Introduction to Archaeology: Class 7
Relative dating: Chronology as brain teaser - stratigraphy and index fossils
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Copyright Bruce Owen 2002
- Two kinds of dating: relative and absolute
- Relative dating
puts things in order, older to younger, without specifying dates in years
- Relative dating methods
- Stratigraphy
(study of strata, or layers of earth)
- The layer-cake model, with oldest at the bottom and most recent at the top
- Steno's law
, or the law of superposition
- Stratigraphy: the study and interpretation of strata
- A field example
- feature
: a localized stratigraphic unit: pit, hearth, wall, etc.
- Plan views: looking down; what you see while you are excavating
- Profile views: looking at the sidewalls of the excavation; what you see when some strata have been removed
- Recording and interpreting strata in the field
- Munsell colors, grain size charts, etc.
- More examples: getting the order of deposition right
- Association of artifacts with strata
- Artifacts may or may not have been made or used at the time the stratum accumulated
- redeposition
- intrusion ("intrusive" artifacts)
- curation
- "Natural stratigraphy" or cultural stratigraphy vs. arbitrary strata (or arbitrary levels)
- Uh-oh... inverted stratigraphy
- Basketloads
- Where was the ground level? Cancha de Yacango tomb example
- Cancha de Yacango strata cut example
- What if the radiocarbon dates are out of order?
- Cultural vs. natural stratigraphy
- Algodonal example with erosion and talus deposition
- Jericho example
- Where was the ground surface at different times?
- What was the order of construction of walls, cutting of trenches, etc.?
- Linking plan views to stratigraphy
- Stratigraphic relationships of features that are not on top of one another
- Sectioning features to get the internal profile
- Cancha de Yacango example: profiles to answer specific questions
- arbitrary levels to answer specific questions
- Keeping cultural strata together
- Why do we dig out the contents of a pit before digging around it?
- Taking the site apart in the reverse order that it formed in
- Index fossil
concept
- Linking contemporary strata by their contents rather than by their physical relationships
- Not nearly as precise
- Useful to correlate strata at different sites
- We'll build on this notion next time...