Filling of dolines with aeolian sediments in the high-mountain karst of the Dinarides(Mt.Durmitor,Montenegro)

Filling of dolines with aeolian sediments,one of the less frequently described ways in which they are filled,is analysed in the present study on an example of a doline in the high-mountain karst of the Dinarides.There is a series of deep dolines on a broad ridge(about 2450 m a.s.l.)on Mt.Durmitor(Montenegro)in the southeastern part of the Dinarides.The accumulation of very fine-grained sand that almost completely fills one of the dolines was analysed.More than 99% of the accumulation was found to be composed of well-sorted quartz grains with an average size of 89μm and no vertical differences in granulometric or textural characteristics.With respect to mineral composition,the accumulation differs significantly from that prevalent in this part of the Dinarides,in which different kinds of carbonate rocks are dominant.The conducted analyses indicated an aeolian origin of the sediments.Significant aridification that began in the Middle Holocene made the area of North Africa a source of sediments that were transported by the aeolian process to neighbouring regions.Geomorphological-sedimentological research on Mt.Durmitor and earlier investigations of the wider Mediterranean region indicate that dolines in highmountain karst can be filled with aeolian sediments.The sediments originated from territory of the northern Sahara,and the filling occurred in the Late Holocene,at the close of the African humid period.The present study shows that apart from the influence of local factors,regional geomorphological processes such as aeolian transport can also exert significant influence on the filling of dolines.It also indicates a high intensity and strongly expressed dynamics of aeolian sediment transport from the territory of Africa to this part of Southern Europe.

Analysing the Influencing Factors of a Postgenetic Subsidence Doline’s Development Using Model Experiments

The subsidence dolines are the most common surface forms of the concealed karsts.One type of these dolines is the suffosion doline.In this model experiment the influential role of these kind of dolines’development factors were analyzed.The aim of the study was to determine the significance of the parameters(cover thickness,secondary porosity of the bedrock,chimney diameter,grain size)that influence the development of a suffosion doline.To study the influencing factors numerous(162)experiments were made with different parameters,in a manner that during the experiments we changed only one parameter,so the effects of it would be detectable from the final solution.These measurements were made with the use of a special tool,designed and built for this purpose.According to the data we gained from the model experiments,the development of a suffosion doline is influenced by many parameters.If these parameters are in an optimal connection to each other,a suffosion doline may appear on the surface.Knowing these parameters of the covered karstic depressions lets us estimate other parameters that may influence the development of the subsidence dolines.

A quantitative morphometric comparison of cockpit and doline karst landforms

This study presented a quantitative comparison of cockpit and doline karst by examining the numbers and characteristics of typical types of landform entities that are developed in Guilin（Guangxi, China）, La Alianza（PR, USA）, Avalton（KY, USA）, and Oolitic（IN, USA）. Five types of landform entities were defined： isolated hill（IH）, clustered hills（CHs）, isolated sinkhole（IS）, clustered sinkholes（CSs）, and clustered hills with sinkholes（CHSs）. An algorithm was developed to automatically identify these types of landform entities by examining the contour lines on topographic maps of two cockpit karst areas（Guilin and La Alianza） and two doline karst areas（Oolitic and Avalton）. Within each specific study area, the CHSs is the least developed type yet with a larger size and higher relief. The IH and IS entities are smaller in size, lower in relief, and outnumber their clustered counterparts. The total numbers of these types of entities are quite different in cockpit and doline karst areas. Doline karst is characterized by more negative（IS and CSs） than positive（IH and IHs） landforms and vice versa for cockpit karst. For example, the Guilin study area has 1192 positive landform entities in total, which occupy 9.81% of the total study area. It has only 622 negative landform entities occupying only 3.91% of the total study area. By contrast, the doline karst in Oolitic has 130 negative while only 10 positive landform entities. The positive and negative landforms in Oolitic occupy 12.68% and 2.61% of the total study area, respectively. Furthermore, average relief and slope of the landform entities are much higher and steeper in the cockpit karst than the doline karst areas. For instance, the average slope of CHs in Alvaton is 3.90 degrees while it is 19.78 degrees in La Alianza. The average relief of CSs is 4.07 m and 34.29 m in Oolitic and Guilin respectively. Such a difference within a specific area or between the cockpit and doline karst may reveal different controls on the development of karst landscape.

The Distribution of Surface Karst Features in the Bakony Region (Transdanubian Mountains, Hungary)

The surface karst of the Bakony Region is described. VES measurements were applied to study the cover and the morphology of the bedrock. A karstmorphological mapping was also performed. A relation was established between the karst types and block types in the mountains. The karstification of the mountains was affected by the block structure of the mountains, the mounds of the uneven bedrock, the presence of superficial deposits and their young denudation. As a result of the above mentioned facts, the karst of the mountains is varied. Soil-covered karst is wide spread in the mountains, but the specific features of this type (solution dolines) only occur on threshold surfaces at the margin of the mountains and on dolomite. The concealed karst was mainly formed on horsts elevated to summit position, but it can also be found on threshold surfaces and on horsts in summit position. Its features are subsidence dolines and depressions of superficial deposit. Cryptokarst and buried karst can be created by gravelly cover or basalt. Where the cover is gravel, epigenetic valleys develop with opened-up phreatic cavities. Where the cover is basalt, ponors develop at its margin, while inside, where the basalt thins out, caprock dolines are formed.