Stratigraphic and paleoceanographic significance of Late Quaternary pteropods from deep-sea cores in the Gulf of Aqaba (Elat) and northernmost Red Sea

Marine Micropaleontology, 7 (1982) 53--72 53 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

STRATIGRAPHIC AND PALEOCEANOGRAPHIC SIGNIFICANCE OF LATE QUATERNARY PTEROPODS FROM DEEP-SEA CORES IN THE GULF OF AQABA (ELAT) AND NORTHERNMOST RED SEA

A. ALMOGI-LABIN

Department of Geology, Institute of Earth Sciences,

(Revised version accepted July 1, 1981)

The Hebrew University of Jerusalem, Jerusalem (Israel)

Abstract

Almogi-Labin, A., 1982. Stratigraphic and paleoceanographic significance of Late Quaternary pteropods from deep-sea cores in the Gulf of Aqaba (Elat) and northernmost Red Sea. Mar. Micropaleontol., 7: 53-72.

The quantitative distribution of 16 thecosomatous pteropod species from four deep-sea cores recovered from the Gulf of Aqaba (Elat) and northernmost Red Sea is summarized. The distribution facilitates a relatively high resolution stratigraphic subdivision of the 6--8 m long core sequences and their correlation. The sequences of pteropod assemblages can be related to oxygen isotope curves and thus dated beyond the radiocarbon-range. The oldest strata penetrated are dated at about 150,000 yr B.P.

Considering the present-day distribution of the species recognized, the core assemblages are of a tropical-- subtropical character throughout the Late Quaternary. On the basis of the composition of the living pteropod populations in the hypersaline (41°/~n), moderately oligotrophic and desert-enclosed Gulf of Aqaba, the pteropod core assemblages, associated foraminiferal assemblages, and the oxygen isotope values determined on both groups, a sequence of paleoceanographic changes during the Late Quaternary is derived. These changes are primarily influenced by productivity of the waters and pertain less to temperature and salinity. The glacial periods (isotope stages 2,3,4 and upper 6) were characterized by lower temperature than at present, higher salinity and greater fertility of the waters. During the glacial maxima monospecific Creseis acicula assemblages characterize periods of metahaline (more than 50%o salinity) conditions in highly productive waters. Although not identical in detail, the last interglacial (stage 5) assemblages are similar to the Holocene warm-water oligotrophic ones. Between 8000 and 3000 yr B.P. a short period of slightly higher productivity is indicated.

Introduction Gulf of Aqaba (Elat) and the northernmost Red Sea by the R/V Atlantis H, and were

During the last two decades numerous studied with special reference to calcareous paleoceanographic studies have been made plankton and stable isotopic composition on deep-sea cores from the Red Sea, using (Reiss et al., 1980). The 1830 m deep Gulf of planktonic foraminifera, pteropods, and Aqaba has very special hydrological char- calcareous nannoplankton analyses, as well as acteristics due to the arid climate, high stable isotope geochemistry (Rosenberg- evaporation rates, and straits dynamics. Herman, 1965; Herman, 1968; Degens and Maximum seasonal and bathymetric tempera- Ross, 1969; Schoell and Risch, 1976). ture range 20.5 to 27.3°C, salinity 40.2-- Recently, deep-sea cores were obtained in the 41.6°/00 and density 27--29.5 sigma-t. These

0377-8398/82/0000--0000/$02.75 © 1982 Elsevier Scientific Publishing Company

5 4

r3oo 3 4 ~ 3 0 '

B A T H Y M E T R I C C H A R T

OF THE

GULF OF ELAT-~QABA

";.-<: t

,,

/ DE E~~~ ~o- " ~

"-. ] ", i ~ .... ',~ ~

• -_ ',,~ ~vo

i ] 74 / "

/

TIRAN DEEP

# ;

2 9 o 0 0 '-

ARAGONESE DEEP

2 8 ° 3 0 '-

DAKAR DEEP

2 8 ° 0 0

35

55

conditions produce a weak summer stratification and a nearly homogeneous water column in winter, high-oxygen content throughout the column (4 to more than 6 ml 1-1 ); a very low nutrient content (nitrate max. 7.2 pg-at 1-1, phosphate 1.0 ~g-at 1-1); primary production, 200--1100 mg C m -2 day -1 and low chlorophyll (16--70 mg m -2) (Klinker et al., 1976; Klinker et al., 1978; Levanon-Spanier et al., 1979; Paldor and Anati, 1979).

The cores collected from the Gulf of Aqaba and from the Red Sea proper immediately outside the Straits of Tiran (Fig. 1) indicate relatively high rates of sediment accumula- tion, penetrating strata as old as isotope stage 6 (about 150,000 yr B.P.) (Reiss et al., 1980). Consideration of the Foraminifera assemblages (including displaced shallow- water benthic species), as well as the 5180 values obtained on planktonic foraminifera and on pteropods, lead to the conclusion that during the glacial maximum (at about 18,000 yr B.P.), the winter temperature of waters in the Gulf of Aqaba and in the Red Sea was probably not lower than 14°C, while salinity rose to more than 500/00 (Reiss et al., 1980).

The stratigraphy and correlation of the core sequences as well as their paleoceanographic interpretation are based on the combined records of stable isotopes and of all plankton groups. However, as shown by Reiss et al. (1980) the most detailed and useful biostratigraphic record is that of the pteropods, for which even a few selected abundance peaks and species ratios facilitate precise stratigraphic correlations and are indicative of paleoenvironmental conditions (see Fig. 2). Quantitative changes through time in pteropod assemblages have also been used successfully for paleoenvironmental interpretation in earlier studies of Red Sea cores (Herman, 1968; Chen, 1969; Schoell and Risch, 1976).

The present paper describes the pteropod record in the Gulf of Aqaba cores and dis- cusses its paleoenvironmental significance.

Methods

Core samples taken at 10--20 cm intervals were washed with water through a 149 pm sieve and oven-dried at temperatures below 50°C. Samples with abundant pteropods were split with a Von Daniels (1970) splitter in order to obtain aliquots which contain 300--500 specimens. All euthecosomatous and calcareous pseudo- thecosomatous pteropod specimens from the split were identified under the binocular microscope and counted. In order to avoid bias in specimen-counts, posteriorely broken adult individuals (~ 5%) were ignored. The state of preservation of pteropods in the material studied was usually very good and only in a few samples did the state of preservation present any difficulties in identification. On the other hand, various species could be identified from external molds and replicas. In certain cases juvenile individuals had to be identified under the SEM (Plates I--II).

Remarks on species

Sixteen species of pteropods were identified in the cores examined. They are listed on Fig. 3 which also indicates the species distribution in the stratigraphic intervals recognized (Reiss et al., 1980).

This figure shows those species which were found in the Gulf of Aqaba and in the northernmost Red Sea bot tom sediments, as well as in plankton tows and stratified hauls (Almogi-Labin and Reiss, 1977 and Almogi- Labin, unpublished). The taxonomy of most of the species has been briefly discussed in Almogi-Labin and Reiss (1977). The following remarks on the taxonomy of four additional species are relevant to the present paper.

Fig. 1. Map of Red Sea and Gulf of Aqaba showing location of cores (bathymetry from Hall and Ben-Avraham, 1978, modified).

56

GENERALIZED ISOTOPE

! & CURVE AND STAGES

_ 6~SO ~0 High Low

5O " 4 ~

I00 ~ 5 - 7 5 K

( I 127K ( ~ I N o p,. forams

i raO,u , ~ l ~ b u l l +falc 2

i~#', _

MAIN ASSEMBLAGE CHARACTERISTICS ( - - dominant spec ies ,~2 peak)

FORAMINIFERA

RS GA RS GA RS

sac, rub, siph, uni. ibnUf,l ~ !nfl bu, I- hux_._:, oce, eric

I absenl or rare ~ v ~ l virg 1 ~ ~ D Si h~ ruh rub .,falc troch I~

~infl I infll r u b , c a l , b u l l , s i p h lroch ,virg j oce,hux soc , uni I

i

i - bul l .+ folc. l ~!~virg 2 virg 2~

j -- bu_ 2 bul 2 ~ corib

I soc,rub,pach(L ) siph mfl.

,~bul 3

mfl. 2 ocic 2 vlrg 3 troch 2

PTEROPODA COCCOL ITHOPHORIDA

GA

0ce h~x~

Irib

eric

infl

[ hu×, oce

RED SEA ZONATIONS

E

13_0-

I

rla

lib

m

c o ~ E

-- ~ o- ]2 0D co

[ A

B

E c

i

I D

J

A

B

C

a)

A

Fig. 2. Biostratigraphic subdivision of Gulf o f Aqaba ( G A ) and northernmost Red Sea ( R S ) cores and comparison with other Red Sea zonations with reference to the generalized oxygen isotope curve (from Reiss et al., 1980). sac. = G. saccu l i f e r ; rub. = G. ruber ; s iph. = G. s i p h o n i f e r a ; univ. = O. universa; falc. = G. f a l c o n e n s i s ; cal. = G. calicla; bull. = G. b u l l o i d e s ; pach . = N. p a c h y d e r m a (left-coiling); intl. = L. inf lata; t roch. = L. t r o c h i f o r m i s ; bul. = L. b u l i m o i d e s ; acic. = C. ac icula; virg. = C. virgula virgula; hux. = E. h u x l e y i ; oce . = G. o c e a n i c a ; eric. = G. e r i c son i ; carib. = G. c a r i b b e a n i c a ; D. = diatoms; Si. = siliceous sponge spicules; Roman numerals in isotopic curve: terminations; arabic numerals in curve: isotope stages.

Limacina bulimoides and L. trochiformis (Plate I, 1--7)

Difficulties in separating juveniles of these two species have been mentioned before (Rottman, 1977). However, they can easily

be distinguished (even in specimens smaller than 300 pm) by the more depressed suture and higher spire in L. bulimoides and by the latter's much more crowded striation, especially in juvenile stages.

PLATE I

All figures on Plates I and II are scanning electron micrographs. Numbers refer to sample (5189) and core (71); IS = isotope stage. 1--4. L i m a c i n a bu l i rno ides (d'Orbigny). 1. x 144, 5931/74, IS-l: juvenile. 2--3. 5932/74, IS-1. 2. x 600; note dense striation. 3. x 96; juvenile. 4. x 36, 5781/68, IS-5. 5--7. L i m a c i n a t r o c h i f o r m i s (d'Orbigny). 5--6. 5932/ 74, IS-1. 5. x 108; juvenile. 6. x 600; note sparse striation. 7. x 36, 5954/74, IS-3. 8. L i m a c i n a inf la ta (d'Orbigny), x 48, 6042/V14-115, IS-3. 9--13. Diacr ia q u a d r i d e n t a t a (de Blainville). 9. x 36, 5928/74, IS-l; juvenile. 10. X 18, 5926/74, IS-l; juvenile. 11. x 26, 5808/68, IS-6;juvenile. 12--13. × 10, Nuweiba; 500--700 m. 14--15. Diacr ia t r i sp inosa (de Blainville). 14. x 16, 5868/71, IS-5; juvenile. 15. x 43, 5878/71, IS-5; juvenile. 16--17. H y a l o c y l i s s t r ia ta (Rang). 16. x 66, 5956/74, IS-3; juvenile. 17. x 18, 5932/74, IS-1.

PLATE I

57

1.

58

LIST OF SPECIES

Cavohn/a /nf/exa ( Lesueur, IBIS)

Covo/m/a Iongirostris ( de Blainville, 1821)

Cavohn/a unc/nota ( Rang, 1829}

Cho convexa ( Boas, 1886]

Crese/s acicu/a ( Rang, 1828}

Crese/s ch/erch/oe (Boas, 1886)

Crese/s wrgu/a v/rgu/o (Rang,1828)

Diacria quadridentata (de Blainville, 1821)

D/acria t r ispmoso (de Blainville,1821)

Hyolocylis str loto (Rang,1828)

Li rnoc ina bu/irnoldes (d'Orbigny,1856)

Lirnacina /'nf/ota ( d'Orbigny, 1836)

L/rnac/na trochiforrn/s ( d'Orbigny, 1856 )

Perac//s sp

Perachs reticulata ( d'Orb gny, 1836}

Gtyliola subulo (Quay and Gairnard, IB'Z7)

Plankton i ha~s tows

I

HOLOCENE G ACIAL . . . . INTERGLACI.

3ottom i[Interval I II a b III ~ediment~_sofope- st. I 2 5 4 5

tL ] 2 £ oH,,,o

? -

GLACIAL

IV 6

sp.

p

I

i

Fig. 3. List of pteropod s p e c i e s o c c u r r i n g in th e water column, bot tom sediments and cores of the Gulf of Aqaba and northernmost Red Sea.

Hyalocylis striata {Plate I, 16--17)

The juveniles of this species are not well known (Pelseneer, 1888; Rot tman, 1977). In the core samples containing H. striata there occur many young shells which seem to rep- resent the early stages of this species. The diameter (about 175--200 pm) of these young shells at the point of contact between the striated and the posterior smooth parts is

in the same range as that of the posterior striated end of adult H. striata. This is in apparent agreement with Pelseneer's (1888) illustration. The specimens figured as juvenile H. striata by Rot tman (1977) possess both dendritic, strong longitudinal and horizontal striae and differ, therefore, from H. striata as presently accepted (Tesch, 1946; B6 and Gilmer, 1977). The length of the posterior smooth juvenile (300--325 pro) is also greater

PLATE II

1. S ty l io la subula (Quoy and Gaimard), x 18, 5781/68, IS-5. 2. Creseis acicula (Rang), x 8, 5959/74, IS-1. 3. Creseis virgula virgula (Rang), X 18, 5926/74, IS-1. 4--5. Creseis chierchiae (Boas), 5845/71, IS-1. 4. x 26. 5. x 56, juvenile, 6--7. Clio convexa (Boas). 6. x 47, 5931/74, IS-1. 7. x 7, Nuweiba, 500--700 m. 8--9. Peraclis sp., 5781/68, IS-5. 8. × 66. 9. × 78; apical view. 10--11. Cavolinh~ longirostris (de Blainville), X 6, 6008/V14-115, IS-1. 12--13. Cavolinia uncinata (Rang), x 6, Ras-Burka. 14--15. Cavolinia in f lexa (Lesueur), X 12, 5788/68, IS-5.

PLATE II

59

60

in the specimens from the Gulf of Aqaba than in those recorded by Rot tman (1977). The difficulties encountered in recognizing juvenile H. striata seem to be due mostly to absence of striae on the juvenile shell, which usually occurs separated from the early, striated adult.

Creseis chierchiae (Plate II, 4--5)

The specimens occurring in the cores and attributed to this species agree with Frontier's (1963a, b, 1965, 1973) species concept, based on Boas (1886). Frontier (op. cit.) distinguished two phenotypes, one with a thin-ribbed shell (strictly inner nerithic) and another with a smooth, thick shell (outer nerithic). Specimens which are morphological- ly intermediate were also recognized.

Rot tman (1976) recognized two species, i.e., C. chierchiae and C. bulgia Sakthivel, 1974, although her descriptions and figures indicate that the latter species is identical with the smooth phenotype of C. chierchiae as recorded by Frontier (op. cit.). The shells from the cores of the Gulf of Aqaba and the Red Sea range from smooth to slightly striated, in agreement with the " smooth" to " intermediate" types of C. chierchiae of Frontier (op. cir.). It is of interest to note that both the thick, strongly ribbed and the smooth phenotypes of C. chierchiae as well as C. bulgia occur in low-salinity waters of the Gulf of Thailand and the South China Sea, as well as at Nosy B~, Madagascar.

Peraclis sp. (Plate II, 8--9)

This stratigraphically important species is usually present as external molds, replicas and recrystallized shells in the cores examined. Its identity is not clearly established: the presence of 7--8 prominent ridges on the last whorl near the spire of the flatly coiled, smooth shell indicates similarity to P. moluccensis Tesch, 1903, from which it differs by a broad, columellar membrane and by the greater ratio diameter of aperture to diameter in the last whorl. This latter ratio and the

broad columellar membrane is similar to that of P. depressa Meisenheimer 1906, from which, however, it differs by the presence of the prominent ridges.

Assemblage composition

Fig. 3 shows the assemblage composition in the water column, the bot tom sediments and in the core sequences from the Gulf of Aqaba and northernmost Red Sea.

The quantitative distribution of all pteropod species in the stratigraphically most complete cores (74 and 68) is given in the accompanying Figs. 4--5.

Fig. 6 shows the frequency curves of five selected species in all cores examined, as they relate to the isotope stages. This figure also shows the correlation between the sequences examined and the position and extent of unconformities. (Letters refer to correlation lines.)

Generally, the diversity of the pteropod assemblages is low in comparison with the Northwest Indian Ocean (Sakthivel, 1968). Somewhat higher diversity is noticeable during interglacial stage 5 and at the beginning of the post-glacial stage 1. The lowest diversity occurs during the glacial maxima (stage 2 and upper stage 6).

An unpublished comparison by the author of the percentage distribution of pteropod species (> 200 pro) in the upper 600 m of the water column over a two-year period with the quantitative composition of the assemblages in bot tom sediments (>149 /~m) from the same area (northern basin) of the Gulf of Aqaba indicates that bot tom sediment assemblages reflect faithfully the living ones.

Indications for diagenetic changes including dissolution of pteropod shells are found mainly in isotope stages 5 and 2. In stage 5 many external molds and replicas occur, while in stage 2 in addition to replicas, acicular aragonite overgrowth is found on shells and fragmented specimens occur. Both in stage 5 and in stage 2 the number of specimens is low, but the assemblage of stage 5 is a relatively high-diversity one with dominance

6 1

o

~ e 0 GO

t o

"5 7 ~ -c,l

t m

a_ 5

~5 m I

o

L I .... '/I, gZ

/ / sap OLuilnq 9 o/, ~z 1

°/o~ I J d s o!u!10^o 9 0×aliU b

° / o ~ l Dlnqns S / ~

} D n 9 i 9 0 0 I :

4 . 4 ~ ! z ~ - - - - - ; . . . . . . "! - + - / / sIW JOJ.iLI 9o-il< q L ~

~' J4 ' !

:W ~ - - ~ ,1,4 - " . / \ ,' ~'-. a ,~;0~,~00,,~0,0~u~0,0~ ¢ ~ , 4 V / t \ / \ / L X / \ . . _ira

I " I / t / \ollOlJ.U! q / dds s!~saJ 9 0 1%1 Ix \ J/ \ . - ' " ~ ' I ,I \ ,' \

• ~ ° :::S : °;: o . : ° .o ~ ! : t : ~ : ~ .o 7 .o .o : .° : : o :

J~90"

NI

uJ9 N'

i . I-

80:

102

i-I1# I I J J I I ~ I t lq) i I J t ~1 I i J I I ~ ~ I I ~ ~ ~ i I I [ I ~ I i a ~ a i~ i m i~ I I.I 144~I i~ i i~ i i ~ i i iF Ii~ ~ I~ i i~ ! ,4~ ii~ i( ; ~.14

I ~ l I I @ 1 1 I I H(~ l t I I I~ l i t l t l t J l J j l j l I J I H J I I ~ J J ~-I ~114114 I i ! H I 4 4 I I 1 I L J " 4 I ~ I t I I 1 1 ~ I t a I i ~ I ~ I H I I J ) I I J l I t I I ~ l l H l l 4 1 1 q ~J t ~ a - -

t'LOd ~ t,,L )d i i

. o. ~ oo ~ ~ o ~ ° o ~ o ~ o ~ o ~ oo ~ ~ . . . . . . . o ~ : ~ o

0~ , ~

II II

cJ ,.o o

~ N

~ II II

6 2

W E 60 t--

r r "

t x l

n z

e.~ f

w " i

0 ~

ds S!laOJa d

i sap!ou~!lnq [ -1

i

I olnqns "S

DlO!J lS H

DSouIdSIJI 0

- Dl~luep!Jponb "0

1

i

! / 1

\

s!ulJo~.!qooJl q

OlOl~Uiq

\

i // / I O~ II / \ / k ~ ~IOlIurq/'dds.. $~asaJ 0.~ 04D~i¢ ~ I \

_ i t , _ _ / " , . ~ . , . ~ - . . . . . .z..--.,.~, \ ~ . . ~ . _

i~ ' ~ I ~ = ~ = I i ~ j l l l r F i , ' , ~ I n ? q ~ l ,,J~:~:~" ~ ~.~ '~r ,~;r ,~ ' r ' l i '~ l ! r '~ , ' ~ ' , , i " " ~ , ' ~ , , : i , ~ l l l ~oI ~ol ~o ~ , ~ i I ~ I , j ~ J 1 ~ ~ i ~i ~ ~ ~ I ~ l~m ~ " t ' Io ' ~ ~I ' ° ~i~ '

J f ~ J I ~ I ~ i l ~ i ] r ~ J ~ I ii i j r I I I i I I I I

05

"0 0

.o

"0

cy

e99d ~ - Oe~d

6 3

~,F ° :~

~ ~ ~ ~ ~ ~ o o

0 o i ~

o

o o 0 m

o

~ o o

o ~

)

~ ",%

i J i

!

, I

11

g

c o

o

co

{ ~' , /

,-4

11

\ \ v

o

©

d

0 ~Z

0

,.o

~ 0

0

d ~ 0

, ~ 0

64

of Limacina, while that of stage 2 the lowest diversity one with dominance of Creseis. It seems, therefore, that diagenetic processes did not considerably affect the qualitative and quantitative composition of the assemblages in the cores.

The uppermost interval I, corresponding to isotope stage 1, is generally characterized by the abundance of L. inflata, which is nearly absent in the immediately underlying strata. Within this interval a number of characteristic changes in quantitative composition can be recognized, viz. a lowermost peak of L. inflata with very few L. bulimoides (accompanied by the presence of C. chierchiae), followed above by a very significant increase in L. bulimoides, a relative decrease of L. inflata, and finally a peak of C. convexa. In the two cores from the northern basin of the Gulf of Aqaba (71 and 73) a peak of L. trochiformis preceeds the L. bulimoides peak. This interval is followed in turn again by increase in L. iuflata and gradual decrease of L. bulimoides, until the latter's near disappearance. In the uppermost part of the (triggerweight) cores a slight increase in C. virgula virgula and L. trochiformis is noticeable.

Interval IIa (isotope stage 2) comprises two parts, a lower one characterized by abundance of C. virgula virgula (up to 100%) and an upper one characterized by the abundance of C. acicula (again up to 100%). The thick- hess of this interval changes from core to core, particularly owing to the presence of unconformities. The apparent lower frequency of the two Creseis species in cores 70, 71 is probably due to the lack of strata corresponding to the peaks in cores 74 and 68.

In core 72 a distinct peak of L. trochiformis occurs between the peak C. acicula of interval IIa and the lowest peak of L. inflata of interval I. Judging by the position of this L. trochi[ormis-peak in relation to the isotope curve and to the ratios L. inflata/L, trochi- [orrnis and Creseis spp./L, inflata, one must conclude that it belongs still to interval IIa. It seems, therefore, that this L. trochiformis

peak is absent in other cores or only partly represented (cores 74 and 70), again possibly due to an unconformity. It is notewor thy that in cores V14-122, C61-119K, and C61- 118K from the Red Sea a L. trochiformis peak is present in the same stratigraphic position (Herman, 1968; Chen, 1969).

Within interval IIb (isotope stages 3--4) three subdivisions can be recognized: a lower zone, characterized by a sharp increase of L. trochiformis and by a great abundance of C. virgula virgula, a second subdivision containing mostly L. inflata with very few specimens of other species (this subdivision corresponds to the L. inflata peak indicated by Herman (1968) from Red Sea cores and dated at 25,000--36,000 yr B.P.); and an uppermost zone dominated again by L. trochiformis with many C. virgula virgula.

According to distribution of pteropods the boundary intervals II and III (i.e. between isotope stages 4 and 5) is gradational. On the basis of the fossil record in the cores (planktonic foraminifera, pteropods and cocco- lithophorids, in particular benthonic foraminifera (Halicz and Reiss, in press)) the boundary between isotope stages 4 and 5 (approx. 75,000 yr B.P.) is placed here slightly higher than in Reiss et al. (1980) (maximum difference 40 cm, in core 74). The gradational nature of this boundary by any criteria is indicated as a "buffer zone" in the accompanying figures.

Interval III (isotope stage 5) comprises four subdivisions recognizeable by means of pteropods. The lowermost part is characterized by dominance of L. in[lata which increases rapidly from the underlying interval. Above, conspicuous L. bulimoides and C. couvexa peaks are present, accompanied by a decrease in L. inflata. In the third zone, L. inflata increases again and few L. trochi- [ormis are present. The fourth subdivision is characterized by intermittently abundant L. trochiformis and L. iu[lata, with a prominent L. bulimoides-peak at the top of the zone.

D. trispiuosa occurs throughout interval III, while Peraclis sp. and C. iuflexa occur only in

65

its upper part. Recrystallized shells of pteropods (which can be specifically identified) are frequent in this interval and more so in the southern Gulf of Aqaba cores; they are most abundant in Red Sea core 68.

Interval IV (isotope stage 6) comprises three parts: a lowermost part with dominance of L. inflata and few L. trochiformis and C. virgula virgula; a second zone characterized by the frequency of L. trochiformis; by the presence of D. quadridentata and by an increase towards the top of C. virgula virgula. The uppermost subdivision comprises a well- preserved, monospecific assemblage of C. acicula.

Discussion

The interpretation of the pteropod assemblages from the cores examined, in terms of paleoceanography and paleoclimatology, is necessarily based largely on the empirical correlation between distribution-patterns and ecological conditions in present-day seas. On the other hand, most of the detailed informa- tion available on such patterns concerns normal-marine and hyposaline waters (Frontier, 1973; Rot tman, 1976, 1977, 1978, 1980; B~ and Gilmer, 1977}. The hypersaline, biologically poor Gulf of Aqaba provides an important clue to the understanding of pteropod distributions, both in the present and in the past.

Fig. 7 lists the species recognized in the cores, their occurrence (depth range, season and basin) in the Gulf of Aqaba and northernmost Red Sea, their total and Indian Ocean surface temperature, salinity and depth ranges, as well as the water mass types in which they occur.

In the following, an at tempt is made to interpret the pteropod record from the cores in terms of the different ecological factors.

Temperature and salinity

The known temperature ranges of planktonic foraminifera and the minimum winter isotherms of displaced, shallow water benthic

foraminifera occurring in the cores (e.g., Amphistegina) suggest that winter temperature in the Gulf of Aqaba during glacial periods was lower by 4--7°C compared to the present 21°C (Reiss et al., 1980). The occurrence of Amphisorus in strata belonging to isotope stage 2 may indicate that the maximum temperature drop did not exceed 4°C (L. Hottinger, pers. communication, 1981). Taking into account these glacial--postglacial temperature differences, the glacial maximum -- Holocene /x6180 derived from pteropods suggests a rise in salinity of greater than 50%0 during isotope stage 2 (Luz and Wolf, in Reiss et al., 1980). The C. acicula peaks in the cores are accompanied by total absence of planktonic foraminifera (Reiss et al., 1980) which have been shown experimentally not to withstand salinities of more than about 50o/00 (H. Erez, pets. comm., 1980}. Indeed, considering the total surface temperature ranges of the pteropod species encountered in the cores (Fig. 7), one would be tempted to conclude that water temperature did not fall below approximately 18°C at any time during the Late Quaternary. If Indian Ocean temperature ranges are considered, temperatures of not less than about 20°C are suggested.

There is a definite order of disappearance of pteropod species groups from interglacial to glacial stages and within the latter, viz.: (1) Clio convexa, Diacria trispinosa, Cavolinia inflexa and Peraclis ?moluccensis; (2) Styliola subula and Limacina bulimoides; (3) Limacina inflata, L. trochiformis and Hyalocylis striata; (4) Creseis virgula virgula; and (5) Creseis acicula.

An explanation of this order of disappearance on the basis of temperature changes is both difficult (see Fig. 7) and internally in- consistent. For example, the abundance of Limacina inflata in Red Sea cores has been related by Herman (1968) to warmer periods. Although L. inflata is indeed abundant in stages 1 and 5, it is generally absent in the glacial stages, where, however, the minimum temperature was apparently above the lower temperature limit of this species. On the other

66

S u r f a c e w a t e r t e m p e [ r a n g e .

S u r f a c e S a l i n i t y r a n g e

0 2Oiiiiiii i 30 °C 30 35 40 4.5 %0 i !!i!i:i? , ~ l d i

Covohnla mf lexo i~iiiiii

Covohn/o long/?ostr/s !ilililiiiiiii :i

Cho convexo

Crese/s ac/cu/a

Crese/L~ chierchioe

Crese/s v/}'gu/a virgu/o

D/acria quodr/dento/a

Diocr/o /r/sp/noso

Hyolocyl/s slr/'oto

L imoc/na bu l /mo/des

Limacina inflato

L/rnocmo troch/formis

Perach's sp.

Perachs ret/culata

Styliola subula

ii ~ - ~ -

~JLI:I[] :ii:i::

tttL...

ii!i!iiiiiii

::iiiii: , . . ,~...

lJJ +.L

i::il i!,,

!i{i{iii: .)!i,o

iiiiii!iiii iiiiiJ,

u!!t!!

D e p t h r a n g e

Epi Mesc lBathy

G . A q a b a / P l a n k t o n hauts (;, 200~),O-600rr

N S D i s t r i b . basin

o o ?

o o '2

• x M W

xx x Ep Su,A

o o ?

o * Ep, A,W

xx xx Ep-M (64%)(68%) Su -W

xx x Ep , A

. } . ~ . - - 4 - - - - - I I o o ?

I G e n e r a l D i s t r i b u t i o n

Tr St T Ne B E CV~M

'2' ?

- - - - '2

F i g . 7. Ecological distribution of pteropod species occurring in cores from the Gulf o f Aqaba and Red S e a . T °

range: line, total range; dashed, Indian Ocean range. Stippled range corresponds to present-day conditions in the Gulf of A q a b a . o = less than 2%; • = 2 - - 6 % ; x = 6 - - 1 2 % ; x x = > 1 2 % ; E p = e p i p e l a g i c ; M = m e s o p e l a g i c ; S =

summer; A = a u t u m n ; W = winter. General distribution: T r = t r a n s i t i o n a l ; S t = s u b t r o p i c a l ; T = t r o p i c a l ; N e =

nerithic; B = boundary currents; E = e q u a t o r i a l ; C W M = central water mass. (For sources see list o f references.)

hand, prominent peaks of L. inflata occur within stages 3 and 6.

At present L. trochiformis occurs in the world oceans at temperature ranges slightly higher than L. inflata (Chen and B~, 1964). Indeed, in the Gulf of Aqaba L. trochiformis is nearly absent during the winter-months, when water temperature is lower by about 6°C than in summer {while L. inflata occurs both in summer and winter). On the other hand, L. trochiformis is abundant in glacial intervals, when winter temperature was certainly lower than at present. This indicates that temperature is not the major factor determining the distribution of L. trochiformis.

The exclusive presence of Creseis acicula during the glacial maximum may indicate that this species is able to withstand strongly metahaline conditions (in the sense of Por, 1978) (see also Risch, 1976). Most of the pteropod species occurring in glacial stages 2 ,3 ,4 and 6 live at present under hypersaline (41%0) conditions in the Gulf of Aqaba. How- ever, such species as S. subula, L. bulimoides and H. striata, which are absent in the present-day Gulf of Aqaba and occur in the world oceans in salinities below 3 9 0 0 (Tesch, 1946; Almogi-Labin and Reiss, 1977) , are present and occasionally abundant in the cores, in lower glacial intervals with calculated salinities above 41%0. On the other hand,

67

D. trispinosa, C. inflexa, P. ?moluccensis and S. subula, present in the interglacial stage 5, are absent in the Holocene when salinities were probably similar to those of stage 5. Clio convexa occurs only in the Holocene and in the lower-middle interglacial stage 5 in intervals with 51sO values lighter than 0°/00; this may be due to either lower temperature or higher salinity than at present. Thus, most of the presence/absence pattern of pteropods in the cores cannot be explained by salinity changes only.

This is also true of the abundance pattern of various species. Thus, for example, prominent peaks of L. inflata and L. trochiformis alternate within intervals (stages 3 and 6) with the same calculated temperature and salinity (compare, however, Schoell and Risch, 1976).

Depth relations

At present, the p teropod assemblages in the Gulf of Aqaba are of epipelagic and meso- pelagic nature, despite the 1830 m depth of the Gulf (Almogi-Labin and Reiss, 1977). During glacial stages the assemblages are solely epipelagic, with the exception of middle stage 3 and lower stage 6 (peaks of L. inflata). It is tempting to interpret this change in terms of a considerable glacial drop in sea level. However, the continuity observed in the isotopic and fossil core-records, indicates that the Gulf of Aqaba was permanently connected with the Red Sea through the 252 m Straits of Tiran and that the Red Sea was in turn connected at least through most of glacial times with the Gulf of Aden by the (at present 137 m deep} Straits of Bab-el- Mandeb (Risch, 1976; Reiss et al., 1980). Erosional unconformities vary in extent and stratigraphic position (Reiss et al., 1980). There is also no indication in benthic foraminiferal assemblages of the cores (drilled between 800--1000 m depth) that glacial sea level in the Gulf of Aqaba fell appreciably below the global one. An a t tempt to interpret the very prominent and rapid changes in abundance of L. inflata and L. trochiformis

in upper stage 5 in terms of depth (Chen, 1969) would lead to the conclusion that depth changed drastically several times over a short time interval. According to Chen {1969) L. bulimoides is frequent at times of transi- tion between moderately deep and deep seas. In the cores, L. bulimoides peaks occur in lower stage 5 and at the base of stage 4; such a prominent peak occurs also within the Holocene, when considerable changes in depth of the sea certainly did not occur.

Thus, depth changes of the water column do not explain the exclusively epipelagic nature of the assemblages in glacial stages. An alternative explanation based on changes in the circulation pattern is suggested. Meso- pelagic species, like e.g., L. inflata, S. subula and C. convexa are known to have pro- nounced diel migration (B~ and Gilmer, 1977 and personal observations in the Gulf of Aqaba). Strong stratification of the water column may hamper such migration. The difference in oxygen isotope values between planktonic and benthonic foraminifera in the cores increases considerably during glacial periods (B. Luz, pers. comm., 1981). This points to stronger water column stratification in Glacial times as compared with the Holo- cene or the last Interglacial. Furthermore, benthic foraminiferal assemblages in glacial intervals indicate low-oxygen bo t tom conditions, in contrast to the situation during the Holocene and the last Interglacial (Halicz and Reiss, in press).

The sequences of pteropod assemblages in Red Sea cores have been interpreted with varying emphasis in terms of temperature (see especially Herman, 1968), of salinity (Schoell and Risch, 1976) or of depth {Chen, 1969). As pointed out above, the pteropod assemblages studied in the present work cannot be simply interpreted in these terms. Hitherto little attention has been paid to an important ecological factor, viz. fertility of the sea.

Fertility-determined sequence

At present the Gulf of Aqaba is a moderately oligotrophic environment

68

(Levanon-Spanier et al., 1979). The most abundant (up to 70%) pteropod species living in it is L. inflata, mostly characteristic of gyre centers, although it occurs also frequently in the Somali current (Sakhtivel, 1968, 1973a). This species is dominant in the Holocene and in the last interglacial where it is accompanied by frequent L. bulimoides. In the last interglacial rather frequent S. subula are added. L. bulimoides and S. subula are, like L. inflata, mostly gyre center types, although L. bulimoides is frequent also in the Somali and Brazil currents (Sakhtivel, 1968; B~ and Gilmer, 1977). The latter two species have strong diel migration (B~ and Gilmer, 1977).

L. trochiformis is characteristic of highly productive areas, like boundary currents and upwelling regions (see Fig. 7) and is at present very abundant in the upper 100 m in the Gulf of Aqaba and the northernmost Red Sea during a very short period in autumn, when productivity increases (Levanon-Spanier et al., 1979; personal observations by the author).

The frequency curves of L. trochiformis in the cores are clearly opposite to those of L. inflata (see Figs. 4--5), despite the fact that their temperature and salinity ranges are quite similar. It seems, therefore, that the abundance of L. trochiformis in glacial intervals indicates increased fertility of the waters. Such an increase in fertility during glacial times is also indicated by abundance peaks of the planktonic foraminifera Globigerina bul- loides-falconensis, characteristic of upwelling regions, by the abundance of the benthonic foraminifera belonging to the Buliminidae indicating low oxygen bo t tom conditions related to high productivity of the upper waters (Reiss et al., 1980; Halicz and Reiss, in press), as well as by coccoli thophorid assemblages dominated by Gephyrocapsa oceanica (A. Winter, pers. comm.). The prominent peak of L. inflata in middle stage 3 (also recorded by Herman, 1968 and interpreted by her as due to warming of the sea) may be due to a temporary change in circulation pattern and resulting lower fertility.

The co-occurrence of abundant L. bulimoides with very frequent L. inflata

and L. trochiformis at the base of stage 4, preceeding the important relative increase in L. trochiformis, may suggest that L. bulimoides is intermediate between L. inflata and L. trochiformis as far as productivity of the sea is concerned. In the lower- middle Holocene, L. bulimoides is more abundant in core 73 and 68, i.e. in the northernmost parts of the Gulf of Aqaba and the Red Sea respectively. This may point to stronger upwelling in those times in the northernmost parts of the basins.

The development of increasing arid climate and decreasing fertility of the Red Sea--Gulf of Aqaba (as well as of the Eastern Mediter- ranean) during the Late Holocene may have led to the near-disappearance of L. bulimoides from this region (see Pastouret, 1970; Mfiller et al., 1975; Luz, 1979; Gat and Magaritz, 1980).

Diacria trispinosa, Cavolinia inflexa and Styliola suOula are characteristic of isotope stage 5 and they are all absent from the core record since the late isotope stage 4. (The same is true of Neogloboquadrina pachy- derma (left-coiling).) All three pteropod species mentioned are absent from the present-day northern Arabian Sea (Stubbings, 1938; Frontier, 1963a,b; Sakthivel, 1968, 1973b). As far as S. subula is concerned, Sakthivel (1973b) suggested that its absence in that area is due to the very low oxygen content of the waters below the thermo- cline. Possibly this barrier was established already at the beginning of isotope stage 4.

The "neri thic" Creseis acicula (Frontier, 1973; Rot tman, 1976, 1980; B~ and Gilmer, 1977) is regarded as the most euryhaline and eurythermal pteropod species and is known to occur in seasonal dense swarms associated with high zooplankton productivity as well as with nitrogen-fixing Trichodesmium blooms (Peter and Paulinose, 1978). The abundance of this species in the glacial maxima (stages 6 and 2) and its association with rich diatom floras in stage 2 of core 68, indicate both highly saline and strongly fertile waters. [Chen (1969) suggested that abundance of C. acicula reflects very low sea level.]

69

C. virgula virgula is regarded in general as an oceanic, stenohaline (33--37%) and steno- thermal epipelagic species (Chen and B6, 1964; Rot tman, 1976, 1980; B6 and Gilmer, 1977). On the other hand, this species occurs at present in the hypersaline water column of the Gulf of Aqaba.

The association of abundant Creseis virgula virgula with frequent L. trochiformis on one hand and with C. acicula on the other in glacial stages is strongly suggestive of salinity and fertility of the sea as determining factors.

The trends of the ratios L. inflata/L, trochiformis and of Creseis spp./L, inflata are opposite (Figs. 4--5) and reflect environ- mental changes mainly in fertility and salinity.

Although Clio convexa is generally considered characteristic of equatorial productive waters (B6 and Gilmer, 1977; Rot tman, 1980) this species lives at present in the moderately oligotrophic Gulf of Aqaba at depths down to at least 600 m. It is present mostly during the short winter, when productivity is relatively high, especially in the southern basin of the Gulf (Almogi-Labin, unpubl.; see also Levanon-Spanier et al., 1979). C. convexa occurs in the cores in the lower interglacial stage 5 and in the middle of postglacial stage 1 when conditions were similar, but not identical to the present (see also discussion of L. bulimoides).

Conclusions

(1) The quantitative distribution of p teropod species facilitates a detailed stratigraphic subdivision and precise correlation of the Gulf of Aqaba--Red Sea core sequences. The biostratigraphic intervals recognized by pteropods can be related to the generalized oxygen isotope curve and, therefore, dated beyond the radiocarbon range.

(2) Available evidence from the present-day Gulf of Aqaba and from the assemblage sequences in the cores examined indicates that -- at least in marginal seas -- productivity of the water is a highly important ecological factor which (in addition to temperature, salinity and depth) affects

distribution of pteropods in space and time. (3) Generally, most of interglacial isotope

stage 5 is characterized by oligotrophic assemblages living in weakly stratified waters with temperatures and salinity similar to the present day Gulf of Aqaba. The upper part of stage 5 seems to reflect higher productivity of the whole water column (Fig. 8).

(4) During glacial times the waters of the Gulf of Aqaba were somewhat cooler, more highly saline, well-stratified and more productive than at present. The glacial maxima are characterized by strongly metahaline and highly productive conditions. Within glacial stage 6 a development from low productive to high productive conditions is indicated. During early stage 4 times conditions were slightly less fertile and less stratified than in later glacial times. In middle stage 3 (about 45,000--35,000 yr B.P.) a short, less than 5000 yr episode of possibly more oligotrophic and less stratified conditions are apparent.

(5) The Holocene pteropod assemblages generally reflect conditions similar to the present-day oligotrophic Gulf of Aqaba, although in the middle Holocene (between about 8000 and 3000 yr B.P.) a short period of slightly higher productivity may be connected with temporarily increased humidity in the area.

Acknowledgements

This work is part of a Ph.D. thesis at the Dept. of Geology, The Hebrew University of Jerusalem, under the supervision of Z. Reiss. Financial support was provided by USA-Israel Binational Science Foundat ion grant no. 1762/78 to Z. Reiss, by NSF grant OCE 7681488 to Woods Hole Oceanographic Institution, and by grant No. 015.7138 (to Z. Reiss and B. Luz) by the Israel Ministry of Energy and Infrastructure. Thanks are due to R. Appelman for preparation of samples and to the staff of the SEM unit of the Hebrew University of Jerusalem for assistance with electron-microscopy. Fruitful discussions were held with B. Luz, Y. Erez, A. Winter and

70

a._ GENERALIZED ISOTOPE m CURVE AND STAGES >-

if3 O_ Hiqh ~ 180 Low

0

5 £ -

IO0

150

E N V I R O N M E N T

PTEROPODA

~ ] ]~ ~.~-'~" s ali n ity - 41 °/o° ": temperature 21- 26°C

i salinity >50%0 temperature 14-17°C

. . . . . . . . . . . . . • - #

/ r .

/ similar to Holocene I / /

- - similar to isotope stage 2

~ j similar to isotope stage 5

oligotrophic, well- mixed

highly productive

salinity > 41%o productive ,well stratified temp.<17°C min.winter temp. episode of less stratified and less productive water=

salinity >41 °~o productive ,well stratified temp.<17°C min.winter temp,

transitional changes in productivity

]To

lib

l]I

IV

......... C ac/cula - -- C.w)~gula v/~'gula ~]~ L. buhmo/~es .... L. mflato , L. troch/form/s

Fig. 8. Summary of paleoceanographic changes in the Gulf of Aqaba and northernmost Red Sea during the Late Quaternary as indicated by pteropods and oxygen isotopes.

E. Halicz, of the Hebrew University, Institute of Earth Sciences. S. Honjo (WHOI) and A. Matthews (Hebrew Univ.) critically reviewed the manuscript.

References

Almogi-Labin, A. and Reiss, Z., 1977. Quaternary Pteropods from Israel. Rev. Esp. Micropaleontol., 9: 5--48.

B~, A.W.H. and Gilmer, R.W., 1977. A Zoogeographic and Taxonomic Review of Euthecosomatous Pteropoda. In: A.T. Ramsay (Editor), Oceanic Micropaleontology. Academic Press, London, pp. 733--808.

Berggren, W.A. and Boersma, A., 1969. Late Pleisto- cene and Holocene planktonic foraminifera from the Red Sea. In: E.T. Degens and D.A. Ross (Editors), Hot Brines and Recent Heavy Metal Deposits in the Red Sea. Springer, Berlin, pp. 282--298•

Boas, J.E.V., 1886. Spolia Atlantica. Bidrag til Pteropodernes. Morfologi og systematik saint til kundskaben am deres geografiske unbredelse. Vidensk. Selsk. Skr., 6. Raekke Naturvid. Math., IV( l ) : 1--231.

Chen, C., 1969. Pteropods in the Hot Brines Sedi- ments of the Red Sea. In: E.T. Degens and D.A. Ross (Editors), Hot Brines and Recent Heavy Metal Deposits in the Red Sea. Springer, Berlin, pp. 313--316.

Chen, C. and B~, A.W.H., 1964. Seasonal Distribution

71

of Euthecosomatous Pteropods in the Surface Waters of five Stations in the Western North Atlantic. Bull. Mar. Sci. Gulf Caribb., 14(2): 185--220.

Degens, E.T. and Ross, D.A. (Editors), 1969. Hot Brines and Recent Heavy Metal Deposits in the Red Sea. Springer, Berlin, 600 pp.

Frontier, S., 1963a. Zooplancton recolt~ en met d'Arabie, Golfe Persique et Golf D'Aden. II. Pt~ropodes: Systematique et repartition. Cah. ORSTOM, S~r. Oc~anogr., 6: 233--254.

Frontier, S., 1963b. Presence de Creseis chierchiae (Boas) dans l'Ocdan Indian. Cah. ORSTOM, S~r. Oc~anogr., 6: 229--232.

Frontier, S., 1965. Le probl~me des Creseis. Cah. ORSTOM, S~r. Oc~anogr., 3(2): 11--18.

Frontier, S., 1973. Zooplancton de la r~gion de Nosy- B~. VI. Pt~ropodes, H~teropodes. Premiere partie: esp(~ces holon~ritiques et n~ritiques-internes (Con- tribution ~ l '~tude d'une bale eutrophique tropical). Cah. ORSTOM, S~r. Ocdanogr., 11(3): 273--289.

Gat, J.R. and Magaritz, M., 1980. Climatic Variations in the Eastern Mediterranean Sea Area. Natur- wissenschaften, 67 : 80--87.

Halicz, E. and Reiss, Z., in press. Paleoecological relations of Foraminifera in a desert-enclosed sea -- the Gulf of Aqaba (Elat), Red Sea. Mar. Ecol.

Hall, J. and Ben-Avraham, Z., 1978. New bathymetric map of the Gulf of Elat (Aqaba). Tenth Int. Congr. Sedimentology, Abstr., 1: 285.

Herman, Y., 1968. Evidence of climatic changes in Red Sea cores. In: Means of Correlations of Quaternary Successions, Congr. Int. Assoc. Quater- nary Research, 8(VII): 325--348.

Klinker, J., Reiss, Z., Kropach, C., Levanon, I., Harpaz, H., Halicz, E. and Assaf, G., 1976. Obser- vations on the Circulation Pattern in the Gulf of Elat (Aqaba), Red Sea. Isr. J. Earth-Sci., 25: 85--103.

Klinker, J., Reiss, Z., Kropach, C., Levanon, I., Harpaz, H. and Shapiro, Y., 1978. Nutrients and Biomass Distribution in the Gulf of Aqaba (Elat), Red Sea. Mar. Biol., 45: 53--64.

Levanon-Spanier, I., Padan, E. and Reiss, Z., 1979. Primary production in a desert-enclosed sea - - t h e Gulf of Elat (Aqaba), Red Sea. Deep-Sea Res., 26: 673--685.

Luz, B., 1979. Palaeo-oceanography of the postglacial Eastern Mediterranean. Nature, 278: 847--848.

McIntyre, A., 1969. The coccolithophorida in Red Sea sediments. In: E.T. Degens and D.A. Ross (Editors), Hot Brines and Recent Heavy Metal Deposits in the Red Sea. Springer, Berlin, pp. 299--305.

Muller, C., Blanc-Vernet, L. and Chamley, M., 1975. Les Coccolitophorides d 'une carotte M~diterran~- enne, comparison pal~oclimatologique avec les

Foraminif~res, les Pt~ropodes et les Argiles. Tethys, 6(4): 805--828.

Paldor, N. and Anati, D.A., 1979. Seasonal variations of temperature and salinity in the Gulf of Elat (Aqaba). Deep-Sea Res., 26(6A): 661--672.

Pastouret, L., 1970. Etude S~dimentologique et Pal~oclimatique de carottes pr~lev(ies en M~diter- range Orientale. Tethys, 2(1): 227--266.

Pelseneer, P., 1888. Report on the Pteropods collected by H.M.S. "Challenger" during the years 1873--1876. II. The Thecosomata. Rep. Sci. Res. Voy. "Challenger" Zool., 23 (65) : 1--132.

Peter, K.J. and Paulinose, V.T., 1978. Swarming of Creseis acicula Rang (Pteropoda) in the Bay of Bengal. Indian J. Mar. Sci., 7(2): 126--127.

Por, F.D., 1978. Lessepsian Migration. The Influx of Red Sea Biota into the Mediterranean by Way of the Suez Canal. Springer, Berlin, 228 pp.

Rampal, J., 1975. Les Th~cosomes (Mollusques pela- giques). Syst~matique et Evolution -- Ecologie et Biog~ographie M~diterran~ennes. Thesis, Universi- t~ de Provence, Marseille, 485 pp.

Reiss, Z., Luz, B., Almogi-Labin, A., Halicz, E., Winter, A., Wolf, M. and Ross, D.A., 1980. Late Quaternary Paleoceanography of the Gulf of Aqaba (Elat), Red Sea. Quaternary Res., 14: 294--308.

Risch, H., 1976. Microbiostratigraphy of Core- Sections of the Red Sea. Geol. Jahrb., D17: 2--14.

Rosenberg-Herman, Y., 1965. Etudes des s~diments quaternaires de la Mer Rouge. Thesis, University of Paris, Paris, A(1123), pp. 339--430.

Rottman, M.L., 1976. Euthecosomatous pteropods (mollusca) in the Gulf of Thailand and the South China Sea: seasonal distribution and species associations. Naga Rep., 4(6): 1--117.

Rottman, M.L., 1977. Euthecosomatous Pteropods and Planktonic Foraminifera in Southeast Asian Marine Waters: Species Associations and Distribu- tion in Sediments. Dissertation, University of Colorado, Boulder, Colo., 235 pp.

Rottman, M.L., 1978. Ecology of recurrent groups of pteropods euphausiids, and chaetognaths in the Gulf of Thailand and the South China Sea. Mar. Biol., 48: 63--78.

Rottman, M.L., 1980. Net tow and surface sediment distribution of pteropods in the South China Sea region: comparison and oceanographic implica- tions. Mar. Micropaleontol., 5 : 71--110.

Sakthivel, M., 1968. A preliminary report on the distribution and relative abundance of Eutheco- somata with a note on the seasonal variation of Limacina species in the Indian Ocean. Bull. Nat. Inst. Sci. India, 38: 700--717.

Sakthivel, M., ]973a. Studies on Limacina inflata d'Orbigny (Thecosomata, Gastropoda) in the Indian Ocean. In: B. Zeitzschel and S.A. Gerlach (Editors), The Biology of the Indian Ocean. Springer, Berlin, pp. 383--397.

72

Sakthivel, M., 1973b. Biogeographical change in the latitudinal boundary of a bisubtropical pteropod Styliola subula (Quoy et Gaimard) in the Indian Ocean. In: B. Zeitzschel and S.A. Gerlach (Editors), The Biology of the Indian Ocean. Springer, Berlin, pp. 401--404.

Schoell, M. and Risch, H., 1976. Oxygen-and Carbon- Isotope Analyses on Planktonic Foraminifera of Core VA 01-188P (Southern Red Sea). Geol.

Jahrb., D17: 15--32. Stubbings, H.G., 1938. Pteropoda. The John Murray

Exp. 1933--1934. Sci. Rep. 5(2): 3--33. Tesch, J.J., 1946. The thecosomatous pteropods. I.

The Atlantic. Dana Rep., 28: 1--82. Von Daniels, C.H., 1970. Quantitative 5kologische

Analyse der zeitlichen und r//umlichen Verteilung rezenter Foraminiferen im Limski Kanal bei Roving. G6ttinger Arb. Geol. Pal~/ontol., 8.

Documents

Stratigraphic and paleoceanographic significance of Late Quaternary pteropods from deep-sea cores in the Gulf of Aqaba (Elat) and northernmost Red Sea