2 Radiocarbon Dating and Calibration Free Online FlashCards

What event does a radiocarbon date directly estimate?

It estimates when the organism died, not automatically when an associated artifact was made or an archaeological layer formed.

In an uncalibrated radiocarbon age, what does BP mean?

BP means radiocarbon years before AD 1950, the conventional reference point called “present.”

Why does carbon-14 decrease in an organism after death?

After death, an organism no longer replenishes its carbon-14, which then decays at a known rate.

What is the old-wood effect?

Long-lived wood may have died decades or centuries before it was burned or reused, making its date older than the event.

What can sample pretreatment not fix?

Pretreatment removes unwanted material, but it cannot correct a mistaken link between the sample and the event being dated.

How does accelerator mass spectrometry measure radiocarbon?

Accelerator mass spectrometry (AMS) counts carbon isotopes directly and can measure small samples.

What does analytical uncertainty describe—and what does it exclude?

It describes measurement precision, but not every possible error, such as contamination or an unsuitable sample.

Why can’t a radiocarbon age be converted by subtracting it from 1950?

Atmospheric carbon-14 varied over time, so a radiocarbon age cannot be converted to a calendar date by simple subtraction from 1950.

Which calibration curves generally suit terrestrial and marine samples?

Terrestrial Northern Hemisphere samples generally use IntCal20; Southern Hemisphere samples use SHCal20; marine samples use Marine20, often with a local reservoir correction.

Why can precise measurements calibrate to broad or separated date ranges?

Calibration produces probability ranges, sometimes broad or separated; irregular curve sections can limit calendar precision even when measurement is precise.

What does a reported calibrated range at 95% probability mean?

It means the calibrated probability distribution assigns 95% of its probability to the reported range or ranges under the stated model and assumptions; years within them are not necessarily equally likely.

What key details should a calibrated-date report include?

A report should identify the sample and laboratory, radiocarbon age and uncertainty, calibration curve and method, probability level, and any reservoir correction.