How to Use the OxCal Program

ANT 207 General Archaeology

For your exercise on archaeological dating, you are asked to use OxCal to calibrate a date in radiocarbon years. To use OxCal, follow these steps:

1) Go to the computers in the archaeology lab, and choose one that is already on.

2) Click on the Oxcal icon, which should be on the desktop. If it’s not there, goto the program menu.

3) Once you’ve clicked the icon, you should see a menu titled “input wizard”

4) Click on “Calibrate a radiocarbon date” in the “Single Plot” section of the menu.

5) Immediately, an input box will appear.

6) In the R_Date box, put in a number, such as 1, for the first radiocarbon date you’re calibrating.

7) In the first number box, type the radiocarbon date you want calibrated

8) In the + box, type 120, which is the standard error for conventional radiocarbon dates.

9) Now click OK

10) An Untitled window with a graph will appear. To make it easier to read, click on the + button until it is large enough.

11) The blue wavy line is the tree-ring calibration curve, like the ones we drew in class.

12) The read curve in the left of the window is the statistical probability of the date given being correct, not counting the wavy curve.

13) The black lump taking up most of the screen is a graphical representation of the probability of the date being correct, combining statistical probability and the calibration curve. See how some dates are more probable than others?

14) The black writing in the upper right-hand corner of the box is the calibrated date spread according to percentage probability. 68.2% is less certain, but with a smaller range, while 95.4% is much likelier to be correct, but is a wider spread.

15) Drop the + range from 120, as in a conventional date, to 20, which would be standard for an AMS date. What difference does it make?

Happy calibrating!