THE C-14 CONTENT OF MODERN VEGETATION SAMPLES FROM THE FLANKS OF THE KATLA VOLCANO, SOUTHERN ICELAND

Samples of living terrestrial plants comprising a moss (Calliergon sp. ), Carer spp. and Alchemilla spp. were collected from the surface of t he mire at Engimyri in Myrdalur, southern Iceland, 10 km from the crat er rim of the central complex of the Katla volcano. This area is 16 km from the fissures active in AD 1918 and was directly affected by the tephra fall. Although there is no hot-spring or fumerole activity in t he area, sufficient volcanic activity during the weeks preceding sampl e collection produced a strong sulphurous odor in the streams. As part of a large-scale dating program, we analyzed the modern vegetation to determine whether anomalies caused by the uptake of ''old'' volcanic CO2 were apparent. The results showed C-14 values for the Calliergon s p., Carer spp. and Alchemilla spp. of 113.2 +/- 0.6 pMC, 113.03 +/- 0. 52 pMC and 113.10 +/- 0.6 pMC, respectively. The delta(13)C(PDB) value s were -28.7 parts per thousand, -28.0 parts per thousand and -27.0 pa rts per thousand, respectively. Similar vegetation, i.e., terrestrial plants from a marsh environment in southern Scotland, were also analyz ed as a comparison and gave C-14 values of 113.16 +/- 0.55 and 112.98 +/- 0.59 pMC. The implication is that Icelandic vegetation at Engimyri is not affected by ''old'' carbon from volcanic emissions and dates o btained for this Icelandic peat are acceptable and directly comparable with Scottish peat.