Holocene alpine glaciation inferred from lacustrine sediments on northeastern Baffin Island,Arctic Canada

With accelerated melting of alpine glaciers, understanding the future state of the cryosphere is critical. Because the observational record of glacier response to climate change is short, palaeo‐records of glacier change are needed. Using proglacial lake sediments, which contain continuous and datable records of past glacier activity, we investigate Holocene glacier fluctuations on northeastern Baffin Island. Basal radiocarbon ages from three lakes constrain Laurentide Ice Sheet retreat by ca. 10.5 ka. High sedimentation rates (0.03 cm a^?1) and continuous minerogenic sedimentation throughout the Holocene in proglacial lakes, in contrast to organic‐rich sediments and low sedimentation rates (0.005 cm a^?1) in neighbouring non‐glacial lakes, suggest that glaciers may have persisted in proglacial lake catchments since regional deglaciation. The presence of varves and relatively high magnetic susceptibility from 10 to 6 ka and since 2 ka in one proglacial lake suggest minimum Holocene glacier extent ca. 6–2 ka. Moraine evidence and proglacial and threshold lake sediments indicate that the maximum Holocene glacier extent occurred during the Little Ice Age. The finding that glaciers likely persisted through the Holocene is surprising, given that regional proxy records reveal summer temperatures several degrees warmer than today, and may be due to shorter ablation seasons and greater accumulation‐season precipitation. Copyright © 2009 John Wiley & Sons, Ltd.     

Two-and three-dimensional linear convection in a rotating annulus

Abstract

An exceptional case to the model-independent theory of Knobloch (1995) is presented, by investigating a rotating cylindrical annulus of height H and side wall radii r _o and r _i, with non-slip, perfectly thermally conducting side walls and thermally insulating stress-free ends. Radial heating permits the possibility of either two- or three-dimensional convective solutions being the preferred mode. An analytical solution is obtained for the two-dimensional case and a numerical solution for the three-dimensional solution, which is also applied to the two-dimensional solution. It is shown that both two- and three-dimensional solutions can be realized depending on the aspect ratio, γ = H/d, where d = r _o-r _i is the thickness of the annulus, the radii ratio λ = r _i/r _o and the rotation rate of the model. For γ = O(1) and λ = 0.4, the preferred convective solution is three-dimensional when the Taylor number, T < 10² and two-dimensional for T > 10². For small aspect ratios, γ ? 1, the preferred mode is two-dimensional for all rotation rates.     

内蒙古敖脑达坝斑岩型铜银锡多金属矿床围岩蚀变特征研究

在给出明确的命名原则基础上，将矿床的蚀变围岩划分为五类：黄玉石英交代岩、绿泥石石英交代岩、绢云母石英交代岩、电气石绿泥石化花岗斑岩、钾长石化花岗斑岩。在平面上岩体中心部位为黄玉石英蚀变带，其两侧为绿泥石石英蚀变带；在剖面上由上向下依次出现绿泥石石英蚀变带→黄玉石英蚀变带→绢英岩化带→钾化带→（电气石）绿泥石化带。从蚀变岩石地球化学角度阐述了铜银锡各自不同的成矿部位。     

Temperature dependence of thermal conductivity and its impact on assessments of heat flux

The variability of sedimentary thermal conductivities with increasing temperature are explored for their impact on estimates of present-day heat flux and subsurface temperature gradient. For sand thicknesses less than about 10–20 km, or shale thicknesses less than about 40–80 km, the subsurface temperature is closely linearly proportional to the thermal resistance integral obtained in the absence of the temperature dependence of thermal conductivity. Estimates of heat flux should be increased (decreased) by about 5% for sands and decreased by about 1% for shales. For salt, because of the much shorter temperature range over which its thermal conductivity decreases, effects produced by the temperature dependence are more noticeable: heat flux should be increased by around 13%, salt thicknesses in excess of 5 km will yield major (around 30–100°C) changes in their temperature regimes solely as a consequence of the temperature-dependent thermal conductivity, and the linear increase of temperature with increasing thermal resistance is not an adequate approximation but has to be replaced with a more exact exponential increase.The impact of the variations, particularly in the case of salt, for geologic processes is briefly considered.     

东西风廓线特征与大气运动平衡态定常波的相关关系及共振条件的研究

本文采用简化数学模型探讨了东、西风廓线特征与外源强迫下大气环流平衡态定常波结构的相关关系。文中采用实际观测资料研究了西风廓线特征与大气环流型季节特征之间的联系。研究表明,西风廓线冬、夏季节差异与中、高纬度西风槽“冬三夏四”波数差气候特征有关,且低纬强东风切变可作为赤道东风波周期振荡成因之一。冬夏西风廓线季节特征可导致大地形强迫效应、海陆加热因子影响作用的显著季节差异。研究还揭示了大气环流型优势波转换的基流特征影响效应,并导出了流场与纬向加热强迫源共振状态的西风廓线特征函数与临界曲线。     

松辽盆地地热场

本文实测了65口井的地热数据,从中取得17个大地热流值,松辽盆地地热场具有中部高边部低,并呈环状分布,该区地热具有高特征的地质发展历史。分区计算盆地的沉积岩层、花岗岩质层和玄武岩质层各底部的温度和热流值,也都具有中部高边部低的变化趋势。分析了盆地地热场受影响的状况和地热高的主要原因。还分析了盆地地热场与构造活动性、地震活动性、重磁力场、岩石圈厚度的关系,以及与石油生成、运移和富集的关系。     

岩石的热惯量研究

本文阐述了热惯量的物理意义及其在地质遥感中的作用。在测得２３种岩石热物理性质的有关参数──热传导率、热容量和密度的基础上，计算并列表给出了岩石的热惯量值和热扩散系数等基础数据。文中分析讨论了沉积岩、变质岩和岩浆岩岩石的热惯量变化由高到低的初步规律。取得了碳酸盐岩和砂岩类等沉积岩和沉积浅变质岩的热惯量差异的结果，指出了它们的易区分性；也指出了中－酸性、碱性岩浆岩之间的热惯量值差异较小，不易区分。     

NWP 模式热量系统误差的动力诊断分析

文章证明了模式在预报时段的位温误差，是由于在模式大气和真实大气中，该时段内位温变化过程的不同而造成的。还证明了原始方程的无加速定理对各强迫因子的线性分解同样适用于研究NWP模式热量误差的成因。对国家气象中心T42L9模式1992年1月和7月预报结果的动力诊断表明，模式对纬向位温分布具有较好的预报能力，但在各纬带也存在明显的误差。通过无加速定理的分解分析，研究了这些误差的成因及改善模式的可能途径。     

下庄矿田基底的控矿作用及其有关地质问题

本文提出武夷及其邻区存在两个裂陷槽及一裂隆，鹰潭－南城－安远－河源韧性断裂带为东部的火山岩型与西部的花岗岩型铀矿床的地质分界线，指出了加里东运动在本区的突出作用是使裂隆基底岩石发生混合花岗岩化作用。根据下庄矿田及其外围发现较深变质的岩石和较大规模韧性剪切糜棱岩带，得出下庄矿田是古老基底加里东热穹隆区多次构造、岩浆活动的产物。由于铀成矿作用赋存于初、脆性两种构造中，建议重新划分矿化类型以指导勘查工作。