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31.
The early Eocene is a period with very high atmospheric CO_2 levels, which receives many interests from climate modelling aspects. To simulate the early Eocene paleoclimate, a realistic reconstruction for land-sea distribution, paleotopography and paleobathymetry is the fundamental step. Here, we present global paleogeographic reconstructions for the early Eocene(～55 Ma), based on integrated paleogeographic data set, the plate-tectonic reconstruction software(GPlates) and geographic information system software(ArcGIS). Comparing with previous paleogeographic reconstructions, we improve the reconstructions by incorporating many recent geologic data and data set, including:(1) Better representations of the Tethys Sea,some marginal or inland seas in the East and Southeast Asia, Atlantic and Arctic region, and the Drake Passage and Tasmanian Gateway;(2) integrated paleoelevation data of global high plateaus and mountains, especially the paleotopography of East Asia,and adopting the latest paleotopographic reconstruction data of the Antarctica; and(3) using the latest data set of oceanic crust paleo-age and oceanic sediment thickness to reconstruct the paleobathymetry. 相似文献
32.
Quaternary strata in China mainly comprise continental deposits in a variety of depositional settings. The continental Quaternary in temperate northern China consists mainly of eolian and fluvio-lacustrine deposits; that in subtropical southern China, mainly of vermiculated red soils, cave/fissure deposits, and fluvio-lacustrine deposits; and that in the alpine Tibetan Plateau, mainly of fluvio-lacustrine and piedmont deposits. The marine Quaternary in China consists of detrital deposits and biogenic reef deposits. The integration of biostratigraphy, magnetostratigraphy, climatostratigraphy and an astronomically calibrated chronology has led to the establishment of high-precision climatochronostratigraphic timescales for the detrital marine Quaternary in the South China Sea and the loess-paleosol sequence in the Chinese Loess Plateau. Extremely high-precision230 Th dating has provided a high-precision absolute age model for cave stalagmites over the past 640000 years as well as highresolution oxygen isotope records representing orbital-to suborbital-scale climate changes. By combining magnetic stratigraphy and biostratigraphy, robust chronostratigraphic frameworks for non-eolian continental Quaternary deposits on the scale of Quaternary geomagnetic polarities have been established. The continental Pleistocene Series consists, from oldest to youngest,of the Nihewanian Stage of the Lower Pleistocene, the Zhoukoudianian Stage of the Middle Pleistocene, and the Salawusuan Stage of the Upper Pleistocene. Stages of the continental Holocene Series have not yet been established. This review summarizes recent developments in the Quaternary chronostratigraphy of representative Quaternary strata and associated faunas, and then proposes an integrative chronostratigraphic framework and a stratigraphic correlation scheme for Quaternary continental strata in China. In the near-future, it is hoped to establish not only a Chinese continental Quaternary climatochronostratigraphic chart on the scale of glacial-interglacial cycles but also a Quaternary integrative chronostratigraphic chart including both continental and marine strata in China. 相似文献
33.
风尘堆积全岩和石英粒度变化对风化成壤强度的指示 总被引：1，自引：1，他引：0
已有研究表明,黄土中的石英组分在黄土区的气候条件下基本不受风化作用的影响.文章对西峰剖面新近纪风成三趾马红土和第四纪黄土-古土壤序列样品进行全岩和石英粒度测试,并计算了不同风化成壤强度样品的全岩-石英粒度中值粒径差值.结果显示,与石英粒度相比,全岩样品含有更多的细粒组分,表明全岩粒度是风尘原始粒度与后期风化成壤作用共同的产物.根据此原理,用二者中值粒径差值定义一个风化指数(Gw),风化强度愈强,Gw愈大,可作为反映风化成壤强度的有效指标.该指标在西峰剖面6.2Ma以来风成堆积序列的应用显示,晚中新世-上新世期间风化强度较强,第四纪以来风化强度呈总体减弱趋势,其趋势与不断增大的全球冰量和粉尘沉积速率相吻合.我们认为,全球变冷和亚洲内陆干旱化程度的加剧是导致风化成壤强度降低的主要原因. 相似文献
34.
李希霍芬是19世纪德国著名的地质学家,对欧洲和中国黄土的研究工作,以及后来的黄土研究有着深刻影响,其学术思想在地球系统科学研究的时代依然有重要的现实意义。文章简要回顾了李希霍芬对黄土研究的贡献,并探讨这些贡献与黄土研究在地球系统科学研究中的现实意义。从李希霍芬时代到今天,黄土作为全球宝贵的地球系统演化的历史记录,在揭示地球岩石圈、水圈、大气圈、冰冻圈、生物圈及宇宙事件对地球系统的影响发挥了重要作用,并在未来地球系统科学研究时代有旺盛的生命力。 相似文献
35.
Science China Earth Sciences - The Chinese government has made a strategic decision to reach ‘carbon neutrality’ before 2060. China’s terrestrial ecosystem carbon sink is... 相似文献
36.
过去典型增温时段的自然植被演化规律是未来增温情形下植被变化趋势的重要参照.黄土高原全新世中期(4 ～8kaB.P.)和末次间冰期(80 ～110kaB.P.)温度分别比现高约1.2℃和2～5℃,是揭示过去不同增温幅度下植被演化的理想时段.通过对黄土高原东西部黄土-古土壤序列有机碳同位素(δ13Corg.)对比研究表明:在全新世中期黄土高原东西部有机碳同位素变化一致,相对末次盛冰期表现为正偏2.2‰～2.9‰,指示C4植物丰度增加.而在末次间冰期黄土高原东、西部不同地貌单元有机碳同位素结果产生空间分异,相对末次盛冰期西部梁峁区表现为负偏约0.8‰,指示C4植物丰度减少,而东部塬区则表现为正偏0.9‰ ～4.0‰,指示C4植物丰度增加.由于上述典型时段大气CO2浓度相近且温度升高,末次间冰期与全新世中期黄土高原C4植物丰度变化的差异可能与降水增加的季节性变化有关.上述结果表明,在过去典型增温期不同增温幅度下黄土高原东、西部不同地貌单元植被演化呈现明显不同. 相似文献
37.
In order to improve the reliability of climate reconstruction, especially the climatologies outside the modern observed climate
space, an improved inverse vegetation model using a recent version of BIOME4 has been designed to quantitatively reconstruct
past climates, based on pollen biome scores from the BIOME6000 project. The method has been validated with surface pollen
spectra from Eurasia and Africa, and applied to palaeoclimate reconstruction. At 6 cal ka BP (calendar years), the climate
was generally wetter than today in southern Europe and northern Africa, especially in the summer. Winter temperatures were
higher (1–5°C) than present in southern Scandinavia, northeastern Europe, and southern Africa, but cooler in southern Eurasia
and in tropical Africa, especially in Mediterranean regions. Summer temperatures were generally higher than today in most
of Eurasia and Africa, with a significant warming from ∼3 to 5°C over northwestern and southern Europe, southern Africa, and
eastern Africa. In contrast, summers were 1–3°C cooler than present in the Mediterranean lowlands and in a band from the eastern
Black Sea to Siberia. At 21 cal ka BP, a marked hydrological change can be seen in the tropical zone, where annual precipitation
was ∼200–1,000 mm/year lower than today in equatorial East Africa compared to the present. A robust inverse relationship is
shown between precipitation change and elevation in Africa. This relationship indicates that precipitation likely had an important
role in controlling equilibrium-line altitudes (ELA) changes in the tropics during the LGM period. In Eurasia, hydrological
decreases follow a longitudinal gradient from Europe to Siberia. Winter temperatures were ∼10–17°C lower than today in Eurasia
with a more significant decrease in northern regions. In Africa, winter temperature was ∼10–15°C lower than present in the
south, while it was only reduced by ∼0–3°C in the tropical zone. Comparison of palaeoclimate reconstructions using LGM and
modern CO2 concentrations reveals that the effect of CO2 on pollen-based LGM reconstructions differs by vegetation type. Reconstructions for pollen sites in steppic vegetation in
Europe show warmer winter temperatures under LGM CO2 concentrations than under modern concentrations, and reconstructions for sites in xerophytic woods/scrub in tropical high
altitude regions of Africa are wetter for LGM CO2 concentrations than for modern concentrations, because our reconstructions account for decreased plant water use efficiency. 相似文献
38.
本文首先对玉龙山东麓不同海拔高度现代表土样品有机碳同位素组成进行研究,探讨土壤碳同位素组成与海拔高度的关系,然后对0.5～0.7MaB.P.以来3期古土壤样品的有机碳同位素组成进行了测定.结果表明,现代表土的有机碳同位素组成与海拔高度之间存在良好的相关性,应是植被随海拔高度变化的反映;不同年龄的古土壤虽然目前均出露于地表,但其深部碳同位素组成存在显著差异,表明古土壤有机质中仍可能包含了过去植被的信息.根据上述结果对青藏高原0.5～0.7MaB.P.以来的隆升幅度进行尝试性估算,得到的隆升幅度约为800m.这个结果与我们过去根据古土壤的估算是基本一致的. 相似文献
39.
当前国际古全球变化研究的主要科学问题和任务——极地—赤道—极地大断面 总被引：2，自引：0，他引：2
国际地圈－生物圈计划（ＩＧＢＰ）是当前地学领域最重要的科学活动之一，其核心项目“古全球变化（ＰＡＧＥＳ）”的主要目标是研究过去的全球变化问题。而ＰＡＮＡＳＨ计划（南北半球古气候计划）是当前ＰＡＧＥＳ活动的焦点。其主要目标是通过三个ＰＥＰ（极地—赤道—极地）大断面，建立气候变化的序列和相位关系。文章对ＰＡＮＡＳＨ及其三个ＰＥＰ项目的主要科学目标和科学问题进行介绍，并对它们共同的科学问题进行分析。我国是ＰＥＰ－Ⅱ断面的重要组成部分，在该方面研究的程度直接关系到整个ＰＥＰ－Ⅱ的工作。组织好该方面的研究是我们重要的国际科学责任和义务。 相似文献
40.
文章对位于渤海湾西岸黄骅坳陷内的BZ1钻孔进行了详细的磁性地层学研究。结果表明,204.51m的岩芯记录了布容正向极性时(Brunhes)、贾拉米洛(Jaramillo)和奥尔都维(Olduvai)极性亚时,钻孔底部年龄约为2.21Ma。本项研究结果为该区约2.21Ma以来的古环境和相关研究提供了可靠的地层年代框架。与沧县隆起区的BZ2钻孔地层结果对比表明,两个构造单元的沉积物厚度在布容期以来差异较大,即在此期间黄骅坳陷相对沧县隆起下沉40余米,表明1Ma前后发生的新构造运动导致黄骅坳陷区构造下沉速率显著增加。 相似文献