geophysics in archaeology
TRANSCRIPT
Geophysics in ArchaeologyGeophysics in ArchaeologyA scrapbook A scrapbook
of worldwide dataof worldwide data
Adam O’Neill
The sitesThe sites
GuatemalaGuatemala++
El SalvadorEl Salvador
Pompeii,Pompeii,ItalyItaly
TurpanTurpan, , ChinaChina
JapanJapan
The dreamThe dream
Ground Penetrating RadarGround Penetrating Radar
200 MHz
50 MHz
450 MHz
~10-15 cm / 2 m
<5 cm / < 1 m
+50 cm / +5 m
Resolution / Max. depth
Tx Rx
www.gpr-survey.com
Typicalhyperbolicdiffraction
Electrical methodsElectrical methods
Arealmapping
Depth profiling
Magnetic Magnetic gradiometrygradiometry
Earthsfield
Inducedfield
Vertical magnetic gradient (nT/m)
Sensors
Iron objects(swords, tools)
Remanent magnetism(kilns, bonfires)
ContentsContents
JapanJapan
China
Central America
Pompeii
EmaEma CastleCastle
Kamioka town, northern Gifu prefecture
Built in 1400’s by Lord of Northern Gifu
Destroyed by fire 1582
Chinese and Japanese pottery from 1200’s to 1500’s
Large trapezoidal and triangular moats
GPR surveys in 1994 and 1997
EmaEma CastleCastle
GPR north moatGPR north moat
Line 5
Trapezoidal moat
100 MHz
GPR west moatGPR west moat
Lines 6&7
Triangular moat
100 MHz
Goodman (1994)
GPR modelling
Time migrationTime migration
50 MHz
Migrated
Clear V-shape
Mount Mount ZoubiZoubi
Yoro Town, southern Gifu prefecture
3rd to 6th century
Oldest burial mound tombs of Kofun period
On major east-west military junction
Sites of many battles
Largest mound at hill summit
Magnetic surveyMagnetic survey
Dipolar anomaly!
FM18 vertical fluxgate gradiometer
GPR surveyGPR survey
Hyperbolic anomalyMetallic source Second anomaly
1 m deeper again
200 MHz
Gradiometer: Width at
half-amplitude~source depth
GPR cubeGPR cube
Target 1: Metallic response
Target 2: Underlying anomalyArchaeologists very interested!
E
W
Excavation surveyExcavation surveyExcavated sword fragments
Post excavation survey
Secondary target revealedBurial?
Swords removed
Swords location
450MHz
KomochiKomochi VillageVillage
Komochi Village, Gunma prefecture
Burial mounds of Kofun period, 300-700 AD
Mt. Haruna erupted twice in 6th century
‘Pompeii of Japan’
Burying kofun up to 4 m in ash and pumice
GPR reconnaissanceGPR reconnaissance200 MHz
100 MHzCMP location
Large kofunSmall kofun
Two frequency GPRTwo frequency GPR
200 MHz
100 MHz
Burial chamber?
Surrounding moat?
Burial moundsBurial mounds
Burial chamber reconstruction
Exposed kofun
Typical sizeand shape
GPR modelling
Goodman (1994)
Velocity analysisVelocity analysis
CMPsounding
Velocitymodel
Magneticsusceptibility
Other tumuliOther tumuli
Giant keyhole
Double-mounds/Clusters
RectangularSingle mound
ContentsContents
Japan
ChinaChina
Central America
Pompeii
Site locationsSite locations
TurpanTurpan
Far northern desert
On the ‘Silk-road’, Middle-east to Asian trading route
Early Kingdoms (from 1st century BC)
Later Mongolian rule (13th-14th century AD)
Autonomous ruling from 1954
Excavations in 1930: 120 tombs, 800 artefacts
Excavations in 1994: Pure gold crown
Aerial photographyAerial photography
13 m3 helium blimp
Tombs grouped into family clusters
GPR linesGPR lines
100 MHz antennas
pulseEKKO IV
GPR sectionsGPR sections
100 MHz
Line 9
Line 10
Fence displayFence display
Excavation: Sloping entrance to tomb
Electrical and EMElectrical and EM
EM38 conductivityRM15 twin resistance
3436
Two resistive anomalies
FollowupFollowup GPRGPR
100 MHz
RM15resistance
Buried cavity? (multiples)
Line 34 Line 36
Surficial anomaly?
100 MHz
ContentsContents
Japan
China
Central AmericaCentral America
Pompeii
Central AmericaCentral America
Kaminaljuyu: 500 BC-1000 ADMongoy: earlier (?) Joya de Ceren: 590 AD
Chalchuapa: older (?)
Guatemala CityGuatemala City
Mayan civilisations, buried by volcanic ash
Kaminaljuyu: 500 BC-1000 AD
Mongoy: has older black soil cover, earlier
Pacaya volcano 25 km to south
Active from 3000-700 years BP
Parasitic eruptions in 16th C
Horse bones, Spanish conquest
Guatemala CityGuatemala City
KaminaljuyuArchaeological Park
MongoyMound
KaminaljuyuKaminaljuyu
Survey area: Flat ground between mounds
Electrical and Electrical and magneticsmagneticsRM15 resistance FM18 gradiometer
Coincident resistance and magnetic linear anomaly
Clear edges of large platformor foundation
MongoyMongoy
‘Gran Basamento’mound
‘Gran Muro’Ancient
foundation
Electrical surveyElectrical survey
RM15 resistance
Shallow platform revealed
Targets and excavationsTargets and excavations
Waste pits:Many artefacts
recovered
Topographic contoursSite excavation map
El SalvadorEl Salvador
Joya de Ceren: Agricultural village, 40-50 families
Clay construction
Loma Caldera tuff ring 600 m to north
Erupted during rainy season of ~590 AD
Chalchuapa: Political centre
Stone construction
Pyramid mounds and defensive walls
JoyaJoya de de CerenCeren
Thick clay walls
On raisedfoundations
GPR profilesGPR profiles
100 MHz
50 MHz
Buried structureOn raised platform
InterpretationInterpretation
100 MHz 50 MHz
Thatched roof collapseAsh drapes over clay walls
ChalchuapaChalchuapa
GPR surveyGPR survey
Mound 5
Typical section
Burial cache
100 MHz
50 MHz
GPR surveyGPR surveyMound 2
50 MHz
Construction cutaway
Boundary wallsBoundary walls
100 MHz
50 MHz
Excavation
Slope of rock wall
ContentsContents
Japan
China
Central America
PompeiiPompeii
PompeiiPompeii
Mount Vesuvius eruption August 24, AD79
Rediscovered 1748
Over two-thirds excavated and restored
Some boundary fortifications remain buried
Mount VesuviusMount Vesuvius
Most famous site buried by volcano
Victims seared byhot gas and ash
Ash Ash isopachisopach
Pom
peii
AD79
Modern soil
1000 AD– 1900 ADeruptions
Survey linesSurvey lines
Unexcavated part:Expected buried
boundary walls of the Porta di Capua
MultiMulti--surveyssurveys
Line 30
EM31 deep
200 MHz
100 MHz
Ash flow
North South
Dipping layers
ResistivityVEx5
Electrical Electrical modellingmodelling
Numericalresult
Syntheticmodel
Fielddata
Multiple techniques essential
GPR alone not always enough
100 MHzGPR
Line 150
Fence displayFence display
Diffraction from top of wall aligns across
sections
Summary and acknowledgementsSummary and acknowledgements
Geophysics and archaeology: Essential integration
Prefer multi-methods (GPR-resistivity-magnetics-EM)
Try to use more than one GPR frequency
Get in before excavations start !!!
Yasushi Tanaka, Tanaka Geological Corporation
Dr. Dean Goodman, Geophysical Archaeometry Lab. http://www.gpr-survey.com
OtherOther
ChatanChatan AirbaseAirbase
Okinawa main Island
Post war occupation US airbase
Base designated for closure and repatriation to local families
Archaeological surveys required for:(i) Cultural heritage mapping(ii) Pre-war land ownership boundaries
GPR surveyGPR survey
Pipes and other modern clutter
Anomaly of interest
200 MHzraw
Migrated
ExcavationExcavation
Time slicesTime slices
200 MHzraw
Migrated
Focusedanomaly
Clear pipes
OtherOther
VV--trench modeltrench model
Velocity effectsVelocity effects
Too slow(0.06 m/ns)
Correct(0.095 m/ns)
Too fast(0.11 m/ns)
OtherOther
San San XiaXia
Yangtse River (Chang Jiang)
From 2 million years B.P. to Ming Dynasty (13th-17th C B.C.)
Several thousand years of civilisation
‘Three Gorges Dam’ over 170 m high
Over 1 million people displaced
Over 800 sites will be flooded
Over 10000 tombs expected
Villages still present, difficult surveying
Site locationsSite locations
Steeptopography!
Dam from spaceDam from space
EM and GPREM and GPREM38 conductivity
100 MHz Anomaly!
More GPRMore GPR100 MHz
Real opportunitiy for archaeo-geophysics!
OtherOther
PrePre--exacavationexacavation surveysurveyRM15 resistance
Good accessMany lineaments
Shallow platform revealed
Waste pits
PostPost--exacavationexacavation surveysurvey
Imaging‘Gran Muro’
wall
RM15 resistance
OtherOther
AcknowledgementsAcknowledgements
Yasushi Tanaka, Tanaka Geological Corporation
Prof. Toshi Matsuoka, Kyoto University
Dr. Dean Goodman, Geophysical Archaeometry Lab. http://www.gpr-survey.com
OYO Corporation, Japan (Chatan data)
West Australian Maritime Museum (Abrolhos Island data)
University of Western Australia