Processes that can disturb the chronostratigraphy of laminated sediments and pollen deposition

The sediment trap technique was used to study the sedimentation processes in two parts of Lake Goci, central Poland, the deep of the main basin and the shallow bay area. From field and lab data was noted that seasonal and annual deposition of pollen grains on the lake bottom was disturbed in the main basin by an increase in water mass dynamics and by resuspension and focusing. Greater concordance between pollen sedimentation and the flowering periods of plants was found in the bay area, where sediment resuspension took place sporadically and with less intensity, compared to the main basin. Futhermore, it is suggested that resuspension of pollen can occur even if laminated sediments are formed, a process which therby diminishes the chronostratigraphic value of sediments and pollen analyses.     

Mountain ordering: A method for classifying mountains based on their morphometry

A new method for classifying mountain morphology, ‘mountain ordering,’ is proposed, and quantitative expressions for various morphological parameters of two ordered mountains in northern Japan were obtained using this method. Mountain order was defined in terms of the closed contour lines on a topographic map. A set of closed, concentric contour lines defines a first-order mountain. Higher-order mountains can be defined as a set of closed contour lines that contain lower-order mountains and that have only one closed contour line for each elevation; they are identified as m + 1th-order mountains, where m represents the order of the enclosed, lower-order mountains. The geomorphometry for a mountain ordered according to this definition permits the identification of systematic relationships between various morphological parameters. The relationships between mountain order and these morphological parameters follow a form similar to that of Horton's laws, and permit the calculation of the ratios of number, area and height; these parameters are sufficient to express the magnitude of a mountain's dissection. The size–frequency distribution for area and height shows self-similarity for ordered mountains, and determines their fractal dimensions. Furthermore, the relationship between area and height, which has the form of a power function, describes the relief structure of ordered mountains. Copyright © 1999 John Wiley & Sons, Ltd.     

Influence of rock strength on the valley morphometry of Big Creek, central Idaho, USA

Analysis of valley morphometry and bedrock strength along Big Creek, central Idaho, shows that valley floor width is strongly controlled by bedrock. We performed statistical analysis of Schmidt hammer rock strength as a function of lithology and aspect and of valley morphometry as a function of rock strength. Rock strength is significantly greater on the south side of the valley and in Eocene granodiorites. Rock strength is weakest in Eocene volcanic tuffs. Valley floor width depends negatively on weakest valley-side rock strength, and hillslope gradient on the north side of the valley depends positively on rock strength. Stream gradient does not depend on rock strength. Valley floor width appears to be controlled by bedrock strength on the weaker side of the valley, which was generally the north (south-facing) side. We speculate that a higher degree of weathering via freeze–thaw cycles contributes to lower strength on the north side. The positive dependence of hillslope gradient on rock strength on the north side provides evidence that differential weathering across lithologies determines the gradient that can be maintained as lateral migration of the stream erodes valley walls. These results suggest that in situ rock strength exerts strong influences on some measures of valley morphometry by modulating hillslope mass wasting processes and limiting lateral erosion.     

洞穴形态量计解析

洞穴形态量计的最基本参数是长度、深度、高度和坡度,借助洞穴专业软件可进行洞穴的投影面积、洞道空间体积、洞道极点投影面积、洞道极点岩体体积等其它基本参数的量计,以及洞穴扩展参数包括洞道的比容积、网密度、面密度和体密度的量计。利用这些形态参数,可以对洞穴进行更科学的统计、形态特征分析、开发利用价值评估。通过选取深峰丛洼地区、中等深度峰丛洼地区和浅峰丛洼地区以及峰林平原区的地下河洞穴进行量计,并对量计结果进行相关分析,发现洞穴的比容积与洞穴的流域面积、石峰的相对高度具有良好的正相关性,而洞穴的网密度、面密度,尤其体密度与洞穴深度有着明显的负相关性。      

Morphometry of Glacial Cirques in the Central spanish Pyrenees

A total of 206 glacial cirques have been identified in the high valleys of the Aragón and Gállego rivers, Central Spanish Pyrenees, in order to study the environmental factors explaining their distribution (altitude, aspect, lithology) and diverse morphometric features (area, width, length, L/W relations, etc.). The use of bivariate and multivariate statistical analyses confirms that a part of the morphometric variability of the glacial cirques is explained by the environmental factors considered here, but their influence is relatively limited. Altitude is identified as the most important factor, affecting both the length and the degree of over–deepening of the cirques. The role of lithology is less obvious because of its interaction with altitude.     

Quantitative Size Classification of Scoria Cones: The Case of Tenerife (Canary Islands,Spain)

Monogenetic volcanoes are the most abundant volcanic structures on the Earth's surface. Thousands of them exist in different tectonic contexts (e.g., subduction zones, intraplate areas, and divergent boundaries), appearing in groups forming volcanic fields. Tenerife, the largest and highest island of the Canarian archipelago, started to form about 14 million years ago (Ma), as a result of a complex eruptive history and a varied geomorphological evolution, including shield-building stages, volcanic rifts, stratovolcanoes, and monogenetic cones. Tenerife is an active, volcanic, oceanic island, where the last eruption occurred in 1909. In this paper, we propose a methodology for calculating the size of monogenetic basaltic volcanoes based on morphometric parameters, as well as a classification of the size of the volcanoes through the study of 297 scoria cones of Tenerife. Morphometric techniques, based mainly on height (H_co), volume (V_co), and area (A_co), were used together with correlations between different morphological parameters. The result is a simple quantitative classification, easy to use for estimating the size of monogenetic volcanoes. Of the monogenetic basaltic volcanoes of Tenerife, 98.98% fit into this classification, which distinguishes between large (H_co >200; V_co >0.1; A_co >0.5), medium (H_co >100 to <200; V_co >0.01 to <0.1; A_co >0.2 to <0.5), and small (H_co <100; V_co <0.01; A_co <0.2) volcanoes. There is a strong correlation between the size of cinder cones and their age: the more recent scoria cones are smaller in size than the older ones. This relationship supports suggestions by other researchers that eruptions have decreased in magnitude and the volume of available magma has become smaller. The results obtained by calculating the size of the scoria cones of Tenerife make possible the extrapolation of this technique to other insular or continental monogenetic volcanic fields.     

印度喀拉拉邦雨影区流域系统形态分析及其水文意义(英文)

The rain shadow regions requisite a comprehensive watershed development and management plan for sustainable water resources management. The Pambar River Basin (PRB) lies on the rain shadow region of the southern Western Ghats, India, where climate showed marked intra-basin variation. A morphometric analysis was done to evaluate the drainage characteristics of PRB using topographical maps and digital elevation data. PRB was divided into eighteen 4th order basins (SB1-SB18), distributed along various climatic...     

Seasonal variation of crescentic dune morphology and morphometry,Strzelecki–Simpson Desert,Australia

The general absence of contemporary dune building in the Australian arid zone finds the occurrence of crescentic dune genesis and evolution at Gurra Gurra waterhole, a somewhat enigmatic event amongst prevalent inactive linear dunescapes. Crescentic dune construction is geographically restricted to areas of dominant unidirectional high windiness and minimal vegetation, parameters that are generally uncommon in arid Australia today. The influence of seasonal multidirectional winds can see dune form undergo continual transition between quasi‐equilibrium and disequilibrium. Such dynamic antithesis is depicted in seasonal mathematical comparisons of the planimetric attributes, length and width. Dimensional equilibrium is a transient feature at Gurra Gurra waterhole and not characteristic of this dunescape. Copyright © 2001 John Wiley & Sons, Ltd.