Geology and hydrogeology of the ^ emernica Mountain Massif , western Serbia

The mountain massif of Cemernica, Western Serbia, is an orogenic feature of the Inner Dinarides. Hitherto, hydrogeological prospecting of the Massif was all on a regional scale, not detailed. Only scanty data, previously collected, were mappable on a scale larger than 1:100 000. The 2005 to 2008 research of the Cemernica Mountain Massif included geological and hydrogeological reconnaissance and mapping, the employment of remote sensing, a geophysical survey, the monitoring of quantitative and qualitative groundwater variation parameters, etc. The groundwaters of Cemernica are a large potential resource of water supply to multiple users. This paper is a contribution to the study of the geology and hydrogeology of the Cemernica Mountain Massif.


Introduction
The mountain massif of ^emernica extends over more than 50 km 2 .Its geology and hydrogeology were explored in detail from 2005 to 2008 and mapped for the first time on a scale larger than 1:100000.The collected data were used to describe the geomorphology, hydrography, geology and hydrogeology of the massif.In addition to internal and external research, some laboratory analyses were made and are reported in the respective chapters of this paper.The identification of the lithostratigraphic units and their spatial relationships, the classification of groundwater bodies and their formation, recharge and discharge mechanisms of the largest karst aquifer are all based on the acquired research data.The qualitative properties in addition to the quantitative aspect of groundwater for the karst aquifer were studied.

Research Concept and Methods
The steps of the geological and hydrogeological investigations in the ^emernica area were the following: • Detailed analysis of the available research data, or identification of the morphologic features and the geological and hydrogeological character of the ^emernica Mountain Massif.• Assessment of relevant climatic factors and hydrologic budget accounting.• Spatial delineation of aquifers.
• Establishment of groundwater occurrence, movement and discharge.• Interpretation of the physical and chemical properties, gaseous, radioactive and microbial compositions of the groundwater.• Quantitative and qualitative assessment of the groundwater and its variation in time.• Groundwater control conditions.
The ]ur~i}a and [titkovo Springs were monitored for one year to evaluate the usability of their waters with low concentrations of mineral matter.
The results obtained by multidisciplinary research of the water from the two springs were the basis for this work.The monitoring at the ]ur~i}a and [titkovo Springs was continuous over the year, while that at the Bursa} and Ku{i}a Springs was periodic.

Geology
^emernica is one of the many carbonate rock areas in the region of Ivanjica and Golija.It belongs to the Drina--Ivanjica fault block (DIMITRIJEVI] & DIMITRIJEVI] 1974), or the former "inner Palaeozoic zone" (PETKOVI] 1961), or "Golija Zone" (AUBOUIN 1974).Previous study of geology of ^emernica has a short history and no published records.
General knowledge of its geology, acquired through mapping and from the base geological map, was used to identify the geologic formations in the field, to study their sedimentological and petrographic nature and structural character.
The mountain massif of ^emernica is composed of rocks formed through two sedimentation cycles.The older, prevailing cycle of the Ivanjica block is the Palaeozoic sedimentation cycle, not exposed everywhere on ^emernica, but lying under all newer formations.The other, Mesozoic cycle, is represented by more than one formation deposited from the Triassic through the Jurassic.

Palaeozoic
Late Palaeozoic rocks, represented by the Bira~ Formation, lie exposed in the deeply eroded Tisovica and Trudova~ka valleys in the area of [titkovo village (DJOKOVI] 1985).
The Bira~ Formation is composed of thin-bedded, laminated siltstones, metasandstones and some limestone lenses.Horizontal and wavy laminae in the siltstone bear ferruginous crusts.Successive on the siltstone is bedded metasandstone with a high proportion of angular quartz.
The stratification and attitude of the siltstone and sandstone in cross-sections indicate frequent turbidity currents, which produced turbidites.
The rocks of the Bira~ Formation were strongly folded and faulted through the Variscan and later Alpine orogenies.The stratigraphic position of the Formation is speculative.It was identified through evidence of the superposition of the subjacent Kovilje conglomerates and the superjacent Kladnica clastics.

Mesozoic depositional cycle
The Mesozoic cycle of deposition produced different formations, more during the Triassic than through the Jurassic.In the ^emernica area, the Kladnica, Bioturbate and Ravni Formations are Triassic, and the Diabase-Chert Formation is Jurassic.quartz grains, quartzite and chert clastics in siliceous cement, reddish-coloured by Fe-minerals.
This time-stratigraphic unit was determined (beyond the limits of the [titkovo village area) as Lower Triassic, based on its few conifer pollen grains.

Bioturbate Formation (T 1 )
A succession of thin-bedded and shaley clay, identified as the Bioturbate Formation (DIMITRIJEVI] et al. 1980) on the Geologic Map Sheet Prijepolje, on the scale 1:50 000, can be recognized under massive limestone of the Ravni Formation in the [titkovo and Trudovo village areas.
New cuttings of a village road near the spring exposed the internal lithologic structure of the Formation, which consists of thin micrite strata and silt and shale laminae.Micrite layers are torn in the sequence and strongly folded together with shale and silt (Fig. 3).
The Formation contains bioturbations of various sizes.Lower Triassic age was determined by its megaand micro-faunal fossils (bivalves and foraminifers).

Ravni Formation (T 2 )
Limestones of the Ravni Formation are most extensive in the ^emernica Mountain Massif, building up a varied surface topology from mountain peaks to karst poljes.The fault block of ^emernica varies in altitude from 110 m SW, where it is thin, to almost 1500 m in the north.
The limestones are slightly recrystallized and dolomitic (Fig. 4).Massive limestones prevail over thick sets of beds in ^emernica, while stratified limestones are recognized only low in the column above springs.
The SW border of ^emernica is steep, produced by an overthrust, and the entire mass of limestone is karstified.The limestone block is thin in the centre, its surface mildly trough -like, like the Ruji{te and Veliko Polje, which allow percolation of surface water and groundwater recharge.
Triassic rocks in the ophiolite belt and its border were taken formerly for exposures of the basal diabase-chert, and Triassic rocks on the SW margin of the Ivanjica Palaeozoic for transgressive, deposited where they still are.It was proved that many Triassic plates, in the form of oligoplacas, lie over the diabase-chert formation, which implies that kilometric limestone plates slid by gravity from the Palaeozoic base into a mélange trough.

Jurassic (J)
A Jurassic ophiolite mélange was recognized in Trudovo area.Its constituents are greywacke, shale, sandstone, limestone, chert and radiolarite.Other rocks of the formation are diabase, spilite, keratophyre, etc. Direct contact of Jurassic rocks and limestones of ^emernica is normally tectonic, extending NW of ]ur~i}i.Rocks of the ophiolite mélange will not be described in detail as they are irrelevant to the mentioned springs.

Photogeology
The task of photogeology was defined as: photographic recording and study of the wider structural pattern of ^emernica: faulting and folding features, lithologic variation, and intensity of karstification within the carbonate rocks extent (unpublished, PAVLOVI] & ^OLI] et al. 2006).
The photogeological interpretation was initially confined to the carbonate extent of ^emernica and its direct contact with the non-carbonated basement, but it was later extended to Carboniferous, Permian and Lower Triassic clastics.The photogeological study eventually included all features of some hydrogeologic relevance.The interpreted aerial photographs covered an area of 54 km 2 .
The sedimentary rocks that build up ^emernica Mountain and its ranges are Lower or Middle Triassic in age.Triassic rocks lie over Permian-Triassic coarse clastics (quartz conglomerate and sandstone) in the northern, southern and south-eastern ranges and over Carboniferous metasandstones in the north-eastern ranges.In the west, the Triassic carbonates of ^emernica are in tectonic contact with Jurassic carbonate and chert of the diabase-chert formation.
Fractures, distinctive morphologic features in the surface configuration, were identified on satellite images of the pattern of fractures (Fig. 5).These are kilometric to decakilometric fractures.Given the size of the study area and the photo and map scales, the identified faults were not classified by importance, even if some of them extend beyond the area limits.These features were classified only in relation to the reliability of identification: observed and inferred.With respect to their expressive morphology, these features may be said to be the factures of neotectonic activity, which may be important in addressing hydrogeological problems.The faults in the ^emernica area are classified into two systems.
The NNE-SSW to E-W systems are particularly well arranged, sub parallel, cutting through ^emernica and extending eastward into Permian-Triassic or Carboniferous rocks.
The other system of kilometric to some decakilometric, the faults have the strike direction NNE-SSW.The morphologic features of these faults suggest that the former system may be more significant for groundwater flow.
A regional fault on the ^emernica western border runs across the entire study area from NNW to SSE, mostly being the contact between Triassic limestones and the older clastics.Several strong springs occur at the cross points of this and the faults in NE-SW strike direction.The regional fault is a complex morphologic feature, of a fault zone type in places.It crosses numerous minor faults where its disruption and displacement are manifested.
The detailed structural pattern and the lithologic units obtained by stereoscopy are given on a photogeological map.The fractures are classified only on the reliability of identification.The carbonate-built ^emernica is densely faulted by hkm-and km-long fractures of two fracture systems: the dominant one with a NE-SW strike direction and the other with a NW-SE strike direction.The systems are conspicuous in the surface configuration, marked by series of elongated sinkholes, short dry valleys or abrupt changes in the slope angle.
Fractures in noncarbonated rocks in the south-eastern and eastern parts of the area control the flow direc-tion or divert it at a right angle.East to west oriented fractures in the SE control largely the surface morphology and possibly also the groundwater flow.
The fault pattern in the easternmost part of the area differs greatly from the carbonate-built ^emernica.Kilometric and decakilometric faults strike dominantly in the N-S direction.Faults in other directions are fewer and shorter.
Morphologic features of hydrogeological interest in ^emernica may be the well-exposed large faults in the strike directions NE-SW to E-W; a complex system on the western border of ^emernica with the occurrences of strong springs and a gravity fault in Ze~ko Polje.

Geophysical Information
Geophysical prospecting was the basic additional exploration for the study of the geology or the type and extent of the lithologic units The measurements were performed in Ruji{te Polje (Fig. 6).
The purpose of the geoelectrical survey was to establish the thickness of the uppermost rock complex, the spatial distribution and depth of each lithologic unit, then to measure the depths to aquifers and to identify faults and fault zones.The method used in the exploration was geoelectrical resistivity sounding in order to estimate the extent and depth of each lithologic unit.Geoelectrical soundings were taken along sections 1 and 2 (Figs.7 and 8), with measurements in eleven sounding points with an AB/2 current electrode separation of up to 300 meters, at the azimuth direction 110°/280°.A symmetrical, Schlumberger array of current and potential electrodes, A-MN-B, was applied.The resistivity measurement results were interpreted both qualitatively and quantitatively.The former covered interpretation of the resistivity plots that show horizontal changes in the electrical resistivity, and the latter, interpretation of the resistivities and thicknesses of the logged formations.The specific electrical resistivity (ρ) and thickness (h) were computerized for each logged lithologic variety.The obtained parameteric values were plotted on sections 1-IPI and 2-IPI, and deep geoelectric sections.
The specific electrical resistivities were measured by geoelectric sounding from ES-1 to ES-11, on which four different lithologies were identified; -Broken Triassic limestone, -Broken Triassic limestone and water?, -Massive or thick Triassic limestone, and -Quartz conglomerate and sandstone.The values of ρ indicated a vertical discontinuity or fault of SW-SE strike direction.
The conclusions based on the geophysical exploration in Ruji{te Polje, ^emernica, are the following: -The lithologic units determined based on specific resistivities are: fragmented Triassic limestone over a water table, water-bearing fragmented Triassic lime-  stone, massive or thick Triassic limestone, quartz conglomerate and sandstone.
-A vertical break or fault in the SW-NE strike direction was registered in both electric profiles based on the values of the parameter r.

Hydrogeology
The water-bearing rocks of the ^emernica Mountain Massif are classified by porosity into the following types (Fig. 9):  • Intergranular aquifer in alluvial deposits of the Tisovica.• Karst aquifer in Middle Triassic limestone (Ravni Formation).
• Fractured aquifer of low potential in Lower Triassic rocks (Bioturbate Formation).There is a fourth type -provisionally "waterless" rocks.The Intergranular aquifer in alluvial deposits of the Tisovica is linear, narrow, directly controlled by a fault that predisposed the Tisovica course.The alluvial deposits of the Tisovica vary in thickness between 6 m and 8 m to 10 m at the most.An aquifer of this type is of minor economic importance for groundwater utilization because its extent is restricted and the water storage is small and variable.
The Karst aquifer of Middle Triassic limestone is centrally located in the Massif area.As limestones occupy almost half the ^emernica area, this type of aquifer is the largest in area and depth.
In terms of groundwater resources, the karst aquifer is the most important in the region.Carbonate rocks formed in the Triassic are also extensive in the Inner Dinarides of western Serbia and traceable over a long stretch in this region.
The mountains of the Dinarides, with few exceptions, extend NE to SW (^emernica, Zlatar, Zlatibor, Tara, Jadovnik, etc.) and are structured largely of Triassic limestones.It follows from all the above-stated that the groundwaters in the aquifers formed by the disolution action -carbonate rocks -are the most abundant in the region.
The principal source of groundwater recharge in the characteristic open hydrogeologic structure of ^emernica is the atmospheric precipitation that falls on limestone outcrops.The high capacity and velocity to respectively receive and transmit atmospheric water are attributed to the geological set-up, structural pattern and degree of karstification.
Groundwater flow, predisposed by the structural pattern, has the general direction from east to west, as indicated by spring flows draining this type of aquifer.The volumes of water discharged by the [titkovo and ]ur~i}a Springs in the west are much higher than spring flows elsewhere in the area.The groundwater flow directions depend, as mentioned before, on faults, factures and karst caverns formed through either tectonic events and/or karstification.
Groundwater in the extensive karst aquifer naturally drains through a number of karst springs.The major springs are [titkovo, ]ur~i}a, Bursa} and Ku{i}a.Their minimum flows vary from 4 l/s to 17.6 l/s ([titkovo and ]ur~i}a) and from 5 l/s to 10 l/s (Bursa} and Ku{i-}a).All springs that drain the ^emernica Karst Massif are contact springs between the permeable Triassic limestone and impervious rocks.Each of the four springs is natural and undeveloped.
Fractured aquifer has a smaller water-yielding capacity and extent than the karst aquifer.It is the most widespread in the NE and W of the considered area.Two major springs ([titkovo and ]ur~i}a) discharge at the contact of the two formations and the Middle Triassic limestones of ^emernica.A smaller area of Lower Triassic, fractured but of lower potential, rocks is located SW of the Bursa} Spring.This aquifer has two sources of recharge.The groundwater in the aquifer of the fractured carbonate and Lower Triassic rocks is replenished by infiltrated atmospheric water and ground water from the adjacent, karst aquifer.The primary flow directions and qualitative properties of groundwater in this type of aquifer have neither been determined, nor can a satisfactory estimate of the water budget be given.
Provisionally "waterless" rock areas are those built up of Jurassic (Malm, Dogger) ophiolitic mélange and Permian-Triassic sedimentary rocks.The rocks identified on the basis of field data as provisionally "waterless" lie in contact with karstified or fractured rocks of low-potential capacity.

Quantitative Groundwater Regime
The total quantity of groundwater involved in the drainage of the ^emernica Massif was monitored at the ]ur~i}a and [titkovo Springs and intermittently measured at the Bursa} and Ku{i}a Springs.Gauging stations were set up for precipitation and hydrologic parameters at the ]ur~i}a and [titkovo Springs in order to obtain representative information for a quantitative estimate of spring flows.The measurements in the ]ur~i}a and [titkovo Springs were taken once in two months, or a total of six measurements in both springs.The measured flows were used to construct flow curves, which were used as the basis for the estimation of other parameters of the flow of the ]ur~i}a and [titkovo Springs (Tab.1).
For a valid analysis of the retention capacity of an aquifer, a new period was necessary of no less than ninety days effective rainfall, resulting in continuous runoff without replenishment (groundwater recession).
An interval of constant runoff or groundwater recession was registered at the [titkovo Spring within the observation period from 30 August 2006 to 9 January 2007.The recession continued for 131 days, an interval of constant runoff without replenishment sufficiently long for analysis.
The considered recession limb of the hydrograph is shown in Fig. 10.Note that there were some ineffective rainfalls in the observation period.
As the maximum to minimum spring flow ratio (Q max : Q min ) was 1 : 3.63 during the groundwater re-cession, the obtained analytical results should be taken with due caution (a reliable ratio by this method should be Q max :Q min =1:10).The recession limb of the hydrograph indicates two different runoff micro regimens.
The obtained runoff coefficients (α 1 = 0.071779 and α 2 = 0.0142) are of the same order of magnitude (α ~10 -2 ), but are different between themselves.The value of the coefficient α 1 indicate higher retentive properties in one micro regimen and the value of α 2 suggests lower retentive properties of karst in the other micro regimen.
The [titkovo Spring flow data from one hydrogeologic cycle were used to calculate the degree of karstification and to determine the dominant groundwater flow directions.The maximum to minimum [titkovo Spring flow ratio (for the whole period) of about eighteen indicated one dominant flow direction, almost certainly controlled by the structural features of the karst aquifer and many minor water paths.
An interval of continuous groundwater runoff, or recession, was registered at the ]ur~i}a Spring during observation of the flow regime from 1 July to 16 October 2008.The recession of the groundwater lasted 108 days and could be used in the analysis.The recession curve is shown in Fig. 11.The value of the coefficient α 1 indicates a higher, and α 2 lower retentive properties in the former and latter micro regimes, respectively.Intermittent rainfalls were ineffective in affecting the groundwater runoff regimes.
As with the [titkovo Spring, the maximum to minimum flow ratio (Q max : Q min ) was less than 1 : 10, specifically 1 : 5.31.The analytical results obtained by the Tarisman method should, therefore, be taken with due caution.

Qualitative Groundwater Regimes
Groundwater from the karst aquifer only was tested for its qualitative properties, because the karst aquifer is much more abundant in water than the others in the region.The tested samples were mainly of the calciumhydrocarbonate (Ca-HCO 3 ) class of water, directly related to the source of origin.Another essential characteristic of the water was comparatively uniform mineral matter in water, not higher than 300 mg/l.
The temperature range of the water is from 6.5° C in the Ku{i}a Spring to 9.3° C in the [titkovo Spring.All spring waters in the area may be assigned to the group of cold waters.Only the water from the Ku{i}a Spring was below the temperature range 7° C to 12° C, considered suitable for human consumption (DRAGI[I] 1997).
The acidity of the water is uniform within the pH range from 7.5 to 8. In this respect, all the waters, except for springs, were neutral to mildly basic.
The specific conductance of the tested groundwater samples was uniform, being within the range from 349 µS/cm (Ku{i}a Spring) to 430 µS/cm ([titkovo Spring).
The mineral matter in the groundwater varied within the range from 225.56 mg/l (Ku{i}a Spring) to 290 mg/l ([titkovo Spring).According to this parameter, the tested samples were low-mineralized groundwater.
The total hardness range was from 11.20° dH (Ku-{i}a Spring) to 12.18° dH (Bursa} Spring).In the classification after Klut, the water of the two springs is moderately hard.In addition to total hardness, the water was tested on permanent and temporary hardness.The difference between total and temporary hardness was very small, indicating a high proportion of carbonate salts, primarily calcium salt, and low proportion of Cl - and SO 4 2-ions.
Sodium and Potassium (Na + +K + ).The sum of the sodium and potassium ion concentrations varies from 0.76 mg/l (]ur~i}a Spring) to 9.96 mg/l (Ku{i}a Spring), the highest being in the latter spring.
Calcium (Ca 2+ ).The dominant cation in the spring waters was the calcium ion, Ca 2+ .All spring waters in the given area therefore belong to the calcium (Ca 2+water group) in the O.A. Alekin classification.The calcium ions are derived from the extensive limestones in the area.The calcium concetration varies from 69.3 mg/l (]ur~i}a Spring) to 86.4 mg/l ([titkovo Spring).
Magnesium (Mg 2+ ).The magnesium ion concentrations, much lower than those of calcium, in the spring water varied from 1.22 mg/l (Ku{i}a Spring) to 4.26 mg/l (Bursa} Spring).
Chlorides (Cl -).Like the sulphates, the chloride concentrations in the spring water samples were very low, varying from 1 mg/l (]ur~i}a Spring) to 12.76 mg/l (Bursa} Spring).
Nitrates (NO 3 -).The nitrate concentrations were very low, far below the maximum allowed concentration.A nitrate ion (NO 3 -) concentration of 5.2 mg/l was detected in the [titkovo Spring water.
Generally, the samples from all springs in the area were of the calcium hydrocarbonate Class, Ca-HCO 3 , with a mineral matter content below 300 mg/l.
The spring waters were cold, neutral to mildly basic and moderately hard.The concentration of the individual elements in the water was below the maximum allowed concentration.The waters tested in the field were clear, without colour, taste and odour.Figure 12 illustrates A graphical presentation of the chemical composition of the tested groundwater (Piper Plot) is illustrated in Figure 12.Other relevant parameters -daily precipitation height, springflow rates and water temperatures -were also monitored over the same period, while the physical and chemical properties of spring water (four full sets of analyses,) were determined quarterly.The inferences are the following:

Conclusions
The Mountain Massif of ^emernica is a structural part of the western-Serbia Inner Dinarides, structured of Palaeozoic and Mesozoic rocks.
The tectonic pattern of the Massif, based on remote sensing information, indicates two dominant strike directions, NNE-SSW to E-W.The whole ^emernica is intersected by faults, which extend eastwards into Permian-Triassic or Carboniferous rocks.The surface features of the faults suggest their being preferential conductors of groundwater.
Middle Triassic limestones form a karst aquifer, the largest in the Massif.
The karst aquifer is an uncovered hydrogeologic structure of known recharge and discharge zones.
The springs that drain the karst aquifer are characterized by high flow rates (Q min 4 to 43.6 l/s; Q max 10 to 495 l/s).
The mean monthly water temperature varies from 8.5° C to 9.9° C.
The ]ur~i}a Spring belongs the calcium hydrocarbonate water group with the content of dissolved solids ranging from 0.2 to 0.3 g/l with a temperature range from 8.6° C to 9.7° C.
The information acquired by geological and hydrogeological research indicates potentially available resources of groundwater for various purposes (water supply, fish ponds, bottling, small power stations).
The results of this research provide for the first time a thorough insight into the water resources in the ^emernica Mountain Massif.
Fig. 10.Analysed recession limb of the [titkovo Spring hydrograph for the runoff period from 30 August 2006 to 9 January 2007.

Fig. 11 .
Fig. 11.Analyse of the recession limb of the ]ur~i}a Spring hydrograph for the runoff period from 1 July to 16 October 2008.
Geological and hydrogeological explorations in the ^emernica Mountain Massif were carried out from 2005 to 2008, through field and laboratory research including stages of hydrogeological reconnaissance and mapping.The groundwater regimes were monitored at the discharge points of the ]ur~i}a and [titkovo Springs over one year, from 1 May 2006 to 1 May 2007.The qualitative and quantitative properties of groundwater were intermittently tested in the Bursa} and Ku{i}a Springs.

Fig. 12 .
Fig. 12. Trilinear diagram of chemical composition of groundwater draining the karst aquifer of ^emernica.