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1.
A. V. Lozhkin P. M. Anderson T. V. Matrosova P. S. Minyuk 《Journal of Paleolimnology》2007,37(1):135-153
Three types of pollen assemblages (shrub-dominated, mixed herb- and shrub-dominated, and herb-dominated) characterize the
~ 300,000 year palynological record from El’gygytgyn Lake. Despite major changes in global climatic forcings, all pollen spectra,
with a few isolated exceptions, have strong to possible analogs in the modern plant communities of Northeast Siberia and Alaska.
Paleoclimatic reconstructions based on squared chord-distance analog analyses indicate two periods (~8600–10,700 14C year B.P. and OIS 5e) when summers were perhaps ~2 to 4°C warmer than modern. January temperatures were also warmer than
present, and both July and January were wetter than today. Palynological data remain inconclusive as to the establishment
of forests near El’gygytgyn Lake at these times. The wettest Julys occurred during OIS 5 d. July temperatures were near modern,
and Januarys were colder and drier than now. January temperatures, even into the Middle Pleistocene, generally show little
variability, suggesting that the suppression of arboreal taxa during glaciations was likely caused by cool summers with low
effective moisture and not by frigid winters. Because age schemes that correlate magnetic susceptibility to variations in
summer insolation or ∂18O have cool plant taxa persisting in warm times (and vice versa), we propose an alternative age model based on the palynological
data.
Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .
This is the first in a series of eleven papers published in this special issue dedicated to initial studies of El’gygytgyn Crater Lake and
its catchment in NE Russia. Julie Brigham-Grette, Martin Melles, Pavel Minyuk were guest editors of this special issue. 相似文献
2.
José Iriarte 《Quaternary Research》2006,65(1):20-32
This article presents a combined pollen and phytolith record of a 1.70-m sediment core from the wetlands of India Muerta (33° 42′ S, 53° 57′ W) in the lowland Pampa (grasslands) of southeastern Uruguay. Six 14C dates and the pollen and phytolith content of the samples permitted the recognition of four distinct climatic periods between 14,850 14C yr B.P. and the present. The Late Pleistocene period (between ca. 14,810 and ca. 10,000 14C yr B.P.) was characterized by drier and cooler conditions indicated by the presence of a C3-dominated grassland. These conditions prevailed until the onset of the warmer and more humid climate of the Holocene around 9450 14C yr B.P. The early Holocene (between around 10,000 and 6620 14C yr B.P.) was characterized by the establishment of wetlands in the region as evidenced by the formation of black peat, the increase in wetland taxa, and the replacement of C3 Pooideae by C4 Panicoideae grasses. During the mid-Holocene, around 6620 14C yr B.P., began a period of environmental change characterized by drier climatic conditions, which resulted in the expansion of halophytic communities in the flat, low-lying areas of the wetlands of India Muerta. About 4020 14C yr B.P. a massive spike of Amaranthaceae/Chenopodiaceae coupled with a radical drop in wetland species indicates another major and more severe period of dryness. After ca. 4000 14C yr B.P., a decrease of halophytic species indicates the onset of more humid and stable climatic conditions, which characterized the late Holocene.The findings reported in this article substantially improve our knowledge of the late Glacial and Holocene climate and vegetation in the region. The data provide a detailed record of the timing and severity of mid-Holocene environmental changes in southeastern South America. Significantly, the mid-Holocene drying trend coincided with major organizational changes in settlement, subsistence, and technology of the pre-Hispanic populations in the region, which gave rise to early Formative societies. This study also represents the first combined pollen and phytolith record for southeastern South America reinforcing the utility of phytoliths as significant indicators of long-term grassland dynamics. 相似文献
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根管石是高等植物的化石遗迹, 是陆地生态系统的敏感指示剂。根管石及其相关特征不仅证实了古土壤的存在并反映出古代陆地渗流环境的演化, 同时为研究古地理、古气候以及植物古生态提供了重要信息。近几十年来, 国际上对黄土-古土壤序列、海岸带和蒸发盐湖等环境中根管石的地球化学特征、成因和形成环境等已经进行了一系列研究并取得了一定的成果。本文总结了根管石的地球化学研究进展, 概括了不同环境中根管石的形态、矿物组成、碳氧同位素组成以及碳同位素定年等特征, 论述了根管石的形成过程及其对环境的指示意义。 相似文献
6.
Diverse palynomorphs and phytoliths recovered from coprolites of ovi-caprids (sheep, goat) collected from Yang-Hai Tomb at Xinjiang Province, China, have been used to elucidate the dietary pattern of ancient livestock and to reconstruct the paleovegetation and paleoclimate of this part of northwest China ca. 2500 14C yr BP. Palynological and phytolith data suggest that a rich dry temperate vegetation prevailed in the area during the said period. Climatic conditions and grassland vegetation type of the area are explored using phytolith indices. 相似文献
7.
本文通过对庆丰剖面的孢粉分析,得出了孢粉组合,恢复了建湖地区自晚更新世玉木亚间冰期以来的古植被及古气候,探讨了地层时代和晚第四纪环境变迁等问题。 相似文献
8.
上海西南部地区晚第四纪孢粉组合与古植被演替 总被引：4，自引：0，他引：4
通过对上海西南部地区几个钻孔的孢粉分析,建立了晚第四纪以来的10个孢粉带,反映了古植被演替和古气候波动的10个阶段,且进行了地层划分。根据孢粉分析和~(14)C测年资料,进一步证实上海地区全新世沉积之下的暗绿色硬粘土层是晚玉木冰期的沉积。 相似文献
9.
Fátima Franco-Múgica Mercedes García-Antón Javier Maldonado-Ruiz Carlos Morla-Juaristi Helios Sainz-Ollero 《Quaternary Research》2005,63(1):1-14
We present a new stratigraphic (pollen and nonpollen microfossils and charcoal particle) sequence with five AMS dates, covering about the last 9000 yr, of a core collected from the Spanish northern meseta, one of the territories of the Iberian Peninsula for which little paleobotanical information is available. The results support the hypothesis of the permanence of the pine forests, in more or less pure masses or large timber stands, during the Holocene in some Iberian continental zones. The typical substitution in postglacial dynamics of heliophyllous species, such as pines or Cupressaceae, by broadleaf trees did not occur in this inland region. Presumably, factors linked to the substrate, in this case very deep sand dunes covering vast areas, may have contributed to the scarce local competitiveness of the broadleaf trees, which would account for the hegemony of pines in this region. Based on the dynamics of aquatic plants and nonpollen microfossils, an initial phase previous to 7500 14C yr B.P. of high levels in the lake can be identified by high percentages of hydrophytes. A progressive increase in helophytes and the gradual infilling of the lake over the last 5000 yr appear to indicate a phase of aridification similar to those established for the western Mediterranean. Study of charcoal particles, more abundant in the last 2500 yr, has given rise to certain hypotheses regarding the incidence of recurring fires of a local or regional nature. 相似文献
10.
Aaron F. Diefendorf William P. Patterson Chris Holmden Henry T. Mullins 《Journal of Paleolimnology》2008,39(1):101-115
A 7.6-m lake sediment core from a marl lake, Lough Inchiquin, records variation in landscape evolution from 16,800 cal yrs
B.P. to 5,540 cal yrs B.P. We observe significant variations (up to 12‰) in δ
13Corg and δ
13Ccalcite values that are interpreted to reflect secular changes in lake water δ
13CDIC values that result from a regional landscape transition from barren limestone bedrock to a forested ecosystem. Lake water
δ
13CDIC values are therefore influenced by two isotopically distinct sources of carbon: terrestrial organic material (−27.1 to −31.2‰VPDB)
via oxidized soil organic matter and weathered limestone bedrock (+3.4‰VPDB). Isotope excursions in lacustrine sediment records
are forced not only by changes in productivity but also by changes in the terrestrial environment. This has profound implications
for the interpretation of paleoclimate records derived from lacustrine sediment and suggests that selection of appropriate
lakes can provide records of terrestrial change where other related records are not available. 相似文献