基于南部非洲湿地的年代地层古气候分期:从悬崖到东海岸

IF 1.2 4区 地球科学 Q2 GEOLOGY
E. Norström, M. Kylander, S. R. Sitoe, J. Finch
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引用次数: 1

摘要

本文旨在根据南非东部和莱索托山区和沿海湿地的替代指示,确定年代地层古气候边界。阶段边界是根据代理推断的气候变化时间以及气候变化的制度变化来确定的。有时还考虑了变化的幅度和/或频率。总结常见的古气候指示,可得出以下年代地层气候阶段:25至18ka、18至15ka、15至11.5、11.5至8ka、8至5.5ka、5.5至2ka和2至0ka。在18 ka、15 ka和2 ka确定了最稳健的边界,即这些边界得到了几个代理/站点的支持。从可用的代理/站点中检测到的其他边界不太清楚,应视为暂定边界。气候变化的时间往往与海岸和山区重合。然而,每个年代地层阶段的气候条件有时在海岸和内陆地区有所不同。25至18卡的阶段是凉爽干燥的,有强烈而频繁的风暴,其次是约18至15卡的阶段,当时的情况不那么严重,但总体上仍然凉爽干燥。在约15至11.5卡的温度下,几个指标推断气候变暖,冬季降雨量减少。在11.5至8 ka期间,湿度普遍增加,随后在8至5.5 ka期间升温。在5.5和2ka之间,表明了向更湿润的连续变化,尽管不同地点的时间不同。在2 ka之后,通常会出现更多变的气候,通常在干旱和潮湿之间有很高的幅度变化。数据分辨率,即可用湿地记录的数量,随着时间的推移而增加,从冰川时期的极低分辨率增加到全新世晚期的最高分辨率。从地理位置来看,与沿海地区相比,山区的遗址代表性过高。与沿海湖泊记录的比较表明,在全新世中后期,与山区相比,沿海地区的气候变化更大,尽管不能排除不同的代理分辨率和方法作为解释。一项案例研究比较了Drakensberg(Sekhokong,Ntsikeni)和海岸(Mfabeni)的多代理记录,讨论了站点内部和站点之间代理比较的优势和问题。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Chronostratigraphic palaeo-climate phasing based on southern African wetlands: From the escarpment to the eastern seaboard
This paper aims to identify chronostratigraphic palaeo-climatic boundaries based on proxy indications from mountain- and coastal wetlands in eastern South Africa and Lesotho. Phase boundaries were identified from timing of climate change inferred by proxies, as well as regime shifts in climate variability. Sometimes magnitude and/or frequency of change was also considered. Summarizing the common palaeo-climatic indications suggest the following chronostratigraphic climate phases: 25 to 18 ka, 18 to 15 ka, 15 to 11.5, 11.5 to 8 ka, 8 to 5.5 ka, 5.5 to 2 ka and 2 to 0 ka. The most robust boundaries were identified at 18 ka, 15 ka and 2 ka, i.e. these boundaries were supported by several proxies/sites. The other boundaries were less clearly detected from available proxies/sites and should be regarded tentative. The timing of a climate shift often coincides at coast and mountain sites. However, the climate conditions within each chronostratigraphic phase sometimes vary between coast and inland sites. The 25 to 18 ka phase was cool and dry with strong and frequent storms, followed by the ca. 18 to 15 ka period when conditions were less severe but still generally cool and dry. At ca. 15 to 11.5 ka several proxies infer warmer climate, with less winter rains. During 11.5 to 8 ka a general increase in wetness is inferred, followed by warming over the 8 to 5.5 ka phase. Between 5.5 and 2 ka a successive change towards wetter is indicated, although timing differ between sites. After 2 ka generally a more variable climate is seen, often with high magnitude shifts between dry and wet. The data resolution, i.e. the number of available wetland records, increases with time from very low during glacial times, to highest resolution during late Holocene. Geographically, sites in the mountain region are overrepresented compared to coastal sites. A comparison with coastal lake records suggests a more variable climate at coastal sites compared to mountain sites during mid- and late Holocene, although different proxy resolution and methodology cannot be ruled out as an explanation. A case study compares multiproxy records from Drakensberg (Sekhokong, Ntsikeni) and the coast (Mfabeni), discussing advantages and problems associated with proxy-comparisons within and between sites.
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来源期刊
CiteScore
3.60
自引率
5.60%
发文量
18
审稿时长
>12 weeks
期刊介绍: The South African Journal of Geology publishes scientific papers, notes, stratigraphic descriptions and discussions in the broadly defined fields of geoscience that are related directly or indirectly to the geology of Africa. Contributions relevant to former supercontinental entities such as Gondwana and Rodinia are also welcome as are topical studies on any geoscience-related discipline. Review papers are welcome as long as they represent original, new syntheses. Special issues are also encouraged but terms for these must be negotiated with the Editors.
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