This study examined the effects of commonly used oxidants in sedimentary macroscopic charcoal analysis on two sediment cores from Thirlmere Lakes National Park, Southeast Australia. The cores, from Lake Werri Berri (WB3) and Lake Couridjah (LC2), span ~900 years and 135,000 years, respectively. The Charcoal Accumulation Rate (CHAR) for both charcoal area and count was quantified using four different chemical treatments and compared to a control using only water. We also quantified the Charring Intensity (CI) of isolated charcoal fragments, a proxy for the severity/intensity of fire, determined using the FTIR spectral characteristics of the remaining charcoal after each treatment. We found significant differences in both the area and number of particles across all treatments in both cores. Significantly, we found substantial differences in CI between treatments, with few charcoal particles formed in low-severity fire (e.g., below ~400 °C or 3.0 °C.s.106) in groups treated with an oxid
Vegetation structure in vast semi-arid to temperate continental land masses, such as Australia, plays a considerable role in global terrestrial carbon sequestration. However, whether soil carbon from these regions is a net atmospheric carbon source or sink remains contentious, introducing large uncertainties on long-term storage of vegetation-sequestered carbon dioxide. We investigate the interplay between catchment erosion quantified using uranium isotopes, vegetation (pollen), catchment carbon cycling, wetland response (diatoms), and lake carbon accumulation on glacial-interglacial timescales in south-eastern Australia. The analyses are applied to sediments from Lake Couridjah, in the Sydney Basin during the last (133.5 ka to 107.6 ka) and current (17.8 cal ka BP to present day) glacial-interglacial transitions. Robust phase-relationships between catchment erosion, vegetation composition and carbon cycling during both glacial-interglacial periods were revealed by statistical analyses
Abstract
The widespread formation of organic rich sediments in south-east Australia during the Holocene (Marine Isotope Stage [MIS] 1) reflects the return of wetter and warmer climates following the Last Glacial Maximum (LGM). Yet, little is known about whether a similar event occurred in the region during the previous interglacial (MIS 5e). A 6.8 m sediment core (#LC2) from the now ephemeral Lake Couridjah, Greater Blue Mountains World Heritage Area, Australia, provides insight into this question. Organic rich sediments associated with both MIS 1 and 5e are identified using C and optically stimulated luminescence (OSL) dating techniques. Also apparent are less organic sedimentary units representing MIS 6, 5d and 2 and a large depositional hiatus. Sediment δ C values (−34 to −26‰) suggests that C vegetation dominates the organic matter source through the entire sequence. The pollen record highlights the prevalence of sclerophyll trees and shrubs, with local hydrological cha