Buried palaeosols of the Nevado de Toluca: an alternative record of Late Quaternary environmental change in central Mexico

Buried palaeosols of central Mexico, not previously analysed from a palaeopedological standpoint, have helped to develop a reliable regional model of Late Quaternary climatic change. This paper focuses upon morphological and micromorphological properties, particle‐size distribution, and extractable Fe, Al and Si of seven palaeosols (named PT1–PT7) in the vicinity of the Nevado de Toluca volcano. The characteristics of Andic Cambisol PT1, similar to those of modern soils in semi‐arid environments, indicate a drier climate in the first half of the Holocene. Humic Andosols PT2–PT4 are analogous to modern volcanic soils of humid forest environments. They show evidence that a moist palaeoclimate prevailed during marine oxygen isotope stages (OIS) 2 and 3. Luvisols PT5 and PT6, which are assumed to have formed at the end of marine OIS 5 to marine OIS 4, also indicate humid conditions. We attribute the differences between Andosols PT2–PT4 and Luvisols PT5–PT7 to variations in the duration in the pedogenesis rather than to changes in palaeoclimate. Micromorphological features of Andosol to Luvisol transition confirm that these soils form an evolutionary sequence. Being for the most part consistent with lacustrine records, the palaeosol properties do not reflect the episodes of ‘drier climate’ during the Last Glacial Maximum, however, as shown by diatom and palynological data from lake sediments. Mesoclimate variations and/or incompleteness of ‘soil memory’, reflecting mostly periods of humid pedogenesis, probably provide the reason for this disagreement. Copyright © 2001 John Wiley & Sons, Ltd.     

绰墩农业遗址中存在中全新世水稻土的新证据*

前人研究认为,在长江下游地区绰墩农业遗址的全新世地层中存在2个古水稻土层,但到目前为止尚缺乏土壤化学和物理学方面的证据。为了寻找土壤学证据,在江苏省昆山市绰墩遗址P-01垂直剖面中连续采集了12个样品,分别测定了全氮(TN)含量、总有机碳 (TOC) 含量、粒度组成、质量磁化率以及粘土矿物组成。结果显示,从剖面底部(200cm)到100cm处和从57cm处到现代土壤表层,TOC,TN,TOC/TN比值、高岭石含量以及高岭石/伊利石(K/I)比值两次出现逐渐升高的趋势,而且它们的曲线形态基本一致。这些特点有可能说明P-01剖面中包含着两次成壤过程:第1次形成了古土壤层(160~100cm),第2次形成了现代水稻土(57cm~现代土壤表层)。但TOC和TN以及水稻植硅石资料不支持在深度57~42cm段存在古土壤的观点。从200cm到130cm处,磁化率和粘粒含量有逐渐降低的趋势,说明此处具有长期淹水的特征。现代水稻土的研究表明,水稻田排水过程中可能使部分粘粒被带走流失。因此,粘粒含量从200cm到130cm处逐渐降低的趋势可能与中全新世的人工排水有关。研究资料与考古学、孢粉学和植硅体资料共同说明,该古土壤层(160~100cm)很可能是古水稻土。古水稻土的确认将为农业考古和古环境变化研究提供有利的条件。     

内蒙古额尔古纳市虎拉林金矿区地电化学提取法寻找隐伏金矿研究

地电化学提取法是在动态平衡原理的基础上,利用人工电场提取深部的矿化或成矿离子,进行成矿预测,确定成矿靶区.为探明资源、节省投入,在虎拉林金矿区投入了以地电化学提取为主的找矿方法,来找寻矿区隐伏的矿体.通过对地电化学提取异常和其他方法异常的综合分析,确定在金矿区具有一定的找矿潜力,并证明了地电化学提取和其他方法在森林覆盖区寻找深部隐伏金矿床是可行的.     

新疆晚古生代气候征及影响的主要因素

根据已经取得的地质资料 ,如沉积特征 ,古地磁数据 ,火山活动 ,构造运动特点等 ,对影响新疆晚古生代气候的一些主要因素进行了初步探讨。     

冀中坳陷潜山油气运聚动力学特征及其类型

依据冀中坳陷潜山流体压力场、流体化学场及流体运移通道等特征的综合研究，将潜山分为三种运聚动力学类型：不整合连通－开放型潜山（Ⅰ）、断层通道－半开放／半封闭型潜山（Ⅱ型）和封闭型潜山（Ⅲ型）。Ⅰ型潜山与冀中坳陷中部区域性地下水动力系统相连通，油气源充足，可形成大规模的潜山油气藏。Ⅱ型潜山分布于紧邻生烃洼陷的斜坡区，潜山相关断层的地震泵（seismic pumping)通道作用促使油气运移与聚集，成藏条件较好。Ⅲ型潜山位于沉降幅度较大的洼陷区呈“孤立”分布，上覆第三系形成异常高压力带，抑制了潜山相关断层流体通道作用，潜山呈封闭系统，油气运聚条件较差，可能只能形成小型潜山油气藏，勘探风险大。     

利用岩芯沉积剩磁(DRM)确定隐伏地层产状

测量并分离出岩芯中的沉积剩磁,依据其在层面坐标系中的平均方向与岩石形成时的地磁场方向一致的原则,参照已发表的块体古地磁极移曲线(APWP)来计算赋存岩芯的隐伏地层产状,并给出了相应的计算方法及公式.     

中国古代木构建筑抗震机理及抗震加固效果的试验研究

为探究中国古代大木作(带有斗栱的木构建筑)结构抗震机理和抗震加固的有效方法，对缩尺比为1／3．52二等材宫殿当心间模型在同样条件下分别进行了模拟地震动的振动台试验研究，测试了模型结构加速度、速度和位移的动力时程响应；模型结构的自震频率和阻尼比。结果表明，古代大木作结构的抗震机理主要表现为两个方面：(i)因柱根滑移而隔震;(ii)斗栱以及普柏枋因弹塑性变形和摩擦滑移消耗掉大量地震能以致结构减轻了震害。     

深部砂土三轴高压卸载结构变化的CT研究

用取自山东巨野矿区埋深近 6 0 0m的深部砂土样,在三轴试验机上进行围压为 12MPa的三轴卸载试验,同时用CT装置探测试样在试验全过程中内部结构变化,并对纪录的CT图片进行了计算机图像分析处理,分析了深部砂土在高压卸载条件下变形和破坏结构性变化本质特点。     

Numerical study of the seismic behaviour of a part of the Parthenon Pronaos

A numerical study of the seismic behaviour of a proposed restoration of the Parthenon Pronaos is presented. The column‐architrave classical structure was represented by a discrete element model, with the assumption of rigid blocks and frictional joints. Time domain analyses were performed, considering the geometric and material non‐linear behaviour at the joints. The deformation and failure modes of drum columns subject to seismic excitations of various types and intensities were analysed. The adverse influence of drum imperfections on structural safety was examined. A proposal of reinforcement with titanium connections was analysed, and it was found that architrave connections generally improve the response by decreasing the permanent displacements, while titanium dowels between the column drums do not improve significantly the behaviour and in some cases they may be unfavourable to the safety of the structure. Copyright 2003 John Wiley & Sons, Ltd.     

徽州村落人居环境特征的初步研究

村落是我国广泛存在的一种人居环境类型。徽州由于受特殊的自然、社会条件和历史发展的影响，村落层面上的人居环境表现出与其它地域显著不同的特征，文章以徽州古村落为对象，对其选址、空间特征、形成机制及存在的合理性进行分析，旨在为徽州文化研究、现代人居环境建设的健康发展和古村落开发利用提供有益参考。