Journal
of
Foraminiferal Research,
v.
35,
no.
4,
p.
279-298, October 2005
A REVISED
TROPICAL
TO
SUBTROPICAL
PALEOGENE
PLANKTONIC
FORAMINIFERAL
ZONATION
WILLIAM
A.
BERGGREN
i
,2 AND
PAUL
N.
PEARSON
3
ABSTRACT
New
biostratigraphic
investigations
on
deep
sea
cores
and
outcrop
sections have revealed several shortcomings
in
currently
used
tropical
to
subtropical
Eocene
plank-
tonic foraminiferal zonal schemes
in
the
form
of: 1) mod-
ified taxonomic concepts, 2) modifiel:l/different
ranges
of
taxa,
and
3)
improved
calibrations with magnetostratig-
raphy.
This new
information
provides
us
with
an
op-
portunity
to
make
some necessary
improvements
to
ex-
isting Eocene
biostratigraphic
schemes.
At
the
same
time, we provide
an
alphanumeric
notation
for
Paleo-
gene zones using
the
prefix
'P'
(for Paleocene),
'E'
(for
Eocene)
and
'0'
(for Oligocene)
to
achieve consistency
with
recent
short-hand
notation
for
other
Cenozoic zones
(Miocene
['M'],
Pliocene [PL]
and
Pleistocene [PTD.
Sixteen
Eocene (E) zones
are
introduced
(or
nomen-
claturally
emended) to replace
the
13 zones
and
subzones
of
Berggren
and
others
(1995). This new zonation serves
as a
template
for
the
taxonomic
and
phylogenetic studies
in
the forthcoming Atlas
of
Eocene Planktonic Forami-
nifera (Pearson
and
others,
in
press).
The
10 zones
and
subzones
of
the
Paleocene (Berggren
and
others, 1995)
are
retained
and
renamed
and/or
emended
to
reflect im-
proved
taxonomy
and
an
updated
chronologic calibra-
tion
to
the
Global
Polarity
Time
Scale (GPTS) (Berggren
and
others,
2000).'
The
PaleocenelEocene
boundary
is
correlated
with
the
lowest
occurrence
(LO)
of
Acarinina
sibaiyaensis
(base
of
Zone
El),
at
the
top
of
the
trun-
cated
and
redefined (former)
Zone
P5.
The
five-fold zonation
of
the
Oligocene (Berggren
and
others, 1995) is modified
to
a six-fold zonation with
the
elevation
of
(former) Subzones
P21a
and
P21b to zonal
status.
The
Oligocene
(0)
zomil'
components
are
re-
named
and/or
nomenclaturally
emended.
INTRODUCTION
The application
of
planktonic foraminiferal biostrati-
graphic studies may
be/said to be an essentially post-World
War II phenomenon (although there were several pre-war
contributions
of
less than lasting value) which resulted from
the recognition
of
their usefulness in local and regional bio-
stratigraphic zonation and correlation. These studies were
often, but not exclusively, connected with petroleum explo-
ration, particularly in the North Caucasus, Crimea, Tadzhik
Depression and other areas
of
the southwestern (former) So-
viet Union (Subbotina, 1947, 1953; Morozova, 1939, 1961;
1 Department
of
Geology and Geophysics, Woods Hole Oceano-
graphic Institute, Woods Hole, MA, 02543,
U.S.A..
. .
2 Department
of
Geological Sciences, Rutgers Umverslty, PIscata-
way, NJ 08854, U.S.A. E-mail: wberggren@whoi.edu
3 School
of
Earth, Ocean and Planetary Sciences, Cardiff University,
Main Building,
Park Place, Cardiff CFlO 3YE, United Kingdom.
279
Alimarina, 1962, 1963; Leonov and Alimariria, 1961; Shuts-
kaya, 1956, 1958, 1960a, b, 1970; Shutskaya and others,
1965). A largely independent zonal scheme was developed
in the Caribbean region (Bronniman, 1952; Bolli, 1957a, b;
1966), and was subsequently applied to the United States
Gulf Coast and Atlantic Coastal
Plain (Loeblich and Tappan,
1957) and expanded in various petroleum exploration re-
gions
of
the world (Blow and Banner, 1962; Blow, 1969,
1979; Stainforth and others, 1975). Various biostratigraphic
zonal schemes were developed by these authors, among oth-
ers, and have been firmly ensconced in the classic biostrati-
graphic literature
of
the past half century.
Since the advent
of
the Deep Sea Drilling Project (DSDP;
1968-1984) and its successor programs, the Ocean Drilling
Program (ODP) and Integrated. Ocean Drilling Program
(IODP),
these various zonal schemes have found widespread
application
in
regional and global biostratigraphic studies.
In the following section, we supplement recent reviews
of
Paleocene zonations
of
the West by presenting a brief re-
view
of
the major Paleogene biostratigraphic studies and
zonal schemes developed over the past
50 years in the For-
mer Soviet Union (FSU) and the West, with a particular
focus on the Eocene.
It
should be remembered that many
of
these studies were conducted as part
of
a larger study
of
the Paleogene
or,
indeed, the entire Cenozoic, so that ref-
erence to the larger framework is unavoidable
in
certain
instances.
Following this overview, we introduce a revised low-lat-
itude (tropical and SUbtropical)
Paleogene planktonic fora-
miniferal zonation. There are several reasons (discussed be-
low) why a revised zonation has become necessary at this
time. These reasons arise variously from taxonomic devel-
opments, new stratigraphic information or perceived short-
comings in previous schemes. The new zonation is intended
to accompany the publication
of
a new Atlas
of
Eocene
Planktonic Foraminifera
(Pearson and others,
in
press)
which uses the zonation outlined here as its biostratigraphic
basis. Most
of
the updates presented here refer to the Eo-
cene, but the
Paleocene and Oligocene zones are also treated
for sake
of
completeness and numerical continuity.
REVIEW
OF EOCENE PLANKTONIC
FORAMINIFERAL ZONATIONS
A history
of
Paleogene planktonic foraminiferal zonations
in the Former Soviet Union (FSU) was presented by Berg-
gren (1960), and an llpdated review
of
Paleocene zonations
of
the FSU was presented by Berggren and Norris (1997).
Comparable reviews
of
Paleogene' zonations
of
the Carib-
bean and Mediterranean may be found in Bolli and others
(1985). These need not be repeated here. Inasmuch as the
emphasis in this paper is on a revised zonation for the low-
latitude (tropical and subtropical) Eocene, we present below
a more extensive review
of
that interval as expressed in the
FSU and Middle East.
280
BERGGREN AND PEARSON
THE
FORMER
SOVIET
UNION
AND
MIDDLE
EAST
Biostratigraphic studies
of
planktonic foraminifera in gen-
eral (and
of
Eocene assemblages in particular) may be said
to have originated in the
FSU. In careers that spanned more
than
50 years, Martin Glaessner (Moscow) and Nina Ni-
kolaevna Subbotina (LeningradlSt. Petersburg) became the
"patron saints". Subbotina died in the early 1980s; the Aus-
trian-born Glaessner left Moscow for Vienna during the in-
famous Stalin trials in 1937, subsequently relocating (1938)
to pursue a career in Australia. He died in 1989; see
Gruz-
man and others (1986) and McGowan (1994), respectively,
for moving tributes to these two pioneering micropaleon-
tologists. In the mid-late 1930's both authors published
sem-
inal papers on the biostratigraphy
of
the Caucasus Moun-
tains (Glaessner, 1934, 1937a, b; Subbotina, 1934, 1936,
1939; see also Morozova, 1939), which basically established
the use
of
planktonic foraminifera in regional biostratigraph-
ic studies. Subbotina was able to establish several zones for
the Paleogene (and, in particular, the Eocene)
of
the northern
Caucasus; in 1947 she expanded her studies into the north-
eastern Caucasus and, subsequently, published her now fa-
mous synoptic monograph (Subbotina, 1953) on Upper Cre-
taceous and Paleogene planktonic foraminifera.
Important biostratigraphic studies/reviews concerning at
least part
of
the Eocene were subsequently published by
Alimarina (1962, 1963), Leonov and Alimarina (1964),
Shutskaya (1956, 1958, 1960a, b, 1970), and Shutskaya and
others (1965). The study by Shutskaya (1970) is notable in
that it presents a synthesis
of
her decade-long studies in the
southwest
FSU, including a review
of
the detailed zonation
of
the Paleocene-lower Eocene succession which she de-
veloped in the 1960s, and an exhaustive historical overview
of
the Paleogene biostratgraphic succession and faunal char-
acteristics
of
the Crimean Peninsula, northern Precaucasus
and Transcaspian region and western part
of
central Asia.
In the latter work (Shutskaya,
1970) she included 40 plates
with detailed illustrations
of
the assemblage content (plank-
tonic and benthic taxa)
of
each Paleocene and lower Eocene
zone from each region, which makes it possible to under-
stand better the basis for biostratigraphic subdivision
of
the
Paleogene
of
the FSU.
It
also permits her zonal scheme to
be correlated with those proposed contemporaneously, and
subsequently, in the West. Finally, Krasheninnikov (1965,
1969) made important contributions to Eocene biostratig-
raphy in the
FSU, as well as other (sub)tropical regions
of
the world (see below), including correlation
of
planktonic
and calcareous nannoplankton biostratigraphies in the North
Caucasus (Krasheninnikov and Muzylev, 1975).
A thorough review
of
early (early 1930's-late 1950's) So-
viet publications on Paleogene planktonic foraminiferal bio-
stratigraphic studies was published by Berggren (1960).
An
up-to-date review
of
Paleocene-lower Eocene zonal schemes
formulated by Shutskaya was presented by Berggren and
Norris (1997), and a correlation framework
of
Soviet and
western Paleogene (including the Eocene) zonal schemes
was published by Blow (1979).
Valery Krasheninnikov has devoted a significant effort to
presenting overviews and comparisons
of
planktonic fora-
miniferal zonal biostratigraphy on a global basis. These in-
clude Syria (Krasheninnikov, 1964a, b; Krasheninnikov and
others, 1964; Ponikarov and others, 1969; Krasheninnikov
and Nemkov, 1975), Armenia (Krasheninnikov and
Ptukh-
yan, 1973),
Egypt
(Krasheninnikov and Ponikarov,
1964),Yugoslavia (Krasheninnikov and others, 1968), the
North Pacific
Ocean (Krasheninnikov, 1982; Krasheninni-
kov and others, 1988), the Southern Oceans (Krashennikov
and Basov, 1986) and the (sub)tropical regions
of
the world
(Krasheninnikov, 1969), resulting in a synoptic overview
of
Paleogene global biostratigraphy (Bolli and Krasheninnikov
(1977). Among the pertinent observations relevant to this
study (Krasheninnikov, 1969; Bolli and Krasheninnikov,
1977) we can cite the following:
1)
There is a general, but systematic, change in taxic com-
position and a decrease in diversity among Eocene
planktonic foraminiferal faunas in a northerly direction
from the Mediterranean (Egypt and
Syria), through the
intermediately situated Armenia, to the Crimea-North
Caucasus region.
2) Some taxa appear to have had different stratigraphic
ranges in different (sub )provinces. The reasons for this
appear to be that ranges have been partly biofacies-con-
trolled (nummultiic versus open-ocean biofacies) and
partly latitudinally controlled.
3) Planktonic foraminiferal assemblages are essentially
similar in taxic composition throughout the Caucasus,
Armenia,
Syria and Egypt (allowing for facies changes
in given stratigraphic settings, such as the presence
of
nummulitic deposits in shallow-water environments),
with the following notable exceptions:
early Eocene: absence (or extreme rarity) in the north- .
em
Caucasus, Crimean regions
of
Astrorotalia palmerae
and Subbotina senni, and rarity
of
Acarinina aspensis;
middle Eocene: absence in the Crimea-Caucasus
of
such forms as Orbulinoides, Globigerinatheka, Globor-
otaloides, Clavigerinella, Planorotalites renzi (=P.
pseudoscitula),
"Morozovella"
spinulosa,
"M."
leh-
neri, Acarinina spinuloinjlata,
"Subbotina"
bolivari-
ana, Guembelitrioides higginsi
(=
G.
nuttalli
of
this pa-
per), Subbotina senni, Acarinina rohri, Hantkenina
mexicana,
H.
dumblei,
H.
alabamensis i.al.;
upper Eocene: absence or extreme rarity in the Cri-
mea-Caucasus
of
such forms as Hantkenina, Cribro-
hantkenina, Turborotalia ampliapertura, Catapsydrax
unicavus, Turborotalia cerroazulensis, Globigerinathe-
ka semiinvoluta, i.al.
4) Disjunct and sporadic occurrences/ranges
of
several taxa
are noted. For example, in the Mediterranean and Ar-
menian regions, Turborotalia cerroazulensis s.l. appears
in the Orbulinoides beckmanni
Zone and ranges to the
top
of
the Eocene, whereas it is representative only
of
the late/upper Eocene in the northern Caucasus. Globi-
gerinatheka index is a long-ranging form (G. kugleri
Zone to the top
of
the Eocene) in the Mediterranean-
Armenian area, whereas in the Crimea-Caucasus it has a
discontinuous range: it is rare in the Acarinina rotun-
dimaginata
Zone, abundant in the Hantkenina alaba-
mensis
Zone and absent in the
"Globigerina"
turcmen-
ica
Zone; it reappears in the lower and middle parts
of
the upper Eocene.
These disjunct
or
anomalous stratigraphic distribution
PALEOGENE PLANKTONIC FORAM ZONATION
281
patterns reflect the gradual growth
of
faunal provincialism
that followed the planktonic foraminiferal (and larger num-
mulitic) major extra-tropical Eocene excursions into high
latitudes. Excursions into northern (Berggren,
1970, 1971)
and southern (McGowran, 1977, 1978, 1986) latitudes oc-
curred during the early Eocene
"Climatic Optimum" (Zone
P6b-P7
of
Berggren and others, 1995, zonation) and, again,
in the late middle Eocene, during the so-called Khirthar
Transgression
of
the Indo-Pacific region, correlative with
Zones ElO-E13 as defined below. This transgression
brought warm biotic elements to
A\Jstralia (McGowran,
1977; McGowran and Li, 2000) and hantkeninids as far
north as
53° N (DSDP Site 647, sOlithern Labrador Sea;
observation by W AB based on samples from M. Kaminski,
1995).
Following the major climatic warming associated with the
first
of
these·
events and centered on Chrons C24r-C23n
(~
55-51
Ma) in particular, there was a gradual decline in
extra-tropical surface-water temperatures, which is reflected
in the gradual biogeographic compartmentalization
of
plank-
tonic foraminiferal assemblages. This has resulted in a need
for independent biostratigraphic zonal schemes to reflect the
changing distribution patterns. For instance, although typi-
cal (sub )tropical planktonic foraminiferal
taxa
occur
throughout the lower Eocene
of
the southern Indian Ocean,
keel~d
morozovellids were restricted to the E4-E5 (as de-
fined below) excursion (Kerguelen Plateau; Huber, 1991;
Berggren, 1992), and acarininids and subbotinids character-
ize the contemporaneous high-latitude, austral
South Atlan-
tic assemblages in the absence
of
keeled morozovellids
(Maud Rise;
Stott and Kennett, 1990; Huber, 1991; see pa-
per by Huber and
Quillevere, this volume). However,
by
the
middle Eocene, austral faunas were characterized
by
low-
diversity acarininid
(A.
collactea,
A.
primitiva), subbotinid
(S.
angip-;;foides,
S.
linaperta) and globigerinathekid (abun-
dant
G.
index) assemblages. The acarininids were replaced
in the late Eocene by catapsydracids
(c.
dissimilis,
C.
un-
icavus), Globorotaloides (the form referred to as "G. su-
teri"
by
most authors), subbotinids
(S.
angiporoides, S.
hagni-eocaena group) and small globigerinids
(G.
officin-
alis
group). These austral assemblages have their contem-
poraneous, taxically comparable counterparts in the upper
Eocene
of
the North Atlantic (Berggren, i972), the North
Sea (Berggren, 1970; King, 1981, 1989; Gradstein and oth-
ers, 1994) and northwestern Europe
(Sylvind Marl Formation
of
Denmark). /
THE
WEST
Eocene planktonic foraminiferal biostratigraphy in the
West was essentially initiated in the form
of
a detailed zo-
nation developed for the stratigraphic succession in Trinidad
by Bolli (1957a, b). His zonation was subsequently followed
by
zonal schemes developed for (sub)tropical regions in
general by Berggren (1969, 1971b), and modified and re-
defined by Berggren and Miller (1988), Berggren (in Berg-
gren and others, 1995) and Blow (1969, 1979).
Premoli Sil-
va and Bolli (1973) made minor changes to the earlier ver-
sion
of
Bolii (1957a) with the insertion
of
the Globorotalia
edgari
Zone between the Globorotalia velasco ens is Zone
(below) and the
Globorotalia rex
(=
G.
subbotinae) Zone
(above). Comprehensive reviews
of
Paleogene (sub)tropical
zonal biostratigraphy were given by Blow (1979) and Berg-
gren and Miller (1988), and particularly by Toumarkine and
Luterbacher (1985).
Jenkins (1971), as part
of
a larger Cenozoic study, for-
mulated a relatively broad biostratigraphic scheme for the
Eocene succession
of
New Zealand. With the recognition
that Paleocene low-latitude, (sub )tropical zonations are not
fully applicable at high latitudes,
Stott and Kennett (1990)
developed a zonal biostratigraphy for high austral latitudes
(Maud Rise) which also found application in the southern
Indian
Ocean (Kerguelen Plateau) in studies
by
Huber
(1991) and Berggren (1992). A modified zonation for the
Antarctic Paleogene is provided in a companion paper
by
Huber and Quillevere (this issue).
MAJOR
FAUNAL
TRENDS
A brief summary
of
the main biotic trends observed in
the planktonic foraminifera during the Eocene is presented
below
..
Aspects
of
these trends have been used by various
authors in the delineation
of
zonal schemes over the past 50
years.
1.
Conical morozovellids and robust acarininids reached
their highest diversity in the latest Paleocene and early
Eocene, respectively (Berggren, 1971b, Figure 1).
Sub-
sequent taxonomic studies (Berggren, 1977; Berggren
and Norris, 1997; Blow, 1979) have not changed this
picture significantly, with the exception
of
the morpho-
logic/taxonomic change noted below.
2.
The appearance during the late early to early middle
Eocene
of
a keeled lineage that is considered homeo-
morphic with Morozovella
(M.
bandy,
M.
crassata,
M.coronata,
M.
lehneri), which is being ascribed to a
new genus in the forthcoming
Atlas
of
Eocene Plank-
tonic Foraminifera (Pearson and Berggren, in press).
The middle Eocene is characterized by the sequential
flattening
of
tests
(M.
crassata/M. spinulosa and
M.
lehneri) and the extinction
of
this lineage near the mid-
dle/upper Eocene boundary. Also occurring
in
the early
middle Eocene was the disappearance
of
the true Mo-
rozovella
lineage (represented
by
M.
aragonensis)
within the lower middle Eocene (upper Lutetian Stage).
3.
Modification
of
the basic acarininid morphology
by
the
development
of
supplementary apertures in the majority
of
individuals in populations led in the middle Eocene
to the appearance
of
forms generally assigned to the
genus
Truncorotaloides in the midde Eocene and to
which the group is restricted.
In the Eocene Atlas (Pear-
son and others, in press) we retain these forms in the
genus
Acarinina, however.
4. The igorinid lineage, while never taxically diverse, un-
derwent a reduction in diversity during the early Eocene
and became extinct during the early middle Eocene.
Test form became more planoconvex and more weakly
muricate during the early Eocene than
in late Paleocene
antecedents, whereas the terminal member
of
the line-
age
(J.
anapetes) is characterized by up to nine cham-
bers
in
the final whorl and a more evolute test.
5. Planispirality returned as a morphogenetic novelty near
the PaleocenelEocene boundary with the evolution
of
282 BERGGREN AND PEARSON
Pseudohastigerina from Globanomalina, and, again,
with the independent origin
of
"Subbotina"
bolivari-
ana (a form assigned to a new genus in the Eocene
Atlas [Pearson and others, in press]) from Parasubbo-
tina near the early/middle Eocene boundary.
6.
In
the early Eocene, radially elongate chambers devel-
opedon a weakly spinose test (Parasubbotina eoclava),
followed by formation
of
clavate chambers bearing a
dense pore pattern within a wall having narrow cancel-
late ridges (Clavigerinella). Subsequently, there was a
reduction
of
the surficial cancellation and concomitant
acquisition in the middle Eocene
of
elongate, hollow
tubulospines at the midpoint
of
chamber extremities
and, later, during the latest
Eoce~e
at intercameral loci
(Hantkenina) and multiple apertures located on the ap-
ertural face (Cribrohantkenina).
7.
Globular· tests with multiple supplementary apertures
appeared in the middle Eocene (Guembelitrioides, Glo-
bigerinatheka, Orbulinoides) and extended to near the
end
of
the Eocene, where the disappearance
of
the glo-
bigerinathekid lineage (G. index,
G.
luterbacheri
and
G.
tropicalis) occurred.
8.
The turborotaliids, a long-ranging conservative group,
appeared during the late early Eocene with Turborotal-
ia frontosa through the modification
of
a globanomal-
inid
(Globanomalina
australiformis) morphology.
; However, the turborotaliids developed a distinct, and
biostratigraphic ally useful, morphologic trend during
the middle and late Eocene consisting
of
a gradual re-
duction in wall cancellation and test compression, lead-
ing to a smooth-walled carinate test
(T.
cunialensis)
during the terminal Eocene.
9.
Subbotinids continued to diversify during the Eocene,
particularly in austral latitudes where the
S.
linaperta
andS:
angiporoides plexi dominated.
10. Spinose and cancellate 'globigerinids' appeared in the
late Eocene (Globigerina officinalis and Globoturbor-
--otalita ouachitaensis groups, respectively) and gradu-
ally replaced the subbotinids during the Oligocene.
Their origin remains an enigma, although a relationship
with Subbotina appears logical.
11. The globoquadrinid (geometrically oriented honey-
comb) wall texture appeared in the
late middle Eocene
with the evolution
of
the nonspinose genus Dentoglo-
bigerina.
Documentation
and-an extended discussion
of
these mor-
phogenetic trends are presented in the Eocene Atlas
(Pear-
son and others, in press).
UPDATED PALEOGENE PLANKTONIC
FORAMINIFERAL ZONATION
We are acutely aware that stability
of
nomenclature is
highly desirable in biostratigraphy, and that alteration
or
modification
of
existing (and generally accepted and ap-
plied) zonal scheme(s) should not be undertaken lightly. For
the past
15
years, the Paleogene Planktonic Foraminifera
Working Group
(PPFWG) has been meeting under the aus-
pices
of
the International Subcommision on Paleogene Stra-
tigraphy (ISPS) with a view to publishing comprehensive
revisions to the taxonomy and biostratigraphy
of
Paleogene
taxa. A first volume, the Atlas
of
Paleocene Planktonic Fo-
raminifera has been published (Olsson and others, 1999).
An Eocene Atlas (Pearson and others, in press) represents
the second contribution in this series.
Unfortunately, the use
of
the acronym
'LO'
has been used
in the literature to denote two different types
of
datum level
(both 'lowest' and 'last' occurrence) and is thus subject to
confusion and misunderstanding unless their meaning is
clarified.
In
the discussion below, we differentiate between
the lowest
(LO) and highest (HO) occurrences
of
paleon-
tologic events used to define the limits
of
a biozone, and
the first appearance datum (FAD) and last appearance datum
(LAD)
of
paleontologic events used to define temporal lim-
its
of
a biochron (sensu Aubry, 1995; see discussion below).
In
the course
of
our investigations we have discovered,
or
been made aware of, several shortcomings in the zonal
scheme
of
Berggren and others (1995). The main areas for
improvement are as follows:
1.
It
is now well established that a discrete, temporally short
« 150 k.y.) stratigraphic interval exists at the base
of
the
Eocene (as now recognized;
Ouda and Aubry, 2003;
Gradstein and others, 2004, p. 87) that is characterized
in pelagic carbonates by geochemical evidence
of
rapid
climatic warming and a carbon isotope excursion (CIE;
Zachos and others, 1993). This interval, which is asso-
ciated with several distinct and stratigraphically limited
planktonic foraminiferal
"excursion taxa" that are
,of
great utility in identifying the PaleocenelEocene bound-
ary (Kelly and others, 1996, 1998), lies within the middle
part
of
Zone P5
of
Berggren and others (1995). We fol-
low the suggestion
of
Pardo and others (1999) and Mo-
lina and others (1999) in using the
LO
of
one
of
the
excursion taxa, Acarinina sibaiyaensis, to subdivide the
old Zone P5
of
Berggren and others (1995). We also use
the now well-documented
LO
of
Pseudohastigerina wil-
coxensis to further subdivide the old Zone P5.
2.
Several
of
the lower and middle Eocene zones listed in
Berggren and others (1995) need to be redefined to con-
form more rigorously with the
SUbtypes
of
Interval Zones
listed in the International Stratigraphic Guide (Salvador,
1994), which is used in this study as the convention for
zonal nomenclature.
3.
New information from drill cores in Tanzania (Pearson
and others, 2004) has indicated that the LO
of
Hantken-
ina in the early middle Eocene is probably diachronous,
with the first Hantkenina having a restricted geographic
range. A more easily recognized datum at a very similar
level is the
LO
of
Guembelitriodes nuttalli. Note that
Globigerinoides nuttalli Hamilton is now recognized as
a prior synonym
of
"Globigerinoides" higginsi Bolli
(Olsson and others, in press). The latter was a frequently
used name for this species. However, reasons for adopt-
ing this synonymy are that nuttalli was clearly described
and illustrated in a prominent publication, the name has
been used,
if
rarely, and new study
of
its holotype con-
firms its identity.
4. As part
of
this study we have recollected the
Eocene-
Oligocene stratotype section at Massignano, Italy at a 10-
cm
resolution in order to locate key upper Eocene bio-
stratigraphic datums with greater accuracy than has hith-
PALEOGENE PLANKTONIC FORAM ZONATION
283
TABLE
1.
Age estimates
of
planktonic foraminiferal datum levels in Massignano section, Italy based on study in this work on recollected sample
material.
Event Reference
LAD H. alabamensis
Berggren and others (1995)
(E/O GSSP)
Coccioni and others (1988)
Base
Zone
01
Gonzalvo and Molina (1992)
This study
LAD
T.
cerroazulensis
Berggren and others (1995)
Coccioni and others (1988)
Gonzalvo and Molina (1992)
This study
LAD
C.
inflata
Berggren and others (1995)
CoccionLand others (1988)
Gonzalv6 and Molina (1992)
This study
LAD
G.
index Berggren and others (1995)
Base
Zone
E16
Coccioni and others (1988)
Gonzalvo and Molina (1992)
This study
FAD
T.
cunialensis
Berggren and others (1995)
Coccioni and others (1988)
Gonzalvo and Molina (1992)
This study
LAD
T.
pomeroli Berggren and others (1995)
Coccioni and others (1988)
Gonzalvo and Molina (1992)
This study
LAD
G.
semiinvoluta Berggren and others (1995)
Base
Zone
E15
Cocciol).i and others (1988)
Gonzalvo and Molina (1992)
This study
FAD
C.
inflaia Berggren and others (1995)
This study
erto been achieved. A list
of
datums and their positions
in comparison to earlier work (Coccioni and others,
1988; Gonzalvo and Molina 1992) is shown in Table
l.
The cited ages
of
the LADs
of
Hantkenina alabamensis
(base
of
Zone
01),
Turborotalia cerroazulensis, and
Globigerinatheka index (base
of
Zone E16) are essen-
tially identical with those compiled by Berggren and oth-
ers (1995). The FAD
of
Turborot(1lia cunialensis at 35.3
Ma
is slightly older than quoted in Berggren and others
(1985, 35.2 Ma). A greater discrepancy exists for the
LADs
of
Turborotalia pomeroli (35.7 Ma, compared to
35.3
Ma
in Berggren and others, 1995) and Globigeri-
natheka semiinvoluta
(Base
of
Zone E15; 35.8 Ma, com-
pared to 35.3
Ma
in-
Berggren and others, 1985). These
datums clearly lie within Chron C16n in the Massignano
section (see Lowrie and Lanci, 1994, for paleomagnetic
data), not C15r as stated in Berggren and others (1985).
The LAD
of
G.
semiinvoluta is very well characterized
at Massignano, as it is continuously present (although
rare) through the lower part
of
the section until its abrupt
disappearance at 4.55 m above the base
of
the stratotype
section. The age
of
the FAD
of
Cribrohantkenina infiata
is not reliably determined at Massignano (contradictory
to Berggren and others, 1995) because all hantkeninids
are absent in the lower part
of
the section, and their first
appearance in the section represents a local influx.
5.
We have encountered significant taxonomic problems re-
garding the recognition
of
Cribrohantkenina lazzarii
(Pericoli), which affects the concept
of
uppermost Eo-
Bottom
Age
Top (m)
(m)
Estimated level (Ma)
33.7
19.00 19.50
19.25
:±:
0.25
19.00 19.50
19.25
:±:
0.25
19.00
19.03 19.02
:±:
0.01
33.7
33.8
18.50 18.60
18.55
:±:
0.05
18.50 18.80
18.65
:±:
0.15
18.55
18.60 18.58
:±:
0.03
33.8
34.0
15.00 15.50
15.25
:±:
.25
15.00
16.50 15.75
:±:
.75
19.00 19.03
19.02
:±:
0.01
33.7
34.3
13.50
14.00
13.75
:±:
0.25
13.00 14.00 13.50
:±:
0.50
14.10 14.50
14.30
:±:
0.20
34.3
35.2
7.20 7.50 7.35
:±:
0.15
15.00 16.50 15.75
:±:
0.75
7.00 7.50 7.25
:±:
0.25
35.3
35.3
5.00 5.50 5.25
:±:
0.25
11.00 12.00 11.50
:±:
0.50
4.50
5.00
4.75
:±:
0.25 35.7
35.3
4.50 5.00 4.75
:±:
0.25
4.00 5.00
4.50
:±:
0.50
4.50 4.60 4.55
:±:
0.05
35.8
(35.5)
Not reliable in this
section
cene Zone P17 as used by Berggren and others (1985).
Zone P17 was introduced
by
Blow (1969, 1979), who
identified it as a biostratigraphic interval between the
LADs
of
Cribrohantkenina and Hantkenina spp., the lat-
ter
of
which is now regarded as denoting the Eocene/
Oligocene boundary. For Blow,
Cribrohantkenina was a
mono specific genus with
C.
infiata as the only valid spe-
cies and with
C.
lazzarii listed among its synonyms.
Martinez-Gallego and Molina (1975) introduced a dif-
ferent concept
of
Zone P17 in which Cribrohantkenina
was split into two distinct species
(c.
infiata and
C.
laz-
zarii). Cribrohantkenina infiata,
which was regarded as
a more rounded and inflated form, was documented as
disappearing first from the record, whereas the more po-
lygonal
C.
lazzarii was observed to persist to the same
level as the disappearance
of
Hantkenina spp. In effect,
these observations, which have been supported by sub-
sequent studies on several
of
the Italian and Spanish sec-
tions (Molina 1986; Nocchi and others, 1986; Molina
and others, 1988; Coccioni and others, 1988), indicated
that Zone P17
in-the sense
of
Blow (1969, 1979) does
not exist. Nevertheless, by splitting Cribrohantkenina,
these authors were able to form an alternative concept
of
Zone P17, namely the interval between the
HO's
of
the
inflated species
of
Cribrohantkenina
(c.
infiata, accord-
ing to their taxonomic concept) and
Hantkenina spp.
Therefore, the concept
of
Zone P17 according to Marti-
nez-Gallego and Molina (1975) and the subsequent studies