ACCUMULATION RATE

The accumulation rate of sediment is usually expressed in cm/year and calculated on the basis of an age-depth model, which may be based on radiocarbon dating or other dating techniques. Variations in the accumulation rate of, for example, peat can give useful information about the hydrology of the system, since the amount of organic material entering the permanently waterlogged lower layers depends on the decay rate in the upper layers, and when the surface is relatively wet, decay is relatively slow and hence the sediment depth increases rapidly, compared with drier conditions when the decay rate is higher. Accumulation rate data are also an important parameter for absolute counting of pollen, spores and other microfossils, since when combined with absolute counting they permit estimation of annual influx of biotic proxies to the sedimentary record. Calculating the accumulation rate is dependent on establishing an independent chronology, and therefore affected by the problems common to age-depth models.

[See alsogrentzhorizont, peat and peatlands, pollen accumulation rate, recurrence surface]