Step by Step
1
Stratigraphy and the law of superposition
The law of superposition states that, in an undisturbed sequence of soil or rock layers, lower layers were deposited earlier and are therefore older than the layers above them — unless something has physically overturned or disturbed the sequence (like a landslide flipping layers upside down, or a pit dug down from a later layer into an earlier one).
2
Typology
Classifying artifacts by their style (shape, decoration, manufacturing technique) to establish a sequence — objects with similar styles found across different sites can be assumed to belong to roughly the same time period.
3
Seriation
A more refined technique that orders artifacts based on how their style changes gradually over time — for example, tracking how a particular pottery decoration style becomes more or less popular across a sequence of graves or layers, then using that popularity curve to place undated finds into the sequence.
4
Fluorine dating: a specialized check on contemporaneity
Bones deposited in the same soil environment absorb fluorine from groundwater at roughly the same rate over time. If two bones found together show very different fluorine levels, that's a red flag that they weren't actually deposited at the same time, even though they were found close together — fluorine dating is sometimes used to confirm (or disprove) that two objects are contemporaneous.
Applied Walkthrough
1
Imagine excavating a burial ground with graves at different depths.
2
Stratigraphy already tells you deeper graves are generally older.
3
Now look closer: a particular style of pottery decoration is rare in the deepest graves, common in the middle layer, and rare again near the top — a classic seriation pattern showing that style rising and falling in popularity over time.
4
If two skeletons from what looks like the same grave show wildly different fluorine absorption levels, fluorine dating would suggest one of them may have actually been placed there at a different time than originally assumed, despite appearing to share the same context.
Exam Application
Exams test whether you can state the law of superposition in your own words, explain the difference between typology and seriation with an example, and what fluorine dating is checking for.
⚠ Common Trap
Don't apply the law of superposition blindly without checking for disturbance. A pit dug from a later, higher layer down into an earlier, lower layer means an artifact found deep in the ground might actually be more recent than the surrounding soil suggests — always check the site for signs of disturbance before trusting depth alone.
✓ Quick Self-Check
1. What is the law of superposition?
In an undisturbed sequence, lower layers are older than layers above them.
Tap to reveal / hide
2. What is typology, as a dating method?
Classifying artifacts by style to establish a rough time sequence.
Tap to reveal / hide
3. How does seriation differ from typology?
Seriation tracks how style changes gradually over time (like rising and falling popularity), producing a finer-grained sequence than typology's broader classification.
Tap to reveal / hide
4. What does fluorine dating check for?
Whether bones found together were actually deposited at the same time, based on similar fluorine absorption rates.
Tap to reveal / hide
5. Under what condition does the law of superposition NOT apply directly?
When the layers have been disturbed — for example, overturned by a landslide or cut into by a later pit.
Tap to reveal / hide