Grain size characteristics and environmental indication of the sediments around Great Wall Station,Antarctica

The Great Wall Station of China(62°13′S,58°58′W) is located at the Fildes Peninsula of King George Island,South Shetland Islands,Antarctica.Sediments in the area can be divided into glacial,periglacial,fluvial lacustrine and littoral deposits in origin.Analysis of the fine particals(below 3.52 mm) shows obviously difference among grain size composition,frequency curve,accumulative curve and scatter diagram.In order of periglacial glacial fluvial littoral deposit,sand increases,silt and clay decreases;sorting changes from poor to good;mean grain size is at very fine fine medium coarse sand respectively;skewness changes from very positive to near symmetric.Scatter diagram of grain size parameters shows difference in the sediments.Variation among frequency curves reflects processing and forming condition of the sediments.The fluvial and littoral deposits follow normal distribution,they are straight lines in normal accumulative diagram.The glacial and periglacial deposits follow Rosin's distribution,they are straight lines in Rosin's accumulative diagram.

Typhoon events recorded in coastal lagoon deposits,southeastern Hainan Island

Coastal lagoon deposits provide evidence for the magnitude and frequency of past tropical cyclones prior to instrumental records and historical documentation.In the present study,we attempt to analyze the sedimentary records containing typhoon information for the northern South China Sea region.For this purpose,sediment cores were collected from two coastal lagoons in the southeastern Hainan Island,and were analyzed in laboratory to derive the data sets about grain size,organic and inorganic carbon contents,and deposition rates.The grain size and organic-inorganic carbon data were used to formulate the proxies of typhoon events.The deposition rates,as calculated using the CRS 210 Pb method,are around 0.5 mm/a for both lagoons,on the basis of which an age model is established.Within the cores,sedimentary layers associated with 35 typhoon events have been identified.On such a basis,a 350 year history of local typhoon activities is reconstructed by incorporating the 210 Pb dating results,typhoon-induced sedimentation patterns and the historical documents.A comparison of the frequency of typhoon occurrence with the regional climate records indicates that the observed changes in tropical cyclone activity patterns,as revealed by the lagoon sedimentary records,may be related to El Ni？o,Pacific Decadal Oscillation（PDO）,North Atlantic Oscillation（NAO）,sunspot,and other potential climate drivers that affect the tropical cyclone variability.This study demonstrates that the sedimentary record of storms can be analyzed in combination with historical documents,to provide meaningful information on past storm activities and their long-term variability.

Intensification of the East Asian Monsoon in Southern China at about300-400 kaBP Inferred from Eolian Deposits in the Middle-lower Reaches of the Yangtze River

In the East Asian monsoon region, eolian deposits widely distributed in the middle-lower reaches of the Yantgze River are among the best materials available for studies on Quaternary climate change in the subtropical zone of Southern China. Typical eolian deposits in this region include upper Xiashu Loess （XL） and underlying Vermiculated Red Soil （VRS） layers. In this paper, chronological and paleoclimatic studies are conducted on an eolian deposit sequence near Jiujiang （J J） city in northern Jiangxi province. A magnetostratigraphic study, combined with optically stimulated luminescence （OSL） dating, is conducted on the JJ section and provides further evidence that eolian deposits in the middle-lower reaches of the Yangtze River have been formed since the late Early Pleistocene, and that the boundary age between the XL and VRS layers is about 300-400 kaBP. In grain-size records of the JJ section, the median grain-size and content of the 〉30μn size fraction increase sharply after 300-400 kaBP, representing an East Asian winter monsoon intensification event. Further pollen analysis reveals differing pollen assemblages before and after 300-400 kaBP： there is an evident increase in plants adapted to grow in a warm humid environment after 300-400 kaBP, implying an increase in precipitation caused by intensification of the East Asian summer monsoon. Global ice volume and uplift of the Tibet Plateau （TP） are regarded as crucial factors influencing variations of the East Asian monsoon on a long-term scale. The deep-sea JlSO record, which reflects variations in global ice volume, shows no obvious change after 300-400 kaBP. Moreover, the influence of global ice volume changes on the East Asian summer and winter monsoons is inverse; the global ice volume increase （decrease） implies a strengthened （weakened） winter monsoon and weakened （strengthened） summer monsoon. We therefore interpret the coupled intensifications of the East Asian summer and winter monsoons at about 300-400 kaBP to the uplift of the TP in the Middle Pleistocene. This climate event is also documented in eolian deposits from the southern margin of the Chinese Loess Plateau （CLP） and from the desert-loess transitional belt. However, it is not recorded in the loess-paleosol sequences from the central part of the CLP, thereby indicating differing climate responses to TP uplift in different regions, which requires further study.

The depositional Environment at Shuidonggou Locality 2 in Northwest China at ～72-18 kaBP

Shuidonggou site has abundant Paleolithic remains of Late Pleistocene deposition. Studying the evolution of depositional environments is essential to the comprehensive understanding of the living conditions of ancient populations. To reconstruct the depositional environment at Shuidonggou, we carried out archaeological excavations and collected systematic deposition samples at the key position of Shuidonggou Locality 2 for grain size analysis and sporopollen statistics. The environmental evolution around the Shuidonggou site generally underwent four stages at ~72-18 kaBP. During the first stage （~72-41 kaBP）, the river developed with gravel and sand stratums. During the second stage （41-34 kaBP）, a swamp with numerous aquatic plants formed. In the third stage （34-29 kaBP）, site formation was characterized by shallow lake depositional conditions; the climate was relatively warm and humid. The marginal bank depositional conditions deteriorated during the fourth stage （29-18 kaBP）, and the site underwent several dry events; the climate also became drier and colder.

On Physical and Mechanical Behavior of Natural Marine Intermediate Deposits

Coastal structures may be built on natural sedimentary intermediate grounds, which mainly consist of silty soils and fine sandy soils. In this study, extensive field and laboratory tests were performed on the natural marine intermediate deposits to demonstrate the difference in behavior between natural marine clayey soils and natural marine intermediate deposits. The natural intermediate deposits have almost the same ratios of natural water content to liquid limit as those of the soft natural marine clays, but the former have much higher in-situ strength and sensitivity than the latter. The research results indicate that grain size distributions of soils affect significantly tip resistance obtained in field cone penetration tests. The mechanical parameters of natural marine intermediate deposits are also significantly affected by sample disturbance due to their high sensitivity and relatively large permeability. Unconfined compression shear tests largely underestimate the strength of natural marine intermediate soils. The triaxial consolidated compression shear tests with simulated in-situ confined pressure give results much better than those of uncomfined compression shear tests.

激光熔化沉积Al-Mg-Sc-Zr合金晶粒尺寸预测及成形工艺优化

通过激光熔化沉积试验分析了工艺条件(送粉速度、扫描速度和激光功率)对Al-Mg-Sc-Zr合金晶粒尺寸的影响,构建了晶粒尺寸预测模型,优化了成形工艺参数,给出了工艺参数最佳区间。结果表明,相较于激光功率和扫描速度,送粉速度对晶粒尺寸的影响最为显著;随着成形能量密度的增加,合金晶粒尺寸呈现出先减小后增大的演变趋势;采用回归方程构建的晶粒尺寸-工艺参数关系模型能准确预测不同工艺条件下激光熔化沉积Al-Mg-Sc-Zr合金的平均晶粒尺寸,相对误差小于2%;通过响应面分析得到工艺参数最佳区间为:送粉速度2.8~3 g·min^(-1)、激光功率1000~1050 W、扫描速度4~5 mm·s^(-1)。

滇西南沧源岩溶洞穴硝洞堆积物来源分析

岩溶洞穴是第四纪时期古人类活动的重要场所。开展岩溶洞穴碎屑沉积物的沉积特征及物质来源分析,对其沉积环境演变历史及古人类活动研究都具有重要意义。本文在了解硝洞洞穴及其周围不同沉积物黏土矿物特征的基础上,结合硝洞洞穴沉积物的粒度和矿物学等特征对其物质来源进行了分析。结果表明:硝洞洞穴沉积物的主要来源为洞穴外地表较高处的沉积物,其通过片流作用被带入洞穴内进行堆积。其次,还同时堆积有少量灰岩不溶性物质及其经历进一步风化成壤作用后形成的物质,总体可能存在4次进一步的风化成壤作用。此外,也有洞壁崩塌的石灰岩角砾和岩块参与堆积,总体存在4次大量灰岩角砾或岩块参与堆积过程,而最近一次的堆积作用,显然受到了人类活动的影响。

不同计算方法的云南省永胜县下院滑坡堰塞湖沉积物粒度特征及沉积历史重建

【研究目的】滑坡堰塞湖灾害链危害大,其形成和溃决过程中受外部环境影响大。堰塞湖沉积物作为记录堰塞湖全生命周期的载体,具有良好的古环境和古气候的指示作用,采用最佳解析方法对其进行解读有利于还原沉积物沉积过程及古环境变化。【研究方法】通过野外调查采样和室内测试分析相结合的方法,采用图解法和矩值法计算下堰塞湖沉积物统计特征的适用性问题,使用粒度结合有机质含量重建了堰塞湖沉积环境,对堰塞湖的发育过程进行还原。【研究结果】(1)堰塞湖沉积物分层沉积层序明显,为单一水动力湖相沉积,物质来源稳定,非多物源沉积;综合有机质变化和沉积物粒度特征表明该堰塞湖经历了4次干湿周期,在气候和地质活动的共同作用下至少存在3次堵塞−泄流沉积过程,估算沉积旋回周期约为1750 a,该沉积历史应该是断裂带长期复杂的活动和气候−河流共同作用的结果。(2)通过对图解法和矩值法进行统计分析结果表明,两种方法对平均粒径和分选系数评价一致性较好,可直接进行替换;矩值法对偏态峰态整体计算结果比图解法大,在使用中需进行线性代换。由于描述参照值的缘故,偏态、峰态在统计表述中有所偏差。【结论】堰塞湖沉积物粒径分布简单,采用图解法计算更加便捷,与其他沉积物对比方便,推荐图解法对堰塞湖沉积进行计算。研究结果表明粒度特征对堰塞湖的沉积和溃决过程以及滑坡灾害对气候变化的响应研究具有一定的指导意义,可为还原该堰塞湖沉积期的古环境和古气候提供理论依据。

甘肃青土湖地区不同类型沙丘的表沙理化特征及其环境意义

沙丘表层沉积物的理化特征在揭示风沙的来源、沉积过程、风化作用等方面具有重要作用。本研究采用野外实地采样和实验室分析方法分析了甘肃青土湖地区不同类型沙丘表层沉积物的粒度和地球化学特征。结果表明:(1)青土湖地区沙丘表层沉积物以细砂为优势粒级,平均含量达72.08%,其次为极细砂,黏粒成分很少。频率分布曲线为单峰分布,概率累积曲线表现为三段式,反映出沉积环境较为稳定。(2)研究区沙丘表层沉积物常量元素以SiO2为主,平均含量为76.40%,其次为Al2O3和CaO,平均含量分别为5.05%、3.74%。微量元素以Cr、Mn、Co、Sr、Ba、Ti、Ce和P为主,平均含量均>100 mg/L。(3)Y、Zr和Y/Zr、Rb/Zr双变量图、A-CNK-FM图解表明巴丹吉林沙漠和腾格里沙漠为其沙源。风沙搬运过程中的磨蚀、风选作用是研究区富集Fe、Mg元素的主要原因。此外,下伏湖相沉积物就地起砂,石羊河冲积物也为其提供了部分沙物质。(4)A-CN-K和A-CNK-FM三角模式图表明研究区风化程度较弱,处于初期脱Na、Ca阶段。在沙丘固定过程中成土作用增强但淋溶作用减小,这是由于植被的影响导致半固定、固定沙丘Na、Ca含量较高。

新疆吾合沙鲁铜矿床含铜岩系安居安组下段砂岩粒度特征与沉积环境分析

吾合沙鲁铜矿床位于新疆西南天山乌恰前陆盆地北缘,该盆地内沉积大套中生代—新生代陆相砂体,是该区域铅锌、铜、铀等砂岩型矿床的重要含矿岩系。关于该矿床沉积学方面的研究工作薄弱,长期制约着对区域成矿规律的深入认识及对矿床勘查的有效指导。本文以吾合沙鲁铜矿床含铜岩系新近系中新统安居安组下段碎屑沉积岩为主要研究对象,以沉积学、层序地层学、岩相古地理学和碎屑岩石学理论为指导,系统采集矿区内安居安组下段砂岩粒度分析样品,采用碎屑岩粒度分析测试手段,对沉积物展开细致和深入的研究。结果表明,安居安组沉积相类型与辫状河三角洲相沉积特征一致,在各岩性段内识别出辫状河三角洲平原和辫状河三角洲前缘2种沉积亚相及分流河道砂坝、陆上天然堤、水下分流河道、分流间湾、河口砂坝及远砂坝6种沉积微相。安居安组下段为研究区主要富铜层位,其中水下分流河道微相和分流河道砂坝微相,可作为吾合沙鲁地区铜矿勘查的重点目标。研究成果可为吾合沙鲁铜矿周边及外围资源远景预测提供找矿思路,为区域探寻砂岩型铜矿提供新的借鉴。

Changes in grain-size and sedimentation rate of the Neogene Red Clay deposits along the Chinese Loess Plateau and implications for the palaeowind system

The wind system responsible for transporting dust onto the Chinese Loess Plateau during the late Miocene and Pliocene is still unknown and recent investigations highlight many controversies. This report aims to investigate spatiotemporal changes in grain-size and sedi- mentation rate of the Neogene Red Clay deposits in north China and to explore palaeoclimatic changes during the late Miocene and Pliocene, in particular the palaeowind system that trans- ported dust. Samples were collected from eight Red Clay sections on the Loess Plateau. Meas- urement and analysis show that there is a clear southward decrease in the mean grain-size index and in the coarse particle fraction (>20 μm). At Jiaxian site on the northern Loess Plateau, the average mean grain-size is around 20 μm, while at Lantian site in the south, the mean is around 9 μm. The coarse particle fraction >20 μm makes up 24.4% and 5.6%, at the two sites respec- tively. This distinct diversity of grain-size in the aeolian Red Clay deposit between the north and south indicate that the palaeodust was transported mainly by northerly low-level winds. The grain-size variations in the Red Clay deposits can also be divided into three stages (the lower, the middle and the upper interval): grain-size of the lower stage is significantly coarser than that of the middle stage, but finer than that of the upper stage. As a consequence, the intensity of pa- laeowind and desiccation of the dust source region during the late Miocene and Pliocene can be divided into three stages: 6.2―5.4 Ma, 5.4―3.5 Ma and 3.5―2.6 Ma. Strength of the palaeowind during the middle stage (5.4―3.5 Ma) is weaker than that of the previous and subsequent stages and the intensity of palaeowind during the latest stage (3.5―2.6 Ma) is stronger than that of the early time (6.2―5.4 Ma). Variations in the sedimentation rate of the Red Clay deposit can also be divided into three stages: the earlier, the middle and the later interval. The sedimentation rate of the earlier stage is higher than during the middle stage, but lower than during the later one. This is a clear indicator of changes in the palaeowind intensity and aridity in the dust source region and may be linked with global ice volume changes during the late Miocene and the Pliocene.

6061铝合金搅拌摩擦增材堆焊工艺研究

采用搅拌摩擦增材制造技术进行A6061铝合金表面堆焊工艺试验。采用光学显微镜和扫描电镜观察堆焊层的晶粒组织形貌,分析工艺参数对堆焊层形状尺寸和晶粒尺寸的影响,并进行拉伸性能测试。结果表明:在其他工艺参数不变的情况下,金属棒料的旋转速度为338 r/min,送料速率为440 mm/min,刀具底部与金属底板表面的间隙为2.8 mm时,热塑变材料在长度方向的堆焊铺展效率最高;堆焊层的晶粒尺寸随着送料速率逐渐增加,表现为先显著减小而后逐渐趋缓;堆焊层的晶粒尺寸随着金属棒料旋转速度增加而增加;堆焊层各区域中的晶粒尺寸大小排列顺序为:中心>上方>下方;堆焊层材料的抗拉强度和屈服强度均略高于锻件材料,两者的延伸率则基本相当,堆焊层拉伸断口为典型延性断裂形貌。

化学气相沉积SiC涂层的制备及水热腐蚀行为

采用化学气相沉积法在高纯石墨块上制备SiC涂层,并进行水热腐蚀实验,研究化学气相沉积工艺、涂层形貌结构与涂层水热腐蚀行为的关系。结果表明:随稀释氢气流量增大,涂层平均晶粒尺寸减小,涂层出现游离Si的可能性增大,其耐水热腐蚀性能逐渐降低;随沉积温度从1 000℃升高至1 300℃,涂层结晶度和平均晶粒尺寸都先增大后减小,在沉积温度为1 200℃时获得最大值,水热腐蚀后涂层结构和晶粒形貌保持完好;随三氯甲基硅烷水浴温度升高,涂层的平均晶粒尺寸增大,50℃水浴温度下制备的涂层结晶度最差且被腐蚀得最严重。

渤海湾曹妃甸海域沉积物粒度分布特征及运移趋势分析

对渤海湾曹妃甸海域161个表层沉积物样品进行了粒度组分和参数分析,利用Pejrup三角投图进行沉积动力环境分区,并运用GAO-COLLINS模型模拟沉积物输运趋势。结果显示,研究区表层沉积物类型包括砂、粉砂质砂、泥质砂、砂质粉砂、粉砂和黏土。粉砂分布范围最广,其次为粉砂质砂。粒度从东北向西南由粗变细,分选性逐渐变好。研究区东、西方向各有一个沉积中心,且二者沉积物输运趋势差异明显。东部海域沉积中心表现为北侧离岸输运,南侧向近岸输运,西侧向东输运;西部海域沉积中心表现为向西南、向西和向北输运。物源、地形地貌和水动力条件是物质输运的主要控制因素。结合周边工程环境因素、海底地形地貌、海流和地质背景等信息,在Pejrup三角图上,研究区沉积动力环境可划分成3个区,各区沉积动力强度与沉积物类型分布具有较好的对应关系。研究区物质运输主要受潮流、波浪和渤海湾环流控制。本研究揭示了曹妃甸南部海域现代沉积特征和水动力特征,可为曹妃甸围海造陆后海域沉积环境变化研究提供基础资料。

旋转速度对滚动摩擦沉积增材组织的影响

滚动摩擦沉积增材(Additive Friction Rolling Deposition,AFRD)是一种新兴的金属固态增材制造技术,特别适用于基于熔合增材制造方法易产生凝固缺陷的高强度铝合金。采用AFRD方法进行2024-O铝合金增材,获得全致密无缺陷的四层增材试件,利用金相显微镜、扫描电子显微镜对不同旋转速度增材试件宏观形貌、微观组织进行了表征。结果表明:(1)沉积层组织致密,无夹杂、裂纹等缺陷、相邻两沉积层之间形成良好的冶金结合。(2)沉积层呈现细小的轴晶粒组织,随着旋转速度升高,晶粒尺寸呈下降趋势。(3)沉积层第二相粒子呈现点片状分布于Al基体上,随着转速增大,第二相粒子趋向于细化与均匀。

基于钻孔记录探究古云梦泽沉积面貌

古云梦泽是晚全新世时期江汉平原与长江最主要的水沙交换载体,其形成演化特征为沉积物所记录,蕴藏了丰富的古环境、古气候信息。为了探讨古云梦泽沉积演化的规律和模式,基于2014~2019年江汉平原野外钻孔采样数据,对江汉平原钻孔沉积物的理化指标包括粒度、总有机碳、磁化率等进行分析,结合加速器质谱碳十四(AMS^(14)C)精准测年和粒度频率曲线得到晚全新世时期江汉平原整体的沉积环境变化序列,进而探讨古云梦泽沉积演化的规律和模式。结果表明:根据钻孔沉积相记录,古云梦泽形成演化过程中出现了“河流-湖泊-三角洲”复合沉积模式;钻孔横向对比发现,三角洲相沉积最先形成于江汉平原西部,并逐渐向东部扩展,表明这种复合沉积模式不仅仅只影响单个钻孔的沉积序列,还在空间上调控了整个古云梦泽的演化。研究成果揭示了历史时期全球变化背景下江汉平原河湖系统自然演变的特征与规律,对于指导江汉湖群的生态恢复和预测未来长江中下游地区江湖关系演变趋势具有重要的意义。

Al含量对激光沉积(CoCrFeNi)-Al高熵合金晶粒形貌的影响

激光沉积技术有望成为制备高熵合金的理想方法,但其制备的高熵合金易产生粗大柱状晶组织,限制了其在高熵合金制备中的广泛应用。利用激光沉积制备了(CoCrFeNi)1-xAlx(x=0,0.10,0.15,0.20)高熵合金,研究了不同Al含量下激光沉积(CoCrFeNi)1-xAlx高熵合金物相及晶粒形貌的演变规律,利用差热分析法对不同Al含量下高熵合金的凝固行为进行了分析。结果表明:随Al含量的增加,激光沉积(CoCrFeNi)1-xAlx高熵合金物相由面心立方(FCC)单相转变为FCC和体心立方(BCC)双相结构,不同Al含量下高熵合金中BCC相含量分别为3vol%(x=0.10)、24vol%(x=0.15)和52vol%(x=0.20);激光沉积高熵合金组织形貌也随Al含量增加由粗大柱状晶转变为细长晶粒,晶粒尺寸由116μm(x=0)显著降低至40μm(x=0.20)。这主要是由于Al含量的增加可降低(CoCrFeNi)1-xAlx高熵合金形核过冷度(ΔTN),并提高合金的生长限制因子(Q),从而产生更为显著的成分过冷,大幅促进了形核行为。

河北平原北部蓟州区西南头营剖面地层沉积特征与沉积环境研究

笔者等通过详细测量河北平原北部天津市蓟州区西南部桑梓镇头营剖面,结合粒度分析数据、孢粉分析数据、^(14)C和光释光测年数据,系统分析了该剖面地层形成年龄和沉积特征。实测剖面显示地层可以划分为18层,沉积物以黏土质粉砂、粉砂质黏土、黏土为主。^(14)C和光释光测年数据显示该剖面沉积物主要为晚更新世晚期以来沉积。粒度分析结果显示14个粒度样品频率分布曲线均为不对称的单峰态,表明沉积物成分单一,为相对稳定的水能条件下形成;概率累积曲线以细粒型为主,样品主要由跃移总体和悬浮总体组成。根据孢粉组合特征,可将剖面划分为3个孢粉带,孢粉带Ⅰ:气候温和湿润;孢粉带Ⅱ:气候寒冷干旱;孢粉带Ⅲ:气候温暖湿润。实测剖面测年结果与古里雅冰芯氧同位素曲线作对比可知,剖面形成时代对应MIS3~MIS1阶段,头营剖面经历了暖—冷—暖的气候变化,与孢粉组合反映的气候特征一致。综上可知,头营剖面晚更新世以来沉积物应属漫滩或洼地相沉积,整体处于相对稳定的低水流条件,沉积环境稳定。

海南岛东南部海湾350年古风暴事件沉积与历史文献记录对比

本项研究试图从沉积记录中分析古风暴事件的时间序列。以海南岛东南部黎安潟湖和新村潟湖钻孔沉积物为研究对象,选取沉积物粒度、有机质和碳酸盐含量等参数建立台风事件的鉴别指标,同时利用放射性核素210Pb计年确定沉积物柱状样的年代序列,对海南岛东南部的古风暴活动进行了分析。结果显示,柱状岩心的粒度指标、有机质和碳酸盐含量清晰地记录了海南省东南部过去350年期间的35次特大风暴潮事件,与历史文献资料对比良好。基于历史文献和沉积记录的风暴潮事件恢复了近350年来的风暴活动历史,发现海南省东南部特大风暴事件频数与厄尔尼诺强度有显著关系,同时还可能受到太平洋涛动和太阳黑子活动等多种因素的综合影响。恢复海岸带地区长时间尺度高分辨率的古风暴记录,为探讨全新世以来古风暴活动的气候响应机制提供了有效信息。

沙坡头铁路防护体系内风沙沉积的粒度特征

包兰铁路沙坡头段铁路防护体系内，由于下垫面性质发生变化，流沙区至人工植被带地表沉积物中表层土壤的黏粒和粉沙含量显著增大，平均粒径减小，颗粒分选性显著变差。防护体系内表层沉积物中的粉沙含量与地表相对高程反相关，黏粒含量与地形起伏没有直接关系，颗粒平均粒径、分选性与地表相对高程正相关。在土层垂直方向上，表层0-5cm内土壤粉沙含量较高，颗粒分选性差；5cm以下深度内土壤粉沙含量减少，颗粒分选性变好。在防护体系内沙丘地貌的不同部位，沙尘沉积速率不同。据此估算表明防护体系内固定沙丘迎风坡顶部沉积速率为0．147cm／a左右；背风坡和丘间地平均堆积速率大于0．588cm／a。