# Stratigraphy and Relative Dating

History I · Archaeology · https://tryals.app/learn/history-i/stratigraphy-and-relative-dating

## The Ground Is an Archive

Dirt is a dated document. **Superposition** states that in undisturbed deposits, lower layers are older, making depth a relative clock. A site is recorded through the **context**: a single depositional event.

| Principle | Statement | Consequence |
| --- | --- | --- |
| **Superposition** | Lower layers are older | Depth is a relative clock |
| **Cutting** | Cuts are younger than what they cut | Intrusions date after targets |
| **Filling** | Fills are younger than their cut | Contents postdate the pit |
| **Association** | Sealed objects entered together | Context is the dating unit |

The **Harris matrix** diagrams these older/younger relationships as a flowchart of time, separating stratigraphy from soil.

## Termini and Pitfalls

Objects bracket layer ages from one side only.

- **Terminus post quem (TPQ)**: limit after which. A coin from 120 CE inside a fill means the fill closed no earlier than 120.
- **Terminus ante quem (TAQ)**: limit before which. Structures sealed beneath datable layers are older.

$$\text{cut} \Rightarrow \text{younger than everything it cuts}$$

**Residuality** is the classic trap: old things constantly end up in young layers. The **latest** object sets a context's TPQ. The section shows where things are, but **sequence** is the true clock.

## Practice questions

7 of this lesson's 12 practice questions, with answers. The full set is in the app.

### 1. Replay this section’s formation. Order the events from first to last.

**Answer:**

1. Natural subsoil forms the base
2. A clay floor is laid on the subsoil
3. Occupation debris builds up on the floor
4. The building collapses over the debris
5. A pit is cut down through collapse, debris, and floor
6. The pit silts up with fill

**Why:** Superposition orders the layers; the cutting rule slots the pit in after everything it truncates; the filling rule puts the fill last. Three principles, one readable biography of a patch of ground.

Page: https://tryals.app/practice/history-i/stratigraphy-and-relative-dating/replay-this-sections-formation-order-the-events-from-first-to-last

### 2. Match each stratigraphic term to its definition.

**Answer:**

- Context → A single depositional event, one layer, cut, or fill
- Cut → The act of digging, younger than what it truncates
- Fill → Material inside a cut, younger than the cut
- Harris matrix → Flowchart of every older/younger relationship on site

**Why:** Contexts are the atoms, cuts and fills the verbs, and the Harris matrix the grammar that binds a whole site into one temporal sentence.

Page: https://tryals.app/practice/history-i/stratigraphy-and-relative-dating/match-each-stratigraphic-term-to-its-definition

### 3. Each observation gives a **terminus post quem** or a **terminus ante quem** for the wall. Sort them.

**Answer:**

- TPQ (wall is no earlier than…): A 350 CE coin sealed in the wall’s foundation trench, Pottery of the 4th century mixed into the wall’s mortar, A timber felled in 380 CE reused in the wall’s base
- TAQ (wall is no later than…): The wall is buried beneath a datable 600 CE destruction layer, A 550 CE grave is cut down through the wall’s ruins, A 500 CE floor runs over the wall’s demolished stub

**Why:** Everything _inside or beneath_ the wall pushes its date later (TPQ); everything _sealing or cutting its ruins_ pulls the ceiling earlier (TAQ). Between the two termini lives the wall.

Page: https://tryals.app/practice/history-i/stratigraphy-and-relative-dating/each-observation-gives-a-terminus-post-quem-or-a-terminus-ante-quem

### 4. The law of superposition says lower layers are older. Give a situation where a strict reading of it produces a wrong date.

A. Sites where erosion has removed the upper layers
B. Sites occupied continuously, where layers merge indistinguishably
C. Any intrusion: a pit, grave or foundation trench cut from above
D. Layers that were deposited very quickly, compressing the sequence

**Answer:** C. Any intrusion: a pit, grave or foundation trench cut from above

**Why:** Superposition assumes deposition from above and an intrusion violates it by construction, putting a ninth-century burial physically below third-century floors. Recognising cuts is therefore prior to reading the sequence, and it is why Harris matrices record relationships rather than depths.

Page: https://tryals.app/practice/history-i/stratigraphy-and-relative-dating/the-law-of-superposition-says-lower-layers-are-older-give-a

### 5. An object lying deeper than another can still be the younger of the two.

**Answer:** True

**Why:** True. Superposition holds only for undisturbed deposits. A grave cut, a rubbish pit, a burrowing animal or a plough can all place recent material below older layers, which is why excavation records *contexts* and their relationships rather than depths, and why a single intrusive find can misdate an entire sequence.

Page: https://tryals.app/practice/history-i/stratigraphy-and-relative-dating/an-object-lying-deeper-than-another-can-still-be-the-younger-of-the

### 6. A pit cut through three layers contains a coin of 200 CE. Why does the coin date the pit rather than the layers it cuts?

A. Because the layers themselves cannot be dated by any method
B. Because the cut must be younger than everything it passes through
C. Because coins are always found in the layer in which they were minted
D. Because the pit is deeper and therefore older than the layers

**Answer:** B. Because the cut must be younger than everything it passes through

**Why:** The digger is younger than the dug. The coin gives a terminus post quem for the fill, which post-dates the cut, and says nothing about when the sliced layers formed.

Page: https://tryals.app/practice/history-i/stratigraphy-and-relative-dating/a-pit-cut-through-three-layers-contains-a-coin-of-200-ce-why-does

### 7. Which processes can put OLDER objects into YOUNGER deposits?

A. Digging a pit through ancient layers and backfilling it
B. Reusing centuries-old timber in a new building
C. A sealed, undisturbed layer generating new artifacts internally
D. Rivers eroding an old site and redepositing its artifacts

**Answer:** A. Digging a pit through ancient layers and backfilling it; B. Reusing centuries-old timber in a new building; D. Rivers eroding an old site and redepositing its artifacts

**Why:** Residuality has many engines, pits, rivers, reuse. What no process can do is the reverse: place a genuinely future object into a truly sealed deposit. That one-way street is the logic TPQ dating drives on.

Page: https://tryals.app/practice/history-i/stratigraphy-and-relative-dating/which-processes-can-put-older-objects-into-younger-deposits