geophysics in archaeology

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