Dating methods

As commented in the video, accurate dating is of fundamental importance to paleoclimatic and paleoenvironmental research (1-4). Indeed, without a reliable estimate of the age of these archives, it is impossible to link them together, that is to say whether they are contemporary, or one precedes the other. It is also by associating these paleoclimatic archives with time that we can identify cyclical phenomena such as, for example, the alternation of glacial and interglacial periods.

As described by R.S. Bradley in Paleoclimatology (1), dating methods fall into four basic categories (Figure 1):

• radioisotopic methods, which are based on the rate of atomic disintegration in a sample or its surrounding environment;
• paleomagnetic methods, which rely on past reversals of the Earth’s magnetic field and their effects on a sample;
• organic and inorganic chemical methods, which are based on time-dependent chemical changes in the sample or chemical characteristics of a sample;
• biological methods, which are based on the growth of an organism to date the substrate on which it is found.

Different dating methods will be more suitable than others depending on the time period of interest (Figure 2).

Figure 1: Principal dating methods used in paleoclimatic and palaeoenvironmental research (based on 1).

Figure 2: Schematic diagram showing the age ranges for which different dating methods are suitable (1)