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JournaJ of Coastal Research 20 920-9.30 West Palm Beach, Florida Summer 2004

Geoarchaeological Interpretation of the Canopic, Largest of the Relict Nile Delta Distributaries, Egypt Jean-Daniel Stanley!', Andrew G. Warne fS and Gerard Schnepp

tGeoarchaeology-Global Change Program

E-206 NMNH SiTijthsonian Institution Washington, D.C. 20560,

U.S.A.

iAECOCEA International 123 oute de Saint Nizier 38170 Seys,sinet-Pariset,

France

ABSTRACT I

/ a

e Z E 3 STANLEY, .-D., WAKNE, A.G., and SCHNEPP. G., 2004. Geoarchaeological nterpretation of the Canopic, argest of the Relict Nile Delta distributaries, Egypt. Journal of Coastal Research, 20(3), 920-930. West Palm Beach (Florida), ISSN 0749-0208.

The Canopic branch, he argest ehct Nile distributary, once lowed across the NW Nile delta of Egypt to the Medi- terranean. This study focuses on the Canopic's evolution at the delta margin and in Ab u Qir Bay seaward of the coast. Information ro m historic documents, ntegrated with data ro m geographical, geological, and archaeological xplo-

ration in the bay, indicates that the Canopic distributary was active from 4000 B.C. to the end of the 1st millennium A.D. Fluvial discharge persisted hrough pre-Dynastic, Dynastic, Greek, Roman, Byzantine and early Arabic ime. The channel flowed to tw o sites, Herakleion and Eastern Canopus, established by the Greeks as navigational gateways fo r rade n he delta and surrounding egion. Eastern Canopus unctioned until he mid-8th century A.D. At hat time, low n he Canopic had decreased markedly, and Nile water was diverted o he east, hrough he Bolbitic- Rosetta branch. By he end of the irst millennium A.D., Nile water was channeled n he Rosetta and Damietta distributaries, and he Canopic branch eventually converted to a canal and drain system.

The Canopic promontory across which he branch lowed, and the ancient sites located at the promontory coast near Canopic channel mouths, subsided beneath he waters of the bay after he 8th century. Submergence was a response to interaction of eustatic sea-level ise, annual loods, growth-faulting, soft-sediment deformation and other natural processes. As the Canopic promontory subsided, Abu Qir Bay attainted a marked concave-seaward shape and its shoreline shifted southward. This geoarchaeological investigation helps distinguish the long-term impact of natural events rom hat of increased human activity. This distinction is of practical mportance fo r the highly populated and vulnerable delta margin that continues to experience submergence and erosion.

ADDITIONAL INDEX W O R D S : bu Qir Bay, archaeology, avulsion, Canopic promontory, channel migration, Eastern Canopus, Herakleion, navigation, Nile floods, ea-level rise, subsidence, substrate failure, rade centers.

INTRODUCTION

The River Nile is one of the world's best documented fluvial s^i^stems. However, there have onlj' been few investigations of this iver's ower stretch and ts distributaries that once extended o, and seaward, of the Nile delta coast in Egypt. The present study integrates geographical, geological, archaeological, nd historic nformation o define he ong-term evolution of the ower Canopic branch that once lowed across the northwestern Nile delta n Eg3'pt o he Mediterranean Sea. The Canopic, argest of the elict River Nile distributaries, discharged arge volumes of sediment along the delta's coastal margin rom he arly o mid-HoIocene. he ranch e- mained active during the major period of human development in his delta sector, persisting hrough pre-Dynastic, Dynas- tic, Greek, Roman, Byzantine and, probably, o early Arabic time ToussouN, 1934; CHEN et ai, 992).

Much of what was known bout he history of he ower Nile and ts Canopic and other distributary branches n he

03505A received and accepted in revision 12 May 2003. ' Deceased.

delta was ummarized n he arly 0th entury, with he most comprehensive synthesis prepared by Egyptian Prince Omar Toussoun. This cholar e\ewed hanges f he Ca- nopic, ocusing rimarily' n bout lOO years f evolution (600 B.C. o 500 A.D.), and based his observations argely on ocuments f Greek, Roman, nd Arab cholars TOUS- SOUN, 922, 1926). More recent historical reviews (BERNAND, 1970; SAID, 993) have been formulated, at east n part, on Toussoun's sources. Geographic and geologic surveys comple- mented hese tudies nd rovide ew nformation n he origin and early history of the Canopic branch and adjacent

Nile delta egion EL BOUSEILY nd FRIHY, 984; HEN t al., 992; WARNE nd TANLEY, 993; RIHY t al, 994). Nevertheless, mitations f working nly rom istoric r earth science perspectives have precluded summation of the Canopic branch's development through time, especially in the offshore sector.

Constraints have been accurate correlation of natural and human events n his egion and evaluation of the branch's coastal volution long he elta margin, ow n waters of Abu Qir Bay Figure ). New ight has been shed by he un-


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Geoarchaeological Interpretation of Nile Delta Distributary 92 1

Rosetta Promontory

YZ^ Land, > 0

Elevation, n meters, elative to mean sea level

I Oto-5 -5 to-10 ' ~^ -1 0 to-20 20 to -3 0 I Deeper than

-3 0

Figure . eneral physiography f the Abu Qir Ba y area, long tlie northwestern Nile delta, Egypt, rom he Ab u Qi r promontory nd idge o he Rosetta promontory. Th e Canopic branch once lowed to he western bay sectoi' (Figure 2). Shown are he submerged Canopic promontory, the Canopic submarine ridge tliat extends northeastward from he Abu Qi r carbonate lieadland, an d tlio Rosetta promontory.

derwater exploration of two ecent!}' discovered ancient settlements, Herakleion nd Eastern Canopus, presently situ- ated about km north of the coast at water depths of 5 o

m n the western ba}' (GODDIO, 2003). These settlements, ini- tial!)' established b)' he Greeks at he mouth of the Canopic for rade urposes n gypt, rovide ew nsiglit n he branch's oastal evelopment and ignificance. Particularly valuable are data on sediinent substrate and natural events in his egion that can now be examined n ight of archaeological (CoNSTANTY, 2002; GODDIO, 2004), physiographic and geophysical SCHNEPP, 000), nd ubstrate tratigraphie (STANLEY et al., 2001, 2004) information obtained in Abu Qir Bay where he ranch nce lowed. This multi-disciplinarj' approach applied offshore should make t possible o assess more omprehensively he volution f he Canopic luvial system rom he ime of its nitiation until ts demise.

GEOGRA PHIC SETTING

The resent configuration of the orthwestern Nile delta margin s argely he esult of interaction of River Nile sediment input and accumulation along the coast and shelf, and the emoval nd edistribution f his material y marine processes. eaward ccretion nd rogradation of the delta typically prevailed when and where iver accumulation ates exceeded the capacity of marine processes to ework the sediment. n ontrast, ubsequent rosional hases ccurred when oastal rocesses emoved more ediment han was provided y iver ediment nflux STANLKY nd WARNE, 1994). The arcuate Nile delta coastline that has evolved s a

result f an ctive wave-dominated egime, where oastal currents along the northwest delta eroded and displaced eastward fluvial sediment discharged to the coast and shelf (FRI- HY et al, 988; SISTINI, 989).

The Abu Qir Bay shoreline s distinctly concave seaward, unlike the gentle convex coastline of the central and eastern Nile delta (inset. Figure ). The coastline is about 50 km long, from he Abu Qir promontory that forms he west bay boundary o he Rosetta romontory n he east EL ASKAKY nd FRIHY, 986). Abu Qir idge delineates he northern part of the bay; t extends seaward o he NE, rom he modern ip of the Abu Qir promontory o about km nto he Mediter- ranean. The Rosetta promontory, the triangular-shaped mass of unconsolidated fluvial-deltaic sediment, protrudes seaward 14 km o he NNW nto he nner Egyptian helf. Land- ward, o he south, several environments surround the modern bay: beach, backshore sandflat and strand plain, coastal dune, brackish o resh-water wetland lagoon, marsh), km (low ill), rain nd anal, nd gricultural and EL-FAY- OUMY et al., 975; EL

FLSHAWI nd EL ASKARY, 981; FRIHY et al, 988; CHEN et al, 992; WARNE nd STANLEY, 993). The modern bay proper can be subdivided nto wo distinct

regions on the basis of shoreline configuration and bathymetry: the Abu Qir idge-to-Maadia ector n he western bay, nd the onger Maadia-to-Rosetta sector o he east. The seafloor in the western bay sector comprises a large, shallow triangular platform we erm he Canopic romontory Fig'ure ). he promontory s bound o he west by Abu Qir promontory, o the north by Abu Qir idge, and o he east by a well-defined,

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922 Stanley, Warne and Schnepp

[ Undifferenliated Pleistocene deposits

"I Late Pleistocene ! o early Holocene

shallovj marine an d coast sand

Shallow marine an d beach sand

; Calcareous sand I ediment core [ location

B 2000-1000 BC Dynastic,

Late Period

[~~1 lood plain and levee with I . .- 1 limited use lor agriculture

'', \ each and coastal dune Brackish water lagoon

Freshwater wetland

30 km Location of core used for paleogeographic reconstruction

Modern coast

Figure . A) Geological cross-section n he southern Abu Qir Bay egion, showing lateral shifts of the Canopic branch hrough tiine. B,C) Paleogeo- graphic econstructions at about 2000-1000 B.C., and at 500 B.C. a.sed on stratigraphie analysis of radiocarbon-dated sediment cores. The Canopie branch and associated subdelta obes and small distributary channels migrated east o-west, and hen back o east; he Bolbitic and Rosetta) branch began ater, its promontory orming the eastern bay margin (Figxn-e ). Modified -o m CHIN and others (1992).

linear margin that extends from the coastal town of Maadia to Abu Qir ridge. This feature extends northward a maximum of 12 km from he southern bay shore and ies at depths that are, fo r the most part, ess than 0 m.

The Canopic branch once flowed across the Canopic promontory o what was hen ts coastal margin. There, he ancient sites of Herakleion and Eastern Canopus were located near istributary mouths. rior o ts ubmergence, he promontory was once about 0 tm wide along what s no w the delta coast, and its triangular-shaped surface covered an area of ~70 km-. The size, shape and area of the submerged platform-hke feature are similar to those of the younger, sub- aerially-exposed Rosetta promontory ormed by he Bolbitic and, later, Rosetta distributaries of the Nile (Figure 2B, C).

GEOLOGIC BACKGROUND

Subsurface investigations of the Nile delta margin initially focused n he petrology nd ithofacies definition of long, continuous ediment ores FOURTAU, 915; TTIA, 954; SriSTiNi, 1989; STANT.EY et al., 1996). Radiocarbon-core dated sections have been tised to document the changes in position of distributaries that once flowed across the delta plain to the coast nd he elta oast onfiguration. hese ave een markedly altered since the early Holocene (8000-7000 years ago) when he modern delta began o orm STANLEY nd WARNE, 994, 998). Chrono- and ithostratigraphic exami- nation of the substrate serve as he basis o nterpret he evolving paleogeography of the northwestern Nile delta dur-

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Geoarchaeological Interpretation of Nile Delta Distributar 92.3

ing he ong eriod when he Canopic ranch was ctive (CHEN et al, 1992; STANLEY and WARNE, 993).

In addition o ediment ores ecovered n and, bottom sediment grab samples and cores were collected seaward of the present coast in Abu Qir Bay (FRIHY, 992; FRIHY et al, 1994; TANLEY t al, 004). ormer Canopic istributary channel patterns and coastal environments across which they once lowed have been dentified with hese materials. Pet- rologic attributes, such as exture and sand composition of dated samples indicate that the early Canopic channel, or its precursor n his area, ormed about 6000 years go CHEN et al., 992). At hat ime, when sea evel was much ower than at present (to ~10 m), and during much of the following five millennia, the Canopic branch discharged a large volume of sediment n he elta margin. t s his material hat formed the large promontory of f the coast, now submerged in the west-central part of Abu Qir Bay (Figure ).

Lithostratigraphic analyses of Holocene ore sections can be integrated with data rom ecently acquired high-resolution subbottom seismic profiles. Together, these indicate that unconsolidated fluvial sediment and wetland organic-rich de -

posits orming he Canopic promontory ccumulated n subsiding arbonate andstone kurkar) ubstrate f ate Pleistocene age Figure A). Closely-spaced (100 o 000 m) seismic profiles show that the consolidated kurkar'basement' was offset by normal aults nto a horst-and-graben opog- raphy in the late Pleistocene and early Holocene. The under- lying kurkar substrate was irst buried by shallow marine carbonate sediment, and hen by quartz-rich River Nile material during he ollowing 5000 years Figure A). These Holocene unconsolidated delta lobe deposits hicken o 5 m east of the Abu Qir headland (STANLEY et al, 2004).

Channels recorded on seismic profiles, together with fluvial sand ections ecovered n ores, ho w hat he Canopic mouth shifted periodically over a distance of as much as

km along he delta coast during he mid- o ate Holocene (Figure 2A). Lateral migration and river mouth displacement likely occurred n manner similar o hat documented n other major delta systems, .e. ypically induced by avulsion and crevasse-splay processes COLEMAN and WRIGHT, 975; PENLAND t al, 988; TRNQVIST, 994). Shifts of the distributary Canopic mouth were accompanied by displacement of their small, ocalized subdelta obes and associated small channels (Figure 2B, C). As these small coastal margin channels migrated back and forth (at a frequency of 100 years, or less), the older, abandoned subdelta lobes were eroded. Re - worked obe ediment was ransported aterally long he delta margin by coastal currents and storm waves. Eventual disappearance of these delta coastal depocenters beneath the water of the bay resulted from land subsidence (isostatic lowering, ault ffset, ubstrate ailure, ediment compaction) and eustatic sea-level rise.

Sea evel ose at ates of 1-2 mm per year during he period from 60 0 B.C. o 80 0 A.D. determined on the basis of dated ore sections. These ates, while generally similar o those of late Holocene sea-level ise documented elsewhere for this time period (cf. FAIRBANKS, 989; PIRAZOLLI, 1992), would not explain the depths on the bay floor (-5 to 7 m) where he Canopic promontory surface and submerged sites

presently ie . Moreover, he configuration of the northwest Nile delta margin changed considerably during the > 1000- year period when Herakleion and Eastern Canopus were occupied settlements on the coast. The overall arcuate shape of Abu Qir Bay developed as a result of rapid subsidence of the Canopic promontory, decreased Nile discharge at the mouth of the Canopic branch, and increased flow farther to the east, through

the

Bolbitic (later the

Rosetta)

branch

(Figure

2),

THE CANOPIC'S LATE HISTORY ON LAND

The historic ecord provides valuable nformation o help interpret he Canopic branch's evolution at the delta coast, including he ime when his major distributary became relict eature. The Nile delta plain was described by Greek, Roman, Byzantine, and Arab scholars who identified the nu- merous Nile distributaries hat lowed o he coast Figure 3). It has been suggested that perhaps as many as seven fluvial channels and canals were active at on e time. Herodotus and Strabo ndicate hat he mouth of the Canopic branch was ocated within what s no w west-central Abu Qir Bay (Figure A, ). ummarizing vailable ocuments, Tous- SOUN 1922, 926) nd thers ndicate hat he Canopic branch was he argest of the distributary channels at he time of the Greeks as of the 7th o 6th century B.C.) and remained active until the 1st millenium A.D.

It s of note hat before he 6th Century B.C., n he Dy - nastic Late Period, a settlement called Herakleion (N 31 18 ' 775; E 0 7' 70) had been established at the mouth of the Canopic branch (CONSTANTY, 2002). nitially, it was to serve as a gateway fo r ships sailing into and out of the northwestern Nile delta by means of the Canopic branch. Herodotus, in The History (Book 2, 113) states ". he came to Egypt. to what is no w called he Canopic Mouth of the Nile and o the Saltpans. There was, n he shore it s still here), shrine of Heracles." Ships headed to Naukratis, at that time the major Greek ort n gypt COULSON nd EON^VRD, 1979) built along the Canopic waterway about 5 km south of the Mediterranean shore Figure 3A-C). It has been suggested hat Herakleion, he coastal gateway, may have been positioned as much as m above sea level at the time of its construction ToussouN, 934). Meanwhile, rom Roman o Byzantine ime Figures C, 3B-D), he Bolbitic channel o the east (later called he Rosetta) was maintained by artificial excavation. Historians indicate that the Canopic channel was adically transformed n he 5th century A.D. and low had diminished before, or by , he ime of the Arab conquest (ToussouN, 1922, 1926).

It s ikely hat low hrough he Canopic branch at Her- akleion had declined n Roman and Byzantine ime. Docu- ments pertaining to Eastern Canopus N 1 8' 880; E 0 5' 50) suggest that flow in the Canopic channel had shifted westward by 4 km and continued n Byzantine time, until at least the early part of 7th century A.D. BERNAND, 1970). Although flow through the channel had decreased, it is prob- able that the Canopic was still used fo r navigation after that date. New vidence rom rchaeological nderwater xplo- ration ndicates hat Eastern Canopus did not subside beneath the waves until a later date, including findings of valu-

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92 4 Stanley, Warne an d Schnepp

Figui-e . eneralized maps of the Nile delta showing positions of major distributary channels an d canals during the times of (A) Herodotus (-484 to 42 5 BC), (B) Strabo (-63 BC to 24 AD), (C) Ptolomy (-90 to 168 AD), (D) Sirapion (-350 AD), an d (E) El-Idris ( -1099-1154 AD). Channel configurations are shown on n early 20th century base map of the delta and, hence, hese maps do not record change in configuration of the coastal egion. Modified fi'om ToLissouN (1926).

ables uch s he youngest, well-preserved old oins hat date uman ccupation of Eastern Canopus o he mid-8th century A.D. STANLIY et al, 2001, 2004; CONSTANTY, 2002; GoDOio, 2004).

The Canopic, however, did not completely disappear at that time. Documents dating from El-Idris n Arabic time (Figure 3E) o he ost-Renaissance UNDP/UNESCO, 978; AID, 1981; iLlOTTi, 998), ndicate that water emained n he progressively modified Canopic channel. It is envisioned that some low continued, albeit much educed, o he coast until the eginning f the econd millennium A.D.; he Bolbitic- Rosetta ad ecome major istributary ischarging sediment at he eastern margin of Abu Qir Bay during and after the 1st millennium A.D. Figure 4). Maps record the presence of a elict Canopic channel at east through he 18th century

A.D., ncluding hose of Abraham Ortelius, 570; Hondius, 1625 Figure 4A), Benot de Maillet, 1735, Richard Pococke, 1737, ean-Baptiste ourguignon 'Anville, 766. ther maps compiled during his period are shown n Figure 4B- E. More ecently, in the early 19th century, distinct traces of

the elict Canopic are dentified on more detailed maps prepared by ARROWSMITH 1802, 807), DU BOIS-AYM 1813), and AOOTIN 1818). y hen, he ranch ad een rans- formed o an rrigation canal and drain channel system.

Traces of the Canopic branch are presently detected inland from he coast, including the southern margin of Idku lagoon, by aerial photography UNDP/UNESCO, 978) and satellite imagery ABDEL-KADER, 982; WACO, 989). Although n- tensely eworked by farmers, a series of low hills kms) are still preserved n his northwestern delta egion. Interpreted

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Geoai'chaeological Interpretation of Nile Delta Distributary 925

A Hondius "-^-'(1625)

P . Forlani (1566)

Modern Delta ,- ' (dashed line) "-

Rashid (Rosetta)

^ Niebuhr (1761)

C P . Lucas p (1717)

^ ^ < ' ^B,M.

Fort Julien

Figure . VIaps showing the conguration of the northwest Nile delta i'om he mid-16th o he ate 18th century A.D. A) Enlarged portion of a map by Hondius 1625 A.D.) showing the elict Canopic channel extending to (1 ) dku agoon and 2) Mediterranean coastal outlet west of Rosetta. For C-E, the modern shoreline dashed ine) s superimposed or -eference y matching he position of Abu Qir headland and own of Rashid (Rosetta) on both liistoric and modern maps. Because the Abu Qir peninsula was not included in historic map B, scaling and orientation of this map (relative to the modern configuration) is more conjectural. Maps B-E are compUed rom data in UNDP/UNESCO (1978).

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as emnant point bars elated o channel migration, hese features delineate ate Holocene low paths of this distributary in the northwest delta.

TRACING THE CANOPIC OFFSHORE

Investigations seaward of the NW Nile delta coast provide

information

essential

o

complement

his

eview

of the

Ca- nopic. ritish nd gyptian ffshore athymtrie urveys made in Abu Qir Bay during the first half of the 20th century showed the presence of submerged linear features that trend SSE o NNW across he northwestern part of Abu Qir Bay (UNDP/UNESCO, 978). These ecord extension of shifting Canopic branches seaward of the coast. The recent, more de - tailed bathymtrie survey Figure A), made n association with on-going geophysical, geological and archaeological x- ploration n he submerged Canopic promontory surface n Abu Qir Bay (SCHNEPP, 2000; GODDIO, 2004; STANLEY et ai, 2001, 004), sheds new ight on the Canopic's history.

The depth of the Canopic promontory s emarkably uni- form, v/ith about 80 % of the surface ranging from .5 o 6.5

m. Physiographic anomalies include: several shallower (< m), elongate to ~2 km ong) eatures, oriented N-S and o- cated at the eastern promontory margin; and tw o rectangular to irregular-shaped depressions in the central part of the submerged promontory. Also noted are several smaller (diameter m) depressions, including on e adjacent to Herakleion. Most significant with respect to he present study are he distinctly inear, channel-like depressions >1 m elief) and nterchannel perhaps evee) ridges mapped along the promontory's eastern boundary (Fig- ure A). These delineate gentle eastward slope extending from depth of ~7 m at he promontory margin o 11 m and deeper in the central bay. On seismic profiles, these linear eatures re eadily raced 10 km rom he present south-central bay coast, near the own of El-Maadia, o he west-central art of Abu Qir Bay. These eatures are no w confidently nterpreted s elict, artially-filled hannels (STANLEY et al, 004). Sediment acies maps depicting tex- ture and composition of modern nearshore and Abu Qir Bay floor deposits also dentify he position of the ormer ower stretch of the more ecent Canopic channel EL BOUSEILY and FRIHY, 984; EL FATTAH and FRIHY, 988; FRIHY et ai, 1994).

More subtle, ower elief 1 m), discontinuous channel- like features are recorded on he surface of the flat Canopic promontory proper. Tw o of these rend oward he ancient towns of Herakleion and Eastern Canopus (Figure ). These features, nterpreted part of the Canopic's distributary ys- tem, trend from Fort El-Hamra in the south to at least as far northward as the submerged sites Figure 5A). It is surpris- ing that such depressions have been preserved on the central portion of the submerged promontory since this is a relatively high-energy, shallow shelf environment. Moderate o strong bottom currents sweep he western bay erode he seafloor, and thus displace sediments laterally (FRIHY et al., 1994) and smooth he promontory surface. Seismic profiles ho w sediment runcation, while grab and ore samples ecord sediment eworking and depression ill STANLEY et al., 004).

Additional vidence s provided by diver excavation at he tw o sites in Abu Qir Bay: a surficial layer (to 1 m thick) of reworked shelly and quartz-rich marine sand partially covers older, organic and silt-rich deltaic margin sediment (fluvial, wetland, coastal) that forms the submerged promontory substrate.

The subtle, inear SSE-NNW depressions on he promontory surface represent partially to nearly filled Canopic channels that are most likely of older Holocene age than the ones that lowed along he eastern promontory margin. W e sur- mise hat uch eatures, xtending ffshore o ow-submerged ancient sites, would not presently be preserved as distinct eatures n he Abu Qir Bay loor had he Canopic branch dried to rickle and were no longer functioning be - fore he 5th century A.D. as ndicated by ToussouN 1934) and others (R. Said, 001, personal communication).

DISAPPEARANCE OF CANOPIC CHANNEL MOUTHS

The disappearance in Abu Qir Bay of tw o important human

centers

and

coastal

extension

of the

Canopic branch

n

ela- tively recent time is puzzling. As noted by ToussouN (1934, p. 52), t s articularly urprising hat what appears o have been cataclysmic event, one occurring during an m- portant historic period with arge population iving in the region, is not mentioned in any historic document.

Among natural processes hat commonly affect delta mar- gins re world eustatic) ea-level hange nd and subsidence, sostatic depression, sediment failure and compaction of substrate deposits. nteraction of tw o or more such phe- nomena could lead to submergence of subdelta lobes and their distributaries beneath the waves COLEMAN, 982). t is recorded that historic records and archaeological evidence no w indicate that Herakleion and Eastern Canopus, located close-

ly o Canopic ranch mouths n he Canopic promontory, were occupied or a period asting approximately 3 centu- ries, rom he 6th century B.C. o he mid-8th century A.D. Ongoing bathymtrie, geological and geophysical exploration, in conjunction with archaeological excavation by divers, show that each of the tw o sites covers a surface area of nearly on e square kilometer and lies at water depths ranging from about 5 o m. However, eustatic ise n sea evel n he eastern Mediterranean since the 8th century A.D. has been less than 2 m along the Nile delta coast. Thus, subsidence of the substrate y ectonic and/or substrate sediment ailure, ccom- panied by erosion and other processes, must account or non-eustatic component of an additional o m ubmergence since Byzantine ime. The esponse o mportant ver-

tical owering of land plus eustatic sea-level ise during the past 300 years, ogether, would account or arge ates of relative sea-level change. While high to > mm/yr), such rates are by no means unique on the Nile delta coastal margin (STANLEY and WARNE, 998).

Among widely distributed valuables ecovered on he bay floor, at Herakleion and Eastern Canopus, are gold and silver coins, jewelry, and statues, along with human and livestock bones. hese, ssociated with arge amaged tructures, point to sudden destruction of sites hat were still occupied.

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Geoarchaeological Interpretation of Nile Delta Distributary 92 7

Canopui (Nelson)

Island

nopus

A bu Qir Bay

Eastern Canopus

erakleion

D

s| (0

< X

~ Canopic channels " (shifts from Greek to early Arabic time)

1 km

Figure . A) Bathj'metry of the present Ab u Qi r Ba y seafloor and location of ancient sites of Herakleion nd Eastern Canopus. The map is based on closely-spaced N-S nd E-W i-id ines, using high-resolution ingle beam chosounder TRITECH PA500. Color shading details the ubmerged, ow- relief Canopic promontory surface, ncluding N-S nd SE o NW rends. Shown n he promontory are well-defined highs 7 m), including one adjacent to Herakleion. Distinct linear BSE to NN W channels at the eastern boundary of the promontory extend from

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Abandonment of the tw o river mouth locales, located near the Canopic romontory oast, ccurred espectively t bout 1900 and 30 0 years go . The younger date at Eastern Ca - nopus is established by archaeological evidence, including the youngest oins Arabic) and Nilometer ecords or his spe- cific eriod POPPER, 951), n onjunction with isrupted strata n adiocarbon-dated ores. Of note re post-deposi- tional

eatures

n

cores

hat include

soft-sediment

deformation, luidization, and slump structures. Seismic profiles of the substrate located below the two sites at the Canopic subdelta iver mouths show arge sections of disturbed strata, including ffset ayers, ilted eposits, nd mud iapirs (STANLEY et al., 003).

An evaluation of potential triggers of sediment failure must take nto account hat he Nile n ts valley and delta was periodically subject o unusually arge luctuations of river flow as a esponse o mportant climatic luctuations POP- PER, 1951; ADAIMSON et o., 980; HASSAIN, 1981; SAID, 1993). Annual variation of the annual peak Nile flood by as little as 1 m ould mean he difference between amine flood stage too ow ) and widespread destruction of the ower delta and

coast flood stage oo high). For example, at he end of the O ld Kingdom and 1st Intermediate Period (about 2250-1950 B.C.), unusually low annual discharge and flood levels caused famine and political disorder. Such periods of drought and of major loods ong continued o devastate population centers located along major distributary channels in the delta plain (SAID, 993). Using all vailable ata, ncluding combined archaeological nd historical nformation, t can be hown that a documented higher-than-average Nile flood at 741 or 742 A.D. was he major rigger or ailure f the ow-lying substrate on which he Eastern Canopus site and emnant Canopic branch were still ocated. Shortly after he ime of Arab onquest, he promontory was urther submerged by floods nd ertical and isplacement. n ittle more han 1000 years, he coastline egressed o ts present position, about 5 km to the south and 2 km to the west of the ancient site (STANLEY et ai, 2003).

Tectonically-induced events during the past tw o millennia may also have caused istric aulting, iquifaction, and sediment slumping eading o ocal and vertical offset and substrate ailure n Abu Qir Bay. W e do not rule out the possi- bility of some earthquake tremors and tsunamis initiated in the more ectonically-active sectors of the eastern Mediter- ranean GUIDOBONI, 994). well-documented example s the arge earthquake-triggered sunami hat caused exten- sive damage to Alexandria in 365 A.D. Thus, positioned just above ea evel n n nstable, water-saturated ediment substrate, Nile looding, ssociated oft-sediment deformation and, additionally, earthquake and tsunami may have in- fluenced he ntegrity of Herakleion and Eastern Canopus. To date, however, the record of liquefaction and fluidized sediment is localized specifically at the Canopic mouths, and not

widely istributed cross he Abu Qir Bay. his ndicates that the impact of seismic events was as geographically limited as that of Nile flooding.

The effects of human activity such artificial channel mod- ification canalization, deepening, deviation) may also have had some nfluence n periodic ateral shifts of the Canopic subdelta mouths in he delta margin setting. Moreover, em - placement of large, heavy stone structures, such as the tem- ples and massive walls at Herakleion and Eastern Canopus, would have had om e ocal mpact. These were constructed directly on water-saturated, organic-rich marsh and coastal sediments of Canopic subdelta promontories. Consequently, these tructures ontributed o ubstrate ailure and were highly prone to damage (STANI^EY et ai, 2004).

In ime, atural rocesses nd uman ctivities would have rendered Herakleion and Eastern Canopus progressively more vulnerable o annual loods of the River Nile. Most destructive were those events reaching a level of 1 m or more above average high lood stage. High loods nduced sudden breaks (crevasse splays) along the channels and their natural levees that lay only just above sea evel. t is o be expected

that the Greeks, Romans, Byzantines, and perhaps those that followed after he ime of the Arab conquest, aving positioned their sites on the soft, clayey silt of the Canopic mouth substrates, were ncreasingly subject to destructive environ- mentally-related problems. Positioned ittle bove mean sea level, the inhabitants were periodically forced to rebuild and, at times, abandon part of their town especially after a larger than average lood event. This cenai-io would also explain large-scale population shifts from Herakleion to Eastern Ca- nopus, and perhaps o other sites along he coastal margin yet to be discovered in the bay.

CONCLUSIONS

The data rom geographical, geological and archaeological exploration, ntegrated with nformation rom historic documents, indicate hat the Canopic distributary was active for a period lasting at least 5000 years, rom about 4000 B.C. o well into the first millennium A.D. Settlements at Herakleion and Eastern Canopus, once positioned at distributary mouths of the Canopic along the Nile delta coast, were submerged in Abu Qir Bay by the mid-8th century A.D. By then, the western and central bay eceived markedly decreased nput of Canopic fluvial sediment, but remained subject to continued land subsidence and sea-level rise and increased coastal erosion. n ime, smaller Canopic distributary mouths and human-occupied sites north of the present coast disappeared as a esponse o avages of annual loods, growth-faulting, and soft-sediment deformation processes hat induced mportant lowering of the substrate.

By early Arabic time, much of the Canopic channel system had been converted into an artificial canal and drain system.

southern coast northward to the Abu Qir ridge. (B) Dashed lines denote partially-filled channels that once extended from Fort Hamra at the coast, across the promontory, to now-submerged ancient sites. Herakleion (submerged during an d after the st century A.D.) an d E;astern Canopus (submerged in the mid-8th century) are studied by underwater archaeological exploration, in conjunction with geological an d geophysical sui-veys.

Journal of Coastal Research, Vol. 20 , No. , 2004


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WARNE, A.G. nd STANLEY, D.J., 993. Late Quaternary evolution of the northwest Nile delta and adjacent coasts in the Alexandria region, Egypt. Journal of Coastal Research, 9, 26-64.

Journal of Coastal Research, Vol. 20 , No. 3, 2004

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