excavation techniques
DESCRIPTION
Describes procedures in excavation from surveys to the dig to dating of hominin remains and artifacts.TRANSCRIPT
Excavation Techniques Excavation Techniques and Analysisand Analysis
Applications to Applications to
PaleoanthropologyPaleoanthropology
About Excavation and AnalysisAbout Excavation and Analysis
Authors’ definition:Authors’ definition: Study of past cultures analyzing material Study of past cultures analyzing material
remains of human behaviorremains of human behavior Study entailsStudy entails Time: Date of the site and its contentsTime: Date of the site and its contents Space: Location of the site and its contentsSpace: Location of the site and its contents Material remains: siting, retrieval, analysis Material remains: siting, retrieval, analysis
Fundamentals of Excavation and Fundamentals of Excavation and AnalysisAnalysis
Site discovery and selectionSite discovery and selection Excavation of artifacts, ecofacts, and featuresExcavation of artifacts, ecofacts, and features Analysis for dates, attributes, and environmentAnalysis for dates, attributes, and environment
An Example: Flow Chart for Combe An Example: Flow Chart for Combe Capelle Capelle (A Neanderthal Site) (A Neanderthal Site)
Research DesignResearch Design DiscoveryDiscovery PreparationPreparation Data Collection (The Dig)Data Collection (The Dig) AnalysisAnalysis Interpretation/SynthesisInterpretation/Synthesis
Some DefinitionsSome Definitions
Ecofacts: remains of plants, animals, sediments, Ecofacts: remains of plants, animals, sediments, or other materials not modified by human or other materials not modified by human activity activity
Features: immovable structures, pits, posts, Features: immovable structures, pits, posts, burial sitesburial sites
Artifacts: all portable objects altered by human Artifacts: all portable objects altered by human activityactivity
Sites: Landscape where human activity took Sites: Landscape where human activity took place, as indicated by the aboveplace, as indicated by the above
How are Sites Formed?How are Sites Formed?
Taphonomy: Study of how lifeforms or Taphonomy: Study of how lifeforms or artifacts wound up at a particular locationartifacts wound up at a particular location
Primary refuse: items left at site of usePrimary refuse: items left at site of use Secondary refuse: Items moved elsewhereSecondary refuse: Items moved elsewhere
How are Items Preserved? How are Items Preserved? Material Material
Some materials resist deterioration:Some materials resist deterioration: Bone: Skulls and teethBone: Skulls and teeth Stone or Metal (tools, ornaments)Stone or Metal (tools, ornaments) Seeds, with protective coversSeeds, with protective covers
How Are Objects Preserved? How Are Objects Preserved? EnvironmentEnvironment
Arid climates (Peruvian coast)Arid climates (Peruvian coast) Water: Planks at Ozette, WA or FranceWater: Planks at Ozette, WA or France Peat moss: the “Bog People” in ScandinaviaPeat moss: the “Bog People” in Scandinavia Ice: Ötzi the “Iceman” in Austrian/Italian AlpsIce: Ötzi the “Iceman” in Austrian/Italian Alps Volcanic Ash, Cerén, El SalvadorVolcanic Ash, Cerén, El Salvador
Site DiscoverySite Discovery
Lucky findsLucky finds Consulting available sources: studies, records, Consulting available sources: studies, records,
even older informantseven older informants Maps and aerial photographsMaps and aerial photographs Geographical Information Systems/Remote Geographical Information Systems/Remote
SensingSensing
Site SelectionSite Selection
Learning everything possible about each siteLearning everything possible about each site Selecting as large and representative a site as Selecting as large and representative a site as
possiblepossible Preliminary work: surface finds, features, Preliminary work: surface finds, features,
perhaps test pits or trenchesperhaps test pits or trenches Problem-Oriented Research and Deliberate Problem-Oriented Research and Deliberate
SurveysSurveys
Survey: Mapping, Part 1: Survey: Mapping, Part 1: General General
First principle: Digging is destructive--record First principle: Digging is destructive--record everything!everything!
MappingMapping Latitude, longitude, and elevationLatitude, longitude, and elevation Benchmarks or featuresBenchmarks or features MeasurementsMeasurements Horizontal Horizontal VerticalVertical
Surveying: Mapping Part 2: Surveying: Mapping Part 2: Horizontal MeasurementHorizontal Measurement
Select and draw west-east (X-axis) Select and draw west-east (X-axis) and north-south (Y-axis) baselines and north-south (Y-axis) baselines from from primary site datum primary site datum
Mark off intervals at meters and Mark off intervals at meters and centimeters from baselinescentimeters from baselines
Label the intervals along axes of Label the intervals along axes of the grid by letters, numbers, or boththe grid by letters, numbers, or both
Adapt procedure according to Adapt procedure according to topographical or archaeological topographical or archaeological featuresfeatures
Laying Out an Alternative GridLaying Out an Alternative Grid
Survey: Mapping Part 3: Survey: Mapping Part 3: Vertical MeasurementsVertical Measurements
Surveying using transit or alidade and Surveying using transit or alidade and measuring rodmeasuring rod
Vertical base: benchmark or permanent feature Vertical base: benchmark or permanent feature of known elevationof known elevation
Convert measures to meters above sea level.Convert measures to meters above sea level.
Example: Work In ProgressExample: Work In Progress
Virtual Dig: Virtual Dig: Mapping in Combe-Mapping in Combe-CapelleCapelle
Retraced excavation by Henri-Marc AmiRetraced excavation by Henri-Marc Ami Excavated sample squares of the site Excavated sample squares of the site Squares distinguished bySquares distinguished by Letter (X axis)Letter (X axis) Numbers (Y axis)Numbers (Y axis) Vertical measurements by 4 strata.Vertical measurements by 4 strata.
Survey: Test pits and trenchesSurvey: Test pits and trenches
Test pits provide sample of site stratigraphyTest pits provide sample of site stratigraphy Stratigraphy: Stratigraphy: profile of two or more layers ofprofile of two or more layers of Natural sedimentNatural sediment Human depositsHuman deposits Test pits provide sample of overall siteTest pits provide sample of overall site Several pits suggest which part should be Several pits suggest which part should be
excavated most extensivelyexcavated most extensively
Survey: Test PitsSurvey: Test Pits
Advantages: Provide preliminary information Advantages: Provide preliminary information on siteon site
DisadvantagesDisadvantages Need more pits to round out informationNeed more pits to round out information May not yield full stratigraphyMay not yield full stratigraphy
Survey: TrenchesSurvey: Trenches
UsesUses Provide full stratigraphyProvide full stratigraphy Provide sample of artifacts to establish chronologyProvide sample of artifacts to establish chronology Locate featuresLocate features Find site boundariesFind site boundaries TypesTypes Slit trenchesSlit trenches Step trenchesStep trenches Backhoe trenchesBackhoe trenches Wall trenchesWall trenches
Survey: Trenches—Advantages and Survey: Trenches—Advantages and DrawbacksDrawbacks
Advantages: Advantages: Good samples of artifactsGood samples of artifacts Find buried featuresFind buried features Good time depthGood time depth DrawbacksDrawbacks Destructive, especially with backhoeDestructive, especially with backhoe Can destroy potential activity areas before knowing Can destroy potential activity areas before knowing
what’s therewhat’s there Danger of collapseDanger of collapse
Deciding Where to ExcavateDeciding Where to Excavate
Sampling depends on research questionsSampling depends on research questions Judgmental Sampling: based on prior Judgmental Sampling: based on prior
knowledge of site; used at Combe-Capelleknowledge of site; used at Combe-Capelle Probabilistic SamplingProbabilistic Sampling Random samplingRandom sampling Stratified sampling: based on prior knowledgeStratified sampling: based on prior knowledge Known trash deposits or architectural featuresKnown trash deposits or architectural features Ensure everything significant is includedEnsure everything significant is included
Tools for ExcavationTools for Excavation
Dental picks or paint brushesDental picks or paint brushes Ice picksIce picks Tweezers (fragile objects)Tweezers (fragile objects) Trowels (pointed and square)Trowels (pointed and square) Shovels (pointed and square-nosed)Shovels (pointed and square-nosed) Heavy equipment (backhoes)Heavy equipment (backhoes) Buckets and ScreensBuckets and Screens
Tools Used for Rough ExcavationTools Used for Rough Excavation
Shovel, Round Nose Club HammerShovel, Round Nose Club Hammer Pick Chisel, FlatPick Chisel, Flat Pry Bar Scraper, Long HandlePry Bar Scraper, Long Handle Sledge HammerSledge Hammer
Tools Used for Fine ExcavationTools Used for Fine Excavation
Top row:Top row: plastic paint trowel, rubber air puffer, large brushes, plastic paint trowel, rubber air puffer, large brushes, small brush, wooden/plastic sculpting tools/small paint small brush, wooden/plastic sculpting tools/small paint trowel), plastic spoon trowel), plastic spoon Bottom row:Bottom row: note pad, folding ruler (in cm.), Marshalltown note pad, folding ruler (in cm.), Marshalltown trowel (45-5), 8"mill bastard file, plastic spoon, plastic trowel, trowel (45-5), 8"mill bastard file, plastic spoon, plastic trowel, tape measure (3-4 m. is sufficient) tape measure (3-4 m. is sufficient)
Vertical Excavation: Some “Laws”Vertical Excavation: Some “Laws”
Law of Association:Law of Association: Artifacts found at the same stratum (layer) are in Artifacts found at the same stratum (layer) are in
association with one anotherassociation with one another Artifacts found at different strata are not in Artifacts found at different strata are not in
association with one anotherassociation with one another Law of Superposition: Geological layers are stratified Law of Superposition: Geological layers are stratified
one upon anotherone upon another Lower strata are older than higher onesLower strata are older than higher ones Uniformitarianism: Geological processes similar Uniformitarianism: Geological processes similar
throughout timethroughout time
The “Laws” IllustratedThe “Laws” Illustrated
a) Law of Association: Skeleton, dagger, and burial pit are at a) Law of Association: Skeleton, dagger, and burial pit are at the same levelthe same level
b) Law of Superposition: pot is at the higher stratum andb) Law of Superposition: pot is at the higher stratum and stone axe is at the lower stratumstone axe is at the lower stratum
Vertical Excavation: Vertical Excavation: StratigraphyStratigraphy
Layer deposited in chronological order: lowest Layer deposited in chronological order: lowest layer is oldest and so on.layer is oldest and so on.
Disturbances can change stratigraphyDisturbances can change stratigraphy Erosion from hillside: oldest is top layerErosion from hillside: oldest is top layer Structure foundation disturbs layersStructure foundation disturbs layers Burrowing animals may move objectsBurrowing animals may move objects Then there are golddiggers and pothuntersThen there are golddiggers and pothunters
Vertical Excavation: Procedure: Vertical Excavation: Procedure:
Each artifact is recorded and removedEach artifact is recorded and removed Photographed, sketched, or describedPhotographed, sketched, or described Vertical and horizontal positionVertical and horizontal position Soils analyzed for chemistry, pollen, etcSoils analyzed for chemistry, pollen, etc Associations between artifacts are recordedAssociations between artifacts are recorded Assumption: artifacts found at same layer Assumption: artifacts found at same layer
occurred at same time periodoccurred at same time period
Vertical Excavation: ProveniencingVertical Excavation: Proveniencing
Definition: recording artifacts in three-Definition: recording artifacts in three-dimensional spacedimensional space
Transit and stadia rod: record is set from a Transit and stadia rod: record is set from a secondary datum pointsecondary datum point
Theolodite: Records the position of a artifact Theolodite: Records the position of a artifact Using both vertical and horizontal coordinatesUsing both vertical and horizontal coordinates
What is a Theolodite?What is a Theolodite?
Left: Front View Right: Back ViewLeft: Front View Right: Back View Front Lens Viewing Lens and FocusFront Lens Viewing Lens and Focus Gun Sights Adjustment knobs (v and h)Gun Sights Adjustment knobs (v and h)
Laser TheoloditeLaser Theolodite
Adds an electronic distance meter (EDM)Adds an electronic distance meter (EDM) And a laser device to the theoloditeAnd a laser device to the theolodite It records the position of an artifactIt records the position of an artifact Using a laser bouncing off a prism of known heightUsing a laser bouncing off a prism of known height Results can be written down or linked to a portable Results can be written down or linked to a portable
computercomputer Printer can produce tags that are detachedPrinter can produce tags that are detached And put with the artifact to be photographed before And put with the artifact to be photographed before
removalremoval
Horizontal Excavation: Horizontal Excavation: ProcedureProcedure
As each layer or stratum is excavated, it is As each layer or stratum is excavated, it is removedremoved
Same procedure of excavation is repeated for Same procedure of excavation is repeated for next layernext layer
One or two layers: prefer horizontal excavation One or two layers: prefer horizontal excavation to get lay of the siteto get lay of the site
Different samples are taken for different layers: Different samples are taken for different layers: soil, pollen, charcoal, bonesoil, pollen, charcoal, bone
Some layers may be left for controlSome layers may be left for control
Overview of DatingOverview of Dating
UnifomitarianismUnifomitarianism Relative DatingRelative Dating
StratigraphyStratigraphy AssociationAssociation
Absolute DatingAbsolute Dating CalendricalCalendrical Natural FeaturesNatural Features IsotopicIsotopic
Dating: UniformitarianismDating: Uniformitarianism
Uniformitarianism vs. CatastrophismUniformitarianism vs. Catastrophism Uniformitarianism: All geological processes--Uniformitarianism: All geological processes--
erosion, weathering--observable today have erosion, weathering--observable today have always been present and at the same ratealways been present and at the same rate
Uniformitarianism is the basis of dating.Uniformitarianism is the basis of dating. Catastrophism: Changes have been sudden and Catastrophism: Changes have been sudden and
have occurred at different rates in the past have occurred at different rates in the past from those of the present.from those of the present.
Relative DatingRelative Dating
Stratigraphy: Stratigraphy: Establishment of sequences by Establishment of sequences by soil stratasoil strata Exceptions: soil disturbance, erosion.Exceptions: soil disturbance, erosion.
Law of Association: Dating of finds within a Law of Association: Dating of finds within a stratumstratum
Chronometric AssociationsChronometric Associations
Basic principle:Basic principle: Materials associated with Materials associated with other materials of known age are the same age other materials of known age are the same age rangerange Bottle styles and clay pipes .Bottle styles and clay pipes . Gravestones in Stoneham, MA (Deetz)Gravestones in Stoneham, MA (Deetz)
Absolute Dating: CalendricalAbsolute Dating: Calendrical
Entails use of traditional calendarsEntails use of traditional calendars MayanMayan
Long Count:Long Count: Beginning date fixed at 3113 BC Beginning date fixed at 3113 BC Calendar Rounds: Calendar Rounds: 260- and 365-day calendars260- and 365-day calendars
Egyptians: Egyptians: 332 BC Conquest by Alexander the Great332 BC Conquest by Alexander the Great Traced back through recorded dynastiesTraced back through recorded dynasties Astronomical events checked by present data Astronomical events checked by present data
Others: Others: Chinese, Romans, GreeksChinese, Romans, Greeks
Absolute Dating: Natural Absolute Dating: Natural FeaturesFeatures
Dendrochronology: Dendrochronology: Tree ring datingTree ring dating Tree rings vary from year to yearTree rings vary from year to year Local stumps or timber compared with master Local stumps or timber compared with master
sequence (e.g., Univ. of Arizona)sequence (e.g., Univ. of Arizona) Varve analysis: Varve analysis: Clay deposits in lakes from Clay deposits in lakes from
melting ice.melting ice. Patterns also differ yearlyPatterns also differ yearly Likewise compared with master chart.Likewise compared with master chart.
Absolute Dating: Isotopic or Absolute Dating: Isotopic or Radiometric TechniquesRadiometric Techniques
Common PrinciplesCommon Principles Isotopes: Isotopes: Radioactive variants of elements (e.g. Radioactive variants of elements (e.g.
carbon, potassium)carbon, potassium) Isotopes decay from radioactive to nonradioactive Isotopes decay from radioactive to nonradioactive
element element They do so at a constant rateThey do so at a constant rate
Half Life: Half Life: The period in which radioactivity The period in which radioactivity rate reaches half the original rate.rate reaches half the original rate.
Isotopic Techniques: Radiocarbon Isotopic Techniques: Radiocarbon DatingDating
Carbon Carbon is found in all lifeformsis found in all lifeforms Carbon 12Carbon 12 is the stable element is the stable element All living things accumulate All living things accumulate Carbon 14Carbon 14 At death, carbon 14 decays at a constant rate to At death, carbon 14 decays at a constant rate to
Carbon 12Carbon 12 It reaches half the rate of original radioactivity in It reaches half the rate of original radioactivity in
5730 years5730 years At 11460 years, radioactivity is half the second At 11460 years, radioactivity is half the second
rate--and so onrate--and so on
Isotopic Techniques: Accelerator Isotopic Techniques: Accelerator Mass SpectrometryMass Spectrometry
In dating, a sample is cleaned then burned to In dating, a sample is cleaned then burned to produce gasproduce gas
Proportion of C14 to C12 is then counted Proportion of C14 to C12 is then counted using Geiger counterusing Geiger counter
Several grams are required for the countSeveral grams are required for the count Accelerated Mass Spectrometer: Accelerated Mass Spectrometer: counts counts
individual moleculesindividual molecules Advantage: High accuracy, less materialAdvantage: High accuracy, less material
Isotopic Techniques: Isotopic Techniques: Radiopotassium DatingRadiopotassium Dating
Half life: Half life: 1.3 billion years1.3 billion years Potassium is found in granite, basalt, clayPotassium is found in granite, basalt, clay Potassium 40 decays to a gas, Argon 40Potassium 40 decays to a gas, Argon 40 Argon 40 accumulate when a rock is formedArgon 40 accumulate when a rock is formed Disadvantage: materials less than 500,000 Disadvantage: materials less than 500,000
years old cannot be datedyears old cannot be dated
Other Absolute Dating TechniquesOther Absolute Dating Techniques
Electronic Spin Resonance:Electronic Spin Resonance: Accumulation of unpaired electrons in crystals in tooth Accumulation of unpaired electrons in crystals in tooth
enamel and other items with calcium (inaccurate in enamel and other items with calcium (inaccurate in bone)bone)
Geomagnetism: Geomagnetism: Alignment of particles on magnetic rock; this is Alignment of particles on magnetic rock; this is
approximate and there are few labsapproximate and there are few labs Obsidian Hydration:Obsidian Hydration:
Reaction with water; measured by thickness of Reaction with water; measured by thickness of accretion.accretion.
Conclusion: DatingConclusion: Dating
All techniques are problematicAll techniques are problematic Appropriate labs may be rareAppropriate labs may be rare Analyzable material must be present: no volcanic Analyzable material must be present: no volcanic
rock, no radiopotassium datesrock, no radiopotassium dates Inherent problems: radiocarbon dating may be off Inherent problems: radiocarbon dating may be off
by centuriesby centuries Best strategy: use several techniquesBest strategy: use several techniques
e.g. dendrochronology with radiocarbon.e.g. dendrochronology with radiocarbon.
ConclusionConclusion
All excavation involves destructionAll excavation involves destruction Therefore, sites have to beTherefore, sites have to be Excavated carefully, often with trowelsExcavated carefully, often with trowels Recorded for location and elevationRecorded for location and elevation Artifacts catalogued before removalArtifacts catalogued before removal Features have to be mappedFeatures have to be mapped Ideal: Sites could be reconstructed Ideal: Sites could be reconstructed Based on recording of dataBased on recording of data