Journal of African Earth Sciences 38 (2004) 169–181

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Palaeoenvironment of the Acheulian Gesher Benot Ya’aqovPleistocene lacustrine strata, Northern Israel––lithology,ostracod assemblages and ostracod shell geochemistry

A. Rosenfeld a,*, Y. Nathan a, C.S. Feibel b, B. Schilman a, L. Halicz a,N. Goren-Inbar c, R. Siman-Tov a

a Geological Survey of Israel, 30 Malkhe Yisrael Street, 95501 Jerusalem, Israelb Department of Anthropology and Geological Sciences, Rutgers University, New Brunswick, NJ 08901, USA

c Institute of Archeology, Hebrew University, 91240 Jerusalem, Israel

Received 23 July 2003; accepted 31 October 2003

Abstract

The Acheulian archaeological site Gesher Benot Ya’aqov (GBY) is located along the shoreline of a Pleistocene Lake, the GBY

Lake, within the Jordan Rift valley. The uniqueness of the site is expressed in its complex sedimentary sequence, rich fossil

assemblages, and in the first appearance of lithic technologies not previously seen in Eurasia. The site is reliably dated at the

Matuyama–Brunhes geomagnetic polarity chron boundary (�780 kA), which occurs within the lake sediments.

The sedimentary sequence at GBY exhibits a pronounced cyclicity. A single first order cycle begins with a lower conglomerate

followed by lacustrine beds, overlain by an upper conglomerate that closes the cycle. Second-order cyclicity is apparent in shifts

from littoral to deeper water facies, with five such cycles, identified within the first order cycle. The diatom and ostracod distri-

butions indicate a freshwater–oligohaline environment of deposition for the lower part of the section and oligohaline–meio-meso-

haline waters in the upper part of the section. In addition, the C and O isotopes and the Sr/Ca and Mg/Ca ratios of the ostracod

(Candona neglecta) shells exhibit three geochemical zones supporting the paleoecological biozonation. They reflect a cooler period

for the lower part of the sequence (interval I), changing into warmer climate at the Matuyama–Brunhes boundary and upward

(interval II). Further gradual temperature increase in the upper interval III caused the retraction and desiccation of the GBY Lake.

� 2003 Elsevier Ltd. All rights reserved.

1. Introduction

The Acheulian archaeological site of Gesher Benot

Ya’aqov (GBY) is located along the Jordan River (Fig.

1) in the northern part of the African-Syrian Rift Sys-

tem. It is situated within a narrow north–south oriented

valley at the southeastern end of the Hula Basin (Fig. 1),

in northern Galilee, Israel (33�0003000N, 35�3703000

E).GBY has been known for its artefacts and fossils since

1934 (Stekelis et al., 1937; Stekelis, 1960) and documents

hominid activities along the margins of this palaeo-Hula

Lake. The GBY palaeo-lake is one of a series of lakes,

which existed in the Hula Basin, the northern extension

of the Dead Sea Rift Valley. Excavations undertaken

* Corresponding author.

E-mail address: y.nathan@mail.gsi.gov.il (A. Rosenfeld).

0899-5362/$ - see front matter � 2003 Elsevier Ltd. All rights reserved.

doi:10.1016/j.jafrearsci.2003.10.008

in 1989–1997 south of the Benot Ya’aqov bridge

(southern margins of the GBY Lake) recovered a rich

assemblage of lithic artefacts and vertebrate fossils

(Goren-Inbar and Belitzky, 1989; Goren-Inbar et al.,

1992). In addition, the site contains unusually well pre-

served organic remains such as fossil wood, seeds, fruits

and pollen. The uniqueness of the site is reflected in

the complex sedimentary sequence, rich fossil record, alithic artefact assemblage and a boundary, between

magnetic polarity zones, which was correlated with the

Matuyama–Bruhnes chron boundary (Goren-Inbar

et al., 2000). This marks the movement of early hominid

technologies out of Africa around 780 kA (date of

the Matuyama–Bruhnes chron boundary). During the

recent excavations, geological work on the stratigraphy

and sedimentology of the site was accompanied bysystematic sampling of the sequence for microfossil

remains.

Fig. 1. Location map.

170 A. Rosenfeld et al. / Journal of African Earth Sciences 38 (2004) 169–181

Non-marine ostracods have been used extensively as

proxy indicators of palaeosalinities, palaeotemperatures

and lacustrine palaeoenvironments (e.g., Chivas et al.,

1985, 1986; De Deckker and Forester, 1988; Holmes and

Horne, 1999). The aim of this study is the reconstruction

of the palaeoenvironments within the palaeo-GBY Lake

during the time of the early hominid occupation. We

report here on a detailed analysis of the fossil ostracodfaunas from GBY and their geochemical signatures as

well as supporting data from sedimentological studies

and diatom analysis.

One of our aims is to contribute data on the associ-

ation between the hominids and lake-margin environ-

ments. A detailed reconstruction of the lake properties

could add much to the understanding of a well-known

phenomenon of repetitive Palaeolithic occupationsalong lake shores that are known from Africa and

Eurasia. The site of GBY, one of the few documented in

the Levant, attests to the fact that the ‘‘Levantine cor-

ridor’’ was a unique ecological niche, which provided

areas rich in resources and was supportive of the

Acheulian hominid mode of living.

2. Geological setting

2.1. General

The Hula Basin and the Jordan Valley are the

northern extension of the Dead Sea–Red Sea–East

African Rift System (Fig. 1). The Rift in the Levant

represents a north–south trending depressed morpho-structure that constitutes a natural passageway between

Africa and Eurasia. Subsidence in the Hula Basin began

in the late Neogene, and continues to the present

(Horowitz and Horowitz, 1985). Freshwater lakes and

marshes have existed more or less continuously within

the basin, and their sediments are locally interstratified

with basalt flows. Late Quaternary to Recent sediments

of the Hula Lake have been the subject of numerousinvestigations (e.g., Cowgill, 1969, 1973, 1994; Racek,

1974; Kafri and Lang, 1987). The chemical and isotopic

composition of gastropod shells has been used to

reconstruct the environments of deposition of Quater-

nary freshwater lakes in the area (Rosenthal et al., 1989;

Moshkovitz and Magaritz, 1987).

A. Rosenfeld et al. / Journal of African Earth Sciences 38 (2004) 169–181 171

At GBY, Quaternary strata are exposed along bothbanks of the Jordan River. Faulting and folding asso-

ciated with the left-lateral Dead Sea Transform have

deformed those sediments (Goren-Inbar and Belitzky,

1989) tilting strata up to 45�. Exposures in the vicinity of

the site include four different Pleistocene formations

(Horowitz, 1973), along with at least two basalt flows.

2.2. Sedimentology

The Pleistocene littoral sediments exposed in exca-

vations at the GBY site (southern margins of the GBY

Lake), are part of the Benot Ya’aqov Formation

(Horowitz, 1973). They comprise some 35 m of inter-

bedded calcareous muds, coquinas and gravels (Figs. 2

and 3). The sediments reflect deposition along the lit-

toral zone of the GBY Lake (one of the Hula palaeo-

lakes); both subaerial and subaqueous deposits arepresent, reflecting lake-level fluctuations along the

palaeo-shoreline.

Subaerial components include both channel facies

and palaeosols. At low lake levels, gravel-bed streams

trangressed the site. They deposited basalt boulder to

cobble-conglomerates in tabular sheets. The matrix of

the clast-supported conglomerates is a hash of frag-

mented molluscs and sand, indicating close proximity tothe lake margin at the time of deposition. These con-

glomerates are prominent at the base and top of the

section exposed at the site. Scattered boulders are also

associated with most of the lake margin sands and

coquinas (shell beds), possibly introduced to the site by

flash floods. The fine-grained lacustrine facies are

Fig. 2. Stratigraphic sections of GBY (trenches). The figure shows the corr

obtain the composite section (Fig. 3).

punctuated by several pedogenic profiles, documentingsoil development during brief desiccation events. All

other facies reflect deposition in beach and shallow

water environments.

The lacustrine facies document deposition in two

broad settings: the higher energy strand line and the low

energy offshore environment. Molluscan coquinas and

pebbly sands are characteristic of the lake margin set-

ting, and it is this facies association which preserves thebulk of the stone tool, and fossil vertebrate remains. The

high-energy deposits appear to be dominated by accre-

tion during storm events (Feibel, 2001). In these

deposits, tabular beds of 10–20 cm thickness occur,

often with few or no internal primary structures.

Archaeological accumulations are concentrated at the

interfaces between such depositional units, while few

stone tools or bones occur within them. Thus the unitsthemselves are interpreted to reflect short-term (storm)

event stratification, while the interfaces between them

reflect depositional hiatuses over which accumulation of

stone-tool discard and fossil bone occurred. Deposits of

the low-energy offshore settings are predominantly

marls (54–68% CaCO3) with a well-preserved organic

component (3–21% OM) with only a minor detrital

contribution. These marls occur in thick packages (1–5m), but internally show a high degree of variability in

particle size, carbonate content and organic matter,

reflecting local and short-term variability in the char-

acter of aquatic vegetation, currents, oxygenation and

other parameters.

The lacustrine sediments contain a rich and varied

assemblage of aquatic invertebrates (molluscs, ostracods,

elations between the beds in the various trenches which were used to

Fig. 3. Composite section at GBY, showing the lithology; the Matuyama–Brunhes geomagnetic boundary; the sedimentological cycles; the

occurrence of the Acheulian artefacts; the trends of the d18O, d13C, Sr/Ca and Mg/Ca ratios for Candona neglecta valves as well as the ostracod

population density, biozones and palaeosalinity.

172 A. Rosenfeld et al. / Journal of African Earth Sciences 38 (2004) 169–181

charophytes, and diatoms). Two types of carbonate mud

are present: organic matter-rich (12–21% OM) and or-

ganic matter-poor (3–8% OM). The organic matter-rich

carbonate muds reflect deposits in low-energy poorlyoxygenated settings, and are generally grey to greyish-

brown. Other than ostracods, they are relatively impov-

erished in calcareous fossils. All the carbonate of this type

of mud is calcite; the endogenic calcite in this type of mud

originates from ostracod valves. Nearly all the sediments

with abundant ostracod faunas are of this type of car-

bonate mud (organic-rich). The organic-poor carbonate

muds, deposited in high-energy open circulating waterssettings, are brown to dark grayish brown. They are rich

in gastropod shells and poor in ostracods. The carbonate

of this type of mud is mostly calcite but contains signifi-

cant amounts of aragonite (gastropod shells). The dif-

ferences between the two types of muds are probably due

to the different environment of deposition, most of the

OM is oxidized in the high-energy settings. The organic

matter-poor, carbonate muds grade into molluscan sandsand coquinas (shell-beds) in which carbonate content

may exceed 90%. These however tend to be poor in os-

tracods, probably because they are largely wave sorted

and wave deposited sediments.

2.3. Age

The sedimentary sequence at GBY lies above the

Yarda Basalt, which has been dated at �900 kA (Hei-

man et al., 1987; Goren-Inbar et al., 1992). A magnetic

polarity transition within the sequence (Fig. 3) is cor-

related with the Matuyama–Brunhes geomagnetic

polarity chron boundary at �780 kA (Bassinot et al.,

1994; Tauxe et al., 1996; Verosub et al., 1998; Goren-

Inbar et al., 2000). The sequence exhibits a pronounced

cyclicity in sedimentary character. A single first-ordercycle begins with the lower conglomerate followed by

lacustrine beds and closes with the upper conglomerate.

This cycle is shown in the composite stratigraphic

sequence (Fig. 3). Second-order cyclicity is apparent in

shifts from littoral to offshore facies, with five such

cycles found within the larger pattern. The magnitude,

character and relationships of these signals have been

interpreted to represent climatic forcing of lake levelfluctuations at the Milankovitch periodicities of roughly

20 and 100 kA (Feibel et al., 1998). This is supported

by the age of the Yarda Basalt (Heiman et al., 1987) and

the detailed analysis of the magnetic characteristics of

the sediments (Verosub et al., 1998, 1999; Goren-Inbar

et al., 2000), which suggest a span of slightly less than

100–150 kA for a 24 m segment of the composite sec-

tion. The combination of cyclostratigraphy and thechron boundary allow direct correlations of the GBY

sequence to oscillations in and around marine Oxygen

Isotope Stage 19.

3. Samples and methods

The samples were obtained from six trenches, whose

locations are given in Goren-Inbar et al. (2000). Fig. 2illustrates the stratigraphic sections of the six trenches,

and their correlation is the basis of the composite

stratigraphic section (Fig. 3). The correlation of the

A. Rosenfeld et al. / Journal of African Earth Sciences 38 (2004) 169–181 173

various trenches was made on the basis of a magneto-stratigraphic study of 155 oriented samples from tren-

ches II–VI (Goren-Inbar et al., 2000). Fig. 3 shows the

position of the second-order cycles, the position of

the Matuyama–Brunhes boundary and the lithology.

The dominance of coarser lithologies at certain levels,

made up mainly of gastropods (Melanopsis sp., Vivipa-

rus sp.) and their debris, resulted in minor gaps in rep-

resentation. More than forty samples (from TrenchesVI, II and III, Table 1) were examined for ostracods.

Only twenty-seven contained enough ostracods to carry

out geochemical analyses. Relatively large samples of

sediment (up to 500 g) had to be washed to obtain en-

ough material (ostracods) for the palaeontological and

geochemical analyses.

All the geochemical analyses were performed at the

Geological Survey of Israel. Only adult specimens of theostracod Candona neglecta were employed in the geo-

chemical study. This species was chosen because of its

abundance in the samples and because of the detailed

experimental studies of Xia et al. (1997a,b) on a species

of the same genus (Candona rawsoni). The shell chem-

istry of Candona species has already been used for a

similar palaeoenvironmental reconstruction (Anadon

et al., 1994). Ostracod valves for the geochemical studywere hand-picked from the sieved separates, and special

care was taken to avoid contamination. A non-metallic

brush was used for picking the ostracods into the ana-

lyzed tubes to avoid metallic contamination. The os-

tracods were washed twice with double de-ionized water,

and then dissolved in ultra-pure dilute hydrochloric

acid. Sr, Ca and Mg concentrations were determined by

ICP-MS (Perkin Elmer, Sciex Elan 6000). Blanks resultswere lower than the detection limit, and the results of

one sample analyzed in triplicate were within a 10%

range. All results were obtained as ratios to avoid errors

due to weighing very small samples.

Sixteen oxygen and carbon isotopic measurements of

the ostracod species (Candona neglecta) were done on a

VG ISOCARB system coupled to a SIRA-II mass-

spectrometer, according to the method of Shackleton(1974). In the Isocarb, the samples (five to eight adult

valves each) were reacted successively under vacuum in

a reservoir of �100% orthophosphoric acid (H3PO4) at

90 �C. Calibration of the mass spectrometer to the

international PDB Vienna (Pee Dee Belemnite) car-

bonate standard was done through the National Bureau

of Standards (NBS) 9, following Coplen (1988).

Instrument precision was better than ±0.1& for bothd13C and d18O values, and the external reproducibility

based on duplicate measurements of reference standard

was 6 0.05&.

Thirty samples (from Trenches II–IV) were examined

for diatoms. Only two samples yielded a few diatoms.

For diatom analyses the samples were treated with HCl

and H2O2 through the standard procedure, with re-

peated washing in distilled water. Slides were preparedby using Naphrax high resolution mounting medium.

Fifteen bulk samples were examined by XRD, with a

Philips PW-1820/00 diffractometer and Cu Ka radiation

using a curved graphic monochromator. This was done

mainly to identify the CaCO3 polymorph present in the

samples (calcite or aragonite).

4. Results

4.1. Ostracods

The photographs of 10 ostracod species together with

the algae Chara are shown in Plate 1. To describe water

salinity we follow Wagner (1957, p. 108) who used the

Valikangas (1933) classification: Freshwater up to 0.5&;oligohaline water 0.5–3&; meio-mesohaline water 3–

10&; pleio-mesohaline 10–16.5&. Euryhaline describes

a species which has a tolerance for a rather wide range of

salinity.

4.1.1. Brief taxonomy and ecology

Cytheromorpha fuscata (Brady, 1868), (Plate 1, Figs.

12–14) is known to dwell only in an oligohaline–

mesohaline environment (Elofson, 1969), probably 0.6–

17&, in water depth of 0–30 m.

Heterocypris salina (Brady, 1868) (Plate 1, Fig. 15).

This species habitat is uniquely in an oligo–mesohalinewater environment, from 0.5& to 13& (Neale, 1964;

Henderson, 1990).

Ilyocypris gibba (Ramdohr, 1808) (Plate 1, Fig. 7)

lives in a freshwater to oligohaline environment of

deposition from 0.1& to 0.8& (Neale, 1964), in shallow

lakes and streams.

Ilyocypris bradyi (Sars, 1890) (Plate 1, Fig. 8) prefers

to live in cooler waters and is found in permanentstreams. It lives in freshwater to slightly mesohaline

water (Henderson, 1990).

Cyprideis torosa (Jones, 1850) is euryhaline and can

tolerate all the salinity range from fresh-water to

hypersaline, from 0.2& to 80&, in water depth of 0–30

m (Rosenfeld and Vesper, 1977).

Candona neglecta (Sars, 1887) (Plate 1, Figs. 1–3)

lives in freshwater to oligohaline environments of softand muddy sediments. The species is able to survive even

in places where water dries out (Wagner, 1957). This

species dominates (high population density) the whole

section. This is the main reason why this species was

chosen for geochemical (trace elements and stable iso-

topes) analyses.

Candona compressa (Koch, 1838) (Plate 1, Fig. 4)

generally inhabits freshwater to oligohaline environ-ments (up to 1&, Neale, 1964).

Candona angulata (Mueller, 1900) (Plate 1, Fig. 5)

dwells in freshwater to mesohaline water. According to

Table 1

Ostracod distribution and population density

Year/

sample

no.

Trench-

layer

Depth

(m)

Cypri-

deis

torosa

Candona

neglecta

Ilyocy-

pris

gibba

Ilocypris

bradyi

Candona

angulata

Darwinula

stevensoni

Dolero-

cypris

sp.

Cythero-

morpha

fuscata

Candona

com-

pressa

Hetero-

cypris

salina

Ilyocy-

pris sp.

Total

speci-

mens

Ostracod

biozones

Palaeo-

environment

96/201 VI-2 6.4 72� 9 3 7 2 93 2B Oligo-

haline–

mesohaline

203 VI-4 7.0 95 6 11 1 13 126

204 VI-4 8.0 10 2 4 16

205 VI-4 8.7 92 2 11 10 115

206 VI-5 9.3 11 1 1 13

207 VI-6 9.5 28 2 1 9 2 42

208 VI-7 9.8 65 3 5 14 8 2 97

209 VI-8 10.4 1 1

210 VI-9 11.0 2 3 10 15

211 VI-10 11.7 10 2 18 30

96/213 VI-12 13.0 3 3 5 10 9 30

95/54 II-3 13.2 18 5 1 3 24 4 37

56 II-5 14.0 22 11 2 35 2A

82 II-7 16.6 112 1 1 114

58 II-7 16.7 48 9 57

59 II-8 17.0 3 1 4

60 II-8 17.3 40 5 5 11 61

61 II-9 18.2 95 8 103

63 II-11 19.1 51 5 2 4 62 1 Freshwater–

oligohaline65 II-13 19.9 2 2

67 II-15 20.6 51 51

69 II-17 21.3 360 6 2 6 374

70 III-1 23.2 14 3 2 19

72 III-3 24.6 5 5

75 III-6 27.4 6 1 7

77 III-8 30.8 1 4 1 6

78 III-9 31.0 15 1 16

95/79 III-10 31.3 2 2

*Number of specimens per 350 g of sediment sample.

174

A.Rosen

feldet

al./JournalofAfrica

nEarth

Scien

ces38(2004)169–181

Plate 1. Pleistocene ostracod species from GBY, northern Israel. Figs. 1–3: Candona neglecta; 1––Female carapace, right valve view; GBY-96/203;

2––Instar, left valve; GBY-95/56; 3––Male carapace, right valve view; GBY-96/203. Fig. 4: Candona compressa; Right valve; GBY-95/67. Fig. 5:

Candona angulata; Male left valve; GBY-96/213. Fig. 6: Darwinula stevensoni; Carapace, right valve view; GBY-96/203. Fig. 7: Ilyocypris gibba; Right

valve; GBY-95/56. Fig. 8: Ilyocypris bradyi; Right valve; GBY-96/201. Fig. 9: Ilyocypris sp.; Right valve; GBY-96/201. Fig. 10: Chara sp.; Algae;

GBY-95/67. Fig. 11: Dolerocypris sp.; Carapace, right valve view; GBY-96/203. Figs. 12–14: Cytheromorpha fuscata; 12––Carapace, left valve view;

GBY-95-61; 13––Right valve; GBY-95-61; 14––Left valve; GBY-95/60. Fig. 15: Heterocypris salina; Right valve; GBY-95/85.

A. Rosenfeld et al. / Journal of African Earth Sciences 38 (2004) 169–181 175

De Deckker (1979) this species was found in waters with

a salinity up to 13.4&.

Darwinula stevensoni (Brady & Robertson, 1870)

(Plate 1, Fig. 6) lives in freshwater–oligohaline waters

with a salinity of up to 0.75& (Henderson, 1990). This

species is found in shallow waters; in Gull Lake, Michi-

gan it reached a maximum population density at a depth

of 6 m and no specimens were found at depths greaterthan 12 m (McGregor, 1969).

Dolerocypris sp. (Plate 1, Fig. 11). Species of this

genus usually live in shallow freshwater to oligohaline

environments (Henderson, 1990).

4.1.2. Ostracod distribution

The distribution and population density of ostracods

(number of ostracods found in 350 g sample) are given

in Table 1. Eleven species were determined. Two species

are rare. Only one adult valve of Cyprideis torosa was

found in the lower part of the section and it was prob-

ably transported. Only two specimens of Ilyocypris

bradyi were found in one layer near the top of thesection. Seven other species known to live in freshwater

to oligohaline–mesohaline waters were found. In GBY,

only two species can be used to characterize the oligo-

haline–mesohaline waters, Cytheromorpha fuscata and

176 A. Rosenfeld et al. / Journal of African Earth Sciences 38 (2004) 169–181

Heterocypris salina, both occur only in oligo–mesohaline waters; neither occur in freshwater. Both

their presence and absence are significant.

4.2. Diatoms

Two samples only (95/70 and 95/71), both from the

lower part of the section yielded a few diatoms with

relatively very low quantity. Most of the diatom valves

are very badly preserved, as a result of dissolution and/

or of mechanical breakage. Almost all the species were

identified at least to the genus stage mainly based onEhrlich (1995) and Krammer and Lange-Bertalot (1986,

1988, 1991a,b). Table 2 lists almost all the diatom spe-

cies that were found in the two samples and Plate 2

shows photographs of the diatoms.

These two samples yielded apart from diatoms, fish

teeth, gastropods and sponge spicules. Most of the

diatoms belong to the Fragilaria group. The diatom

assemblages of these two samples may be correlated tothe assemblages of the Hula Basin (Ehrlich, 1973):

sample GBY/95/70 to the assemblage of H1 zone and

sample GBY/95/71 to the H4 zone. Both assemblages

Table 2

Diatoms in samples 95/70 and 95/71

Species/sample no. 95/70

Achnanthes sp. Xa

? Achnanthes minutissima X

Amphora cf. libyca –b

? Anomoeoneis sphaerophora –

Aulacoseira cf. ambigua A single va

Aulacoseira cf. granulata X

Cocconeis placentula var. euglypta –

Cocconeis placentula var. lineata X

Cyclotella ? ocellata –

Cymbella cf. aspera –

Ellerbeckia arenaria X

Ephithemia sp. –

Ephithemia adnata –

Ephithemia frickei X

Epithemia turgida –

Eunotia cf. pectinalis –

Fragilaria spp. X

Fragilaria cf. brevistriata X

Fragilaria cf. pinnata X

Fragilaria construens var. construens X

Fragilaria construens var. venter X

? Fragilaria virescens X

Gomphonema sp. –

Gomphonema cf. insigne –

Navicula sp. X

Nitzschia amphibia –

Opephora martyi X

Pinnularia sp. X

Synedra sp. X

Synedra ? ulna –

aX¼present.b –¼Not detected.

indicate a very shallow freshwater, eutrophic, alkalineenvironment.

These two very badly preserved assemblages were

probably the result of breakage by currents and waves

and/or from being biologically ingested and digested.

Molluscs feed mainly on epilithic and epiphytic algae,

hence most of these diatom species, which are also epi-

lithic and epiphytic were probably ingested by molluscs.

4.3. Geochemical analyses

The results of the geochemical analyses are given inTable 3. Fig. 3 shows the trends of the d18O, d13C, andSr/Ca and Mg/Ca ratios along most of the section.

According to these results, the section may be divided

into three parts. I––a lower part in which the Sr/Ca and

Mg/Ca curves exhibit similar trends, while the d13C and

d18O have opposite trends. II––a middle part where the

Sr/Ca and Mg/Ca curves show opposite trends, while the

d13C and d18O have similar trends. III––an upper partwhere the relationships between the curves are not clear.

All the samples analysed by XRD contained appre-

ciable amounts of calcite, with ostracods constituting

95/71

X

–

X

X

lve –

X

X

X

X

X

X

X

X

–

X

X

–

X

–

X

X

–

X

X

X

X

X

X

X

X

Plate 2. Pleistocene diatom species from GBY, northern Israel. Fig. 1: Fragilaria construens var. venter (Ehrnberg) Grunow, 1881. Sample no. GBY-

95-71. Fig. 2: Fragilaria construens var. construens (Ehrnberg) Grunow, 1862 (broken valve). Sample no. GBY-95-70. Fig. 3: Fragilaria construens

var. construens (Ehrnberg) Grunow, 1862. Sample no. GBY-95-70. Fig. 4: Opephora martyi Heribaud, 1902. Sample no. GBY-95-70. Fig. 5:

Fragilaria cf. pinnata Ehrenberg, 1843. Sample no. GBY-95-70. Fig. 6: Cocconeis placentula var. lineata (Ehrenberg) Van Heurck, 1880–1885. Sample

no. GBY-95-70. Fig. 7: Ellerbeckia arenaria (Moore) Crawford, 1988. [The magnification in LM · 1000]. Sample no. GBY-95-70. Fig. 8: Aulacoseira

cf. granulata (Ehrenberg) Simonsen, 1979. Sample no. GBY-95-70. Fig. 9: Chrysophyte cyst. Sample no. GBY-95-71.

A. Rosenfeld et al. / Journal of African Earth Sciences 38 (2004) 169–181 177

most of the endogenic, biogenic component. Aragonite

was identified only in samples, which contained gastro-

pod debris.

5. Discussion and palaeoecology

5.1. Ostracod biozones and population density

According to the ostracod distribution (Table 1), the

two ostracod species Heterocypris salina and Cythero-

morpha fuscata, which do not occur in freshwater, occur

only in the upper part of the section. The ostracod

Cytheromorpha fuscata var. significans that occurs infreshwater (Alm, 1916; quoted by Elofson, 1969, p. 209)

was not found in the GBY samples. All the ostracods

occurring in the lower part of the section can live in

freshwater to oligohaline environments of deposition.

Therefore a division into two parts according to ostra-

cod distribution may be discerned within the GBY sec-

tion: (1) a lower freshwater to oligohaline part up to 3&,

from �19 to 31 m, and (2) an oligohaline to oligohaline–

meio–mesosaline, up to 10&, upper part from �6 to 18

m. This division is a reflection of the first-order cycle, thefreshwater–oligohaline phase marks the beginning of the

lake and the slight increase in salinity is an indication of

a drier climate leading towards the lake desiccation. The

boundary between the freshwater–oligohaline ostracod

zone 1 and the oligohaline–meio–mesohaline zone 2

coincides more or less with the Matuyama–Brunhes

boundary (Fig. 3).

A secondary twofold division may be noticeable in theupper oligohaline–meio–mesohaline biozone 2: a lower

2A zone, with oligohaline waters, from 18 to 13.5 m

Table 3

Geochemistry results trace elements and C and O isotopes of Candona neglecta valves

Sample Layer Depth (m) Ca (ppm)a Mg (ppb)a Sr (ppb)a Sr/

Cab · 10�3

Sr/Mgb Mg/

Cab · 10�2

d13C &

PDB

d18O &

PDB

96/201 VI-2 6.4 2.406 9.82 2.13 0.406 0.060 0.673 )3.03 )5.2896/203 VI-4 7.0 2.752 8.57 2.39 0.397 0.077 0.514 +3.62 )5.0896/204 VI-4 8.0 4.521 13.10 3.93 0.398 0.833 0.478 )5.57 )4.5796/205 VI-4 8.7 1.216 4.83 1.25 0.471 0.072 0.656 )5.20 )4.7196/208 VI-7 9.8 11.142 28.44 12.02 0.494 0.117 0.421 )4.05 )4.7396/211 VI-10 11.7 2.697 11.73 2.27 0.385 0.054 0.718 )8.58 )4.9896/213 VI-12 13.0 3.038 86.98 2.88 0.433 0.009 4.724 )8.22 )4.6895/56 II-5 14.0 1.416 5.10 1.45 0.468 0.079 0.595 – –

95/82 IV-7 16.6 17.467 30.01 30.77 0.806 0.284 0.284 )3.26 )4.3095/58 II-7 16.7 6.304 11.14 10.90 0.791 0.271 0.292 )3.77 )4.4795/60 II/8 17.3 6.035 14.75 6.90 0.462 0.114 0.403 )7.02 )3.8195/61 II/9 18.2 7.144 19.72 5.47 0.351 0.077 0.455 )7.05 )4.1595/63 II/11 19.1 4.385 12.58 3.70 0.386 0.082 0.473 )5.94 )3.8395/67 II-15 20.6 2.602 10.53 3.31 0.582 0.064 0.716 )1.54 )4.3695/69 II-17 21.3 7.776 33.42 7.71 0.454 0.086 0.284 +0.97 )5.2895/70 III-1 23.2 0.721 3.13 0.97 0.616 0.086 0.716 )3.70 )5.0995/77 III-8 30.8 – – – – – – )2.82 )4.97aConcentration in solution (10 ml, see methods).bMolar ratio.

178 A. Rosenfeld et al. / Journal of African Earth Sciences 38 (2004) 169–181

(occurrence of both Cytheromorpha fuscata and Hetero-

cypris salina) and an upper 2B zone, from 13.5 to 6.5 m

(absence of Cytheromorpha fuscata and presence of only

Heterocypris salina). The absence of Cytheromorpha

fuscata in the 2B zone may indicate a higher salinity in

this zone. It should be emphasized that we are evaluat-

ing the highest salinity to be only about 8–10&. Thissubdivision reflects the second order cyclicity. These two

parts may be correlated to the third and fourth second-

order sedimentary cycles.

Other findings strengthen the interpretation that the

lower part of the section had a freshwater–oligohaline

environment of deposition. The two diatom assemblages

(H1 and H4 of Ehrlich, 1973) found in the lower part of

the GBY sequence indicate a very shallow freshwater,eutrophic, alkaline environment. A poor epiphytic

assemblage characterizes zone H1. Zone H4 is domi-

nated by epiphytic species and by benthic–planktic

forms together with abundant sponge spicules and

chrysophyte cysts. Gasse et al. (1987, pp. 9–10) observed

a reasonably good correlation between chrysophyte

contents and the frequencies of freshwater organisms.

Thus we think that the specimens of the algae Chara sp.(Plate 1, Fig. 10), which occur only in the lower part of

the section (Sample 95/67) should indicate low salinity.

Furthermore, it should be noted that Candonid spe-

cies, which originate in cooler climates (Martens and

Ortal, 1999), represent about 60% of the ostracods

present in the GBY section, while they represent only

some 10% of the recent non-marine ostracods in Israel.

This is in accord with the conclusion of Martens andOrtal (1999) which states that most of the Mediterra-

nean served as refugium for Western European faunas

during glacial phases.

5.2. Geochemical zones

There is a strong relationship between the Sr/Ca and

Mg/Ca ratios of the ostracods and of the waters in

which they moulted (De Deckker et al., 1999, see also

references therein). Most of the relationships between

the two curves (Sr/Ca and Mg/Ca) in Fig. 3 may beexplained by the peaks in the deposition of biogenic

aragonite due to the relative abundance of gastropods in

the sediment, because aragonite is much richer in Sr

than calcite. The precipitation of aragonite lowers the

Sr/Ca ratio in the lake waters while precipitation of

calcite increases it. The precipitation of both calcite and

aragonite increases the Mg/Ca ratios. This is true even in

an open lake where the concentrations are diluted butthe cation ratios do not change significantly.

It is possible to distinguish three sections along the

Sr/Ca and Mg/Ca curves. I––A lower interval from �21

to �18 m where the two curves have similar trends. II––

A large middle interval from �17 to �9 m where the

relations are not clear-cut but in the main the Sr/Ca

ratios have opposite trends to those of the Mg/Ca ratios.

III––A small upper interval from �9 to �6 m where thetwo curves have again similar trends. In the lower

interval of the curve the endogenic, biogenic calcite is

low magnesium calcite (ostracod shells); therefore pre-

cipitation of this calcite increases both ratios. In the

middle–upper interval the endogenic, biogenic carbon-

ate is mainly aragonite (gastropod shells). Formation of

aragonite gastropod shells (rich in Sr) lowers the Sr/Ca

ratio while it increases the Mg/Ca ratio in the lake wa-ters. In the uppermost part it is again low magnesium

calcite. This explains the opposite trends of the Sr/Ca

and Mg/Ca ratios in parts of interval II and the well-

A. Rosenfeld et al. / Journal of African Earth Sciences 38 (2004) 169–181 179

defined covariant trends in intervals I and III. Thealternation of relatively high and low Sr/Ca and Mg/Ca

ratios suggests alternating conditions which are consis-

tent with a small lake subject to rapid fluctuations. The

lower interval (I) may be correlated to the second sedi-

mentary cycle while the third interval (III) may be cor-

related to the fourth sedimentary cycle.

The variability of the d13C values of Candona neglecta

valves is greater than that of the oxygen isotopic values(Fig. 3). The values range between )9& and 3& with a

general cyclical pattern. The d13C values of ostracod

carbonate are mainly controlled by the d13C of dissolved

inorganic carbon (DIC) in the ambient lake water. At

the same time d13C values seem to be systematically

biased by microhabitat and vital effects (Von Graffen-

stein et al., 1999). In the bottom waters, both respiration

and oxidation of the organic matter that formed at thesurface waters at times of high productivity decrease the

oxygen concentration, raise the DIC and lower the d13Cof the DIC (Deuser and Hunt, 1969; Shackleton and

Vincent, 1978). There are three clear peaks of negative

value for d13C: )7.1& at 18.2 m, )8.6& at 11.7 m and

)5.6& at 8 m (Fig. 3). These values indicate high pro-

ductivity and it can be seen that they are found near the

beginning of the secondary sedimentary cycles 2, 3 and4. The lower and upper peaks of the negative d13Ccoincide with the ostracod population density peaks

(Table 1). The highest negative values (middle peak)

coincide with the exceptionally high Mg/Ca value (Table

3, Fig. 3) due to very high productivity (formation of

biogenic carbonate). We are aware of the exceptionally

high positive value of sample 96/203 (Table 3 and Fig.

3). Nevertheless, this is a single measurement on whichwe could not make a duplicate because of lack of os-

tracods, therefore apart from the fact that it agrees with

the lowering of productivity towards the top of the

section, we are unable to draw further conclusions.

The d18O values vary from )5.3& to )3.8&. They

show a trend to heavier isotopes in the interval between

21.3 and 17.3 m ()5.3& to )3.8&) and an opposite

trend in the interval 17.3–6.4 m ()3.8& to )5.3&). Weinterpret the d18O variations as mainly due to tempera-

ture changes and not due to concentration (evaporation)

or dilution (rain). We base this on the small salinity

changes inferred by the ostracod assemblages and the

fact that the GBY Lake was for most of its history an

open lake (Horowitz, 1979; Moshkovitz and Magaritz,

1987). Moshkovitz and Magaritz (1987), from their

study of C and O isotope records of middle and latePleistocene molluscs, reached the conclusion of high

productivity and found no evidence for high evapora-

tion in the Hula basin. Our results indicate a decrease in

temperature followed by an increase. The most promi-

nent climatic event seems to have occurred at the tran-

sition between intervals I and II, where the trends invert.

The decrease in temperature indicates the beginning of

the lake and the increase in temperature is consistentwith the interpreted retraction leading to its desiccation

toward the upper part of the sequence.

We are aware that there might have been short peri-

ods when the water level in the GBY Lake was so low

that it was lower than the exit, leading to the formation

of a closed lake during these short periods. We have

no direct evidence from the ostracod distribution or

their chemistry since they were formed at high stands,nevertheless the occurrence of pedogenic profiles indi-

cating brief desiccation events (see sedimentology) sup-

ports this possibility.

6. Conclusions

The cyclicity observed in the GBY sediments is

also recorded by the ostracod distribution, population

density and chemistry of their valves. The ostracod

distribution indicates at least two biozones, a lower

freshwater–oligohaline and an upper oligohaline–meso-

haline zone.

Climatic changes during the time interval sampledreflect (d18O values) a lowering of the temperature fol-

lowed by a gradual warming. This agrees with Horo-

witz’s (1979, 2001) synthesis, which concludes that

during pluvial periods the climate was cooler and these

periods are characterized by an expansion of the lakes in

the Jordan and Hula basins. During interpluvial peri-

ods, the climate was hotter and these periods are char-

acterized by the retraction of these lakes and thedesiccation of some of them.

The sedimentology, ostracod population density and

the ostracod valve chemistry (Sr/Ca and Mg/Ca ratios,

d13C and d18O) all exhibit a cyclicity, which reflects the

expansion and retraction of the lake. Five such cycles

were observed (Fig. 3). The detailed reconstruction of

the lake properties adds much to the understanding of a

well-known phenomenon of repetitive palaeolithicoccupations along lake shores, which are known from

Africa and Eurasia. The results of this study are viewed

as an additional evidence for the notion that the dis-

persal ‘‘Out of Africa’’ was a mechanism of repetitive

waves.

Acknowledgements

We are grateful to Mr. M. Dvorachek for the SEM

micrographs, Mrs. T. Beer for preparing and washing the

samples and Mr. Y. Levy for printing the photos. We

thank Mr. S. Hoyland for preparing the location map,

and Mrs. N. Shragay and B. Cohen for their technicalassistance. Last but not least we thank Dr. I. Boomer for

his careful review and remarks, which considerably im-

proved an earlier version of the manuscript. The Irene

180 A. Rosenfeld et al. / Journal of African Earth Sciences 38 (2004) 169–181

Levi Sala Care Foundation and the L.S.B. LeakeyFoundation supported fieldwork at GBY.

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