LICHENOMETRY
Lichens are symbiotic communities
algae conduct photosynthesis and supply the community with nutrients
fungi take up water and minerals
| fruticose |
 |
| foliose |
 |
| crustose |
 |
History: R.E. Beschel (1961) first used lichens in 1950's to study air pollution and to date glacial moraines in Swiss and Italian Alps
PRINCIPALS:
Diameter = f(E, A)
Environment
lichen growth rates vary with elevation, proximity to sea, aspect
lichen growth rates vary among substrates (rock types)
Age: the size of the lichen thallus increases with age.
assume growth begins soon after the deposit stabilized
growth rate slows with age
The largest lichen on the deposit is the oldest, i.e. first established
METHODS:
CALIBRATION
Establish growth rates
a. dated deposits: buildings, bridges, gravestones, landslides
b. repeated measurement of thalli
Determine age of deposit (glacial moraines, pueblo walls) based on size of lichens
AGE (yr) = Diameter (mm) / Rate (mm/yr)
relative dating: extent of coverage of rocks by lichens
PROBLEMS:
Only some types are usable e.g., Rhizocarpon geographicum
© W.P.Armstrong 2003 |
Other forms fragment, or growth not radial
The ecology of lichens poorly known
Attempts to establish growth curves and date deposits in southern Rocky Mountains have failed (Carrera an Andrews, 1973)
Links
- Bull, W.B. 1996.
Dating San Andreas fault earthquakes with lichenometry: Geology 24: 111-114. Viewed online at
http://www.activetectonics.com/articles/Dating_SN_quakes_w_lichens.pdf
September 25, 2003.
- Solomina, Olgaa and Calkinb, Parker E. 2003.
Lichenometry as applied to moraines in Alaska, U.S.A., and Kamchatka, Russia. Arctic, Antarctic,
and Alpine Research 35:129-143. Viewed online at
http://www.bioone.org/bioone/?request=get-document&issn=1523-0430&volume=035&issue=02&page=0129
September 25, 2003.
Lichenometry Readings
HOMEWORK
