Carbon dating practice problems
With well-established calibration data sets (e.g., ), the procedure is straightforward, but calculated 1-sigma and 2-sigma calibrated age ranges commonly are larger than the corresponding radiocarbon age ranges.
Radiocarbon ages on marine and freshwater shells, foraminifera, and aquatic mosses carry additional uncertainty that must be considered when using these organisms to date subaqueous landslides or lakes impounded by landslides.
There are two sources of uncertainty in radiocarbon ages.
Plant fossils in growth position on a surface over which a landslide travels are ideal material for dating because the landslide killed the plants; in other words, the ages of the fossils and the landslide are the same, given the aforementioned uncertainties.
Similar errors result from modern argon being absorbed on to the surface and interior of the sample, thereby invalidating the second assumption.
Fortunately, atmospheric argon contamination can be assessed by measurement of the different isotopes of argon present.
The outer-ring issue can be circumvented by dating twigs, leaves, seeds, and other delicate plant fossils, although such materials commonly are not present in landslide deposits.
Some landslides can be dated indirectly, using plant material contained within sediments deposited in an upstream lake impounded behind the debris dam or within outburst flood sediments deposited when the dam is breached by overflow.