HOLOCENE CLIMATE VARIABILITY INTERPRETED FROM PEAT DEPOSITS ON NORTHWEST ICELAND

Sedimentology analyses and the degree of peat humification were used to determine Holocene climate variability at two peat outcrops, near Raudkollur and Svínavatn, on northwest Iceland. Five radiocarbon ages collected at the sites and an extrapolated age-depth model show that the sediments at both sites record most of the Holocene (post Saksunarvatn Ash deposition). An increase in mass magnetic susceptibility, decrease in water content, and decrease in organic carbon are present at both sites in the early Holocene. This combination of sedimentology data are interpreted as Preboreal cooling, which is documented throughout the North Atlantic region. The degree of peat humification is interpreted from measurements of the percent absorbance and percent transmission analyzed on a spectrophotometer at 540 nm. Low values of the degree of peat humification are interpreted from high percent transmission and low absorbance from the Raudkollur site during the early Holocene, which indicates wet and/or cool conditions. The degree of peat humification correlates well with the sedimentology data. Drier and warmer conditions follow this wet and cool period with continued climatic stability for at least 3500 years. A second period of wet and cool conditions is interpreted from sedimentology records from both sites and a decrease in the degree of peat humification at the Raudkollur site at approximately 5300 ± 100 yr B.P. This is interpreted as the onset of Neoglaciation cooling, which correlates with other terrestrial and marine records from north and northwest Iceland. Measurements of the degree of peat humification at the Svínavatn site are in progress. The peat stratigraphy at both sites includes ash layers. At least five major rhyolitic ash layers are present at the Raudkollur site, and more than seven tephra horizons are present at the Svínavatn site. Geochemical analyses of the ash layers are in progress, but preliminary analysis suggest that at least three layers are Holocene Hekla tephra layers.