Quaternary palynology of the Pacific slope of Washington

Quaternary deposits on the Pacific slope of Washington range in age from the earliest known interglaciation, the Alderton, through the Holocene. Pollen stratigraphy of these deposits is represented by 12 major pollen zones and is ostensibly continuous through Zone 8 over more than 47,000 radiocarbon yr. Before this, the stratigraphy is discontinuous and the chronology less certain. Environments over the time span of the deposits are reconstructed by the comparison of fossil and modern pollen assemblages and the use of relevant meteorological data. The Alderton Interglaciation is characterized by forests of Douglas fir (Pseudotsuga menziesii), alder (Alnus), and fir (Abies). During the next younger interglaciation, the Puyallup, forests were mostly of pine, apparently lodgepole (Pinus contorta), except midway in the interval when fir, western hemlock (Tsuga heterophylla), and Douglas fir temporarily replaced much of the pine. Vegetation outside the limits of Salmon Springs ice (>47,00034,000 yr BP) varied chiefly between park tundra and forests of western hemlock, spruce (Picea), and pine. The Salmon Springs nonglacial interval at the type locality records early park tundra followed by forests of pine and of fir. During the Olympia Interglaciation (34,00028,000 yr BP), pine invaded the Puget Lowland, whereas western hemlock and spruce became manifest on the Olympic Peninsula. Park tundra was widespread during the Fraser Glaciation (28,00010,000 yr BP) with pine becoming more important from about 15,000 to 10,000 yr BP. Holocene vegetation consisted first of open communities of Douglas fir and alder; later, closed forests succeeded, formed principally of western hemlock on the Olympic Peninsula and of western hemlock and Douglas fir in the Puget Lowland. Over the length of the reconstructed environmental record, climate shifted between cool and humid or relatively warm, semihumid forest types and cold, relatively dry tundra or park tundra types. During times of glaciation, average July temperatures are estimated to have been at least 7°C lower than today. Only during the Alderton Interglaciation and during the Holocene were temperatures higher for protracted periods that at present.     

Statistical techniques and their application in palynology

The basic principals of hypothesis testing are reviewed, including the development of the hypothesis, the statistical assumptions made, and the test of the hypothesis. The appropriate experimental design and sampling technique for evaluation of hypotheses posed are discussed. Because the analysis of variance involving the F-test should be used in a wide variety of geological experiments, emphasis is placed on this analysis. Many geological experiments result in the measurement of one or more factors on a continuous scale, whereas others are recorded in a discrete fashion. This necessitates the use of a covariance analysis to evaluate the effect of discrete and continuous factors in the same model. Orthogonal comparisons are discussed as they are used to evaluate specific hypotheses following the general test of hypothesis in the analysis of variance or covariance. All procedures discussed are illustrated using actual palynofloral data.     

An experimental approach to the palynology of cave deposits

Surface sediment, speleothems, and bat guano from two adjacent, topographically different cave sites in eastern Spain have been studied palynologically to elucidate the potential of cave sediments for palaeoenvironmental reconstruction. A cave opening with a large entrance and constant width presented far fewer problems of alteration in the pollen assemblages than a sac‐like cave opening with a constricted entrance. Pollen concentration is linked primarily to the amount of pollen input rather than to the result of post‐depositional alteration. Sampling should be undertaken away from parietal and rear areas and avoiding moisture zones. Lateral differences in the pollen spectra indicate that sampling should be on the basis of a multiple‐profile approach and selection of dry rather than wet sediments. If these procedures are followed, within‐cave sediments can realistically reflect not only local but also regional vegetation of the site. Copyright © 2000 John Wiley & Sons, Ltd.     

Mineralogy and palynology of the Mesopotamian plain sediments, Central Iraq

This work was done on the representative section (230 cm) in Dora site which located in Baghdad in the central of the Mesopotamian Plain. Eleven soil samples were examined mineralogically and palynologically. Grain size analyses showed that silt is the higher fraction (61%), clay is the least (9%), whereas sand forms 30%. Translucent and opaque heavy minerals contributed 57% from the sand fraction, whereas the light minerals formed just 43%. The type of heavy minerals and its maturity defined four provenances—they are granitic, basic igneous and metamorphic rocks—that belong to the high lands of south Turkey and north of Iraq. The fourth provenance is the sedimentary rocks which are located north of Mesopotamian Plain around the Tigris River and their tributaries. Dinoflagellate within thin bed of marine origin clearly indicated the transgression of the Arabian Sea northward through Tigris and Euphrates valleys or high marine waves reached to Baghdad before 10,000 years P.B. approximately. This means that the marine sediments were also an additional source of the Mesopotamian Plain. Three specific climatic features are identified via palynological interpretation; a temperate-wet climate extended from 10,000 to 5,000 years P.B. followed by dry period extended from 5,000 to 3,500 years P.B. and the last climatic feature is characterized by oscillation of wet to dry periods which is dominant since 3,500 till now.     

Stability of loess

Lutenegger, A.J. and Hallberg, G.R., 1988. Stability of loess. Eng. Geol., 25: 247–261.

The natural stability of loess soils can be related to fundamental geotechnical properties such as Atterberg limits, water content and void ratio. Field observations of unstable conditions in loess deposits in the upper midwest, U.S.A. show relationships between instability and the in situ moisture content and the liquidity index of the loess. Unstable loess can attain natural moisture contents equal to, or greater than, its liquid limit. Implications of these observations for applied engineering works are described.     

Quality, palynology, and palaeoenvironmental interpretation of the Ilgin lignite, Turkey

The Ilgin lignite field can be subdivided into the Haramiköy and Kurugöl areas which are separated by an area of basement and a fault. The lignite-bearing sequence consists mainly of fluvial and lacustrine Neogene deposits. The Ilgin lignite, averaging 8 m (up to 25 m) thick, is blackish brown and dark brown in colour. The lignite contains abundant brown wood, plant remains and white gastropod shells. Samples have an average of 38.9% moisture on an as-received basis and a mean of 3.9% total sulphur on an air-dried basis. Geochemical analysis, using an ICP-MS, was undertaken. Thirteen lignite core samples from three boreholes drilled in the Kurugöl area were ashed at 750°C. The average trace element contents of the lignite show a higher concentration of U (average 43 ppm) when compared to the range for most coals in the world, while the others (Ti, P, Sc, Be, Mn, Co, Cu, Zn, Ga, As, Rb, Sr, Zr, Nb, Mo, Cs, Ba, Y, Ta, W, Tl, Pb, Bi, Th, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu) agree with the global ranges. The Ilgin lignite is identified as of Middle Miocene (Middle Serravallian) age and occurs within lacustrine sediments deposited under subtropical climatic conditions.     

柴达木盆地一里坪凹陷新近纪孢粉特征及其古环境意义

柴达木盆地位于青藏高原北部,受高原隆升以及全球气候影响,新近纪盆地内古环境发生显著变化。通过对新近纪柴达木盆地一里坪凹陷孢粉特征进行分析,恢复盆地植被类型和环境演化过程,进而探讨高原构造隆升和全球气候变化对盆地古环境的影响。结果表明,一里坪凹陷新近纪孢粉组合以裸子植物繁盛,被子植物较为常见,旱生植物发育为主要特征。孢粉特征指示柴达木盆地一里坪凹陷整体新近纪属于半干旱—干旱气候,古环境演化受青藏高原隆升强度以及全球气候影响显著：下油砂山组环境为亚热带森林,上油砂山组环境为温带森林—草原,狮子沟组环境转变为寒温带草原—半荒漠。该时期环境背景,不利于一里坪凹陷在新近纪发育大规模优质烃源岩     

Lithology and palynology of Weichselian alluvial fan deposits near Eerbeek, The Netherlands

In a sandpit in an alluvial fan in the central Netherlands, four interstadials could be recognized. The upper two are ¹⁴C-dated and assigned to Hengelo and Moershoofd, while the lower two belong to either Odderade or Brorup. Lithological evidence suggested the existence of two zones indicative of permafrost separated by a zone in which running water was more important. The lower permafrost zone was found to be situated between the Moershoofd and Odderade interstadials, the younger zone to belong to the Upper Pleniglacial.     

Problems of loess chronology

Loess as a typically subaerial, loess deposit has long been regarded a Pleistocene sediment and its date of formation has been put to ca 600 ka BP. Recently, the beginning of the Pleistocene is identified in the official concord reached — at 1.6 Ma BP, while not infrequently others propose 2.4 Ma BP. Until the fifties the whole loess (loess-paleosol-sand) sequence could be referred into the shorter Pleistocene period, which —according to the climatic claendar by Milankovitch — consisted of nine cold and eight warm intervals. Some supporters of the longer Pleistocene chronology hold that the beginning of loess formation can be put as far back as 1.6 – 2.4 Ma BP. Loess formation intervals are usually correlated with the cold stages (nos 2, 4, 6 etc.) of the Emiliani oxygen isotope timescale, while soil formation is believed to correspond to the warm stages (nos 1, 3, 5, 7 etc.). The typical loess, i. e. loess proper, are not older than stage no 23 (Jaramillo event — 0.96 Ma BP). Previous to this date climatic conditions had not generally favoured loess formation and paleosols formed one above the other with clay, loam or carbonate intercalations.     

饱和黄土的性质与非饱和黄土流变模型

对西安地区相关数据统计分析，把西安市饱和黄土、软黄土的工程性质与一般黄土进行详细对比，指出它们之间的工程性质差异。同时重点介绍推导非饱和黄土加载体积流变模型过程以及模型的适用条件，对该模型的应用作了分析。     

柴达木盆地一里坪凹陷新近纪孢粉特征及其古环境意义

柴达木盆地位于青藏高原北部,受高原隆升以及全球气候影响,新近纪盆地内古环境发生显著变化。通过对新近纪柴达木盆地一里坪凹陷孢粉特征进行分析,恢复盆地植被类型和环境演化过程,进而探讨高原构造隆升和全球气候变化对盆地古环境的影响。结果表明,一里坪凹陷新近纪孢粉组合以裸子植物繁盛,被子植物较为常见,旱生植物发育为主要特征。孢粉特征指示柴达木盆地一里坪凹陷整体新近纪属于半干旱—干旱气候,古环境演化受青藏高原隆升强度以及全球气候影响显著：下油砂山组环境为亚热带森林,上油砂山组环境为温带森林—草原,狮子沟组环境转变为寒温带草原—半荒漠。该时期环境背景,不利于一里坪凹陷在新近纪发育大规模优质烃源岩     

Stratigraphy,palynology and geochemistry of the Lower Eocene coals of Arauco,Chile

The Arauco Sedimentary basin of Chile (37° −37° 45′S, 73° 08′ −73° 41′W) contains the most important reserves of bituminous coals of Chile. These are concentrated in two Formations: Curanilahue (Lower Eocene) and Trihueco (Middle Eocene). Five coal seams from the Lota Member of the Curanilahue Formation have been studied from the stratigraphic, palynologic and geochemical point of view. These coals were formed during a regressive stratigraphic episode; the palynological assemblage indicates that the climatic conditions prevailing at the time were of high humidity and temperature. These coals from a geochemical point of view are characterized by high sulphur (2.02%), ash (11.9%) and Ge (67.5 ppm; 1224.3 ppm in ash).     

Non-classical types of loess

The purpose of this contribution is to describe the sequence of physical and chemical processes resulting in the sediment-type named loess, a fine-grained sediment deposit of universal occurrence. Owing to historical causes, loess has been (and still is) implicitly linked to glacial/periglacial environments among most naturalists. However it is known today that most eolian dust is deflated from tropical deserts. Hence, that sequence of processes is more comprehensive than the former narrow cold scenario. Six examples of different “non-classical” cases (from South America and Europe) that fit well to the loess definition are developed: 1) volcanic loess in Ecuador: pyroclastic eruptions/valley wind/mountain praire/silica structuring; 2) tropical loess in northeastern Argentina, Brazil and Uruguay: deflation of river and fan splays/savanna/iron sesquioxide structuring; 3) gypsum loess in northern Spain: destruction of anhydrite/gypsiferous layers in a dry climate/valley wind/Saharian shrub peridesert/gypsum structuring; 4) trade-wind deposits in Venezuela and Brazil: deflation in tidal flats/trade wind into the continent/savanna/iron hydroxide structuring; 5) anticyclonic gray loess in Argentina: continental anticyclone on plains/anti-clockwise winds and whirls/steppe/carbonate structuring. All these non-classical types conform to the accepted loess definitions and they also share the most important field characteristics of loess such as grain size, friability, vertical or sub-vertical slopes in outcrops, subfusion and others. Other cases can probably be recognized when systematically scrutinized.     

黄土地区挤密桩桩周土体挤密模型的确定

研究分析了邓肯-张模型在挤密桩周土体应用中的不足。通过室内试验及对黄土地区挤土桩成孔对桩周土挤密原理的分析,认为桩周挤密黄土变形模量在破坏前符合邓肯-张模型,破坏后可用重塑土室内压缩试验的压缩模量与建议的转换系数? 确定,并进一步给出了相应的计算模式,提出了黄土成孔挤密模型并通过一个实例验证了模型的合理性。此模型为以后对桩周土体的应力分析打下了良好的基础,对进一步完善挤密桩设计理论具有参考价值。     

黄土微结构的试验研究

本文通过电镜扫描分析手段,对Q3黄土试验场地土样微结构特征的各项指标进行了比较和分析,旨在找出其规律性。同时,本文还介绍了黄土微结构的研究方法和要求。结合室内实验,对所获得的一系列黄土特性量化指标进行了分析对比,揭示了微结构与黄土液化之间的内在联系。研究结果表明,由统计值变异系数,能达到对黄土场地液化势起到相当程度确定性的目的,验证了利用微结构研究黄土结构变化的可行性。     

The loess of West Europe

During the last thirthy years, many studies about loess and periglacial deposits have allowed to present a correlation table from the Netherlands and Belgium to north-west France. For the Quaternary, 11 main interglacial soils were recognized, separated during Early Pleistocene by combe-rock and solifluction deposits, and during Middle and Late Pleistocene by loess cycles. Two main loess basins exist in France. The most important is the Northern basin, continuing the sandy area of Belgium (cover sand) and the desert pavement of the Netherlands. The second is developed in Normandy and results from the Channel landscape open during pleniglacial periods. We have now stratigraphic tables at different time-scales. The main research axes must be now to attain a better knowledge about sources of loess materials, to estimate the volume of loess and its climatic significance and landscape variation during the pleniglacial events. Absolute datings of Middle Pleistocene stratigraphic details are needed to evaluate the differences between the different climatic cycles.     

入渗诱发黄土滑坡的力学机制

在农田水利建设蓬勃发展的同时,灌溉入渗在黄土塬边诱发了严重的滑坡灾害。作为黄土滑坡的典型区域,甘肃黑方台地区近年来受到了密切关注。为了研究入渗条件下黄土边坡的变形破坏机制,在黑方台典型滑坡后壁削取原状土样,开展了3组不同应力路径的三轴试验以模拟边坡的失稳过程。通过开展偏压固结不排水（ACU）试验和饱和恒载（SDL）增孔压试验研究了饱和黄土启动和变形破坏过程;通过开展非饱和恒载（UDL）增湿试验,研究了非饱和黄土启动和变形破坏过程。在此基础上,从应力路径和黄土的微观结构角度阐述了入渗诱发黄土滑坡的力学机制。此外,利用试验结果分析了黄土的典型物理力学特性,结果表明：在埋深应力范围内,该黄土的饱和临界状态线可简化为单一的直线;该黄土的状态边界线可近似为其临界状态线;由UDL试验预测的土-水特征曲线受应力状态影响,较高的应力水平对应较低含水率。