The carbon isotope ratios of bog peat in the Ozegahara peatland, Japan, were measured. The vertical variation of the bulk peat featured: 1) rapid decrease of the carbon isotope ratio (δ13C) near the surface, 2) broad rises in the ratio around depths corresponding to 3000, 5500, 7500 years BP with a period of approximately 2500 years, and 3) a further decrease toward the bottom. In order to understand the reasons for the changes, peat components were separated and their isotopic composition measured along with modern peat-forming vegetation. The selective decay of holocellulose is responsible for the rapid decrease of δ13C in the surface layers, and the transition from earlier vegetation caused the further decrease of δ13C near the bottom. The decay constant for holocellulose was estimated to be as small as 0.001 yr-1. The variation of δ13C seemed to be synchronized with sea level change, but showed poor correlation with solar activity and the temperature change estimated from pollen analysis. The δ13C of peat mosses lacking in stomata would increase with the rise in atmospheric CO2. The increase in the atmospheric CO2 occurring synchronously with sea level rise could be the reason for the periodical change. Some climatic information of the Holocene period may have been recorded in the Ozegahara bog peat.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology