica Zone - Early/Middle Miocene; (10) Cassidulina teretis Zone - Middle Pliocene/Pleistocene.

G r a d s t e i n , F .M. , Geo log ica l Survey o f Ca na da , Bedfo rd I ns t i t u t e ofO c e a n o g r a p h y , D a r t m o u t h , N . S . B 2 Y 4A 2 and C e n t r e for M a r i n e

G eo l og y , D a l h o u s i e U n i v e r s i t y , H a l i f ax , N.S . C A N A D A .

K am i n sk i , M .A. , W H O I / M I T J o i n t P r o g r am in O c ea n o g r ap h y , W o od s H ol e O c ean o g r ap h i c I n s t i t u t i o n , W o o d s H o l e , MA 02543 U.S .A .B e r g g r e n , W , A ., G eol o g y an d G eo p h y s i c s D e p a r t m e n t , W o o d s H o le O c ea n o g r ap h i c I n s t i t u t i o n , W o o d s Hole , MA 02543 U.S .A .

97



Log m ark er A occu r s a t the top Cre tace ous ; log ma rke r B on ave rage i s in the D a n ian ; log m ark er s C and D

de l inea te the tu f f s nea r the P a leocene /Eocene boundary ; log marker E i s top Ear ly Eocene ; log marker F i s

ne a r the Eocene /O l igocene bound ary and log mark er G occu r s a t the top of the Ear ly /M idd le M iocene . A

ran ge cha r t dep ic t s the ave rage and to ta l s t r a t ig r a ph ic r ang e of 30 agg l u t ina ted ben th ic t axa . Th i s c ha r t ,

wi t h min or modif icat ions , i s a lso appl ic able of fshore eas t ern Ca na da.

I N T R O D U C T I O N

The Ter t i a ry G raben o f the cen t r a l N or th S ea s e rved

a s a l i n k b e t w e e n t h e e x p a n d i n g N o r w e g i a n -

G reen land S ea and the s ha l low ep icon t inen ta l s eas

o f N or th w es t Eu ro pe . We a re s tudy in g the Te r t i a r y

s he l ly micro fos si l a s s em blage s of the cen t r a l N o r th

Sea as pa r t of a long- te rm inv es t ig at ion to fu r thero u r u n d e r s t a n d i n g of t h e t a x o n o m y , g e o g r a p h i c

d i s t r i b u t i o n a n d p a l e o e co l o g y of a g g l u t i n a t e d

fo ramin i f e r a a s w e ll a s the i r u t i l i ty fo r s t r a t ig r aph y .

F o l l o w i n g t h e w i d e s p r e a d d e p o s i t i o n o f D a n i a n

cha lk , south of abou t 60° N, the N or t h Se a Ba s in

5

60°-

58°-

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52°.

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CON OCO 2 1 1 / 1 9 - 1 1 5 .

T o t a l 3 / 9 A - 1 1 6 .

T o t a l 3 / 2 5 - 1 1 7 .T o t a l 9 / 1 0 B - 1 1 8 .

M o b i l 9 / 1 3 - 1 1 9 .

M o b i l 9 / 1 3 - 3 A 2 0 .

M o b i l 9 / 1 3 - 5 A 2 1 .

S h e l l 9 / 2 3 - 1 2 2 .

E s s o N o r w a y 1 6 / 1 - 1 2 3 .B P 1 4 / 4 - 1 2 4 .B P 1 4 / 1 5 - 2 2 5 .

B P 1 5 / 2 0 - 1 2 6 .BP 1 5 / 2 0 - 2 2 7 .

B P 1 6 / 1 1 - 1 2 8 .

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P h i l l i p s 1 6 / 1 7 -1P h i l l i p s 1 6 / 2 9 -2B P 2 1 / 1 0 - 1B P 2 1 / 1 0 - 4P h i l l i p s 2 2 /1 4 - 1 XP h i l l i p s 2 3 /2 2 - 1M o b i l 2 1 / 2 8 - 1P h i l l i p s 3 0 / 1 3- 1 XP h i l l i p s 2 /7 - 1 XAMOCO Norw ay 2 /8 -1S h e l l 3 0 / 1 9 - 1D a n s k N o r d s o E - lD an s k N o r d s o E -2D an s k N o r d s o A -2AMOCO 3 8/ 1 6 -1

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Fig. 1.Location of 29 exploration wells, Central North Sea..

98



underw en t r ap id s ubs idence (S c la te r and Chr i s t i e

1980; G rad s te in an d Bergg ren 1 9 8 1 ; Wood 1 9 8 1 ). A s

a resul t , ter r igenous c las t ic sediments in excess of 3

km th ick accumula ted in the cen t r a l po r t ion o f the

bas in . Th ickes t s ed imen ts a r e found in the Cen t r a l

G r a b e n , w h e r e a s th e V i k i n g G r a b e n r e c e i v e d

b e t w e e n 2 a n d 3 k m of s e d i m e n t . M u d s t o n e s

p r e d o m i n a t e , w i t h d e e p m a r i n e c l a s t i c f a n s , l i k e

those of the Fo r t ie s and Fr ig g o il f ie lds d evelop ingdur in g the ea r ly s t age o f Ter t i a ry s ubs idence . In th e

Ekof i s k a r ea pos t -D an ian o l i s to s t romes occu r . By

M idd le M iocene t ime the N or th S ea t rough had been

f il le d , l e a v i n g a n e r i t i c e n v i r o n m e n t w i t h a

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

d o m i n a t e d by Cassidulina, Elphidium,

Fursenkoina, an d Cibicidoides.

The pos t -D an ian , P a leocene th rou gh Ear ly -M idd le

M iocene muds tones ha rbour a r i ch and d ive r s i f i ed

f lys ch -type agg lu t ina ted ben th ic f auna (G rad s te i n

and Be rggr en 1981) . In th is s tudy we repor t on thes t r a t ig r aph ic d i s t r ibu t ion o f the ben th ic f auna in 29

e x p l o r a t o r y w e l l s . O v e r 2 0 0 0 c u t t i n g s , s i d e w a l l

cores and some core samples were analyzed ( table 1 ;

f igu re 1 ). I n o rd e r to s t a nd ard ize t he t axo nom ic

Table 1.Central North Sea wells and thickness of Cenozoic internals tud ied; wel ls are l isted approximately f rom north to south asshow n in figure 1. Wells marek d with an asterisk (*) emp loyedcoring techniques in addi t ion to cut t ings sampl ing.

Conoco

T o t a l

T o t a lT o t a l

S he l l

Mobil

Mobil

M ob i l

D ans k N ords o

D ans k N ords o

D ans k N ords o

B P

B P

B P

B P

B P

B P

B P

Es s o N orw ay

P h i l l ip s

P h i l l i p s

P h i l l ip s

Mobil

P h i l l i p s

P h i l l ip s

A m o c o N o r w a y

P h i l l ip s

S he l lA moco

211/19-1

3/9 A-1

3/25-19/1 OB-1

9/23-1*

9/13-1

9/13-3A

9/13-5

A-2*

E - 1*

E - 2*

14/4-1

14/15-2

15/20-1

15/20-2

21/10-1

21/10-4

16/11-1

16/1-1*

2/7-IX

16/17-1

16/29-2

21/28-1

22 /1 4 - IX

23/22-1

2/8-1

30 /1 3 - IX

30/19-1*38/16-1

2000 - 5925 '

1 3 5 5 - 2 1 8 0 m

554 - 2580 m1682 - 2952 m

900 - 6700 '

1800 - 8700'

990 - 8840 '

1 6 0 0 - 8 9 0 0 '

4650 - 6080 '

4400 - 6698 '

471 0 - 6470"

280 - 989 m

5 0 9 - 1 9 3 1 m

1 240 -1 9 66 m

870 - 234 3 m

49 70 - 79 8 0 '

1 2 1 7 - 2 8 0 8 m

793 - 2200 m

1 2 5 0 - 9 0 2 5 '

2030 - 9700 '

3579 - 9500 '

2000 - 894 5 '

2090 - 4600 '

3400 - 987 5 '

1 5 2 5 - 1 0 1 2 5 "

1 1 9 0 - 8 2 1 0 '

5 2 5 - 1 0 1 0 2 "

1 4 1 0 - 1 0 5 0 0 '1480 - 3870 '

nomenc la tu re , a l l w e l l s amples w ere inves t iga ted by

the s en io r au tho r ; a s s i s t ance w as p rov ided by the

junior authors on th is pro ject . A large col lect ion of

N or th S ea type s pec imens , hous ed w i th the s en io r

a u t h o r i s a v a i l a b l e fo r c o m p a r a t i v e s t u d i e s . T h e

t a x o n o m y of t h e b e n t h i c f o r a m i n i f e r a f o l l o w s

G r a d s t e i n a n d A g t e r b e r g ( 19 8 2 ), G r a d s t e i n a n d

Bergg ren (1 9 8 1 ) and K amins k i et al. ( th i s vo lume) .

A re v i s i o n o f t h e t a x o n o m y o f t h e a g g l u t i n a t e d

morpho types encoun te red i s in p rog res s and w i l l be

r e p o r t e d o n e l s e w h e r e . T h e f in a l s t r a t i g r a p h i c

ana lys i s p r es en ted he re invo lves the d i s appearance

leve l s ( tops ) o f 1 47 be n th ics , inc lu d i ng ov er 60

agg lu t ina ted ones and s ome p lank ton ic t axa .

F o r t h e p u r p o s e o f t h i s s t u d y t h e m i c r o f o s s i l

d i s t r i b u t i o n d a t a w e r e a u g m e n t e d b y t h e r e l a t i v e

pos i t ion in the we l ls (in feet or m ete rs of dep th b elow

the ro ta r y t ab le ) o f phys ica l log m ark er s A th roug h

G a s d e f i n e d b y A . C . M o r t o n a n d R . B . K n o x

(per s ona l communica t ion , 1 9 8 4) .

P R E V I O U S B I O S T R A T I G R A P H I C S T U D I E S

The Cenozoic microfoss i l record of the Nor th Sea

r e g i o n h a s b e e n t h e s u b j e c t of s e v e r a l

b io s t r a t ig r aph ic s tud ies . I n the mos t comprehens ive

zona t ion to da te , K ing (1 9 8 3) concen t r a te s on the

u p p e r p a r t of t h e s t r a t i g r a p h i c r a n g e s o r t o p s of

a l m o s t 1 0 0 b e n t h i c a n d o v e r 2 5 p l a n k t o n i c

fo ramin i f e r a , inc lud ing t axa o f d ia t om s an d s om e

M i o c e n e Bolboforma. S e v e n t e e n i n t e r v a l z o ne s

u s i n g b e n t h i c s a n d 1 6 u s i n g p l a n k t o n i c t a x a a r eproposed. The zonat ion is largely based on species

o c c u r r i n g i n t h e " o u t e r s u b l i t t o r a l - e p i b a t h y a l

b io fac ies " , w h ich in ou r t e rmino logy t r a ns la te s in to

o u t e r n e r i t i c t o u p p e r b a t h y a l e n v i r o n m e n t s . T h e

zona t ion appe ar s to be pa r t i cu la r l y u s e fu l for th e

a r e a a r o u n d t h e C e n t r a l G r a b e n . K i n g ( 1 9 8 3)

p rov ides an exce l l en t s um m ary o f the in te r r e la t io n

o f h i s z o n a t i o n w i t h t h a t d e v e l o p e d b y D o p p e r t

( 1 9 8 0 ) a n d D o p p e r t a n d N e e l e ( 1 9 8 3 ) f o r t h e

N e the r lan ds and by a num ber o f d i f f e ren t au t ho r s

f or s h o r t e r s t r a t i g r a p h i c i n t e r v a l s i n D e n m a r k ,

W e s t G e r m a n y a n d E n g l a n d . T h e e l e v e n - f o l d

as s emblage zona t ion deve loped by D opper t and co w orker s fo r the N e the r lands u s es ove r 9 0 s pec ies

(mos t ly ca lca reous ben th ic t axa ) , typ ica l o f s ha l low

t o d e e p n e r i ti c e n v i r o n m e n t s .

Ioak im (1 9 79 ) s tud ied the d ino f lage l l a t e s ucces s ion

in the co res from t he Es s o N o rw ay 1 6 /1 -1 w e l l ,

c e n t r a l N o r t h S e a . N i n e ( p r e l i m i n a r y ) a s s e m b l a g e

z o n es w e r e d i s t i n g u i s h e d f ro m P a l e o c e n e t h r o u g h

Ear ly M iocene and co r r e la ted to Rocka l Bank and

L a b r a d o r Shelf. The mos t r ecen t o rgan ic mic ro fos s i l

zonat ion for the Cenozoic of the Nor th Sea is that of

Cos ta ( in p res s ) . Tw en ty concu r ren t r ange zones a r ep ropos ed us ing bo th appea rance and d i s appearance

99



o f t a x a in W e s t e r n E u r o p e , N o r t h S e a a n d

No r weg ian Sea . I t i s p r im ar i ly i n t en d ed f o r r eg io n a l

co r r e l a t io n s of Pa l eo cen e th r o u g h P l io cen e s t r a t a .

Un f o r tu n a te ly , l i t e r a tu r e o n th e ac tu a l o ccu r r en ces

of the zonal taxa in the No r th S ea wel ls s tud ied by

us for fo ram in ifera i s non -ex i s ten t . For th is reas on i t

i s n o t p o ss ib l e t o d o a f i r s t - o r d e r co r r e l a t io n to

C o s ta ' s zo n es .

INTERFOSSIL PROBABILISTICDISTANCE SEQUENCE

0.5881 0.3427 0.0974

0.7108 0.4654 0.2200 -0.0253

PLIO-PLEISTOCENE

Early-middle

Miocene

iULate Oligocene-

Early Miocene

Rupelian

(earlyOligocene)

X iLate

Eocene

Middle-

?late Eocene

Ypresian

: s ^ !

m

i :

[fEarly

Ypresian-

late

Selandian

Selandian

JZ

Danian

2 2 8 0 . 2 7 57 C a s s i d u l i n a t e t e t i s

7 7 0 . 0 6 4 8 E l p h i d i u n s p p ,

3 1 0 . 1 4 35 C i b i c i d o i d e s s c a l d i s e n s i s

2 1 0 .3 2 1 1 S i g i o i l o p s is s c h l u t a g e r i

2 6 ! 0 . 5 5 70 N e o g l o b o q u a d r i n a a t l a n t i c a

2 0 7 0 . 1 7 8 0 L o g m a r k e t G

2 1 ! 0 . 0 1 4 1 S a r t i n o t i e l l a c y l i n d r i c a

1 0 ! 0 . 1 9 5 5 C a u c a s i n a e l o n g a t a

1 5 0 . 2 5) 3 G l o b i g e r i n a p i a e b u l l o i d e s

2 3 8 0 . 0 3 8 ! G l o b o r o t a l i a p t a e s c i t u l a z e a l a n i i c a

) 1 0 . 0 0 74 ' N e o g e n e B a d i o l a n a n F l o o d

1 7 0 . 6 7 0 8 A s t e i i g e r i n a g u r i c b i2 0 8 . 1 5 6 8 G y r o i d i n a g i i a r d a n a

1 3 8 0 . 2 0 1 1 ' G l o b i g e r i n a a n g u s t i u m b i l i c a t a

1 1 1 0 . 0 9 74 ' G l o b i g e r in a e i a t . o f f i c i n a l i s

2 5 8 . 4 0 75 C o a r s e a g g l u t i n a t e d s p p .

) 7 0 . 0 9 2 9 C y c l a i ni i n a p l a c e n t a

1 8 2 0 . 2 4 4 7 S p i r o s i g n i l i n e l l a c o m p r e s s u s

1 4 2 0 . 0 1 9 ! ' G y r o i d i n a s o l d a n i i m a a i l l i g e r a

1 4 0 0 . 0 2 4 4 » o t a l i a t i n a b a l i m o i d e s

2 4 0 . 3 0 8 5 ' t u n i l i n a a l s a t i c a

1 8 3 0 . 0 8 2 5 C y c l a n i n a r o t u n d i d o r s at a

2 6 2 0 . 0 1 3 2 K a r r e r i e l l a h o r r i d a

2 0 6 0 . 0 3 6 ! L o g d a r k e r F

1 4 ! 0 . 6 8 3 5 ' G l o b i g e r i n a t h e k a i n d e x

2 ! 0 . 1 9 0 1 B e t i c u l o p h r i q j i u . i l a i p l e c t e n s

4 6 0 . 2 8 1 7 ' A d e r c o t r y i a s p . 12 4 5 0 . 0 0 7 5 ' H a p l o p b r a g m o i d es j a r v i s i

2 6 1 0 . 1 5 3 4 H a p l o p h r a g m o i d e s w a i t e r !

1 1 7 0 . 0 1 33 E o c e n e R a d i o l a r i a n F l o o d

2 6 4 0 . 0 3 0 5 K a r r e r i e l l a c o n v e r s a

6 8 1 . 0 9 1 4 S p i r o p l e c t a n i n a s p e c t a b i l i s L 02 0 5 0 . 0 1 9 2 L o g M a r k e r E

8 6 0 . 0 3 7 2 ' T u r r i l i n a r o b e r t s i

2 6 0 0 . 2 2 43 H a p l o p h r a g m o i d e s k i r k i

2 6 3 0 . 0 7 6 8 A a o b a c u l i t e s a f f . p o l y t b a l a i ns

4 5 0 . 0 1 0 2 ' B u l i i in a t t i g o n a l i s

5 4 0 . 0 3 4 6 S p i r o p l e c t a m m i n a n a v a r r o a n a

5 0 8 . 4 6 85 S u b b o t i n a p a t a q o n i c a

2 7 ) 0 . 1 1 4 2 H a p l o p b r a g m o i d e s r e t r o s e p t u s

2 7 7 0 . 0 2 7 5 T u f f

2 2 0 . 0 8 0 3 C o s c i n o d i s c u s s p p .

2 0 4 0 . 1 0 0 4 L o g m a r k e t D

1 6 3 0 . 1 2 3 5 C y s t a m m i n a p a u c i l o c u l a t a

2 0 3 0 . 0 0 1 ! L o g m a r k e r C

1 6 3 0 . 1 4 6 2 G l o m o s p i r e l l a s p

1 1 0 0 . 1 8 ( 7 C y s t a m i n a a f f . g l o b i g e r i n a e f o r m i s

7 8 0 . 0 ( 2 8 T r o c h a o i n o i d e s c o r o n a t u s

7 i 0 . 0 2 7 9 R e t i c u l o p h r a g m i i » p a u p e r a

5 7 0 . 0 8 6 7 S p i r o p l e c t a n i n a s p e c t a b i l i s L C O

1 0 5 0 . 1 3 1 1 R z e h a k i i a m i n i m a

6 5 0 . 0 3 7 3 ' R e t i c u l o p b r a g m iu m g a r c i l a s s o i

1 3 4 0 . 1 2 ( 8 H o t n o s i n a e x c e l s a

1 2 9 0 . 1 9 30 t i o c n a m i n a r u t b v e n m u r r a y i

2 5 1 0 . 5 8 00 ' A n n o d i s c u s p l a n u s

2 5 3 0 . 0 7 S 8 S u b b o t i n a t t i l o c u l i n o i d e s

( 1 0 . 0 3 0 7 S u b b o t i n a n s e u d o b o l l o i d e s

( 0 0 . 1 2 ( 1 P l a n o r o t a l i t e s c o m p r e s s u s

2 0 2 0 . 2 1 ( 1 L o g H a r k e r B

1 0 7 0 . 0 2 9 7 H a t a m i a » a r i a n s

5 5 G a v e l i n e l l a b e c c a r i i f o r m i s

• I• I• I

! i

•• i

F i g . 2.

Average stratigraphic distribution of twenty-nine agglutinated benthic foraminifera, Cenozoic, central North Sea.

Isolated first or last ocurrences are shown with dashed lines. The zonation to the left is the scaled optimum sequence for the average tops of 54 foramini

fera and siliceous microfossils and physical log markers A-G in 29 wells. Dendrogram values along y-axis are distances between events in relative time.

Scaling is stratigraphically downward, in line with the study of the wells. The generalized ten-fold zonation is representative for the regional Cenozoic

stratigraphy (see text). There are 11 unique events (= rare events) shown with **. A shading pattern has been used to enhance the stratigraphically most

useful part of the dendrograms. The large interfossil distances at the top of the Danian, Late Selandian-Early Ypresian, Middle-Late Eocene, Late Eocene-Early Miocene and Middle Miocene are sedimentary cycle boundaries.

10 0

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CENTRAL NORTH SEA ZONATION (A gte r ber g and Nel 198 2a ,b ; G ra ds te i n andAgterberg 1982; Gradstein et al. 1985). Ranking is a

T h e s t r a t i g r a p h i c d i s t r i b u t i o n o f t h e l o c a l p a i r w i s e c o m p a r i s o n t e c h n i q u e t h a t t r i e s t od isappearance leve ls of 147 ben th ic fo ramin ife ra , de te rm in e the m os t l i ke ly se qu en ce o f

including over 60 agglutinated and some planktonic bio strat igra ph ic e ven ts as recorded in differe nttaxa in 29 exploratory wells, was investigated using s t ra t igra ph ic sec t ion s. Scal in g de ter m in es thethe ran kin g and sc alin g (RASC) m etho d. T his spacing of these events in relative time, using the

m et ho d can pr oc es s a co m pl ex an d no is y frequency of cross-over in re la t ive posi tion of thestratigrap hic record for stratigrap hic zonations, and events in the wells. The r ela tiv e po sition of thedeal with the record in an objec t ive m an ne r events in the f inal ranke d and scaled opt im um

101



s e q u e n c e s i s e s s e n t i a l l y a n a v e r a g e of a l l t h e

r e l a t i v e p o s i t i o n s e n c o u n t e r e d . I n t h i s s e n s e t h e

RASC zona t ion i s no t vu lnerab le to ou t l i e rs in the

o r i g i n a l d a t a . T e s t s o n s t r a t i g r a p h i c n o r m a l i t y o f

t h e i n d i v i d u a l ( w e l l ) r e c o r d r e l a t i v e t o t h e

c a l c u l a t e d s t a n d a r d r e v e a l w h e r e t h e o u t l i e r s a r e .

D e t a i l s o n d a t a p r e p a r a t i o n , t h e m e t h o d , d a t a

p r o c e s s i n g a n d i n t e r p r e t a t i o n o f r e s u l t s a r e i nG r a d s t e i n etal. (1985) . The res u l t s p rese n ted in th i s

s t u d y w e r e a c q u i r e d w i t h a p e r s o n a l c o m p u t e r

v e r s i o n o f t h e R A S C p r o g r a m , u s i n g a n I B M - X T

w i t h m a t h e m a t i c a l c o - p r o c e s s o r , 5 1 2 k R A M a n d

E P S O N M X d o t m a t r i x p r i n t e r .

A c lose look a t t he Nor th Sea ana ly t i ca l da ta shows

tha t the sou thern wel l s (b locks 21-38) con ta in more

O l i g oc e n e - M i oc e n e c a l c a r e o u s t a x a , i n c l u d i n g

s e v e r a l s p e ci e s o f p l a n k t o n i c s , t h a n t h e n o r t h e r n

wel l s wh ich con ta in a mor e d ivers i f i ed Pa leo cen e

a g g l u t i n a t e d r e c o r d . T h i s p a t t e r n o f g e o g r a p h i c

d i f f e r e n t i a t i o n w a s f u r t h e r c o n f i r m e d u s i n g

c o r r e s p o n d e n c e a n a l y s i s (G . B o n h a m C a r t e r ,

p e r s o n a l c o m m u n i c a t i o n , 1 9 8 5 ) . T h i s m e t h o d

c l a r i f i e s t h e s p a t i a l d i s t r i b u t i o n o f c o - o c c u r r i n g

t a x a . T h e r e m a y be s e v e r a l r e a s o n s f o r t h i s

b iogeograph ic t rend , one o f them be ing the fac t t ha t

the p r inc ipa l deep-water connec t ion was to the nor th

in the Norweg ian Sea . The l a t t e r reg ion does no t

h a v e m u c h of a n i n d i g e n o u s p l a n k t o n i c r e c o r d .

A n o t h e r r e a s o n is t h a t t h e p o s t - D a n i a n , L a t e

Pa leocene-Eocene ba thya l muds tone fac ies d id no t

p r e s e r v e m u c h o f a c a r b o n a t e r e c o r d , o w i n g t o

d iagene t i c e f fec t s (Grads te in and Berggren 1981) . At h i r d r e a s o n is c l i m a t i c ; a p p a r e n t l y t h e t r a n s i t i o n

f ro m c a r b o n a t e - r i c h t o c a r b o n a t e - p o o r r o c k s i n

Cenozo ic t ime can be t raced f rom sou th to no r th over

t h e c e n t r a l N o r t h S e a ( Z i e g l e r 1 9 8 1 ) . T h e

b i o g e o g r a p h i c a n a l y s i s i n d i c a t e s t h a t f o r d e t a i l e d

r e g i o n a l s t u d i e s t w o z o n a t i o n s a r e r e q u i r e d , o n e

e m p h a s i z i n g t h e n o r t h e r n P a l e o g e n e r e c o r d a n d t h e

o t h e r t h e s o u t h e r n O l i g o c e n e - M i o c e n e r e c o r d . I n

th i s s tudy we s t res s the genera l i zed zona t ion which

c o m b i n e s f e a t u r e s fr o m b o t h t h e C e n t r a l G r a b e n

a n d V i k i n g G r a b e n d e e p - w a t e r t r o u g h s .

The genera l i zed Cenozo ic Nor th Sea zona t ion usest h e R A S C t h r e s h o l d s k c = 8 an d m c = 5 , w h i c h

m ea ns th a t zona l t axa m us t occur in 8 o r more ou t o f

29 wel l s and each pa i r o f t axa in the sca led op t imum

sequ ence in 5 o r mo re wel l s . Th i s th resh o ld redu ces

the o r ig ina l da ta se t o f 147 even t s to 49 , i nc lud ing 8

p l a n k t o n i c a n d 25 a g g l u t i n a t e d t a x a a n d t h e l o g

m a r k e r s A - G of K n o x a n d M o r t o n ( p e r s o n a l

com mu nica t io n , 1984) , as found in the ma jo r i ty o f

w e l l s s t u d i e d . T h e h i s t o g r a m s t h a t d i s p l a y t h e

i n t e r f o s s i l d i s t a n c e s b e t w e e n t h e r a n k e d t a x a

( f ig u r e 2) a r e q u i t e s t a b l e w h e n R A S C r u n s w i t h

o t h e r k c and m c t h r e s h o l d p a r a m e t e r s a r e u s e d . F o r

e x a m p l e , w e t r i e d k c = 9 and 10 and m c = 6 an d 7 ,

which incorp ora te 45 and 41 t ax a respec t ive ly . In

a l l cases the same zones a re recogn ized .

I n o r d e r t o e n h a n c e t h e z o n a t i o n w i t h i n d e x t a x a

tha t a re ra re o r o ther t axa tha t a re though t to be

p o t e n t i a l l y of s u c h u s e , t h e R A S C m e t h o d a l l o w s

in t rodu c t ion of so -ca l l ed spec ia l o r un iqu e ev en t s

(UE) . Twelve even t s were se l ec ted tha t occur in l es st h a n k c = 8 w e l l s , b u t a r e w o r t h n o t i n g . T h e s e

even t s a re the h ighes t occur rence o f ( f rom o ld to

y o u n g ) Amm odiscus planus, Reticulophragmium

garcilassoi, Bulimina trigonalis, Turrilina robertsi,

Haplophragmoides (?) jarvisi, Adercotryma sp. 1 ,

Globige rinatheka index, Turrilina alsatica,

Globigerina ex g r . officinalis, G. angustium bilicata

and Neogen e rad io la r i an f lood. In the f ina l RASC

c a l c u l a t i o n s , s t r a t i g r a p h i c n e i g h b o r s of t h e s e e v e n t s

ar e iden t if i ed . A ne ighb or i s a spec ies tha t occurs in

the sca led op t imum sequence and a l so in the wel l ( s )

w i t h t h e U E , a n d s t r a t i g r a p h i c a l l y a s c l o s e a s

p o s s i b l e to i t . E a c h U E i s p o s i t i o n e d h a l f w a yb e t w e e n t h e s e n e i g h b o r i n g e v e n t s i n t h e s c a l e d

o p t i m u m s e q u e n c e .

Ten in t e rv a l zones a re recog n ized ( f igu re 2 ; t ab le 2 ) ,

w i t h t h e c h a r a c t e r i s t i c t a x a l i s te d s t r a t i g r a p h i c a l l y

i n o r d e r o f a v e r a g e d i s a p p e a r a n c e . A m o r e d e t a i l e d

zona t ion (which uses lower k c a n d m c v a l u e s ) i s

poss ib le for loca l co r re l a t ion . The reg iona l (deep-

water ) zones a re f rom o lder to younger :

Zone

A ge

T a x a

Zone

A ge

T a x a

Subbotina pseudobulloides

Da nian (Zones P I - P2)

Gavelinella beccariiformis, Matanziavarians, Planorotalites compressus,

Subbotina pseudobulloides a n d S.

triloculinoides.

T h i s z o n e c o r r e s p o n d s t o K i n g ' s ( 1 9 8 3 )

Z o n e o f t h e s a m e n a m e a n d a g e .

Gavelinella beccariiformis h a s b e e n

repor t ed f rom sed imen t s as young as Zone

P5 (T ja l sma a nd Loh ma nn 1983) . Th i s f it s

w i t h i t s d i s a p p e a r a n c e a l o n g t h e

C a n a d i a n A t l a n t i c m a r g i n t o g e t h e r w i t h

Aragonia velascoensis and jus t be low th e

a p p e a r a n c e o f Pseudohastigerina ( p o s t

P5) , ( G r a d s t e i n et al. 1985, p . 346). In thec e n t r a l N o r t h S e a t h e d i s a p p e a r a n c e o f G.

beccariiformis i s a p p r o x i m a t e l y 5 m . y .

ear l i e r , and may be re l a t ed to the change

n e a r t h e e n d of t h e D a n i a n f r o m

p r e d o m i n a n t l y c a r b o n a t e t o c l a s t i c

s e d i m e n t s .

Trochammina ruthven murrayi -

Reticulophragmium paupera

S e l a n d i a n , L a t e P a l e o c e n e ( Z o n e s P 3 -

P4) .

Ammodiscus planus ( U E ) , Trochammina

ruthven murrayi, Hormosina excelsa,

10 2



Table 2.Correlation of the foraminiferal zonation for the Central and Viking Graben, North Sea, with the standardcalcareous planktonic biostratigraphy and the nerit ic North Sea zonation of K I N G (1983).

EPOCH Blow »79 TH IS STU D Y King I 9 8 3

Quaternary

Pliocene

Ü JZÜ JOo

C D

c< D

ÜOO)

LÜZ

LüÜoUJ

Io v

— OJ

cd oQ_

L

M

± E

M

L

E

N I 9 -N 2 I

? N 6 -Nl I

? P 2 I -N5

P I 5 -P I7

P 6 b - P 8

P 5 - P 6 b

P 3 - P 4

P I - P 2

Cassidulina teret is

G l o b o r o t a l i a p r a e s c i t u l a

G . z e a l a n d i c a

G l o b i g e r i n a

ex gr . o f f ic in a l is

Ro t a l i a t i n a

bulimoides

G l ob i ger i na t heka i ndex

R e t i c u l o p h r a g m i u m

a m p l e c t e n s

S u b b o t i n a p a t a g o n i c a

Cosc inodiscus spp .

•kSubbot ina pseudobui lo ides

NSP

NSB7

NSP8

NSB5

NSB4

NSP5-NSB3

NSP4

NSP2-NSBI

NSP I

*

Reticulophragmium garcilassoi (UE) ,Rzehakina minima, Spiroplectamminaspectabilis L C O ( l a s t c o m m o n o rc o n s i s t e n t o c c u r r e n c e ) ,Reticulophragmium paupera,Trochamminoid.es coronatus.T h e o v e r l a p in o c c u r r e n c e o fTrochamm ina ruthven murrayi,Rzehakina minima and the p r imi t ivec y c l a m m i n i d s ß . garcilassoi an d R.

Tr ocham m i na r u t hven m ur r ay iR e t i cu l ophr agm i um pauper a

paupera is typical of the lower LizardsSpring Formation in Trinidad of P I to P4a g e ( K a m i n s k i et al., t h i s v o l u m e ) .Primitive cyclamminids are also knownfrom the Late Paleocene-Early Eocene ofAustralia (Ludbrook 1972) and Tunisia(F .M.Grads te in , unpub l i shed ) . In theNorth Sea wells studied, the zone occursabove carbonate-rich sediments of Danianage. In some wells the positions of the

103

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events in th is zone and in the ove r ly ing

Coscinodiscus Z o ne a r e o v e r l a p p i n g ,

which i s the r eason why the two zones a re

not c lea r ly sepa ra ted in the h is tograms of

f igure 2 . Based on the e s t im a te for the age

o f t h e Coscinodiscus Z o n e o f L a t e

S e l a n d i a n ( S p a r n a c i a n ) - E a r l y Y p r e s i a n

( see be low) , the Trochammina ruthuenmurrayi-Reticulophragmium paupera

Z o n e i s o f S e l a n d i a n a g e . I t p r o b a b l y

equa te s wi th pa r t o r a l l o f King ' s Zone

N S P 2 ( l a r g e r a d io l a r i a ) .

Zone Coscinodiscus s p p .

A g e L a t e S e l a n d i a n - E a r l y Y p r e s i a n , L a t e

Pa leocene -Ear ly Eocene . (Zones P5-P6b) .

T a x a Cystammina aff. globigerinaeformis,

Glomospirella s p . , Cystammina

pauciloculata, Coscinodiscus spp . , ( la rge ,

p i l l b o x - s h a p e d p y r i t i z e d d i a t o m s ) ,

vo lcan ic a sh in sed im en t ( tu f f) an d logmarke r s C and D (a sh beds of low sonic

ve loc i ty ) .

The a sh- se r ie s in te rva l ( the Se le and the

lower pa r t o f the Ba ld e r Form a t ions ) ha s

b e e n a s s i g n e d t o t h e Apectodinium

hyperacanthum Z o n e ( S p a r n a c i a n ) ,

e x t e n d i n g u p w a r d s i n t o t h e Wetzeliella

astra-W. meckelfeldensis Z o n e s ( E a r l y

Y p r e s i a n ) , ( I o a k i m 1 9 7 9 ; K n o x a n d

M o r to n 1 9 8 3 ; M a lm et al. 1984) . The A.

hyperacanthum Z o n e s t r a d d l e s t h e

P a l e o c e n e / E o c e n e b o u n d a r y . A t D S D P

Si te s 401 and 550 on the Rocka l M arg in ,t h e d i s t a l e q u iv a l e n t s of t h e N o r t h S e a

tuf f s have been shown to l ie whol ly in

n a n n o f o s s i l Z o n e N P 1 0 , ( Ro b e r t s et al.

1 9 8 5 ) , w h ic h c o r r e s p o n d s to t h e E a r ly

Y p r e s i a n .

Zone Subbotina patagonica

Age Yp res ian , Ea r ly Eocen e (Zones P6b-P8) .

T a x a Subbotina patagonica, Spiroplectammina

navarroana, Bulimina trigonalis ( U E ) ,

Ammobaculites aff. poly thalamus.

This zone i s ea s i ly iden t i f ied because of

t h e o f te n r e d d i s h - c o l o u r e d , 3 - 1 / 2c h a mb e r e d g lo b ig e r in id s , r e f e r r e d t o b y

King (1983) a s G. ex gr . linaperta (Zone

N S P 5 ) , b u t b e l o n g i n g in Subbotina

patagonica. O t h e r p l a n k t o n i c s ( a l l r a r e

a n d i n o n e o r tw o w e l l s o n ly ) i n c lu d e

Acarinina densa ( w e l l 1 5 / 2 0 - 2 ) , A .

soldadoensis, A. pentacamerata a n d

Pseudohastiger ina wilcoxensis ( E s s o

N o r w a y 1 6 /1 - 1 ) . T h e z o n e c a n a l s o b e

r e c o g n i z e d in t h e R o s n a e s C l a y

( Y p r e s i a n ) o f D e n ma r k , i n t h e L a b r a d o r

Sea and in the Ypres ian of Be lg ium ( see

10 4

G r a d s t e i n a n d A g t e r b e r g 1 9 8 2 f or

rev iew) . The end of the S. patagonica p e a k

o c c u r s a t t h e b o u n d a r y of Z o n e s

N P 1 1 / N P 1 2 , w h i c h c o i n c i d e s w i t h t h e

u p p e r b o u n d a r y of t h e Morozovella

formosa formosa Z o n e , a t t h e t ime o f

Anom aly 24 , s l igh t ly o lde r tha n 55 m.y .

( Be r g g r e n et al. 1985) . Ammobaculites aff.polythalamus i n L a b r a d o r w e l l s o n

a v e r a g e d i s a p p e a r s i n t h e o v e r ly in g z o n e

of Reticulophragmium amplectens

( G r a d s t e i n et al. 1 9 8 5 ) . Textularia

plummerae in King's (1983) Zone NSB3 is

o u r Spiroplectammina navarroana.

Zone Reticulophragmium amplectens

Age Middle (- Late) Eoce ne

T a x a Haplophragmoides kirki, Turrilina

robertsi ( U E ) , Spiroplectammina

spectabilis LO ( la s t occur rence w i th f ew

s p e c i m e n s i n i s o l a t e d s a m p l e s ) ,

Karreriella conversa, E o c e n e r a d io l a r i a n

f lood, Haplophragmoides walteri, H.

jarvisi ( U E ) , Adercotryma s p . ( U E ) ,

Reticulophragmium amplectens.

T h i s l a r g e a s s e m b l a g e of m a i n l y

a g g l u t i n a t e d t a x a i s t y p i c a l fo r t h e

mass ive muds tone sequence be low leve ls

w i t h Globigerinatheka index a n d

Rotaliatina bulimoides ( s e e b e lo w ) , i n

w h i c h a g g l u t i n a t e d t a x a a r e l e s s

p r e v a l e n t . Haplophragmoides ( a f f . )

walteri in some we l l s d isappea r s in the

Oligocene Rotaliatina bulimoides Zone .

T h e i m m e d i a t e l y o v e r l y i n g z o n e w i t hGlobigerinatheka index i s p robably La t e

E o c e n e i n a g e . I n P o l a n d t h e p e a k

o c c u r r e n c e o f R. amplectens is in (so-

c a l l e d ) M i d d l e E o c e n e s t r a t a . In

L a b r a d o r - G r a n d Ba n k s w e l l s t h e a v e r a g e

d i s a p p e a r a n c e o f R. amplectens a n d t h e

o th e r a g g lu t i n a t e d t a x a i n t h i s z o n e i s

w e l l b e lo w th e t o p s o f Turborotalia

pomeroli an d Globorotalia cerroazulensis,

P r i a b o n i a n , ( L a t e E o c e n e ) . I n t h e

Labrador Sea (ODP S i te 647) , the acme of

R. amplectens i s i n t h e M id d l e E o c e n e .

For th is r eason the R. amplectens Zone

ma y b e l a r g e ly M id d l e E o c e n e i n a g e ,

poss ib ly ex tending in to the La te Eocene .

The zone i s p robab ly cor re l a t i ve to t he

Zones NSB4 (Cylammina amplectens) an d

N S B 5 (Planulina palmerae) o f K i n g

( 1 9 8 3 ), a l t h o u g h N S B4 i s r e f e r r e d b y

King a s Ea r ly Eocene in age .

Zone Globigerinatheka index

Age La te Eocene

T a x a Globigerinatheka index ( U E ) , Karreriella

horrida ( i n c l u d e s K. apicularis),

Cyclammina rotundidorsata.



Zone

A g e

T a x a

Zone

A ge

Zone

Age

T a x a

The in t e rv a l zone i s es se n t i a l ly def ined by

the h ighes t occur rence in some wel l s o f

Globigerinatheka index. T h e a v e r a g e

d i sap pear ance o f the as soc ia t ed t ax a ha s

an "er ro rbar" o f a t l eas t one zone up and

one zone down. The G. index even t fa l l s

w i t h i n Z o n e N S P 8 o f K i n g ( 1 9 8 3 ) ,

e q u a t e d w i t h N P 1 6 a n d P 1 3 ( ~ P i 2 - P u ) ,Midd le Eocene . Such in t e rp re t a t ion re l i es

hea v i ly on an age of the eve n t in th e

D a n i s h S 0 v i n d F o r m a t i o n o f N P 1 6 - 1 7 ,

a l though in the Nor th At l an t i c Ocean the

t a x o n e x t e n d s f r o m P 1 5 - P 1 7 , L a t e

Eocene . In the sou thern wel l 38 /16-1 G.

index occurs wi th Cibicidoides truncanus

(King 's Zone NSB6a) , known f rom Zone

PI3 (Midd le Eocene) to top Eocene (Van

MorkhovenefaZ . 1986) .

Rotaliatina bulimoides

R u p e l i a n , E a r l y O l i g o c e n e ( Z o n e s P 1 8 -P19) .

Turrilina alsatica ( U E ) , Rotaliatina

bulimoides, Gyroidina soldanii

mammilligera, Spirosigmoilinella

compressus a n d Cyclammina placenta. In

severa l wel l s Heterolepa mexicana w a s

a l so found . Coa rse agg lu t ina ted b en th ic s

on average d i sappear in th i s zone , excep t

i n t h e s o u t h e r n w e l l s ( b l o c k s 2 1 - 3 0 ) ,

w h e r e t h e d i s a p p e a r a n c e i s o n e o r t w o

z o n e s h i g h e r , r e f l e c t i n g y o u n g e r

s h a l l o w i n g u p w a r d s . Spirosigmoilinella

compressus w a s r e c o r d e d b y G r a d s t e i nand Berggren (1981) as "Rzehakina" sp. 1 .

I n L a b r a d o r - G r a n d B a n k s w e l l s Turrilina

alsatica i s m o r e c o m m o n t h a n Rotaliatina

bulimoides i n beds o f the same age . The

R. bulimoides Zone co r responds to NSB7

(King 1983) o f the sam e nam e and ag e .

Globigerina ex gr . officinalis

Late Ol igocene-Ear ly Miocene (Zones ?

P 2 1 - N 5 )

I n s e v e r a l ( p a r t i c u l a r l y s o u t h e r n ) N o r t h

Sea wel l s th i s in t e rva l con ta ins common

to a b u n d a n t s m a l l , n o n d e s c r i p tg lob iger in ids . Th i s inc ludes the nomina te

spec ies , G. angustiumbilicata, G. opima

nana a n d r a r e l y G. ciperoensis. S a m p l i n g

r e s o l u t i o n i s l o w i n t h i s i n t e r v a l , a n d

Miocene cav ings and (?) rewo rked Eocene-

Ol igocene t axa hamper recogn i t ion o f th i s

in t e rva l zone , wh ich needs fu r th er s tudy .

Globorotaliapraescitula-G. zealandica

Ear ly -M idd le Miocene (Zones 7N6-N11)

Asterigerina gurichi, N e o g e n e r a d i o l a r i a n

flood (UE), Globorotalia praescitula a n d

G. zealandica, Globigerina praebulloides,

Caucasina elongata and Martinotiella

cylindrica.

I n s o m e w e l l s , p a r t i c u l a r l y a r o u n d t h e

Ekof i sk a rea , (b locks 22-30) , agg lu t ina ted

f o r a m i n i f e r a l i k e Cribrostomoides,

Glomospira, Bathysiphon, Hyperammina,

Trochammina, Reophax a n d Cyclamminae x t e n d i n t o t h i s z o n e , a s s o c i a t e d w i t h

c o m m o n p l a n k t o n i c s . T h e l a t t e r a l s o

inc lude Globigerinoides spp . , G. trilobus,

Globoquadrina dehiscens a n d G. aff.

baroemo ensis, Globorotalia praemena rdii,

Sphaeroidinella seminulina a n d t h e

Neogloboquadrina continuosa-

pachyderma-acostaensis g r o u p . A m o n g

t h e b e n t h i c s r a r e Uvigerina e x g r .

basicordata a n d U. semiornata kusteri

occur.

Zone Cassidulina teretisAge Midd le P l iocene-P le i s tocene (Zones N19-

N21)

T a x a Cibicidoides scaldisensis, Elphidium spp .

a n d Cassidulina teretis.

In the 16/1-1 wel l by Esso Norway these

ben th ics co -occur be tween 1285 and 2300 '

w i t h t h e p l a n k t o n i c s Globorotalia

crassaformis, G. puncticulata, G. inflata,

Orbulina universa a n d Neogloboquadrina

atlantica-pachyderma of Middle Pl ioc ene

( l a t e N19-ear ly N21) age . The same zone

w i t h s i m i l a r ( r a r e ) p l a n k t o n i c s o c c u r s

a l o n g t h e L a b r a d o r a n d G r a n d B a n k s(Grads te in and Agterberg 1982) .

R A N G E C H A RT O F A G G L U T I N A T E D B E N T H I C

F O R A M I N I F E R A

A p p r o x i m a t e l y 3 0 t a x a o f a g g l u t i n a t e d b e n t h i c

f o r a m i n if e r a h a v e d is t i n c t s t r a t i g r a p h i c r a n g e s i n

the cen t ra l Nor th Sea wel l s s tud ied . The majo r i ty o f

t axa has been re fe r red to in the t ex t d i scuss ing the

t e n -f o l d z o n a t i o n . R e m a r k s w e r e a d d e d o n

s t ra t ig raph ic occur rences in o ther geo log ica l bas ins .

A c o m p r e h e n s i v e s u m m a r y f or t h e s t r a t i g r a p h i cr a n g e s o f t h e a g g l u t i n a t e d b e n t h i c t a x a i s i n t h e

r a n g e c h a r t o f f i g u r e 2 . T h e t e n - f o l d i n t e r v a l

z o n a t i o n , w h i c h i s d i r e c t l y b a s e d o n t h e s c a l e d

op t imum sequence shown to the l e f t o f the char t , has

been t i ed to the geochrono log ic sca le on the r igh t

u s i n g a g e s of s e l e c t e d e v e n t s . T h e s e a g e s a r e

e s t i m a t e s u s i n g t h e c o r r e l a t i v e e v i d e n c e p r e s e n t e d

i n t h e t e x t a n d a r e b a s e d on la s t o c c u r r e n c e d a t u m s :

Cibicidoides scaldisensis

Globigerina praebulloides

Globorotalia praescitula

Rotaliatina bulimoides

2 M a

15

17

31

105



Globigerinatheka index 38

Reticulophragmium amplectens 4 0

Turrilina robertsi 49

Subbotinapatagonica 5 5

L o g m a r k e r D 5 8

L o g m a r k e r C 5 9

Subbotina pseudobulloid.es 63

T h e s t r a t i g r a p h i c r a n g e o f mo s t a g g lu t i n a t e d t a x a

in f igure 2 i s d iv ided in two or th ree pa r t s . A so l id

l i n e s h o w s t h e a v e r a g e r a n g e b a s e d o n t h e r a n k in g

a n d s c a l i n g r e s u l t s . T h e d a s h e d l i n e i n d i c a t e s t h e

ma x imu m o r t o t a l r a n g e b a s e d o n o b s e r v a t i o n s i n

ind iv idua l we l l s . Due to the na ture of the ma jor i ty o f

samples ( cu t t ings) the lower ha l f o f r anges i s le ss

r e l i a b l e . T h e t o t a l r a n g e o f Haplophragmoides

walteri p r o b a b ly e x t e n d s b e y o n d P a l e o c e n e - E o c e n e ,

b u t t h i s a w a i t s fu r t h e r t a x o n o m ic s t u d y . W i th m in o r

mo d i f i c a t i o n s t h i s r a n g e c h a r t ma y a l s o b e u t i l i z e d

fo r r e g i o n a l c o r r e l a t i o n s i n L a b r a d o r a n d

N e w f o u n d la n d o f fs h o re b a s in s . T h e mo s t im p o r t a n td i f fe r e n ce s a r e t h a t in t h e w e s t e r n A t l a n t i c

c o n t i n e n t a l m a r g i n b a s i n s Arenobulimina does no t

e x t e n d i n t h e T e r t i a r y , Rzehakina epigona r e p l a c e s

R. minima, Trochamm ina ruthven murrayi i s

a b s e n t a n d Cystammina pauciloculata,

Ammobaculites a f f . polythalamus a n d

Haplophragmoides kirki r a n g e u p i n t h e

Reticulophragmium amplectens Z o n e , M id d l e - ? L a t e

E o c e n e .

S T R A T I G R A P H I C P O S I T I O N O F L O G M A R K E R S

A G

T h r o u g h t h e c o u r t e s y of D r s . A .C . M o r to n a n d R .

K n o x ( B .G .S . , K e y w o r th , U .K . ) w e r e c e iv e d d e p th

p icks for the i r log m ar ke r s A-G in the we l l s s tud ied .

T h e s e lo g m a r k e r s a r e t h o u g h t to b e

c h r o n o s t r a t i g r a p h i c i n n a t u r e an d a c c o r d i n g t o

M o r to n a n d K n o x ( p e r s o n a l c o mmu n ic a t i o n , 1 9 8 4 )

cor re spond to the fo l lowing approxima te leve ls :

M ark e r G - top Middle M iocene

M ark e r F - top Upp er Eocen e

M a r k e r E - t o p E a r ly E o c e n e

M a r k e r D - t o p S e l e F o r m a t io n ( or e q u iv a l e n t )

M a r k e r C - b a s e S e le F o r m a t io n ( t op P a l e o c e n e )

M a r k e r B - t o p E k o f i s k F o r m a t i o n ( t o p E a r l y

Pa leocene )

M a r k e r A - t o p Cr e t a c e o u s

W e ex p e c t e d t h e lo g p i c k s t o v a r y s l i g h t l y i n

s t r a t i g r a p h i c p o si t io n r e l a t i v e to t h e f o r a min i f e r a l

e v e n t s i n t h e w e l l s a n d t r e a t e d t h e l o g p i c k s a s

" fo s si l e v e n t s " i n th e RA S C c a l c u l a t i o n s . F ig u r e 2

s h o w s t h e a v e r a g e s t r a t i g r a p h i c p o s i t i o n o f a l l

e v e n t s . T h e r e i s g oo d a g r e e m e n t b e tw e e n t h e a g e s

ass ign ed by Knox and Mo r ton to the log p icks and

the ages a ss igned by us to the accompanying zones .

L o g ma r k e r A i s a lw a y s fo u n d a t t h e l e v e l w i t h

Globotruncana be low the Danian zone (no t shown in

f igure 2) . Log m ark e r B on ave ra ge i s in the Da nian ,

r a th e r t h a n a t t h e to p a s s u g g e s t e d . L o g m a r k e r s C

and D a re in the Coscinodiscus Z o n e t h a t d e l i n e a t e s

th e a s h - s e r i e s , t h a t s t r a d d l e s t h e P a l e o c e n e - E o c e n e

b o u n d a r y .

The top of log m ark e r E i s g iven a s top of Ea r l y

E o c e n e i n a g r e e m e n t w i th i t s a v e r a g e o c c u r r e n c e

s l i g h t l y a b o v e t h e Subbotina patagonica Z o n e ,

Ypres ian . The on ly se r ious except ion to th is ave rage

pos i t ion w as found to be in we l l 23 /22-1 wh ere E

o c c u r s w i th D a n i a n p l a n k to n i c s . T h e l a t t e r m a y b e

r e w o r k e d .

Log marke r F occurs in the Globigerinatheka index

in te rva l , La te Eocene . Log m ar ke r G f i t s we l l a t the

top of the Globorotalia praescitula-G.zealandica

Z o n e , E a r l y - M i d d l e M i o c e n e . A n i n t e r e s t i n g

o b s e r v a t i o n i s t h a t t h e m a r k e r s F a n d G a r ea s s o c i a t ed i n f i g u r e 2 w i th b r e a k s i n t h e s c a l e d

o p t imu m s e q u e n c e . T h e s e b r e a k s a r e r e c o g n i z e d b y

l a r g e i n t e r f o s s i l d i s t a n c e s b e tw e e n tw o e v e n t s i n

a d j a ce n t z o n e s . T h e l a r g e d i s t a n c e me a n s t h a t t h e r e

is l i t t l e o r no c ross -ove r in pos i t ion b e tw een the

events in the two zones . Such a s i tua t ion i s expec ted

w h e r e t h e r e i s s t r a t i g r a p h i c s e c t i o n m i s s i n g

be tween the zones or a sudden change in f ac ie s (may

a l s o be d u e t o a h i a tu s ) . T h e l a t t e r i s t h e c a s e

b e t w e e n t h e D a n ia n a n d S e l a n d i a n z o n e s , w h e r e

c a r b o n a t e s a r e r e p l a c e d b y mu d s to n e s a n d s a n d s .

A s m e n t i o n e d e a r l i e r , i n c o m p u t e r r u n s w i t h o u tu n iq u e e v e n t s s u c h a s Globigerinatheka index, lo g

m a r k e r F f a l l s e x a c t l y a t t h e l a r g e i n t e r f o s s i l

d i s t a n c e b e tw e e n t h e Rotaliatina bulimoides Z o n e

a n d t h e u n d e r l y i n g Reticulophragmium amplectens

Z o n e . L o g m a r k e r F m a r k s t h e E o c e n e - O l ig o c e n e

boundary in the zona t ion and the la rge in te r foss i l

d i s t a n c e a s s o c i a t e d w i t h i t s u g g e s t s a h i a t u s

in v o lv in g t h e u p p e r m o s t E o c e n e t o E a r ly O l ig oc e n e .

I n r u n s i n c l u d i n g u n i q u e e v e n t s , t h e

Globigerinatheka index-log m a r k e r F e v e n t s a r e

s a n d w i c h e d b e t w e e n t h e R. bulimoides a n d R.

amplectens Z o n e s , i n d i c a t i n g t h a t t h e s e e v e n t s a r e

closely t ied to the p osit ion of a hia tu s in m any (?) of

t h e w e l l s . T h e s e o b s e r v a t i o n s r e q u i r e mo r e d e t a i l e d

s tu d y .

Log m ar ke r G re f lec ts a La t e Miocene h ia tu s in the

we l ls in the cen t ra l Nor th Sea grabens . Few of the

we l ls s tud ied show unequivoca l foss i l ev idence for a

L a t e M io c e n e i n t e r v a l ( b a s e d o n r a r e p l a n k to n i c

f o r a m i n i f e r a i n c l u d i n g Neogloboquadrina

atlantica,left coi lin g + N. acostaensis).

Anothe r b reak in the r ecord i s sugges ted a t the base

of the Globorotalia praescitula-G. zealandica Zone ,

O l i g o c e n e - M i o c e n e b o u n d a r y . A m o r e d e t a i l e d

106

http://pseudobulloid.es/





a n a l y s i s of t h e n a t u r e o f t h e b r e a k s a n d t h e r e a s o n s

for i t i s beyond th e scope o f th i s com mu nica t io n .

D I A C H R O N O U S E V E N T S ,

S P I R O P L E C T A M M I N A S P E C T A B I L I S LO A N D

L C O

O n e o f t h e f e a t u r e s o f t h e R A S C m e t h o d i s t h e

a b i l i t y t o t e s t e a c h i n d i v i d u a l w e l l s e q u e n c e for

s t r a t i g r a p h i c n o rm a l i t y (G ra d s t e i n et al. 1985) . The

t e s t d e t e c t s w h i c h t a x a i n t h e i n d i v i d u a l w e l l s a r e

o u t l i e r s , r e l a t i v e t o t h e s c a le d o p t i m u m s e q u e n c e .

Fo r exam ple , the l as t occu rren ce o f S . spectabilis

(LO) and i t s l as t commo n o r con s i s ten t occ u rrenc e

( L C O ) , w h i c h w e re t r e a t e d a s s e p a ra t e t a x a i n t h e

ca lcu la t ions , were found to be ou t o f s t ra t i g ra ph ic

p o s i t i o n 5 a n d 7 t i m e s r e s p e c t i v e l y , w i t h a

p r o b a b i l i t y e x c e e d i n g 9 5 % . F u r t h e r a n a l y s i s s h o w e d

t h a t in t h e s o u t h e r n w e l l s ( b l o c k s 2 3 - 3 0 ) , S .

spectabilis LO i s res t r i c ted to the Pa leocene (be low

the as h-s eri es) ; in the b lock 16 we lls i t is found oneo r two s tages younger a t the top o f the Subbotina

patagonica Z o n e a n d t h e b a s e o f t h e

Reticulophragmium amplectens Zone . In the b locks

9 and 3 wells i t is at the top of the R. amplectens

Z o n e . T h i s m e a n s t h a t t h e l a s t o c c u r r e n c e o f

Spiroplectammina spectabilis m i g r a t e s u p w a r d s i n

t ime f rom Late Pa leocene in the sou thern wel l s to

La t e Eo c e n e in t h e n o r t h e rn N o r t h S e a w e l l s .

The (average) l as t common occu rrence (LCO) o f th i s

f o r m is a l w a y s b e l o w t h e a s h - s e r i e s i n t h e

Reticulophragmium paupera-Trochamm ina ruthven

murrayi Zo n e . Th i s a c m e a p p a re n t l y e x t e n d e d o n t othe she l f fac ies o f Wes te rn Europe . I t i s shown by

Dopper t (1980) in the Pa leocene o f the Nether lands ,

e x t e n d i n g s l i g h t l y i n to th e Ea r l y Eo c e n e .

A l o n g t h e C a n a d i a n A t l a n t i c m a r g i n

Spiroplectammina spectabilis i n g e n e ra l d o e s n o t

occu r above the Acarinina densa Zone , Ea r ly M idd le

E o c e n e , a l t h o u g h i n O D P S i t e 64 7 , c e n t r a l La b ra d o r

Sea i t i s found as h igh as N P2 1 . In th i s ocea n ic s i t e ,

i t i s found as h igh as co re 29 , 20 m above the

a s s i g n e d Eo c e n e -O l i g o c en e b o u n d a ry .

A C K N O W L E D G E M E N T S

W e g r a t e f u l l y a c k n o w l e d g e t h e s u p p o r t w i t h

s a m p l e s a n d o t h e r w e l l d a t a of t h e f o l l o w i n g

c o m p a n i e s a n d o r g a n i z a t i o n s : B P ( A b e r d e e n a n d

S u n b u r y ) , C o n o co ( L o n d o n ) , D a n i s h G e o l o g i c a l

S u r v e y ( C o p e n h a g e n ) , E s s o ( S t a v a n g e r ) , E P R E

( B o r d e a u x ) , M o b il ( L o n d o n ) , N P D ( S t a v a n g e r ) ,

P h i l l i p s ( L o n d o n ) , P a l e o s e r v i c e s ( W a t f o r d ) ,

R o b e r t s o n R e s e a r c h (L l a n d u d n o ) a n d S h e l l (Lo n d o n

a n d Th e H a g u e ) .

A . C . Mo r t o n a n d R . K n o x (B G S , K e y w o r t h ) k i n d l y

d o n a t e d t h e v a l u a b l e d a t a o n t h e d e p t h a n d

es t im ated ag es of the phys ica l log m ar ke rs . F . Rög l

(V i e n n a ) , S . G e ro c h (K ra k o w ) , G . J o n e s (U n o c a l ,

B r e a ) , M . B r o l s m a ( S h e l l , U . K . ) , C . S c h r ö d e r

(Hal i fax ) and A. Gran t (Dar tmou th ) p rov ided adv ice

o n t a x o n o m y o r t h e m a n u s c r i p t .

Th is i s a con t r ibu t ion o f the Cenozo ic Deep Water

B e n t h i c F o ra m i n i f e r a p ro j e c t w h i c h w a s s u p p o r t e d

b y a c o n s o r t i u m o f o i l c o m p a n i e s ( A R C O , B P ,

Chevron-Gulf, E l f - A q u i t a i n e , E x x o n , M o b i l ,

P h i l l i p s , S h e l l I n t e rn a t i o n a l , S h e l l U S A , Te x a c o a n d

Unoca l ) . Th i s is Geo log ica l Su rvey o f Ca na da Pa per

No . 52286 .

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