过去 2.3 万年间北非的水文和植被变化:利用遥感技术和来自东地中海的特定化合物 δ2H 和 δ13C 对尼罗河流域进行的比较研究

IF 1.9 3区 地球科学 Q3 GEOGRAPHY, PHYSICAL
KHALED S. Sinoussy, Hiroshi Naraoka, Osamu Seki, MAHMOUD A. Hassaan, Yusuke Okazaki
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引用次数: 0

摘要

根据地中海东部 ODP 967 号站点沉积物中的正烷烃及其碳同位素比值(δ13Cn-烷烃)和氢同位素比值(δ2Hn-烷烃),重建了非洲东北部尼罗河流域地区自末次冰期极盛时期(LGM)以来的水文气候变迁和植被变化。利用 ArcGIS 将研究结果与流域地区目前的植被覆盖情况进行了比较。赤道湖和埃塞俄比亚高原流域地区目前草地的平均比例分别为 45.8% 和 64.7%。δ2Hn-烷烃的范围为-199至-127‰,与日照变化对轨道强迫的响应共同变化。从脱冰期到全新世中期,δ2Hn-烷烃含量减少,这表明非洲湿润期(AHP)(15-5 ka)降水量增加,原因是热带辐合带北移。然而,根据富集的δ2Hn-烷烃推断,在远古至全新世晚期降水量较少。967 号站点的δ13Cn-烷烃与δ2Hn-烷烃的变化趋势并不一致,而是呈现出-25.9‰至-33.2‰的千年尺度变化。这些δ13Cn-烷烃值一致表明,尼罗河流域地区自远古至近代一直处于以 C4 禾本科植物为主的环境中,并一直持续到远古至近代。重建结果表明,在第四纪晚期,水文气候变异受到轨道和突变的影响,而植被则普遍以草为主,降水反馈较弱。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Hydrological and vegetation changes in North Africa over the past 23 000 years: a comparative study of watershed areas of the Nile River using remote sensing and compound-specific δ2H and δ13C from the Eastern Mediterranean Sea

Hydroclimate variation and vegetation changes of the Nile River watershed area in northeast Africa since the Last Glacial Maximum (LGM) were reconstructed based on n-alkanes, their carbon isotope ratios (δ13Cn-alkanes), and their hydrogen isotope ratios (δ2Hn-alkanes) in sediments from ODP Site 967 in the Eastern Mediterranean Sea. The results were compared with the present vegetation cover in the watershed areas using ArcGIS. The average proportion of current grassland in the Equatorial Lake and Ethiopian Highland Plateaus watershed areas was 45.8 and 64.7%, respectively. δ2Hn-alkanes ranged from −199 to −127‰ and co-varied with insolation change response to orbital forcing. Depleted δ2Hn-alkanes were found from deglaciation to the middle Holocene, suggesting increased precipitation during the African Humid Period (AHP) from 15 to 5 ka caused by northward migration of the Intertropical Convergence Zone. However, lower precipitation was inferred by enriched δ2Hn-alkanes during the LGM and late Holocene. δ13Cn-alkanes at Site 967 did not show a trend in harmony with δ2Hn-alkanes and instead exhibited millennial-scale variations ranging from –25.9 to –33.2‰. These δ13Cn-alkanes values consistently indicated a C4 grass-dominated environment in the watershed areas of the River Nile since the LGM, persisting through the AHP and into the present. Reconstructions demonstrated orbital and abrupt forcing of hydroclimate variability while maintaining generally grass-dominated vegetation with weak precipitation feedback over the late Quaternary.

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来源期刊
Journal of Quaternary Science
Journal of Quaternary Science 地学-地球科学综合
CiteScore
4.70
自引率
8.70%
发文量
82
审稿时长
6-12 weeks
期刊介绍: The Journal of Quaternary Science publishes original papers on any field of Quaternary research, and aims to promote a wider appreciation and deeper understanding of the earth''s history during the last 2.58 million years. Papers from a wide range of disciplines appear in JQS including, for example, Archaeology, Botany, Climatology, Geochemistry, Geochronology, Geology, Geomorphology, Geophysics, Glaciology, Limnology, Oceanography, Palaeoceanography, Palaeoclimatology, Palaeoecology, Palaeontology, Soil Science and Zoology. The journal particularly welcomes papers reporting the results of interdisciplinary or multidisciplinary research which are of wide international interest to Quaternary scientists. Short communications and correspondence relating to views and information contained in JQS may also be considered for publication.
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