This chapter reviews some specific environmental configurations where 14C dating can be applied and warns of some issues to be aware of.
In this chapter, we discuss a series of tips for selecting plant macro-remains for 14C measurement. We review the different geological, biological, and sedimentary contexts (dense forest, volcanic area (fig. 1), freshwater environments, karst and cave), the major types of plant residues (tree-ring, leave, seed, pollen, phytolith), and point out the most common pitfalls (“old wood effect,” “canopy effect,” “freshwater reservoir age” (fig. 2), “hard water effect,” bioturbation, . . .). Here, we also highlight the interest of wiggle-matching for wood artifact dating. The chapter concludes with some reminders and suggestions for the storage and chemical preparation of these macrorests.
Figure 1 : Volcano effect—The color of the CO2 symbols represents their 14C content (see F14C color scale at the base of the figure). The thin arrows are for CO2 fluxes and mixtures between CO2 sources, the thick arrows for carbon incorporation by plants through photosynthesis. CO2 emitted by volcano is 14C-deprived and mixes with free atmospheric CO2. Plants under the influence of volcanic plume, fumaroles or diffuse emission photosynthesize from a mixed 14C-depleted CO2. As a result, the plant F14C is lower than the F14C of free atmospheric CO2.
Figure 2 : Atmospheric impact of freshwater reservoir—The color of the CO2 symbols represents their 14C content (see F14C color scale at the base of the figure). The thin arrows are for CO2 fluxes and mixtures between CO2 sources, the thick arrows for carbon incorporation by plants through photosynthesis. CO2 emitted by lake activity (DIC degassing) is 14C-depleted and mixes with free atmospheric CO2. Plants under the influence of emitted CO2 photosynthesize from a mixed 14C-depleted CO2. As a result, the plant F14C (floating and in the vicinity) is lower than the F14C of free atmospheric CO2
Reference: Hatté C., Jull A.J.T., 2023. Chronology of plant macrofossils. Encyclopedia of Quaternary Sciences, 3rd edition – doi: 10.1016/B978-0-323-99931-1.0
