3The Lexis Group, Albion House, 9 Atbion Avenue, Blackpool, Lancashire FY3 8NA, UK. Abstract: ...... 3 7 3 6 7 2 18 tr)f/. 3816412 .1521.1-15 ll-1. 15. 6312s35. 13. 2. 1. 5. I. 84. 1. 23. 53. 1 ...... spond to the Loucr Balmoral Sandstone riithin the.
Upper Paleocene-Lower Eocene dinoflagellate cyst sequence biostratigraphy of southeast England A. J. powELLl, H. BRINKHUIS2 & J. p. BUJAK3 t
Millennia Ltd, Unit 3, Weyside Park, Newman Lane, Alton, Hampshire GU34 2PJ, UK 2Laboratory of Palaeobotany and Palynology, University of []trecht, Heidelberglaan 2, 3584 CS Utrecht, The Netherlands 3The Lexis Group, Albion House, 9 Atbion Avenue, Blackpool, Lancashire FY3 8NA, UK Abstract: Detailed study of the aquatic palynomorph assemblages, particularly dinoflagellate cysts, from the type-Thanetian and related sections in southeast England has enabled a detailed biostratigraphic and sequence biostratigraphic analysis to be carried out. The base of the Thanetian Stage at Pegwell Bay lies above the base of theAlisocysta margarita (Ama) biozone; the overlying type-Thanetian is assigned to the Apectodinium hyperacanthum (Ahy) and Apectodinium augustum (Aau) biozones. The base of the Ypresian succession is drawn at the base of the Harwich Formation at Lower Upnor corresponding to the base of the Glaphyrocysta ordinata (Gor) biozone. The Wetzeliella asrra (Was) biozone is characteristic of the lower London Clay Formation at Herne Bay. Five Thanetian and three Ypresian sequences are identified through consideration of dinoflagellate cyst palaeoecology and sedimentological evidence. Deepening and shallowing trends enable transgressive and highstand systems tracts to be identified. The maximum flooding surfaces are identified and correlated into the North Sea Basin (Central Graben) as a series of eight primary condensed sections, two of which (characterized by the Areoligera and Apectodinium acmes) are of a second-order scale (the other six are third-order). Lowstand system tracts are represented onshore by a series of seven unconformities (type 1 sequence boundaries) with the amount of missing time below biozonal resolution. A single type 2 sequence boundary is also evident in the Ypresian succession at Wrabness. The unconformities may be conelated into more distal locations in the North Sea Basin where lowstand sandstone deposition is characteristic.
One
of the
objectives
of the
International
Commission on Stratigraphy (of the International Union of Geological Sciences) is the development of a global standard stratigraphic scale. As paft of this exercise, the remit of the International Subcommission on Paleogene Stratigraphy (ISPS) is to review and, if necessary, revise the definition of the ages/stages of the Paleocene EpochL/Series (see Schmitz 1994). The ISPS has decided that the Paleocene Series be divisible into three stages,
namely Danian, Selandian and Thanetian (see Jenkins & Luterbacher 1992). The Paleocene Working Group of the ISPS has set itself the objective of assessing the relative merits of various global events which might be used to define the base of the Selandian and Thanetian stages, and to
recommend the Global Stratotype Section and Point (GSSP) for each stage. In view of the fact that one of the requirements for a GSSP should be as complete a sedimentary succession as possible, it is important that the type-Thanetian should be reappraised from a sequence stratigraphic perspective. After all, from a classical perspective, the base of the Thanetian Stage can be no older than the
of the type-Thanetian (i.e. the contact of the Thanet Sand Formation with the Chalk Group ai Pegwell Bay, Kent, UK). It is primarily in this context that the present study has been undeftaken.
base
Aims of the study The principal purpose of this study is to provide a detailed interpretation of the sequence stratigraphy of Upper Paleocene and Lower Eocene sediments exposed in southeast England on the basis of the
aquatic palynological (primarily dinoflagellate cyst) stratigraphic record. The scale of inquiry is such that systems tracts may be deduced from the biostratigraphic data (see Powell 1992a), th:us necessitating a closely-spaced suite of samples. By so doing, it is possible to test third-order cyclicity represented in the rock record. By considering the details of a well-exposed set of strata in a relatively proximal setting, it is possible to deduce the stratigraphic relations with those located more
distally within the Nofth Sea Basin. A number of predictions may be made concerning the proximal expression of primary condensed sections (Powell
Ftzm Knox, R. W. O'8.. Corficld, R. M. & Duna1. R. E. (eds), 1996. Correlution Northuest Europe, Geological Societ.v- Spccial Publication No. 101. pp. 1,15 1tt3.
ct.f
the
Earlr Puleogent,
itt
145
t46
A. J. POWELL ETAI.
1992a) expressed more fully in distal locations in
the basin.
In
addition. unconfbrmities apparent
proxirnally (onshore) may be traced towards their correlative conformities in distal localities otTshore as secondary condensed sections (Poweli 1992a) and basin-lloor lans.
Scope of the study
The sections examined are exposed in Kent and E,ssex (Fig. 11. The stratigraphic position ol the samples is shown in the stratigraphic summary logs (Figs 2-5). Dnling April 1991. two of us (AJP and
HB, with the guidance of Mr David J. Ward) collected 28 sarnples fiom Pegwell Bay (Fi-e. 2); two samples wele obtained from the Upper Chalk, 18 fiom the Thanet Sand Formation (Base-Bed, Stor-rrmouth Clays and Pegwell Marls) at the cliffend section, Pegwell Bay. anci eight lurther san'tples
flom the adjacent hoverport car-park
section
(Pegwe1l Marls and Recuh,er Silts). At Herne Bay (Fig. 3), the eastern cliff section (tbLrr samples fiom
the Oldhaven Member of the Harwich Formation) were sampled (AJP, HB and DfW). A further four samples were also obtained from the western cliff section from the Oldhaven Member into the London Clay Formation. At the Lower Upnor sandpit (Fig. a) the Reculver Silts of the Thanet Sand Formation (two samples), the Lambeth Group (the Upnor and Woolwich Formations - 12 samples) and the Oldhaven Member of the Harwich Formation (five samples) were sampled (AJP and HB). At the cliff section of Wrabness, Essex (Fig. 5), 15 samples from the Wrabness Member of the Harwich Formation were obtained (AJP and HB).
The average gap between samples were: at the cliff-end section (Pegwell Bay) 45 cm, at the hoverport car-park (Pegwell Bay) 43 cm, at the eastern cliff section (Herne Bay) 105 cm, at the foreshore section (Heme Bay) 135 cm, at the westem cliff section (Heme Bay) 136 cm, at the sandpit (Lower Upnor) 127 cm, and at the cliff section (Wrabness) 102 cm. The key references were: for Pegwell Bay Ward (1977), for Herne
the Reculver Silts). the foreshore section (12 samples from the Reculver Silts. through tl-re
Bay Ward (1978), for Lower Upnor Kennedy & Sellwood (1970), and for Wrabness King
Woolwich Bottom Bed of the Upnor Formation to
(198 1).
2' 50 kn
tonbridqe -a 52' Wrobn
e
rt'
Horw
ich
LONDON
a
Herne 8oy
Lower Upnor
Pegv 0ov
e
ll
Boy
er
al'
t' Fig. 1. Location map of the Pegwell Bay, Herne Bay, Lower Upnor and Wrabness sections.
t41
PALEOCENE-EOCENE DINOFLAGELLATE SEQIJENCE BIOSTRAIiGRAPHY
slides were prepared using glycerine jelly as the mounting medium. The slides were studied both qualitatively and quantitatively. The quantitative analysis comprised a count of 200 aquatic palynomorphs where possible. For this purpose, six broad palynomorph
The Laboratory of Palaeobotany and Palynology,
University
of
Utrecht, undertook
all the
prep-
arations using standard techniques. Heavy liquid (ZnCl) separation of the material was applied and residues were sieved using a 10 pm precision mesh sieve. After mixing to obtain homogeneity, four
PEGWELL BAY STRATIGRAPHIC SUMMARY LOG park Kent,U.K.
SECTION: Cliff & car
STRATIGRAPHERS: AJP, HB, JPB
ffffi
COUNTY:
SCaf-E:
IiEnll Sandsrong
LOCATION: TR 3545 CHRONG STRATIGBAPTI\
U =
F
E U
o
z
g F
o
F
zo
-
U
o
E
o
@
E = o
U = =
f=
z
o U 6
g o
I F l
U
zu l
U
= 4
tr
tz
F
a
u o u
F
d
19
o
s
E
a
I
s F
16
a F
()
N
J
I
HE
F
l
N
N
U
;8
z
OINOFLAGELLATE CYST BIOEVENTS
6
(m.tr.s)
i Eq ;=
I
:
(r
35 AE .k
d
:a
Srrefl debris
U
h
:uF
66311
F 2
SEOUENCE
STNATIGRAPHT
N
U
m fllll Si[stone El
lfm
SAMPLES: PBI - PB28
LtTtio-
z a U
6440
Conglomerate F_T= Ctaysrone
mls
2
TS SB1
_ -. -
?l-
PB28 PB21
G.
A.
P-B?q
intiata
ILO).
lmpoversh.ddinoc-yst eemblag€.
nercilib
tLO\.
-F G. @s;tuius_f6r , c. spa@sun stabw \Fo). E S. @/nul6 (FOl, C nAailitLof. +- C. qadbtFot. F- . lmFwnsh€d dinoclst ss6mbhg€. ( I f.1,-T"1T !1",. L. @nnhb tFot P. brus@
F6ii PB23 PB21
(Fo_),
^
6 E
o
c
o
c o
;
L
o
;L o
o o l
c
!
o
!
E
@
6
F
c l
c 6
c o a c d t F
:
G
F
6
o,
a I
=
s E E
;o o
+
o
c F 13
_ _ _
z
mis
c o !
(.)
_ -
10
@
s
I
O
E
p Ee -
8
F @
9
a
k* Bed
c 2 TS SB1
= = -
Fig.2.
Stratigraphic summary 1og for Pegwell Bay.
PB1{
PBlI PB1; PB1(
i--
PBll PBl,
-|_
PBli PB1:
FE -PB1! P81( ai - pE6 =a - EBA
F
E
PB2{
EBi PB2
P c,enutatun \FOl. A saroransE (abLdanr/. lfiporenshd d,noqsl ssefibtags. A.
7 .-FFI = 'L -
s@nsBb l$udat).
A. saronereis
(suFrabudant).
I LPutjT !19):!: 2n-!il tFPt.!: n:nb?n?Ma I r vr r. rd,€rd rrv), e. qv4@ra\rv), u_ oeote@rcA I (FOI. A oiDDheftk tabu*nil (siFrabund'anr) r. aargarra (FO), | A *rc.;;i6arp
r &bonu (FO), C. tb.ospthBun IFOI Ah;cqhs}2 [ (FO), C. 6rc/6m Ge. \FO), H. thbrun cry_ \fO} lmpowrishd dimqst a3sambtage.
1
|
D. dentbubt a tf O), P nagoitbun tFOt, c. Eudolur€rus (FO), S. ssptatus {FO).
IS
Bailenol Fynomorph6. A. serorere,scrp. (suFrabundanl). Baren ol palynomorphs. Baasn ol palynomophs.
P81
-
@datht lt
q.
A. J. POWELL E7A'.
i48
HERNE BAY STRATIGRAPHIC SUMMARY LOG SECTION: Cliff &
foreshore STRATIGRAPHERS: AJP, HB, JPB
couNTy: Kenr, u.K. LOCATION: TR 210
z u
I rm
SAMPLES: HB1 .
LITHO. STRATIGRAPH\
CHRONG
=
SCar-E:
688
o o o F
4
-o
F
U
zg
E
o
o
o F
l 6
E =
o
= o
= =
!
o U
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zU
F o
= 6
U
I
F
,s
U = F
F
a
o
a F
o
5
TS
! m
; 6 T
E o
c
N
3or \
-
E
) 6
C
I W.6tallo), D. @bdeEaEs t6-hor). C. s@cbsm , h@muphuh. A. qunquetdum, | tsudar). Ptarmprmeita spp tommont lfFvonshod assomb aF w lh fte.osperm€lla
il
sDo
Bsrsn ol Frynonorohs
)
o l
s
d
=
g
p
6
N
I-
o
E
) ,
-H816
I
e
\6
6
_H8r
Btr,sn or F yiomo,phs e-Mr". 4 Ddly-a FO E I O. , ao.,tor,",'" r-r, rO & tor r' ro-oro,pru, (aD-rc.' I A s"qnx-I a mrcsa rLo I @.--r.s'LO M r.ro,.r--'LO'
i A atcaotdu iLA), S spralls (LO), G. pss&b/r iLO), A serc.oreis (LO) P tidta lLOl L hyahna tLo).
4
K
o l--
o
F
E
u)
F
@
zi TS SB
^L
;
SB1
m
o
o
c o N o
a
F a I
E
BIOEVENTS
-H818
F
o
O
o
DINOFLAGELLATE CYST
-H819
_H817
)
6.Or'"
o
E
E F
56"11
\
-HB2O
mls
SB1
o
cnatr
El
Siltstone
lmetres\
!
i
ffi
llll]l
Io
68)
c
a I
lil.lTl Sandsrone
u z o N
-i
a o E;
clavstone
Conglomerate
@
16 o=
E
E
U
P
o a
HB2o
SEOUENCE U
El
ffiS
P crcnulatun
-H813 -H812
S Foudolu.€rus
I
c
ILO).
-H811
,
L. hyal)natFOt,
(LO)
G cesicutuslLOl.
M.
pseoetecoNatDr
o
c
o
;c o
o o l
'tr
G
o
;
o
c
.g
e
c 6 E F
! o E
o a O
:
c f,
c d ! F
EH
o
o
o o
86
I
L,n.
l_,*
mls
.g
F
a F
6 E
co
a
o Fig. 3. Stratigraphic summary log for Heme Bay
:
*
lmpveished dimqsl
ass€mblag€.
to
6
c
€l
5
.E
c F
f
tr
.E
I D
o
6 C
a =
E
6 e
o
o
a
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!_
F !
cr
P gotzo'|ense lFo)
o
l-'*
l-,",
q
IrI_
F I
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l. I
P /drae lFo)
ano.o.o,pnu-$O
Acot.-Lrtr6!n,FOl
I A ,ob6ruD iFo), M trnbnat'n tFO)
PALEOCENE-EOCENE DINOFLAGELLATE SEQUENCE BIOSTRAIIGRAPHY
149
LOWER UPNOR STRATIGRAPHIC SUMMARY LOG SECTION: Sandpit STRATIGRAPHERS: AJP, HB, JPB fiffi Conglomerate E= Ctaystone COUNTY: KenI, U.K. scaLE: ffisandsrone mchatk lrm LOCATION: TO759711 SAMPLES: LUI - LU19 IITI 531151sns El Stretl debris CXRONG
LITHO.
z
z
N
u = ts
s
u
u
F
E
-q tti Jd
o
Iq
z o
-
A f o E
o
tr
E
u
E
=
c
o =
8 J
z
o U o
F l
E
6 c F
o
-
.9
-
o z
3 o u
E
o
.r1?
F
u = F
F U) I
g
15
E o
o .; c
-:
,
; o
c
o
o
o o o
o o o o
o L
;
q
o
o l
!
o
o c 6 E F
o
! o ! e d J
u7 JO dE =k G
hE l.o
EUE
J6
6 N o O
oo oo r0 0 I&TT I I
O r=
E$
F H
5
t. a F
o
! g\
a0
tri
t56
A. J. POWELL E7AL.
?"o
^o^eor&
\n bru
oo".
"% oo.
%,\ \
hrn. "a. o
f5f3) J J
N
i
o
66N
33)))f!) ! J J J JJJ
JJJ
O
J !..i
a
'ug o.
H)IMUVH
NOIIVhIUOC HJIM'IOOM
NOIIVhITIOC UONdN
I
6
bo
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al
a
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3
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6
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tr]toN-oooNoro+oNi -FdOOOOOOOOO EtrtrMEOtr6E6NODtrE aa)a))>a)a))>aa uJ ,-\vlt NocNo'l
NOLtYhIUOd HJIMUYH
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23 3E
s-q >2
f>
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t
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fs.E,F'rE;r dNrij^i-N hm a6 66
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bo
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M
B o E
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o
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F (^
i,
=3 ul
A
.jl
F F
LD
F.
o o .o L
o N 5!
I
PALEOCENE*EOCENE DINOFLAGELLATE SEQUENCE
BIOSTRAIIGRAPHY
159
?%.o toor,
nu*
"oz^
/t\
4u-
".4 I
a
ffi
+/-
?n, -*ru*: 4+. -.",
U
..2
.%
oo*
ril
?lu
rrt (/)
\+2.
--1-1
0
%
/'f*r-----1---,--
P._
A
aa^
-%.-
oo. a 4-
-?.
?^
I
7o)
! /-T'\
-t-
''b^ "1. 27,
a o
%
d E
r+,
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.t^ I
o\
T-r_l
o
ln$ONiOOoNOlnSONrdidiFooooooooo
a
trooatrnoootrtrtrtrnE
o
3
-a)aa)ar>>,)>); wc
l.vtlNmNo'l
NOIIYhDIOJ H]IMU\/H
o-
o
bo
pi
EO o
5E !!6
se
J E
a
E
o
o !0
s
bo
=:
3z
E
bo
dd
FF
i E
E
N
N
..'
'a
I O
o d o
6q
bo
si* b.9P B-.E (,(,]
F (, F
F (DS ,1.
Lr i^P ts
=
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(.) o0
tr
A. J. PO:V,IELL ET AL.
160
Table 2. Aquatic palynomorph distribution (counts) at Heme Bay
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 t9 20
Samples HB Taxa
72
A. gippingensis A. robustunt
1
Alisoc y-sta sp. 2l Ge rdiocy'sta? sp. indet. M. pseudorecttn-atum Thalas,s ipho
ra spp. undiff.
S. psetdofurcatus T. peLagica
S. septatus
A. senonensis s.l. G. pcrstieLsii O pe rc tio diniLutt spp. undiff.
C.? minimum
ridium spp. undifT.
R. bortts.sica H t sr ric hokol pom,r
1*l +1 +13
2
1
**3+31
3
21 *1 1
P. crenulcttwn
P o L -r'sphae
119
:pp. undit'i.
1.. comntuni.s
M. fimbriatunt C. fibrospinosum
Foram test linings O. centr)carpunt F ib roc.t" s trt spp. undiff. G. divaricata s.l. G. ordirtata Acanthomorph ac rita rc hs C. graciLe C. inrtdes
inidiniuxt ? spp. undiff. C. speciosum
Sp
A. cornufrulitosum S. ramosus
A. ramuliJbra H. tLtbiferLtm A. alcit'ornu
I 8611 12413 421 2 6 3 9 61813 I 4 23 5 511 1 9 9391523 6 3 s11 *151 61 ""91 *****+**2 1l 23 *11* *l ** **11 *l *1 144J584*2 137610 13028 9 1 5112131 815 ll 12 l0 3 t1 1.7 21 2 9 l8 15 t9 11 10
*+1
26 4
*
13'71 19 2.1 31 46
21 1*** * 5 1 2 2 ')r1s1?i_L
13 I 8 1,1 29 17
610t3 4 7
-s
* 2 1 I 6 I 2161316 610 1312'7 2 6 2 7 510 4 3 I 5 510171Trt 81.119 3'7 712.15
I 1
9
5
2
8
t 9
2
34
1
1
32 I
I
2
9 2
1
58 31 43 23 25 17 42 31 61 56 51 2'7 39 39 42
s1319131612 8 5 3 61120182910
16*113251.1 63112111
+3113
12
1
37 2t
10 11
1
3
* present outside of count.
lowermost Upnor Formation (Lambeth Group). Knox e/ al. (1994) presented a reappraisal of the magnetostratigraphy of the type-Thanetian succession.
Biostatigraphy Apart from dinoflagellate cysts, the most intensively studied microfossils from the type-Thanetian have been the calcareous nannofossils and a full review is given by Siesser e/ al. (1987). These authors have also carried out the most detailed analysis of the stratigraphic distribution of these microfossils from Pegwell and Herne Bays. Their findings suggest that the lowermost 4.2m of the
Thanet Sand Formation is assignable to biozones NP6-7, and the overlying part of the formation belongs to biozone NP8. Knox (1990) believed an NP7 biozonal allocation to be likely for the lower Thanet Sand Formation. However, more recently, Knox et al. (1994) assigned the lowermost Thanet Sand Formation (Stourmouth Clays) to biozone
NP6 and the Reculver Silts to biozone NP8 (the Pegwell Marls being unassignable). Knox (1990) suggested that the Upnor Formation of the Lambeth Group may be assigned to biozone NP9 (with an unconformity at its base). According to Knox (1990), the 'Oldhaven Beds' of the Harwich Formation, and the overlying London Clay Forrnation, belong to biozone NP10 (with an unconfonnity at the base ofthe 'Oldhaven Beds').
161
PALEOCENE-EOCENE DINOFLAGELLATE SEQUENCE BIOSTRATIGRAPHY Table
2.
Continued
01 02 03 04 05 06 07 08 09
Samples HB Taxa
lidiae inium spp. undiff. C. intricata cr spp. undiff. P te ro sperme l-e o s ph ae r d ia spp. undiff. H. tumpanukt P.
Apte od
I I
C. medcalfii
15
anc|rea
11
2
)+ l1
undiff.
1
1
D. sintpler P. magnilicum b
t'
c' I
op s ie
I I
cL
I
20
15
i0
1
3
H. mentbrmtiplnntm
C
2
l1 620 3
L. cl. h.:,alina
runt
H orno I r -r b I inm spp.
12 71818 4 29932 36
* 8 618
4
16 36
28
213
*
31 111
43
1
l1
4
spp. undifT.
1
3
1
undiil.
2
3
1
D. denticLtLata
*
L. htalina Ta s nnnite.s spp. undiff. P he lotlinium ? sp. indet. D. oebislbLlensis A. suntntissum T. delicata A. cf. quittyrelatum A. cf . 1lartum A. pan,Llrt
46
14
2t *+
1l*2* 1l
P. golLtwense
i42
111
1
52
+l
24
t 1
1 8 11
Apectodinirun spp. unditT. A. cluintlttelatunt
!il.
3 1
1
Tectatctdini un ? sp. indct.
Subril i sp hue ru ? spp.
20
1*2
23 2 s
i
C. s pe c ios tutt gla
t4 t5 16 17 18 t9
1t4
1i:+ * 111*' 16 2.t957 222'7
C. tlepressum
S-
12 13
52
A. hornomorpl'ttort
i
t0 ll
1
12 12
ustra
t
Source: Heiimann-Clausen 1985. x present outside of count.
P
revious dinoflagellate
cy
st studies
studies have been carried out on the dinoflagellate cyst assemblages from the type-
A number of
Thanetian and these have been reviewed by Powell
(1992b). These previous studies had biostratigraphic or palaeoenvironmental objectives and were conducted on a relatively coarse scale. Thus, although broad correlations are possible throughout nofthwest Europe (and second-order palaeoenvironmental trends are apparent), detailed sequence biostratigraphic analysis has hitherto not been possible.
To summarize, it is well known that Areoligera spp. and Alisocysta margarita are cha-racteristic of the Thanet Sand Formation (Husain 1967; Downie
al. 1971; Allen 1982; Jolley 1992). From a biostratigaphic perspective, both Costa & Downie
et
(1976) and Costa e/ al. (1978) assigned the Thanet Sand Formation to the Deflandrea speciosa biozone and the Lambeth Group to rhe Wetzeliella (Apectodinium) hyperacantha biozone. Costa et al.
(1978) allocated the London Clay Formation of Kent to the Wetzeliella (W.) astra and W. (W.) meckelftldensis biozones. Costa et al. (1978) wete
allocate the 'Oldhaven Beds' of the to any biozone due to the absence of key species. Knox e/ al. (1981) suggested that the 'Oldhaven Beds' lie within the A. hypercanthum biozone. Heilmann-Clausen (1985) was able to correlate the Thanet Sand Formation at Pegwell Bay (his biozone 4, and the unable
to
Harwich Formation
t62
A. J. POWELL ETA'.
Table 3. Aquatic palynomorph distribution (counts) at Lower (Jpnor
SamplesLU
01 02 03 0,+ 05 06 07 08 09 t0 11 12 13 11 t5 16 11 18
t9
Taxa e r
14 9 .+:l -s0 l1 29 6 1 1l 33 15 5 53 40 t8 12 9 3 8 16 11 4 .+6 7 15 1 5 1 7 14
O. cetirocarpum Le i o.s p ha
idia spp. undiff.
Acant horno rp h ct c: r i ta rc hs P ediastnnt spp. undiff. H. abbreyicttum
i:1 *925
A. hlperuconthum H. tenuispinoswn
1299 1211 I 3 7 5730 2 1 31.+ 6-s86 5 8 86
A. quinquelatLtm A. partuttt Apectodiniutn spp. undiff. A. hornomnrphum
ll 17
A. conttfrutico.sum
2
1.+u
ll3* *1 23 3 I 13 11 -s 3 :,. 3 12 1522 9 3.1 253 21 113 +22 21 13ltl
Deflandreoids undiff. Bat iaca sphuera spp. undiff. G. d*aricatct P o l1'sp hae r i d ittm spp. undiff. L. mochaerophorum
A. senortensis s.l.
t tt m P. indentotct A. robustturt Adna t o.s p hae ridiunz spp. undiff. Co rdos phae rid i url spp. undiff. L
13 I
1
7 I t1 r,+ *61
1l
1
D. colligerunt H. tubiferum
12
C. irtodes F.
s
5
2 321 20 5 9 '+ I
S. fttntosus L. cortnrumis M. fimbrkrLtm
G. ordinata G. intricata M. p.s e u d o re c Lt n- t
*
7
fe ro.r
H. plectilLtnt Fi b rocy's ta spp. unciitT. C ri b ro p e r id ini um spp. undifT.
2
ApteodiniLtm spp. undifT. S. nteniltrttnacetts G. pa.stielsii
12
I 7
T. deLicatu P
te
ro s pe rm
eII
3+
o spp. undifT.
x present outside of count.
Ama biozone of Powell 1992b) with the Holmehus
Formation
of the Viborg 1 borehole in
Jutland, Denmark. Similarly, he conelated the formation at Heme Bay (his biozone 5, and the Ahy biozone of Powell1992b) to the 'Grey Clay' lying berween rhe Holmehus arld @lst Formations in the same borehole, despite the apparent absence of Apectodinium spp. Powell (1992b) assigned the Thanet Sand
Formation at Pegwell Bay to the Alisocysta margarita (Ama) biozone, and at Herne Bay to
the Apectodinium hypercanthum (Ahy) biozone. He placed the Lambeth Group in the Apectodinium augustum (Aau) biozone, and the 'Oldhaven Beds' of the Harwich Formation in the Glaphyrocysta
ordinata (Gor) biozone. The lower London Clay Formation was assigned to the Wetzeliella astra (Was) and W. meckelftldensls (Wme) biozones.
The only previous palynological studies of the Harwich Formation at Wrabness have been those
r.
*
PALEOCENE-EOCENE DINOFLAGELLAIE SEQUENCE BIOSTRATIGRAPHY
& Spinner (1989, 1991). They assigned the Harwich Formation to the Apectodinium hypercanthum biozone (sensu Costa & Downie 1976 and Costa e/ al. 1978) and restricted the succession of Jolley
above the Harwich Stone Band to the Deflandrea oe b i sfe ld
e
n
si
s acme biozone.
t63
Pegwell Bay dinoflagellate cyst
biostratigraphy Barren interzone Age: Indeterminate. Samples: PB I and PB2. Litho s trati graphy: Chalk Group.
Dinoflagellate cyst biostratigraphy of the studied sections Although the lowermost samples at Pegwell Bay and Lower Upnor are virtually barren of palynomorphs, most other samples contain reasonably well-preserved aquatic palynological associations
Comments: The
two samples from the Chalk
proved to be barren of palynomorphs and may not be assigned to any biozone. The Chalk Group is Coniacian to Santonian in age (Siesser et al. 1987).
Alisocysta margarita (Ama) intenal biozone
suitable for quantitative analysis. The results show that dinoflagellate cysts dominate the associations in most cases. Other categories of aquatic palynomorphs are only common to abundant in particular intervals of the Lower Upnor section and in the
Age:Thanetian (pars), Iate Paleocene (pars).
upper part
Comments'. The succession in the Base-Bed of the Thanet Sand Formation contains neither the index taxon of the Ama biozone (DeJlandrea denticulata) nor the nominate taxon (Alisocysta margarita).
of the Wrabness section. Samples from the Oldhaven Member at Herne Bay contain
virtually only Leiosphaeridi, spp.
and
Pterospermella spp.
In the dinoflagellate cyst assemblages usually only a few taxa or 'complexes' of moryhologically similar taxa are quantitatively important. In most samples, Spinferites ramosus, Achomosphaera ramulifera. Areoligera senonensis
group. G laphy ro cy s t a int ric at a, G. div ari c at a, C e ro dinium speciosum or C. medcalfii are common to abundant, and range throughout the investigated interval. In addition, Apectodinium spp. (mainly A. homo-
morphum) and Deflandrea oebisfeldensls are common in particular intervals. Cordosphaeridium spp., usually represented by C. fibrospinosum, C. gracile or C. inodes, may be common in some samples, as are representatives of Operculodinium centrocarpum, Homotryblium spp., Impletosphaeridium spp. and Polysphaeridium spp. The biozonation scheme applied in the present study is that of Powell (1992b). This scheme is defined by the range bases ofpaticular taxa; it has the additional advantage in that range tops may be extrapolated into the North Sea Basin. The major latest Paleocene and earliest Eocene palynological
(dinoflagellate cysts) bioevents occurring
in
the
North Sea Basin are shown in Fig. 14, while a comparison of published latest Paleocene and earliest Eocene North Sea palynological biozonations is presented in Fig. 15.
The acronyms FO and LO stand for first occuffence and last occurrence respectively. The relative abundance categories used in the present study are: rare( 60Vo) and present (outside of count).
Samples'. PB3-PB28.
Lithostratigraplzy: Thanet Sand Formation (Base-
Bed, Stourmouth Clays, Pegwell Marls
and
Reculver Silts, pars).
However, the superabundant occurrence
total dominance (l00%o) of members of
and
the
in sample PB4 is evidence for allocation of the Base-Bed
Areoligera senonensis group strong
to the Ama biozone. Furthermore, indicators of older biozones, notably Palaeoperidinium pyrophorum, are absent.
The sample at PB6 from the base of the Stourmouth Clays contains a highly impoverished assemblage which includes representatives of the Areoligera senonensis group. Other samples from the lower Stourmouth Clays (PB7-P810) are also
in terms of both specimen and species numbers. However, the occurrence of Deflandrea denticulata at PB7 confirms allocation to the Ama biozone. Phelodinium magnificum, C e ro dinium me dc alfii, Sp inife rit e s p s e udofurc atus and S. septatus all have their FO atPB7. Alisocysta marg.arita, the nominate taxon for the Ama biozone, has its FO at PB11 (upper impoverished
Stourmouth Clays) together with those of C o rdo sphae ridium fib ro spino s um, Alis o cy s t a sp.
2 of
Heilmann-Clausen (1985), Achomosphaera
alcicornu, the Cerodinium speciosum and the Hystrichosphaeridium tubifurum groups. The assemblage atPB12 is impoverished, but contains a reasonable recovery of both Areoligera senonensis and C e ro dinium me dc alfi i.
Moving into the Pegwell Marls (sample PB13), a number of FOs are apparent, including those of Diphyes colligerum, Hystrichostrogylon coninckii (only present in this sample), H. membraniphorum, Thalas siphora delicata, Glaphyrocysta divaricata
164
A. J. powELL ErA..
Table 4. Aquatic pa\'nomorph di.stribution (count.t) at Wrubness
01 02 03 04 05 06 01 08 09 10 11 t2 13 t4
Samples WB
15
Taxa G. exuberans
O. compler
1
P. subtile
2
L. disjunctum D. cladiodes s. Morg. F. bipolttris
3
I
Hy'stric hokolpoma sp. A. C. grocile
L. wetzelii O. cenlrocarpum
A. alcicornu
S. cf - membranar:eus
S. monilis
Senegolinium? sp. A.
1l
I
G. ordinatct s.L.
S. ramosus
H. tubferum G. divoricata D. ctebisJeldensis Acritarch sp. A Foram test linings
-5
ridium spp. undiff,
Acritarch
sp. B.
Le io sp ha
ridia spp. undiff
e
9 13
2l*1 1i1r224 9 t4 11 t3 8 4 6f325a 3 38 3'7 39 16 48 .13 23 22 16 lt 16 t8 2 7 5 9 4 8 l5 914213-5 I 3 7 3 6 7
T. cf. pelagica T. delicctta
P. indentata
*2
l+421 8 11 11 11 9 1234424 911121012137]1 4-5435431
A. rttultispinosum
A. ranruLiftrct
st
2* 2t
1
S. septatLts
Michn
I
t)a 84 2*2 23 53 365153 25586415 62513583 x514211 181281112168 122t1222
C. xtultispittosum S. cf. chlam"-dophora C. giuseppei
A. senonensis
22
13 2
.
1 5
tr)f/
3816412 .1521.1-15 ll-1 6312s35
and Deflandrea oebisfeldensis. The Areoligera senonensis group is superabundant at PB15.
Phthanoperidinium crenulatutn has
its FO
at
PB18. A generally similar assemblage is present at PB19 and it is at this sample position that the top of an acme (> 2OVo) of Areoligera may be placed (equivalent to bioevent P1 of Mudge & Copestake 1992; biochronoevent BC-7 of Armer,ttout et al. 1993; and bioevent Aga of Mudge & Bujak 1996). The assemblage at PB20 is highly impoverished but includes Areoli gera senonensis. A large number of taxa have their FOs atPB21 (uppermost Pegwell Marls), the most significant being Cerodinium depressum, Lejeunecysta
communis, Rottnestia borussica, Palaeocystodinium lidiae, Melitasphaeridium pseudorecurvatum and the Glaphyrocysta pastielsii grotJp.
The assemblage at PB22 (lowermost Reculver
8
3
16 49 18 18 t2 4 2
9 2
18
15
I
I
41 41
31527 21-s415 3 5 4 4 311
10
Silts) is impoverished in terms of specimen numbers, but nevertheless is generally similar in species composition to that at PB2l. The assemblage at PB23 contains the FO of Cordosphaeridium gracile, while that at PB24 of Cerodinium medcalfii and the FO of Spinifurites cornutus. A generally similar assemblage is present in PB25 but with the additional FOs of Impagidinium paradoxum, contains the LO
Gerdiocysta cassiculus and Cerodinium speciosum glabrum. The LO of Alisocysta margarita lies at PB26 (equivalent to bioevent P2 of Mudge & Copestake 1992; biochronoevent BC-8 of Armentout et al. 1993; and bioevent Alm of Mudge & Bujak 1996), while an impoverished assemblage is present at
PB27 broadly similar to that at PB26 in terms of species composition. The richer assemblage
165
PALEOCENE-EOCENE DINOFLAGELLATE SEQUENCE BIOSTRATIGRAPHY
4.
Thtrle
Continued
01 02 03 04 05 06 07 08 09 10 11 12 13 14
Samples WB
15
Taxa
A. bifomtoides F'. cf. vectense D. phophoriticcr C. pannttceunt M. psettdorecttnatum
1l 42 ;
pellitum
T.
D. colligerum P. t:renulatttm
R. borussica
H. mentbranipltorunt P te ro spe rme lo spp. unditT.
..,
3
646 22 ).
tl
2
I
O.? severinii
I
(ornutus
1
76 +2 +2 2152437
I. cctliforniense A. hy'peracanthunt
1
A. homomorphLun
1
wte cy'.s ttL spp. undiff. S. den.sispinottun A. pun'unt P. goli.ov'ense Le.j
1* 21 23 1
2 1
31 13
H. rigaudiae
3 I
C. speciosum
C. itnties e
dias t ru m spp.
5
undiff.
ra spp. undiff e s spp. undilf.
C _t'm a I io.s p htLe Tu.sm
u
rLi
t
+ present outside
1
1
e
P. rttagnificunt P. inversibuccirturtr P. rrtittust'ulum
P
1.1
1
pseudolurcatus
S.
1
*
I
1
1
3l 32 *2
2
35 12
G. pastieLsii
I
14 223
1
D. pastielsii
S.
t/l
+3 72 1l
C. depressum
2
*12
2
1
11
.
212 2453
:k
of count.
at PB28 is
characterized
by
abundant
Glaphyrocysta spp.
Mudge & Copestake 1992; biochronoevent BC-9 of Armentrout et al. 1993; and bioevent IA of Mudge & Bujak 1996); Apectodinium cornu-
of
fruticosum also has Herne Bay dinoflagellate cyst
biostratigraphy Apectodinium hyperacanthum (Ahy) interval biozone Age:Thanetian (pars), late Paleocene (pars). Samples: HBI-HBl4. Lithostratigraphy: Thanet Sand Formation
(Reculver Silts, pars); Lambeth Group, Upnor Formation (Woolwich Bottom Bed, pars).
Comments: The FO of Apectodinium homomorphum at HB1 is good evidence for allocation to the Ahy biozone (calibrated close to bioevent M5
its FO at HBl, as
do
Adnatosphaeridium robustum and Muratodinium fimbriatum. Other FOs of note include Palaeocystodinium lidiae at }{B2, P. gofuowense at HB9 and Lejeunecysta hyalina at HBl0, all within the Reculver Silts of the Thanet Sand Formation. There are, in addition, a number of LOs within the succession. At HB10, the LOs of Gerdiocysta cassiculus, Melitasphaeridium pseudorecurvatum, Adnatosphaeridium robustum, Alisocysta sp. 2 of Heilmann-Clausen (1985) and Areoligera gippingensls (equivalent to bioevent P2 of Mudge &
Copestake
1992 Biochronoevent BC-8 of
Armentrout et al. 1993; and bioevent Ag of Mudge & Bujak (1996) are all present, whlle Spiniftrites
t66
A. J. POWELL ETA'.
CHRONOSTRAT. uJ
Was
z uJ o o IU
z a
(E
tr
tIJ
3 o J
LU
o-
MAJOR PALYNOLOGICAL (DTNOFLAGELLATE CYST) BTOEVENTS
(Powell '92)
2-t
astra Cercdinium wardenense (acme) Glaphyrocysta ordinata (acme) Dellandrea oebisfeldensis (acme)
.-t tlJ c-t z z L) o Ahv ,-t o F Lt IU ul J z s-r oI F cc F r-r tIl Ama .J Aau Lt
TU
:) Ppv
-, L.,:r
@
H
/-. gv
/-. Y7
rr
Apectodinium Complex (acme) (P3) Apectodinium augustum s- Wills & Peattie (1 Muratodinium ApectodiniumComplex (acme), A. augustum s. Schroder (1992) Apectodinium
IJ .J
ao)
r1t
Cerodinium dartmoorium/Cerodinium speciosum glabrum
(L (L
i-1
990) fimbiatum paruum Adnatosphaeidium robustum Apectodinium Complex (persistenl), L. machaerophorum Areoligera gippingensis (P2) Rottnestia borussica (re-appearance) Alisocysta margarita (PZ) Phthanoperidinium Ateuilgera 5et tut |en5t5/Areoilgera gtPPutger,5rS (aurIe,l A reo I i g e ra se no n e n si s/Areol ig e ra g ippi n gensls (acme) D e fI an drea de nticul ata, Areo I i g e ra g ip pi n g e n si s Pal ae o pe ridi n i u m py rop ho ru m (persistent)
luiak, in prep)
Lr
wetzeliella
Deflandreaoebisfeldensis/Glaphyrocystaordinata(acme)
Gor 1) .-t |ir
Bioevenb (Mudge and
rout et ai.93)
crenulatum
rr B u L.,l! ll Ll
n,
+
l-.:l (
l-l ll
a @@ /fr
@
YY
tef q,
Fig. 14. Major latest Paleocene and earliest Eocene palynological (dinoflagellate cysts) bioevents occurring in the North Sea Basin.
pseudofurcatus has its LO at HB 1 1 at the top of the Thanet Sand Formation. Within the Upnor Formation of the Lambeth
Group (Woolwich Bottom Bed), the
LO of
Phthanoperidinium crenulatum is at HB13, while Achomosphaera alcicornu, Spiniferites septatus, Glaphyrocysta pastielsii, Areoligera senonensis, Palaeocy stodinium lidiae and Lej eunecysta hyalina all have their LOs at HB14.
(abundant) A. homomorphum. A number of species have their LOs at HB15. These include Rottnestia borussica, Lej eunecysta communis, Muratodinium .fimbriatum and Thalassiphora delicata.
Barren interzone Age: Indeterminate. Samples'.
HB16 and H817.
Lithostratigraphy: Thames Group; Harwich Formation (Oldhaven Member). Comments'. These two samples from the Oldhaven Member proved to be barren of palynomorphs and assignment to any biozone is not possible.
Apectodinium augustum (Aau) intenal biozone Age: Thanelian (pars), late Paleocene (pars).
Sample:}{815.
Lithostratigraphy: Lambeth Group; Upnor
Glaphyrocysta ordinata ( Gor) chronozone
Formation (Woolwich Bottom Bed, pars).
Age: Ypresian (pars), early Eocene (pars). Samples: HB18 and HB19.
Comments'. Although
the nominate taxon,
Apectodinium augustum, is absent in sample HB15 (it is believed to be restricted to more offshore parts of the basin), the Apectodinium complex accounts for 34.5Vo of the assemblage. This constitutes the
Lithostratigraphy: Thames Group; London Clay Formation, Basement Bed and Walton Member
FO of the Apectodinium acme and is taken
London Clay Fomation contains neither the index taxon (Phelodinium magnificum) nor the nominate taxon (Glaphyrocysta ordinata) of the Gor biozone.
as
for the assignment to the Aau biozone. The assemblage at HB15 also contains the FO (and LO) of Apectodinium parvum. This taxon is accompanied other Apectodinium species including summissum (FO and LO) and evidence (see Heilmann-Clausen 1985)
A.
by
(pars). Comments: The sample (HB18) at the base
of the
However, because the assemblages at HB18 and
(especially) HB19 are characterized
by
the
presence of Pterospermella spp. (common at HBl9) the base of the Gor chronozone (i.e. the
PALEOCENE-EOCENE DINOFLAGELLATE SEQUENCE BIOSTRATIGRAPHY
t$ G- f lo!a
C^ .=@ -YF (!0) O-
Es ua
o@
Ng EO
E
x9 o
a
esopads earpueuao
wnqueceladlq wnupotcadv
NE
f: 4(E
ic
q
wnputplo wnqaqdauopic
+
q-
(
(I)
.o .= oi t.
U
X
or.ucv stsueplaJStqeo
(!
C
c P
o
eJue6leu
wnqlueoeladlLl wnrupotcadv
eolpueuoo
_o
e$lcosttV
sEuauopJe/A
ON
;99 o) u,
stsdouelec
o b
wnlsn6ne wntupolcodv
elue6)ew
elslcosttv
o
EE 4v
X
(gc
aulsv stsuegaFqoo ealpueuaq
wn$n6ne wruupolcodv
o=
(c OG C od
o O)
:--
o
elsicostlv
o
s8
B3n
oo) c0 o-
E: (,
c)
6 6 6 E
fl $ IS
c)
$o
:o o N o
q-
s
o.
o oo
o 6
a ao c5
elue6Jew
o
elsloostlV
\
aa0-
C)
c0
C\I
F
F
N
orl
PO Vo) -c o-o,
o 2l5;< 4L
I
6
o
z o o
E]
o
q)
EE o-=
, ol o ol: F
d=oE
urn$n6ne'v
0)
60
\
o s
stsdouuac
a-
.t
(u
o
9tsuAuep)elvl
f o q
elue6Jew
lo
O-
\
aa.
tr
_o
CU
o
q-
co
oa9
a-
\o
G L^
:^ 0)co
161
o
C\I
o O
o o o
-0.
LO
o
d .d o
oa (g
=
b (, NVISf UdA
3N3CO3 USMO]
f CE
CO
E
NVI13NVHI
SN3COttVd Ufddn
ootos
-
E
O
ri 60
?
168
A. J. POWELL ETAZ.
Leiosphaeridia biofacies of Bujak & Mudge 1994) probably lies at H818. Glaphyrocysta ordinata does, howeveq occur at HB19.
Wetzeliella astra (Was) interval biozone Age: Ypresian (pars), early Eocene (pars). Sample: HB20.
Lithostratigraphy: Thames Group; London Clay Formation, Walton Member (pars). Comments: The occurence of Wetzeliella astra in the stratigraphically highest sample examined at Heme Bay (H820) indicates assignment to the Was biozone. Also characteristic of the assemblage is the common occurrence of Deflandrea oebis-
feldensis together with abundant Cerodinium speciosum, common Apectodinium species, notably
A.
homomorphum and
A.
quinquelatum, and
Pterospermella spp.
LUl0 in an assemblage
dominated
by
super-
abundant Apectodinium spp., notably A. homomorphum. This is taken as evidence for allocation to the Aau biozone despite the absence of the nominate taxon (see Heilmann-Clausen 1985). A generally similar assemblage is present at LU11
although Muratodinium fimbriatum
and
Lejeunecysta communis are additionally present. A. pantum also occurs at both LU12 and LU13,
although Apectodinium spp. as a whole are no
longer dominant. The FO of Lingulodinium machaerophorum lies at LU10. The sample at LU14 is impoverished, but Apectodinium spp. we again very well represented (particularly A. homomorphum) at LU15, which probably marks the LO of the Apectodinium acme (equivalent to bioevent P3 of Mudge & Copestake 1992; biochronoevent BC-10 of Amentrout et al. 1993; and bioevent Aa? of Mudge & Bujak 1996). Adnatosphaeridium robustum occurs at LUl5 as well as Diphyes colligerum.
Lower Upnor dinoflagellate cyst
biostratigraphy
Glaphyrocysta ordinata ( Gor) chronozone
Barren interzone
Age'. Ypresian (pars), early Eocene (pars). Samples: LU16-LU18.
Age: Indeterminate. Samples:
Lithostratigraphlt: Thames Group; Harwich
LU1-LU8.
Lithostratigraphy: Thanet Sand Formation (Reculver Silts, pars); Lambeth Group, Upnor Formation (Woolwich Bottom Bed) and Woolwich Formation (Woolwich Beds, pars). Comments: The eight samples obtained from the base of the Lower Upnor section proved to be baren of microplankton and may not therefore be assigned to any biozone. Samples from the Upnor
Formation at Herne Bay are productive and are assigned to the Ahy Biozone.
Formation (pars).
Comments'. Although
the marker
species
(Phelodinium magnfficum) of the Gor biozone is absent, Leiosphaeridiri spp. are particularly dominant in the two samples (LU16 and LU17) at the base of the Harwich Formation (biochronoevent BC-11 of Armentrout et al. 1993: Leiosphaeridia biofacies of Bujak & Mudge 1994). Allocation to the Gor chronozone is therefore appropriate. Also characteristic of the assemblages
is
superabundant Paralecaniella indentata;
Apectodinium homomorphum is present atLU16.
Imp ov e rishe d int e rzone
Glaphyrocysta ordinata occurs commonly at LU18 in an assemblage with Leiosphaeridia spp.
Age'. lndeteminate.
Sample:LU9.
wtd Pterospermella spp. present, but not common.
Lithostratigraphy: Lambeth Group; Woolwich
Also occurring at LU18 is Apectodinium homomorphum and common Hystrichosphaeridium
Formation (Woolwich Beds, pars). Comments: The sample at LU9 is impoverished both in terms of specimen and species numbers. Pediastrum spp., Leiosphaeridia spp. and undifferentiated acanthomorph acritarchs are present.
tubiferum.
Imp ov e ri she d int e rzone Age: Indeterminate.
Apectodinium augustum (Aau) interval biozone Age: Thanetian (pars), late Paleocene (pars). Samples:
LUl0-LU15.
Lithostratigraphy: Lambeth Group; Woolwich Formation (Woolwich Beds, pars). Commentst Apectodinium parvum
is
present at
Sample:LUl9.
Lithostratigraphy: Thames Group; Harwich Formation (Oldhaven Member). Comments'. The highest sample at Lower Upnor (LU19) contains a highly impoverished assemblage which precludes assignment of it to any biozonal llnit; Leiosphaeridia spp. and, Pterospermella spp. are present.
t69
PALEOCENE_EOCENE DINOFLAGELLATE SEQUENCE BIOSTRATIGRAPHY
Wratrness dinoflagellate cyst
through the utilization
biostratigraphy
record. Previous studies of these sections have been corelatable on a broad scale throughout northwest Europe (see, for example, Costa & Downie 1976; Costa et al. 1978; Heilmann-Clausen 1985) and the
Glaphyrocysta ordinata ( Gor) inte rttal biozone ,4ge: Ypresian (pars). early Eocene (pars). Samples'.
WBI-WB10.
Lithostratigraphy: Thames Group; Harwich Formation (Wrabness Member, pars). Comments'. The assemblage in sample WB1 at the base of the succession examined (50 cm above the Harwich Stone Band) contains common Deflandrea oebisfeldensis and Glaphyrocysta
ordinata (thus indicating assignment of the D. oebisfeldensls acme of Knox & Harland 1979). AIso common in WB1 is Hystrichosphaeridium tubiferum. Other events
of note within the Gor biozone include: the FOs of Fibrocysta bipolaris and Lentinia? wetzelii at WB1; the FOs of Achilleodinium bifurmoides
and,
Deflandrea phosphoritica
at WB2 (together with Diphyes colligerum, Phthanoperidinium crenulatum and Melita-
sphaeridium pseudorecur-vatum)i and the FO of Palaeotetradinium minusculum at'V,lB6. Phelodinium magnificum, the index taxon for the Gor biozone has its LO at WB7. Apectodinium
homomorphum, Deflandrea oebisfeldensis,
Glaphyrocy sta ordinata and Hy stricho sphae ridium tubifurum have their LOs at WB 10. The Leiosphaeridiabiofacies of Bujak & Mudge (1994) was not encountered in our sample set from Wrabness. However, the data of Jolley & Spinner
(1989,
fig. 3)
indicates that Deflandrea oebis-
feldensis occurs at levels < TVobelow the Harwich Stone Band, which suggests that the succession below the Stone Band could be assigned to the Leiosphaeridia biofacies, albeit on negative evidence.
cyst
North Sea Basin (see, for example, Costa & Manum 1988; Powell 1988, 1992b). However, the present study makes it possible for finer-scale correlations to be made with the North Sea Basin where similarly detailed (and largely unpublished) analyses have been carried out since the early 1980s (e.g. Stewart 1987; Powell 1988; Wills & Peattie 1990; Mudge & Bujak 1996). Correlations into northwest Europe, however, remain broad because detailed biostratigraphic data either require reappraisal (having being published prior to 1980) or are unavailable through lack of study. A number of hiatuses are apparent in onshore southeast England, as might be expected in a more proximal setting. Where a hiatus is contained within a particular biozone, sedimentological and lithological characteristics have been taken into consideration. The hiatuses are manifest as a series of eight transgressive-on-highstand systems tract unconformities (type 1 sequence boundaries) marking the bases of five Thanetian sequences and two Ypresian sequences. A third Ypresian sequence has its base marked by a shelf margin systems ffact (type 2 sequence boundary).
North Sea sequences Correlation between the onshore (proximal) sequences of the present study and their offshore (distal) equivalents is dependent upon the recognition of linking bioevents. Recent developments
in
North Sea lower Paleogene biostratigraphy
& Copestake 1992; M:odge & Bujak 1996) suggest that particular bioevents (often acme
(e.g. Mudge
occurrences) are associated with high-gamma shales. The nature of high-gamma shales is not
Imp ov eris hed interzone
Age: Indeterminate. Samples'.
of the dinoflagellate
WB11-W815.
Lithostratigraphy; Thames Group; Harwich Formation, Wrabness Member (pars). Comments; The samples between WB11 and WB15 contain impoverished microplankton assemblages
including low levels of Leiosphaeridia spp., acanthomorph acritarchs, Pediastrum spp., Pterospermella spp., Tasmanites spp. and P arale c anie
lla
inde nt at a.
Sequence biostratigraphy The biostratigraphic analysis of the sections has demonstrated that a refined breakdown is possible
always apparent; some represent
condensed
sections associated with downlap surfaces. As noted by Powell (1992a), the amount of time represented within a particular condensed section will increase progressively in an offshore direction. As a result, condensed sections cannot be regarded
to represent true time iines. Condensed
sections
are not only characteristic of maximum flooding surfaces (primary condensed section of Powell 1992a), but also develop at the base of lowstand and shelf margin wedges (secondary condensed section of Powell 7992a). Care must therefore be taken when interpreting the correlative significance of high-gamma shales. Nevertheless, many sequences developed for the lower Paleogene of the North Sea (e.g. Jones & Milton 1994; Mudge & Bujak 1996) are based upon the recognition and
A. J. POWELL T7A'.
110
correlation
of
condensed sections. Because
a
number of bioevents recognized in our study are also present in the North Sea (Fig. 14), the dinocyst record provides an excellent means of relating the proximal and distal expressions of sequences.
D
inofla g ellat e
re
lativ e
s e
cy st p alae o
a- lev el
ec
o lo
obscures temperature-related signals significantly, since the onshore-offshore and facies-related
gy and
fluctuations
Studies of Recent dinoflagellate cyst distribution pa{.terns indicate that water-mass composition (roughly comparable to distance from shore), seasurface temperature, salinity and productivity are the principal controlling parameters. An actualistic approach would thus suggest that a similar situation
existed in the past. On this basis, it has been possible to interpret the late Paleocene to early Eocene reiative sea level and climatic history of southeast England.
Lithological, sedimentological and biostratigraphic data indicate that the sections investigated
represent marginal marine environments. Such considerations are supported by the absence of oceanic dinoflagellate cysts like Impagidinium and Nematosphaeropsls spp. One would expect that relative sea-level fluctuations in such a marginal
marine setting would be reflected
in
various, less reliable, sources, including information about other fossil organisms. Changes in average water temperature may be traced by comparing the relative contribution of typical high, middle and lower latitude dinoflagellate cysts to successive assemblages. However, the generally marginal marine nature of the investigated deposits
varying
abundances of taxa that typically occur in restricted marine or inner neritic water masses as opposed to
those that characteristically occur in outer-neritic waters. Moreover, it might be anticipated that only the transgressive and highstand phases would be present at the margins, while the lowstand deposits are only well developed in the basin, i.e. the North
Sea. In a manner similar to that applied by Brinkhuis (1994), the successive shifts in disffibution of the principal dinoflagellate cyst groups may be used to reconstruct the late Paleocene to early Eocene relative sea-level history of southeast England. The distribution of co-occurring aquatic palynomorphs may be used to further support interpretations. As a result of the scale of the present investigation, only second- and third-order sequences, sensuHaqet al. (1987), may be identified. Because the third-order signal is superimposed upon the second-order, high energy conditions become progressively more open marine through each second-order cycle. The recognition of higher order sequences would require even more closely-spaced samples.
The palaeoecological affinity of the dinoflagellate cyst groups may be established on the basis of published Recent distribution patterns available for those components of the assemblages
that have modern counterparts (or that are morphologically comparable to extant taxa). The palaeoecology of extinct taxa may be interpreted from
trends are dominant. Moreover, most species occurring in the sections are cosmopolitan in nature. The principal dinoflagellate cyst complexes
(Evitt 1985) and the significance of the
other
aquatic palynomorphs are summarized below.
Deflandrea Complex
of Pp-cysts. The
motile
dinoflagellate stages that produced cysts assignable to Cerodinium may well represent heterotrophic peridinioids. High frequencies of heterotrophic peridinioids are characteristic of areas with high primary production related to increased nutrient availability in upwelling areas and river mouths
(see Powell et al. 1992). Raised quantities of Cerodinium spp. may therefore, like Deflandrea spp. (Brinkhuis et al. 1992), be tentatively linked to such depositional settings; their motile stages may have grazed on diatoms and other phytoplankton (including other dinoflagellates) as well as on
bacterially decayed material.
Lejeunecysta, Palaeocystodinium and Phelodinium are included in this complex, as well as Cerodinium and Deflandrea. The factors controlling the distribution of Deflandrea oebisfeldensis were probably similar to those acting upon Cerodinium spp.
Apectodinium Complex of Pq-cy sts. Apectodinium spp. may be compared with other peridinioids, such as Cerodinium spp., and may have a similar palaeoecology. When present, Apectodinium spp. often dominate assemblages completely. This phenomenon suggests that the motile stages producing Apectodinium spp. were highly tolerant towards varying water-mass conditions and could be successful where others failed, e.g. in highly restricted marine settings. Furthermore, there is evidence to suggest (Jan du Ch€ne et al. 1975; Heilmann-Clausen 1985) that Apectodinium spp. appeared earlier
in the Tethyan Realm than in
the
North Sea Basin, or were more consistently present in the older Paleocene (Selandian) at lower latitudes (Brinkhuis et al. 1994). During the latest early Paleocene, theyappear to have migrated into higher latitudes (they would have migrated into higher latitudes initially in a pulsating manner associated with relative sea-level highstands and relatively high temperatures), including the North Sea Basin (Thomas 1993), and reached high abundances as far north as the Barents Sea by
PALEOCENE-EOCENE DINOFLAGELLATE SEQUENCE BIOSTRATIGRAPHY
the latest Paleocene (Brinkhuis, pers.
obs.).
Information from Thomas (1993) indicates that 'middle' Paleocene Apectodinium occurences are typically present at or near condensed intervals immediately above sediments representative of short periods of sand-prone, high terrestrial flux. During the late Paleocene they became increasingly common, culminating in worldwide, nearly monotypic, assemblages at the Paleocene*Eocene boundary (Powell 1988). The present study shows that Apectodinium spp. gradually disappeared through the course of the early Eocene, at least in the basin margins, to be replaced by the Wetzeliella lineage.
M is c e llane ous al gae. Althotgh published records Tasmanites spp., Pterospermella spp. and Cyclopsiella spp. show them to have cosmopolitan distributions extending from freshwater to oceanic
of
settings,
high relative
abundances almost
exclusively occur in quite nearshore, inner-neritic
to brackish settings (Chateauneuf
Representatives
of the Glaphyrocysta group, most
of which are included within the
Areoligera
Complex. may represent open marine. inner-neritic water masses (Downie et al. l91l; May 1980; Brinkhuis & Zachariasse 1988: Brinkhuis et al. 1992; Brinkhuis 1994).
Homotryblium Complex of Gq-cysts. Represenof the Homotryblium Complex, include Polysphaeridiura as well as Homotryblium itself,
tatives
are regarded to represent restricted marine to inner Wall 1984; Brinkhuis 1994).
neritic water masses (Bradford
&
Spiniferites Complex of Gs-cysts. This complex, which includes Achomosphaera, Hystrichostrogylon, Rottnestia arrd Spiniferites, is regarded to represent open marine, neritic water masses (Wall et al. 1977l, Head & Wrenn 1992; Brinkhuis 1994).
Cordosphaeriditm Complex of Gi-cysts. This complex, only represented by Cordosphaeridium in the present study, is regarded to represent open marine, neritic water masses (Downie et al.
1971;May 1980; Brinkhuis 1994).
Operculodinium Complex
of Gn-cysts.
The
Operculodiniun Complex, which includes Dapsili-
dinium, Diphyes and Lingulodinium
and
Operculodiniunr is thought to represent restricted to open marine, neritic water masses (Wall et al. 1977).
1980).
Pediastrum spp. have a definite fresh- to brackishwater origin.
Acanthomorph acritarchs. Published records of these taxa show them to have cosmopolitan distri-
butions from freshwater to oceanic. Highest relative abundances almost exclusively occur in relatively nearshore, inner-neritic
Areoligera Complex of Gv-cysts. This complex, which includes Gerdiocysta as well as Areoligera, is thought to represent marginal marine, innerneritic settings, often in association with relatively coarse-grained deposits (hydrodynamicalty high energy), indicating a tolerance for such settings (Downie et al. 1971; Brinkhuis 1994). However, one species, Areoligera gippingensis, is indicative of offshore conditions (Heilmann-Clausen 1994).
111
to
brackish
settings.
Foraminiferal test linings. Remains of the inner walls of foraminifera have been suggested to be derived from benthic foraminifera in relatively inshore habitats at the change-over from normal to restricted marine settings (G. J. Van de Zwaan, pers. comm.). They are also known to occur in areas of upwelling (Powell et al. 1992). Leiosphaeridia spp. This category, often referred to as leiospheres, probably represents a heterogeneous group of freshwater to marine organisms. However, they often dominate in sediments independently characterized as brackish or freshwater environments. They are often accompanied by Pterospermella spp. which may support attribution to restricted marine to freshwater environments. Bujak & Mudge (1994) refened to this assemblage as the Leiosphaeidia biofacies of late Paleocene to early Eocene age in the North Sea Basin.
Paralecaniella spp. Although Paralecaniella spp. have been reported from Upper Cretaceous and Teftiary successions from around the world, their palaeoenvironmental significance is poorly understood. Elsik (1977) considered them to represent
either schizosporous algae or acritarchs, and mentioned that they were most abundant in marginal marine successions, indicating a tolerance for inner-neritic, probably brackish, conditions.
Dinoflagellate cyst sequence biostratigraphy of the studied sections By using the above listed palaeoecological characteristics of the principal dinoflagellate cysr groups and the other accompanying aquatic palynomorphs, five Thanetian and three Ypresian sequences have been identified in the studied sections. Figure 16 shows a summarized sequence stratigraphy of
studied sections, while the predicted sequence
A. J. PO\IELL ET AL.
112 LITHOSTRAT. CHRONO. BrozoNEs (Powell '92) (Ellison et al. 1994 STRAT.
SEQUENCES SEOUENCES Pagwell Bay Herne Bay
Was
SEOUENCES Lower Upnor
SEQUENCES WrabnBSs
SEQUENCES lHardenbol'94)
HST Ypr-t TST
uJ
z O z o UJ a
:,':
I.JJ
cc LU
ul
E
L
Gor
o = J
SMSI
Yp-2
HST
sffi
Ypr-2 TST Ypr-2
LST (ivt)
(pr-2 LST (ivl)
vl-1
HST Ypr-1
TST
Th-6 HST
l3 Aau
Thr-5
3lE ,!l: 5l.c
TST
SI: clo
-5
ro
l=
HST
HST
Thr-4
Beds'
Th-5
Thr-4
TST
TST
ul
z
LU
O
z
o [! tr UJ J
oE.
tu o_ o_
:)
z T F
Th-4
Ahv HST Tht-3 HST Thr-3 TST
X
Th-3 HST Thr-2 TST
Ama
u
E
Th-2
HST
Thr-'l
TST
Th-1
Fig. 16. Summarized sequence stratigraphy of studied sections.
PALEOCENE_EOCENE DINOFLAGELLATE SEQT]ENCE SEOUENCES This Study
Predicled stratig raph ical extent of condensed sections
ffi I
4
Biozonation
co
I (Balder)
.e (/) q)
LITHOSTRAT )entral Graben (K&H 1992)
E
82
o
LL
T50
q)
(!
dl
B1
o
E (!
S3
i
\ ffi rdcw
k €;ffi @
.e
ltt
Cromarty Sandst,
$
Memb€r
a q)
*
cromarty
I'13
c
,#
Ypr-1
SEQUENCES SEQUENCES Slewart ( 1 987) Jons & M&B (this vol) Milton (1994)
.9 (!
Shell Margin We(
Ypr-Z
Forties Field UniE
w&P (199o)
3rd Order
lprimary
Ypr-3
Forties Fi6ld
w&P (1990)
BIOSTRATIGRAPHY
()
M
8 (Dornoch
T45
Q2h
Sandstone .6.
Member ,ffi.
lr^ffi Tht-5
r€W Fonies
c
Deflandrea darlmooila
Znd O-iderFTimary
o .E E
o LL o s1b o
N
Sandslone /
Bt
5
Member ,&
J
a
(= 4
f,
3rd Order ffi^4 Primary CD
xW
Tht-4
v+
\
Forties Sandston Msmber
E f
tco
o o o
o
,gVi,
a)
Primary CD
ffi
H
7
f,
Memb6r
Tht-3
G a_
N
Forties Sandston
A \Gll
i
O)
S2a
(6
L
a.
q
6E o6f,
t=&S
(Forties)
F
51a
T40 E
,,4
\TAfr I AriN
'sx
Tht-2
Upper BalmorE Sandslone
3rd Order Primary CD
'ts
ffi
tE (/)
Yqffi Lower
o
(U
5
.a
,ffi
E LL
o
lalmorat A
(Lista ll) Andrew Tufl
o.
pyrophorum
L3
(U
D
\ ()'
2nAErrierF?f mZE Condensed Section
.9
Lista lll)
N
t
Tht-1
6
$
et
C
Fig. 17. Summarized sequence stratigraphy ofNorth Sea Central Graben
3 (Lista l)
.u)
J
T30
L2
A.
111
r_ POWELL
strati-graph)' of North Sca Central Graben is sho'"vn
in I;i-s. 17.
'[hartetian Secluence
I
pars
1.
Mugnetostrcrtigroplt: Chron 26n to 2-5r (pars.) in Knor er al. (1t)91). I-ithostrtLti,qrapftr': Thanet Sand Formation (BaseBecl. Stourtnouth C lay's, Pegr','el I N{arl s). Btts,:tl unt'on.fiu'rlllr': The Base-Bed of the Thanct Sand Formation lies unconformablv upon the Chalk
Group rrn,ith the Campanian Maastrichtian, the whole ol thc Lower Paleocene (biozones Cco. Tru. Xlu. Scr and Cst of Pou'cll 19920) irnd n'ruch of the Uppcr Paleocene (biozones Scle, Csp and Ppv ol Prrucll l9Ql/rt .ttcucr:iurt. nlis:irtg. Recog,nistl .r1s1.r?.t rtrcts: TST. PB3 PB I-5: HST,
PBI6 PB2I. (lonnrcnr.s. Areoligera spp. cxhibit a strong dominance in the assernblages betrveen PB3 and PB15 (superabundant). br-rt shou' a stcacll' decline above
PBl6 PBlg
(abunelant).
fore interprcted as a
The m.f.s. of the Tht-l sequence is represented by a second-order primary condensed section (Fig. 17) at the 5-6 sequence boundary of Stewart boundary of Mudge
& Bujak
(1996). The Tht-l
sequence corresponds to the Th-l sequence of Hardenbol (1994) and also equates with sequence BTI ol Knox er al. \1994).
Thanetian Sequence 2 (Tht-2) Samples'. PB22 PB28 (Pegwell Bay). Biozonation'. Alisocy sta margarita (Ama) biozone (pars).
Magnetostratigraphy: Chron 25r (pars) in Knox et al. (1994). Lithostratigraphy'. Thanet Sand Formation (Reculver Silts, pars).
Basal unconformity: The Reculver Silts lies unconformably upon the Pegwell Marls with part of the succession attributable to the Ama biozone missing.
This succession is therc-
Recognized systems tracts'. TST, PB22-PB24; HST'
stricted high-encrg.vof a transgressive
PB25_PB28. Comments'. The Spiniferites Complex, being the most 'offshore' dinoflagellate cyst group present in the assemblages, exhibits a sffong dominance in the
re
mar-cinal manne setttng typical
regime. Sanrples PB1-l and PB15 ale b1' fal the richest samples of the sttccession in terms of concentration and are thought to lic close to the
ot
maxilnurr floodin-s sr-rrface (r-n.f.s.). Conspicuously. Areoligeru tippin-
rnost conclenseLl interval
grnsrs has its peak occurrence in thesc sar-nplesl this species may' represent a n-rolphotype of Arertligertr adapted to rlrore offshole conclitions (HeilmannClausen 199.1). The dccline in the rclatrve percenta-ue of Arcitligeru spp. abore sanrple PBI-5 is accom-
panied
.,11-.
(1987), the T30-T40 sequence boundary of Jones & Milton (1994) and the Lista II-Lista III sequence
(Tht-1)
Suntples: PB3-PB2I (Peglcll Bay1. Bio:orrtLtion'. A1i.rr.,r'r'slr.t rnorgurito (AIra) biozone (
t7
by an increase in the recoverv of
the
in samples PB22-PB24, but declines steadily above. This succession is interpreted to represent open marine, neritic conditions marking assemblages
the onset and development of a transgressive phase. The '6 inch' shell bed (unit 15) at the base of the Reculver Silts is thought to mark the transgressive surface (TS) overlying the highstand deposits of the underlying Tht.l sequence. Samples PB25 and PB26 are the richest samples in this sequence (in terms of concentration) and are thought to lie close
Spini.l'erircs Complex as u'e11 as
to the most condensed interval or m.f.s. The
caused the si-*nificant seditnent accr.rr-tlulation of thc
Spinferites Complex above PB25 is accompanied by a marked relative increase in rhe Glaphyrocystrt group, reflecting increased influence of innerneritic water masses. This part of the sequence is therefore interpreted to represent the introduction of gradually more restricted, inner neritic conditions in response to a subsequent relative sea-1evel highstand (HST). The LO of Alisocysta margarita (PB26) seems to be associated with the relative sea level fall of the Tht-2 sequence and may be used to correlate the m.f.s. into other
the introductiotl ctl Cortlo.splureridiunt spp. ln addition. relative nurnbers of the Glalthr'l?('r',!/rr gloLlp start to increase in this interval. This suecession is intclpreted to represcnt the introduction of hydloclvnan-ricalll' less energetic. neritic, open marine conditions in rcspt'rnse to a relatile sea-lcvel high stand. A possible Lrnderlying second-orclcr trend ol lclatir.e sca levei rise throu-uh suhsidence rnal hare r.nain bodl'
of the Pesrvell N{arls durrng this HST
phase.
Etluit'tilt'nt'e'. Thc 1o$'stancl svstems tlact (LST) ol sequence Tht-l is absent. Holr'ever. in the central Nt,tth Sclt tlri\ prll rrl lllc \LlC!e\\itrn tnl) trrrrcspond to the Loucr Balmoral Sandstone riithin the Lista Formation (Ll) (on tlre basis that it lics above the LO of PtLlaeoperit)iniurn pt'trtpltonuir according
to Knox & Holloua) 1992).
discontinuous nodule layer (unit 17) between these two samples is considered to represent this horizon. The decline in relative percentages of the
sections. Equivalence'. The missing succession at the base
of the Tht-2
sequence represents the LST. This
probably corresponds
to the Upper Balmoral
PALEOCENE EOCENE DINOFL.{GELr_.ATE SEQUE}rCrL BrOS.l.R.,\TICiRApHy Sandstone
within the Lista Formation (L3) in the
central Nofih Sea (on the basis that it lies below the LO of A/isocysta margarita according to Knox
& Holloway
1992).
The m.f.s. of the Thr2 sequence is represented by a third-order primary condensed section (Fig. 17) within sequence 6 of Stewart (1987), sequence T40 of Jones & Milton (1994) and the Lista III sequence of Mudge & Bujak (1996). The Tht-2
sequence corresponds to the Th-2 sequence of Hardenbol (1994) and also equates with sequence
BT2 of Knox er al. 119941
seclirnents $
ith
hr_rrh
115
levcls of contincntallr'-derivcd
pllnl nlulctiillr. Thc lri::hert.lrrrrple tlkcn lrorp 16. Reculver Silts. sarrple HB I l. unexpcctedl\, contains high lelative nurnbers ol' the ofIshor.e Spirtif'erites Conrpler. It is possible that these rnar, have been intloduced florn thc or.erll,ing Beltin_te Fish Bed (unit J) of the Upnor Fornrarion throuslr burrorvin-u. An altcrnativc explanation rnay be sanrpline error as thc sarnples rvcre collccted fl.onr the covered succession in the intcrtidal zone ofthe tbreshore.
Etprirulence.
It
ntust be consiclcred likell. that no of the l'ht-3 seqLrcnce was devclopecl at the basin rrarginsl in the ccntral Nor.th Sea the equir.,alent lowstand cleposit.s probabll, Jie
lowstand phase
Thanetian Sequence 3 (Tht-3) HBl-HB11 (Herne Bay). B iozonation: Ap e ct odinium hy pe rac anthum (Ahy ) biozone (pars). Magnetostratigraphy: Chron 25r (pars) in Knor et al. (1994). Samples:
Lithostratigraphy:
Thanet Sand Formation
(Reculver Silts, pars).
Basal unconformity: Becatse there is no overlap between the sections at Pegwell and Herne Bays, the presence or absence ol an unconlormity between samples PB28 and HB1 cannot be proven. The argument for the presence of a sequence boundary between the sections is based upon the composition of the dinoflagellate cyst assemblages (discussed below). Recognized systems tracts'. TST,
HBl-HB4;
HST,
HB5-H811. Comments: The whole aspect of the assemblages from the lower part of the Herne Bay section (notably the presence of Apectodiniun spp.) are markedly different to those from the upper part of the section at Pegwell Bay and suppofis the view that a discontinuity is present between the sections. The Spiniferites Complex exhibits a strong dominance in the assemblages in samples HB 1-HB2 and HB3, but has lowered relative percentages in overlying samples, until sample HB11. The lower part of the Herne Bay succession is therefore interpreted to represent open marine conditions marking the onset and development of a transgressive phase (and an underlying TS is therefore predicted). Sample HB4, taken at the 'Reculver Tabular Band, (unit B), conspicuously displays a marked increase in the Glaphyrocysta group, reflecting increased influence of inner-neritic water masses. The Reculver Tabular Band is therefore thought to represent the condensed interval or m.f.s. The succession overlying the Reculver Tabular Band is therefore interpreted to represent the introduction
of
more restricted inner-neritic conditions in
response to a subsequent relative sea-level HST. This culminates higher up in the renewed introduction of increased relative percentages of the
even more restricted Areoligera spp. (iound in
u'ithin the (lou,cr) Forties Sandstone N,Iember rvithin the Sele Formation (Sla) (on the basis that thev lie above the LO of A1l.sr.,r't.rttt rnurguritu accorclins to Knox & Holloway 1992). The nt.f.s. of the Tht-3 seqllence is represente.l bv a third-orcler pnntarl, conclensed section (Fig. 1 71 within sequence 7 of Stcw,art (19871. sequence T40 of Joncs & I,lilton (199.1) ancl the Forties sequence of N,lLrdsc & Bujak (1996). The Thr-3
scquence corresponcls to the Th-3 scquence ol Hardenbol i | 99.11 ancl possibl), equates to sequence
BT3 of Knor er al. (1991). Thtutetittn Secluente I f 7ltt-|) Sample"-: HBl2 HB15 lHerne Bay)l LU3-LU9 (Lower Upnor). Bio
