Vegetation and precipitation change inferred from the δ13C and δ2H values of n-alkanes from lake sediment from 18 cal ka BP, tropical NE Australia
Journal Publication ResearchOnline@JCUAbstract
The carbon and hydrogen isotope compositions (δ13C and δ2H) of sedimentary n-alkanes are excellent recorders of past vegetation and precipitation change. Yet, few studies have combined and compared n-alkanes in modern plants and paleoenvironmental records. Here we analyzed the δ13C and δ2H values of n-alkanes (δ13Calk and δ2Halk, respectively) from a 7-m-long sediment sequence in Lake Barrine, modern catchment soils, fallen leaf mixtures, rainforest tree leaves and grasses from tropical northeastern Australia. We exploited the correlation between the relative abundances, δ13C, and δ2H values of n-alkanes from fresh modern rainforest leaves, grasses, fallen leaves, soils and surface sediments. Based on this, we developed two binary mixing models to determine C3 plant abundances and the δ2H values of precipitation (δ2HP-R) to study rainfall and vegetation in the Lake Barrine catchment since 18.3 cal ka BP. Combining the results of this study with mean annual air temperature, pollen, and clastic influx, we reconstructed a robust climatic and environmental record for this site and compared it with other regional paleoenvironmental records. The modern samples indicate slight 13C enrichment and obvious 2H depletion in the n-alkanes from fresh rainforest leaves, fallen leaves, soils, and surface sediments, which is possibly due to microbial build-up of n-alkanes during decomposition. A broad consistency in regional paleoclimate trends was identified, including a cool, dry Last Glacial Maximum (23–17.0 cal ka BP), warmer, wetter last deglacial (17.0–14.9 cal ka BP), wetter with stable temperature Antarctic cold reversal (14.9–12.8 cal ka BP), (possibly) cooler, drier Younger Dryas (12.8–11.6 cal ka BP), warmer, wetter early-to-middle Holocene (11.6–5 cal ka BP) and cooler, slightly drier and more variable late Holocene (5 cal ka BP to the present).
Journal
Quaternary Science Reviews
Publication Name
Quaternary Science Reviews
Volume
337
ISBN/ISSN
1873-457X
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Pages Count
15
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Publisher
Elsevier
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DOI
10.1016/j.quascirev.2024.108807