BeneaththeEuphratesSediments:MagneticTracesoftheMesopotamianMegacityUruk-WarkaBy Jörg W .E . Fassb inder

By3000 BCEUruk-Warkawasoneof the largest megac it iesof Mesopotamia. It wasalso

the set t ing for theoldest sagaof humankind, the famous “Epic of Gilgamesh.” More than

100 yearsof archaeolog ical researchandexcavat ionsby theGermanArchaeolog ical

Inst itute (DAI)have revealed the ruinsof thismetropolis. New techniquesnowpeer

furtherbeneath the surfacewithout excavat ion.

Thec itywas center foramult itudeof technical innovat ions, inc luding irrigat ioncanals,

plastermortar, astronomy, writ ing , literacyandnumeracy. About 40 ,000 residents

inhabitedUrukalreadyby3000 BCE, inanareaof some five squarekilometres. The

diameterof the c ity is4 -5 kilometers, theenc losing wallhasa leng thof some11

kilometers. Meanwhile surface surveys, excavat ionsand textshave confirmed the

presenceof canals, houses, templesandgardensevenoutside the c itywall.

Map o f Mesopotamia showing the main anc ient c i t ies and the ex tent o f the

Pers ian Gu l f ca . 5000 B .C . Uruk marked in red . (Wik iped ia)

Uruk , sa te l l i te v iew v ia Goog le Ear th .

Uruk : Panorama v iew o f the c i ty centre w i th the Z iggurat . Courtesy o f Jörg

W .E . Fassb inder .

Traces o f the anc ient gardens in the nor thern par t o f the c i ty

became v is ib le a f ter heavy ra in in February 2019 . Courtesy o f Jörg W .E .

Fassb inder .

Archaeolog ical research into suchanenormous site cannot be restric ted toexcavat ion

andarchaeolog ical survey. Excavat ionsare t imeconsuming andmust beaimedat the

opt imal targets. A ll kindsof remote sensing techniquesmust thereforebeused to

understand the c ity in its ent irety. Aerialphotographymaybedone in suitableweather

condit ionsduring theyear, along withhigh-resolut ion satellite imageanalysisand

AirborneLaserScanning . But thesemethodsare limitednot onlyby temporaryweather

condit ions; theyprovide informat iononlyabout theuppermost cent imetresof the

subsurface. Deeper featuresand those coveredby sediments remainunseen.

Geophysicsprovidesuswithawide rangeof prospect ing methods that canpeerbeyond

thenear surfaceunderground. Magnet ic , elec tric , and radarprospect ionarehighly

developedgeophysical tools to survey the f irst 1 -3 metersbeneath theg roundwith

suffic ient lyhigh spat ial resolut ion. Unfortunately radarprospect ing at Urukwill fail, since

theEuphrates sedimentsareextremely saltyandcontain suchahighamount of c lay

minerals that theenergyof thewavesareat tenuated in the f irst upper20 cmof the

g round. The f irst testswith resist ivityprospect ing (ERT= EarthResistanceTomography)

in the spring seasonof 2019 revealedpromising resultswith respect tomeasuring the

exact depthof features, although resist ivityvaluesareextremely lowdue to thehigh

salt concentrat ionof the sediments. But theseprospect ing methodsare t imeconsuming

and thusof limiteduse for sucha largearea. Magnetometerprospect ing remains the

most suitablemethod to t racearchaeolog ical structuresup to3 meterbeneath the

g round.

Magnetometry forarchaeolog icalprospect ing using total f ield caesiummagnetometers

wasdevelopedand refinedat theBavarianS tateDepartment of MonumentsandS ites in

a c lose cooperat ionwith theGeophysics Inst ituteof theLudwig-Maximilians-University

Munich since the late1970 ’s. Thecaesiummagnetometerprobes, compared to

commerc ialmodels, provideup to100 t imeshigher resolut ion. These typesof

instruments, adapted to the spec if ic requirementsof archaeolog icalprospect ing , must

be carriedmanuallyapproximately30 cmabove theg round. Ideal g roundcondit ionsare

soft , muddyordusty soils, condit ions that make it impossible touseawheeled system,

whichwill either st ick in the soft mudandsandanddamage thearchaeolog ical features.

Magnetometer prospect ion in ac t ion by modi f ied handheld caes ium

magnetometers (Sc in trex and Geometr ics ) in “Duo-sensor” con f igurat ion .

Courtesy o f Jörg W .E . Fassb inder .

Magnetometerprospect ing inUrukwas init iatedby thearchaeolog ist MargaretevanEss

(direc torof theDAI inBaghdad)andcarriedout by theMunichprospect ing team in

2001-2002 , resumedafter the Iraqwar in2016 , andcont inued in2018 and2019 . The

geophysical surveywas started in the southwesternpart of the c ityand focusedonan

areanorthof theS inkashidPalace. A large canalpasses thisarea to theeast , and it

inc ludes the canal and itsbranches, aharbourandset t lement areaeast of S inkashid

palaceanda set t lement area southwest of thepalace. A second, largeareawas

measuredacross the southernc itywall, bring ing to light construct iondetails, awater

gate, aswell asnearbygardensand f ields. In the south, outside the c ity, a largeburial

g roundandahugebuilding complexof the c itywallweredetected.

ICONOS Sa te l l i te image f rom2005 over la id by magnetometer resu l t s o f the

survey areas 2001-2019 . Courtesy o f Jörg W .E . Fassb inder .

Excavat ion o f co f f ins f rom the bur ia l ground . Courtesy o f Jörg W .E .

Fassb inder .

Themagnetogram imageprovides insight into set t lement areas, gardensand f ields c lose

to the c itywall, aswell thenetworkof canals that obviously servedas themainarteries

of Uruk. Thisnetworkof waterwaysandcanals cross the c ity fromnorth to southand

makes the c ityquartersaccessible, but alsoprovidewater for the irrigat ionof gardens

inside theenc losedc ity. Themaincanalwas traced in theeasternpart of the

magnetogram fora leng thof 400 m. It is10 mwideand, at severalpoints, slight ly

smaller canalsbranchoff to thewest . Left and right of the canal are set t lement areas,

dividedby the smaller canals that led to f ieldsandgardenswest of the set t lement areas.

Canalsof threeor fourdifferent widths, the smallest belong ing to the f ield irrigat ion

systems, canbedist inguished.

Thecentralpart of themagnet ically scannedarea is characterizedby twodifferent main

features. In the south, a large structure, running East –West , seems toaccompany the

canals into the c ity centre. A similar shorter structure somemetres to thewest

obviouslyblockspart of themaincanal. Noneof these structuresarevisibleneither from

theairnor from theg round, which isvery f lat in thispart of the c ity. However, they

seem to controlorguide thewater f lowand the canals. Herea selec t iveexcavat ion

coulddetermine thedateand thenatureof these structures.

In the south, the c itywall anda small canal crossing the c itywall canbe seen. Here, the

courseof the c itywall and, at regular intervals, it sbast ionsknown fromprevious

excavat ionsanddocumentat ionelsewhere in the c ity, are c learlyvisible. Thehigh

intensityof the signaloverpartsof thewallon its innerandouter faces seems to

indicate thepresenceof f iredbricks, adetail that wasnot knownbefore. Recent

excavat ionsbrought to light that thesebrickswere composedof anc ient , burnt pottery.

It is alsoapparent that the fort if icat ioncomplexwas constructed suing more separate

walls thanwerepreviouslyknown, and that the canal c irc ling the c ity ran just outside it .

Theent irewall complexwasnearly40 mwide. Thewall it self , with its innerandouter

shellsof bricks, is ca. 9 m thick, anobservat ion that corresponds to theexcavat ion

f indings.

Magnetogramdeta i l o f the c i ty wa l l ( le f t ) and f rom the f loodgate in the

south o f the c i ty ( r ight ) . Cour tesy o f Jörg W .E . Fassb inder .

Excavat ion t rench a t the c i ty wa l l tha t revea led that mud br icks are

composed by anc ient pot tery ins tead o f burned br ick as prev ious ly

assumed and in terpreted f rom our magnetometer measurements . Courtesy

o f Jörg W .E . Fassb inder .

Excavat ion t rench showing the Uruk C i ty wa l l . Courtesy o f Jörg W .E .

Fassb inder .

Furtherdetails about Uruk’s structureareprovidedby themagnetogramof the

southwest gate, which isnearly15 mwideandcanbe interpretedasa f loodgate, where

the inner c ity’s largewest andcentral canals f lowedout through thewall. On the

outside, thegatewas f lankedby towersandwasprobably streng thenedwith f ired

bricks.

Downstreamof the f loodgate, a small side canalbranchesoff to the southeast ,

expanding roughlymidway in front of a largebuilding of f iredbricks intoa smallharbour-

like structure. A prec ise inspect ionof thebuilding revealsa slight shift in theorientat ion

of thewalls, indicat ing twobuilding phases, whilea c loserviewon theharbour seems to

revealvague tracesof buried ships.

Le f t , magnetogramdeta i l o f a huge bu i ld ing complex and an ad jacent

harbor in the south o f the c i ty ; r ight , de ta i l o f the main cana l and ana lys is

o f the shape and depth o f the cana l by ERT-measurement ( red) .

Courtesy o f Jörg W .E . Fassb inder .

Supplementary “EarthResistanceTomography” (ERT)profilesallow toverifyand to

validate thedepthof archaeolog ical features suchas theextensionand thedepthof the

c itywallor the shapeanddepthof theanc ient canals. Detailedanalysisof the

magnetograms, supplementarymeasurementswith resist ivityprospect ionsor seismic

methodscombinedwith satellite remote sensing , UAV surveys, topographical

informat ionand the integrat ionof archaeolog icaldata fromselec tedand targeted

excavat ions, will allow for c loser insights into thedevelopment , the structureand the

funct ionsof the c ity, evenwithout largeandcost lyexcavat ion. Themagnetometer

surveyhopefullywillbe cont inuedandwilloffera comprehensivepic tureof the structure

of Uruk through t ime.

J ö rg W. E. Fas s b inde r is a f ac ult y membe r and le c t ure r at t he G e ophy s ic s

De partment o f Eart h and Env iro nment al S c ie nc e s , Ludwig -Max imilians -

Univ e rs it y , Munic h, G e rmany .

For further reading :

Andrae, W. (1935)Die deuts chenAusgrabungen inWarka (Uruk). Deutsche

Forschungsgemeinschaft .

Fassbinder, J .W.E. (2017)Magnetometry forArchaeology, Encyc lopediao f

Geoarchaeology . Encyc lopediao f EarthS c iences S erie s , 499-514 (doi:10 .1007/978-1-

4020-4409-0_ 169).

Fassbinder, J .W.E. , H. Becker, andM. vonEss (2005)Prospect ionsmagnét iquesàUruk

(Warka). La c ité‚ du roiGilgamesh (Irak), Dos s iers A rchéologie 308 :20-25 .