D F1yde<!i, Ch. Hemleben & S Belle<s: Nannofossils in the sapropellayers ... , p. 203 - 21 I.

Journal of Nannoplankton Research, 24, 3, 2002.

DISTRIBUTION OF CALCAREOUS NANNOFOSSILS IN THE
SAPROPEL LAYERS OF HOLE 69-2SL, METEOR CRUISE 40/4,
EASTERN MEDITERRANEAN SEA
Dimitris Frydas*, Christoph Hemlebent & Spyridon M. Bellas"*Dept. of Geology, University of Patras, GR-26500 Rion/Patras, Greece, dfrydas@upatras!gr;
tinst. of Geology & Palaeontology, University of Tubing en, D-72076, Tubing en, Germany;"Inst. of Geosciences, Division of Palaeontology, Free University of Berlin, Malteserstr. 74-100, D- I 2249 Berlin/
Germany & Geology Dept., Patras University, GR-26500 Rion/Patras, Greece, drbellas@zedat.fu-berlin.de

Key words: sapropels, Mediterranean Sea, Quaternary, calcareous nannofossils
Abstract: Calcareous nannoplankton associations from the sapropel layers of the gravity core M40/4,
Station 69-2L, south-eastern Mediterranean Sea, have been examined. The investigated core mainly
consists of nannofossil-/foraminifera-bearing mud, sapropel layers SI to SS/6 (except S2), and tephra
layers. A subtropical coccolitb association was recognised in sapropels SI, S4, SS, SS/6, while a temperate
one characterises S3. A reversal in dominance between Gephyrompse< muelleme and Emilie<nie< huxleyi
was observed in sapropel S3 at 256cm subdepth. A significantly lower coccolith diversity was observed in
the sapropel and tephra layers themselves, as in the foraminiferal mud, probably because of the influenceof anoxic conditions, including bacterial activity, or ash-falls on the coccolith assemblages. In addition,a moderate to intensive corrosion characterises the nannofossils in the bioturbated upper part of some
sapropels.

Introduction
The Mediterranean Sea is a marginal basin that is almost
entirely surrounded by continents. Therefore, bothhydrography and sedimentation processes are controlled
by the regional climate and topography of the adjacentland-masses. High evaporation rates and deep winterconvection initiate the formation of warm and oxygenrich deep and intermediate water-masses in the southern
Adriatic Sea, the Levantine Sea, the south-westernAegean
Sea and the northwestern Mediterranean Sea (Pickard &Emery, 1990). The primary production in the surface-waterthat controls the flux of organic matter to the sea-floor
exhibits a strong seasonal and spatial variability. While
primary productivity rates are generally low from summer
through winter, deep convection of the water-column andnutrient input by rivers cause a pronounced increase inphytoplankton activity during spring, particularly along
the coastal areas (Amone, 1994). The deep parts ofthe
eastern Mediterranean can presently be regarded as a foodlimited enviromnent, and exhibit oligotrophic and welloxygenated conditions (Miller et al., 1970; Pickard & Emery,1990).
One of the main sedimentological characteristicsof the eastern Mediterranean is the cyclic deposition ofsapropels that point to drastic changes in the marine
enviromnent. Previous studies on the origin of these anoxic
events discuss both severe decrease in the ventilation of
the subsurface waters (Thunell & Williams, 1989;
Rossignol-Strick et al., 1982; Fontugne et al., 1989; Thunell
et al., 1983; Tang & Stott, 1993) and increased
palaeoproductivity, followed by high organic-carbon flux
rates to the sea-floor (Castradori, 1993; Sancetta, 1994). A
temporal correlation has been observed between theaccumulation of sapropels and the precessional cycle ofEarth's orbit (Schmiedl et a! ., 1998). Furthermore, a linkhas been established between the sapropels and: (1)203

intensifications of the Asia-Africa transverse monsoons(Rossignol-Strick, 1985; Kleijne, 1990); and (2) increased
activity of Mediterranean depressions followed byenhanced humidity in the northern borderlands of theeastern Mediterranean (Rohling, 1994, 1999; Rohling &Gieskes, 1989). Geochemical evidence indicates that
sapropel formation has been promoted either by increased
productivity (Calvert et al., 1992; Ho well & Thunell, 1992)
or by a model combining both higher productivity andbetter preservation persisting during precession minima(Nijenhuis et al., 2001 ).
The Late Quaternary climate of the Mediterranean
region is generally characterised by humid interglacials
accompanied by low ? 18 0 values, and arid glacials defmedby high ? 18 0 values (Rossignol-Strick, 1985; VergnaudGrazzini et al., 1977, 1986). Schmiedl et al. (1998) reportedchanges in the benthic foraminifera fauna of the Ionian
Sea in the last 330kyr, while Aksu et al. (1995a, b) and
Geraga et al. (2000) evaluated various microfossil data fromshort cores of the Aegean Sea for palaeoenviromnental
changes in the last 18kyr (including only sap rope! S 1).
Phytoplankton associations concerning the geographic,
as well as stratigraphic, distribution ofHolocene to Upper
Pliocene coccoliths, silicoflagellates and diatoms in theeastern Mediterranean area were reported by Schrader &Matherne (1981), Danelian & Frydas (1998), Pearce et al.
(1998), Frydas (1999), Negri et al. (1999) and Negri & Giunta(2001).
In this paper, we mainly report on the calcareous
nannofloral content of five successive sapropel layers,
S1, S3, S4, SS and SS/6, from a gravity-core in the eastern
Mediterranean Sea. Both a quantitative study of selectively
important species through the core, and a semiquantitative
presentation of the whole assemblages in each sapropel,
have been performed. Based on this diversity data, andcorrelations between the individual sapropels, specificJournal ofNannoplankton Research, 24, 3, 2002.

D. Frydas, Ch. Hemleben & S Bel/as: Nannofossils in the sapropel layers ... , p. 203 - 211.

Wal rDepth- -IO<kn- -200m- -IOOOm- -lSOOm- -2000m- -2500m- -JSOOm- JSOOm•

METEOR 4tV4, Stations 65 to 70

e ODP Leg 160, Sites 969,971

Figure 1: Bathymetric map of the eastern Mediterranean Sea, with location of thecore site, M40/4-69, S of Crete Island, and regional map of the Mediterranean Sea
and investigated area in the inlet

Species

distributions related to sapropel level , as well as
quantitative differences between the assemblages fromsapropel and non-sapropel sediments, are described. It is
postulated that such variabilities are most probably related
to palaeoecological and palaeoceanographic circulation
changes during the Late Pleistocene to Recent.
Material and methods
The gravity core, 69-2SL, logged on board the research
vessel Meteor (Federal Republic Germany), was recoveredfrom the Levantine Basin (eastern Mediterranean Sea) anddeposited at the University of Ttibingen, Institute of
Palaeontology. The site of Core 69-2SL is located at
33°51.57'N, 24°41.45'£, at a present water-depth of2154m(Figure 1). Sampling took place at 5cm intervals throughthe sapr opel formations and at 1Ocm intervals(approximately) through the grey-yellowish to brownishgrey, nannoplankton- and foraminiferal-pteropod-bearing
muds, which are moderately bioturbated in their upper parts(Figure 2). The most significant characteristic of this core
are here considered to be the easily-recognisable sapropel
formations, SI, S3, S4, S5 and S5/6 (Hernleben eta!., 1999).

Several dark grey to brown-brownish yellow
tephra interlayers were observed as well.
A total of 63 samples were analysedfor calcareous nannofossils. At least 300
coccoliths were identified per sample, usinga Leitz DIALUX 20 EB photomicroscope ata magnification of l250x (normal andpolarised light). The development of theeight most important species abundances
through the studied core is presented in
Figure 3. Preparation of smear-slides forlight-microscope examination followed
standard procedures (Bown & Young, 1998).
Additionally, several samples of thesapropel layers were examined at the Free
University of Berlin, Institute of
Palaeontology, under a Cambridge
Instruments scanning electron microscope(SEM: Plate 1) to facilitate fme taxonomic
identifications . Generally, all of thenannofloral assemblages are moderately towell preserved. Emiliania huxleyi
preservation seems to suffer most, or
alternatively the ultrastructure could be moredelicate and more easily corroded than thatof the other species, as it is shown in Plate 1(Figures 11 and 12). All the studied smearslides (SMR), as well as the negatives (NG),are stored in the Laboratory ofMicropalaeontology, University of Patras(SeriesMeteor40/4, SMR-199811 to-63, NGSMR-1998/1 to -6, x36).
Below (Table 1) is the identification
scheme used for differentiating between thevarious gephyrocapsids , based onmorphometric measurement of various
parameters.

G. caribbeanica
G. ericsonii
G. margerelii
G. muellerae
G. oceanica

Angle

Length

(ao)

(~m)

45
26
39
24
54

4 .0
2 .7
2.2
3.6
3.9

B!L
(%)
88
76
73
75
83

PIL
(%)
46
54
58
51
42

Table 1: Mean values of the measured morphological elements ofthe gephyrocapsids: a0 = bridge angle; Length of coccolith; B/L =relative roundness = B/Lx!OO (B = coccolith breadth; L = coccolith
length); P/L = relative pore width = P/Lx!OO, (P = pore size)

Stratigraphic framework
Sapropel layers represent a first-class stratigraphic tool
for the interval covered by the studied core and, moreover,for intra-Mediterranean correlations. According to recent
high-resolution data from the adjacent Ionian Sea,
published by Schmiedl et al. (1998), the following ageassignments have been made for the recovered sapropels(kyr BP): 78 to 80kyr for S3, 105 to 108kyr for S4, 119 to
124kyr for S5 (at c.520-540cm depth), and 163 to 167kyr for
the upper (younger) part of S6, which was located at
c. 770cm core-depth. Since our S5 sapropel is placed at a204

D. F1ydas, Ch. Hemleben & S Bellas: Nannofossils in the sapropel layers ... , p. 203 - 211.

Journal of Nannoplankton Research , 24, 3, 2002.

METEOR 40/4 69-2 L

gyBR

llop

0.5
ye BR

t====t1.0

pal brYE_;-99- IOScm. A h, pale brownish yellow, sandy with disturbed
upper and lower boundary

L 105-20 cm. Foram- nno Ooze, faint di genetic
banding throughout

1.5
pal ye OR~~~:j - 20 -219cm. Ash, brown, pebbles at base, graded bedding,

2 .0

..
H
H

2.5

H
3.0

-

-

base

alteration minerals concentrated'-219-236cm. N nno-Foram Ooze, vivid coloration of grey, blui b
imprcgnition monling in diffuce bands

1--:.,.....f"'=':-.-i ~ and greeni h hue~

1--""'----i

236-245 m. propel, banded t base, bioturb ted at top
245-246cm. A h, dark grey, ndy
246-247cm. propel, homogenous

248-250cm.

anno-Foram Ooze ,interlayer, grey

2S0-270cm. propel, banded in upper and lower pan,\\ bomogenou at centren-!-==:..Al....::.=......t\ [ 270-30 cm. Nanno-Foram Ooze, bluish to grey
l30 -324cm.

3.5
_ I_

I
4.0

L \

1

~ gy OL
GY

n
4.5

base

\...363-3 7cm. propel, laminated and banded throughout.
Thin ash ringer at 3 Ocm

\_

yeGY
1======1GYpropel, biocurbated top, banded324-363cm. anno-Foram Ooze, o idation front at 349cm.
Homogenous bum-down front from 349 to 363cm

3 7-425cm.

nno-Foram Ooze, grey to yellowi h grey

425-429cm. Sapropel, bioturb ted\_ 429-SOOcm. nnno-Foram Ooze, brownish grey, yellowi h grey,
parti lly mottled black. Manganese impregnations throughout

brGY

KEY
LITHOLOGY

r-::::::'1

L:.J

.

:

Ivvvj

anno/Foram Ooze

Volcanich

TRUCTURES-Graded bedding- Occasional laminae
lCHNOFO~- Primary lamination-banding

1L

U - Moderately bioturbated- Slightly bioturb tcd

Figm·e 2: Lithology, sedimentary structures and stratigraphy of the studied gravity-core, 2SL (Station 69), from the SE Mediterranean Sea

depth ofbetween 363 and 387cm, it is obvious that much
lower sedimentation rates (3.00 to 3.35cmlkyr) dominatedin our core location compared to those in Core M2 5/4KL13 ofSchmiedl et al. (1998).
In a biostratigraphic context, a few to common
occurrence of E. huxleyi places the assemblage in thehomonymous zone, NN21, ofMartini (1971) and CN15 of
Okada & Bukry (1980). The high abundance of E. huxleyi(>20%) in the upper part of the core (above 52cm) makes
an assignment of this core-interval (0 to 52cm) to the E.
huxleyi Acme Subzone, coded MNN21 b by Rio et al. (1990),
possible. The lower core interval (53 to 500cm), with

205==========================

D. Frydas, Ch Hemleben & S Bel/as: Nannofossils in the sapropel layers .. , p. 203 - 211.

Journal ofNannoplankton Research, 24, 3, 2002.

Depth
Core
(in Clll) M40/ 4-69

Calcareous nannofossil distribution [\](Selected species: 1-8)
0

"

10

20

30

40

50

0

10

20

Sl

V

30

Age Isotope(ka) Stages
400-.-- - . ,1 (I)so- ----

lOG-

3 (I)

150
50
200

25()-

.....

30o-

3So-

40Q-

Intra-S3

71.5

S3
S4

-------lOO

ss
Intra-SS

5 (I)

SS/6
45Q-

SOv

140

*: tncr asing of E.buxleyi
over than 10'

R : Reversal of dor.UnanceE.buxleyi/G. •ueller•e

1.
2.
3.
4.

E. hu.~ leyi
G. •ueller11e
G. ericson11
G. oce~tnica

5 . G. c~tribbeanicll
6 . Hel cosphaerids
7 . c. lepcoporus
8 . u. sibog11e

Figure 3 : Quantitative percentage cumulative distribution of the eight most important calcareous nannofossi l species. Left: Core 69-2SL,Meteor Crui se M40/4, Station 69, S of eastern Crete; right: correlation to Isotope Stages 1 to 6

predominating Gephyrocapsa oceanica, Gephyrocapsa
muellerae and fewer E. huxleyi, is simply referred to as theE. huxleyi Zone (MNN2la).
Results
After the morphometrical analysis of 300 gephyrocapsid
specimens under the SEM, two groups of small coccolithassociations could be determined (work in preparation,
see Table 1, above): (1) coccoliths that have a mean bridgeangle of26 ° and 24° and a mean length of2.7 and 3.6f!m.
Gephyrocapsa ericsonii and G muellerae, belong to thisgroup, respectively. They correspond to the transitional
to sub-Arctic associations of Bollmann (1997); (2)coccoliths with a mean bridge-angle of 45 ° and 54°, and amean length of about 4.0f!m. This group includes large
gephyrocapsids, such as Gephyrocapsa caribbeanica andG oceanica, and corresponds to Bollmann's (1997)
subtropical coccolith association.
Moving downcore, from the top of the core (Ocm)to the sample at 251 cm, the main components of thenannofloras in S 1 and S3 are E. huxleyi and G oceanica
together with various helicosphaerids , Calcidiscus

leptoporus and Umbilicosphaera sibogae found as freecoccoliths (see Table 2, Figure 3). In general, the specimensof E. huxleyi in this interval belong to the genotype
variation C ofYoung & Westbroek ( 1991 ). A small overall
and central-area size, and a delicate appearance of the
distal-shield elements, generally characterise variety C. The
central-area elements may be entirely or partly absent, as
in our case (Plate 1, Figures 24 and 16, respectively).
E. huxleyi distinctly dominates (values up to 26%)
from Ocm down to the samples interval between 251 and256cm (abundant, Table 2), though in reducing
percentages, particularly towards S3 (falls to under 10%
below star in Figure 3). Within the same stratigraphic
interval, G muellerae is few to common (Table 2, Figure 3).
Below 251 cm, G muellerae frequency increases toabundant, and consistently dominates the assemblage
down to the bottom of the core, while E. huxleyi is common
down to 323cm, and then decreases to few (2-5%) to thebottom of the core. G oceanic a shows the same behaviouras G muellerae below S3 down to the bottom. It can beassumed that the assemblages in the interval between 251
and 256cm represent the so-called ' reversal in dominance206

D. Frydas, Ch. Hemleben & S Bel/as: Nannofossils in the sapropellayers ..., p. 203 - 211.

S3

S4

ss

l<\ r F F r IF r r r
A k:: F F
IF r c

r r

236
241
24s
251
256
261
267
308
313
318

F IF
K; C C K; F F
R IF
r ~ IF F t IF r r r r F
IR
r ~ IFr IF r r r r F
IF IR
c ~ F F A IF
A ~c F
r ~ F F A F r A r r r r
IF
A IF F A IF r A r r F
IF R IF

363
368
373

F V\. IFF I\ IF
F A

387

A IF

r

A r F F r
A r IF F r
C ~ IFrr (' c r

IF r r r r
F
r r r

r

IF

R
R

r ('

IR

le C F iA A F k:; IF r
r r IF ~ A F r IF
r A IF ~ A F rk:; A F ~ ~r K; IF

IF

85186 f--4'-"25"--f-IF-lA~IF--Fr'-Fr-lF'--ff-+~'-f-F-Ir"'--flc"-+--+--fiF'-+-l--l~F--+-fR4--+-I
429 F A IF r r F IF ~ F r r
Table 2: Distribution of calcareous nannofossils in sapropels, gravity-core 2SL(Station 69). A= abundant (> 10%); C = common (5-10%); F = frequent (2-5%); R rare (1- 2%) ; r = reworked

between E. huxleyi and G muellerae' , a significant
biostratigraphic event previously reported by otherauthors from Mediterranean Sea cores (e.g. Thierstein etal., 1977, and see discussion below).
Generally, it appears that all coccoliths observedin S3 occur in lower frequencies, or present negative peaks .
or lows, than within the other layers above S3 to the top.
Normally, each species is represented by < 10% frequency
in S3. This is also the case for the nannofloras in theyoungest sapropel, S1, with the exception of E. huxleyi,
which is abundant and which increases within S 1 to 24%(Figure 3).
Moving further downcore, the deeper sapropels,
S4, S5 and S5 /6, are characterised by an increased
abundance of helicosphaerids, such as Helicosphaera
carteri, H. hyalina and H. wallichii, with a meanabundance usually ranging between 12% and 16% (Figure3). The latter sapropels are associated with well-represented
gephyrocapsids, consisting mainly of G muellerae(ranging between 10% and 20% on average) and G
oceanica (up to 15%). Both these species' frequencies
increase downwards. Subordinately, G caribbeanica (~3· oo). G eri sonii (- - -8%), and very small Gephyrocapsa
s . L _
were observecL C. leptoporus ranges from· ec ly below S3 )and4%

Journal of Nannoplankton Research, 24, 3, 2002.

U. sibogae and Syracosphaera pulchra,having averages ranging between 10 and
15% in the total assemblage. In S4, S5 andS5 / 6 particularly, U. sibogae clearlydecreases, and ranges between 5% and 9%(Figure 3 ), while S. pulchra, though notconsistently present, shows few to common
abundances (Table 2).
Considering the cumulative
distributions in the sapropels (Figure 3), theabsolute frequencies of some species, suchas G caribbeanica, G ericsonii and U.
sibogae, remain almost constant through thewhole core with minor fluctuations of theorder of 1 to 2%. It is also interesting toobserve that G caribbeanica presents its
abundance minima directly above (or,alternatively, directly after) sapropel
deposition (S3, S4 and S5).
The distinctive decrease, or low
trend, in the representative values of nearly
all the species is clearly demonstrated, fromthe selected calcareous nannofossil
cumulative distribution through Core M40/
4-69 (Figure 3), and particularly from thedevelopment of their frequencies at thelevels of the sapropel layers. E. huxleyi is
the only taxon which decreases consistently,
downcore to the level of S3, coded R(negative correlation with depth) , thenbecoming more stable (~5%). Comparing semiquantitativeand quantitative frequency distribution data of all thesapropels in Table 2 and Figure 3, the most pronounced
and longest-duration values decrease is recorded within
the thick S3 between 236 and 267cm. Negative peaks, orlows, in the selected nannoflora values detennined for S5
are also important, but not in the order recorded for S3.
Discussion
The euphotic zone is a well-known common habitat forcalcareous nannoplankton , with minor exceptions.
Additionally, their being primary producers makes them afirst class, sensitive group for monitoring surface-waterchanges and fluctuations related to recent or pastenvironmental variations.
As previously reported, G oceanica is one of themain components of the calcareous nannoflora throughthe studied core from the eastern Mediterranean. In recent
seas (Indonesian Archipelago), the dominance of G
oceanica (February-March), followed by occurrences ofUmbellosphaera irregularis and E. huxleyi have also been
observed. In warm August water-samples, G oceanica andE. huxleyi are the most frequently-occurring species,
followed by C. leptoporus (Kleijne, 1990). In the
Mediterranean Sea particularly, G oceanica increases inabundance in lower salinity samples than in surrounding-·where · drops in abundance (Knappertsbusch 1993).
· darao · ed

Journal of Nannoplankton Research, 24, 3, 2002.

. D. Frydas, Ch. Hemleben & S. Bel/as: Nannofossils in the sapropel layers ... , p. 203 - 211.

the occurrence of G oceanica-enriched floras, thoughrather sporadic, correlates with high water-temperature,
low salinity and low water-density in the upper photic zone
community. Common to abundant G oceanica in thesapropel layers of Core M40/4-69 could have, therefore,
been caused by reducing of surface-water salinity during
deposition of the S 1 and S3, S4 to SS/6. This could, in turn,have caused shoaling of the pycnocline into the lower
euphotic zone, and maintenance of a Deep Chlorophyll
Maximum (DCM), a highly productive layer of enhanced
production which might have caused high accumulationof organic matter, leading to fonnation of sapropels, acomposite procedure also suggested by Castradori ( 1993)
for the origin of the eastern Mediterranean sapropels.
Florisphaera profunda contributes <2% to 3%
to these nannofloras. It is sporadically present in all thestudied sapropels, except SI. Probably, its occurrence islimited by the oligotrophic surface-water conditions of thesouth-eastern Mediterranean Sea, in contrast to the northwestern Pacific Ocean and the northern South China Sea,
where a bloom of F. profunda, caused by high surfacewater fertility, has been observed (Ahagon et al., 1993;
Wei et al., 1997). This taxon is considered to be a goodpalaeoproductivity proxy, and its abundances can be used
for monitoring the depth of the nutricline, which controls
nutrient availability (Molfino & Mclntyre, 1990; Castradori,1993). It represents a main component of the deep-water
assemblages developed at depths between approximately
60 and 180m (Re id, 1980). Recently, F. profunda seasonal
fluxes in the deep-photic layer were studied off Moroccoand the Canary Islands, where abundance-peaks wererecorded between January and March and in November(Sprengel et al., 2000). F. profunda's sporadic occurrencesin the sapropels studied here could possibly indicate suchseasonal fluxes .
The reversal in dominance between E. huxleyi
and G muellerae has been reported by Flores et al. ( 1997)
in the western Mediterranean Sea at about 73kyr, while
Violanti et al. (1987) estimated this event at 8Skyr from the
Tyrrhenian Sea. In an earlier work, Thierstein et al. (1977,
pp.403-404) recorded, in transitional waters, the "reversal
in dominance between Emiliania huxleyi andGephy rocapsa caribbeanica", and dated it atapproximately 73kyr. According to our data, the reversal(coded R in the cumulative distribution diagram, Figure 3)
falls within S3, below Glacial Isotope Stage 4 and shouldhave an age of71.Skyr, approximately.
Warm interglacial periods are characterised by ahigher phytoplankton percentage than glacial (cold)
periods. Although SI , S4, SS and SS/6 are considered tohave been deposited within warm interglacial intervals, it
is here shown that sapropel associations are represented
by low calcareous nannofossil diversities, and show
signj.ficant dissolution. The elements of E. huxleyi and
Ceratolithus sp. are partly corroded or dissolved (Plate 1,
Figures 11, 12, 14 ). In contrast, C. l eptoporus,
Rhabdosphaera clavigera, U. sibogae and thehelicosphaerids are proved to be more solution-resistantin the sapropel layers, as shown by their good state ofpreservation and consistent abu-ndances (Figure 3 ).

Progressive alteration, due to processes such as
dissolution, of the coccoliths of E. huxleyi is probably
responsible for the significant drop in abundance
downcore of this taxon, particularly below S3. This might
be indicative oflong periods of suspension, or low sinking
speed in the water-column (Broerse et al., 2000), a factwhich in turn points to low sedimentation rates for the
lower part of the studied core (2Sl to SOOcm), perhaps due
to strong subbottom oceanographic currents. Anothersynergetic role might have been the great depositiona1
palaeodepth that these coccoliths were deposited at.
Moreover, bacterial activity and populations werestudied from the upper sediment and sapropellayers (downto SS) by Overmann et al. ( 1999). The main sites were KLS1Station 69 (Figure 1) and the anoxic Urania Basin at Station
76, SW of Crete. Significant microbial cell numbers andintense activity were recorded, even in the deepest samplesof SS, which might have provided favourabl e conditions
for the growth and survival of carbonate chemotrophic
bacteria. Total numbers of bacterial cells reached values ofabout 10 8 per cm 3 in all sapropel layers of Gravity-core
M40/4-69.Additionally, the water in the anoxic brine fromthe Urania Basin below 3470m was found to containenormous concentrations (up to 24mM) of free sulphide(H S), while the concentration in the underlying sedimentwa~ only 3mM (Overmann et al., 1999).
It seems, therefore , that the mo st extreme
environmental conditions occurred during sapropel
formation and deposition. Thus, either coccoliths wereprevented from settling, or their preservation potential was
minimised, or both processes worked together, as in thecase presented here . As a consequence , coccolith
diversities become very low, or even the whole nannoflora
disappears. This is due probably to the influence of anoxia,
including intensive bacterial activity (Overmann et al.,1999), or to additional ash-falls on the coccolithassemblages (Thunell et al., 1983; Keller, 1994; Keller etal., 1978; see. ash-layers in the present core, Figure 2). But,in contrast to the benthic foraminifera fauna from the Ionian
Sea to the west, where the diversities remained very low
some thousand years after the cessation of anoxic
conditions, especially after deposition of S 1 and SS(Schmiedl et al. , 1998), coccolith associations restabilised
within a short interval after sapropel formation was
terminated. This is clearly shown particularly directly above
S3 , where the increase in abundance of some taxa is in theorderoflO to 20%.
Additionally, and in contrast to the impoverishedcalcareous nannoplankton , well-preserved opal
phytoplankton and zooplankton assemblages, containing
diatoms, silicoflagellates and radiolarians, have been found,described and illustrated from SS by Danelian & Frydas(1998) and Pearce et al. (1998), close to Station 69 (ODP
Sites 969 and 971: Figure 1). Opal phytoplankton were notaffected by carbonate chemotrophic bacteria, and therefore
present a high preservational potential.

1.

208

Conclusions
The reversal in dominance between E. huxleyi and G
muellerae was recognised in Core M40/4-69 and was

D. F1ydas, Ch. Hemleben & S. Bel/as: Nannofossils in the sapropellayers .. , p. 203 - 211.

2.

3.

4.

5.

6.

7.

placed at c. 71.5kyr, thus pointing to a slightly younger
age than in other, similar studies of the Mediterranean
Sea.
Generally, a quantitative decrease was recorded in thepercentage distributions of the eight selectedcalcareous nannofossil species evaluated in thesapropels, relative to the non-sapropel sediments ofthe studied core.
The most prominent percentage decrease wasobserved in S3, but it must be noted that this was the
thickest sapropel recovered (among the five sapropels
studied).
A decrease in the quantitative composition of thewhole assemblages in the individual sapropels wasclearly observed.
Despite this decrease (point 4) in the sapropels, a few
species, such as C. leptopor!'s and the various
helicosphaerids, are still well-represented (seem notreally to be affected).
Recovering rates of the coccoliths above the sapropel
layers, immediately after the anoxic events, are quite
quick (rapid rejuvenation) in relation to published datafrom foraminifera.
F profunda is, surprisingly, found in only rare to few
frequencies, in relation to other Mediterranean studies.

Acknowledgements
DF is indebted to the German Ministry of Research forfacilitating his participation on the RJV Meteor during its
cruise from Piraeus to Malaga (21.1.98 to I 0.2.98). DF also
thanks the German Academic Service (DAAD) for
supporting two months' research at the Free University
Berlin, Division ofPalaeontology (Prof. Dr. H. Keupp), andMr. W. Mueller for his assistance concerning SEM imaging(F.U. Berlin). Fruitful reviews of the first draft by Drs J.-A.
Flores and J.A. Lees are gratefully acknowledged.

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D. Fryda.r. Ch. Hem/eben & S. Sellas: annofossils in the sapropcllayers... , p. 203 - 211.

Journal of Nannoplanhon R

arch, 24, 3, 2002

Plate 1
Calcareou nannofo il re o ered from gra ity-c re 2 L, ea tern Medit rranean a (Meteor crui e M4 /4,tation 69). Depth from t p of core. All di tal coccolith ie except Fig. l7 (pro imaJ view). Bars = I J..liTl211