Post-glacial rock weathering processes on a roche moutonn@e in the Riksgränsen area (68°N), northern Norway

Weathering processes responsible for landscape denudation in Arctic environments are poorly understood. Traditionally, gelifraction has been widely invoked as the dominant weathering process, but empirical support for this is frequently lacking. In Norwegian Lapland, post-glacial weathering has been recently attributed to predominantly biophysical processes, based on field measurements of landscape lowering undertaken by André (1995). The study reported here examined bedrock samples from one of André's sites for mineralogical and chemical transformations since post-glacial exposure. Backscatter scanning electron microscopy reveals extensive mineral grain dissolution and accompanying development of rock porosity. Wavelength dispersive spectroscopy shows these mineral alterations to be the result of the loss of major chemical constituents including Ca, Mg, K, Si, and Al. Chemical weathering is clearly a component of post-glacial landscape denudation in Norwegian Lapland, in addition to the important role of biophysical processes identified by André (1995). Cosmogenic dating of the sampled bedrock surface confirms that much of this weathering has occurred in the last 10,000 years.     

中国地图制图技术的演进与前瞻

中国地图科学工作者在继承和发扬祖国地图科学光辉传统的同时,吸取地球科学,空间技术和信息工程等学科的现代成就,使当代地图科学技术取得长足的进展,几十年来,航空摄影与系列制图,航天遥感与动态制图,计算机制图与电子地图,地理信息系统与制印一体化等先进科学技术已取得瞩目成绩,专题地图集的编制与信息时代相呼应,出现一些新观念,新技术,随着地球信息科学新学科的兴起,地图科学将出现新机遇,新挑战。     

四川盆地北部地区三叠系构造及其演化特征分析

四川盆地北部地区以下三叠统嘉陵江组四段-五段的大套膏岩层为分割层,将其分为上下两个构造层,上构造层断裂以膏岩层作为主滑脱层,上、下构造层断裂均终止于膏岩层。区内东部构造运动最为强烈,断裂非常发育。中部地区上构造层断裂相对发育,下构造层不发育。西部受构造运动影响最小,断裂不发育。断裂样式主要表现为"Y"或反"Y"字型组合、"树枝状"、平行及对冲断裂等。三叠系主要在平昌-达州-宣汉一带发育北东-南西向断裂,通江以东地区以北西-南东走向为主,中部平昌-龙岗一带受力复杂,断裂走向较不规律,元坝地区发育有南北走向断裂,往西断裂逐渐不发育。全区可划分为7大构造带,其中米仓山前缘褶皱构造带包含了西部九龙山背斜和东部通南巴构造; 川北凹陷构造带仅在上构造层有少量断裂发育; 川北平缓构造带上构造层发育大量中小型断裂; 大巴山前陆盆地构造带属于断褶发育的凹陷带; 川东高陡构造带构造变形强烈,上构造层多发育披覆背斜及较陡断背斜,下构造层发育断背斜并伴有断堑、断垒特征。该地区下构造层断裂发育开始于印支早期构造运动,印支中后期断裂活动进一步加强; 上构造层断裂发育始于印支中后期构造运动,盆地北部整体开始抬升使雷口坡组顶部遭受剥蚀; 燕山期上、下构造层断裂进一步发育,山前褶皱构造带挤压变形强烈,构造格局基本定型,喜马拉雅山期运动对研究区构造具有叠加改造作用。     

Modelling the Planetary Nebula

Deep narrow-band imaging and spectroscopy of the Planetary Nebula (PN)surrounding V4334 Sagittarii have been obtained since the onset of thethermal pulse in the star. Although of low surface brightness,narrow-band imaging suggests a ring structure maybepresent. Abundances, expansion rates and physical parameters for thenebula, derived from spectroscopy, show the plasma to be essentiallytypical of old evolved PN (within the errors of observation). The mostrecent data show little evidence of recombination indicating a verylow plasma electron density.Assuming no recombination has occurred, models of the PN spectrum wereconstructed using both simplistic ideas as well as sophisticatedphoto-ionisation codes. These show good agreement, and suggest that thepre-outburst UV radiation field would need to be powered by aprecursor with a surface temperature of T > 10⁵K. The luminosity ofthis star is less well constrained by the models, and cannot be usedsolely to accurately determine its distance. However, by excludingunrealistic models we expect 250 > L/L_odot > 1000 or so. When plotted ona HR diagram for evolved stars this shows good agreement with thatexpected for a pre-last thermal pulse object.     

Groundwater recharge and chemical evolution in the southern High Plains of Texas, USA

The unconfined High Plains (Ogallala) aquifer is the largest aquifer in the USA and the primary water supply for the semiarid southern High Plains of Texas and New Mexico. Analyses of water and soils northeast of Amarillo, Texas, together with data from other regional studies, indicate that processes during recharge control the composition of unconfined groundwater in the northern half of the southern High Plains. Solute and isotopic data are consistent with a sequence of episodic precipitation, concentration of solutes in upland soils by evapotranspiration, runoff, and infiltration beneath playas and ditches (modified locally by return flow of wastewater and irrigation tailwater). Plausible reactions during recharge include oxidation of organic matter, dissolution and exsolution of CO₂, dissolution of CaCO₃, silicate weathering, and cation exchange. Si and ¹⁴C data suggest leakage from perched aquifers to the High Plains aquifer. Plausible mass-balance models for the High Plains aquifer include scenarios of flow with leakage but not reactions, flow with reactions but not leakage, and flow with neither reactions nor leakage. Mechanisms of recharge and chemical evolution delineated in this study agree with those noted for other aquifers in the south-central and southwestern USA. Electronic Publication     

Experiments on Channel Evolution due to Dam Removal in Taiwan

Due to safety concerns and habitat restoration for landlocked salmon,a 13-m high check dam on Chijiawan Creek was removed in late May 2011 in Taiwan.We conducted experiments to understand channel evolution of different scenarios.We further compared our experimental results of riverbed elevation changes with the analytical solutions derived from the diffusion equation and field dynamics as well after the creek experienced the first flood event.The results indicated that magnitude of discharges and notch size are dominant factors in resulting channel evolution.While the largest differences between grain size distribution are associated with discharge,the largest differences in net change in upstream volume are associated with notch size.While the theoretical equation could help understand the channel change after dam removal,it only explained the evolution closer to the dam.The physical experiments,on the other hand,provided insights especially with regard to comparing alternative proposed management actions.The discrepancies between predicted and actual outcome highlight more needed inputs for future dam-removal assessments.     

http://www.sciencedirect.com/science/article/pii/S1674987113000832

The Sinus Iridum region, the first choice for China＇s＂Lunar Exploration Project＂is located at the center of the lunar LQ-4 area and is the site of Chang＇e-3 （CE-3）＇s soft landing. To make the scientific exploration of Chang＇e-3 more targeted and scientific, and to obtain a better macro-level understanding of the geotectonic environment of the Sinus Iridum region, the tectonic elements in LQ-4 region have been studied and the typical structures were analyzed statistically using data from CE-1, Clementine, LRO and Lunar Prospector missions. Also, the mineral components and periods of mare basalt activities in the study area have been ascertained. The present study divides the tectonic units and establishes the major tectonic events and sequence of evolution in the study area based on morphology, mineral constituents, and tectonic element distribution.     

热带大气发展运动的低频模式

当热带大气运动的适应过程完成后,即进入到缓变的发展运动,描写发展运动的模式有Gill的长波近似模式以及作者提出的短波近似模式.文中在分析这两个模式的特点和不足之处后,提出了低频近似下的发展模式.如f0是热带地区典型的科氏参数值或惯性振荡频率,设运动的特征频率为σ,则长波和短波近似的成立条件之一,要求σf0.而低频近似模式要求σ2f02,即对运动频率的要求比长波或短波近似模式降低一个量级,因此适用性更广.     

1410号台风Matmo登陆前后的动热力结构演变和水汽输送特征分析

利用NCEP/NCAR（美国国家环境预报中心/国家大气研究中心）的全球预报系统（GFS）再分析资料、欧洲气象中心（ERA-interim）资料以及中国气象局观测站点的实况降水观测结合CMORPH卫星反演降水资料,对2014年第10号台风Matmo生成后西北行并登陆台湾及福建过程中的特征进行了分析,揭示出Matmo移动路径主要受西太平洋副热带高压（简称西太副高）外围引导气流影响。动、热力物理量场分析表明,Matmo在登陆福建前后,福建上空一直维持深厚的涡旋结构,福建东南部上空的上升区与台湾海峡及福建西部附近的下沉运动区形成明显的垂直环流圈。同时,南海上空有明显的西南急流（风速大于16 m s-1）,Matmo的水汽来源主要有两条,分别为孟加拉湾和南海以及西太副高南侧。充足的水汽输送及低层水汽辐合抬升有利于Matmo登陆后的强降水发生和维持。Matmo登陆福建后仍然保持低层辐合、高层辐散,有利于持续暴雨的发生。Matmo登陆福建期间始终处于风速垂直切变小值区（小于9 m s-1）中,环境风速的弱垂直切变有利于Matmo暖心结构及高空辐散形势的维持,是Matmo在登陆后依然能维持自身强度不衰减的原因之一。     

热带大气和海洋的半地转适应和发展运动

半地转适应和半地转发展是热带大气和海洋运动的两种基本形态,它们在时间上是可分的,反映了不同的物理过程。当初始扰动作用于大气或海洋时,首先将激发出重力惯性波,当重力惯性波频散后,建立起半地转的平衡状态,此后运动进入到以Rossby波(长波或短波)、Kelvin波和混合波中的Rossby短波为主导的发展状态。文中研究的纬圈半地转适应和发展运动,是Gill长波近似模式的理论基础。同时研究了经圈半地转适应和发展运动,实际上这相当于短波近似模式,它可以应用到研究海洋经圈边界附近的一类问题。