Composition of clays along the continental shelf off Israel: contribution of the Nile versus local sources

doi:10.1016/S0025-3227(00)00021-9

Marine Geology

Volume 167, Issues 3–4, 15 July 2000, Pages 339-354

https://doi.org/10.1016/S0025-3227(00)00021-9 Get rights and content

Abstract

The eastern Mediterranean sedimentary regime is dominated by sediment transport from the Nile River and its delta, but recent studies have also suggested a certain contribution of clay fraction from streams to the continental shelf and slope off Israel. In the present study we focused on clay fraction deposition along the inner (∼40–1000 m water depth) shelf of Israel in order to substantiate and quantify its different sources. For this purpose detailed XRD mineralogical determinations as well as chemical compositions of the clay (<2 μm) fraction of marine and continental sediments were used.

The clay mineral composition of Israeli stream sediments is variable, with no distinct spatial or temporal trend, but within a limited assemblage. This clay assemblage is made up of illite–smectite (IS) phases (70–90%), kaolinite (5–25%) and illite (<10%) and is similar to that of the Nile. However, it is clearly distinguished by the type of the IS phases, which are derived mainly from Mesozoic outcrops and recent sediments/soils and are less expandable than those of the Nile, which are derived mainly from weathered basalt. The Nile-derived component is depleted in the marine clay fraction along the Israel coast, evidenced by a decrease of IS expandability and the Fe₂O₃/Al₂O₃ ratio, and an increase in the K₂O/Al₂O₃, MgO/Al₂O₃ and CaO/Al₂O₃ ratios. The depletion is well pronounced north of Tel Aviv, where the largest coastal plain stream flows to the sea. A northward increase of carbonates in the clay fraction, and particularly of the bioskeletal component is indicated by the ratios of MgO and Sr to CaO. The contribution of the local streams to the shallow shelf marine clay fraction is estimated to be about 50%.

A minor contribution of desert dust is identified by the relative increase in kaolinite in the marine sediments south of Tel Aviv.

Introduction

The sandy sediments deposited on the eastern Mediterranean shallow shelf along the Sinai and Israel coasts are derived from the Nile River and its delta. This has been established both by measuring current and wave directions (Emery and Neev, 1960, Golik, 1997) and by various sediment characteristics (Pomerancblum, 1966, Rossignol, 1969). Much attention has been given to sand transport along the Israeli coast since the cessation of sediment supply to the sea by the Nile, due to the construction of the Aswan Dam in 1964, and its immediate impact on the erosion of the Egyptian coast. Furthermore, longshore sand transport along the Israeli coast has been obstructed by seaward projecting coastal installations (Golik, 1997). While sand movement has been given much attention, there is no information on the clay chemical composition and only limited information on its mineralogical composition and spatial distribution on the shallow shelf off Israel. Clays in the marine environment are easily dispersed by currents and may serve as good tracers for their source (e.g. Chamley, 1989, Gingele and Leipe, 1997). Since organic and inorganic pollutants tend to concentrate in the clay fraction, the recognition of continental clay transport in the sea might bear environmental significance.

The mineralogical composition of the clay fraction in sediments from the Nile Delta to northeast of Cyprus has been established as almost uniform, consisting of smectite (50–80%), kaolinite (Ka) (15–40%), illite (I) (0–15%), and possible traces of chlorite (Ch) (Venkatarathnam and Ryan, 1971, Nir and Nathan, 1972, Maldonado and Stanley, 1981, Emelyanov, 1994). The contribution from the Nile River was regarded as dominant, whereas contribution to the shelf from the Sinai and Israeli streams was assumed to be negligible (Nir, 1984). Most of the previous clay studies outlined the general pattern of the Levantine Basin, with no specific attention to the shallow shelf (<1000 m depth).

Recently, Stanley et al., 1997, Stanley et al., 1998 determined clay mineralogical composition of Israeli stream sediments, compared them to those of the eastern Mediterranean sediments and the Nile and concluded that there is a certain, but unquantified, contribution from the Israeli streams. High concentrations of trace-metals in marine sediments of the shallow shelf off Israel were found in a study by Goldsmith et al. (submitted), who suggested contribution by fine fractions of polluted streams.

There is no direct measurement or even estimation of the quantity or composition of sediments that are carried by the streams to the sea. Several streams are only monitored for their annual water. Clay fraction composition should be used to evaluate the continental contribution to the shallow shelf sediments.

All previous clay studies used the relative content of smectite, kaolinite and illite as a source indicator. The term “smectite” or ‘montmorillonite’ included also IS phases. The Nile smectite was once determined as a disordered IS with an illitic (non-expandable) component in the range of 20–40% (Weir et al., 1975). No such compositional analysis has yet been applied to the smectites and IS phases of the eastern Mediterranean and coastal stream sediments.

In the present study the characteristics of the IS phases and the chemical composition of the clay fraction are used in order to evaluate and substantiate the contribution and sedimentological pattern of land-derived clays versus Nile-derived clays in surface sediments on the continental shelf off Israel.

Section snippets

Mediterranean area

The continental shelf of Israel narrows (from 60 km off Gaza to 25 km off the border with Lebanon), and its base deepens from south to north (950–1150 m). The 180-km long shelf is wedge-shaped and is built mainly of Pliocene–Quaternary Nile-derived sediments, whose rate of sedimentation decreases with increasing distance from the Nile Delta (Ross and Uchupi, 1977, Almagor, 1993).

Longshore currents are the main agent of sand transport along the southeastern Mediterranean coastline: (a) Along the

Mediterranean sediment samples

The sample locations are marked in Fig. 1b. The samples were taken during 1997 along a coastal south–north traverse, at a water depth of ∼40 m, where silty clays or clayey silts are already dominant. The C3 sample, west of Haifa, was taken, however, at 166 m water depth since in shallower water the bottom was rocky. Two east–west traverses were sampled from 40 to 200 m water depths off Ashqelon and from water depths of 40 to 1000 m off Netanya. One sample from 1423 m water depth was also analyzed.

Sample processing

The clay fraction (<2 μm) was repeatedly collected from thin suspensions in settling tubes according to Stokes’ law. A portion was used for clay analysis and the rest was evaporated to dryness, desegregated to powder by a Spex mixer/mill and was used for chemical analysis. A duplicate portion from large enough samples was first treated by ∼1 N HCl to dissolve carbonates, and by 15% H₂O₂ to decompose organic matter before clay separation. The diffractograms of the treated clay fraction were of

Mineralogy

Representative diffractograms of marine and continental clay fractions are presented in Fig. 3a and b, respectively. All samples have the following composition of the clay fraction: IS>Ka≥I (Table 1). Illite was definitely identified in all marine samples but not in all continental samples. Its content does not exceed ∼10%. Chlorite content in some of the continental and marine samples is a few percent, and is 5–10% only in two marine samples. It was not detected in the two Nile samples.

The clays of the streams

The Israeli stream sediments do not show any definite or consistent clay composition pattern related to location or time. Three tributary samples that were collected at upstream stations, in addition to those of the outlets, exhibit variability along their routes. Suspensions from the same stations in different years sometimes have different mineralogical compositions. Moreover, no clear linkage to a specific lithology could be made. Palygorskite, for example, which is a common minor component

Conclusions

In spite of the high similarity in the clay mineralogical composition of the Israeli streams of the marine and of the Nile sediments, namely, IS>kaolinite>Illite, the analysis of the IS expandability enables distinguishing between them. The Nile's IS phases are much more expandable than the continental IS phases. Marine IS expandability along the Israeli coast is in-between that of the continental and that of the Nile IS phases and is closer to that of the streams.

In such similar compositions

Acknowledgements

Most marine samples were collected on board the R/V Shikmona in a cruise supported by G.J. van der Zwaan from Utrecht University. We thank: Y. Goren, N. Porat, S. Ilani, and A. Sneh for providing supplementary samples; S. Ehrlich, D. Stiber and L. Halicz for carrying out the chemical analyses; G. Almagor for commenting on an earlier version; B. Katz for linguistic editing; and J. Hall and B. Cohen for drawing the maps. We appreciate the reviews of Nathalie Fagel and Christian Robert whose

References (47)

G. Almagor
Continental slope processes off northern Israel and southernmost Lebanon and their relation to onshore tectonics
Mar. Geol.
(1993)
G. Almagor et al.
Sediment transport over the continental slope offshore northern Israel: an analysis by means of electron microscopy
Sediment. Geol.
(1996)
R. Chester et al.
Soil sized aeolian dusts from the lower troposphere of the eastern Mediterranean Sea
Mar. Geol.
(1977)
E. Ganor et al.
Transport of Saharan dust across the Eastern Mediterranean
Atmos. Environ.
(1982)
F.X. Gingele et al.
Clay mineral assemblages in the western Baltic Sea: recent distribution and relation to sedimentary units
Mar. Geol.
(1997)
F.M. Kishk et al.
Mineralogical and chemical composition of the clay fraction of some Nile alluvial soils in Egypt
Chem. Geol.
(1976)
M.D. Krom et al.
The characterisation of Saharan dusts and Nile particulate matter in surface sediments from the Levantine basin using Sr isotopes
Mar. Geol.
(1999)
N.N. Kubilay et al.
Seasonal chemical and mineralogical variability of atmospheric particles in the coastal region of the northeast Mediterranean
Catena
(1997)
D.A. McManus
Suggestions for authors whose manuscripts include quantitative clay mineral analysis by X-ray diffraction
Mar. Geol.
(1991)
D.J. Stanley et al.
Clay-mineral variations in the northeastern Nile delta, as influenced by depositional processes
Mar. Geol
(1986)

K. Venkatarathnam et al.

Dispersal patterns of clay minerals in the sediments of the eastern Mediterranean Sea

Mar. Geol.

(1971)

H.S. Abdel Wahab et al.

Clay mineralogy and the Recent evolution of the north-central Nile Delta, Egypt

J. Coast. Res.

(1991)

Almagor, G., 1976. Physical properties, consolidation processes and slumping of recent marine sediments in the...

Y. Arkin et al.

Paleocene–Early Eocene environments of deposition in the northern Negev

Isr. Geol. Surv. Bull.

(1972)

Bentor, Y.K., 1966. The clays of Israel. Guide-book to the excursions. In: Int. Clay Conf., Jerusalem, Israel. Israel...

Bergametti, G., Gomes, L., Remoudaki, E., Desbois, M., Martin, D., Buat-Menard, P., 1989. Present transport and...

P.E. Biscaye

Mineralogy and sedimentation of Recent deep-sea clay in the Atlantic Ocean and the adjacent seas and oceans

Geol. Soc. Am. Bull.

(1965)

H. Chamley

Clay Sedimentology

(1989)

S.A. Denekamp et al.

Grain-size distribution of silt in different environments along the nearshore of Israel

Isr. J. Earth Sci.

(1978)

H.A. El-Attar et al.

Montmorillonitic soils developed in Nile River sediments

Soil Sci.

(1973)

E.M. Emelyanov

Recent bottom sediments of the Levantine Sea: their composition and processes of formation

K.O. Emery et al.

Mediterranean beaches of Israel

Isr. Geol. Surv. Bull.

(1960)

M. Gal et al.

Clay mineral distribution and origin in the soil types of Israel

J. Soil Sci.

(1974)

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Composition of clays along the continental shelf off Israel: contribution of the Nile versus local sources

Abstract

Introduction

Section snippets

Mediterranean area

Mediterranean sediment samples

Sample processing

Mineralogy

The clays of the streams

Conclusions

Acknowledgements

Mar. Geol.

Sediment. Geol.

Mar. Geol.

Atmos. Environ.

Mar. Geol.

Chem. Geol.

Mar. Geol.

Catena

Mar. Geol.

Mar. Geol

Mar. Geol.

Clay mineralogy and the Recent evolution of the north-central Nile Delta, Egypt

J. Coast. Res.

Paleocene–Early Eocene environments of deposition in the northern Negev

Isr. Geol. Surv. Bull.

Mineralogy and sedimentation of Recent deep-sea clay in the Atlantic Ocean and the adjacent seas and oceans

Geol. Soc. Am. Bull.

Clay Sedimentology

Grain-size distribution of silt in different environments along the nearshore of Israel

Isr. J. Earth Sci.

Montmorillonitic soils developed in Nile River sediments

Soil Sci.

Recent bottom sediments of the Levantine Sea: their composition and processes of formation

Mediterranean beaches of Israel

Isr. Geol. Surv. Bull.

Clay mineral distribution and origin in the soil types of Israel

J. Soil Sci.