Journal of Coastal Research Fort Lauderdale, Florida Winter 1993 1I I Late Quaternary Evolution of the Northwest Nile Delta and ~ Adjacent Coast in the Alexandria Region, Egypt

Andrew G. Warne and Daniel Jean Stanley

Mediterranean Basin Program U.S. National Museum of Natural History Smithsonian Institution Washington, DC 20560, U.S.A. ABSTRACT....__...... __...... __.._

WARNE, A.G. and STANLEY, D..L, 1993. Late Quaternary evolution of the northwest Nile Delta and adjacent coast in the Alexandria region, Egypt. Journal of Coastal Research, 9(1), 26-64. Fort Lauderdale ,ttllllll't. (Florida), ISSN 0749-0208. ~ The late Pleistocene to Recent evolution of the Alexandria region, Egypt, is interpreted by sedimentologic­ stratigraphicstudy of radiocarbon-dated borings. Petrological and faunal analyses define major lithofacies, euus~_~asJt' and mapping of these subsurface sequences depicts spatial and temporal distributions of sedimentary 1&r.JW environments. Lithofacies distributions are used to compile time-slice paleogeographic maps for the past =-+; -35,000 years. New information is provided on the origin and history (since ~6,OOO years BP) of Maryut lake, the major coastal water body south and west of Alexandria. Lithostratigraphic criteria are developed to define the western limit of the Nile delta, which lies within the study area. Mapping of subsurface facies reveals that the western limit of Maryut lake (former Lake Mareotis) demarcates the western boundary of the delta; this boundary has not significantly shifted since late Pleistocene time. Facies distributions are related to natural factors which control sedimentation and coastal development in this area, and include eustatic sea-level and climatic oscillations, subsidence (compaction, isostatic depression), neotectonic uplift and sediment transport processes. Integration of core study with geomorphic analysis serves to differentiate the impact of natural from human-induced factors. Our investigation highlights the extent to which the Alexandria region has been influenced by man, and reveals that anthropogenic factors have become a dominant controlon depositional systems and coastal plain evolution. Combined effects of natural (primarily sea-level rise and neotecton­ ism) and human-induced phenomena (e.g., wetland loss and severe pollution) are inducing changes which threaten this low-lying area. Geologic and geomorphic analyses provide information that is essential to effective coastal management of the Alexandria region.

ADDITIONAl..INDEX WORDS: Abu Qir lagoon, Alexandria, Carbonate ridges, Maryut lake, Neotec­ tonisrn, Nile delta, Paleogeography.

INTRODUCTION of time-slice paleogeographic maps are generated This study is a sedimentologic-lithostrati­ for the Alexandria region on the basis of these graphic investigation of subsurface depositional lithofacies distributions. sequences of late Pleistocene to Recent age in the There have been more than 100 published stud­ Alexandria region of Egypt (Figure 1). The in­ ies that consider geological, geochemical, geo­ vestigation is part of along-term geologic pro­ graphical and environmental aspects of the Al­ gram, initiated at the Smithsonian Institution in exandria region (many are cited in this article). 1985, to define the late Quaternary to Recent evo­ Our study, however, is the first systematic and lution of the entire northern Nile delta. Study of comprehensive investigation of subsurface se­ radiocarbon-dated sediment borings and system­ quences, and also the first detailed paleogeo­ atic mapping of subsurface sequences are an in­ graphic analysis of the Alexandria and Maryut tegral part of the ongoing program to evaluate lake region. Moreover, this study evaluates the changes in the coastal region of Egypt through origin and early history of Maryut lake, the major time. Herein, petrologic and faunal analyses serve coastal water body to the south and west of Al­ to define major subsurface lithofacies and sedi­ exandria (Figure 1), and attempts to define the mentary environments in the study area, and core­ boundary between the delta to the east and the to-core correlations of dated sections depict litho­ desert coastal plain to the west. facies distributions in time and space. A series Comparable investigations of the late Quater­ nary evolution of adjacent Nile delta regions, also based largely on analysis of radiocarbon-dated 92075 received and accepted 26 August 1992. sediment cores, have been carried out to the east Evolution of the NW Nile Delta 27

..l/~• ...... r------'------"""-----~------....., Mediterranean Sea

~"".... Drain and canal ~ Railway ~ Maryut lake

20

• 5-85 Smithsonian core (this study)

• S-74 Smithsonian core (Chen et al., 1992)

A E-3 Engineer core Arab.' Gulf xA..1 Published well description (Attia, 1954)

Figure 1. Map of the Alexandria region showing prominent geographic features and position of sediment cores used in this study. Inset map demarcates general locations of comparable Smithsonian Nile Delta Project studies to the east: (1) Coutellier and Stanley (1987), (2) Stanley et al. (1992), (3) Arbouille and Stanley (1991), and (4) Chen et al. (1992).

(COUTELLIER and STANLEY, 1987; ARBOUILLE and population growth and severe pollution (cf. STANLEY, 1991; STANLEY et al., 1992; CHEN et al., EL-WAKEEL and WAHBY, 1970; EL-WAKEEL and 1992). These companion studies (Figure 1, inset) EL-SAYED, 1978; SAAD, 1983a,b; EL-RAYIS et al., have demonstrated that, as in the case of most 1986; ELSOKKARY, 1989; and ABDUL DAHAB et al., delta shorelines (cf. BROUSSARD, 1975; COLEMAN, 1990). Interpretation of radiocarbon-dated cores 1982), modifications in the northern Egypt coast provides the most effective means to differentiate through time have been induced by eustatic sea­ the effects of natural from human-induced factors level and climatic oscillations, subsidence (com­ that control lithofacies distribution and coastal paction, isostatic depression, neotectonism) and development. OUf analysis was initated to provide sediment transport processes. Previous studies vital information for preparation and implemen­ have shown that, in addition to these natural phe­ tation of effective plans to help protect and re­ nomena, man has affected profound physiograph­ mediate the low-lying Alexandria region. ic and ecologic transformations on the northern Egypt coast. Anthropogenic alterations include METHODOLOGY land reclamation, agricultural, aquacultural, ir­ Fourteen Smithsonian sediment cores, collected rigation and industrial projects (BUTZER, 1976; during a 1990 field expedition (Figure 1), were WATERBURY, 1979). analyzed in this study. These 7.5 em diameter In addition to interpretation of the late Qua­ cores, recovered using a trailer-mounted rotary ternary evolution of the Alexandria region, the percussion (Acker-2) drilling rig, range in length major goal of the present investigation is to pro­ from 10 to 45 m and are spaced ---4 to 16 km vide necessary data to monitor ongoing and future apart. Cores were collected as continuous sections changes in the northern coastal region of Egypt. where sediment was cohesive, and as washings (by Alexandria, highly industrialized and Egypt's circulating water) where sandy and noncohesive. largest port, must come to terms with exponential Nine of these cores (S-77 to 8-85) were analyzed

Journal of Coastal Research, Vol. 9, No.1, 1993 28 Warne and Stanley during the course of this study (Figure 1); the bonate sands, and carbonate desert coastal sands; other five cores (S-72 to S-76) were examined in and (2) Holocene fluvially-influenced and marine­ a previous investigation (CHEN et al., 1992). In influenced lagoon deposits. addition, lithologic logs of six engineering borings Distinct molluscan fossil assemblages have been (E-l to E-6) and one published log (A-l in ATTIA, shown to be representative of specific range of 1954) are incorporated into the subsurface data­ marine conditions and water depths in the Med­ base. Moreover, other published lithologic logs iterranean region (DI GERONIMO and ROBBA, 1976), (FOURTAU, 1896, 1915; ATTIA, 1954; SAID, 1981; including the Nile delta (BERNASCONI ei al., 1991). SESTINI, 1989) were consulted for this study. In this study, molluscan paleocommunity analysis Each Smithsonian core was systematically split was performed (M.P. BERNASCONI, written com­ and macroscopic features such as general lithol­ munications, 1991, 1992) on 24 samples from nine ogy and color, hardness, stratal boundaries, sed­ cores (S-7~3, S-75, S-77, S-78, S-79, S-80, S-82, imentary structures, fossil content, root traces and S-8;3, S-84) to more precisely define the environ­ other features were recorded. All core sections ments of deposition for the sampled intervals. Pa­ were x-radiographed for detailed examination of leocommunity analysis is particularly useful in sedimentary structures and traces of plants and differentiating among brackish water bay, ma­ organisms (cf. method of COUTELLIER and rine-influenced lagoon and fluvially-influenced la­ STANLEY, 1987). From the fourteen cores, 444 goon facies. samples were collected for petrographic analysis Following the procedure described above, the at each lithological boundary, or at less than 1 m various late Quaternary lithofacies were distin­ intervals in the case of thick homogeneous sec­ guished for each boring. Core-to-core correlations tions. An additional 47 samples were radiocarbon were then established, taking into account avail­ dated (using total organic matter, plants and/or able radiocarbon ages. These correlations high­ shell); of these, 31 provided viable ages to estab­ light lithofacies distributions (and associated en­ lish a chronostratigraphic framework. vironments of deposition) in time and space. A Size analysis was performed on the 444 petro­ series of time-slice paleogeographic maps, based logic samples to determine proportions of clay primarily on facies distributions, was then com­ «2 um), silt (2-63 ,urn) and sand (>63 um). The piled. All relevant information is recorded in ME­ average size (very fine, fine, medium, coarse, very DIBA (1992). coarse) of the sand fraction was determined for A generalized geomorphic-land use map (Fig­ all samples by comparing these samples (under a ure 2) of the Alexandria region was compiled to reflected light microscope) to sand-size standards better relate present-day sedimentary environ­ in a Grain Sizing Folder (©Forestry Suppliers ments to sub-recent and modern coastal process­ Inc.). Such sand-size analysis has proved to be es, and also to record the profound impact of man particularly useful to differentiate marine-influ­ on this densely populated and highly industrial­ enced lagoon from brackish water bay deposits ized region. This map was compiled primarily from (cf. CHEN et al., 1992). Landsat-5 Satellite Thematic Mapper images Petrographic analysis (ef. method of COUTEL­ (bands 3, 4, 5, 7) which were taken during a survey LIER and STANLEY, 1987) of the sand-size fraction in December, 1986, and published by IWACO was used to distinguish the major sedimentary (1989; scale 1:100,000). Additional information was facies. Relative percentages of 18 sand-size com­ obtained from topographic (U.S. DEFENSE MAP­ ponents were calculated from point counts of > 300 PING AGENCY, 1961, 1973, 1975, 1977; scale grains for the 444 samples (method of FRIHY and 1:50,000) and other pertinent maps (AR­ STANLEY, 1988). Counted components include: 9 ROWSMITH, 1802, 1807; JACOTIN, 1818; SHATA, 1958; mineralogical (light and heavy mineral, mica, ver­ EL-SAMI, 1960; EL FAYOUMY et aZ., 1975; FRIHY dine/glauconite, pyrite, gypsum, lithic fragment, et al., 1988; CHEN et al., 1992). Geomorphologic undefined carbonate particle and carbonate ag­ features of the Alexandria region were observed gregate); 6 faunal (indeterminate shell fragments, during 1990 and 1992 Smithsonian field expedi­ foraminifera, ostracod, gastropod, pelecypod and tions. sponge); and 3 floral (diatom, plant fragment and Bathymetric (Figure ~3) and topographic (Fig­ seed). This method is particularly useful for dif­ ure 4) maps of the region were compiled to better ferentiating (1) late Pleistocene siliciclastic allu­ characterize the sedimentary and tectonic set­ vial plain sands, deltaic siliciclastic to coastal car- tings of this region which comprises the transition

Journal of Coastal Research, Vol. 9, No.1, 199a Evolution of the NW Nile Delta 29

o 10 20

---kilometers I

Coast Anthropogenic Features Lowland Oolitic beach and Urbanized and industrialized ~ Predominantly open water lake beach ridge (Ridge I) m iii Causeway ~ Marsh with abundant floating thickets Siliciclastic sand flat ofPhragmites and other plants Landfill and sewage disposal area, • ~ Inland former lake E:;j Sabkha and playa, isolated by causeways ~ Road Carbonate ridge with ~ Sabkha and alluvial fan with abundant well developed caliche ~ Railway loess and gypsum (Ridges II, III, IV) Intensely cultivated ...• ~.... Drain and canal D and irrigated Fish farm, former lake r:::-:1 Scmidcsert, converting to l:.:.:..:J agricultural and residential Commercial salt pond, ~~~~~ former lake § Scmidcscrt, mostly ~ military base Former lake and lagoon, • Ridge I Ridge III I Possible drained and cultivated If.] Kom ~ Ridge II • Ridge IV fault

Figure 2. Geomorphic-land use map of the study area. Primary source of data is Landsat-5 Satellite Thematic Mapper images taken in a December 1986 survey (lWACO, 1989). Diversity of geomorphic features reflects (1) the transition from Nile delta plain to the east and desert coastal plain to the west, and (2) profound influence of human activity. Descriptions of various geomorphic features is given in text. Inset map shows eastern portions of late Pleistocene carbonate ridges, and position of possible fault (Butzer, 1960). from deltaic to desert littoral environment. These andria region can be subdivided into a series of maps were compiled from documents of the U.S. distinct geomorphic areas, including beach, car­ DEFENSE MAPPING AGENCY (1961, 1973, 1975, 1977, bonate ridge, inland depression, drain and canal, 1985, 1990; scale 1:50,000) and SHAFEI (1952). kom (low hill), semidesert, reclaimed lagoon and irrigated farmland. The coastline between Abu DESCRIPTION OF THE STUDY AREA Qir and EI Dekheila is characterized by alternat­ The study area parallels the SW-NE oriented ing small bays and pocket beaches which are sep­ coast for a distance of -.,70 km, and extends -.,20 arated by headland points and small islands km inland. It is located at the western edge of the (SHUKRI and PHILLIP, 1956). In contrast, the coast Abu Qir Bay and includes the northwestern sector from EI Dekheila to Abu Sir (and further west) of the Nile delta (HILMY, 1951; SHUKRI and PHIL­ is characterized by broad white, carbonate beach­ LIP, 1956; STANLEY and HAMZA, 1992). This coast­ es. Maryut lake, a shallow brackish water body al region lies at the eastern end of Arabs' Gulf with no direct connection to the sea has been (Figure 1, inset) and includes the eastern portion artificially divided into > 9 sub-basins by cause­ of the Western Desert coastal zone. The Alex- ways and canals, and is heavily polluted by un-

Journal of Coastal Research, Vol. 9, No.1, 1993 1 30 Warne and Stanley

D Landandlagoon o Submerged archeologicsites C3 0-5mBMSL em 5-10mBMSL BMSL =Below mean sea level III 10-20 m BMSL ~ 2D-30mBMSL o 10 20 / ~ >30mBMSL -=- km

Figure 3. Bathymetric map of the Alexandria nearshore region. Primary source of data is U.S. Defense Mapping Agency (1985, 1990). Submerged features and archeological sites are discussed in text. treated sewage and industrial wastes. Other dis­ al., 1978; STOFFERS et al., 1980). Several small tinctive geomorphic features of the study area islands, remnants of a carbonate ridge, dot the include a series of shore-parallel carbonate ridges nearshore between Abu Qir and El Agami (to >40 m elevation); these are separated by de­ (EL-SAYED, 1988a). BUTZER (1960) and pressions which contain shallow lagoons and sab­ EL-WAKEEL and EL-SAYED (1978) described a se­ khas. Large portions of the study area lie below ries of bathymetric highs -..1-1.5 km offshore that sea level (Figure 4) and thus are particularly vul­ parallel the present shoreline. EL- WAKEEL and nerable to marine inundation. EL-SAYED (1978) considered these to mark an an­ The Alexandria region has a long record of hu­ cient shoreline which has subsided below sea level. man habitation, dating back to pre-dynastic times. At a resolution of 5 ill, the bathymetry shown in By 5,000 years BP, herdsmen had migrated to the Figure 3 does not reveal this submarine feature. Mediterranean coast as the climate of western Sediments along the coast are polluted by un­ Egypt became more arid and the former grass­ treated seawater, industrial waste and contami­ lands converted to desert (DE COSSON, 1935; nation related to the shipping industry (AB­ BUTZER, 1976). The earliest historical record dates DEL-MoAT! and EL-SAMMAK, 1988; ABOUL DAHAB, back to -..3400 BC when the region was known as 1988). Kingdom of the Harpoon (the harpoon was used Oolites of Arabs' Gulf have been interpreted by for catching fish in Lake Mareotis), Historic rec­ some to be relict sediments which formed during ords indicate that Lake Mareotis (predecessor of warmer periods of the late Quaternary (ANWAR Maryut lake) was a fresh water lake, which was et al., 1981). Petrographic analysis by ALEX­ deeper and of greater aerial extent than at present ANDERSSON (1990), however, suggests that ooli­ (DE COSSON, 1935). The history of Lake Mareotis zation may he in progress at present. is discussed in more detail in a later section. Coastal Area Marine Shelf The coast, especially at Alexandria and EI Aga­ The nearshore marine shelf is primarily com­ mi, is the principal seaside resort in Egypt, sea­ posed of sand which is fine and siliciclastic in the sonally attracting millions of vacationers. Com­ east, and coarse and carbonate-rich in the west plete modification of segments of the coastline, (EL-WAKEEL and EL-SAYED, 1976, 1978; EL-SAYED, from Alexandria to El Agami, has resulted from 1979, 1988c). Textures grade from sand near the rapid construction to house the fast-growing pop­ coast to muddy silt 5-8 km offshore (EL WAKEEL ulation and to accommodate industry and ship­ and EL-SAYED, 1978, their Figure 3). The middle ping at Egypt's principal port. shelf is primarily composed of skeletal and pel­ On the basis of geomorphology and sedimen­ loidal carbonate sand and mud (SUMMERHAYES et tology, the coast from western Abu Qir bay to the

Journal of Coastal Research, Vol. 9, No.1, 1993 Evolution of the NW Nile Delta 31 ;I

• >40 m AMSL § 0-3 m BMSL mean sea level CEJ 20-40 m AMSL S >3 m BMSL .10-20mAMSL BMSL =Below mean sea ~ 5-10mAMSL 0 10 20 level I ••

Figure 4. Topographic map of the Alexandria region. Primary source of data is U.S. Defense Mapping Agency (1961, 1973, 1975, 1977). This map highlights (1) the large land surface below sea level, including former Lake Mareotis, and (2) physiographic expression of the transition between the low-lying Nile delta plain to the east and carbonate ridges of the coastal plain to the west. Topographic features are discussed in text.

ruins at Tapasiris (Abu Sir) can be subdivided The ~30 km of coastline between Abu Qir and into four zones: western Abu Qir bay; Abu Qir­ EI Dekheila is characterized by small bays sepa­ El Dekheila coast; Alexandria harbor district; and rated by capes and small islands (Figure 5A). Sea EI Dekheila-Tapasiris coast (cf. HILMY, 1951; cliffs (to ---5 m) are common along this coast and SHUKRI and PHILLIP, 1955; PHILLIP, 1976; form as waves erode carbonate coastal ridges. EL-WAKEEL and EL-SAYED, 1978). These four Along this portion of the coast, sandy beaches are coastal zones are described below, from east to generally narrow and are best developed in small west. bays (Figure 5A). Many of these beaches are now The siliciclastic beach and sand fiat south of artificially replenished with sand. Carbonate con­ AbuQir extends for ---7km along the westernmost tent, mostly in the form of shell and shell frag­ portion of Abu Qir bay (Figure 2). This coastal ments, increases markedly westward, from --- 36 CJ~ sector is primarily composed of very fine to me­ at Abu Qir to ---99~';) at EI Dekheila (HILMY, 1951). dium quartz sand (CHEN et al., 1992). Micas, heavy In contrast, proportions of quartz and heavy min­ minerals and mollusc shells are common accessory erals decline westward, reflecting the diminished components. The relative proportion of carbonate influence of the River Nile on this geomorphic increases northward towards the carbonate ridge province (HILMY, 1951; SHUKRI and PHILLIP, 1955). at Abu Qir. The sand fiats are generally <1 m The sands from Abu Qir to Sidi Bishr (Figure 1) above mean sea level, but intermittent dunes reach are generally fine to medium, whereas the sands 2 m in elevation (EL FAYOUMY et al., 1975). These from Sidi Bishr to EI Dekheila are generally coarse low-lying sand flats extend 0.5-0.75 km inland. (EL-WAKEEL and EL-SAYED, 1978). The boundary

Journal of Coastal Research, Vol. 9, No.1, 1993 32 Warne and Stanley

Figure 5. Ph otograph s of selected geomorphic and sedi mentologic features in the study area. (A) carbon ate Ridge II formin g small cape and pocket beach at Mun taza h park , between Alexandria and Abu Qir (view toward north ). (B) roadcut thro ugh Ridge II bet ween Borg el Arab and coast, near Abu Sir (Tapas iris); elevation of ridge crest -35 m (view northw est toward Arabs' Gulf). (C) Ridge II quarried for building stone at Sidi Barakat , southwest of Alexandria; note large-scale bedding (ridge crest -30 m). (D) Mallahet Mar yut depr ession between Ridge II (Tapasiris archeologic site in foregrou nd) and Ridge III in distance (view toward southwest). (E) dr iller at core site S-85 (between Ridges II and III ) near Borg el Arab , recoverin g carbonate sands which produce char acteristically white drilling fluids. (F) cultivate d field in former Abu Qir lagoon near Abu Qir bay coast; note date palm s on raised sand barrier (view toward eas t) . (G) view of EI Umoum drain, which traverses and subd ivides Maryut lake (view from Desert road toward sout heast). (H) cau seway traversing sout hweste rn sub-basin of Maryut lake, near core site S-82; carbonate Ridge III in background (view toward west) . (I) commercial salt pond (crusts in white) in west-ce ntral sub-basin near core site 8- 83; facto ries of western EI Agam i in backgroun d (view toward northeas t).

Jo urnal of Coastal Resea rch, Vol. 9, No. I, 1993 Evolution of the NW Nile Delta 33

Figure 5. Continued. between the Nile delta and the Western Desert age (DOWIDAR and ABOUL KASSIM , 1986; EL-RAYIS coast occurs in this region (STANLEY, 1989, his et al., 1986). Figure 4). In contrast to the irregular coastline in the There are two principal harbors along the Al­ northeastern study area, the 40 km stretch from exandria coast: the Eastern and Western harbors El Dekheila to Tapasiris is characterized by (Figure 2). These two adjacent harbors are pro­ straight, carbonate-rich sandy beaches of variable tected from the sea to the north by remnants of width. These beaches are backed by dune ridges a limestone ridge (formerly Pharos Island) and which, in their natural state, are driven landward man-made jetties. The two harbors were once a by dominant southeast-directed winds. The sands single water body, but were divided by a causeway along this stretch of coast are medium-grained, which was constructed by order of Alexander the well sorted and well rounded (HILMY, 1951). The Great (JONOET, 1916; MORCOS, 1985). The West­ carbonate content is high (>99%) whereas quartz ern harbor covers -31 km 2 and has an average and heavy minerals are found only in trace depth of -7 m. This harbor handles -90% of the amounts; the heavy minerals generally comprise foreign trade of Egypt. Because it is a semiclosed the more stable varieties (SHUKRI and PHILLIP, basin, the only significant sediment source is un­ 1955; EL-WAKEEL and EL-SAYEO, 1978). Ooids and treated sewage and industrial waste (EL-SAYED et coated grains make up 85 % of the carbonate frac­ al.,1988). The harbor bottom is covered by highly tion; shells and shell fragments constitute most polluted, dark gray to black, organic-rich mud of the remainder (STANLEY and HAMZA, 1992). (EL-WAKEEL and EL-SAYEO, 1978). The Eastern harbor covers -25 km2 and averages -6 m in Carbonate Ridges depth . This semiclosed basin is covered by grayish The western portion of the study area is char­ black to black sandy silts (EL-WAKEEL, 1964) and acterized by a series (perhaps as many as 8-10) currently receives large volumes of untreated sew- of elevated carbonate ridges of late Pleistocene

Journal of Coastal Research, Vol. 9, No.1, 1993 34 Warne and Stanley age. These ridges extend westward, some for> 100 much as 10 m above mean sea level in the western kill, parallel to the present coast. These ridges part of the study area, but decreases markedly in progressively increase in elevation from --10 m at elevation and disappears just east of EI Agami the coast to --100 m some 40 km inland (ZEUNER, (Figure 2). Extensive, ongoing construction has 1950; SHUKRI et al., 1956). The eastern terminus completely modified Coastal Ridge I in the Agami of all ridges is in the Alexandria region (BUTZER, region. To the west, where undisturbed by man, 1960, his Figure 1). Their termination has been the upper surface is partially covered by coastal attributed to downwarping under the weight of and dune plants, and is fronted by beaches of the Nile delta sediment load (HASSOUBA, 1980; ct. variable widths which are also composed of white SAID, 1981), and faulting (BUTZER, 1960). oolitic sands. These back-beach dunes are dis­ There are several interpretations as to environ­ placed by dominant southeast directed winds, and ment of deposition of the late Pleistocene ridges: thus are migrating to the southeast. In places, some studies concluded that the three northern­ these coastal dune sands have infilled the de­ most ridges are shallow marine deposits such as pression between Ridges I and II, resulting in a offshore bars (FouRTAu, 1893; BLACKENTHORN, series of discontinuous sabkhas and playas. 1901, 1921; ZEUNER, 1952; SHUKRI et al., 1956; Oolitic sands in the upper portion of Coastal SAID et al., 1956; BUTZER, 1960; ISMAIL and SELlM, Ridge I are interpreted to have originally formed 1969; CHERIF et al., 1988), whereas others consider on the shelf in Arabs' Gulf. These shallow shelf these ridges to be of nonmarine coastal dune or­ sands were then transported onto the beach by igin (HUME, 1912; HUME and HUGHES, 1921; HUME marine waves and currents, and then onto the and LITTLE, 1928; BALL, 1939; SANDFORD and AR­ ridge by southeast-directed winds. A late Mon­ KELL, 1939; PICARD, 1943; SCHWEGLER, 1948; asterian age has been attributed to these deposits HILMY, 1951; PAVER and PRETORIUS, 1954; SHATA, (SHUKRI et al., 1956; CHERIF et al., 1988). 1955). However, in light of evidence from a recent trench across a ridge near Bahig (Figure 2), some Abu Sir Ridge II authors concluded that this ridge is of both ma­ Abu Sir Ridge II is almost parallel to and land­ rine and eolian origin (HASSOUBA, 1980; HASSAN ward of Coastal Ridge I (Figure 2, inset), and et al., 1986). It has been suggested that the ele­ extends from Abu Qir westward to the town of EI vation of carbonate ridges records successive late Sallum, near the Egyptian-Libyan border. Abu Pleistocene sea level stands (SHUKRI et al., 1956; Sir Ridge II limestones have been classified as HASSAN et al., 1986). However, some studies con­ mostly ooid-coated grain-bioclastic grainstones clude that, over time, these and related carbonate (STANLEY and HAMZA, 1992). The relative pro­ ridges around the Mediterranean Sea have been portion of quartz and other insoluble residue is elevated by tectonic processes (EL RAML Y, 1968; very high in the northeast ("-'76 ~~)) but decreases HEY, 1978; NEEV et al., 1987). markedly to the southwest (STANLEY and HAMZA, In the present study, the three northernmost 1992). Allochems are primarily ooids, coated grains ridges are termed Coastal Ridge I, Abu Sir Ridge and algae (STANLEY and HAMZA, 1992). In the II and Gebel Maryut Ridge III (Figure 2, inset), walls of quarries, these grainstones commonly dis­ and are briefly described below. play high angle, unidirectional (to the southeast), large-scale, planar cross bedding. Thin calcrete Coastal Ridge I crusts (2-15 cm thick) occur irregularly through­ Coastal Ridge I parallels the shore from Alex­ out the ridge sequence; these suggest intermittent andria westward to about 30 km east of the Libyan subaerial exposure of the ridge deposits and sub­ border. Along its entire extent, the carbonate con­ sequent meteoric diagenesis (EL-SHAHAT et al., tent exceeds 98.5 c;C} and is classified as an ooid 1987). The elevation of this cream colored lime­ grainstone (STANLEY and HAMZA, 1992). Acces­ stone ridge averages about 35 m in the western sory components include fossils ofalgae, molluscs, part of the study area (Figure 5B), and decreases foraminifera and micritic carbonate particles; eastward to 6 ill at Abu Qir. The city of Alexandria quartz is rare to absent. Ridge I is commonly cross­ is built upon this ridge. It is quarried in the west­ laminated, in which foresets trend dominantly to ern part of the study area, primarily for building the southeast. Coastal Ridge I is composed of stone and cement (Figure 5C). In the western por­ white, well sorted, medium-grained, loose to light­ tion of the study area there is little soil or vege­ ly cemented, carbonate sands. This ridge is as tation along the ridge crest, and a caliche crust is

-Iournal of Coastal Research, Vol. 9, No.1, 199:3 Evolution of the NW Nile Delta 35 well developed. Flanking both sides of the ridge dose gypsum nodules are currently forming in the are extensive alluvial fans of poorly sorted, weath­ two northernmost depressions (Depressions I and ered Ridge II sediment. This ridge has been as­ II of ALl and WEST, 1983). These two northern­ signed a "main Monasterian" age in some studies most depressions are briefly discussed below. (BLACKENHORN, 1921; SHUKRI et al., 1956; CHERIF, 1988). EI Dekheila-Abu Sir Depression I The El Dekheila-Abu Sir Depression I between Gebel Maryut Ridge III Coastal Ridge I and Abu Sir Ridge II, is narrow Gebel Maryut Ridge III lies south of, and par­ (0-0.5 km) and discontinuous. In places, Coastal allel to Abu Sir Ridge II. In the study area these Ridge I has expanded southeastward and infilled two ridges are separated by a 8 to 4 km-wide Depression I, which has resulted in a series of depression occupied, in part, by the western ex­ isolated playas and sabkhas. The upper 1 to 2 m tension of Maryut lake. The yellow to light-brown of Depression I sediment consists of ooid-bearing Ridge III changes from mostly quartz-rich car­ calcareous silt (loess) with abundant gypsum nod­ bonate sandstones in the northeast to mostly bio­ ules. These nodules are forming at the present clastic grainstones in the southwest (STANLEY and time (WEST et al., 1979; HASSOUBA, 1980; ALI and HAMZA, 1992). Ridge III is fossil-rich and char­ WEST, 1983). These gypsiferous silts are underlain acterized by a diverse faunal content (STANLEY by gray shelly silts oflagoon origin (ALIand WEST, and HAMZA, 1992). True ooids are absent. The 1983). The sabkha surface is 0 to 1 m above sea elevation of Gebel Maryut Ridge III ranges from level. The surface is flat and partially vegetated 20 to 40 m. As in the case of Ridge II, there is with halophytic shrubs. In summer the surface is little soil or vegetal cover along the crest, and a dry and capped by a 2 mm crust of silt cemented caliche crust is well developed. Flanking both sides by halite and gypsum (ALI and WEST, 1983). In of the ridge are extensive alluvial fans of poorly winter (depending on the amount of rainfall) the sorted Ridge III sediment. depression is partially filled with water. Just west Studies of a large trench cut across Ridge III of El Agami, sectors of this depression have been near Bahig (Figure 2) have lead recent workers to artificially infilled (with Ridge I sands) for com­ conclude that this ridge formed under a wide va­ mercial and residential use. riety of conditions ranging from marine to eolian (HASSOUBA, 1980; HASSAN et al., 1988; STANLEY Mallahet Maryut Depression II and HAMZA, 1992). Several well developed paleo­ The Mallahet Depression II, situated between sols are interbedded with Ridge III marine car­ Abu Sir Ridge II and Gebel Maryut Ridge III, is bonates; these interbedded marine and subaerial continuous and generally between 3-4 km wide deposits record several cycles of su bmergence and (Figure 5D and E). The surface of this depression emergence during the course of ridge develop­ descends to more than 3 m below sea level (Fig­ ment (HASSAN et al., 1986). Previous studies have ures 2, 4). Until the twelfth century, AD, this assigned a late Tyrrhenian age to these deposits depression served as the western branch of Lake (SANDFORD and ARKELL, 1939; SHUKRI et al., 1956; Mareotis (DE COSSON, 1935). Presently, Depres­ CHERIF et al., 1988). sion II is artificially segmented into several sub­ basins by causeways and canals (Figure 2). Mal­ Inter-ridge Depressions lahet Maryut Depression II is discussed further The shore-parallel carbonate ridges are sepa­ in association with the Maryut depression. rated by a series of elongate depressions. The floor of successive depressions increases in elevation to Maryut Depression the south (Figure 4). The depressions are gener­ Maryut, which covers --90 km", is presently the ally covered by brown, calcareous clayey loess smallest Nile delta coastal brackish water body (HASSOUBA, 1980; ALI and WEST, 1983). Beneath (Figure 2). Unlike the other three Nile delta la­ the loessic cover are calcareous and gypsiferous goons, Maryut has no direct connection to the sea, clayey silts which have been interpreted to have and therefore is herein referred to as Maryut lake accumulated in shallow lagoons and sabkhas (SAID (as opposed to Maryut lagoon). Maryut lake sur­ et al., 1956; HASSOUBA, 1980; HASSOUBA and SHAW, face is currently maintained at 2.8 m below mean 1980).These sediments are locally mined for gyp­ sea level by pumping water from the lake to the sum to the south and west of the study area. Va- sea at EI Max. With present water depths up to

Journal of Coastal Research, Vol. 9, No.1, 1993 36 Warne and Stanley

1.5 m and lake levels at 2.8 m below sea level, the same century and Alexandria declined in impor­ floor of Maryut lake extends to as much as 4.3 m tance. El Mahmudiya canal was rebuilt by Mo­ below sea level, appreciably lower (by nearly 3 m) hamid Ali Pasha in 1820 and once again Alex­ than other northern Nile delta lagoons. andria became a principal city of Egypt. The canal Because of the artificially low lake levels, Mar­ currently supplies the Hydrodrome with water. yut lake occupies a fraction ('"-' 13 C;~)) of an exten­ The course of the EI Mahmudiya canal through sive subsea-level depression which is herein re­ downtown Alexandria is now dry, although it is ferred to as Maryut depression (Figure 4). The still recognizable on satellite images (Figures 1, remaining 87 ~~() of the depression has been drained 2). and is now used primarily for agriculture (Figure El Qalaa drain is a branch of EI Mahmudiya 2). Modern Maryut lake, subdivided into more canal and receives large amounts of industrial than nine sub-basins by causeways and canals wastes from the Alexandria region. It is the prin­ (Figures 5G and H, 6), is heavily polluted and cipal source of water (and also pollutants) for partially eutrophic. Maryut lake and its prede­ Maryut lake. cessor, Lake Mareotis, will be discussed in detail EI Umoum drain receives agricultural runoff in a later section. from the Beheirah Governate (Figure 5G). Its wa­ ters are less polluted than those of EI Qalaa drain Former Abu Qir Lagoon (EL-RAYIS and SAAD, 1986). A series of breaks Former Abu Qir lagoon occupied '"-' 105 km 2 in along its embankments allows the canal water to the region just east of Alexandria and south of mix with that of Maryut lake. Water is pumped Abu Qir city (Figures 2, 5F). This low-lying region from this drain at EI Max to maintain Maryut was wetland until as late as the early nineteenth lake at 2.8 m below sea level (ALEEM and SAMAAN, century (ARROWSMITH, 1802, 1803; JACOTIN, 1818; 1969a). FOURTAU, 1896). Although drained and intensely EI Noubariya canal is the major water way in cultivated, the former lagoon is still discernable the westernmost Nile delta, and serves as a prin­ on satellite images. The eastern margin of this cipal artery for shipping barges in the Alexandria subsea-level depression is separated from the coast region. The canal has been polluted with tin from by narrow (0.5-0.75 km) coastal sand fiats (Fig­ antifouling agents used in paints which are ap­ ures 2, 4, 5F). plied to barges using this canal (ABDUL DAHAB et al., 1990). The West Noubariya canal, more re­ Canals and Drains cently constructed, is also used for barge traffic. An extensive network of irrigation canals covers large portions of the southeastern sector of the Korns and Tells study area (U.S. DEFENSE MAPPING AGENCY, 1961, Several hills, referred to as karns or tells, are 1975,1977). The southwestern portion of the area conspicuous features in the depression between is less extensively cultivated, but irrigation proj­ carbonate Ridges III and IV and are readily rec­ ects are expanding into that region. EI Mahmu­ ognized on aerial photographs and satellite im­ diya, El Qalaa, EI Umoum, EI Noubariya and West ages (Figure 2). These hills, largely composed of Noubariya canals and drains, the principal inland fine and medium sand and silt, characteristically waterways in the study area, are briefly discussed contain abundant artifacts which have proven to below (Figures 1, 2). be of great value to archeologists working in this To the east of the study area, EI Mahmudiya region (RODZIEWICZ, 1984). DE COSSON (1935) de­ canal follows the course of the former Canopic scribed the two koms near Bahig (Figure 2) as channel, once a major distributary of the River "artificial mounds". Nile (TOUSSON, 1992; CHEN et al., 1992). Even before the arrival of Alexander the Great in 332 Arable Lands Be, EI Mahmudiya canal (formerly the Alexan­ Low-lying arable lands of the study area make dria canal) had been constructed to supply small up the northwestern sector of the fertile Nile cres­ villages of the region with drinking, bathing and cent. Construction of the Aswan High dam in 1964 irrigation water (DE COSSON, 1935). When the Ca­ brought an end to annual floods in the delta, and nopic channel silted up in the twelfth century, EI to the influx of large volumes of nutrient-rich sed­ Mahmudiya canal was extended to the Rosetta iments carried by the flood waters (SHARAF EL branch. However, the canal silted up during the DIN, 1977). These sediments were not only im-

Journal of Coastal Research, Vol. 9, No.1, 199~ Evolution of the NW Nile Delta 37

o 10 ---kilometers ~ Western sub-basin • Centra) sub-basin ~ Southern sub-basin rn Southeastern sub-basin [ill Small. undescribed sub-basins ~ West-cen1ral sub-win E±J Southwestern sub-basin § East-central sub-basin

Figure 6. Map showing artificial sub-basins of present-day Maryut lake. Sub-basins are separated by canal embankments and causeways. Inset map shows four Maryut sub-basins as described by several authors (cf. Aleem and Samaan, 1969a). portant for keeping the soil nutrient rich, but also suggested that climate in the region has become for maintaining the balance between sediment in­ drier during the past 1,200 years, although vari­ put, land subsidence and sea-level rise. Without ations have been reported (BELL, 1970; HASSAN, sediment input, ongoing sea level rise and sub­ 1981; RIEHL and MEITIN, 1979). The Alexandria sidence will make the region vulnerable to inun­ coastline is microtidal along which waves, ap­ dation by the sea. The study area is especially at proaching from the northwest, drive marine cur­ risk because large portions of the arable land are rents and sediments to the east and northeast. reclaimed lake and lagoon which already lie below These marine currents prevent Nile siliciclastics sea level (Figures 2, 4). Therefore, significant in­ from reaching further west than the shores of crease in sea-level rise or subsidence, or breaching eastern Alexandria (STANLEY, 1989). It should be of the coastal barriers by winter storms or earth­ recalled that, until recently (closure of Aswan High quakes, may result in inundation of coastal regions dam), large volumes of Nile sediments debouched by the sea. at nearby Rosetta promontory.

Depositional Processes Affecting the Alexandria DESCRIPTION AND INTERPRETATION OF Region LATE QUATERNARY FACIES UNDP/UNESCO (1976,1977, 1978), INMAN and Subsurface lithofacies in this westernmost Nile JENKINS (1984), STANLEY et al. (1992) and CHEN delta sector were distinguished and interpreted et al. (1992) have described the climatic, fluvial by macroscopic observations of split core sections and marine conditions influencing the northern and by petrographic analyses on the sand-size Nile delta. Winds are predominantly southeast­ fraction of core samples (cf. methods of COUTEL­ directed (NAFAS et al., 1991). Wind speeds are LIER and STANLEY, 1987). Interpretation of de­ generally between 2 and 50 km per hour. Wind positional environments associated with these fa­ storms (known as "khamsin") most commonly take cies was refined by identification of molluscan place from January to April and have been shown paleocommunities ic]. BERNASCONI et al., 1991; to be effective in transporting large volumes of M.P. BERNASCONI, written communications, 1991, dust in this region (OLIVER, 1945, 1946). 1992), and by combined compositional and stained The Alexandria region receives an average of grain analysis (cf. STANLEY and CHEN, 1991). 200mm of rainfall per year, but precipitation var­ A synthesis of vertical and lateral facies rela­ ies greatly from year to year. Rains are seasonal: tionships is presented in Figure 7. Most lithofacies almost all rain occurs between December through described below have been discussed in previous February, whereas between June and August there Nile delta studies (COUTELLIER and STANLEY, 1987; is essentially none. Annual evaporation potentials ARBOUILLE and STANLEY, 1991; STANLEY et al., of 1.5m far exceed precipitation. DE CaSSON (1935) 1992; CHENet al., 1992). In addition to these, eight

Journal of Coastal Research, Vol. 9, No.1, 1993 38 Warne and Stanley

Late Pleistocene Late Plelstoeene to Holocene Holocene E:] Alluvial to shallow marine siliciclastic sands liillI Artificial fill ~ Marine-influenced ~ Drowned channel siliciclastic sands E] Tnu15gTCssive smds lagoon muds ~ Sabkha sands ~ Deltaic siliciclastic to coastal carbonate sands ____ Late Pleistocene to and silts ~ Nearshore marine -beach sands Holocene unconfonnity ['!l ~ Well cemented grainstones ~ Fluvial crevasse splay sands ~ Brackish water Ridge II carbonate sands (poorly cemented) bay muds Et:E Lagoon margin ~ fiiI LQ Nearshore marine ~ Ridge III carbonate sands (poorly cemented) muds (closed-basin) muds Flood plain muds §j Auviallv­ II North (Harbor) influenced Intra- Holocene mRood plain margin and playa stiffmuds lagoon muds unconfonnities >- "'tf~"'2 - Intra-late Pleistocene unconformities ~~ ~ 8:Z East (Abu Qir) Eustatic sea­ West (Abu Sir) level curve Central (Maryut Lake) >- "'O~"'O -o~"2 ~ ~ ~ ~ ~ Low High >- >- "'tf~-o i .a~m~~ ~:i~~~

Basal Holocene Approximate .....;.T ~ sediments ."-T:~••-'-T Scale ..... -7500 (in meters) ...~ . years B.P. ~ ~. . in east ~l~ .~.~.. ."-T .•

Figure 7. Generalized lithostratographic sections for four sectors in the study area. The various lithofacies, correlated largely on the basis of radiometric data, are related to sea-level changes during the late Pleistocene and Holocene. Generalized sea-level curve on right after Lighty et al. (1982) and Fairbanks (1989). other facies and subfacies are recognized in the termittent stiff muds (Figure 7). In the eastern present study: late Pleistocene deltaic siliciclastic part of the study area this interval consists of tan to coastal carbonate sands, carbonate-rich desert to brown quartzose sands and green to brown stiff coastal sands, cemented limestones, distal flood muds, whereas to the west, the late Pleistocene plain stiff muds; and Holocene fluvially-influ­ sequence consists of white to tan carbonate sands enced lagoon muds, lagoon margin muds, sabkha and yellow to green stiff muds (Figure 7). These silts and sands, and nearshore marine (closed­ regionally variable sand and stiff mud sequences basin) muds. The newly described facies are dis­ represent several distinct environments of depo­ tinguished from previously defined Nile delta sition along the western edge of the delta. More­ facies primarily by their higher proportion of car­ over, these late Pleistocene facies serve to define bonates. the boundary between the Nile delta to the east and the Western Desert coastal zone to the west. Late Pleistocene Sediment Types Late Pleistocene core sections, radiocarbon Alluvial to Shallow Marine Siliciclastic Sands dated at more than 12,500 years before present Yellowish brown (lOYR 5/4) to light olive gray (BP), are composed primarily of sands with in- (5Y 5/2) to olive gray (lOY 5/2), very fine- to

Journal of Coastal Research, Vol. 9, No.1, 199:3 Evolution of the NW Nile Delta 39

Late Pleistocene Holocene

A

L.te Ptelst~ne SIInda: Holocene SIInd.: B Average % Light Miner.'. Average % Light Mlnera'.

Figure 8. Isopleth map showing frequency' distributions (averaged percent calculated from sand grai~ counts) of car~onate a~d light minerals for the sand size fraction in the late Pleistocene (A and B) and Holocene, (C and D) sections. West~ard.lncrease In proportions of carbonate (and concurrent decrease in light minerals) for both the late Pleistocene and Holocene sections IS the result of diminished influence of the River Nile to the west of Alexandria.

coarse-grained, rather poorly sorted sands are Drowned Channel Sands present in the lower portions of cores 8-74 and Light brown (5YR 5/6) to moderate yellowish 8-78 in the eastern portion of the study area (Fig­ brown (lOYR 5/4), coarse- to very coarse-grained, ure 7). These sands are primarily composed of poorly sorted, generally well rounded sands form iron-stained quartz; common accessory compo­ a 29 m thick section in the lower portion of one nents include feldspar, mica, lithic fragments, core (8-73). Although the general composition of heavy minerals and shell fragments. The propor­ these sands is comparable to alluvial sands de­ tion of carbonates (shells, shell fragments and un­ scribed above, they contain 30-50 C;~) very coarse, identified carbonate particles) is generally low rounded and highly stained quartz grains, and 1­ (Figure 8A). Fauna is rather sparse, although gas­ 7 ~!-~) foraminifera. A radiocarbon date from the tropods and ostracods, usually broken tests, are stiff mud interval at the top of these sands indi­ locally present. Core sections of this facies as long cates that this facies was deposited before 12,000 as 25 m have been recovered during Smithsonian years BP. The sphericity of the grains suggests drilling expeditions (MEDIHA, 1992); several well that these sands were transported for a consid­ records reported by ATTIA (1954) indicate that erable distance, and their coarse-grained texture this facies may locally exceed 50 m in thickness. suggests that they were deposited in a major river The time of deposition of these sands cannot be channel. The presence of trace amounts of ver­ accurately dated by the carbon-14 method: dat­ dine/glauconite and foraminifera indicates that able carbonate particles in the sands are, for the this paleochannel migrated over, reworked and most part, reworked and originally formed well redeposited former shallow marine and lagoon before actual burial. However, the stratigraphic sediments. These sands are interpreted to have position of these sands between, or below, dated been deposited in the westernmost channel of the stiff mud intervals indicates accumulation before Late Pleistocene Nile alluvial system (cf. CHEN 13,000 years BP. Composition of sands indicates et al., 1992). they originated in the East African highlands, in­ cluding the headwaters of both the Blue and White Nile (cf. SHURRI, 1950; FOUCAULT and STANLEY, Deltaic Siliciclastic to Coastal Carbonate Sands 1989;HAMROUSH and STANLEY, 1990). These sands Yellowish gray (5Y 8/1) to white (N9) to dark are interpreted to be mostly alluvial deposits with yellowish brown (10YR 4/2), fine- to coarse­ intermittent shallow marine and lagoon compo­ grained, poorly sorted, carbonate-rich, lightly iron­ nents. stained sands are present in the lower portions of

Journal of Coastal Research, Vol. 9, No.1, 1993

Evolution of the NW Nile Delta 41 seven cores (S-77 to S-8~1) in the central study unidentifiable carbonate particles and carbonate area (Figure 7). These sands are composed ofvari­ aggregates. Accessory components include quartz able mixes of quartz and carbonate, in which the and gypsum. Fauna is common, especially in the proportion of carbonate increases westward (Fig­ lower portion of the interval and includes pe­ ure 8A). The carbonate fraction, ranging from "-' 10 lecypods, foraminifera, gastropods and ostracods. to 30~'~) in this facies (Figure 8A), is composed of Approximately 17 m of this facies was recovered shells, unidentified carbonate particles and car­ in S-84; ATTIA (1954) reported> 100 m of similar bonate aggregates. Carbonate aggregates are here­ "marine sand" facies in well A-I (Figure 1). Pet­ in defined to be mixtures of very fine sand-to rologic analysis indicates that these sands are silt-size broken shell, small undifferentiated car­ characteristic of Ridge II or Ridge III deposits bonate detritus and minor quartz which are bound (STANLEY and HAMZA, 1992). Their age cannot be together by carbonate cement (Figure 9F). Gyp­ accurately determined by radiocarbon tech­ sum is always present in considerable quantities niques. These sands are interpreted to be desert (5-25 ~(). Heavy minerals occur in significantly coastal deposits and record accumulation in near­ lower proportions than in the alluvial sands to the shore, beach, sabkha and dune environments along east. STANLEY and HAMZA (1992) reported small a desert coast (cf. GLENNIE, 1987). Depositional quantities of oolites from this interval. Although conditions were similar to those presently en­ light iron-staining is common, these sands are less countered along the Egyptian Western Desert stained than the correlative alluvial sands to the coast to the west of the study area (EL SHAMI et east. Fauna, although generally sparse, is pri­ al., 1971). Based primarily on the proximity of marily composed of pelecypods, gastropods, fo­ S-84 to Ridge II, these carbonate-rich desert raminifera, calcareous algae and ostracods. Core coastal sands are herein considered to be Ridge sections as long as 34 m of this facies were recov­ II sediments. ered during Smithsonian drilling expeditions. The age of these sands can not be accurately dated by Cemented Subsurface Carbonates radiocarbon techniques, because datable carbon­ Yellowish gray (5Y 7/2) to very pale orange ates in the sands were, for the most part, formed (10YR 8/2), well cemented limestones were re­ well before deposition and burial. However, the covered in borings S-84 and S-85 along the west­ stratigraphic position of these sands between, or ern extension (western sub-basin) of Maryut lake below, more reliably dated stiff mud intervals in­ (Figure 7). The limestone units in the two borings dicates a period of accumulation from "-' 16,500 to are quite different and are thus described sepa­ >39,000 years BP. We interpret these sands as rately (detailed descriptions in STANLEY and having been deposited in a transitional sector be­ HAMZA, 1992). tween the Nile alluvial plain to the east and the Yellowish gray (5Y 7/2) to medium light gray Western Desert coastal plain to the west. The (N6), medium-grained, rather well sorted and well presence of quartz and heavy minerals (particu­ cemented grainstones occur in core S-84. STANLEY larly in the east) indicates the influence of the and HAMZA (1992) determined that this unit is River Nile (cf. HILMY, 1951); whereas high pro­ composed of 87 f);;) fossils; however because these portions of carbonate and gypsum (particularly biogenetic components occur as well rounded, me­ in the west) are characteristic of desert coastal dium-grained allochems, they can only be recog­ deposits (cf. EL SHAMI et al., 1971; GLENNIE, 1987). nized as fossils by microscope examination. Detailed petrographic analysis of these sands in­ STANLEY and HAMZA (1992) determined that this dicates they are similar in composition to the east­ unit is composed of 39lJ~ algae and 25lJo forami­ ernmost portions of Ridges II and III (STANLEY nifera with minor amounts of gastropods and and HAMZA, 1992). echinoids; ooids are a significant accessory com­ ponent. The insoluble residue (quartz, etc.) of rep­ Desert Coastal Carbonate-rich Sands resentative samples comprises < 2 cp~ of the sands. Yellowish gray (5Y 8/1) to pinkish gray (5YR This unit appears massive both in plain light and 8/1) to white (N9) rather poorly sorted, lightly in x-radiographs. This interval is 1 m thick in core cemented, medium- to coarse-grained, carbonate S-84. Radiocarbon analysis suggests that this unit sands were recovered in the lower portions of one is >40,000 years BP. STANLEY and HAMZA (1992) core (8-84). Carbonates compose 91 r;;) of this in­ concluded that this grainstone unit was at least terval (Figure 8A) and consist largely of shell, in part derived from eroded and reworked Ridge

Journal of Coastal Research, Vol. 9, No.1, 1993 ""'!i'

42 Warne and Stanley

III carbonates. Its well rounded, well sorted tex­ in the eastern portion of this study area (Figure ture suggests significant reworking. 7). Some more common colors include: light olive In contrast with the above, the limestone unit gray (5Y 5/2), dusky yellow (5Y 6/4), white (N9) in core S-85 is composed of very pale orange (lOYR and grayish orange (10YR 7/4). These stiff muds 8/2), medium-to very coarse-grained bioclastic are primarily composed of quartz; accessory com­ grainstones and algal boundstones. Large, well ponents include carbonate, aggregate and gyp­ preserved fossils are the principal component; sum. Irregularly shaped calcareous nodules are coated grains, ooids and unidentifiable fossil frag­ ubiquitous. Iron staining is common. Fauna and ments are important accessory components. Fau­ flora are generally absent in the sand size fraction, na in this unit include algae and foraminifera, although there is one fossil-rich horizon in core with lesser amounts of gastropods, echinoids and 8-81. Cross-bedding is well developed in some sec­ ostracods. This unit is commonly laminated, cross­ tions (Figure 9A), whereas mud cracks are well bedded and contains many diastems. The stratum developed in others. These muds are semi-con­ is 4 m thick in core S-85. Radiocarbon analysis solidated and thus are termed stiff muds. This suggests that this unit is >40,000 years old. This facies ranges in thickness from 0.5 to 8.8 m. One limestone has a composition intermediate be­ to three separate stiff mud intervals may occur in tween those of Ridges II and III; however, the the cores (Figure 7). Radiocarbon data indicate

high proportion of calcareous algae and presence that these stiff muds range in age from r- 16,500 of characteristic amphistegin foraminifera indi­ to >38,000 years BP. cate a closer affinity with Ridge III (STANLEY and Previous investigations in the north-central Nile HAMZA, 1992). The cross-bedded, coarse intervals delta (ARBOUILLE and STANLEY, 1991; STANLEY et indicate deposition under high energy, subaque­ al., 1992) recognized two distinct stiff mud types: ous conditions. The high proportion of large, well overbank and interdistributary lagoon facies. preserved fossils indicates short transport dis­ Compared to these two facies, the playa stiff muds tances and relatively minor sediment reworking. are more green, yellow and white (as opposed to brown), generally have a higher carbonate con­ Flood Plain Muds tent, are more oxidized, and contain almost no Greenish gray (5GY 6/1) to dark yellowish brown plant matter. Cross-bedded sandy muds up to 20 (lOYR 4/2) sandy muds form the upper portion em thick (Figure 9A) indicate subaqueous depo­ of the late Pleistocene sequence in only one core sition, whereas well-developed caliche horizons (S-73) in the eastern portion of the study area. and mudcracks indicate subaerial exposure. A Sands occur as dispersed, matrix-supported grains, general absence of vegetation is recorded by lack or as discrete beds (to 14 em thick) and lenses. of both root traces and plant material. The stiff Irregularly shaped calcareous nodules (1 mm to muds of the study area are interpreted to have 3 em) are ubiquitous. Fauna and flora are sparse been deposited in ephemeral lakes and playas near to absent. In some sections, interbedded sands the edge of the Nile delta flood plain under gen­ and silts are current-ripple laminated. These sandy erally arid conditions (cf. GUSTAVSON, 1991). muds are semi-consolidated and thus are termed stiff muds. This facies is ""' 1.5 m thick in core Late Pleistocene to Early Holocene Transgressive S-73. Radiocarbon dates from this facies indicate Sands an age> 12,700 years BP. The sandy stiff muds Olive gray (5Y 3/2) to yellowish brown (10YR in core 8-73 are interpreted to be channel over­ 4/2), fine- to coarse-grained, rather poorly sorted bank and crevasse-splay deposits which accu­ sands occur in the lower portions of cores S-72, mulated in shallow ephemeral lakes and/or playas S-75 and S-76 in the eastern study area (Figure in close proximity to distributary channels (cf. 7). These sands are primarily composed of un­ BUTZER, 1976; ABU-ZEID and STANLEY, 1990; AB­ stained quartz; common accessory components DEL WAHAB and STANLEY, 1991), under generally include heavy minerals, shell fragments and ver­ arid conditions (ct. REINECK and SINGH, 1980; dine/glauconite. Undifferentiated carbonate and COLLINSON, 1986; CHEN and STANLEY, in press). shell fragments comprise as much as 35 ~~) of the sand fraction. Fauna, although generally sparse, Flood Plain Margin and Playa Muds includes gastropods, pelecypods, ostracods and Variegated, streaked and mottled stiffmuds and foraminifera. This facies ranges to 10m thick in sandy muds occur in several cores (S-77 to S-83) study area cores. The sands per se have not been

Journal of Coastal Research, Vol. 9, No.1, 199a Evolution of the NW Nile Delta 43 dated, but radiocarbon dates from Holocene muds valves, gastropods and foraminifera as the most immediately above these sands indicate they were common taxa. Shells in brackish water bay facies deposited before 7,500 years BP. tend to be smaller (0.5-2.0 mm) than those in Several Nile delta studies to the east (e.g., lagoons, and are usually more dispersed (Figure COUTELLIER and STANLEY, 1987; ARBOlJlLLE and 9B). Horizontal and uneven laminae are com­ STANLEY, 1991; STANLEY et al., 1992; CHEN et al., monly observed in muds; stratification, in some 1992) have interpreted this facies to he marine cases, is highlighted by concentrations of fossils transgressive sands which were deposited during (Figure 9B). Brackish water bay mud sections the last rapid rise in sea level (Flandrian trans­ range in thickness from 1.2 to 7.0 m, Radiocarbon gression). This facies is the product of reworking dates indicate that this facies was deposited pri­ of late Pleistocene alluvial and shallow marine marily between 7,000 and 5,000 years BP. deposits which resulted in concentration of sands. Carbonate pebbles commonly occur in brackish Carbonate content in this facies increases west­ water bay muds and are composed of irregularly ward (STANLEY and HAMZA, 1992): increased pro­ shaped calcareous siltstone and grainstone. Thin­ portions of marine carbonates relative to terres­ section analysis shows that these pebbles were trial siliciclastics is a function of the decreased derived from the adjacent Abu Sir Ridge II (cf. influence of the River Nile system at and west of EL FAYOUMY et al., 1975; STANLEY and HAMZA, the Alexandria region. 1992; CHEN et al., 1992). The pebbles were prob­ ably washed from the ridge and incorporated in Holocene Sediment Types bay deposits during storms. Nile delta sediments of Holocene age began to Molluscan assemblages from bay facies indicate accumulate -7,500 years BP in the eastern part brackish water conditions with significant marine of the study area as the rate of sea-level rise began influence. These faunas also suggest accumulation at water depths ranging from 5 to 7 m (M. P. to decrease (cf. MORNER, 1976; cf. LIGHTY et al., BERNASCONI, written communications, 1991, 1982; cf. FAIRBANKS, 1989; STANLEY, 1990; see eu­ static sea-level curve in Figure 7). Unlike the 1992). Combined petrologic and molluscan com­ northeastern Nile delta (COlJTELLIER and munity analyses indicate that these muds accu­ STANLEY, 1987; STANLEY et al., 1992) there are no mulated in generally brackish water, but in deep­ open marine (prodelta, delta-front) facies of Ho­ er, more marine-influenced conditions than those locene age in the present study area. In addition, of lagoons. unlike Holocene sequences to the east, which are Nearshore Marine (Closed-basin) Muds composed of several distinct facies (CHEN et al., Gray, sandy and silty muds were described in 1992), Holocene sequences in the central and numerous engineering cores (E-2 and E-3 are ex­ western sectors of the study area are composed amples) from the harbor area of Alexandria (Fig­ of only one facies. ures 1,7). The muds are characteristically organ­ An unconformity separates the Holocene from ic-rich, shelly and have a hydrogen sulfide odor. underlying alluvial or coastal sands (BERNASCONI Root traces are common. This mud interval rang­ et al., 1991; STANLEY et al., 1992). In the present es from 6 to 11 In thick. The age of the base of study area, lag deposits comprising shells, coarse the muds above carbonate sands has not been sands, and rounded carbonate pebbles occur at or just above this hiatus in many cores. Radiocarbon radiocarbon-dated, but most probably is of mid­ Holocene age. Organic-rich muds are currently dates indicate that this lacuna is larger in the being deposited in the semiclosed Eastern and southern and western part of the study area. Western harbors of Alexandria, from depths of several meters close to shore to a maximum of 8 Brackish Water Bay Muds m. Recent and sub-recent sediment is anthropo­ Olive gray (5Y 3/2), grayish black (N2), to genic (municipal and industrial waste) and is greenish black (5 GY 2/1) soft, homogenous muds highly polluted (EL-SAYED et al., 1988; DOWIDAR occur near the base of the Holocene sequence in and ABOUL KASSIM, 1986). five cores (S-72 to S-76) to the south of Abu Qir (Figures 1,7). Common sand-size components in­ Holocene Lagoon Facies clude light and heavy minerals, micas and shells. Previous studies described older Holocene and The muds are generally fossiliferous, with hi- modern lagoon mud facies in the northern Nile

Journal of Coastal Research, Vol. 9, No.1, 1993 44 Warne and Stanley

delta to the east (ARHOUILLE and STANLEY, 1991; nifera, and higher proportions of gypsum and car­ LOIZEAU and STANLEY, in press). Based on de­ bonates (Figures 8, 10). Fauna is dominated by tailed petrological and molluscan community pelecypods, particularly Cardium; other fauna in­ analyses, three mud subfacies are distinguished clude gastropods, ostracods, and foraminifera. in the northwest Nile delta region: marine-influ­ Bedding is generally obscured by bioturbation and enced lagoon, fluvially-influenced lagoon, and la­ shell; however, in places, shells form distinct lay­ goon margin. ers (Figure 9D). The thickness of this lagoon Marine-influenced Lagoon Muds. Olive gray (5Y subfacies ranges from 2 to 9 m. Radiocarbon data 3/2) to dark gray (N3) plant-rich muds and silts and historical records indicate that these ftuvi­ occur in the eastern part of the study area (S-72 ally-influenced deposits accumulated from """6,100 to S-78). The sand fraction is primarily composed to 700 years BP. Molluscan community analysis of quartz and shell; accessory components include suggests that the mud and shell sequence was heavy minerals, mica and plant debris. Some in­ deposited in brackish water with significant fresh­ tervals consist almost entirely of molluscs (Figure water influence (M.P. BERNASCONI, written com­ 9C). Biogenic components include characteristic munication, 1992). This subfacies is interpreted ostracods (PUGLIESE and STANLEY, 1991), benthic to have been deposited in a basin which was not foraminifera (EL-WAKEEL et al., 1970; KULYK, directly connected to the sea, and was fed directly 1987), molluscs (BERNASCONI et al., 1991), sponge by one or more perennial River Nile channels. spicules and diatoms; plant matter is common to Gypsum in this facies (Figure 10F) is inter­ abundant. Bedding may be undisturbed or com­ preted to have formed postdepositionally, prob­ pletely obscured by bioturbation. Where undis­ ably between the twelfth and nineteenth centu­ turbed, bedding features include: horizontal and ries. During this period, all Nile delta channels wavy lamination, small-scale ripple cross lami­ which had supplied fresh water to Lake Mareotis nation, and lenticular to flaser bedding (CHEN et had silted up so that the lake level fell, and this al., 1992, their Figure 5B; STANLEY et al., 1992, region became a salt lake and sabkha. Under these their Figure 3). The thickness of this lagoon subfa­ evaporitic conditions, saline groundwater precip­ cies ranges from 1 to 9 m. Radiocarbon data in­ itated gypsum in the buried freshwater lake de­ dicate that lagoon deposits accumulated from posits. It is of note that gypsum is currently

r-..., 5,000 years BP to the present. Molluscan pa­ forming beneath the surface of the nearby EI De­ leocommunity analysis on two cores (M. P. kheila-Abu Sir and Mallahet Maryut depressions BERNASCONI, written communications, 1991, 1992) (WEST et al., 1979; ALI and WEST, 1983). indicates that these muds were deposited in a Lagoon Margin Muds. Light olive gray (5Y 6/1) marine-influenced lagoon which was directly con­ to yellowish gray (5Y 7/2) muds occur primarily nected to the sea, and supplied with fresh water in core 8-84, in the western extension of Maryut by Nile distributaries. These deposits are directly lake (Figures 1, 7). The sand fraction in these comparable with those accumulating in the mod­ muds is primarily composed of weathered lime­ ern Idku lagoon (LOIZEAU and STANLEY, in press), stone (Ridge II) residuum, carbonate aggregates and with adjacent Holocene lagoon mud facies and quartz. Significant accessory components in­ described by COUTELLIER and STANLEY (1987), clude plant material, gypsum and shell (Figure ARBOUILLE and STANLEY (1991), STANLEY et al. 10). Limestone pebbles (to 10 ern) occur locally. (1992), and CHEN et al. (1992). Fossils are generally sparse; however, there is one Fluvially-influenced Lagoon Muds. Olive gray fossil-rich horizon in which foraminifera are es­ (5Y 3/2) to dark gray (N3) to greenish gray (5GY pecially abundant. The unit has been thoroughly 6/1) muds and silts occur in the central and west­ bioturbated by roots. Discrete quartz sand layers ern part of the study area (8-77 to S-84). The are generally absent. Gypsum nodules are com­ sand fraction in these muds is primarily composed monly noted in x-radiographs (Figure 9E). This of quartz and shell; accessory components include facies is 2 m thick in S-84. No radiocarbon dates unidentified carbonate particles and gypsum. are available for this unit. In contrast to marine­ Many intervals consist almost entirely of molluscs influenced and freshwater-influenced lagoon sedi­ (cf. Figure 9C). In contrast to the marine-influ­ ments, this subfacies by being lighter colored (more enced lagoon subfacies, the freshwater influenced oxidized), contains higher proportions of gypsum, lagoon subfacies has lower proportions of heavy roots and root traces, and lower proportions of minerals, mica, verdine/glauconite and forami- shell. The gypsiferous mud, abundant root traces

-Iournal of Coastal Research, Vol. 9, No.1, 199:1 Evolution of the NW Nile Delta 45

Holocene Sands: Average % Gypsum

Figure 10. Isopleth map showing frequency distributions (averaged percent) of selected sand-size components for the Holocene section. Distributions are discussed in text.

and its proximity to Ridge III indicate that these to yellowish gray (5Y 7/2), very fine- to fine-grained, deposits accumulated along a lagoon margin. moderately to well sorted sands occur as beds and lenses within lagoon mud facies in cores S-72, Holocene Sand Facies 8-73,8-75,8-76 and 8-78. Quartz is the primary Four sand facies of Holocene age are recognized constituent and mica is common to abundant; in the study area: nearshore marine-beach, la­ other accessory components include shell frag­ goon, fluvial channel to crevasse-splay, sabkha and ments, verdine/glauconite, pyrite and gypsum. alluvial fan. Each of these sand facies is described Sand layers within muddy lagoon facies range from below. a few millimeters to 9 em thick. Based primarily Nearshore Marine to Beach Sands. Yellowish gray upon petrology, ARBOUILLE and STANLEY (1991) (5Y 7/2 to 5Y 8/1) mostly fine- to medium-grained distinguished two lagoon sand subfacies: fluvially­ sands occur in the upper portions of one core (8­ influenced and storm wash-over. Of the two, storm 73). These sands are characterized by relatively wash-over sands contain relatively higher pro­ lowproportions of lightly iron-stained quartz, and portions of fossils and verdine/glauconite, where­ high proportions of heavy minerals. Verdine/glau­ as ftuvially-influenced lagoon sands contain rel­ conite is a common accessory component. Shells atively higher proportions of plant debris. Lagoon are sparse and occur mostly as fragments. This sands of the present study are primarily fluvially­ facies is 1.5 m thick in core S-73. Radiocarbon influenced. dates indicate that these sands were deposited Fluvial Channel to Crevasse-splay Sands. Olive within the past 3,400 years. Low proportions of gray (5Y 3/2) to grayish olive (lOY 4/2), generally stained quartz and high proportions of heavy min­ fine-grained, moderately to poorly sorted sands erals are characteristic of sands extensively re­ occur in cores 8-73 and 8-75 (CHEN et al., 1992). worked in a swash zone where denser grains are Quartz is the main constituent; accessory com­ concentrated (STANLEY et al., 1992). Verdine/ ponents include heavy minerals, mica and gyp­ glauconite indicates that these sands accumulated sum. The few fossils present, such as in core 8-73, in or near a shallow marine environment (cf. PIM­ are broken and abraded. The thickness of this MEL and STANLEY, 1989). facies in the study area ranges from 1 to 4 m. Lagoon Sands. Pale yellowish brown (lOYR 6/2) Radiocarbon data indicate that these sands were

Journal of Coastal Research, Vol. 9, No.1, 1993 1 46 Warne and Stanley deposited as early as 5,900 years BP (S-75) and Sea-level Factor as late as 2,900 years BP (S-73). The high pro­ portion of iron-stained quartz and absence of Late Quaternary lithofacies in the Nile delta nonreworked fossils indicate that these sands were study area were deposited during the most recent deposited in river channel and adjacent crevasse­ eustatic sea-level cycle: from the last Pleistocene splay environments ic]. STANLEY and CHEN,1991; highstand (---35,000 to 30,000 years BP), to the CHEN et al., 1992). These Holocene sands are last Pleistocene lowstand ( --- 20,000 to 18,000 years readily distinguished from the late Pleistocene BP), to the present highstand (cf. eustatic curves alluvial sands: the Holocene fluvial sands are of LIGHTY et al., 1982; FAIRBANKS, 1989; see also primarily composed of fine-grained, lightly iron­ PIRAZZOLI, 1992). Tide-gauge data for the past 50 stained quartz, whereas the late Pleistocene al­ years from the Alexandria region indicate that luvial sands are primarily composed of coarse­ relative sea level has continued to rise and could grained, well rounded, highly iron-stained quartz. be as much as 1.8 to 2.5 m above its present level Sabkha to Alluvial Fan Silty Sands. Very pale by 2100 (EL-FISHAWI and FANOS, 1989; FRIHY, orange (lOYR 8/2) to grayish orange (10YR 7/4), 1992). very fine-grained sands and silts are best devel­ To better understand the influence of sea level oped in core S-85. The sands and silts are pri­ oscillations on coastal development, impacts of marily composed of carbonate with gypsum; ac­ late Pleistocene to Holocene sea-level changes on cessory components include quartz and shell subsurface lithofacies distributions are discussed. fragments. Carbonates are most commonly com­ (1) Late Pleistocene carbonate ridges record posed of weathered limestone fragments and car­ sea-level stands that are generally higher than at bonate aggregates. Fauna is very sparse. This present (SHUKRI et al., 1956; BUTZER, 1960). Some subfacies is 6 m thick in S-85. Because of re­ wor kers have proposed that these ridges origi­ working, these sands cannot be accurately dated nated as submarine coastal bars which record sea by the radiocarbon method. The high proportion level at the time of their formation (ZEUNER, 1952; of weathered limestone and the proximity of core SHUKRI et al., 1956); other workers, however, re­ S-85 to Ridge III indicate these are alluvial fan alized that significant portions of these ridges are deposits: in addition, the high proportion of gyp­ of coastal dune origin and thus do not reflect sea sum and silt suggest these are sabkha sediments. level at the time of deposition (BUTZER, 1960). It is of note that core 8-85 was recovered in the Recent work has shown that several minor sea­ Mallahet Maryut depression; ALIand WEST (1983) level cycles are recorded within a single ridge described the upper 1 m of sediments in this de­ (HASSOUBA, 1980; HASSAN et al., 1986). pression as sabkha deposits. (2) Younger late Pleistocene siliciclastic allu­ vial to shallow marine sand, local drowned valley sand, flood plain stiff mud, deltaic siliciclastic to FACIES AS RELATED TO SEA LEVEL, coastal carbonate sand, and carbonate coastal sand NEOTECTONISM AND CLIMATE accumulated from earlier than ---30,000 to 11,000 Petrologic analyses described above highlight years BP. Thus, they were deposited during the the diversity of late Quaternary coastal and ter­ last Pleistocene sea-level highstand, last major restrial sediment types in the Alexandria region. eustatic lowering, and early phases of the subse­ A summary of the laterally variable lithofacies quent very rapid sea-level rise. The coastline at sequences is represented by generalized sedimen­ that time was generally northward (seaward) of tary sequences from four sectors of the study area its present position, having migrated as much as (Figure 7). In the following sections, an attempt 50 km to the north of the present coast, just land­ is made to place these late Quaternary lithofacies ward of the present-dayshelfbreak (SUMMERHAYES sequences in a comprehensive stratigraphic and et al., 1978; MALDONADO and STANLEY, 1979; AB­ paleogeographic context. To do so requires that DEL WAHAB and STANLEY, 1991). each facies be related to principal factors which (3) Marine transgressive sands accumulated in determine sediment distribution. Here, lithofa­ the eastern part of the study area from 11,000 to cies distributions in time and space are considered 8,000 years BP as sea level continued to rise. This in terms of sea level, tectonism and climate. A late Pleistocene to early Holocene rapid rise caused fourth major factor, sediment transport processes, the coastline to retrograde southward of the pres­ is considered in later sections. ent-day Nile delta shoreline to the east of Abu

.Iournal of Coastal Research, Vol. 9, No. ],1993 i Evolution of the NW Nile Delta 47

Qir. An unconformity developed at the base of vations on submerged Greek and Roman ruins in transgressive sands as the shoreline migrated the Alexandria and Abu Qir regions lead JONDET southward (landward) and marine currents and (1916), TOUSSOUN (1934), MORCOS (1985) and waves reworked late Pleistocene sediments. EL-SAYED (1988b) to conclude that ruins as old (4) An unconformity also occurs at the base of as 2,500 years along the coast had submerged 2 the Holocene sequence throughout the study area. to 5.5 m. Several observations suggest that neo­ Radiocarbon dates indicate that this lacuna is tectonics and seismicity may have been a factor. variable in duration and that Holocene sedimen­ For example, four major earthquakes which shook tation commenced ,....., 7,500 to 5,000 years BP. In Alexandria in the fourth century A.D. (DE COSSON, particular, this surface of erosion and (or) non­ 1935) are nearly coincident with a major tectonic deposition continued well into the mid-Holocene event in the eastern Mediterranean during the in the southern and western portion of the study fifth century AD; this event likely resulted in ver­ area (Figure 7). tical displacements at numerous localities around (5) By ---7,500 years BP the rate of sea-level the Mediterranean basin (PIRAZZOLI, 1987). There rise decelerated such that the rate of sediment is, in fact, considerable evidence of fault displace­ input began to predominate over the rate of sea­ ment in the study area. BUTZER (1960) pointed level rise; consequently, aggradation and progra­ out that several of the late Pleistocene carbonate dation of Nile delta sediments began to accu­ ridges terminate at the same longitude; he attrib­ mulate on the unconformity. utes this to possible displacement along north­ (6) Brackish water bay muds were deposited south oriented faults (Figure 2, inset). From geo­ in the eastern sector of the study area from -.,7,500 physical surveys, SHATA (1955) and EL RAMLY to 5,000 years BP, while the southern and western (1968, 1971) described subsurface folds in the re­ sectors of the study area remained emergent. gion. EL RAMLY (1971) proposed that the carbon­ (7) By ---5,000 years BP, as sea level continued ate ridges were delimited by successive earth to rise, the central and western sectors of the study movements. From satellite images, EL SHAZLY et area were inundated and fluvially- to marine-in­ al. (1975) described an important system extend­ fluenced lagoon conditions were established. ing northwestward from Wadi Natrun toward the (8) From --5,000-1,000 years BP, as sea level Borg el Arab region. HASSOUBA (1980) attributed has continued to slowly rise, marine-influenced the eastward disappearance of late Pleistocene lagoon muds and fluvial sands accumulated in the carbonate ridges to increased isostatic loading, eastern sector and fluvially-influenced lagoon, la­ and perhaps faulting, to the east under the weight goon margin and sabkha sediments accumulated of thick River Nile sediments. Based primarily on in the western sector of the study area. During satellite imagery, NEEV et al. (1982, 1985, 1987) this period, sea level rose from about -5 m to -1 suggested that the Alexandria region lies within m (cf. LIGHTY et al., 1982). a major northeast-southwest oriented fracture zone (a left-lateral megashear) that extends from the Israel-Lebanon coast southwestward through Tectonic Factor central Africa. In this scheme, the Alexandria re­ Lithofacies distributions can he affected by dis­ gion is located along the northeast-southwest ori­ placement of land surface (subsidence or emer­ ented Qattara-Eratosthenes shear (NEEv et al., gence) relative to sea level in a similar way as they 1982). These authors recognized three sets ofpho­ can by a change in sea level relative to land sur­ tolineaments in the Alexandria region: NE-SW, face. It is thus imperative in paleogeographic re­ WNW-ESE and E-W. It has been proposed that constructions to distinguish the effects of these late Pleistocene carbonate (kurkar) ridges in the two factors: eustacy and tectonism. The late Qua­ study area are tectonically elevated and formed ternary sea-level history, as discussed in the pre­ along pre-existing lineaments (NEEv et al., 1987). vious section, is reasonably established. Here, ev­ An isopachous map of the total Holocene sec­ idence for tectonism in the Alexandria region and tion, based on analysis of Smithsonian and en­ its possible effects on lithofacies distributions are gineering borings, is useful in differentiating the discussed. tectonic from sea-level factor. It is of note that Several studies have found archeological and field penetrometer measurements of Holocene geological evidence which indicate late Quater­ sediment strength in cores show little variability nary tectonic activity in the study area. Obser- both vertically and laterally. It hence appears that

Journal of Coastal Research, Vol. 9, No.1, 199:3 48 Warne and Stanley

sidence) by the radiocarbon age of that core sam­ ple. Using core S-77 as an example, the lowest radiocarbon-dated sample has an age of 6,170 years BP at a depth of 8.7 m. Eustatic sea-level curves indicate that, at 6,170 years BP, sea level was 7 m below its present stand, and thus the thickness of Holocene sediment, which can be attributed to vertical land motion, is 8.7 - 7 = 1.7 m. A lowering rate of 0.03 cm/yr (30 cm/IOO yrs) is calculated by dividing 1,700 em (1.7 m) by 6,170 years. Given a maximum one standard deviation error of 140 years (as reported by Beta Analytic), the subsi­ dence rates are accurate to within 5 C;~). Error in­ troduced by inaccuracies in the estimated sea lev­ B -10- Holocene thicknessoontours in meters el rise, however, is not known. Figure 11. Isopachous maps of the total Holocene thickness The above calculations assume that present (contours in meters). (A) map depicting long-termed averaged ground elevation of the boring site is at sea level, Holocene subsidence-emergence rates in em/yr. Areas with over­ and that the radiocarbon-dated layer was depos­ all emergence are denoted by negative numbers. (B) map show­ ing long-term averaged Holocene sediment accumulation rates ited at sea leveL However, surface elevations from in em/yr. which some of the borings in this region were taken are actually below sea level (Figure 4). Thus, long-term subsidence rates calculated for the study sediment compaction has not significantly mod­ area are minimal. Calculations that result in neg­ ified lithofacies thickness trends. ative values, at 3 of the 14 Smithsonian core sites Figure 11 shows that Holocene sediments thick­ in the western and southwestern sectors, indicate en markedly to the east, towards Abu Qir bay. The minor emergence during the Holocene. most notable exception to this overall thickness Calculated long-term vertical land displace­ trend is in the harbor area of Alexandria where ment rates indicate minor subsidence (to 0.07 em/ isolated pods of Holocene sediments attain thick­ yr) in the east (Figure lIA) and minor emergence nesses of more than 10 m. It should be kept in (to -0.5 cm/yr) in the west. Low subsidence val­ mind, however, that availability of Holocene ues are a marked contrast to regions just to the thickness data for the region is unevenly distrib­ east and northeast where subsidence rates as high uted. For example, no thickness data currently as 0.45 cm/yr are recorded in the Rosetta prom­ exist for El Dekheila-Abu Sir depression I, or for ontory region (CHEN et al., 1992). Emergence, at the nearshore, open marine shelf, north of the Abu least locally, would help explain the presence of Sir-Alexandria coast. one or more hiatuses within various Holocene sec­ Long-term land displacement (subsidence or tions. Radiocarbon dates from study area cores emergence) rates have been calculated for all cores demonstrate that the most significant hiatus oc­ in the study area (cf. method of STANLEY, 1988). curs at the base of the Holocene, and that this To obtain conservative values, calculations for each lacuna is greatest in the southwest. core involve: (1) determining the age and depth Ruins of the ancient Hellenistic city of Canopus of the lowest-oldest radiocarbon-dated Holocene in Abu Qir bay (Figure 3; TOUSSOUN, 1934) now sample for each core; (2) estimating the sea-level lie as much as 5 m below sea level. Tousson (1934) position, relative to the present stand, at the time assumed that these Hellenistic (--- 500 BC and indicated by the dated sample, using a eustatic younger) ruins were originally as much as 3 m curve tc]. LIGHTY et al., 1982); (3) subtracting the above sea level, which would imply that they have total Holocene thickness for that core from the been submerged as much as 8 m during the past depth of sea level projected from eustatic curves 2,500 years. According to many eustatic curves at that time: this subtraction is done to account (cf. LIGHTY et al., 1982; FAIRBANKS, 1989), sea for accommodation space (WILGUS et al., 1988) level has risen ---2.5ill during the past 2,500 years. made available by subsequent sea level rise; and From this, it has been suggested that the ruins of (4) division of the remaining sediment thickness Canopus may have tectonically subsided at a rate (or accommodation space made available by sub- of 0.22 em/year (CHEN et al., 1992), which is sig-

l Journal of Coastal Research, Vol. 9, No. r, 199:~ 1 Evolution of the NW Nile Delta 49 nificantly higher than rates to the south and west late Pleistocene age are characteristic of desert (Figure 11A). Subsidence at Canopus approaches coast deposits (cf. EL SHAMI et al., 1971; GLENNIE, rates recorded in the Rosetta promontory to the 1987). In the eastern part of the study area, me­ east. From observations on the depths of Helle­ dium to coarse, poorly sorted, iron-stained sands nistic and Roman ruins in the Alexandria harbor of late Pleistocene age (particularly those which region (JONDET, 1916; Moncos, 1985; EL-SAYED, accumulated between --20,000 and 12,500 years 1988b), it may be concluded that the Alexandria BP) were deposited under arid conditions by a coast (Figure 3) has been submerged at rates of seasonally dry, braided river system (cf. ADAMSON 1 to 2 m/1,000 yr. EI Sayed (1988b) concluded et al., 1980; STANLEY et al., 1992). Flood-plain and that the tectonic factor is an important compo­ playa stiff muds of late Pleistocene age accumu­ nent of this submergence. From our present study, lated locally in ephemeral interchannel depres­ we interpret the tide-gauge data for Alexandria, sions; calcareous nodules and gypsum in these cited earlier (increased water level of 0.18 to 0.25 flood-plain muds suggest repeated seasonal wet­ em/year), as recording both eustatic sea level rise ting and drying in an arid to semiarid climate (cf. (to 0.1 em/year) and tectonic land subsidence (to GUSTAVSON, 1991; CHEN and STANLEY, in press). -0.15 em/year). Climate has also been a major factor in deter­ From the above considerations, it is apparent mining sediment type and distribution during that the petrologically variable Holocene facies in Holocene times (--7,500 years BP to the present). the study area accumulated in a sector of the delta Reduced proportions of coarse, iron-stainedsands which has undergone modest vertical land dis­ in Holocene river channel deposits indicate more placement when compared to areas to the east humid conditions. Moreover, the transition from (ARBOUILLE and STANLEY, 1987; CHEN et al., 1992). thick late Pleistocene alluvial sands to discrete The modest rates would explain the absence of Holocene fluviallithosomes in mud (Figure 7) re­ open marine facies (prodelta and delta-front) in cord a change from a seasonally dry, braided river the Alexandria region (Figure 7). in the late Pleistocene to a perennial, meandering river system in the Holocene. Fluvially-influenced Climatic Factor lagoon deposits in the western part of the study Climatic change can affect sea-level fluctua­ area also record the presence of a perennial river tions, coastal processes, river channel migrations, system. In contrast, gypsiferous sabkha deposits and therefore, sediment distribution. Thus, in or­ in the western part of the study area (WEST et der to more fully define late Quaternary paleo­ al., 1979; ALI and WEST, 1983) indicate that, over­ geography in the Alexandria region, it is impor­ all, the Holocene climate has remained arid. tant to differentiate the role of climate from the The above climatic observations concur with other controlling factors. The late Quaternary cli­ those made in the delta regions to the east matic history of the eastern Sahara and Nile val­ (ARBOUILLE and STANLEY, 1991; STANLEY et al., ley region (ADAMSON et al., 1980; PAULISSEN and 1992; CHEN et al., 1992). In our view, climate has VERMEERSCH, 1989; PETIT-MAIRE, 1989) during significantly influenced sediment composition and the past 35,000 years can be summarized as fol­ facies distribution in the Nile delta study area, lows: from --35,000 to 25,000 years BP climate but to a lesser extent than either eustatic sea-level was arid; from --25,000 to 20,000 years BP con­ or tectonic oscillations. For example, the overall ditions were somewhat more humid; from --20,000 transition from late Pleistocene alluvial to Ho­ to 12,500 years BP climate was generally cool and locene coastal deposition records the change from dry; from --12,500 to 5,000 years BP climate was a major sea-level lowstand to a highstand. More­ more humid resulting in high floods; and from over, variable Holocene sediment thicknesses and -5,000 years to the present, climate has been arid. lithofacies sequences record variable subsidence Archeologic evidence indicates that the climate histories across the study area (Figure 7). in the Alexandria region has become significantly drier during the past 2,000 years (DE COSSON, RATES OF SEDIMENT ACCUMULATION 1935). Holocene sediment accumulation rates (Figure Several late Pleistocene lithofacies, and their lIB) are calculated to more accurately interpret distribution, can be related to syndepositional cli­ facies distribution in time and space and, more matic conditions. In the western part of the study specifically, to better differentiate the effects of area, medium to coarse carbonate-rich sands of sea level and tectonism on lithofacies distribution.

Journal of Coastal Research, Vol. 9, No.1, 1993 50 Warne and Stanley

rates from r- 5,000 to 8,000 years BP. These trends Age (In years B.P.) are highlighted by a calculated exponential curve. 8000 6000 4000 2000 0 0 ~ The dispersal of data points may, in part, reflect CD CD irregular, pre-Holocene topography on which sed­ E 2 g iments were deposited. en The calculated accumulation curve is nearly co­ 4 a.CD E incident with (--0.5 m below) the general eustatic 6 m sea-level curve of LIGHTY et al. (1982). This par­ CD allel trend of the accumulation and sea-level curves 8 8 "C indicates that major changes in Holocene accu­ coCD 10 "C mulation rates are primarily controlled by changes '0 .J::. in rates of sea-level rise. This would support our 12 Q. CD contention that Holocene eustatic sea-level fluc­ c I. iii I ii, I, i , I 14 tuations are the principal influence on sedimen­ tation in the region. Figure 12. Graph showing core depth versus radiometric age fur 17 samples from 11 cores. The exponential curve was cal­ An average regional sediment accumulation rate culated from these data. Superimposed on the calculated curve of 0.10 cm/yr for the past 5,000 years is estimated is a generalized eustatic sea-level curve (from Lighty et al., from the overall slope of the calculated curve in 1982); depth is in meters below sea level. The near-coincident Figure 12. This calculated rate is the same as the calculated and eustatic curves implies (1) Holocene sedimen­ tation rates are largely controlled by rate of sea-level rise, and rate of sea-level rise. These comparable rates (2) tectonic subsidence was minor during the Holocene. See text demonstrate that, overall, subsidence in the study for discussion. Error in radiocarbon dates, as reported by Beta area during the Holocene was modest to negligi­ Analytic Inc., represent one standard deviation and range from ble. ± 60 to ± 140 years. REGIONAL LITHOFACIES CORRELATION AND GEOMETRY Accumulation rates have been calculated in two Integration of all pertinent petrologic, faunal ways, as described below. and radiometric data for each study area core, and Long-term averaged rates of sediment accu­ subsequent core-to-core correlations define late mulation were calculated for each of the fourteen Quaternary lithofacies distributions in time and Smithsonian core sections. Calculations first in­ space. Correlations and lithofacies analysis take volved determination of core depth and age of the into account the relative impact of sea level, tec­ oldest radiocarbon-dated Holocene sample in each tonism and climate on sedimentation. In addition, core. Averaged accumulation rates are calculated the effects of sediment transport processes on by dividing the depth of each sample by its age lithofacies distributions need also to be consid­ in all cores. Estimated values take into account ered here. Salient features of lithofacies distri­ possible errors associated with the radiocarbon butions are summarized in Figures 13 and 14, and date. are described below, from oldest to youngest. Holocene sediment accumulation rates across (1) Petrographic data show that Ridges I, II the study area (Figure lIB) generally decrease and III are lithologically distinct (STANLEY and from northeast (0.20 cm/yr, or 200 cm/l,OOO yrs) HAMZA, 1992), and paleontologic data indicate to southwest (0.02 cm/yr, or 20 cm/l,OOO yrs): these ridges were deposited during separate time these values are significantly lower than rates in periods (SHLJKHI et al., 1956). Each ridge is in­ the Nile delta to the east (COUTELLIER and terpreted to be composed of nearshore marine to STANLEY, 1987; ARBOUILLE and STANLEY, 1991; coastal dune sediments which accumulated dur­ STANLEY et al., 1992; CHEN et al., 1992). ing an overall sea -level highstand. These ridges Changes in sediment accumulation rates over contain interbedded paleosols, caliche horizons time were determined, using 17 radiocarbon-dated and marine deposits which record minor sea-level samples of Holocene age from 11 cores. A graph fluctuations during ridge development (cf. HAS­ showing depths of dated samples versus age of SAN et al., 1986; STANLEY and HAMZA, 1992). Ridge these samples (Figure 12) reveals a marked de­ II and Ridge III carbonates are interpreted to be

crease in accumulation rates from >- 7,500 to 5,000 separated by an unconformity (see also SHUKRI years BP, and then a more gradual decrease in et al., 1956, their Figure 2).

Journal of Coastal Research, Vol. 9, No. 1, 199:~ Evolution of the NW Nile Delta 51

Late Pleistocene Holocene bEl Alluvial to shallow marine siliciclastic sands Intra-late Pleistocene Artificial fill Marine- influenced unconformities lagoon muds ~ Drowned channel siliciclastic sands Sabkha sands Nearshore marine and silts G{] Deltaic siliciclastic to coastal carbonate sands Late Pleistocene to Holocene -beach sands Fluvial crevasse ~ Well cemented grainstones splay sands Brackish water U Transgressive sands bay muds ~ Ridge II carbonate sands (poorly cemented) Lagoon margin Nearshore marine _____ Late Pleistocene to muds ~ Ridge III carbonate sands (poorly cemented) Holocene unconformity (closed-basin) muds Fluvially­ rn Undifferentiated carbonate sands (poorly cemented) influenced Intra-Holocene lagoon muds unconformities mFlood plain stiff muds [;] Flood plain margin and playa stiff muds

o 10 20 ---km Figure 13. Stratigraphic fence diagram summarizing the late Pleistocene and Holocene lithofacies distributions in time and space.

(2) Well cemented grainstones occur locally tocene age (ATTIA, 1954; SAID, 1981; COUTELLIER within poorly cemented Ridge II and Ridge III and STANLEY, 1987; ARBOUILLE and STANLEY, 1991; carbonate sands (Figures 1~3, 14A-A'). Initial pet­ STANLEY et al., 1992; CHEN et al., 1992). rologic analysis indicates at least two generations (5) A thick section of drowned channel sands of cement (STANLEY and HAMZA, 1992). ( > 13,000 years BP) occurs in the lower portion (3) Deltaic siliciclastic to coastal carbonate of core 8-73, to the east of Abu Sir ridge (Figures sands of late Pleistocene age (> 38,000-15,000 13, 14A-A'). These very coarse sands record the years BP) occur in the central portion of the study location of a major Pleistocene (pre-Canopic) Nile area (Figures 13, 14A-A'). These sands mark the channel. Absence of incised river channels through transition zone between the Nile delta to the east Abu Sir Ridge II (>35,000 years BP) to the west and the desert coast to the west. Unconformities of 8-73 (Figures 2, 4) indicates that this pre-Ca­ separate the deltaic siliciclastic to coastal carbon­ nopic channel was the westernmost River Nile ate sands from the significantly older Ridge II and distributary during the latest Pleistocene. Ridge III carbonates. (6) Late Pleistocene stiffmuds (>35,000-11,000 (4) Thick sections of late Pleistocene silici­ years BP) occur in the upper portions of many clastic alluvial sands (>35,000-12,700 years BP) late Pleistocene sand sequences (Figures 13, 14A­ occur in the eastern part of the study area. These A'). These muds are interpreted to be overbank medium to coarse, quartzose sands are interpret­ and playa deposits which accumulated in local­ ed to be braided river deposits, with some inter­ ized depressions during seasonal floods. It is of calated nearshore marine and beach sands. These note that these stiff muds are most common in sands are the westernmost portion of the thick the cen tral portion of the study area (Maryut lake and widespread Nile sand lithosome of late Pleis- region); this indicates that the lake sector was a

Journal of Coastal Research. Vol. 9, No.1, 1993 52 Warne and Stanley

A A' 5-85 5-84 5-83 5-80 S-77 S-76 5-75 5-73

Late Pleistocene B B' El Alluvial to shallow marine siliciclastic sands E-3 E-4 5-76 5-74 5-72 ~ Drowned channel siliciclastic sands o D Deltaic siliciclastic to coastal carbonate sands ~ Well cemented grainstoncs r;n ~1II10 If§ Ridge ITcarbonate sands (poorly cemented) E ~ Undifferentiated carbonate sands (poorly cemented) mFlood plain muds 20 ~ Flood plain margin and playa stiff muds

Intra-late Pleistocene unconformity Holocene (!rnI Artificial fill Late Pleistocene to Holocene m Sabkha sands and silts [J Transgressive sands ~ Fluvial crevasse splay sands ~ Late Pleistocene to Holocene unconformity Lagoon margin muds ~ Fluvially-influcnced lagoon muds c C' ~ Marine-influenced lagoon muds E-3 E-4 ~ Nearshore marine-beach sands ~ Brackish water bay muds ~ Nearshore marine (closed-basin) muds - Intra-Holocene unconformity

km

Figure 14. Stratigraphic cross-sections showing late Pleistocene and Holocene lithofacies distributions in three sectors of study area. Note that section C-C' has a different horizontal scale than A-A' and B-B'.

depression during late Pleistocene as well as Holo­ late Pleistocene to early Holocene (Flandrian) cene times. marine transgression. An unconformity occurs at (7) Late Pleistocene to early Holocene shallow the base of the transgressive sands and is the re­ marine transgressive sands occur in the eastern sult of wave reworking of older, late Pleistocene study area (Figures 13, 14A-A'). These sands deposits. overlie older late Pleistocene alluvial sands and (8) An unconformity also occurs at the base of muds (COUTELLIER and STANLEY, 1987; ARBOU­ the Holocene section throughout the study area. ILLE and STANLEY, 1991; STANLEY et al., 1992; Holocene deltaic and coastal sediments began to CHEN et al., 1992). Transgressive sands terminate accumulate above the hiatus '"'-'7,500 years ago as near the southern margin of the modern Idku the rate of sea-level rise markedly decelerated. lagoon, and record the southwestern limit of the (9) Radiometric dates indicate that onset of

Journal of Coastal Research, Vol. 9, No. 1, 199:~ ~ Evolution of the NW Nile Delta 53

Holocene sedimentation above the hiatus oc­ EVOLUTION OF LAKE MAREOTIS AND curred earlier in the eastern sector than in the MODERN MARYUT LAKE western sector of the study area. The absence of early Holocene sediments in the west may be at­ Early History tributed to emergence of that region during that Lake Mareotis, precursor of Maryut lake, was time (Figure IIA). the largest geomorphic feature in the study area (10) Holocene sequences above the unconfor­ during the middle and late Holocene. Prior to this mity thin from northeast to southwest across the time, the region was a subaerially-exposed de­ study area (Figures 11, 14A-A') which also sug­ pression bound to the northwest by elevated car­ gests emergence in the south and west. bonate Ridge II. During the late Pleistocene, when (11) Holocene sediments tend to be marine sea level was generally lower, most of this pre­ coastal in the east and terrestrial in the west. It Mareotis basin was a seasonally flooded alluvial is of note that no open marine, deep water facies plain in which calcareous and gypsiferous sandy (e.g., prodelta and delta-front) of Holocence age muds accumulated (CHEN and STANLEY, in press). occur in the study area. Radiocarbon-dated core sections indicate that (12) Middle and late Holocene lagoon deposits Lake Mareotis had developed by at least 6,100 occur throughout the study area and demonstrate years BP. At about that time, climate was becom­ that, until recently, coastal wetlands were the pre­ ing more arid so that grasslands of the Libyan dominant ecosystem of the northwestern Nile del­ desert to the southwest were disappearing, ta plain. prompting herdsmen to immigrate to the more (13) Holocene lagoon deposits are marine-in­ temperate Mareotis region (DE COSSON, 1935). By fluenced in the east and fluvially-influenced in the ---5,000 years ago, the Lake Mareotis region was south and west. Differences between these two an important fishing and agricultural center, as subfacies are subtle and the transition between well as the first major port of the early dynasties them is highly gradational. of Egypt (NEWBERRY, 1908). Historic records in­ (14) Holocene fluvial sands interfinger with dicate that early Mareotis was a freshwater lake brackish water bay and lagoon muds in the east­ (DE COSSON, 1935); however, analysis of mollus­ ern portion of the study area (Figures 18, 14A­ can faunas demonstrates that the lake was more A'). These sands were deposited by the former likely a mixed freshwater-brackish water body Canopic channel (CHEN et al., 1992). (M.P. BERNASCONI, written communication, 1992). (15) The Holocene sabkha and alluvial fan de­ From ---6,000 to 800 years BP, the surface of posits, in core S-85 (Figures 13, 14A-A'), are in­ Lake Mareotis was at about sea level and covered terpreted to have accumulated near the edge of --700 km-, extending more than 40 km southeast Lake Mareotis along the northern slopes of Ridge of Alexandria and 70 km southwest between Ridg­ III. es II and III, beyond Abu Sir (Figure 15). Ar­ (16) Holocene nearshore marine (closed-basin) cheological records show that lake depths during muds in the harbor district of Alexandria were this period were sufficiently deep that ships could deposited in a basin which was separated from enter from the River Nile, traverse the lake and the Maryut depression by Ridge II (Figures 13, dock at southern Alexandria, and even at Abu Sir 14B-B'). This basin has subsided nearly 25 m (DE COSSON, 1935). Our analysis indicates that (rates of ---0.3cm/yr) during Holocene time (Fig­ Lake Mareotis was deeper than the other Nile ure 14C-C'). These subsidence rates are the high­ delta coastal water bodies because (1) large vol­ est in the study area and are comparable to rates umes of River Nile sediments were not delivered in the Rosetta promontory to the east (CHEN et to this depression and (2) the region was locally al., 1992). It is of note that the barrier that sep­ subject to subsidence. arates the Eastern and Western harbors is arti­ It remains unclear from historic records how ficial (JONDET, 1916; MORCOS, 1985) which implies and where Lake Mareotis was supplied with ma­ that the two Holocene sediment wedges in the rine and fresh water. Maps older than 2,000 years harbor area (Figure 11) were once united. (e.g., those of Herodotus and Strabo) do not show (17) Thick sections of artificial fill in the upper any channel or canal connecting the River Nile parts of borings 8-80 and E-1 to E-5 are yet an­ with Lake Mareotis (TOUSSOUN, 1922; SAID, 1981). other indication of extensive alteration of this re­ More recent maps (such as that of Serapion), how­ gion by human activity. ever, show a canal extending from the Canopic

Journal of Coastal Research, Vol. 9, No.1, 1993 54 Warne and Stanley

Figure 15. Map of the northwest Nile delta showing (1) extent of former Lake Mareotis, (2) trace of former Canopic channel, (3) artificial outlet near El Max, (4) trace of two branches (El Hagir and Naukratis canals) of the former Canopic channel which supplied River Nile water to Lake Mareotis, (5) location of the ancient Greek city of Naukratis and (6) present-day El Noubariya and El Mahmudiya canals. Outline of lagoons is modified from Jacotin (1818). channel to the southeast end of the lake. Maps of Mareotis was connected to the River Nile, and the early nineteenth century also show a canal that there were periodic incursions of marine wa­ extending from the Rosetta channel to the lake ter resulting in brackish conditions. Significant (ARROWSMITH, 1802, 1807; Du BOIS-AYME, 1813; fluvial input into the region is suggested by the JACOTIN, 1818). According to DE Cossox (1935), frequency distribution of light minerals (mostly it is generally accepted that a canal extended from quartz), the dominant sand component through­ the city of Naukratis to the southeast end of Lake out most of the study area (Figure 8D). Notable Mareotis, near the village of El Barnugi (Figure proportions of heavy minerals and mica (Figure 15). He also suggested that a second channel fol­ lOA and B) also record terrigenous input; their lowed the course of EI Hagir canal. An artificial distributions indicate input was predominantly outlet through Ridge II near EI Max (whose base from the southeast. High proportions of shell and was slightly above sea level) prevented Lake shell fragments (Figure 8C) indicate that terrig­ Mareotis from overfilling and endangering the Al­ enous sediment input was sufficiently low that exandria region during floods (JACOTIN, 1818; shell-forming organisms proliferated. The pres­ SHAFEI, 1952). ence of verdine/glauconite and foraminifera (Fig­ Petrologic data analyzed in the present study ure lOC and D) indicate that Lake Mareotis ex­ indicate that from '"-6,000 to 800 years ago, Lake perienced at least some marine influx; frequency

Journal of Coastal Research, Vol. 9, No. 1, 199:~ Evolution of the NW Nile Delta 55 distributions of these two components indicate industrial wastes from several outfalls in the marine waters entered from the northeast. Low northeastern sector of the lake. Untreated wastes proportions of vegetal matter in core samples have rendered Maryut lake highly polluted and (Figure IOE) suggest that these borings were re­ partially eutrophic (W AHBY et al., 1978; AB­ covered from what were once the central, deeper DEL-KADER, 1982; SAAD et al., 1984). Once highly portions of Lake Mareotis, which were at some productive, fishing yields have declined from 7,000 distance from lake margins and marsh plant tons in 1962 to 1,000 tons in 1978, mainly because thickets. of pollution (W AHBY et al., 1978). Nonetheless, Historic records indicate that all canals linking the lake supplies --- 22 ~(J of the fish caught in Lake Mareotis to the Canopic and Rosetta chan­ Egypt's brackish water lakes and lagoons (ABouL nels silted up by the twelfth century so that lake DAHAB et al., 1990). levels fell and the region became a series of salt Several investigators (e.g., ALEEM and SAMAAN, lakes and sabkhas. Without a fresh water supply, 1969a; EL-WAKEEL and WAHBY, 1970; SAAD, 1972; Alexandria declined in importance until Mo­ WAHBY et al., 1978; SAAD et al., 1982) recognized hamed Ali Pasha reconstructed EI Mahmudiya four Maryut lake sub-basins which are separated canal in 1820. Because Maryut depression did not by artificial embankments (Figure 6, inset). With receive water from Abu Qir lagoon or EI Mah­ construction of more canals and causeways, these mudiya canal, lake levels remained low, except four sub-basins have been further subdivided into from 1801 to 1804 and 1807 to 1808. At these two >6 sub-basins (Figure 6). In addition to these six times, the dyke between Maryut depression and sub-basins, the Hydrodrome, west-central and former Abu Qir lagoon was breached for tactical western sub-basins are considered to be part of military purposes, and the depression filled with the Maryut depression (Figure 4) because they sea water (DE COSSON, 1935). are subsea-level water bodies that were once part It is of note that the early nineteenth century of Lake Mareotis (DE COSSON, 1935). To record maps of ARROWSMITH (1802, 1807), Du BOIS-AYME the extensive influence of man and to document (1813) and JACOTIN (1818) portray Maryut during the accelerating changes affecting Maryut, that its briefperiod of inundation by the sea. However, could serve for future reference, a brief descrip­ in 1808 the barrier between Maryut and Abu Qir tion of each of the nine Maryut sub-basins is given lagoon was restored and the lake dried up again below. until 1892 when the irrigation sytem of the Be­ EI Nouzha Hydrodrome sub-basin is ---4.8 km2 heirah district (northwestern N-ile delta) was or­ with an average bottom depth of 3.65 m below sea ganized and several canals flowed into, and once level, and water surface level maintained at about again filled the depression with water, creating 0.6 m below sea level. Chlorosities are quite low Maryut lake. Later, pumps were installed at EI and range from 0.1 to 0.4 gil (KERAMBRUN, 1986). Max to control the size of the lake by keeping The Hydrodrome was separated from Maryut lake levels at about 2.8 m below sea level. in the late 1930's to form a seaplane airport (SAAD et al., 1985). It receives its water from the rela­ Recent Evolution of Maryut Lake and the Role of tively unpolluted Mahmudiya canaL The Hy­ Man drodrome sub-basin currently serves as a fish farm Modern Maryut lake levels are still maintained (KERAMBRUN, 1986). at --2.8 m below sea level by pumping from the The northern sub-basin is ---29.4 km2 with lake to the sea at EI Max. The lake currently depths between 0.9 and 1.5 m, and chlorosities covers --90 km 2 which is 13 ~\J of the size it would between 1.1 and 2.6 gil (KERAMBRUN, 1986). This be if the water surface was at sea level. The central su b- basin is heavily polluted by industrial wastes portions of Maryut lake (the northern, south­ from El Qalaa drain, and untreated sewage from eastern, southern, southwestern, central and east­ municipal and industrial outfalls (ALEEM and SA­ central sub-basins in Figure 6) receive most of its MAAN, 1969a; EL-WAKEEL and WAHBY, 1970; SAAD, water from EI Qalaa drain (Figures 1, 2). It also 1972, 1983a,b; SAAD, 1980; WAHBY and ABDEL receives water from EI Umoum drain through sev­ MONEIM, 1979; MITWALLY, 1982; SAAD et al., 1981; eral breaks in the embankment separating the SAAD et al., 1982; SAAD et al., 1984; SAAD et al., drain course from the lake. Maryut lake is the 1985). Moreover, the eastern and southeastern receptacle for large volumes of untreated indus­ margins of this sub-basin are solid waste disposal trial wastes from El Qalaa drain, and sewage and sites for the city of Alexandria (Figure 2). Two

.Iournal of Coastal Research, Vol. 9, No.1, 1993 56 Warne and Stanley other sources of pollution in this sub-basin are the southern end of both the east-central and cen­ the EI Noubariya canal (such as tin from paint of tral sub-basins are industrialized. The west end barges and ships; ABOUL DAHAB et al., 1990) and of the central sub-basin is a continuous embank­ air (including mercury fallout from industries at ment, so that waters of the central and west-cen­ EI Max and EI Dekheila; ELSOKKARY, 1989). Bot­ tral sub-basins do not mix. tom sediments are generally dark gray (N3) clayey The west-central sub-basin is '" 85 km' and is silt in the northeastern, and shelly silt and clay a commercial salt pond which produces r- 1,000,000 in the remainder of the sub-basin (EL-W AKEEL kg of unrefined salt per year (H.Z. HANAH, per­ and WAHBY, 1970; SAAD, 1980). These sediments sonal communication, 1992). Water is maintained contain large amounts of H 2S. In the western por­ at salinities of 92 gil in the main body of this sub­ tion of this sub-basin, floating Phragmites and basin (Figure 51); concentrations are regulated by Typha thickets are widespread; these thickets are adding Mediterranean seawater through two un­ currently being cleared to accommodate fish derground pipes. The color of this brine is light ponds. red (5R 6/6), from red algae cysts (Artemia) and The southeastern sub-basin is "'4.2 km" with microscopic shrimp. The 92 gil brine is dried and water depths of 0.9 to 1.5 m, and chlorosities of salt extracted in fifteen shallow pans (H.Z. HAN­ 1.1 to 2.6 gil (KERAMBRUN, 1986). This sub-basin AH, personal communication, 1992). is relatively unpolluted and serves as a fish farm The western sub-basin, segregated on the (WAHBY et al., 1978). Bottom sediments are pri­ southwest and northeast ends by causeways (Fig­ marily composed of dark gray (N3) shelly silt and ures 2, 6) is a complex of sabkhas and shallow clay (EL-WAKEEL and WAHBY, 1970). This sub­ playas whose relative size varies according to sea­ basin has some floating thickets at its western end son. The western sub-basin receives its waters from (Figure 2). groundwater seepage and runoff. The surface of The southern and southwestern sub-basins (the this sub-basin is dry for much of the year (es­ southwestern basin of ALEEM and SALAAM, 1969a) pecially in the summer). Sediments from this sub­ cover r- 12.6 krn-, and are partially divided by EI basin generally include halite and gypsum crusts Noubariya canal, although breaks in the canal at the surface (during the dry season) and gyp­ embankments allow water to pass from one sub­ siferous loess below. Pelecypod (Cardium) fossils basin to the other. Water depths are "'0.9 to 1.5 are common, and are relicts of former Lake Mar­ m, and chlorosities are 1.1 to 2.6 gil. Bottom sed­ eotis (DE CaSSON, 19~)5; ALI and WEST, 1983). The iments are primarily dark gray (N3) shelly silt floor of the western sub-basin is generally flat and and clay, and silty clay (EL-WAKEELand WAHBY, sparsely covered with halophytic plants. A com­ 1970). Large portions of these two sub-basins are mercial fish pond has been constructed at the covered with floating thickets of Phragmites and northeast end of the sub-basin (Figure 2). other marsh plants. Subaqueous macroscopic al­ Maryut lake and associated wetlands continue gae is also common (ALEEM and SALAAM, 1969b). to be reduced in size by land reclamation projects The southern portion of the southwestern sub­ and subdivision by canals and causeways. It is basin is industrialized; ABDEL-KADER (1982) re­ also of serious concern that large portions of the corded considerable wetland loss in this portion lake are increasingly polluted with industrial and of the sub-basin. municipal wastes. These actions have resulted in The central and east-central sub-basins (the a significant decrease in the lake fish productivity northwest basin of ALEEM and SALAAM, 1969a) and are contributing to increased health hazards cover "'8.4 km'', These two sub-basins are par­ for the region. tially separated by a canal; however, breaks in the canal embankments permit passage from one sub­ PALEOGEOGRAPHY AND CONCLUSIONS basin to the other. Their relatively unpolluted Subsurface distribution of late Pleistocene and waters have depths of 1 to 1.5 m and chlorosities Holocene lithofacies in the Alexandria region have of 1.1 to 2.6 gil (KERAMBRUN, 1986). Bottom sed­ been defined on the basis of petrologic, biogenic iments are primarily dark gray (N3) shelly silt and radiometric analyses, and remote sensing. A and clay (EL-WAKEEL and WAHBY, 1970). These paleogeographic synthesis is derived from inte­ two sub-basins are primarily open water lakes, but gration of these data with the well-documented the northern portion of the east-central sub-basin archeologic record of the Alexandria region. Of is marshy. The northern end of the central, and particular concern are factors which control sed-

Journal of Coastal Research, VoL 9, No. 1, 199:~ Evolution of the NW Nile Delta 57

'-4000-3000 E years B.P.

Figure 16. Series of time-slice paleogeographic maps showing late Pleistocene to recent evolution of northwestern Nile delta and adjacent coastal region near Alexandria (explanation in text). iment distribution, that is sea level, tectonism, southwest. Paleogeographic analysis also serves climate, sedimentary processes and, more recent­ to differentiate the relative influence of natural ly, man. and anthropogenic factors on sedimentation, and With regard to late Pleistocene deposits and thus provides a means to better evaluate man's their distribution, this study has focused on the role on the Alexandria region at present and in origin of: (1) siliciclastic sands in the eastern, mixed the future. siliciclastic-carbonate sands in the central and During the late Pleistocene, prior to 35,000 years carbonate sands in the western sector of the study BP (Sicilian to late Monasterian), a series of area, (2) stiff muds and (3) paleochannel systems. prominent nearshore marine to coastal dune ridg­ Facies analysis reveals that marine transgres­ es were deposited in this region. These carbonate­ sive sands of latest Pleistocene to Holocene age rich sands accumulated during a series of sea -level are localized in the eastern sector of the study highstands. Minor sea-level fluctuations affected area. Moreover, distributions of Holocene sec­ the development of each ridge, and resulted in tions show: (1) brackish water bay muds in the intermittent subaerial exposure and subsequent northeast, (2) fluvial sands in the east, (3) marine­ caliche and paleosol development. During time of influenced muds in the east and fluvially-inftu­ ridge formation, back-barrier lagoons and sab­ enced muds in the southwest, (4) carbonate-rich khas developed in depressions on the landward sabkha and alluvial fan sands in the west, and (5) side of the ridges; mud and gypsum accumulated reduced depositional sequences in the southern in these depressions. The entire ridge complex has and western sectors. been subsequently uplifted and tilted to the north Mapping of subsurface lithofacies and paleoen­ and northeast. vironments is useful for interpreting geomorphic Evolution of the Alexandria region during the features in the Alexandria region, such as: (1) the past ---35,000 years is summarized in a series of distinctive coast which includes siliciclastic sand time-slice paleogeographic maps (Figure 16). flats in western Abu Qir bay, seacliffs and pocket From ---35,000 to 11,000 years BP, the coast in beaches from Abu Qir to EI Dekheila, and exten­ the Alexandria region migrated seaward from near sive, oolitic beaches from El Dekheila to Abu Sir; its present location to as much as 20 km to the (2) karns to the south of Ridge III; (3) sabkhas in northwest (near the shelfbreak) during the latest inner ridge depressions; and (4) semidesert in the Pleistocene lowstand (---20,000-18,000 years BP),

Journal of Coastal Research, Vol. 9, No.1, 1993 58 Warne and Stanley and then landward (southeastward) to about the branches carried only a fraction of the sediment present-day midshelf. During this period, the area load of the Canopic branch and thus Lake Mar­ was a subaerially exposed coastal and alluvial eotis remained a sediment-starved deep water la­ plain. A NNW-trending, primarily braided river goon. During this period, the climate was becom­ channel system (pre-Canopic) flowed across the ing more arid. alluvial plain to the present-day shelf edge (MAL­ By ---4,000-3,000 years BP, sea level steadily DONADO and STANLEY, 1979). The major river rose to --- 3-4 m below its present level. As the channel was periodically inundated by brackish result of rising sea level and subsidence, Lake water during intermittent sea-level rises (CHEN Mareotis spread further to the south. During this et al., 1992). This was the westernmost channel time, the Canopic branch migrated westward as complex of the River Nile system during the late far as the eastern margin of Abu Qir lagoon, just Pleistocene. The mixed siliciclastic-carbonate east of Abu Sir Ridge II. It is of note that the sands in the central study area record the tran­ course of the channel during this period nearly sition from alluvial plain to the east and desert coincided with the course of the late Pleistocene, coastal plain to the west. The Maryut region was pre-Canopic channel. Although climate had be­ a depression during this period in which relatively come arid, the southwestern portion of the study thick and widespread floodplain sandy muds ac­ area was a thriving agricultural region (DE COSSON, cumulated. Gypsum and calcareous nodules, and 1935). the physical properties of these muds, record al­ By ---2,000 years BP, the Canopic branch was ternating wet and dry conditions in a generally diminishing as a significant Nile distributary, and arid climate (CHEN and STANLEY, in press). the Rosetta (Bolbitic) branch was being artifi­ From '"'-'11,000 to 8,000 years BP, the coast mi­ cially excavated (ct. SAID, 1981). However, Lake grated from the present-day midshelf landward Mareotis continued as a deep, mostly fresh water (southeastward) as sea level continued to rise rap­ lake, perhaps the result of excavation of the canal idly. As shoreline transgressed landward, late between the city of Naukratis and the lake (cf. Pleistocene sediments were reworked by coastal DE COSSON, 1935). Alexandria had become a ma­ waves and currents which resulted in deposition jor eastern Mediterranean port, with harbors on of nearshore marine shoreface and beach sands. both Lake Mareotis and the Mediterranean Sea. Rapidly rising sea level caused the shoreline to EI Mahmudiya canal had been constructed by this transgress into the eastern part of the study area. time and may have isolated the fluvially- from the Eventually, the rate of sea -level rise began to de­ marine-influenced portion of the lagoon. A system celerate, transgression halted and much of the of wells and cisterns was constructed in the south­ region became a surface of nondeposition (and western portion of the study area to enhance ag­ probably erosion in the south and west). Available ricultural output in this arid region. subsurface data do not provide information about By 800 years BP (1200 AD), the Canopic branch river channels in the study area duringthis period. and EI Mahmudiya canal had filled with silt so The climate was generally more humid at this that the supply of fresh water to the Alexandria time. region was markedly diminished. As a result, Mar­ At ---7,500 years BP, the rate of sea-level rise eotis lake level fell and the depression became the began to decelerate, and brackish water bay and site of salt lakes and sabkhas. Alexandria declined lagoon muds accumulated in the eastern portion in importance as a port and trade center. The of the study area. Most of the region to the south once-rich agricultural regions to the south and and west remained subaerially exposed in a rel­ west of Alexandria disappeared as the result of atively humid climate. increasing aridification and decay of the Greco­ By '"'-'6,000 years BP, much of the area was cov­ Roman system of wells and cisterns (DE COSSON, ered by brackish and fresh water. The central 1935). Fresh water was reintroduced into Maryut portion of the region was a fluvially-influenced depression in the late nineteenth century by di­ lagoon (Lake Mareotis), whereas the eastern por­ verting artificial drains to this region. Lake levels tion evolved into a marine-influenced lagoon. The are currently maintained at nearly 3 m below sea fluvially-influenced portion of the lagoon was fed level by pumping water from the lake to the Med­ by one or more minor branches of the Canopic iterranean sea. Large portions of Maryut lake, and channel which flowed into the southeastern por­ all of Abu Qir lagoon, have been drained and are tion of the lagoon (Figure 15). These minor currently being cultivated.

Journal of Coastal Research, Vol. 9, No.1, 1993 Evolution of the NW Nile Delta 59

In summary, the present study demonstrates andria (especially K. el Adm and M. Rodziewicz) that the boundary between the Nile ftuvial system for their hospitality and use of the library. Drs. to the east and the desert coastal region to the D. Arbouille and G. Randazzo assisted with drill­ west has not significantly shifted since late Pleis­ ing operations, and Drs. Z. Chen and F. Hamza tocene time. During the mid- to late Holocene, contributed to the petrologic study of some bor­ Lake Mareotis was a ftuvially-inftuenced lagoon ings used in this investigation. Messrs. W. Boy­ and, therefore, an integral part of the Nile delta kins and J. McRea assisted with analyses at the system. The western edge of the Nile delta is now Sedimentology Laboratory-NMNH. Identifica­ obscured by irrigation projects which have arti­ tion and interpretation of molluscan assemblages ficially expanded the cultivated surface westward in selected core samples were made by Dr. M.P. and southwestward onto former desert. Bernasconi. The manuscript was reviewed by Drs. This investigation reveals that the Alexandria Z. Chen and J.-L. Loizeau. Generous funding for sector has been increasingly controlled by man this study was provided by grants from the Smith­ and that the anthropogenic factor is now the dom­ sonian Scholarly Studies Program, Office of the inant control on coastal plain evolution and de­ Smithsonian Assistant Secretary for Science, U.S. positional patterns. Unlike other Nile delta sec­ National Museum of Natural History, National tors to the east where natural factors are the Geographic Society Committee for Research and dominant control on the evolution of the Nile Exploration, and ELF-Aquitaine, Washington. coastal region, it seems inevitable that wetland loss will continue and pollution increase as the LITERATURE CITED Alexandria region copes with its rapidly growing ABDEL-KADER, A., 1982. Landsat Analysis of the Nile population and increasing industrialization. Nat­ Delta, Egypt. M.Sc. Thesis, Univ. of Delaware, New­ ural factors are also of serious consideration. It ark, Delaware, 260p. ARDEL-MoATI, A.R. and EL-SAMMAK, A.A., 1988. Geo­ may be necessary, for example, to augment coastal chemistry of short core sediments off Alexandria re­ structures along the Abu Qir bay coast to prevent gion. Rapports et Proces-oerbaux des Reunions, marine inundation into low lying regions. Even Commission Internationale pour l'Exploration then, marked accentuation in sea-level rise, land Scientifique de la Mer Mediterranee, 31.2, 107. ABDEL WAHAB, H.S. and STANLEY, D.J., 1991. Clay min­ subsidence or earthquake activity could result in eralogy and the recent evolution of the north-central inundation of Abu Qir and Maryut depressions. Nile delta, Egypt. Journal of Coastal Research, 7, Saline groundwater incursion in low-lying regions 317-329. is likely to increase. ABOUL DAHAR, O.A., 1988. Speciation of tin compounds Fortunately, the expanding Abu Qir-Alexan­ in sediments of the Alexandria coast belt. Water, Air, and Soil Pollution, 40, 433-441. dria-El Dekheila-EI Agami urban center is posi­ ABOUL DAHAB, O.A.; EL-SABROUTl, M.A., and HALIM, tioned on a carbonate ridge which lies several me­ Y., 1990. Tin compounds in sediments of Lake Mar­ ters above sea level. Expansion of irrigation yut, Egypt. Environmental Pollution, 63, 329-344. projects into desert (which is well above sea level) ABU-ZEID, M.M. and STANLEY, D.J., 1990. Temporal and spatial distribution of clay minerals in Late Quater­ to the south and southwest of Alexandria is a nary deposits of the Nile delta, Egypt. Journal of reasonable course of action for future develop­ Coastal Research, 6, 677-698. ment of this region. ADAMSON, D.A.; GASSE, F.; STREET,F.A., and WILLIAMS, M.A., 1980. Late Quaternary history of the Nile. Na­ ACKNOWLEDGEMENTS ture, 288, 50-55.

ALEEM, A.A. and SAMAAN t A.A., 1969a. Productivity of Prof. A. Bassiouni, Ain Shams University, Cai­ Lake Mariut, Egypt. Part 1. Physical and chemical ro, and Dr. B. Issawi, Under Secretary for State, aspects.lnternationale Revue der Gesamten Hydro­ Cairo, are thanked for providing support for the biologie, 54(3), 313-355. Nile Delta Project and for facilitating all aspects ALEEM, A.A. and SAMAAN, A.A., 1969b. Productivity of Lake Mariut, Egypt. Part II. Primary production. In­ of the field work. Appreciation is expressed to ternationale Revue de Gesamten Hydrobiologie, 54 Eng. A. Madi, Mr. M. Harnzawi and the two drill (4), 491-527. crew teams of MISR Raymond Foundations in ALEXANDERSSON t T., 1990. Holocene shelf sedimenta­ Ismailia for efficient drilling of the borings. We tion on the western Egyptian shelf. Rapports et Proces­ thank Mr. H.Z. Hanah, general manager of the verbaux des Reunions, Commission Internationale pour l'Exploration Scientifique de la Mer Mediter­ Nasr Salt Works, for providing information on ranee, 31.2, 108. salt production in the Alexandria area. Weare ALI, Y.A. and WEST, I., 1983. Relationships of modern grateful to the Archaeological Society of Alex- gypsum nodules in sabkhas of loess to compositions

Journal of Coastal Research, Vol. 9, No.1, 1993 60 Warne and Stanley

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