DOI: 10.1016/j.palaeo.2014.07.040
论文题名: Contribution of organic matter molecular proxies to interpretation of the last 55ka of the Lynch's Crater record (NE Australia)
作者: Kaal J. ; Schellekens J. ; Nierop K.G.J. ; Marti´nez Cortizas A. ; Muller J.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2014
卷: 414 起始页码: 20
结束页码: 31
语种: 英语
英文关键词: Degree of peat humification
; Lynch's Crater
; Molecular proxies
; NE Australia
; Palaeoclimatology
; Palaeoecology
英文摘要: The Lynch's Crater (NE Australia) deposit is a key information source on Late-Quaternary palaeoenvironmental change, including human-induced deforestation since the arrival of Aboriginals, megaherbivore extinction and southern hemisphere tropical climate dynamics. This study adds to the important dataset available for the site by assessing the molecular composition of organic matter in the record using pyrolysis-GC-MS to elucidate ecological and hydrological conditions since 55. ka BP.Pyrolysates were dominated by methylene chain compounds (MCCs) and lignin products (methoxyphenols). Concomitant increases in MCCs and aquatic source indicators (biogenic opaline silica, Si:Al ratio, SEM-visible debris of sponges and diatoms and aquatic pollen taxa), which roughly coincide with abrupt climate events in GISP2 δ18O (Heinrich event H3, H1, 8.2ka and oscillations at 33-36ka BP), reflect transitions from peat (dominated by lignin from terrestrial plants) to lacustrine (MCCs from aquatic plants) conditions. The evidence points towards wet conditions causing the accumulation of layers rich in inorganic sediment during H events, favouring the hypothesis of a southward ITCZ shift, rather than an ENSO-induced northward shift, as the underlying mechanism. This contradicts previous studies using the "degree of peat humification" index (DPH). We measured DPH and the extracts and residues by PY-GC-MS, to better understand the validity of this surface moisture proxy. Paradoxically, high DPH corresponds to the relatively young (<15ka) ombrotrophic peat environment, as DPH relies on the proportion of extractable carbohydrates concentrated in this part of the core, while deeper and unarguably more evolved layers are comprised of alkali-inextricable lignin and MCCs. Therefore, DPH does not accurately reflect humidity-controlled degradation/preservation dynamics and its use for studying climate change in complex records, such as Lynch's Crater, is cautioned. Finally, the decoupling of humidity conditions from changes in regional arboreal vegetation supports the hypothesis of an anthropogenic- rather than climate-driven shift towards sclerophyllous vegetation since 45ka, but the hydroseral complexity of the system demands caution on this matter. © 2014 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/69207
Appears in Collections: 过去全球变化的重建
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作者单位: Instituto de Ciencias del Patrimonio (Incipit), Consejo Superior de Investigaciones Cienti´ficas (CSIC), San Roque 2, Santiago de Compostela, Spain; Departamento de Cieˆncia do Solo, Escola Superior de Agricultura Luiz de Queiroz (ESALQ), Universidade de Sa&tild;o Paulo, Av. Pa´dua Dias 11, caixa postal 9, Piracicaba (SP), Brazil; Department of Earth Sciences-Organic Geochemistry, Faculty of Geosciences, Utrecht University, P.O. Box 80021, Utrecht, Netherlands; Departamento de Edafoloxi´a e Qui´mica Agri´cola, Fac. Bioloxi´a, Universidade de Santiago de Compostela, Campus Sur, Santiago de Compostela, Spain; Department of Marine and Ecological Sciences, Florida Gulf, Coast UniversityFL, United States
Recommended Citation:
Kaal J.,Schellekens J.,Nierop K.G.J.,et al. Contribution of organic matter molecular proxies to interpretation of the last 55ka of the Lynch's Crater record (NE Australia)[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2014-01-01,414