Final answer:
Calibrated radiocarbon dates are adjusted for atmospheric carbon-14 level fluctuations and are based on the decay of carbon-14 isotopes, expressed with a range indicating uncertainty. They provide an approximation rather than an exact age and can be affected by environmental factors.
Step-by-step explanation:
Calibrated radiocarbon dating involves refining conventional radiocarbon age estimates based on comparison with a calibration curve, typically derived from dendrochronologically-dated tree rings. Calibrated dates account for variations in atmospheric carbon-14 levels over time, which influence the initial starting point of the carbon-14 decay process.
The correct statements identifying what calibrated radiocarbon dates are as follows:
- A) True: Calibrated radiocarbon dates are indeed based on the radioactive decay of the carbon-14 isotope.
- C) True: Calibrated dates are adjusted for fluctuations in atmospheric carbon-14 levels.
- D) True: Calibrated dates are typically expressed with a range or error margin reflecting the uncertainties inherent in the process and the calibration curve.
The incorrect statements are:
- B) False: Calibrated dates provide an approximation of age, not an exact date, due to a range of possible values on the calibration curve.
- E) False: Calibrated dates can be affected by environmental factors or contamination, which can alter the initial amount of carbon-14 in the sample.
- F) False: The calibration curve is based on the understanding that atmospheric carbon-14 concentration has varied over time, not remained constant, which is why calibration is necessary.