Terrestrial n-alkanes and their carbon isotope records from the Hanon paleo-maar sediment, Jeju Island, Korea: Implications for paleoclimate and paleovegetation over the last 35 kyrs
| Autor: | Seung-Il Nam, Sangmin Hyun, Kyung-Hoon Shin, Se Won Chang, Suk-Chang Lee |
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| Rok vydání: | 2017 |
| Předmět: |
Alkane
chemistry.chemical_classification Total organic carbon Hydrology 010506 paleontology N alkanes Isotope 010502 geochemistry & geophysics 01 natural sciences Maar chemistry Isotopes of carbon Environmental chemistry Paleoclimatology East Asian Monsoon Geology 0105 earth and related environmental sciences Earth-Surface Processes |
| Zdroj: | Quaternary International. 441:89-100 |
| ISSN: | 1040-6182 |
| Popis: | The carbon isotope of total carbon (δ 13 C org ), long-chain n -alkanes, and their compound-specific carbon isotope ratios (δ 13 C ALK ) were investigated in the Hanon paleo-maar sediment, Jeju Island of Korea to understand paleoclimate variabilities and their paleovegetation linkages. Based on the organic geochemical data (TOC (%), TN (%), and their δ 13 C org and δ 15 N), the core column stratigraphy was divided into three units, namely from the bottom to 14.5 ka (Unit I), from 14.5 ka to 3.0 ka (Unit II), and from 3.0 ka to the core top (Unit III), respectively. In particular, δ 13 C org showed marked fluctuation from −17.31‰ to −28.68‰, suggesting different organic carbon sources. A relatively narrow range of variation in δ 13 C org was observed in Unit III, and drastic changes in δ 13 C org were observed from Unit I to Unit II. This may indicate a predominance of C 4 plants in Unit I, and drastic changes from terrestrial C 4 to C 3 in Unit II and predominance of C 3 plants in Unit III. The distributions of n -alkane were characterized by a continuous predominance of odd-numbered n -alkanes, particularly n C 29 and n C 31 , and by high fluctuation of the total n -alkanes concentration. The average chain length (ACL), carbon preferences index (CPI), and paleo-plant proxy (P aq ) showed high fluctuation and glacial-interglacial variations with distinctive a high and low ratio at about 9.2 ka, corresponding to the switching points of δ 13 C org and a high concentration of n -alkane distribution. Individual n -alkane odd-numbered isotopes of δ 13 C ALK ranged between −11.80‰ in δ 13n C 21 and -34.93‰ in δ 13n C 31 , suggesting different sources of n -alkanes. The distribution of n -alkanes and their individual δ 13 C ALK , in particular δ 13n C 21 , support paleovegetation changes, and their time-dependent variations matched well with glacial-interglacial paleoclimate variations. Therefore, organic geochemical proxies recorded in Hanon paleo-maar sediment reflects paleoclimate variabilities as well as paleovegetation changes for the last 35 kyr in Jeju Island, Korea. |
| Databáze: | OpenAIRE |
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