Quaternary Deposits As the Hydrogeological System of Eastern Slavonia
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GEOL. CROAT. 52/2 141 - 152 7 Figs. ZAGREB 1999 Quaternary Deposits as the Hydrogeological System of Eastern Slavonia Andrea BAÈANI 1, Marko ©PARICA 2 and Josipa VELIÆ 1 Key words: Hydrogeological system, Watershed, Kljuène rijeèi: hidrogeolo¹ki sustav, razvodnica, lito- Lithological continuity, Fault zones, Transmissivity, lo¹ki kontinuitet, rasjedne zone, transmisivnost, rav- Plateau, Eastern Slavonia, Croatia. njak, istoèna Slavonija, Hrvatska. Abstract Saæetak The area of eastern Slavonia, situated between the Drava and U prostoru istoène Slavonije, izmeu Save i Drave nalaze se tri Sava rivers, comprises three geotectonic units: the eastern part of the geotektonske jedinice i to na sjeveru istoèni dio Dravske potoline, na Drava depression in the north, part of the Slavonia-Srijem depression jugu dio Slavonsko-srijemske potoline, a izmeu njih Ðakovaèko- in the south and the central Ðakovo-Vinkovci plateau together with vinkovaèki i Vukovarski ravnjak. Ravnjaci su u morfolo¹kom i struk- the Vukovar plateau. These units are separated by deep faults that turno-tektonskom pogledu sloæene timorske strukture, koje su od sus- reach the base of the Tertiary sediments. The first 200 m of Quater- jednih potolina odvojene sistemima dubokih rasjeda koji zadiru u nary deposits are saturated with fresh water. The aim of this study podlogu tercijarnih sedimenata. Zbog morfologije terena se duæ was to find out whether the faults form impermeable boundaries sepa- pruæanja Ðakovaèko-vinkovaèkog i Vukovarskog ravnjaka proteæe rating the waterbearing deposits into independent hydraulic systems, povrπinska i podzemna razvodnica koja istraæivani prostor dijeli u dva or if a singular hydraulic entity exists. Results of the analysis indicate sliva: Dravski na sjeveru i Savski na jugu. Cilj ovog rada bio je that lithological continuity of the aquifers exists along the fault zones istraæiti da li rasjedne zone izmeu ravnjaka i potolina predstavljaju on the margins of the Ðakovo-Vinkovci and the Vukovar plateaux, nepropusnu granicu koja naslage dijeli u dva odvojena hidraulièka which means that there is no impermeable hydraulic boundary on the sustava ili one Ëine jednu hidrauliËku cjelinu. Analizom su obuhvaÊe- watershed between the Sava and Drava river valley. The part of east- ne kvartarne naslage koje sadræe vodu pogodnu za vodoopskrbu, a ern Slavonia between the Sava and Drava rivers is one hydraulic sys- koje zalijeæu do dubine od 200 m. Rezultati analize pokazali su da tem consisting of zones with different transmissivity values. In the litolo¹ki kontinuitet vodonosnih slojeva duæ rasjednih zona Ðako- zones of reduced transmissivity, the hydraulic connections are weak- vaèko-vinkovaèkog i Vukovarskog ravnjaka nije prekinut, te da na ened, but not broken. Such zones exist not only along the fault zones razvodnici savskog i dravskog sliva ne postoji nepropusna hidraulièka of the Ðakovo-Vinkovci plateau and the Vukovar plateau, but also granica. Prostor istoËne Slavonije izmeu Drave i Save smatra se jed- within the Sava and Drava depressions. The terrain morphology influ- nim hidraulièkim sustavom unutar kojeg postoje zone s razlièitim vri- enced formation of both the surface and the underground watershed, jednostima transmisivnosti. Duæ zona smanjene transmisivnosti parallel to the extension of the Ðakovo-Vinkovci and Vukovar hidraulièke veze su oslabljene, ali nisu prekinute. Takve zone nisu plateau. Therefore, within this single hydraulic entity, when the draw- prisutne samo duæ rasjednih zona Ðakovaèko-vinkovaèkog i Vuko- down reaches the watershed due to excessive pumping, the watershed varskog ravnjaka nego i unutar pojedinih depresija. U sluèaju da will be displaced from its natural position. sniæenje uzrokovano crpljenjem dosegne razvodnicu zapoèinje dotok vode iz podruèja s druge strane razvodnice, tj. razvodnica se premi- jeπta u odnosu na prirodni poloæaj udaljavajuÊi se od mjesta crpljenja. 1. INTRODUCTION of complex horst structures, that are separated from the neighbouring depressions by systems of deep faults The eastern part of the Drava depression in the (Figs. 1 and 2). With respect to the surface water and north and part of the Slavonia-Srijem depression in the groundwater, two drainage areas are defined - the Drava south, divided by the central Ðakovo-Vinkovci plateau drainage area in the north and the Sava drainage basin together with the Vukovar plateau, are deeply subsided in the south. The surface and subsurface watersheds structural depressions which were formed along region- between these two areas are located on the Ðakovo- al faults characterised by the horizontal displacement Vinkovci and the Vukovar plateaux. and movement of coherent tectonic blocks to the north- For construction of the geological map shown in east, which influenced the formation of large extension Fig. 1, the following sheets of the Basic Geological Map of SFRJ Scale 1:100,000 were used: Donji Miho- zones. The plateaux have the morphology and structure ljac (HEÆIMOVIÆ, 1985), Na¹ice (KOROLIJA & JA- MIÈIÆ, 1989a), Osijek (MAGA©, 1987a), Odæaci 1 Faculty of Mining, Geology and Petroleum Engineering, University (TRIFUNOVIÆ & STOJADINOVIÆ, 1985), Slavonski of Zagreb, Pierottijeva 6, HR-10000 Zagreb, Croatia. Brod (©PARICA, 1987), Vinkovci (BRKIÆ et al., 1 Institute of Geology, Sachsova 2, HR-10000 Zagreb, Croatia. 1989), Baèka Palanka (ÈIÈULIÆ-TRIFUNOVIÆ & 142 Geologia Croatica 52/2 Fig. 1 Geological map. Baèani, ©parica & VeliÊ: Quaternary Deposits as the Hydrogeological System of Eastern Slavonia 143 Fig. 2 Geological cross-sections A-A’ and B-B’. GALOVIÆ, 1985a), Brèko (BUZALJKO et al., 1987) and the radioactive logs) were correlated in a north- and Bijeljina (VRHOVÈIÆ et al., 1986). The structures south direction in order to depict the lateral relation- and other tectonic data were compiled after the works ships of the plateau sediments to the depressions. Due of HERNITZ (1983) and PRELOGOVIÆ et al. (1995). to the fact that there is a limited number of wells in the The aim of the study was to determine whether the marginal zones, the data set was complemented with fault zones between the plateaux and depressions con- interpretation of geoelectric measurements. The results stitute an impermeable zone that separates the Sava and obtained by utilisation of the mathematical models that Drava drainage area into two hydraulic systems, or covered the marginal zone were also taken into account. whether a singular hydraulic entity exists. The shallow- est 200 metres of sediments favourable for water-sup- ply were explored. 3. RESULTS The results of comprehensive analyses of all the 2. DATA-SETS AND METHODS data that were at our disposal, originating from the sources mentioned above, can be grouped in accor- The work is largely based on the analysis of geolog- dance to the scientific disciplines - geological (strati- ical and hydrogeological data that were published in graphic, tectonic and palaeogeographic), hydrogeologi- scientific and professional papers and books, as well as cal and hydraulical data. Their synthesis solved the on the numerous reports in the archives of several com- problem of the continuity of the aquifer layers in the panies and scientific institutions. These data were inter- studied area of a relatively complex geological struc- preted together with fieldwork and laboratory investiga- ture. tions of the sediments drilled in 518 wells. The most important data obtained from the wells were the total 3.1. QUATERNARY GEOLOGICAL EVOLUTION depth, depth-intervals of permeable layers and the ratio of the thickness of permeable and impermeable layers. In view of the water-supply possibilities, the most The following hydrogeological parameters of the wells interesting sediments were deposited during the Middle were calculated: average hydraulic conductivity, trans- and Upper Pleistocene. This is the reason why this missivity, storage coefficient and leakage coefficient. overview of the geological history only covers the Qua- The drilling data and the well-logs (primarily the E-logs ternary period. 144 Geologia Croatica 52/2 In northern Croatia, there is a continuation of like their transport capabilities, and by the shallowing of the depositional environments between the Pliocene depositional area. The wind forces took the dominant (Uppermost Tertiary) and the Quaternary, the Pliocene role in the transport of sedimentary material, while silt being characterised by large aquatic areas with sedi- and clay were deposited in the remaining lakes and ments of significant thickness, especially in the subsid- swamps. In some places, the aquatic environments ing depressions. It also means that the Pliocene - P l e i s- totally dried up which enabled the formation of palaeo- tocene boundary has not yet been defined with confi- sols. The related palaeogeomorphological circumstan- dence. Subsequent to the strong tectonic events bet- ces are explored, documented and explained in the ween the Pliocene and Quaternary, and to the break- works of VELIÆ & DURN (1993) and VELIÆ & SAF- through of the Danube in the Ðerdap canyon, the lakes TIÆ (1996). and swamps gradually dried up, followed by formation The aforementioned depositional environments are of the drainage pattern. There are only scarce data on confirmed by fossil findings. The ostracods significant the Lower Pleistocene of the explored area. There are for the shallow stagnant waters were determined by no outcrops. The age was proved by fossil findings in a SOKAÈ (1976), SOKAÈ & HARTEN (1978), SOKAÈ