Jökull - 01.12.2007, Page 28

Maciej Dąbski
Figure 4. Lichen dating curve (Bradwell 2004) and dates of Fláajökull moraine ridges. – Reiknaður vöxtur
fléttna á jökulgörðum útfrá stærð þeirra.
Table 2. Dates of Fláajökull moraine rides formation obtained with use of different lichenometric methods. –
Reiknaður aldur jökulgarða I–V við Fláajökul útfrá stærð fléttna við jökuljaðarinn.
moraine I II III IV V
single largest lichen (mm) 150 74 150 66 40
single largest lichen* (mm) 83 74 80 66 40
“1-in-1000” lichen** (mm) 80 72 59 54 46
5 largest* lichens (mm) 83,80,73,70,69 74,73,63,63,62 80,70,60,59,53 66,64,62,58,51 40,40,40,39,39
average of 5 largest* (mm) 75 67 64,4 60,2 39,6
frequency gradient (-1)** 0.0505 0.0554 0.0748 0.0871 0.095
A (years AD) 1905 1915 1918 1923 1949
B (years AD) 1791 1832 1806 1862 1927
C (years AD) 1804 1841 1884 1898 1915
D (years AD) 1898 1906 1930 1939 1944
E (years AD) 1870/94 1907 1920/25 1932/33 1934/35
* without single exceptionally large lichen (150 mm)
** without largest lichens (reduction described in this paper)
A-years: calculated with the method used by Evans et al., average of 5 largest thalli. B-years: calculated with use of the
Bradwell’s (2001) dating curve (single largest thallus). C-years: calculated with use of the Bradwell’s (2001) dating curve
and use of predicted “1-in-1000” thallus (Lock et al. 1979). D-years: calculated with use of the frequency gradient approach
(Bradwell 2004) with correction described in this paper. E-years: obtained in the previous research (Dąbski 2002)
26 JÖKULL No. 57