SEDIMENTOLOGY AND HUMIFICATION INDEX OF PEAT DEPOSITS FROM NORTHWEST ICELAND

The purpose of this study is to reconstruct a climate proxy record from peat deposits in Northwest Iceland for part of the Holocene period. Fieldwork was conducted at two sites: Raugkollur (RA-05-01) and Svinavatn (SN-05-01). Two cm thick samples of peat were collected at 5 cm intervals from the two outcrops. Standard sedimentology analyses including the determination of mass magnetic susceptibility, water content, and loss on ignition, were performed on all samples from the RA-05-01 site. The degree of humification, the extent to which peat has decomposed, is used as a proxy for precipitation. Measurements of absorbance and percent light transmission were performed on a Spectronic 20 Genesys at 540 nm. Tephra layers are present at depths of 8 cm, 40 cm, 90 cm - 95 cm, 114 cm, and 138 cm at the RA-05-01 site. A visual examination of tephra samples indicates rhyolitic composition, and samples were submitted for geochemical analysis. Peaks in mass magnetic susceptibility occur at depths of 66 cm, 90 cm - 95 cm, 114 cm, 116 cm, 120 cm, 125 cm, and 138 cm - 145 cm, representing an increase in mineral matter. Water content data shows troughs at depths of 54 cm, 66 cm, 90 cm - 95 cm, 114 cm, 120 cm, 132 cm, and 138 cm - 145 cm. These troughs reflect increased bulk density. Low values of organic and inorganic carbon content occur at depths of 0 - 8 cm, 54 cm, 66 cm, 90 cm - 95 cm, 114 cm, 120 cm, and 132 cm – 145 cm. Peaks in percent light transmission occur at depths of 54 cm, 66 cm, 90 cm - 95 cm, 114 cm, 138 cm - 145 cm. The peaks correspond to low humification and are interpreted as wet climatic conditions. Intervals of relative climatic stability are interpreted from uniform magnetic susceptibility measurements, water content, and organic and inorganic carbon content from 15 cm - 35 cm, 70 cm - 85 cm, and 100 cm - 105 cm. Laboratory analyses for the second site, SN-05-01, are in progress. Interpretations from sedimentology data and humification indices from these two sites reflect increased inputs of ash and/or fluctuations in precipitation throughout the Holocene. Five wood samples were submitted for radiocarbon dating, which will help determine the timing of the fluctuations.