中国不同气候带盐风化作用的地貌特征

盐风化作用是地球表面普遍存在的一种物理风化作用,由于盐类的周期性结晶作用而造成地表岩石和建筑材料的破坏,形成诸如风化穴或蜂窝石构造等地貌景观。盐风化作用也是差异风化的主要表现形式之一。然而,到目前为止盐风化作用在中国地学界仍然被严重忽视,以至于盐风化作用造成的地貌景观常常被地学研究者和科普人士误读为海浪冲蚀、流水侵蚀、风蚀作用等。经过近十年的野外观察与探讨,笔者等对盐风化的形成机理和表现形式有了深入的理解。本文以中国境内东部海岸带、华北半干旱区、西北干旱区和东南湿热气候带基岩露头为例,系统地分析了盐风化作用的机理及其在不同气候带的表现形式。盐风化的必要条件是:适当的可溶性盐类(如Na_2SO_4、NaCl等)供应、周期性的干湿交替和温度变化。盐风化作用主要在发育可渗性孔隙的砂砾岩类和富含微裂隙的花岗岩类之露头表面表现明显,可以形成特征显著的盐风化穴。盐风化作用形成的地貌景观在东部海岸带和西北干旱区表现尤为明显,常常形成蜂窝石构造和大型风化穴,与风蚀作用的痕迹明显有别;而在华北半干旱区和南方湿热气候带虽然受到降雨等其他因素的影响而常常遭受改造、叠加甚或清除,但在某些露头区仍然保留有重要的识别标志,形成大型风化穴以及小型蜂窝石构造。笔者等强调:地表各种地貌景观形成过程中都有盐风化作用的贡献,而建筑物和景观保护也必须考虑到盐风化作用的影响。建议地学同仁重视盐风化作用的普遍性和重要性,在相关教材中补充更新盐风化的概念,并以科普的方式通过多种媒体纠正过去的错误认识。     

Quartz sandstone peak forest landforms of Zhangjiajie Geopark, northwest Hunan Province, China: pattern, constraints and comparison

The Zhangjiajie Sandstone Peak Forest Geopark in northwest Hunan Province, China, is a comprehensive geopark containing many spectacular quartz sandstone landforms, limestone karst landscapes and various other important geoheritage resources. It is listed as a UNESCO World Geopark and is also part of the World Heritage Wulingyuan Scenic and Historic Interest Area for its important landscape features. Many of the sandstone landforms, particularly the vast number of thin pillars or spires, are very unusual and serve as the core landscapes of the geopark. But Zhangjiajie displays a diverse range of landform types, exhibiting spectacular patterns and regular distributions. In this paper, the geomorphic traits, distribution pattern and constraints of the sandstone landforms of the Zhangjiajie Geopark are examined. Our study indicates that in the outcropping areas, the sandstones display four distinctive levels from 300 to 1,000 m above sea level, and these extend clearly from the highest sandstone plateau platform to the center of the valleys. The high sandstone platforms developed close to a flat high-level erosional surface, and subsequent erosion into this plateau has resulted in successively lower levels of landforms that transition gradually from peak walls, peak clusters, peak forests and peak pillars to remnant peaks in the lower valley bottoms. The form and distribution of the Zhangjiajie sandstone landforms are primarily dominated by the geological setting, particularly the presence of brittle structures (fractures and joint sets) trending NNW, ENE and NE. Triggered by the episodic tectonic movements, major streams and escarpments frequently occur along these structural directions, while some of the peak walls, peak clusters and peak forests have their longer elongated axes corresponding to NE or NNW directions, with an increased density of peak forms at the intersection of these fractures and joints. The geometry of the diverse sandstone landforms is also influenced to a certain degree by the climatic, water system distribution, lithologic properties, biological process, meteorological features and denudation processes. The suite of quartz sandstone landforms in Zhangjiajie can be compared with other sandstone landscapes regionally, and our interpretation of the sandstone peak forest formation processes offers a significant contribution to the study of topographic features and the geomorphic evolution of sandstone landscapes.     

青海地质旅游发展探讨

地质旅游是一种新兴的旅游形式,具有知识性、观赏性和趣味性等多种特点和优势,正以其独特的魅力,发展成为重要的旅游产品,具有广阔的发展前景,近年已逐步成为一个新的发展热点。青海具有典型地质剖面、地质地貌景观、水体景观、地质工程景观、古生物化石遗迹、典型矿床景观和地质灾害遗迹景观等丰富独特的地质遗迹。目前已建立4家国家地质公园,但地质旅游尚处于起步阶段。根据青海旅游市场客源现状,利用SPSS12forWindows对1996～2005年青海游客人数进行曲线拟合,利用所得Cubic模型预测了青海地质旅游市场客源发展趋势,并在分析、评价青海地质遗迹的基础上,讨论了目前地质旅游发展所面临的一些问题,并提出了相应的对策及建议。     

广西桂平白石山丹霞地貌景观特色与成因过程

中国是世界上研究丹霞地貌最早的国家, 随着2010年"中国丹霞"世界自然遗产的成功申报, 丹霞地貌作为一个地貌类型的名称已走出国门被世界所承认.在介绍广西桂平白石山丹霞地貌空间分布和景观特色基础上, 对其形成条件和过程进行分析探讨, 指出: (1)白石山丹霞地貌典型集中、类型齐全、景观独特, 具有典型的"顶平、身陡、麓缓"的丹霞地貌特征; (2)白石山丹霞地貌是古近纪山间盆地沉积的红色碎屑岩, 由构造运动盆地隆起、侵蚀、溶蚀作用、流水切割以及重力崩塌等内、外动力作用塑造形成; (3)白石山丹霞地貌具有地层沉积时代新、形态宏伟的特色, 在各丹霞地貌中较为罕见, 具有很高的科学价值.      

Etch and intracutaneous landforms and their implications

Many landforms, major and minor, and including plains of various types, inselbergs, boulders, flared slopes, Rillen and rock basins, are initiated beneath the land surface, at the weathering front. They have evolved in various lithological settings. Most are formed by differential moisture attack, either controlled, or strongly influenced, by bedrock structure. Such forms of subsurface derivation may be differentiated into etch or subcutaneous features that were initiated at the base of the regolith, and intracutaneous forms that had their origin within the weathering zone. Although the agent or agents responsible for eroding the regolith and exposing the bedrock forms have varied in space and time, the similarity of etch and intracutaneous forms is such that their basic morphology persists regardless of the climatic regime in which they now occur. As the regolith is widely developed on the land surface, the forms initiated beneath and within it cannot be taken as climatic indicators. Indeed, like structural forms, these convergent forms represent a varied but significant azonal element in the physiographic landscape.     

蜀南地区茅口组古岩溶地貌与缝洞系统发育关系研究

蜀南地区茅口组古岩溶地貌形态对缝洞系统的发育起着控制作用。在恢复茅口组古地貌的基础上,根据上二叠统在区域上的分布厚度、风化壳表面侵蚀特征和茅口组地层保存程度,将茅口组顶部古岩溶面划分为岩溶台地、岩溶坡地(又分为西部陡坡带和北东部缓坡带)和岩溶盆地3个二级地貌单元;研究了各地貌单元和缝洞系统发育关系。结果表明:岩溶台地岩溶水以垂向渗流为主,风化剥蚀强烈,形成垂向的溶缝、溶洞常被泥质等充填,横向连通性弱;岩溶陡坡、岩溶台地和岩溶陡坡过渡带岩溶作用最强,溶孔、溶洞发育,且充填程度低,缝洞系统最为发育,是有利的勘探区带;岩溶缓坡水流速度慢,岩溶作用周期长,溶蚀空间易受充填,不利于缝洞保存;岩溶盆地岩溶发育最弱,储集性能差,是不利的勘探区带。      

Diagnosis of weathering damage on rock-cut monuments in Petra, Jordan

Studies of many years—combining in situ investigation and laboratory analysis—have provided comprehensive information on weathering damage on the rock-cut monuments in the ancient city of Petra in Jordan. These rock-cut monuments represent outstanding world heritage. Many hundred monuments were carved by the Nabataeans from bedrock about 2000 years ago. The awareness of increasing weathering damage on the monuments has resulted in international efforts towards their preservation. The damage diagnosis has addressed the complex mutual relationships between stone types, stone properties, monument exposure regimes, environmental influences, weathering phenomena, development and extent of weathering damage and weathering progression. The rocks were classified lithostratigraphically and petrographically. Results on weathering forms, weathering profiles and weathering products obtained from monument mapping, in situ measurements and laboratory studies revealed a complex diversity of weathering phemomena with respect to type and intensity. Damage categories and damage indices were used to create a reproducible quantitative rating of weathering damage. Detailed results on weathering forms allowed the characterization and quantification of weathering progression including weathering prognoses. Stone properties and states of weathering damage were jointly considered for the rating of the rocks’ susceptibility to weathering. The systematic evaluation of weathering damage and monument exposure regimes can enhance the assessment of weathering factors and processes.     

Development of sediment–landform associations at cold glacier margins,Dry Valleys,Antarctica

The impact of modern cold glaciers on arid periglacial landscapes has received little attention compared with other glacial regimes, and there is a widely held assumption that cold glaciers are not effective geomorphological agents, despite recent studies to the contrary. This paper focuses on the processes operating at the margins of a number of glaciers in the Dry Valleys of Victoria Land, notably the Wright Lower Glacier. The glaciers are entraining primarily older drift deposits and highly weathered regolith which texturally are sandy gravels, as well as well‐sorted sands of fluvial origin. Despite basal temperatures of the order of ?16°C, frozen layers and blocks of sand and gravel are being incorporated into the base of the glaciers by folding and thrusting. The sedimentary products are ridges and aprons several metres high within which the principal lithofacies are sand, gravel, foliated glacier ice, lake ice and snow. These facies are glaciotectonized strongly. Draped over these landforms is a veneer of well‐sorted aeolian sand up to half a metre thick. Supraglacial streams flowing off the glaciers incise these landforms and the sediment is redeposited as alluvial fans, lake deltas and lake‐bottomset deposits. Overall the sediment/landform association differs markedly from those of other glacial regimes, with sand and gravel being the dominant facies, while the usual indicators of glacier working (such as facets and striations on clasts) are lacking. The preservation potential for these landforms on a thousand‐year time scale is high, as modification in this arid regime by slope processes and running water is limited. Sublimation of buried ice is so slow that ridge features are likely to remain ice‐cored almost indefinitely, modified only by wind transport and weathering.     

北京岩溶水资源信息系统的设计与实现

着重研究系统总体结构,系统数据组织和管理以及系统专业功能的设计与实现。本系统基于．NET平台和ArcGIS二次开发而成,最终实现数据信息的可视化管理及应用。     

江西信江盆地白垩系沉积体系及其与丹霞地貌的关系

根据野外沉积层序、岩石学特征、古生物资料和地貌景观特征,本文对江西信江盆地白垩系沉积相进行了初步分析,首次探讨了沉积体系与丹霞地貌发育特征之间的内在联系。信江盆地白垩系主要发育4种沉积体系,即冲（洪）积、三角洲、湖泊和扇三角洲。早白垩世主要发育半深湖-深湖、扇三角洲相沉积,晚白垩世从盆地南缘到北缘大致为洪冲积相→辫状河流→三角洲→滨浅湖→三角洲→辫状河流→洪冲积相的展布方式。研究表明,该区丹霞地貌形成的物质基础主要是上白垩统冲积扇、辫状河相沉积产物,丹霞地貌的空间分布与盆地冲积扇、辫状河沉积相的平面展布具有较好的一致性,同时,沉积亚相、微相类型对丹霞地貌的发育起到一定的控制作用。     

新疆乌恰康苏地区构造地貌与景观生态格局研究

新疆乌恰康苏地区位于西昆仑山与西南天山对冲作用形成的盆山耦合带,其构造地貌具有显著的山地-平原分布格局特征.文章以"3S"技术为基础进行构造地貌填图,划分新疆乌恰康苏地区的景观类型,研究构造地貌对该区域景观生态格局的影响.采用垂向山地-平原构造地貌为指标,划分5个景观类;以土地利用类型+植被覆盖为指标,划分6个景观型;...     

Deglaciation and glacial lake development in the Kaamasjoki river basin, Finnish Lapland

The glacial hydrology of the meltwaters of the ice sheet during deglaciation in a large river basin has been reconstructed on the basis of heights of thresholds and saddles of bedrock topography, glaciofluvial accumulation forms (eskers, deltas and plains of sorted material) and erosional landforms (drainage channels and shorelines) as well as a few terminal moraines. The water level of glacial lake dropped in several stages. The lake existed and deglaciation took place before 9740±280 years B.P. The deglaciation took place at a much faster rate in the studied region than later in western Lapland.     

An overview of the role of weathering in the production of quartz silt

Quartz silt is a widespread detrital sediment with large aeolian (loess) and alluvial silt deposits forming important components of many contemporary landscapes. Despite research findings which indicate that a range of opportunities exist for the comminution of quartz into silt particles within a wide variety of geomorphic environments (e.g. glacial grinding, fluvial comminution, aeolian abrasion, frost weathering, salt weathering, insolation weathering and deep weathering), the ‘glacial-aeolian’ hypothesis has traditionally been favoured as the most likely explanation for loess formation and loess is seen as primarily a Quaternary phenomenon. As a consequence there has been a tendency to underestimate sediment inputs into loess systems by geomorphological processes operating within pre-Quaternary environments. In particular, earth scientists may have considerably underestimated the role of weathering in global silt generation, as there are now many references to the existence of a patchy but widespread distribution of pre-Quaternary weathering profiles across the glacial and periglacial landscapes of the Northern Hemisphere (e.g. North America, British Isles, north and central Europe), landscapes within which many of the classical loess deposits are located. These observations suggest that weathering profiles may have covered large tracts of the Northern Hemisphere land surface prior to the Quaternary glaciations. This, in turn, may have important implications for quartz silt generation as: (1) experimental studies indicate that many weathering processes are capable of generating significant quantities of silt-sized debris, and (2) particle characteristics displayed by saprolitic material that has developed on quartz rich crystalline source rocks often include significant quantities of either silt-sized material, or quartz grains that are weakened by weathering derived microfractures. Thus, weathering profiles may represent ‘mines’ of actual and potential quartz silt, available for release into sedimentary systems when these profiles are subsequently reworked by geomorphological processes such as glacial, fluvial and aeolian erosion.     

试论红色岩溶概念及其科学价值

岩溶地貌在全球广泛分布,造就了丰富多彩的地貌形态及自然景观。在我国湘黔鄂渝交界区存在着极具观赏性的特殊岩溶地貌,其形态特征有别于常见的岩溶地貌。但当前对这套特殊岩溶地貌的名称及其地学价值尚未深入探讨。该类型地貌具有四个基本特点:红颜色、层状凹凸形态、泥质灰岩的成景岩性、土下环境差异溶蚀成因。在对比分析它与红色系地貌、已认识的岩溶形态、常见岩溶地貌的差异性基础上,文章采用“外观特征”+“地貌类型”的命名原则将它命名为“红色层状凹凸岩溶地貌”,简称“红色岩溶”,并提出其科学定义及界定标准。红色岩溶具有重要的地学价值,其极具观赏性的独一无二形态使得红色岩溶具有重要的旅游经济价值。      

岩石物理化学性质对泰宁丹霞洞穴的形成制约

泰宁丹霞红层由铁钙质混合胶结的较松散固结红色砂砾岩构成,岩石胶结物中CaCO3含量较高,抗压强度极低、孔隙度和含水性均较高。当岩石遇水湿润或浸泡时,或者生物风化过程中受到各种动植物分泌的有机酸作用,岩石胶结物中CaCO3易溶解流失,促使丹霞红层进一步软弱松散。冬季水结冰之后体积会膨胀,所以岩层表面产生片状裂隙。通过裂隙的毛细管效应,孔隙-裂隙水由岩石内部向结冰的表面扩散,在表面张力作用下水呈表面积最小的球状。春季化冻时岩石沿球形片状裂隙自由剥落的片状风化,圆球形洞穴开始形成,随着四季交替,年复一年,间歇性结冰和融化过程,使得洞穴逐渐扩大,形成泰宁丹霞各种形态的洞穴奇观。     

Contaminants from cretaceous black shale: II. Effect of geology,weathering, climate,and land use on salinity and selenium cycling,Mancos Shale landscapes,southwestern United States

The Cretaceous Mancos Shale (MS) is a known nonpoint source for a significant portion of the salinity and selenium (Se) loads in the Colorado River in the southwestern United States and northwestern corner of Mexico. These two contaminants pose a serious threat to rivers in these arid regions where water supplies are especially critical. Tuttle et al. (companion paper) investigates the cycling of contaminants in a Colorado River tributary watershed (Uncompahgre River, southwestern Colorado) where the MS weathers under natural conditions. This paper builds on those results and uses regional soil data in the same watershed to investigate the impact of MS geology, weathering intensity, land use, and climate on salt and Se storage in and flux from soils on the natural landscape, irrigated agriculture fields, areas undergoing urban development, and wetlands. The size of salinity and Se reservoirs in the MS soils is quantified. Flux calculations show that during modern weathering, natural landscapes cycle salt and Se; however, little of it is released for transport to the Uncompahgre River (10% of the annual salinity and 6% of the annual Se river loads). When irrigated, salinity and Se loads from the MS soil increase (26% and 57% of the river load, respectively), causing the river to be out of compliance with Federal and State Se standards. During 100 years of irrigation, seven times more Se has been removed from agricultural soil than what was lost from natural landscapes during the entire period of pedogenesis. Under more arid conditions, even less salt and Se are expected to be transported from the natural landscape. However, if wetter climates prevail, transport could increase dramatically due to storage of soluble phases in the non-irrigated soil. These results are critical input for water-resource and land-use managers who must decide whether or not the salinity and Se in a watershed can be managed, what sustainable mitigation strategies are possible, and what landscapes should be targeted. The broader implications include providing a reliable approach for quantifying nonpoint-source contamination from MS and other rock units elsewhere that weather under similar conditions and, together with results from our companion paper, address the complex interplay of geology, weathering, climate, and land use on contaminant cycling in the arid Southwest.     

Cavernous Weathering in Aeolian Sandstones: An Example from the Yongningshan Hill of the Loess Plateau, Northwest China

Cavernous weathering is commonly found on sandstone slopes in different environments. Either a single dominant process or polygenetic agents require to be invoked in order to interpret the development. The Yongningshan hill of the central Loess Plateau is representative of cliff dwellings in Northwest China, which is characterized by well-developed cavernous weathering features and provides a good opportunity for the better understanding of sandstone weathering in the Loess Plateau. Multiple methods, including field survey, in-situ rock strength measurement, along with experiments on samples for microscopic observation, element composition and salt chemistry, were employed to investigate the controlling factors of cavernous weathering. The results show that cavern development is different on the four slopes with the western slope hosting massive honeycombs, tafoni and hardened surfaces. The porous and permeable aeolian sandstones are fundamental, because they provide space and pathways for the transportation of water and salt, honeycombs dominantly aligning within the lamination of cross-beds. The environmental factors such as the seasonal wetting and drying cycle, aeolian salt, moisture and water vapor are key factors for the development of cavernous weathering forms. The northern and northwestern wind-blown dust storms have brought abundant salts, the lengthier dry periods of the wetting and drying cycle being beneficial for salt accumulation within caverns, favoring salt weathering.     

Long-term rates of chemical weathering and physical erosion from cosmogenic nuclides and geochemical mass balance

Quantifying long-term rates of chemical weathering and physical erosion is important for understanding the long-term evolution of soils, landscapes, and Earth's climate. Here we describe how long-term chemical weathering rates can be measured for actively eroding landscapes using cosmogenic nuclides together with a geochemical mass balance of weathered soil and parent rock. We tested this approach in the Rio Icacos watershed, Puerto Rico, where independent studies have estimated weathering rates over both short and long timescales. Results from the cosmogenic/mass balance method are consistent with three independent sets of weathering rate estimates, thus confirming that this approach yields realistic measurements of long-term weathering rates. This approach can separately quantify weathering rates from saprolite and from overlying soil as components of the total. At Rio Icacos, nearly 50% of Si weathering occurs as rock is converted to saprolite; in contrast, nearly 100% of Al weathering occurs in the soil. Physical erosion rates are measured as part of our mass balance approach, making it particularly useful for studying interrelationships between chemical weathering and physical erosion. Our data show that chemical weathering rates are tightly coupled with physical erosion rates, such that the relationship between climate and chemical weathering rates may be obscured by site-to-site differences in the rate that minerals are supplied to soil by physical erosion of rock. One can normalize for variations in physical erosion rates using the “chemical depletion fraction,” which measures the fraction of total denudation that is accounted for by chemical weathering. This measure of chemical weathering intensity increases with increasing average temperature and precipitation in data from climatically diverse granitic sites, including tropical Rio Icacos and six temperate sites in the Sierra Nevada, California. Hence, across a wide range of climate regimes, analysis of chemical depletion fractions appears to effectively account for site-to-site differences in physical erosion rates, which would otherwise obscure climatic effects on chemical weathering rates. Our results show that by quantifying rates of physical erosion and chemical weathering together, our mass balance approach can be used to determine the relative importance of climatic and nonclimatic factors in regulating long-term chemical weathering rates.     

Geomorphology and geomorphological heritage of the Ifrane–Azrou region (Middle Atlas,Morocco)

Geomorphological heritage is a widely used term in European and North-American countries, but is still scarcely mentioned in Africa. Nevertheless, the attractiveness of the African countries is often intimately connected to its breathtaking and endless geological landscapes. Morocco is one of those countries that has the widest diversity in landscapes and landforms, ranging from the Mediterranean and Atlantic coasts over the Rif, Middle Atlas, High Atlas and Anti-Atlas mountain chains to the great rocky and sandy deserts in the South. A wide variety of geological units hosting different types of important economic mineral deposits cover a temporal range from Late Precambrian to Quaternary. A detailed geomorphological study has been carried out in the region of Ifrane and Azrou (Middle Atlas, Central Morocco) using a combination of high resolution satellite data and direct field observations integrated by geological maps and scientific literature. In order to describe and evaluate the geomorphological heritage of this area, 40 geomorphosites have been selected comprising springs, karst landforms (polje, dolines, caves, sinkholes, stone forests, cryptokarstic dolines), carbonate depositional landforms (travertines and waterfalls), fluvial landforms (meanders, canyons, palaeo-valleys, etc.), structural landforms (triangular facets, hogbacks, cuestas, residual outcrops, etc.) and volcanic landforms (volcanoes, caldeira, pyroclastic cones, lava tube). The results of this research have been summarised in a thematic map, representing the geomorphosites related to various landscape units.