Resonance frequencies of unconsolidated sediments of the Iska alluvial fan (Ljubljana Moor basin) were derived using microtremor method. Free-field measurements were conducted in a grid with point ...spacing of approximately 250 m. The sediments frequency-thickness relationship, h = 202.97 f.sup.-1.139, was obtained on the basis of 107 microtremor measurements, six existing boreholes that reached the Pre-Quaternary basement and two seismic reflection profiles. The reliance of the obtained relationship was evaluated with the R2 coefficient, which shows a very good level of determination. The resonance frequency map reveals the existence of an N-S oriented deeper buried valley (maximum depth 119 m) in the Western part of the alluvial fan. The microtremor HVSR amplitude map does not show any specific spatial distribution pattern, with the exception of a relatively narrow band of low amplitudes located north of Iska vas. This is probably related to an area of severely fractured bedrock along the Misji Dol fault. Map of the Quaternary sediment thickness and map of the Pre-Quaternary basement topography were constructed on the basis of the established relationship. The basement topography map shows rather steep western slopes of the buried valley down to deepest part, followed by a gradually ascending basement towards the Eastern part of the fan. The comparison of the obtained parameters a and b in frequency-thickness relationship with other sedimentary basins around the world reveals a small variation of b values, and a rather large range of a values, which implies that the parameter a is characteristic for certain geological areas. The results of this research will find use in constructing more accurate hydrogeological models and for assessment of possible sediments-structure resonance effects in seismic microzonation. Keywords: Microtremor method Sediments resonance frequency Frequency-thickness relationship Mapping sediment thickness Iska alluvial fan Ljubljana Moor
The Ljubljana Moor basin is characterized by moderate bedrock topography and thicknesses of Quaternary lacustrine and fluvial sediments ranging from 0 to 200 m. More than 65 boreholes which reached ...the bedrock were drilled in the area, but their distribution in the basin is very uneven and some data from the boreholes uncertain. There are also no data on S-velocity distribution within the basin, but seismic refraction measurements pointed out a rather uniform increase of P-velocity with depth, great impedance contrast with the bedrock and relatively small lateral velocity variations. The microtremor horizontal-to-vertical spectral ratio (HVSR) method was therefore applied as a complementary tool to seismic refraction survey to map the thickness of sediments. First, microtremors were measured at the locations of boreholes which reached the bedrock and the resonance frequencies determined. The inverse power relationship between the resonance frequency and the thickness of sediments was then determined from 53 data pairs. The quality of the correlation is moderate due to possible heterogeneities in sediments and possible 3D effects in some minor areas, but the obtained parameters correspond well to the values obtained in six other European basins. Secondly, a 16 km-long discontinuous seismic refraction profile was measured across the whole basin, leaving uncovered some larger segments where active seismic measurements were not possible. Microtremors were then measured at 64 locations along the same profile, using 250 m point spacing, without leaving any gaps. The frequency–thickness relationship was used to invert resonance frequencies to depths. These were first validated using the results of the seismic refraction survey, which showed good agreement, and finally used for interpolation in the segments of missing refraction data to obtain a continuous depth profile of the bedrock. The study has shown that the microtremor method can be used as a complementary tool for mapping the thickness of unconsolidated sediments also in areas characterized by moderate bedrock topography. As the input data are always to some extent uncertain, it is important to have a sufficiently large number of borehole data to establish a frequency–thickness relationship, as well as some additional independent geophysical information for its validation.
In order to detect recently tectonically active faults, Stream Length-gradient (SL) index and a newly developed method of river gradient analysis were made for three rivers. Two methods were used on ...the southern part of Ljubljana moor, where rivers cross dextral (right-lateral) faults with Dinaric orientation (NW-SE). Watercourse profiles were analysed first, using a »classic«, well established method of SL index. However, this method didn't yield useful results since almost no variability in SL indexes were observed. Additionally, a second newly developed method pointed on the anomalies, which might correspond to the areas of active surface uplift and subsidence as a consequence of active tectonic movements. We compared determined anomalies with the fault lines plotted on the Basic geological map 1 : 100.000 and with the data of radar measurements of vertical movements by PSInSAR method. In this way five potentially active faults, areas of contraction and areas of extension were determined. The results of this research can be used as complementary information for the construction of tectonic model of Ljubljana field and Ljubljana moor.
This paper presents the first comparable overview of different recovery techniques used for waterlogged Neolithic sediments in the surroundings of the Alps in the last decades. Such an investigation ...became necessary because it was not known which parts of plants and types of remains were absent or completely underrepresented due to inappropriate recovery techniques in Slovenian archaeobotany up to 2006. During the 2007 excavation of the approximately 5,200 years old Neolithic pile dwelling site of Stare gmajne, Ljubljansko barje, Slovenia, we compared three methods for the investigation of botanical macroremains: method 1 (M1) included rough wet-sieving and subsequent drying of the fractions; method 2 (M2) rough wet sieving and keeping the fractions wet; and method 3 (M3) washing over and keeping the fractions wet. M3 with gentle washing, systematic subsampling, examination, and sorting of macroremains while wet, as well as using 0.355 mm as the smallest sieve mesh size gave the best results. When using the cruder M2 or M1 methods, waterlogged uncarbonized seeds of taxa such as Linum usitatissimum, Papaver somniferum and Brassica rapa, waterlogged chaff of Cerealia and pericarps of Maloideae and Quercus sp., which are all fragile, were underrepresented or even completely absent and therefore the plant spectra were strongly biased. On the contrary, taxa with lignified seed/fruit walls like Cornus mas, Corylus avellana or Rubus sp. were overrepresented when using the M2 and particularly the M1 method. The application of the M3, instead of the M1 method which has been traditionally used in Slovenian archaeobotany, helped us to identify uncarbonized remains of Linum usitatissimum and various species of Triticum for the first time in a waterlogged Neolithic site in Slovenia. Our study should contribute to a standardization of methods, which is desperately needed in archaeobotany. The study clearly shows that the plant spectra can be strongly biased if inappropriate handling techniques are used. The conclusions hold for all kinds of waterlogged sediments of different periods.
The metal composition of a group of eneolithic copper artefacts from the Ljubljansko barje (Ljubljana Moor) was determined by ICP-AES analysis. Half of the finds come from ...nineteenth century excavations of prehistoric pile dwellings at Ig and the remaining objects were found on the bed of the River Ljubljanica in the twentieth century. The material has been approximately dated to the fourth and third millennia BC. Analysis showed that all the objects are made of copper with various impurity patterns differing in terms of the concentration ratios of arsenic, antimony, nickel, silver and lead. The majority of the artefacts are of a copper type with dominant antimony, copper with domi-nant arsenic was found only in two artefacts. All artefacts also contain lead and silver as trace elements. The results showed that the classification of the metal composition into the copper types that have been identified in the recent German research by means of multivariate analysis was reasonable.
In September 2010, one of the greatest floods in recent decades affected Slovenia, following intense rain between September 16th and 19th. Members of the Anton Melik Geographical Institute of the ...Scientific Research Centre of the Slovenian Academy of Sciences and Arts made their first terrestrial oblique imaging of the floods on Ljubljansko Barje (the Ljubljana moor) from Sv. Ana hill over Podpec on the September 20th, 2010. The floods on the Ljubljana moor, Radensko polje and Dobrepolje were later also covered with handheld imaging made from helicopter on September 23rd, 2010. Terrestrial imaging was made in the time of the highest waters and the imaging from helicopter when the floods were retreating. The floods on Ljubljana moor around Podpec are presented. Images made with the Canon PowerShot SX10 IS non-metric camera were used. The camera was calibrated afterwards, but the calibration data could not be used directly due to not knowing the parameters of zoom in the time of imaging.The flooding boundary was measured from the non-metric images with the interactive orientation of image on the DEM. The results of interactive orientation of non-metric images made with the photogrammetrically derived DEM with a cell size of 5 m ? 5 m and LiDAR derived DEM with a cell size ofl m* 1 mare presented. The evaluation of the method for the 3D data acquisition is also made.
At the eastern margin of the Ljubljansko barje (Ljubljana moor) smaller faults can be seen along which part or the whole colluvial cover is displaced. The age of the colluvium is not determined ...therefore at the moment fault are treated as subrecent. Similar the same phenomenon was seen at the Postojna area.
Abundant archaeological evidence and specific geomorphologic features make the upper course of the Ljubljanica River running through Ljubljana Moor (Slovenia) one of the most interesting rivers in ...Europe. Roman bronze vessels and iron weapons found by chance in the Ljubljanica at Vrhnika, the ancient Nauportus, led the director of the Provincial Museum in Ljubljana, Karel Dežman, to devise a large scale plan for an underwater survey of the riverbed. This, one of the first modern research projects of underwater archaeology was executed in 1884 with the help of divers from the Austro-Hungarian naval base in Pula. Investigations by the Group for Underwater Archaeology and the activities of amateur divers from 1979 onwards revealed distinctly structured distributions of underwater finds on several sites in the upper course of the river indicating possible sacred places with votive offerings and funeral sites, as well as other non-ritual concentrations.
Results of the study show that a combination of isotopic and hydrochemichal methods can be used to obtain new hydrogeological data about the properties of waters in individual aquifers of the ...Ljubljansko barje. An unambiguous distinction was made betweenwaters flowing into the aquifer from the Krim mountains and waters originating in the Gradaščica. It was also possible to identify waters deriving from the karst basin of the Ljubljanica river. The mean altitude of individual waters’ recharge areas was estimatedon the basis of isotopic analyses. The combination with chemical analyses was used to assess the approximate share of carbonate rocks in the aquifer’s recharge area and determine its lithological composition. On the basis of annual changes in the amplitude ofthe isotope signal, also the recharge dynamics of aquifers and the age of observed ground and surface waters were estimated.
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