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Dolines are considered to be among the most prominent karst formations, which is why they can serve as diagnostic forms of karst. Their spatial distribution and density are important indicators of an area’s degree of karstification, as well as of an overall geomorphological development. The aim of this paper is to determine the spatial distribution and the density of dolines, and also to analyse the influence of geological structure and morphometric features of the terrain (hypsometry, slope inclination, relative relief) on the spatial distribution of dolines in the area of southeastern Velebit. Moreover, for the first time with regards to the Croatian karst, the spatial distribution of dolines was compared with the spatial distribution of entrances into caves in the southeastern Velebit’s area of Crnopac. The data on the dolines’ position were adopted from 1:25,000 scaled topographic maps. All data were digitalised and analysed with ArcGIS 10.1 software in the GIS laboratory of the Geographic Department of the Faculty of Science in Zagreb. The research showed a strong influence of morphometric parameters of the relief on dolines’ density. The most prominent occurrence of dolines is linked with the areas ranging from 1000 to 1200 meters of altitude, slope inclination lower than 2° and the relative relief of 100 – 200 m per km2. Furthermore, the highest density of dolines was recorded in the Jurassic carbonate layers, while it was determined that the zones of main faults do not have a significant influence on the increase of dolines’ density. A high degree of correlation was determined by comparing spatial distributions and density of dolines and entrances into caves.

Ponikve pripadaju među najznačajnije krške oblike koji se stoga smatraju i dijagnostičkim oblicima krša. Njihov prostorni raspored i gustoća važan su pokazatelj stupnja okršenosti nekog prostora, ali i njegova cjelokupnoga geomorfološkog razvoja. Cilj ovoga rada je utvrditi prostorni raspored i gustoću ponikava te analizirati utjecaj geološke građe i morfometrijskih karakteristika terena (hipsometrija, nagib padina, vertikalna raščlanjenost) na prostorni raspored ponikava na području jugoistočnog Velebita. Prvi je put na području krša Hrvatske uspoređen prostorni raspored ponikava s prostornim rasporedom ulaza u speleološke objekte i to samo na dijelu jugoistočnog Velebita – Crnopcu. Podaci o položaju ponikava preuzeti su s topografskih karata 1:25 000. Svi podaci su digitalizirani i računalno analizirani s pomoću ArcGIS 10.1 programskog paketa u GIS laboratoriju GO PMF-a u Zagrebu. Istraživanjem je ustanovljen snažan utjecaj morfometrijskih parametara reljefa na gustoću ponikava. Najznačajnija pojava ponikava vezana je za područja nadmorskih visina 1000 – 1200 m, nagiba padina manjeg od 2° i vertikalne raščlanjenosti reljefa 100 – 200 m/km2. Također, najveća gustoća ponikava zabilježena je u karbonatnim naslagama jurske starosti te je utvrđeno da zone glavnih rasjeda nemaju značajniji utjecaj na povećanje gustoće ponikava. Usporedbom prostornog rasporeda i gustoće ponikava i ulaza u speleološke objekte utvrđen je njihov visok stupanj korelacije., Dolines are considered to be among the most prominent karst formations, which is why they can serve as diagnostic forms of karst. Their spatial distribution and density are important indicators of an area’s degree of karstification, as well as of an overall geomorphological development. The aim of this paper is to determine the spatial distribution and the density of dolines, and also to analyse the influence of geological structure and morphometric features of the terrain (hypsometry, slope inclination, relative relief) on the spatial distribution of dolines in the area of southeastern Velebit. Moreover, for the first time with regards to the Croatian karst, the spatial distribution of dolines was compared with the spatial distribution of entrances into caves in the southeastern Velebit’s area of Crnopac. The data on the dolines’ position were adopted from 1:25,000 scaled topographic maps. All data were digitalised and analysed with ArcGIS 10.1 software in the GIS laboratory of the Geographic Department of the Faculty of Science in Zagreb. The research showed a strong influence of morphometric parameters of the relief on dolines’ density. The most prominent occurrence of dolines is linked with the areas ranging from 1000 to 1200 meters of altitude, slope inclination lower than 2° and the relative relief of 100 – 200 m per km2. Furthermore, the highest density of dolines was recorded in the Jurassic carbonate layers, while it was determined that the zones of main faults do not have a significant influence on the increase of dolines’ density. A high degree of correlation was determined by comparing spatial distributions and density of dolines and entrances into caves.

The Velebit Mountain spreads along the Adriatic sea between Senj in the North West and the Zrmanja river in the South East. Velebit is a Dinaric Mountain consisting mostly of carbonate rocks. Main characteristic of its sea slopes are scarce resources and aridity, which affected land use and settlement positions during prehistory. Although the Velebit Mt. is a very hard area to live in, people have made great efforts during the past to shape the landscape in order to survive. The karstic nature of the Velebit Mountain with its unique micro morphological traits, impedes prehistoric cultural landscape research and makes it difficult to detect and study the sites. In this talk we will present land use research methods in the difficult landscapes of the Velebit Mt., as well as new results.

This paper analyses for the first time the influence of glaciation on underground karst landforms in the Croatian part of the Dinarides, as well as the interrelation between underground and surface relief developments under glacial conditions. The karst environment, as a good recorder of palaeo-environments, provides some new information on Quaternary glaciation in the Velebit Mountain in Croatia, and reveals, generally, the morphogenetic evolution of Štirovača Ice Cave (in Croatian, "Ledenica u Štirovači") and of the surrounding area. During cold periods, glacial exaration produced a particularly significant quantity of sediments. Consequently, underground karst conduits situated below the snow line during the Pleistocene were filled with high-energy sedimentary structures, glacial and fluvioglacial sediments. This reduced or even stopped their conduit function, and led to difficulties in the drainage of meteoric water, to lake formation within morphological depressions and to a rise in the local water-table level. With the denudation of these deposits, conduit reactivation and a drop in the underground water level occurred. Stabilisation during milder climatic conditions led to aggradation of the cave and to the deposition of flowstones from 8230 ± 150 years BP.

The Baške Oštarije karst polje is stretching out at the direction E - W at lenght of 3,75 km, while the width is varying from 0,25 to 2,0 km. It divides central from the south part of the Velebit mountain and it is formed at the contact of two orographic wholes. Besides karst and fluvio-karst processes, the derasion and periglacial processes have been most expressed at the relief formation. The water which flows down from edge parts of polje has great importance in relief formation because of its corrosional aggressivity., Zavala Oštarijskog polja u kršu proteže se u smjeru I – Z u dužini od 3,75 km, dok širina varira od 0,25 do 2,0 km. Ovo polje dijeli središnji od južnog dijela Velebita i oblikovano je na kontaktu dvije orografske cjeline. U oblikovanju reljefa najizraženiji su, uz krški i fluviokrški, i derazijski i periglacijalni procesi. Voda koja dotječe s rubnih dijelova polja zbog svoje korozijske agresivnosti ima veliku važnost u oblikovanju reljefa.

The new data showed that age of this ice part is at bottom about 58, 000 years old, and near of top of this ice part is about 560 years old.

The first approach to the relationships between societies and physical environments on Velebit Mountain shows narrow correlations between spatial distribution of dolines, soil formation, hydric resources, vegetation and land occupation. In 2002, sediment cores have been obtained from different dolines of Velebit Mountain to evaluate the potential of their sedimentary archives in order to reconstruct the landscape history. On the littoral slopes and on the top parts of the mountain, the dolines were difficult to dig due to the presence of rocks in depth. Nevertheless, the cores have been sampled and soil analyses have been made (physical and chemical analyses: colour, grain size, pH, CaCO3, C, N, P, K, Mg, CEC). No dating materials were found. The first results attest to rather homogeneous pedologic processes in each area studied (Kamenica, Stinica, Baske Ostarije and Bilensko Mirevo), but they also indicate colluvial contributions. These contributions differ from one doline to another according to their location and morphology. Dolines reveal themselves to be not very good traps, as the representative nature of their sedimentary archives could be very local. However, the best profile has been obtained at Bilensko Mirevo, which shows a change in the soil nutrient content from an impoverishment in its middle part toward an increase of the soil nutrients in recent parts. Those environmental changes could not be precisely dated, but could be correlated with the 17th to 20th century phase of strong human impact on the Velebit environment and with the rural depopulation observed since the second half of the 20th century. Keywords: karst, dolines, Mediterranean soils, Velebit Mountain, Dinarides, Croatia.

The influence of tectonic forces on the karst relief development has been studied using dolines as geomorphological markers. The strain and stress orientations have been calculated from the doline distribution applying the centre to centre method.

The influence of tectonic forces on the karst relief development has been studied using dolines as geomorphological markers. the strain and stress orientations have been calculated from the doline distribution applying the centre to centre method. 623 local results have been obtained which were later injected into 2D finite element model cretaed in Castem 2000 software.

The relation between geological structure and landforms has always been an important subject in geomorphology, but, in the last few decades, the plate tectonic theory has strongly increased the interest in this subject. Many researchers have focussed their attention on the influence of active tectonism on landform development. As the style and location of landform development are determined by the type, location and rate of tectonic movements and their associated stress field (Brunsden, 1990) the aim of this work is the determination of the relation between the karstic relief forms and tectonic processes. We wanted to discover to what extent the tectonic movements influence the development of karst relief and in what measure these influences can be studied from relief. Stress has been invoked in explanation of a number of minor forms, developed mainly in granite (e.g. Jennings and Twidale, 1971), but also in other lithological settings. From this, two questions arise : Can the stress and strain be measured from relief ? Can the deformation rate be measured from relief ? The analyses were applied to the Velebit mountain range which is a typical karstic area. It is a part of the Outer Dinarides, which is in turn a part of the Adriatic-Eurasia collision zone. Its numerous specific relief forms and the recent tectonic activity make the Velebit mountain range pertinent for such analyses. In the karstic domain, dolines can be used as a sensitive indicator of tectonic activity. Even if the development of dolines is primarily the consequence of the rock nature and climatic conditions, its spatial repartition is basically determined by the geological structure. The spatial analysis of dolines allows us the measurement of strain and stress to which the studied area has been submitted during recent periods.