3.2 Dating methods in archaeology

Dating methods in archaeology are crucial for understanding the past. Relative dating establishes chronological sequences, while absolute dating provides specific dates. Techniques like stratigraphy, radiocarbon dating, and dendrochronology help archaeologists piece together timelines.

These methods are part of the archaeological toolkit for uncovering human history. By combining different dating approaches, researchers can build more accurate chronologies, revealing how societies and cultures changed over time.

Relative vs Absolute Dating Methods

Principles and Characteristics

Top images from around the web for Principles and Characteristics

• 

  Overview of Relative and Absolute Dating – Introductory Physical Geology Laboratory Manual ... View original

  Is this image relevant?

• 

  How do scientists date rocks and fossils? — Earth@Home View original

  Is this image relevant?

• 

  Overview of Relative and Absolute Dating – Introductory Physical Geology Laboratory Manual ... View original

  Is this image relevant?

• 

  Overview of Relative and Absolute Dating – Introductory Physical Geology Laboratory Manual ... View original

  Is this image relevant?

• 

  How do scientists date rocks and fossils? — Earth@Home View original

  Is this image relevant?

1 of 3

Top images from around the web for Principles and Characteristics

• 

  Overview of Relative and Absolute Dating – Introductory Physical Geology Laboratory Manual ... View original

  Is this image relevant?

• 

  How do scientists date rocks and fossils? — Earth@Home View original

  Is this image relevant?

• 

  Overview of Relative and Absolute Dating – Introductory Physical Geology Laboratory Manual ... View original

  Is this image relevant?

• 

  Overview of Relative and Absolute Dating – Introductory Physical Geology Laboratory Manual ... View original

  Is this image relevant?

• 

  How do scientists date rocks and fossils? — Earth@Home View original

  Is this image relevant?

1 of 3

• Relative dating methods determine artifact or site age in relation to other objects or layers without providing specific calendar dates
• Absolute dating methods provide specific calendar dates or age ranges for artifacts or archaeological sites
• Relative dating establishes chronological sequences based on context and stylistic changes
• Absolute dating utilizes scientific techniques to measure time-dependent properties of materials
• Choice between methods depends on available material, time period studied, and required precision level
• Combining relative and absolute dating often provides the most comprehensive and accurate chronological framework

Relative Dating Techniques

• Stratigraphy analyzes layered deposits to establish relative chronology
• Seriation arranges artifacts or features in a sequence based on stylistic or technological changes
• Cross-dating correlates artifacts or features from different sites based on similarities
• Typology classifies artifacts into groups based on shared characteristics to infer relative age

Absolute Dating Methods

• Radiocarbon dating measures decay of carbon-14 isotopes in organic materials (up to ~50,000 years old)
• Dendrochronology analyzes tree ring patterns to date wooden artifacts and structures
• Thermoluminescence dates ceramics and other heated materials by measuring accumulated radiation
• Potassium-argon dating determines age of volcanic rocks and associated artifacts (millions of years)
• Optically stimulated luminescence dates when mineral grains were last exposed to sunlight

Radiocarbon Dating: Principles and Applications

Fundamental Concepts

• Based on decay of carbon-14 isotopes in organic materials with half-life of approximately 5,730 years
• Assumes relatively constant ratio of carbon-14 to carbon-12 in atmosphere over time
• Accurately dates materials up to about 50,000 years old
• Sample preparation involves cleaning, pretreatment, and conversion to suitable form (carbon dioxide gas or graphite)
• Measurement techniques include liquid scintillation counting, gas proportional counting, and accelerator mass spectrometry (AMS)
• AMS provides most precise results and requires smaller sample sizes

Applications and Limitations

• Dates organic artifacts (textiles, bone tools)
• Analyzes human and animal remains for chronological and dietary information
• Examines charcoal from hearths to establish occupation periods
• Dates organic materials associated with archaeological contexts (seeds, wood)
• Calibration necessary to account for atmospheric carbon-14 variations over time
• Limitations include impact of contamination and reservoir effects in marine environments
• Unable to directly date inorganic materials (stone tools, ceramics)

Calibration and Interpretation

• Dendrochronology and other independently dated records used for calibration
• Calibration curves convert radiocarbon years to calendar years
• IntCal20 is the most recent internationally agreed calibration curve
• Bayesian statistical methods often employed to refine date ranges
• Consideration of archaeological context crucial for accurate interpretation
• Multiple samples and cross-checking with other dating methods improve reliability

Dendrochronology and Thermoluminescence in Archaeology

Dendrochronology: Tree Ring Dating

• Science of dating wood based on analysis of tree ring patterns
• Provides precise calendar dates for wooden artifacts and structures
• Trees produce distinctive growth rings each year influenced by environmental factors (climate, soil conditions)
• Master chronologies constructed by overlapping ring patterns from living trees, historical structures, and archaeological wood samples
• Cross-dating technique matches ring patterns between samples to extend chronologies
• Applications include dating timber structures (log cabins, temples)
• Limitations include need for well-preserved wood and regional master chronologies

Thermoluminescence Dating

• Measures accumulated radiation dose in crystalline materials since last heated or exposed to sunlight
• Useful for ceramics, burnt flint, and other heated archaeological materials
• Dating range extends back to about 300,000 years
• Involves measuring light emitted when sample heated, proportional to time elapsed since last heating or light exposure
• Factors affecting accuracy include environmental radiation levels and sample contamination
• Applications include dating pottery sherds and burnt stones from hearths
• Requires careful sampling and laboratory procedures to ensure reliable results

Comparative Analysis and Integration

• Dendrochronology provides anchor points for radiocarbon calibration curves
• Thermoluminescence complements radiocarbon dating for inorganic materials
• Combining multiple dating methods increases overall chronological accuracy
• Integration with stratigraphic analysis and artifact typologies enhances site interpretation
• Understanding strengths and limitations of each method crucial for appropriate application
• Ongoing research improves precision and extends dating ranges of these techniques

Stratigraphy for Relative Dating

Principles and Concepts

• Study of layered deposits in archaeological sites
• Based on principle that older layers generally found below more recent ones
• Law of Superposition (Nicholas Steno, 1669) states undisturbed stratigraphic sequences have oldest layers at bottom, youngest at top
• Involves identifying distinct layers or strata, their composition, and contained artifacts or features
• Establishes relative chronological sequence of site occupation and activities
• Interfaces between strata (erosional surfaces, buried soils) provide information about site formation processes and temporal gaps

Analysis and Interpretation

• Complex stratigraphy requires careful interpretation to reconstruct chronological sequence accurately
• Intrusions, pit features, and post-depositional disturbances complicate stratigraphic relationships
• Stratigraphic correlation between site areas or multiple sites develops regional chronologies and cultural sequences
• Harris Matrix technique visually represents stratigraphic relationships
• Soil micromorphology analyzes microscopic features of sediments to understand site formation processes
• Integration with absolute dating methods and artifact typologies enhances precision and reliability

Applications in Archaeological Research

• Reconstructs site formation processes and occupation history
• Identifies cultural phases and transitions within a site
• Establishes relative chronology of artifact assemblages
• Assesses site integrity and potential for further investigation
• Guides excavation strategies and sampling procedures
• Contributes to understanding of landscape evolution and environmental changes
• Supports interpretation of spatial organization and activity areas within sites