a date expressed as specific units of scientific measurement, such as days, years, centuries, or millenia; absolute determinations attempting to pinpoint a discrete, known interval in time
accelerator mass spectrometry (AMS)
a method of radocarbon dating that counts the proportion of carbon isotopes directly (rather than using the indirect Geiger counter method), thereby dramatically reducing the quantity of datable material required. younger then they actually are. ALLOWS US TO RADIOCARBON-DATE MINUTE AMOUNTS OF CARBON
a high-precision method for estimating the relative quantities of argon-39 to argon-40 gas; used to date volcanic ashes that are between 500,00 and several million years old
de Vries effects
fluctuations in the 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.
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. Dositmeters are often a short length of pure copper filled with calcium sulfate.
electron spin resonance (ESR)
a trapped charge technique used to date tooth enamel and burned stone tools; it can date teeth that are beyond the range of radiocarbon dating.
a hominid who lived in africa, asia, and europe between 2 million and 500,00 years ago. these hominids walked upright, made simple stone tools, and may have used fire
index fossil concept
the idea that strata containing similar fossil assemblies 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.
law of superposition
the geological principle stating 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; also known STENOS LAW
the time required for half of the carbon-14 available in organic sample to decay; the standard is 5568 years although it is known that the half-life is closer to 5730 years.
neanderthals (or neandertals)
an early form of humans who lived in europe and the near east about 300,00 o 30,000 years ago; biological anthropologists debate whether neanderthals were in the direct evolutionary line leading to homo sapiens
old wood problem
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
optically stimulated luminescence (OSL)
a trapped charge dating technique used to date sediments; the age is the time elapsed between the last time a few moments exposure to sunlight reset the clock to zero and the present.
the specific chemical process which plants metabolize carbon; the three major pathways discriminate against carbon-14 in different ways, therefore similary aged plants that use different pathways can produce different radiocarbon ages.
an absolute dating technique that monitors the decay of potassium (K-40) into argon gas (Ar-40)
dates expressed relative to one another (for instance, earlier, later, more recent, and so forth) instead of absolute terms.
when organisms take in carbon from a source that is depleted of or enriched in 14C relative to the atmosphere; such samples may return ages that are considerably older or younger than they actually are
rock formed when the weathered products of preexisting rocks have been transported by and deposited in water and are turned once again to stone.
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.
a trapped charge dating technique used on ceramics and burnt sotne artifacts -- anything mineral that has been heated to more than 500 degree celcius
similar to index fossils in geology; artifact forms that research shows to be diagnostic of a particular period of time.
trapped charge dating
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