mica and heavy minerals as markers to map nile delta coastline displacements during the holocene

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Mica and Heavy Minerals as Markers to Map Nile Delta Coastline Displacementsduring the HoloceneAuthor(s): Jean-Daniel Stanley and Pablo L. ClementeSource: Journal of Coastal Research, 30(5):904-921. 2014.Published By: Coastal Education and Research FoundationDOI: http://dx.doi.org/10.2112/JCOASTRES-D-14A-00003.1URL: http://www.bioone.org/doi/full/10.2112/JCOASTRES-D-14A-00003.1

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Mica and Heavy Minerals as Markers to Map Nile DeltaCoastline Displacements during the Holocene

Jean-Daniel Stanley* and Pablo L. Clemente

Cities under the Sea Program (CUSP)Department of PaleobiologyNational Museum of Natural HistorySmithsonian InstitutionWashington, DC 20013, U.S.A.

ABSTRACT

Stanley, J.-D. and Clemente, P.L., 2014. Mica and heavy minerals as markers to map Nile Delta coastline displacementsduring the Holocene. Journal of Coastal Research, 30(5), 904–921. Coconut Creek (Florida), ISSN 0749-0208.

Mica and heavy minerals in sediments of Egypt’s Nile Delta are examined to test if measured proportions of these twomineral groups and their distributions can be used to define former coastline positions and their shifts in time and spaceduring the Holocene. The premise of the study is based on the sufficiently different attributes of these two components,especially their shape, density, and size, which could induce their segregation and dissimilar dispersal patterns duringsediment transport. To test this hypothesis, mineralogical data from more than 1400 samples from 87 sediment coresrecovered across the northern third of the delta margin were analyzed. The marked contrast in both temporal and spatialdistributions of high proportions of mica and of heavy minerals indicates distinct separation occurred primarily north ofthe central delta, in an area from ~45 km south of the present shoreline to ~10–15 km offshore during the time spanconsidered. Additionally, detailed examination of core sediment types demonstrates a relationship between theproportions of these two mineral groups and proportions of clay, silt, and sand fractions in which they occur near thepresent coast. Mica is preferentially deposited with silt and clay landward of the modern shore, while heavy mineralconcentrations are generally associated with coarser silt and sand near and seaward of the shoreline. Shifts of the NileDelta margin have been triggered by natural processes leading to insufficient sediment replenishment: relative sea-levelrise involving delta plain subsidence and shoreline erosion, and intensified human activity, especially during the pasttwo centuries, such as construction of dams, barrages, and entrapment by the delta’s expanded canal system. Theapproach used here helps define two of the three major earlier Holocene coastal shifts, and it could be used to measureongoing and future landward shoreline advances onto the delta plain.

ADDITIONAL INDEX WORDS: Climate change, coastal processes, grain density, grain shape, human interference, Nilebranches, northern delta, provenance, relative sea level, relict distributaries, salinization, shoreline shifts, sedimentreplenishment, subsidence.

INTRODUCTIONThis investigation examines two major coastal margin

migrations of the northern Nile Delta during the Holocene,

an earlier one advancing to the north, and a second reverting to

the south. To date, most studies of this delta’s shoreline shifts

along the Mediterranean have focused on factors recently

affecting the coast and its contiguous submerged areas

offshore. There have been far fewer investigations of the Nile’s

coastal migrations based on observations made in the delta’s

northern plain landward of the present shoreline. Our

evaluation of temporal and spatial shoreline shifts in this

region is based on analysis of a newly examined mineralogical

database acquired from sediment cores. This data set is

complemented by information on the Nile’s hydrographical

parameters and coastal processes collected by others at the

shoreline and along nearshore sectors of the Nile shelf.

As has been shown in studies of many of the world’s other

large fluvio-deltaic depocenters, major natural factors that

have controlled the Nile Delta margin’s position and configu-

ration in Holocene time include: climate change and rising sea

level; erosional cutback of low-lying unconsolidated terrains by

active coastal processes; and subsidence of delta plain surfaces

(cf. Broussard, 1975; Coleman, 1982; Coleman et al., 1981;

Wright and Coleman, 1973). In addition to these parameters,

human activity and interference of Nile flow have increasingly

affected this delta’s margin in more recent time, causing

marked decrease of sediment replenishment at and near the

coast. Egypt’s population has grown rapidly, reaching nearly

85 million, with the majority (~60%) highly concentrated in the

Nile Delta between Cairo and the coast (Figure 1A), and the

remaining mostly along the Nile Valley in Middle and Upper

Egypt. It is generally recognized by Egyptians living in the

delta, many experiencing economic hardship, that each new

pressure, whether the result of altered natural processes,

increased human activity, or both, tends to increase threats to

themselves and endanger their country’s most vital breadbas-

ket positioned in this low-lying coastal terrain. This has led to

Egypt’s increased concern with regards to changes that are now

modifying the delta’s coastal margin. Some of these changes

will likely have direct, rapid, and quite probably serious

ramifications in the near future if sea level continues to rise

and encroach farther inland onto the delta plain (Bohannon,

2010; Sestini, 1992; UNDP, 2009).

D O I : 1 0 . 2 1 1 2 / J C O A S T R E S - D - 1 4 A - 0 0 0 0 3 . 1 r e c e i v e d18 February 2014; accepted in revision 21 February 2014; correctedproofs received 9 April 2014; published pre-print online 29 May 2014.*Corresponding author: [email protected]� Coastal Education & Research Foundation 2014

Coconut Creek, Florida September 2014Journal of Coastal Research 30 5 904–921

Figure 1. (A) Google Earth image (2013) showing the Nile Delta bounded to the north by the Mediterranean and to the west and east by desert. Numerous small

towns and cities in the delta appear as light-colored, irregular spots. Numbers on image refer to the following: (1) calcareous ridges, (2) Mariut lagoon, (3)

Alexandria, (4) Abu Qir headland, (5) Abu Qir Bay, (6) truncated Rosetta promontory, (7) Burullus lagoon, (8) Burullus inlet, (9) Burullus headland, (10) Baltim

outlet, (11) high migrating dune fields, (12) Gamasa, (13) Ras El-Barr, (14) truncated Damietta promontory, (15) Damietta promontory spits, (16) Manzala lagoon,

(17) Port Said–Suez Canal entry, (18) salt flats east of canal, (19) Suez Canal. (B) Cores recovered at sites S1 to S87 serve as a database for the present study

(Stanley, McRea, and Waldron, 1996). A¼Alexandria; B¼Burullus headland; Bu¼Burullus lagoon; DP¼Damietta promontory; I¼ Idku lagoon; KZ¼Kafr el-

Zaiyat; Man¼Manzala lagoon; Mar¼Mariut lagoon; PS¼Port Said; T¼Tanta.

Journal of Coastal Research, Vol. 30, No. 5, 2014

Using Mica and Heavy Minerals to Map Nile Delta Coastline 905

The main focus here is on petrologic information derived

from .1400 sediment samples obtained from numerous

continuous radiocarbon-dated core sections of Holocene age

recovered across the northern delta plain (Figure 1B). Special

attention is paid to the proportions of mica and heavy minerals

in the sand-size fraction of Holocene sections. Selection of these

two mineral groups is based primarily on their significantly

different responses to dynamic transport processes by fluvial,

marine, and eolian agents that have prevailed in the past and

continue to modify this depocenter. Theoretical, laboratory,

and field studies by geologists working in the modern sediment

record and in diverse geological formations have indicated that

some sand-size minerals, such as mica, can be more readily

displaced by currents for greater distances than some other

mineral types. It is also of note that mica has received much

less attention in Nile Delta studies than heavy minerals. With

its characteristic flake shape, mica, once in suspension, would

be carried farther in a flowing or agitated body of water, settle

less rapidly, and be displaced further along a dispersal path

than more spherical grains. These rounder grains are usually

dominated by quartz and feldspar, as well as some associated

denser minerals (especially heavy minerals) that tend to be of

equivalent or smaller size than the mica (Pettijohn, Potter, and

Siever, 1973).

During transport, mica would thus tend to be segregated

from denser heavy minerals of sand size and selectively

transported for greater distances away from sediment entry

points along the Nile in the lower delta and Nile distributary

mouths along the coast. The ability of mica to remain in

agitated or flowing water over longer distances relative to other

grains of the same size helps to explain the generally low

concentrations of mica of Nile River origin presently in the

delta’s coastal sediments. It also illustrates why greater

amounts of mica are deposited in finer-grained sediment of

Nile origin in deeper waters on the Israeli margin hundreds of

kilometers away from Nile Delta sources (Pomerancblum,

1966). In contrast, heavy mineral suites tend to form

concentrated lag deposits in coastal margin settings near the

Nile’s distributary mouths. Such concentrates of greater

densities prevail in seafloor areas reworked by strong bottom

currents and powerful episodic storm wave surges in the high-

energy settings between the inner shelf and the beach (Frihy

and Komar, 1993; Frihy, Lotfy and Komar, 1995).

We propose that mapping and comparing distributions of

these two distinct mineral groups in the subsurface sections of

the delta proper could provide some new information on earlier

positions of Holocene coastlines. Distinguishing their past

distributions in radiocarbon-dated core sections of the northern

delta plain may also offer some additional insight on the

present and future evolution of this now densely populated and

vulnerable low-lying region of significance to Egypt.

SETTING, COASTAL PROCESSES, ANDPROVENANCE

The following section aims to provide a broad framework for

interpreting the mineralogical data presented in this study in a

more comprehensive manner. The topics reviewed include the

basic stratigraphic evolution of the Holocene delta, coastal

processes that have modified its margin, and the provenance of

the delta’s components, including mica and heavy minerals and

major size fractions of the sediments with which these two

mineral groups were deposited.

Figure 2. Schematic of the northern delta and its contiguous coastline and inner shelf. The distribution of sediment types offshore is from Summerhayes et al.

(1978). Theþ1 m contour above msl (dotted line) is from Sestini (1989). Coastal sands on land at present are derived from a 2013 Google Earth image. Black

dashed line indicates the landward limit of the early Holocene coast as determined from core logs in Stanley, McRea, and Waldron (1996). Arrows indicate three

Holocene coastal shifts associated with three phases of the delta’s evolution: (I) landward retreat across the Nile shelf area in the late Pleistocene to early

Holocene; (II) seaward advance during the early Holocene, and through the mid-Holocene to early part of the late Holocene; and, (IIIa) return landward of the

coastline during the late Holocene from the present inner shelf, now submerged. Details reviewed in text.


906 Stanley and Clemente

Three Phases of Delta Coast DevelopmentThe geologic evolution of the Nile Delta’s shoreline during

the Holocene, and that of its adjacent sectors on land and its

contiguous submerged inner shelf, has likely involved three

major phases as schematically depicted by deltaic stratigraphic

models (cf. Curray, 1960; El Askary and Frihy, 1986; Scruton,

1960). These schemes have served to conceptualize the

development of some of the world’s large fluvio-marine deltas

and emphasize the interactive roles of increased sediment

discharge at the coast that can result in their seaward-directed

progradational build-out or their erosion and retrogradational

landward advance. The models identify a sequence of lateral

coastal displacements that essentially result from opposing

forces: a fluvio-delta’s accretion and extension into the marine

environment, and coastal processes that counter such deposi-

tional build-out and can lead to landward retreat of a delta’s

margin. As an example of the latter, it is likely that decreased

fluvial sediment input to the coast coupled with increased

eustatic or relative sea-level rise in conjunction with powerful

coastal marine erosional processes acting along shoreline

sectors would cause a delta-margin cutback. Such phases

involving alternations of seaward delta build-out and of delta

plain removal by erosion of sediment transported via river to

the shoreline are responsible for the multiple shifts of a deltaic

coast that commonly occur through time. Three of these

migrations are indicated by arrows in Figure 2.

During the Nile Delta’s first phase (I), extensive coastline

retreat southward occurred during the late Pleistocene to the

early Holocene, a period when sea level rose rapidly (rates to~1

cm/y) and advanced southward across the shelf platform. A

broad but irregular cover of coarse to fine sand, silt, and clay,

deposited across what was then a subaerial plain, subsequently

became the presently submerged Nile shelf surface positioned

north of the terrestrial depocenter (Stanley and Warne, 1998).

The delta front and shoreline formed in this micro–tidal sea

retreated to a position south of the present subaerial delta coast

(Figure 2, early Holocene, shown as black dashed line), as

recorded in cores by a basal unit largely composed of sand and

silt that dates from about 9000 YBP to 7000 YBP (Figure 2,

arrows depicting phase I). This basal unit in early Holocene

core sections is of modest but uneven thickness, sometimes

formed of reworked and mixed late Pleistocene and early

Holocene sandy deposits, and locally discontinuous due to its

partial erosion by coastal and bottom-current processes in this

actively displaced nearshore setting.

This major landward coastline retreat was followed by a

second phase (II) during which the delta experienced its major

sediment buildup (accretion, locally to nearly 50 m in

thickness) and seaward progradation with a re-advance of

the coast to north of the Nile’s modern subaerial depocenter

(Figure 2, arrows depicting phase II). A study of cores recovered

in the northern third of the present subaerial delta (Figure 1B;

Stanley and Warne, 1998) and those at sea (Summerhayes et

al., 1978) shows that the seaward build-out phase lasted~5000

years, extending from the early (~7500–6500 YBP) and mid-

Holocene to the early part of the late Holocene (~2000 YBP).

Deposition of thick delta-front and prodeltaic facies consists in

large part of fine-to-medium sand, with high proportions of silt

and muddy silt (Stanley and Warne, 1993, 1998; Summerhayes

et al., 1978; UNDP/UNESCO, 1976). One reason for this delta’s

fairly symmetrical arcuate build-out was the delta’s greater

volume of flow seaward during that period via numerous

distributary channels that were responsible for sediment

transported onto what is now the inner shelf. Relict branches

of the Nile that flowed to the coast during phase II may have

numbered as many as ten (Figure 3), but not all were active

simultaneously or of equal importance (Said, 1981; Toussoun,

1922). According to Herodotus’ The History (484–425 BC, 2.17;

translation by Grene, 1987), the branches that were still active

in Greek time as late as about the mid–fifth century BC were

the Canopic, Bolbitinic, Saitic, Bucolic, Mendesian, and

Pelusiac (Figure 3). He also calls special attention to the

importance of the Sebennitic branch, which flowed almost

directly northward to and beyond what is presently the

Burullus headland (Figure 1A, sites 8–9), and he suggests that

its channel was a major source of water flow to the coast,

dividing the delta into two halves. This major delta buildup and

seaward progradational phase included sediment deposited

during pre-Dynastic time (before ~5050 YBP) and lasted

through Egypt’s Dynastic and Ptolemaic periods to the first

century BC (Baines and Malek, 1985; Butzer, 1976).

The third, most recent phase (III) of delta development

(~2000 YBP to present, comprising what here is termed the

late Holocene) is characterized by changes of two natural

factors that, in earlier time, had largely controlled the Nile

Delta’s morphological and stratigraphic evolution. By the late

Holocene, (1) the rate of sea-level rise was substantially lower,

to between 1.7 mm/y and 3.0 mm/y (Lambeck and Purcell, 2005;

Sivan et al., 2001; Woppelman and Marcos, 2012), and (2) the

natural annual volume of Nile River flow and its sediment load

periodically decreased, largely as a response to regional climate

change in the Nile Basin, including cycles of marked aridifica-

tion (Bernhardt, Horton, and Stanley, 2012; Kropelin et al.,

2008; Marriner et al., 2012; Muhs et al., 2013; Said, 1993;

Zviely, Kit, and Klein, 2007). During this same period, the role

of a third controlling factor, (3) subsidence of the delta plain

surface, became increasingly apparent as a major parameter

affecting the delta’s coastline position (Becker and Sultan,

Figure 3. Nile distributaries, including traces of eight relict branches

(dashed lines) and two partially active ones (Bolbitinic/Rosetta and Bucolic/

Damietta). Some, such as the Sebennitic (5), formerly extended seaward of

the present coast. Map is adapted from Wright and Coleman (1973) and Ross

et al. (1978).



2009; El-Sayed, 1996; Stanley and Clemente, 2014; Stanley and

Corwin, 2013; Stanley and Toscano, 2009; Warne and Stanley,

1993a). Measured land-lowering rates in the northern delta

during the late Holocene (ranging from 3.7 mm/y to 8.4 mm/y;

Stanley and Corwin, 2013) locally began to exceed rates of

eustatic sea-level rise, as determined separately by geophysical

analyses in this general Mediterranean region (Lambeck and

Purcell, 2005). In parallel with significant rates of subsidence

and a relative sea-level rise of ~1 cm/y along the delta’s

northern margin in Greco-Roman (332 BC–AD 395) and

subsequent time, the shoreline retreated landward to its

present position (Figure 2, phase IIIa arrows).

Increased Effects of Human Activity and CoastalProcesses

Population in the delta is estimated to have increased from

about 80,000 at~6000 YBP, to~1.2 million at~3250 YBP, and

then to ~2.16 million at ~2150 YBP in Greek time (Butzer,

1976, his Table 4). From the latter part of phase II and during

the past two millennia (phase IIIa), Egypt’s population has

Figure 4. (A, B) Data on wave directions, wave heights, and wave refraction patterns along the Nile Delta margin. (C) Extent of erosion and accretion,

predominant coastal current directions, and definition of littoral subcells (I to V) in this area. Modified after Frihy and Dewidar (2003).



grown to about 85 million inhabitants at present, with most in

the delta and along the Nile (CIESIN, 2009; UNDP, 2009).

About 18 million are now concentrated in the Cairo region at

the delta’s southern apex, and population densities locally

exceed 1000/km2 in parts of the delta, including some coastal

sectors such as at Alexandria (5.5 million inhabitants) and Port

Said (.0.6 million inhabitants). The much-increased human

activity during phase IIIa along the lower Nile and in the delta

proper now constitutes a major controlling factor of Nile flow.

The resulting effect of anthropogenic influences is the almost

complete cutoff of sediments now carried to the coast by the

only two remaining and altered Nile branches, the Rosetta and

Damietta (Stanley and Wingerath, 1996). These two distribu-

taries, formerly the Bolbitinic and Bucolic, respectively, were

not natural but dug channels according to Herodotus’ The

History. Major changes to the delta’s margin have resulted

directly from emplacement of barrages across the Nile in Upper

and Middle Egypt, construction of the Low Dam at Aswan early

in the twentieth century, closure of the High Dam at Aswan in

1964–65, and near cutoff of freshwater flow into the Mediter-

ranean by closure of two dams ~30 km landward of the two

mouths of the Nile’s Rosetta and Damietta branches (Water-

bury, 1979). It is recalled that, before closure of the High Dam,

Nile sediments transported through the Rosetta and Damietta

branches varied from year to year in the range of 60–100

million tons. At present, only ~10% of the Nile’s flow actually

reaches to and seaward of the delta’s coast (Stanley and

Wingerath, 1996). This reduction has also resulted from almost

complete diversion of Nile flow north of Cairo and its

entrapment across the delta by thousands of kilometers of

canals and drains, and discharge into the partially closed

coastal lagoons (Bohannon, 2010). Such a marked depletion of

the Nile’s natural fluvial sediment supply to the northern delta

and the coast is now only partially offset by the volume of relict

Nile sand and silt displaced southward from offshore onto land

by coastal currents (Frihy, Debes, and El Sayed, 2003; Frihy

and Dewidar, 2003; Frihy and Lotfy, 1997) and by dust and fine

sediment from adjacent desert terrains and more distal regions

released over the delta by seasonal winds (Guerzoni and

Chester, 1996; Khatita, 2011).

In summary, the most recent phase (IIIa) of the Nile Delta’s

coastline change is a consequence of the interaction of the five

previously cited controlling factors: climate change and sea-

level rise, much reduced Nile sediment discharge to the coast,

subsidence of the delta plain, coastal processes, and increased

human activity. Coastal retreat has thus prevailed along many

sectors between the Alexandria region to the west and the

northeastern margin east of Port Said and the Suez Canal

south of the Gulf of Tineh (Figure 1). Of particular note are

combined effects of much decreased volumes of Nile sediment

reaching the coast (Said, 1993) combined with ongoing

nearshore to coastal marine erosive processes at present

(Figure 2, phase IIIa arrows). Many published studies

concerned with this subject have focused primarily on the

post–High Dam effects and related coastal margin evolution,

which have led to recent emplacement of coastal protective

structures to help reduce erosion rates. Much applicable

research has resulted from programs sponsored by UNDP/

UNESCO (1976, 1977, 1978), those of the Egyptian govern-

ment’s Coastal Research Institute at Alexandria, different

science departments at the University of Alexandria, and other

governmental and academic organizations. That work, detail-

ing physical oceanographic parameters and coastal dynamics,

has found that ongoing landward retreat of fluvio-marine delta-

front and prodelta depositional sectors results from a series of

interactive factors that prevail in the southeastern Mediterra-

nean. For example, dominant NW winds drive waves and

produce strong coastal currents toward the east (Figure 4C),

which can reach velocities as high as 100 cm s�1 to 150 cm s�1

(Abo Zed, 2007; El Din, 1974). Additionally, wave heights

reaching 2 m to 5 m can result from storms, especially in

winter, which can produce powerful land-directed surges

(Inman and Jenkins, 1984; UNDP/UNESCO, 1978; Figure

4A). Somewhat deeper bottom and geostrophic currents play a

role in reworking older (relict) Nile sediment on the shelf (El

Din, 1974, 1977; Frihy, 1992a).

In the early twentieth century, very rapid delta coastal

erosion resulted in remarkable shoreline retreat rates mea-

sured at~50–100 m/y along the Rosetta promontory, 10 m/y at

the Damietta promontory, and 5–10 m/y at the central

Burullus headland (Frihy, 1992a,b; Frihy and Deabes, 2011;

Frihy, Debes, and El Sayed, 2003; Frihy et al., 1994).

Substantial rates of sediment accretion were measured locally,

such as in Abu Qir Bay, as a result of significant erosion in

adjacent headland regions (Figure 4C). By ~20 years ago, it

was reported that an approximate average cutback of extensive

shoreline sectors accounted for 54% of the delta coastline, while

accretion occurred along much of the remaining 46% of the

coast (Frihy and Komar, 1993; Figure 4C). In recent years,

erosion rates have been significantly reduced at the more

vulnerable delta headlands following emplacement of coastal

protection structures (Frihy and Dewidar, 2003): at the Rosetta

promontory, �20 cm/y to �50 cm/y, and at the Burullus

headland and Damietta promontory, both at 0 cm/y to �20

cm/y. Accretion of sediment, some of it temporarily stored along

the coast, occurs at more modest rates, ranging from 0 cm/y to

40 cm/y between zones of erosion, such as the eastern Rosetta

margin, Gamasa embayment, and western margin of the Suez

Canal entrance at Port Said and south of the Gulf of Tineh

(Frihy and Dewidar, 2003; Figure 4C).

Heavy mineral concentrations, such as the so-called ‘‘black

sands’’ of economic value, comprise to as high as 70% to 90% of

the sand fraction and occur near the mouths of present as well

as former Nile distributaries subject to erosion (El Fattah and

Frihy, 1988; El-Hinnawi, Niazi, and Samy, 1989; Naim, El

Miligy, and El Azab, 1994). Heavy minerals and textural

attributes of sediment, such as size, have helped define five

sediment transport zones (I–V), termed subcells, along the

present delta’s coastal/nearshore zone, from Abu Qir in the

west to beyond Port Said in the east (Frihy and Dewidar, 2003;

Frihy and Komar, 1993; Frihy, Lotfy, and Komar, 1995; Figure

4C).

Provenance of Coastal Margin SedimentsThe texture and composition of sediments that prevail in the

northern delta study area and offshore, at least to as far as the

middle shelf, record a dominant Nile River origin, with

provenance from both White Nile sources in central Africa



and Blue Nile–Atbara headlands in the Ethiopian Plateau (El-

Hinnawi, Niazi, and Samy, 1989; Foucault and Stanley, 1989;

Hassan, 1976; Shukri, 1950, 1951; Shukri and Azer, 1952). The

similarity of heavy mineral suites in different late Pleistocene

to modern sand layers along the Nile, in the delta, and in the

inner to midshelf is primarily a function of mineralogical

homogenization during sediment transport. White Nile sedi-

ments are generally masked by dominant Blue Nile and Atbara

components, recycled together north of Khartoum in the Main

Nile, and by subsequent reworking of sediments between

different fluvio-marine environments in the northern delta

(Stanley, Sheng, and Pan, 1988).

The dynamics of multiple processes along the delta’s coastal

margin have further modified the original sediment attributes

both along the shore and shelf, including their original grain-

size distribution and mineralogical content (El-Fishawi and

Molnar, 1985; Frihy and Lotfy, 1994; Frihy, Lotfy, and Komar,

1995; Stanley, 1989). Studies conducted offshore have identi-

fied altered sediment texture and composition as related to the

Nile Delta’s coastal and offshore currents and seafloor

morphology (Coleman et al., 1981; Gheith et al., 1994; Sestini,

1989; Summerhayes et al., 1978) and also to the former coastal

discharge positions of now-relict Nile distributary branches

(Arbouille and Stanley, 1991; Coutellier and Stanley, 1987;

Frihy and Lotfy, 1994; Gheith et al., 1994).

Some offshore sediments examined on the broad expanse of

both inner and middle shelf are identified as older relict Nile

deposits released by the river’s flow on the subaerially exposed

shelf prior to ~9000–8000 YBP; these earlier deposits have

been covered locally by Nile deposits more recently released on

the Nile shelf (Stanley and Warne, 1998). These two sets of

sediment have been reworked, forming a palimpsest deposit

offshore during the Holocene as the delta’s coastline and inner-

shelf environments advanced seaward and then retreated

landward (Sestini, 1992).

Mineral counts of mica, comprising primarily biotite (densi-

ty, g/cm3: 2.8–3.2), have been recorded along the different Nile

sectors between central Africa source areas and the Sudan

northward to the delta coast and offshore, with average relative

percentages ranging from absent and trace amounts to 4% of

the sand fraction (El-Fishawi and Molnar, 1985; Frihy and

Gamai, 1991; Garzanti et al., 2006; Shukri and Azer, 1952).

Mica contents in Middle Egypt sediment (Bustamante-Santa

Cruz, 1995) and those in central Nile Delta deposits examined

in cores S86 and S87 (Figure 1B; this study) range from trace to

,2%. Mica contents along carbonate-enriched beaches west of

Alexandria comprise ,2% (Hassouba, 1995; Philip, 1976;

Shukri and Philip, 1956), and those in delta coastal sands east

of Alexandria generally range from trace amounts to ~3% (El-

Fishawi and Molnar, 1985; Gheith et al., 1994).

Heavy minerals in Nile deposits in the lower Nile basin north

of the African source areas (El-Hinnawi, Niazi, and Samy,

1989) comprise variable amounts (from few grains to .10%) of

the sand fraction. These are composed primarily of opaque iron

minerals, amphiboles, clinopyroxenes, and epidotes (Hassan,

1976; Shukri, 1951; Shukri and Azer, 1952), and they are

included in comprehensive listings that identify as many as 45

mineral species from source areas. The densities of these

mineral types are much higher, ranging from ~3.5 to .5.2

(such as hematite), than the dominant proportions of light

mineral fractions of lower densities with which they are

associated, primarily quartz (2.65) and feldspars (2.57–2.76).

The flake shape of mica and considerably higher densities of

more spherical heavy minerals contribute to segregation of the

two mineral types during transport in aqueous media, first by

the Nile River and then by marine currents along the coast and

inner shelf. Moreover, such displacements of considerable

volumes of sand- and silt-size sediment of Nile derivation and

their differentiated mica and heavy mineral contents have

reached eastward to as far as Israel, as recorded by mineral-

ogical analyses (Inman and Jenkins, 1984; Pomerancblum,

1966; Stanley, 1988; Zviely, Kit, and Klein, 2007).

METHODSThe present investigation takes into consideration the

information summarized in the previous section to help better

interpret the differences in separately mapped temporal and

spatial distributions of mica and heavy minerals during two

major depositional phases of the delta. To achieve this, two

major Holocene stratigraphic sequences of the northern Nile

Delta coastal plain margin are evaluated: (1) an older, thicker

underlying section between the base and 2 m from the core top,

termed Early to mid-Holocene (phase II), that ranges in age

from ~7500 YBP to ~2000 YBP; and (2) a younger overlying

late Holocene section, termed Upper 2 m (phase IIIa), dating

from early Roman time (~2000 YBP) to present. In this

manner, it should be possible to determine whether any notable

differences in the distribution patterns of mica and heavy

minerals of sand size can be identified in the two stratigraphic

sequences in the northern delta and coastline area.

The data utilized herein are derived from laboratory analyses

of numerous (1410) sediment samples taken from 85 drill cores

collected in the northern delta study area and also those from 2

cores recovered in the central delta (Figure 1B). The core sites

and boring numbers are officially recorded as S1 to S87, where

the letter S denotes recovery by the National Museum of

Natural History (NMNH), Smithsonian Institution, Washing-

ton, D.C. The continuous core sections were collected using

Acker II trailer-mounted rigs during five field seasons from

1985 to 1990 with detailed stratigraphic, sedimentological,

textural, and mineralogical data recorded and interpreted

across the northern delta, from east to west (Coutellier and

Stanley, 1987; Stanley et al., 1992; Arbouille and Stanley, 1991;

Chen, Warne, and Stanley, 1992; Warne and Stanley, 1993b).

The total depth of sediment borings ranges from ~20 m to ~60

m, and these include continuous and dated late Quaternary

chronostratigraphic sections that, in most cases, extend from

the late Pleistocene at their base to the late Holocene and

recent time at their top.

Attention in the present study is paid to the Holocene

sections, which range from~2 m to~49 m in length and extend

in age from approximately 8500 YBP to the present. Basal

Holocene sections that reach to the underlying Pleistocene

sequences range from ~8500 YBP to ~6500 YBP, but in most

cases ~7500–7000 YBP. These basal sections are generally

positioned unconformably upon older (usually 12,000 YBP or

greater) underlying late Pleistocene sandy deposits. To

examine representative deposits at each core site, the samples



were selected down-boring at each change of lithology, or at

about 50 cm intervals in the case of long homogeneous sections.

Microscopic analyses of the sand-size components (63 lm to

1000 lm fraction selected for this study) were performed on the

1410 Holocene samples, and based on mineral counts of 300 or

more grains identified in each sample. Detailed lithologic logs

of the 87 cores, radiocarbon dates, and textural and mineral-

ogical numerical data gathered for each sample are recorded in

a monograph published by the Smithsonian Institution

(Stanley, McRea, and Waldron, 1996).

Figure 5. (A) Percentages of the clay-size fraction in sediments that formed the northern Nile Delta region mostly during the early through mid-Holocene

(modified after Stanley and Clemente, 2014). Average rates of sediment compaction (ARC) for this period are from Stanley and Corwin (2013). (B) Averaged

percentages of mica in the sand-size fraction in the four sectors (I–IV) of the study area. (C) Averaged percentages of heavy minerals in the sand-size fraction in

this area. WMND¼western margin of northern delta; EMND¼ eastern margin of northern delta. Details discussed in text.



Among the mineralogical components identified are light

minerals (primarily quartz and lesser amounts of feldspars),

heavy minerals (both opaque and transparent), micas (primar-

ily biotite, with traces of chlorite and muscovite), glauconite,

pyrite, evaporites, lithologic fragments, aggregates, and nu-

merous components of whole and fragmented fauna and plant

material. In addition to the percentages of mica, heavy

minerals, and other mineral components, the proportions of

clay (,2 lm), silt (2 lm to 63 lm), and sand (63 lm to 2000 lm)

fractions were determined for each sample. Percentages of all

Figure 6. (A) Percentages of the clay-size fraction in sediments that formed the northern Nile Delta region during the late Holocene; nearshore coast-parallel belt

is largely sand (after Stanley and Clemente, 2014). (B) Averaged percentages of mica in the sand-size fraction in this area. (C) Averaged percentages of heavy

minerals in the sand-size fraction in the four sectors (I–IV) of the study area. WMND¼western margin of northern delta; EMND¼ eastern margin of northern

delta. Details discussed in text.



these components are listed by Stanley, McRea, and Waldron

(1996, their pp. 205–424). The primary database used in the

present investigation includes the total relative percentages of

mica and of heavy minerals, which, together, in more than half

of the samples examined, account for only a relatively small

proportion (generally ,10%) of the overall sand-size fraction.

Average values were calculated separately for the total heavy

minerals as one group and total micas as a second group.

Averaged data for each of the two stratigraphic sections in all

cores are available from the second author.

Four different values for each core site include separate

average percentages for mica and heavy minerals in both the

lower and upper stratigraphic sections of each core (data

plotted in Figures 5B, 5C, 6B, and 6C). The number of samples

examined to calculate mica and heavy mineral percentages in

the Early to mid-Holocene average of core sections totals 1197

(samples examined in this stratigraphic section of each core

range from 1 to 48). The number of samples in the Upper 2 m

average of Holocene core sections totals 213 samples (samples

examined in this stratigraphic section of each core range from 1

to 8). Values of both mica (Figures 5B and 6B) and heavy

minerals (Figures 5C and 6C) are shown separately on four

maps by means of contour lines plotted at 3% intervals, from

,3% to .12%.

Each of the four mineral contour maps subdivides core sites

in the study area south of the shoreline into four areal sectors,

denoted I to IV from west to east. In sector I, mineralogical data

are averaged from five cores (S80, S82 to S85) along the

western margin of the northern delta (WMND). Sector II

includes data from 21 cores (S60 to S79, S81) from the western

delta sector to the western bank of the Nile’s Rosetta branch.

Sector III comprises data from 34 cores (S1, S2, S4, S28, S29,

S31 to S59) recovered in the delta from the eastern bank of the

Rosetta branch to the western bank of the Nile’s Damietta

branch. Sector IV includes data from 25 cores (S3, S5 to S27,

S30) east of the Damietta branch to the eastern margin of the

northern delta that extends to the NW Sinai (EMND). The four

sector boundaries were selected on the basis of major

geographic and geologic features such as the eastern limit of

carbonate-rich terrains immediately to the west of the delta

(sector I), the two modern Nile branches (Rosetta and

Damietta) in the north-central delta (sectors II and III) proper,

and the Sinai Desert, which serves as the northeastern delta’s

eastern boundary (sector IV). For comparison purposes, data

are also plotted in similar fashion for samples in the two

different Holocene sections of cores S86 and S87 recovered in

the central Nile Delta, south of the northern delta study area

near Kafr el-Zaiyat and Tanta (Figure 1B).

MICA AND HEAVY MINERALS IN TIME AND SPACEThe major observation of note in this study is the relative

reversal, over time, of areas in the northern delta along the

present coastline that have the highest mica content (mostly

biotite, with only traces of muscovite and chlorite grains) and

those with the highest heavy mineral concentrations (mineral

types listed in Frihy and Dewidar, 2003; Frihy and Komar,

1993; Frihy, Lotfy, and Komar, 1995; Naim, El Miligy, and El

Azab, 1994). The measured overall proportions of the two

mineral groups of sand size in the Early to mid-Holocene

sections (older than ~2000 YBP) averaged for 1197 samples

from the 85 core sites in the study area are as follows (Figures

5B, C): mica, 5.9% and heavy minerals, 2.7%. In contrast,

proportions of those two fractions that make up the bulk of

samples in the younger Upper 2 m averaged for 213 samples

from late Holocene sections in the 85 cores across the northern

delta differ considerably (Figures 6B, C): mica, 2.7% and heavy

minerals, 5.2%. Thus, overall, relative percentages of mica

recorded in the northern delta were reduced by more than half

from the early- and mid-Holocene to the early part of the late

Holocene, while percentages of heavy minerals in that same

period increased almost twofold.

To more specifically identify these changes in the major

mineralogical distributions in the study area, average relative

percentage data were compiled separately for the overall

Holocene and late Holocene core sequences in each of the four

regional sectors (I, II, III, IV) of the northern delta. The

following summarizes major differences in both time-related

and geographic distributions of the two mineral groups as

shown in Figures 5B, 5C, 6B, and 6C:

(1) Mica: Proportions in the Early to mid-Holocene sections

are highest in sector III (7.3%), decrease in sector II

(6.1%), and are lower still in sector IV (4.7%). Percent-

ages are considerably lower in the Upper 2 m sections

than those in the Early to mid-Holocene and decrease

from west to east, from sector II (3.8%) to sector IV

(2.1%).

(2) Heavy minerals: Proportions in Early to mid-Holocene

sections decrease from west to east, between sectors II

(4.4%) and IV (1.5%), a diminution of 2.9%. Percentages

of this component are much higher in the Upper 2 m of

core sections than those of the Early to mid-Holocene, yet

they also follow a similar eastward-decreasing trend from

sector II (7.4%) to sector IV (3.3%), a reduction of 4.1%.

Additional observations are made pertaining to the specific

distribution patterns of mica and heavy minerals relative to

specific geographic sectors (I–IV) and changes with time in the

study area:

(1) Mica in older core sections: This lower stratigraphic unit

is characterized by relatively high proportions of mica in

the Early to mid-Holocene sections that are widely

distributed in cores of sectors II to IV (Figure 5B).

Percentages of mica range from .3% to .12% from Abu

Qir Bay west of the Rosetta promontory to east of the

Suez Canal. A long (~225 km), broad arcuate belt

comprising .3% mica extends across most of sector II,

all of sector III, and most of IV; several small, linear

patches rich in mica (.12%) are recorded within this area

and oriented N-S to E-W. The area with average mica

content of .3% extends to and parallels the coast and has

a broad width that ranges from ~10 km south of the Abu

Qir Bay coast in the west, to ~25 km south of the north-

central Burullus lagoon area, and to .40 km in the

northeastern area of the Damietta promontory and

Manzala lagoon.

(2) Mica in younger core sections: Samples in the Upper 2 m

section record a much different distribution pattern, with



.3% mica distributed in two smaller areas, and with a

more modest content (Figure 6B) than in the underlying

older core sections (Figure 5B). Areas comprising moder-

ate to high values of mica (.6%) prevail along the

northern segment of the Rosetta branch south of Abu Qir

Bay, and also, to the east, but in a more localized zone

positioned 10 km or more south of Gamasa and the

Damietta promontory. The two E-W–oriented zones with

mica content .3% are well defined: A somewhat longer

western area ~110 km long and to ~25 km in width

comprises values to .12% south of the Rosetta promon-

tory, and an E-W–oriented area ~70 km in length and

~20 km in width is positioned 5–25 km south of Gamasa

and the Damietta promontory. However, most samples

examined in the younger Upper 2 m sections contain only

low percentages (,3%) of mica along the coast east of the

Rosetta promontory and south of the Burullus embay-

ment and headland; this zone of low mica percentages

extends eastward to the Damietta promontory and south

of the coast in the Gulf of Tineh.

(3) Heavy minerals in older core sections: The distribution

pattern of heavy minerals averaged for the Early to mid-

Holocene time span shows a long and very broad expanse

comprising ,3% of these minerals that extends across

most of sectors III and IV (Figure 5C). The largest area

with heavy mineral proportions ranging from 3% to .6%

is long (~140 km) and narrow (~5–15 km), positioned in

the northwestern coastal region, in sector II and western

half of sector III. This enriched zone is aligned parallel to

the coast between the west of Abu Qir headland and the

coastal sandbar that forms the northern boundary of

Burullus lagoon. Heavy mineral concentrations are

highest (.9%) in a small, localized area near what is

now the northern Rosetta branch.

(4) Heavy minerals in younger core sections: In the Upper 2

m section, the average percentage of heavy minerals has

increased to .3% in a long (.250 km), arcuate, coast-

parallel belt that extends continuously from the Abu Qir

headland in sector II eastward along the delta margin all

the way to the Gulf of Tineh in sector IV (Figure 6C).

Figure 7. Four LANSAT-5 Thematic Mapper images showing relatively recent landward incursion of sand-size fraction from the coast onto the Nile Delta.

These, collected in 1986 and 1988, are reduced in size from their original 1:100,000 scale. (A) Abu Qir Bay (AQB) and sand-covered coast between Abu Qir

headland (AQH) and eroded Rosetta promontory (RP) of the Rosetta branch (RB); IL¼Idku lagoon (East Alexandria image). (B) Linear coastal sandbar east of RP

separating Burullus lagoon (BL) from the Mediterranean; Burullus headland (BH) to upper right (Damanhur image). (C) Large sand dune fields between BH and

Gamasa (G) (Mansura image). (D) Incursion of coastal sand between G and the Damietta branch (DB) and its promontory (DP). Note series of E-directed sand-

spits along this eroded E-W promontory coast and older eroded spits and linear islands preserved in Manzala lagoon (ML) (Damietta image).



Within this belt of variable width (5–25 km), values

increase northward from .3% toward the coast proper to

.9% to .12% between Abu Qir Bay and the Burullus

headland, and also in the Damietta promontory and NW

Manzala lagoon. A value of .30% heavy minerals was

measured in one core (core S17, Figure 1B) in this latter

sector.

(5) Areas of lowest mica and heavy mineral proportions: In

westernmost sector I, samples in the two Holocene

sections show only traces to minor amounts of heavy

minerals (averages of 0.7% to 1.9%), and only traces of

mica (averages of 0.1% to 0.6%). Moreover, samples

collected at core sites S86 and S87 in the central delta

have trace to minimal amounts of mica (,3.0%) and

,6.0% of heavy minerals in both Early to mid-Holocene

and Upper 2 m sections.

DISCUSSIONThe temporal and spatial variations of mica and heavy

minerals described in the previous section are not random but

are consequences of the major natural and human-influenced

factors that have controlled the nature and distributions of the

size fractions of sediment in which the two mineral groups were

deposited in the northern delta during the Holocene. These

factors have contributed to time-regional differences in the

proportions of sand, silt, and clay that constitute most sediment

fractions deposited by the Nile in different sectors of the delta

(Stanley and Clemente, 2014). Other variable factors, but not

random during the time span considered here, are the

following: thickness of sedimentary sections; rates of sediment

compaction and subsidence (Stanley and Corwin, 2013);

decreased sediment volume and fluvial discharge toward the

coast resulting from the increased role of artificial barriers; and

diminished replenishment of sediment in northern delta areas.

All have influenced, at least to some extent, the distribution of

the two mineral groups. When considered in this larger

context, especially the size fractions of sediment with which

they are associated, it is not surprising that the distribution

patterns of mica and heavy minerals recorded in Figures 5 and

6 have varied considerably during the Holocene.

Throughout most of the Holocene period encompassing the

two stratigraphic sections focused on herein, the average

percentages of clay-size (Figure 5A) and silt-size fractions in

most of the study area where the cores were recovered range

from .20% to .60%. Although proportions remained generally

similar in much of the northern delta during the late Holocene,

average percentages of these two fractions diminished consid-

erably (with ,20% combined silt and clay) near the coast. In

contrast, the nearshore zone during this time is characterized

by a well-defined coast-parallel belt with .20% to .80% sand

formed along and just south of the shoreline (Stanley and

Clemente, 2014, their Figures 4B, C). This recently formed

sand-rich zone borders the entire coast, extending from the

Alexandria region in the west to the northeastern corner of the

delta south of the Gulf of Tineh (El-Fishawi, 1985; El-Fishawi

et al., 1976). Its width ranges from 10 km in sectors I to III to

.15 km in the Gamasa region of eastern sector III and the

Damietta promontory in the western part of sector IV (Stanley

and Clemente, 2014, their Figure 4A). The coastal strip is

readily visible on satellite images, where the most extensive

stretch includes the broad belt of sand dunes west of the

Gamasa outlet (Figure 1A, sites 10–12). Other important sand-

rich areas include coastal sectors west and east of the Rosetta

mouth (site 6), the long sandbar that separates Burullus lagoon

from the sea (between sites 6 and 9), areas west and east of the

Damietta promontory (sites 13–15), and also Port Said and

adjacent northern Suez Canal (sites 17 and 18). The arcuate

belt of sand-rich and clay- and silt-poor coast-parallel terres-

trial areas is shown in greater detail in Figure 7.

The long and broad distribution of high mica proportions (to

.12%) in the northern delta’s Early to mid-Holocene sections

correlates well with mapped high percentages of clay (.60%)

that formed deposits south of the present coast (Figures 5A, B).

This pattern of mica, prevalent in these older mud-rich core

sections, is also similar to that of the narrower coast-parallel

belt rich in heavy minerals (.12%) mapped in the Upper 2 m

late Holocene core sections (Figure 6C). It is of note that this

latter enriched heavy mineral zone closely resembles the coast-

parallel distribution pattern recorded by the much higher

percentages of sand (to .80%) and low proportions of silt and

clay (both ,40%; Figures 6A, C) mapped by Stanley and

Clemente (2014, their Figure 4A). Thus, on land near the

present coast, high mica content in fine-grained sediments

prevails in the Early to mid-Holocene section, while high heavy

mineral content is more prevalent in the sand-rich Upper 2 m

late Holocene deposits.

During the two periods considered, these reversed distribu-

tion patterns are interpreted as the result of mechanical

separation of mica from heavy mineral grains by transport

processes. The two mineral groups became partially segregated

from each other and, to some extent, from the quartz and

feldspar that constitute most coarse silt- and sand-sized grains

in the northern delta. This segregation phenomenon occurred

in part due to the Nile’s altered seaward flow as the river

subdivided north of the delta apex and its water was diverted

into separate distributary channels extending to the coast

(Figure 3). The different petrological attributes of these

minerals, including size, density, and shape, contributed to

their mechanical separation as the Nile flowed northward to

the coast, and by the effects of marine processes that prevailed

at distributary Nile branch mouths and beyond in nearshore

sectors (El-Fishawi, 1985; El-Fishawi and Molnar, 1985; Frihy

and Komar, 1993; Frihy, Lotfy, and Komar, 1995; Gheith et al.,

1994).

The shoreline during the Early to mid-Holocene shifted north

of the present coast as shown in Figure 2 (phase II arrows).

Proportions of mica well to the south of the then-positioned

sandy shoreline were much higher (to .12%) at that time than

in the same area during the late Holocene (Figure 5B). The

much lower proportions of mica (,3%) in the younger Upper 2

m section along the north delta margin inland from the present

coast, from east of the Bolbitinic-Rosetta promontory to south

of the Gulf of Tineh (Figure 6B), indicate that the sediment

transport regime and depositional conditions in this area of the

delta plain changed markedly during the past ~2000 years. To

interpret these findings, it is recognized that, during much of

the Holocene to present, proportions of clay released in the



northern delta were considerably higher (to .60%) than those

of clay measured along the present Nile River in Middle and

Upper Egypt (9%), and in the central Nile Delta (11% clay,

according to Morsy, 1981; and ,20% in cores S86 and S87 as

calculated in this study; Figure 6A). The increased proportions

of mica (to .12%; Figure 6C) associated with high percentages

of clay (20% to .40%; Figure 6A) suggest a response to reduced

fluvial flow intensity and transport capacity in sectors north of

the central delta. The delta’s seaward-directed slope diminish-

es substantially from Cairo at its southern apex (elevation to

about 22 m above mean sea level [msl]) to Tanta (elevation of 8

m above msl at ~80 km north of Cairo). The slope continues to

decrease northward, especially where it merges with the near-

horizontal surface of the northern delta plain, which lies at

about 1 m elevation above msl. This latter flat region is~30 km

to ~45 km wide landward of the coast. Before emplacement of

the Aswan High Dam, Nile waters flooded annually in late

summer–early fall and spread across this broad, flat plain’s

surface by channel overbank flow. This led to enhanced

discharge of sediment in that sector with notably higher

proportions of both clay and mica.

Additional information on the causes of distribution differ-

ences of mica in time and space in the study area is provided by

examination of the separately mapped patterns of heavy

minerals. In contrast with mica, these denser minerals (to

3%–6%), especially iron-rich ones, were more prominently

released in the Early to mid-Holocene section and concentrated

primarily in a narrow coastal zone between Alexandria and the

northern Burullus headland (Figure 5C). Higher concentra-

tions (.6%–.12%) at that time are mapped only in two areas of

the Abu Qir Bay region, landward of the former mouths of the

Nile’s Canopic (El Bouseily and Frihy, 1984) and Bolbitinic

branches (Figure 3). It is of note, however, that until the late

Holocene, low proportions (,3%) of heavy minerals occur in

sectors III and IV in most of the northern region, from the

Burullus headland to the delta’s eastern margin (Figure 5C).

During this seaward progradation (phase II) period, the

muddy sand and sandy mud sediment landward of the present

coast was characterized by overall similar average size

fractions of sand (29%), silt (35%), and clay (36%) in the core

recovery area (Stanley and Clemente, 2014, their Figure 3).

This fairly even distribution of the three sediment fractions in

older Holocene sections, however, differs from those forming

the Upper 2 m core sections. In these more recent sediment

units, proportions of sand became coast-parallel, with percent-

ages increasing distinctly northward from ,20% to .80%

towards the present coast (Stanley and Clemente, 2014, their

Figure 4A). Heavy minerals (to .12%) in the coastal zone, and

especially the suite of dominant mineral species that form the

black sand deposits distributed along beaches (El-Hinnawi,

Niazi, and Samy, 1989; Frihy, Lotfy, and Komar, 1995), tend to

be of finer-grained sand size than the bulk of light mineral

grains, such as quartz and feldspar, with which they are

associated. It has been shown that fine-grained beach sands

that consist of large proportions of total heavy minerals tend to

prevail where the coastline sector is subject to greater erosional

intensity and sediment reworking (Frihy and Dewidar, 2003).

While effects of such size sorting are recorded by deposits

displaced by marine processes along the delta coast (Frihy and

Komar, 1993; Frihy and Lotfy, 1994), these phenomena, also

probable along the Nile’s fluvial transport paths between

African source areas and northern delta environments, have

yet to be clearly defined.

High proportions of mica in fine-grained deposits of older core

sections near the coast (Figure 5B) and those of heavy minerals

in sand-rich units in the younger sections near the coast

(Figure 6C) record the close relation among the delta’s

shoreline position, dominant sediment-size fraction released,

and distribution of the two mineral groups. High percentages of

mica in Early to mid-Holocene sections parallel to the present

coast indicate that they were deposited primarily with fine-

grained sediment fractions during phase II and were preserved

in a zone of minimal winnowing well to the south of the former

coastline position at that time (Figure 2). By the end of phase II

and beginning of the late Holocene, much of the delta’s

coastline appears to have been positioned approximately 10

km to 15 km and perhaps locally farther north of the present

shore. This distance estimate is based on two independent sets

of observation: (1) the minimal northern position of sand-rich

deposits on the adjacent inner shelf as mapped by Coleman et

al. (1981, their Figure 4), El-Fishawi et al. (1976, their Figure

4), and Summerhayes et al. (1978, their Figure 6); and (2)

calculation of relative sea-level rise that takes into account

rates of both eustatic rise and lowering of the delta plain

surface. The first item (1) indicates a northern average seaward

position off the Nile shelf delineated by the present approxi-

mate seafloor depth of about 20 m (Figure 2, phase II arrows).

The second item (2) is based on the calculation involving a

modest rate of world sea-level rise (~1.0–1.5 mm/y) during

much of the past~2000 years (Lambeck and Purcell, 2005) plus

the rate of land subsidence in the northern core recovery area of

the delta plain near the coast. The rates of land lowering range

from 3.7 mm/y west of the Rosetta branch, to 7.7 mm/y between

the Rosetta and Damietta branches, and to 8.4 mm/y east of the

Damietta branch (Stanley and Corwin, 2013; ARC in Figure

5A). An average relative sea-level rise rate to 1 cm/y would

have accounted for as much as 20 m of delta plain surface

lowering beneath sea level during the past 2000 years to

present.

A relative sea-level rise of~1 cm/y, and position of the former

shoreline, now subsided to~20 m at a distance of about 10 to 15

km north of the modern coast, would have resulted in average

horizontal rates of landward retreat of the coastline ranging

from approximately 5 m/y to 7.5 m/y from ~2000 YBP at the

end of phase II to the present time (Figure 2, phase IIIa

arrows). Shoreline retreat rates on the order of 2 m/y to 3 m/y

have been estimated in Abu Qir Bay between the offshore

position of now-submerged Greek and Roman centers (Her-

acleion and East Canopus) and the present coast to the south

(Goddio, 2007; Stanley, 2007). These landward incursion rates

approximate those of measured shoreline erosion recorded

along some coastal sectors as recently as the early to mid–

twentieth century, such as at the Burullus headland (cutback

rates of ~5 m/y) prior to recent emplacement of protection

structures at that location (Frihy and Deabes, 2011). It is also

possible for landward retreat to have exceeded these rates at

times when periodic deep-seated readjustments of strata

additionally lowered the delta surface, as was likely in the



sector underlying the Manzala lagoon area in the northeastern

delta (Stanley, 1988, 1990).

CONCLUSIONS AND RAMIFICATIONSThe relationship among mica, heavy minerals, and the

dominant grain-size fractions (sand, silt, or clay) that form

the Holocene deposits in which they occur at and landward of

the coast shows that recorded distributions of the two mineral

groups are able to help identify the Nile Delta’s former coastal

positions. We propose that such mineral/sediment grain-size

associations could potentially also serve as useful indicators to

measure ongoing shoreline changes and perhaps help predict

future displacements.

Of interest in this respect is an examination of sand-rich

nearshore and onshore deposits that have low amounts of mica

(,3%) and a significant heavy mineral content (.3%) that have

shifted landward to south of the delta’s coast during the past

few centuries (Figures 6B, C). Satellite images, such as those of

LANSAT-5 Thematic Mapper (bands 7, 4, 3, 5) acquired in

1985–88 (IWACO-RIGW, 1990, scale 1:100,000), show in detail

the important surficial sand deposits that presently form broad

beaches, lagoon bar barriers, and dunes that have advanced

considerable distances onto the delta plain (Figure 7). Of note

are the present major incursions of sand onto the delta surface.

These have formed the following: broad beaches and dunes

along the eastern third of Abu Qir Bay, reaching inland to

nearly 10 km (Figure 7A); low straight sandbar separating

northern Burullus lagoon from the Mediterranean shoreline (to

5.5 km wide; Figure 7B); high and particularly wide broad sand

dune fields southeast of the Burullus headland and the town of

Gamasa (to 11 km inland; Figure 7C); wide beaches and dune

fields between the Gamasa coast and Damietta promontory (to

5 km wide; Figure 7D); and sand-rich area along the northern

Suez Canal between the Port Said coast and ~10 km to the

south (Figure 1A). Once on land, there are few morphological

relief barriers to retard the sediment’s advance across the low-

lying northern third of the delta plain, which ranges to little

more than 1 m above msl over much of its surface.

Applying the earlier cited averaged coastline retreat rates of

~5 m/y to 7.5 m/y from about 2000 years ago to the present

(phase IIIa) would have produced sand incursion of only 1 km

to 1.5 km over the northern delta, and not the observed 5 km to

11 km cited earlier. Until about an estimated 200 years ago,

displacement of sediment from the foreshore onto back-beach

settings was largely due to wave-current transport and

powerful periodic wave surges. Once ashore, the sand-rich

deposits were displaced further inland by wind onto low-lying

agricultural fields and wetlands (Figure 7). By the early to mid-

1800s, under the rule of Muhammad Ali, Egypt began a

program to emplace large-scale artificial structures such as

barrages capable of altering the Nile’s flow. In the two centuries

following these early modifications, the Nile’s flow pattern has

been substantially altered, resulting in more rapid rates of

landward advance by the sea. For example, a 5 km incursion

landward during the past 200 years would indicate a

southward migration of ~25 m/y. Such an increased landward

advance for extensive distances would likely have involved the

role of several processes in addition to natural coastal erosion

by wave currents and storm surges.

Additional significant factors that have fostered accelerated

entry by the sea onto the coastal margin likely include the

following:

(1) the marked decrease in sediment replenishment in

coastal settings, especially since the closure of the Aswan

High Dam in 1964–65 to establish a constant year-long

flow of the Nile;

(2) emplacement of barrages in the northern delta, which

now severely diminish water and sediment discharge to

the sea via the Rosetta and Damietta branches;

Figure 8. Schematic depicting potential landward shoreline migration southward across the delta plain surface to 1 m elevation above mean sea level (msl) from

present time over the next 100 to 130 years (phase IIIb, shown by arrows), which could result from continued relative sea-level rise. Also shown is the past

landward saline water incursion from the coastal margin inland, with a trend from salt-rich to brackish to freshwater inland (modified after Kashef, 1983).

Salinity in groundwater has continued to increase southward during the past three decades and is now affecting ever-enlarged agricultural and aquacultural

areas of the delta’s northern to central sectors.



(3) the ever-increasing density of delta canal systems that

trap Nile water and sediment displaced north of Cairo

and allow only a much-reduced discharge to reach near-

coastal environments; and

(4) the artificial removal of sand caused by ongoing extensive

quarrying of this sediment from some coastal areas that,

in effect, removes natural high-relief features (some to

~10 m) such as dunes (migrating barchans and other

types), which would otherwise serve as temporary

barriers to retard further inland marine advance (El-

Banna, 2004; Fazaa and Al-Youm Al-Sabi, 2012).

The recent marked reduction of sediment provided to the

coastal-nearshore system can no longer offset the effects of

delta plain subsidence (to 8 mm/y) and of sea-level rise of ~2

mm/y or more, which continue to produce a rate of relative sea-

level rise of ~1 cm/y. These activities, in conjunction with the

other earlier-cited processes that affect the delta’s margin, will

alter and displace the shoreline position further inland on a

near-continuous basis. Effects of erosional cutback, in conjunc-

tion with relative sea-level rise, will become even more

problematic should a eustatic rise in sea level increase from

20 cm to possibly as high as 100 cm by the end of this century,

as has been projected by some climate change experts and

panels. It is not surprising that the Intergovernmental Panel

on Climate Change (IPCC, 2008) has cited the Nile Delta as one

of the world’s most vulnerable coastal sectors.

Based on observations of the two mineral groups presented in

this study, it is expected that percentages of mica will decrease

in younger sediment core sections, while those of heavy

minerals in these same sections are expected to increase south

of the shore as the delta’s coastline retreats landward.

Associated with this evolution is continued, if not increased,

seawater flooding onto the low-lying plain and wetlands, with

saline groundwater migration extending farther south of the

coast as the delta surface subsides relative to sea level. This

increased groundwater salinization will reduce agricultural

productivity and further decrease arable areas of the delta,

which accounts for ~63% of Egypt’s total cultivated land

(Mabrouk et al., 2013). The persisting problems of saltwater

intrusion (Figure 8) coupled with already considerably de-

creased availability of freshwater from the Nile, rainfall, and

groundwater are inevitably affecting the already densely

populated delta towns and countryside (Dawoud, 2004; El-

Asmar, Hereher, and El-Kafrawy, 2012; Kashef, 1983; Mab-

rouk et al., 2013; Sestini, 1992).

In effect, the modern Nile Delta is no longer evolving as a

natural physical, chemical, and biological fluvio-marine system

but, rather, is now viewed as a relict organic-rich depocenter

that is now in its destruction phase, lacking in freshwater,

increasingly polluted, and decreasing area due to a landward-

retreating shoreline (Stanley and Warne, 1998). Without large-

scale, well-planned protection measures, among them emplace-

ment of a series of protective megastructures along much of the

coast, continued relative sea-level rise could submerge the

surface by about 1 m of seawater within the next 100 to 185

years (Stanley and Corwin, 2013; Figure 8). The coastline’s

form during such a landward retreat would likely become less

arcuate than at present. This progressively straighter elongate

shore cut back by marine erosional processes would also

preserve fewer promontories and headlands. Moreover, if

flooded by the sea, only the upper parts of terrains with

present elevations of 1 m above msl will remain visible as small

islands resembling the present ones in Burullus and Manzala

lagoons (Figures 7B, D). Time is of the essence if the most

vulnerable zone comprising the northern third of the delta’s

22,000 km2 area is to be effectively protected.

In summary, we suggest that the distribution patterns of

mica and heavy minerals recovered in surficial sediments and

short core sections can now be mapped on the northern delta

plain to better define altered positions of the coastline and to

measure its potential landward advance during this critical

stage of the depocenter’s evolution (phase IIIb, Figure 8).

Measurements of the two mineral groups could be made

periodically along a series of transects oriented normal to the

shore, and these compilations can then be compared with

records of coastline positions and elevations of the northern

delta’s surface recorded by remote sensing and geographic

information system (GIS) techniques (Becker and Sultan, 2009;

El Nahry, Ibraheim, and El Baroudy, 2008; White and El

Asmar, 1999). Such coordinated multidisciplinary surveys of

the Nile Delta, made in a systematic and regularly scheduled

manner, would serve to accurately measure rates of coastal

subsidence as well as of landward incursions by the sea at

present and in the years ahead.

ACKNOWLEDGMENTSWe thank the National Museum of Natural History,

Smithsonian Institution, for support during preparation of

this study. We also express appreciation to Drs. C. Grifa and

M.R. Senatore and Ms. K.A. Corwin for their thoughtful

reviews of an earlier draft of this article.

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mica and heavy minerals as markers to map nile delta coastline displacements during the holocene

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