datingsider for voksne Haderslev Lichenometric dating curve

Absolute ages have been derived through develooment of a lichen growth curve based largely on the commonly used species of “3” is comparable to those from southern Alaska, Baffin Island, Swedish Lapland, and the Colorado Front Range.

Lichenometric dating curve-54

Lichenometry is a dating technique that uses lichens to obtain estimates of relative or absolute ages of rock-bearing substrates.

It is based on the general assumptions that: a) stabilization and succeeding colonization of lichen-free rocks occur shortly after deposition and b) subsequent lichen growth occurs with a predictable pattern as a function of time.

The ‘great period’ of growth lasts for approximately 20 years after the erection of the gravestone.

The lichen factor (growth after 100 years) is correlated with the growth after 25 and 250 years indicating that it is a representative index of the growth rates. Calculated lichen factors for acidic igneous substrates range from 33 to 104 mm.

Species often reach ages of several thousand years, perhaps even to ≃ 9000 yr BP.

Searches of bouldery Holocene moraines fronting small cirque glaciers in the arctic and alpine terrain of the central Brooks Range reveal patterns of selected lichen species consistent on the basis of maximum thallus diameters. These data permit the development of lichenometric growth curves on acidic igneous, basic igneous, sandstone and slate substrates in most areas of Highland Scotland.The colonisation of gravestones, which is extremely erratic, takes place after a minimum of eight years.The distributions of different types of gravestones are non-uniform in both time and space, making the comparison of growth rates on different rock types impractical.The results indicate that there may be a gradual decrease in the growth rates from W to E, reflecting the decreasing maritime influence towards the E.We have computed surface ice velocity by measuring lichens along 1200 m of a supraglacial boulder train.