A RECORD OF LATE PLEISTOCENE AND HOLOCENE CARBON ACCUMULATION AND CLIMATE CHANGE FROM AN EQUATORIAL PEAT BOG

A 9.5 m peat core from a peat deposit in the central lowlands of Kalimantan (Indonesian Borneo) reveals that organic matter accumulation in the Sunda Shelf area started over 22,000 ¹⁴C yrs ago during the Last Glacial Maximum (LGM), representing the first evidence of ombrotrophic peat accumulation in the lowlands of Southeast Asia since the late Pleistocene. Most other lowland peat deposits in this region document the onset of carbon accumulation during the early or middle Holocene. The core shows that organic matter accumulation and thus carbon storage was not uniform and some intervals just shortly after the LGM may represent climatic changes that favoured degradation and thus carbon release to the atmosphere. Carbon storage was slow or negative during most of the late Pleistocene, but was rapid during the early Holocene. More than 3.5 m of peat accumulated between 11,000 and 7,500 ¹⁴C yrs BP, indicating that Southeast Asia possibly acted as a large sink of atmospheric CO₂ during that time. This may, in part, have contributed to the decrease in atmospheric CO₂ in the early Holocene to a minimal 260 parts per million by volume (p.p.m.v.) around 8,000 yr BP. The 20 p.p.m.v. rise over the last 8,000 yrs observed in the Taylor Dome ice core has been attributed to a decrease in terrestrial biomass and also coincides with a reduced organic carbon accumulation rate in the Kalimantan peat core as well as at other sites around Southeast Asia.