Variations in the D/H and 18O/ 16O ratios in cellulose extracted from a peat bog core

Abstract

A peat core from a raised bog covering the period 3100 to 2400 14 C years B.P. has been analysed for D/H and 18 O/ 16 O ratios. These analyses were applied to cellulose, extracted from 56 successive layers of 1 cm thickness. D/H ratios were determined for the carbon bonded hydrogen; 18 O/ 16 O analyses were performed by applying a new method. For the interpretation of the results obtained on peat, the isotopic ratios of 11 living bog plant species were measured, showing a relatively large scatter. Most pronounced is a depletion in D of about 25‰ and in 18 O of about 5‰ of the Sphagnum mosses relative to the vascular bog plants. This different isotopic composition is reflected by the δD and δ 18 O records of the peat core, because the abundance of the remains of non-vascular plants is variable. If this effect is taken account of, the remaining δD variations appear to be too large to be attributed to variations in the isotopic compositions of precipitation. As palaeoclimatic indicators the D/H and 18 O/ 16 O ratio qualitatively agree with the pollen analytical evidence for the climatic deterioration of the Subboreal-Subatlantic transition.