Ch. 5 - Chronology Building: How To Get A Date

Question 1

Absolute date

Answer 1

A date expressed in specific units of scientific measurement, such as days, years, centuries, or millennia; absolute determinations attempting to pinpoint a discrete, known interval in time.

Question 2

Relative dates

Answer 2

Dates expressed relative to one another (for instance, earlier, later, more recent) instead of in absolute terms.

Question 3

Index fossil concept

Answer 3

The idea that strata containing similar fossil assemblages are of similar age. This concept enables archaeologists to characterize and date strata within sites using distinctive artifact forms that research shows to be diagnostic of a particular period of time.

Question 4

Law of superposition

Answer 4

The geologic principle that in any pile of sedimentary rocks that have not been disturbed by folding or overturning, each bed is older than the layers above and younger than the layers below.

Question 5

Time markers

Answer 5

Artifact forms that, as with index fossils in geology, research shows to be diagnostic of a particular period of time.

Question 6

Seriation

Answer 6

A relative dating method that orders artifacts based on the assumption that one cultural style slowly replaces an earlier style over time. With a master seriation diagram, sites can be dated based on their frequency of several artifact (for instance, ceramic) styles.

Question 7

Tree-ring dating

Answer 7

(Dendrochronology)

The use of annual growth rings in trees to assign calendar ages to ancient wood samples.

Question 8

Half-life (of 14C)

Answer 8

The time required for half of the carbon-14 available in an organic sample to decay.

5730 years.

Question 9

Photosynthetic pathways

Answer 9

The specific chemical processes through which plants metabolize carbon. Because the three major pathways discriminate against carbon-13 in different ways, similarly aged plants that use different pathways can produce different radiocarbon ages.

Question 10

Reservoir effect

Answer 10

When organisms take in carbon from a source that is depleted of or enriched in carbon-14 to the relative atmosphere; carbon dating of such samples may return ages that are considerably older or younger than they actually are.

Question 11

de Vries effects

Answer 11

Fluctuations in the radiocarbon-dating calibration curve produced by variations in the atmosphere’s carbon-14 content; these can cause radiocarbon dates to calibrate to more than one calendar age.

Question 12

Accelerator Mass Spectrometry (AMS)

Answer 12

A method of radiocarbon dating that counts the proportion of carbon isotopes directly (rather that using the Geiger counter method), thereby dramatically reducing the quantity of database material required.

Question 13

Trapped charge dating

Answer 13

Forms of dating that rely upon the fact that electrons become trapped in minerals, crystal lattices as a function of background radiation; the age of the specimen is the total radiation received divided by the annual dose of radiation.

Question 14

Dosimeter

Answer 14

A device to measure the amount of gamma radiation emitted by sediments. It is normally buried in a stratum for a year to record the annual dose of radiation. Often a short length of pure copper tubing filled with calcium sulfate.

Question 15

ThermoLuminescence (TL)

Answer 15

A trapped charge dating technology used on ceramics and burnt stone artifacts – anything mineral that has been heated to more than 500 degrees C.

Question 16

Neanderthals

Answer 16

An early form of Humans who lived in Europe and the Near East about 300,000 to 30,000 years ago. Biological anthropologists debate whether Neanderthals were in the direct evolutionary line leading to Homo sapiens.

Question 17

Optically Stimulated Luminescence (OSL)

Answer 17

A trapped charge dating technique used to date sediments; it measures the time elapsed between the last time a few moments’ exposure to sunlight reset the clock to zero and the present.

Question 18

Electron Spin Resonance (ESR)

Answer 18

A trapped charge technique used to date tooth enamel and burnt stone tools; it can date teeth that are beyond the range of radiocarbon dating.

Question 19

Homo erectus

Answer 19

A hominin who lived in Africa, Asia, and Europe between 2 million and 500,000 years ago. These hominins walked upright, made simple stone tools and may have used fire.

Question 20

Argon-argon dating

Answer 20

A high-precision method for estimating the relative quantities of argon-39 and argon-40 gas; used to date volcanic ashes that are between 500,000 and several million years old.

Question 21

Old wood problem

Answer 21

A potential problem with radiocarbon (or tree-ring) dating in which old wood has been scavenged and reused in a later archaeological site; the resulting date is not a true age of the associated human activity.