lmvmd of Afiican Earth Sciences, Vol. 13, No. 3/4, pp. 367-375, 1991. 0899-5362/91 $3.00 + 0.00 Prin'a:d in Thailand © 1991 Pergamon Press plc

Surface textures of quartz grains from Recent sedimentary environments along the Mediterranean Coast, Egypt

M. A. A. ABD-ALLA

Geology Deparunent, Faculty of Science, Mansot~a University, Egypt

(Accepted for publication 25 September, 1990)

Abstract - This study identifies the assemblages of quarlz-grain surface texttwes in sends from five Recent environments along the Mediterranean coast end adjoinin8 desert regions of Egypt. The results of this study, using the scarmin 8 electron microscopy (SEM) reveal the existence of several surface feat~es that reflect the effect of mechanical end chemical action on the studied quartz grains.

Qumz grains of beach, ne~shore, coast~l dune end desert send sheets show an abundance of bothmechmical and chemical surface features developed during ~ensportation of the grains in the subaqueons end aeolian environments respectively. On the other hand, sand grains from sabkha sedimen~ are ch~ac~rized by the dominence of chemical surface features. Among chemically produced surface features, those originating from silica dissolution are considerably more numerous Oum those due to silica precipitation.

Relative frequency dislributions of the various surface features recorded on quartz grains from different onvironments indicate a considerable overlap in the types of surface feature from beach sands and nearshore sends to coastal dune sands end vise versa, as might be expected in this system where sediment has been recycled between markedly dune end coastal mmine settings.

INTRODUCTION

The present paper at tempts to determine the surface features characteristics of quartz sand grains from the var ious Recent sed imenta ry environments in the Mediterranean coastal and desert areas of Egypt. The occurrence, frequency distribution and overlapping of chemical and mechanical surface features are used to clarify the relat ionship be tween the various Recent sedimentary environments in Egypt and their genesis.

The investigation of quartz gram surface textures of modern Nile Delta coastal environments made by El Fishawi and Molnar (1984) and Frihy and Stanley (1987) showed that it is possible in some cases to distinguish sands from several subaerial and subaqueous environments . Also, surface features of quartz sand grains have been used in interpreting the depositional environments of Holocene subsurface core sand samples (EIAskary and Frihy, 1984) and Quaternary subsurface core sand samples [Frihy and Stanley, 1987) in the Nile Delta area.

Extensive use has been made of scanning electron microscopy (SEM) to s tudy surface textures of detrital mineral grams, in particular those of Recent quartz grains. The s tudy of surface features on coarse (> 500 Jan} sand-slzed quartz grains by SEM techniques has developed into a

ma jor m e t h o d for i n t e rp re t ing s e d i m e n t a r y environments and t ransport mechanisms. Criteria for d is t inguishing mechan ica l and chemica l features and their implications have been well establ ished (Krinsley and Doornkamp, 1973; Whalley and Krinsley, 1974 and Krlnsley, Friend and Klimentidis, 1976). At tempts have been made to use these surface features to determine depositional environments of ancient sediments (Black-welder and Pilkey, 1972; Nordstrom and Margolis, 1972; Krinsley e t al., 1973 and Kholief, 1983). Surface textures of quartz sand grains have been used to identify the sources and genesis o f various detrital sediments (Ly, 1978; El Fishawi and Molnar, 1984; EIAskary and Frilly, 1984 and Frthy and Stanley, 1987). However, some caution in the use of surface features as indicators of deposiUonal environments has been suggested (Subramanian, 1975 and Manker and Ponder, 1978).

NATURE OF THE STUDIED AREA

The nor thern Mediterranean coast of Egypt along the studied area (Fig. 1} comprises a narrow zone, nearly fiat and characterized by low relief and mild gradients. It is typified by large peripheral lakes (e.g. Idku and Burullus), closed lake (Maryut), ex- tensive costal fiats and shows m a n y features of earlier progradlng and present retreated coastline.

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Fig. I. Map show/rig pos i t ion of the s t u d e d samples .

Several geological s tud ies have been carried out on the nor the rn coast of Egypt (Hume, 1925; Hflmy, 1951; Shukr i and Phil/p, 1955a and b; Fr/hy, 1975; Anwar, et aL, 1984; Ahmed, 1987 and Coutelller a nd Stanley, 1987). Sestin/(1976) des- cribed the coastal morphology including the shore line features, old accret ion ridges, backshore plain and the coastal dunes . The shore line features comprised the beach, cusps , spits and small shore dunes. He also described isolated scat tered small groups o fba rchan and sief dunes on the backshore plain.

TYPES OF SEDIMENTS STUDIED

The nor the rn Medi terranean coast of Egypt is covered by Recent sediments . Based on their textures and mode of occurrence, the following Recent sediment types can be recognized:

(a) coastal sed iments (beach sands , nearshore sands , coastal d u n e s and sabkha deposits) and

(b) desert sed iments (sand sheets). Beach and nearshore sand deposits are the

d o m i n a n t type of R e c e n t s e d i m e n t s in the Medi terranean coast of Egypt. They are composed of poorly-sorted mixture of sand, silt and clay. Coastal s and d u n e s are a very consp icuous land- form, especially in the Nile Delta coastal plain. They extend parallel to the shore and separate the shore zone from the cult ivated a n d / o r the sabkha areas. These s and dunes show a variety of forms i n c l u d i n g b a r c h a n , l o n g i t u d i n a l a n d t r a n s - verse dunes . They are composed of quartz sand occas iona l ly mixed wi th some m a r i n e shel l fragments.

The coastal s abkha is wide spread on the areas a round the lakes and in the inland par t of the supra t idal fiat area. In the Nile Delta sabkhas b o u n d seaward by the intertidal fiat and landward by the coastal dune belt a n d / o r the cult ivated land.

The sou the rn par t of the area, sou th to Burg El Arab, is a vas t erosion surface (desert peneplain) which in m a n y places lies bare or is partially

covered with a th in veneer of mobile sand. These sand sheets are generally well sorted and are composed mainly of quartz.

METHODOLOGY

Thirty seven samples have been collected from 11 sites (Fig. 1). These samples were chosen to represent the var ious types of Recent deposi ts that covered coastal and deser t areas (Table 1). The procedures used for cleaning quartz sand grains for SEM examinat ions are those described by Krinsley and Doornkamp (I 973). Each sample was t reated with 15 % HCI, to digest ca lc ium carbonate material and passed th rough a 0.063 m m sieve and dried. The coarsest quartz grains were hand- picked unde r a binocular microscope. It is noted tha t only monocrys ta l l ine quar tz gra ins were se lected for c o m p a r i s o n of sur face fea tures , m o u n t e d on SEM a l u m i n u m spec imen s tubs and coa ted wi th a layer of gold in an Edwards 306 v a c u u m e v a p o r a t o r . The g r a i n s were examined with a Cambridge In s t rumen t s Stereo- scan S-306 Scanning Electron Microscope. Fifteen quartz grains from each sample were randomly selected by the line me thod (Carver,1971) for detai led observat ion. Each gra in was photo- graphed in full view, and t h e n its edges and faces were p h o t o g r a p h e d at h igher magnif ica t ions . The photographs of the quartz grains were then described, classified and tabulated.

RESULTS

In general, the examined quar tz gra ins are rounded to subrounded , bu t angular grains are also present . The rounded coarse-gralned quartz grains are generally frosted, whereas the fines grains are most ly smooth.

Investigations of the surface textures of quartz grains from the different types of Recent sed iments of the area of s tudy reveal the effects of mechanica l and chemical act ion on the s tudied quartz grains. Mechanical features are mainly v-shaped pits, c rescen t - l ike pi ts , d i s h - s h a p e d dep re s s ions , u p t u r n e d plates, s traight and .curved grooves, str iat ions and s tepped cleavage planes.

Table I. N u m b e r s , locat ions a n d facies of s t ud i e d s a mp le s .

Sample No.

IA, 1B, IC 2A, 2B, 2C 3A, 3B, 3C, 3D, 3E 4A, 4B, 4(2 SA, 5B, 5C 6A, 613, 6C 7A, 7B, 7C 8A, 8B, 8C 9A, 9B, 9C 10A, 10B, 10C, 10D. 10E IIA, lIB, 11C

Location No.

1 2 3 4 5 6 7 8 9

10 11

I.zx~t/on

Gamasa Garaasa Ras El Ba~r Rats El Ba~r Alexandria Alexandria Burg El Arab Burg El Arab Burg El Arab South Burg El Arab

Facies

Beach studs Nearshare sands Coastal dune sands Beach sands Nearshore sands Beach sands Nearshore sands Beach sands Ne.anshere sands S.l~r,h. dep~.- Desert sa_~s

Surface textures of quartz grains from recent sedimentary environments along the Mediterranean Coast, Egypt 369

Chemical features are manifested on quartz gram surfaces by solution and precipitation textures, e.g., triangular etching pits, irregular solution pits, crystal overgrowth and smooth precipitation surfaces. Figures 2 to 6 show some of the results obtained.

Study of the relative frequency distribution of various surface features recorded on the quartz grains show that each type of sediment is characterized by an abundance of certain sur- face features. Other features may be present in addition to the main characteristic features (Fig. 7).

Coastal Sediments (at) B e a c h s a n d s - SEM examinations of the

quartz sand grains from the beach sands revealed that most of the grains are rounded to subrounded (Fig. 2A). The surface features of the quartz grains are m_~inly represented by mechanical v-shaped impact pits, rounded and pitted grooves, surface and edges roughness and upturned plates (Fig. 2B, C and D).

Such surface features may reflect the effects of both subaqueous and aeolian origin. The sub- aqueous origin is supported by the presence of v-shaped pits and rounded and pitted grooves (Krinsley and Doornkamp, 1973), whereas the aeolian effects are related to the presence of up- turned plates. The presence of aeolian features in such beach sediments may suggest that some aeolian sands were reworked by waves and tides to form these beach sand deposits.

Also, the roughness of surfaces and edges of some of the quartz grains {Fig. 2A) are character- istics for differential chemical weathering related to the differences in chemical resistance within the grains {Krlnsley and Doornkamp, 1973}.

(b} N e m h o r e s a n d s - The surface features of quartz grains from the nearshore sands are more or less similar to those described from beach sands, especially by the prevalence of mechanical features rather than chemical ones.

Quartz grains in nearshore sands commonly display typical subaqueous abrasion features {Fig. 3A). V-shaped pits and crescent-like pits (Fig. 313) are prominent. Some nearshore quartz

A- Rounded grain shows surface and edges roughness. B- V-shaped pits and straight and curved grooves in association with silica precipitation.

C° Solution, precipitation and upturned plates. D- Upturned plates with V-impact pits scattered over the surface of the grain.

Fig. 2A-B-C-D. SEM micrographs of surface features of quartz grains from beach sands.

370 M. A. A. ASD-ALLA

A- Subrounded grain showing smooth, abraded surface w/th percussions pits.

B- Upturned plates abut the smooth abraded edge (aeolian action), V-shaped pits and crescent-like pits (normal beach

action).

C- Subrounded graln displaying smooth surface and D- Upturned plates in association wlth V-lmpact pits, well rounded comers, solution and precipitation.

Fig. 3A-B-C-D. SEM mlcrographs of surface features of quartz grams from nearshore sands.

grains display aeolian features such as smooth- ness and upturned plates (Fig. 3C and D) which record earlier t ransport of some nearshore grains by wind.

(c) C o a s t a l d u n e s a n d s - Quartz grains from coastal dune sands are commonly rounded to subrounded and characterized by smooth sur- faces with a few mechanical pits scattered all over the grain surface (Fig. 4A). They are mainly c h a r a c t e r i z e d by d i s h - s h a p e d dep re s s ions , conchoidal fractures, up turned plates, striations, s t epped c leavage p l anes and v - shaped pits (Fig. 4B, C and D). One of the most important features that characterize quartz grains of the coastal dunes is silica precipitation (Fig. 4B}. The smoothness of these grains (Fig. 4A) may be due to the action of the water evaporation during the day/nlght cycle. Evaporation of pore water in these sediments during the day usually leads to concentration of evaporites and, therefore a rise in the pH value of the water. Under these conditions silica solution from some parts of the quartz grain

surface (especially in projected areas) is re- depos i t ed in concave a r e a s (Kr lns ley a n d Doomkamp, 1973). Such process tends to smooth the grain surface and leads to the development of well rounded comers (Fig. 4A and B). The v-shaped pits similar to those present on the surface of quartz grains of the beach sands are also common (Fig. 4D). This is probably a relict from some subaqueous environments. The presence of such features also indicates the possibility of grain transportation from marine environment.

(d) SablrdU deposl t~ - Quartz sand grains from sabkha deposits are mainly character ized by c h e m i c a l f e a t u r e s r a t h e r t h a n f e a t u r e s of mechanical origin. They are character ized by tr iangular etching pits (Fig. 5A). These textures usually indicate a high energy chemical environ- ment (Krinsley and Doornkamp, 1973). Clear etching edges and deep etching grooves (Fig. 5B) are commonly present as a result of chemical process, in particular, silica solution. Additionally, the surfaces of the quartz grains from sabkha

Surface textures of quartz grains from recent sedimentary environments along the Mediterranean Coast, Egypt 371

Pig. 4A. SEM micmgraphs of surface features of quartz grains from coastal dune sands. A- Small well-rounded grain with a

few mechanical pits and smooth surface.

B- Rounded grain shows conchoidal fractures and dish-shaped depression associated with silica precipitation.

C- Concholdal fractures in association with striations and 4D- Impact V-shaped pits with upturned plates. stepped cleavage planes.

Fig. 4A-B-C-D. SEM mierographs of surface features of quartz grains from coastal dune sands.

~ - Triangular etching pit associated with silica 5 B- Clear etching edges and deep etching grooves modified precipitation and scattered silica plastering, by solution (vigorous chemical action).

Fig. 5A-B. SEM micrographs of surface features of quartz grains from s a b k h a deposits.

d e p o s i t s a l so d i s p l a y s i l ica p r e c i p i t a t i o n f e a t u r e s , e.g., i r r e g u l a r p l a t e s a n d c a v i t y fil l ing a s well a s

372 M . A . A . ABD-ALLA

5C- Scattered silica plastering associated with triangular ~D- SlUca precipitation associated with upturned plates and solution pits and irregular plates. V-shaped pits.

Flg. 5C-D. SEM mlcrographs of surface features of quartz grains from s a b k h a deposits.

6A- Highly rounded grain with Irregular depression In the middle due to mechanical chipping during powerful sand

s t o r m s .

6B- Well rounded and abraded grain, pitted and worn by abrasion.

6C- Coneholdal fractures associated with upturned plates 6D- Dish-shaped depressions associated with eoncholdal and V-shaped pits. fractures and deep pits modified by silica solution.

Fig. 6A-B-C-D. SEM mlcrographs of surface features of quartz grains from deser t sand sheets .

Surface textures of quartz grains from recent sedimentary environments along the Mediterranean Coast, Egypt

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Fig. 7. Summary of occurrence of mechanical and chemical features on sand-sized quartz grains of the Recent sediments along the Mediterranean coast of Egypt and adjoining desert

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silica plastering (Fig. 5C) where excess silica is pressed over a quartz grain surface in a non- oriented pat tern. This m ay be explained by the movement of gra ins across one ano the r unde r high pressure (Krinsley and Doornkamp, 1973). Relicts of mechanica l features as v-shaped pits and up- t u rned plates are usual ly m a s k e d by chemical features. The types and frequency of chemical features of quartz grains from sabkha deposi ts

373

suggest tha t the grains have been subjected to a high energy chemical environment .

Desert Sed iments (sand sheets} Quartz grains with highly spherical and rounded

outl ines and worn and abraded grain surfaces (Fig. fiA and 13) are a b u n d a n t m the desert sands occurring as s and sheets. The r o u n d n e s s and mechanical abras ion textures of the grains are presumably the product of aeolian abrasion, which is capable of abrading and round ing quartz grains of all sizes (Kuenen, 1960).

Quar tz g ra ins are c o m m o n l y charac te r ized by the p redominance of mechan ica l features, especial ly concho ida l f rac tu res , d i s h - s h a p e d depress ions and irregular depress ion and impact v-shaped pits (Fig. 6C and D). The action of t ranspor t by wind may be responsible for the formation of such features dur ing s t rong sand a n d / o r dus t s torms. Upturned plates, which are usual ly developed by mechanica l action, have been w o m and smoothed by abras ion

Signs of minor chemical features were noticed on the surface of these gra ins by the presence of deep pits, which are most ly due to the solut ion of silica along microfractures in an alkaline near-surface diagenetic environment .

DISCUSSION AND CONCLUSIONS

Investigation of the surface features of quartz sand grains from various Recent envi ronments along the Medi te r ranean coas t of Egypt and adjoining desert areas reveals the occurrence of two m e a n features, mechanica l and chemical. From the relative f requency dis t r ibut ion of the various surface features on the quartz s and grains, it is noted tha t mechanica l features are dominan t in desert sands , coastal dune sands , and beach and nearshore sands. Chemical features are mostly confined to coastal s abkha deposits.

Mechanical features can be grouped into fossil or relict features and Recent features. Fossil features are those inher i ted from the original deposit ional envi ronment . Recent mechan ica l fea tures are commonly super imposed on the fossil surface fea tures . The m o s t i m p o r t a n t .fossil su r face features that reflect the s u b a q u e o u s envi ronments are the v-shaped impact pits. Their presence on non-mar ine sands probably indicate tha t these sands were recycled by water. Quartz grains with conchoidal f ractures and u p t u r n e d plates have been identified in a lmost all s tudied Recent sedi- men t types. Recent mechanica l features are main- ly generated dur ing aeolian t ranspor t of the quartz sand grains. Such features are -represented by pitting and cracking of the grain surface due to v i o l e n t w i n d a b r a s i o n , e .g . , d i s h - s h a p e d

374 M.A.A.

depression, i r regular depress ion and str iat ions. It was also observed t h a t Pitting act ion is more p ronounced in the coarse quar tz gra ins of deser t s and and coasta l dune sand , which is great ly affected by sa l ta t ion processes, especially dur ing s a n d s torms.

Chemical fea tures , main ly genera ted by solut ion (etching) a n d precipitation, are a lmost developed in the coas ta l s a b k h a deposits . Solut ion a n d precipi tat ion are also presen t in the near -sur face diagenetic env i ronment of quar tz s and gra ins of coastal dunes . The increas ing rate of evaporation, which charac ter izes the arid a n d semi-arid a reas and the a b u n d a n c e of sa l ts in the pore water which increases the pH, are the mos t impor tan t factors in inf luencing the development of chemical features.

The following m a y t h u s be concluded from this s tudy: 1- The assemblage of mechan ica l a n d chemical

surface fea tures of sand-s lzed quar tz gra ins from the s tud ied Recent sed iments along the Medi te r ranean coas t of Egypt and associated env i ronments show overlap similari ty a s would be expected in a deser t -coas ta l -mar ine sys tem where sed iment is readily recycled between marked ly different envi ronments . This clearly suppor t s the conclus ions in the previous s t u d y in the Nile Delta area by Fr ihy and Stanley 1987.

2- Relative f requency d i s t r ibu t ion s t u d y high l ighting the propor t ions of mechan ica l and chemical features , however, shows tha t there are sufficient differences in the assemblages of tex tures to d is t inguish the aeol ian-dominated envi ronment (desert s a n d s a n d coastnl dune sands ) f rom the s u b a q u e o u s e n v i r o n m e n t beach sands , and nearshore s a n d s from the chemica l ly a c t i v e - d o m i n a t e d ones ( sabkha deposits).

Acknow/edgements - The present work was carried out at the Geology Department, University of Glasgow, U.K. The author was funded by a post-doctoral followship awarded by the British Council in Cairo. The help of Prof. B. E. Leaks and Dr. W. G. Jardin~ for providing SEM facilities is gratefully acknow- ledged. "[he author wishes to thank Mr. P. Ainsworth at the SEM unit. Many thanks are due to Dr. A. El Shahat , Geology Dept., Mansoura University, Egypt and Prof. D. J. Stanley, Smithsonian Institution, Washington, for their useful comments and for review- ing the manuscript.

REFERENCES

Ahmed, ~ A. 1987. Geomorphological and sedimento- logical studies on the Mediterranean coastal plain along the Nile Delta, Egypt. M.Sc. Thesis, Mansoura University, Egypt, 283 p.

ABD-AL~

Anwar, Y. M., El Askary, M. A. and Frihy, O. E. 1984. Reconstruction of sedimentary environments of Rosetta and Damletta promontories in Egypt, based on textural analysis. J. Aft. Earth Sct, 2, 17-29.

Blackwelder, P. L. and Pilkey. O. H. 1972. Electron microscopy of quartz grain surface textures, the U.S. eastern Atlantic continental margin. J. Seal. Petro/., 42, 520-526.

Carver, R. E. 1971. Procedures in Sedimentary Petrology. New York, Wiley Intersclence, 653 p.

Coutelller, V. and Stanley, D.V. 1987. Eastern Nile Delta evolution during the Holocene. Mar. Geo/., 77, 257- 275.

El Askary, M. A. and Frihy, O. E. 1984. Environmental interpretation of sand grain surface textures in the Rosetta and Damietta promontories along the Nile Delta coast, Egypt. N. Jahrb. GeoL Pa/aontoL Monatsh, 12, 709-716.

El Fishawi, M. and Malnar, B. 1984. Distinction of the Nile Delta coastal environments by scanning electron microscopy, a statistical evaluation. Acta Mineral Petrogr., Szeged, 28, 709-716.

Frihy, O. E. 1975. Geological study of Quaternary deposits between Abu Quir and Rashid. M.Sc. Thesis, Alexandria University, Egypt, 103 p.

Frihy, O. E. and Stanley, D. J. 1987. Quartz grain surface textures and depositional interpretations, Nile Delta region, Egypt. Mar. Geo/., 77, 247-255.

Hflmy, M. E. 1951. Beach sands of the Mediterranean coast of Egypt J. Seal. Petro/ogy, 21, 109-120.

Hume, W. F. 1925. Geology of Egypt Surv. Dept., Cairo, 408 p., (2 vol.).

Kholief, M. M. 1983. Interior cavities and exterior surface texture of detrltal quartz of some Egyptian clasUc sediments. J. Petm/. Geo/, 5(4), 427-436.

Krinsley, D. H. and Doornkamp, J. 1973. Atlas of Quartz Sand Surface Textures. Cambridge University press, Cambridge, England, 91 p.

Krlnsley, D. H, Blscaye, P. 1~ and Turekian, IC IC 1973. Argentine basin sediment sources as indicated by quartz surface textures. J. Sed. PetroL, 4S, 251- 257.

Krinsley, D. H., Friend, P. and Kllmentldis, R. 1976. Eolian transport textures on the surfaces of sand grains of early Triassic age. Bu/L GeoL Soc. Am., 87, 130-132.

Kuenen, P. H. 1960. Experimental abrasion, 4. Eolian action. J. GeoL, 68, 427-449.

Ly, C. K. 1978. Grain surface features in environmental determination of late Quaternary deposits in New South Wales. J. Seal. PetroL, 48, 1219-1226.

Manker, J. P. and Ponder, R. F. 1978. Quartz grain surface features from fluvial environments of north eastern Georgia. J. Seal. Petrol., 48, 1227- 1232.

Nordstrom, C. E. and Margolls, S. V. 1972. Sedimentary history of central California shelf sands as revealed by scanning electron microscopy. J. Sed. PetroL, 42, 527- 536.

Sestini, G. 1976. Geomorphology of the Nile Delta. UNESCO, Coastal Protection Project. In Proceed Sem. on Nile Delta Sed., UNDP/UN/ASRP, Alex., Oct,, 1975, 12-24.

Surface textures of quartz grains from recent sedimentary environments along the Mediterranean Coast, Egypt 375

Shukri, N. M., Philip, G. 1955a. The geology of the Mediterranean coast between Rosetta and Bardia. Part I, Recent sediments. Bull Inst. Egypte, 37, 377-395.

Shukrl, N. M. and Philip, G. 1955b. The geology of the Mediterranean coast between Rosetta and Bardia. Part Ill, Pleistocene sediments, mineral analysis. Bull. Inst. Egypte, 37, 445-455.

Subramanlan, V. 1975. Origin of surface pits on quartz as revealed by scanning electron microscopy. J. Seal. Petrol., 45, 530-534.

Whalley, W. B. and Krtnsley, D. H. 1974. A scanning electron microscope study of surface textures of quartz grains from textural environments. Sed/mento/cxjy, 21, 87-105.