Excavation Techniques Excavation Techniques and Analysisand Analysis

Recovering Fossil FormsRecovering Fossil Forms

Fundamentals of ArchaeologyFundamentals of Archaeology

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

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

Fossils:Fossils: Remains of life form from the pastRemains of life form from the past Petrification: replacement of bone with mineral or Petrification: replacement of bone with mineral or

stonestone

How are Items Preserved?How are Items Preserved?

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

Others may be preserved byOthers may be preserved by Arid climates (Peruvian coast)Arid climates (Peruvian coast) Water: Planks in Lakes in FranceWater: Planks in Lakes in France Peat moss: the “Bog People”Peat moss: the “Bog People”

More Examples of PreservationMore Examples of Preservation

Waterlogged Sites: Bog People, DenmarkWaterlogged Sites: Bog People, Denmark Arid Sites: Puruchucho-Huaqerones Arid Sites: Puruchucho-Huaqerones

Mummies, PeruMummies, Peru Cold Sites: The Iceman, Italian AlpsCold Sites: The Iceman, 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

Surveys: Hadar, EthiopiaSurveys: Hadar, Ethiopia

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

Survey: Mapping Part 2: Survey: Mapping Part 2: Horizontal MeasurementHorizontal Measurement

Select and draw west-east (X-axis) and north-Select and draw west-east (X-axis) and north-south (Y-axis) baselines from south (Y-axis) baselines from primary site primary site datum datum

Mark off intervals at meters and centimeters Mark off intervals at meters and centimeters from baselinesfrom baselines

Label the intervals along axes of the grid by Label the intervals along axes of the grid by letters, numbers, or bothletters, numbers, or both

Adapt procedure according to topographical or Adapt procedure according to topographical or archaeological featuresarchaeological features

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.

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 remains and artifactsHuman remains and artifacts

Test pits provide sample of overall siteTest pits provide sample of overall site Test Trenches reveal stratigraphyTest Trenches reveal stratigraphy

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

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 association Artifacts found at different strata are not in association

with one anotherwith one another

Law of Superposition: Geological layers are Law of Superposition: Geological layers are stratified one upon anotherstratified one 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

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 occurred Assumption: artifacts found at same layer occurred at same time periodat 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

Theodolite: records the position of an artifact Theodolite: records the position of an artifact using a laser bouncing off a prism of known using a laser bouncing off a prism of known heightheight

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

Analysis: Aims and ObjectivesAnalysis: Aims and Objectives

DatingDating Artifact: classificationArtifact: classification Bone analysisBone analysis PaleobotanyPaleobotany Palynology (pollen analysis)Palynology (pollen analysis) PaleozoologyPaleozoology StructuresStructures Other featuresOther features

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 Associations: Chronometric Associations: Relative and Absolute Dating Relative and Absolute Dating

Combined?Combined? 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 Absolute Dating: Isotopic TechniquesTechniques

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.