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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 .