Fruška Gora Mt. as a part of the Pannonian Basin: some important geological remarks


Fruška Gora Mt.

The Fruška Gora mountain represents an E-W extending block, ridge, graben-horst (width  ̴ 15 km, length app. 78-85 km). Crveni Čot is its highest peak, and rises to an altitude of 539 m. The mountain is settled between two subunits: Lower Srem in the south and Bačka in the north. It is situated in the southern part of the Pannonian Basin.

The National Park “Fruška Gora” spreads on the isolated Fruška Gora mountain (25.393 ha). Thanks to the complex geological basement, island character and existence of marine conditions during its long geological history, this hill-mountain in the Pannonian Plain represents an unique natural system. Forests predominate in the range of 90% of all plants. Flora of Fruška Gora consists of more than 1500 species; fauna is very rich, especially ornitofauna with about 200 species of birds, and more than 69 species of mammals.

Because of its specific geographic position (Fig. 1), between the Danube River in the north and closeness to the Sava River in the south, the Fruška Gora mountain was a good area for living for humans from Middle Paleolithic time. Also, in many places on the area of Fruška Gora, traces of human from Neolithic, Roman times, Medieval Period, Austro-Hungarian Empire were found.

Figure 1. Geographic position of Fruška Gora mountain

On the Fruška Gora mountain, of special importance are 35 Serbian Orthodox monasteries built in period from XV to XVIII century (16 of them are active today). Some of them are shown on Fig. 2.

In the National Park “Fruška Gora” special regime of protection there are 25 objects of nature, and in the future is planned to protect also 38 new objects of nature.

Figure 2. Some of monasteries on Fruška Gora mountain: Jazak (left), Krušedol (middle), Staro Hopovo (right)

Geology of Fruška Gora Mt.

The Fruška Gora mountain (Fig. 3), because of its complex geological structure and complicated tectonics, was an object of investigations of many geologists, not only Serbian, but also Hungarian, Austrian etc. Geological investigations started from the end of XIX century (in that time very famous geologists explored this area like A.Koch or G. Pethȍ). Also, the researchers increased investigations during the XX century, especially between the 1st and 2nd World War and during mapping of the Basic Geological Map of Yugoslavia in scale 1:100 000 in the 70ies. In latest time, numerous authors tried to explain the complicated structure of Fruška Gora and gave new interpretations of its geological history.

Figure 3. A. Satellite map of wider area of Fruška Gora Mt. B. Part of Geological Map of SFR Yugoslavia, scale 1:500 000 (1970)

In a geological sense, the Fruška Gora mountain (as block, ridge or horst) is the part of the Vardar Zone Western Belt, built of Triassic to Eocene (Oligocene ?) formations; Neogene sediments occur at all sides and at its flanks.

Four groups of Mesozoic and Paleogene rocks can be separated. The first group, located between Fruška Gora and Srem dislocations, is the Ophiolitic mélange with underlying deposits, where are included: Middle Triassic non-metamorphosed dolomites and lenses of (?)Middle to Upper Triassic low to very low-grade schists and siliceous crystalline limestones (Fig. 4a), which originated from sedimentary and volcanic rocks (as km-long and up to 100 m thick lenses); Upper Jurassic mélange with olistostrome composed of sandstones, diabases, limestones, cherts, gabbros and subduction-related metamorphic rocks (crossite schists, as well as “eclogites” found as pebbles only) in a silty-clayey matrix, and up to several km long serpentinite lenses along E-W stretching faults. The second group, settled on eastern and south-eastern slopes of Fruška Gora, are Jurassic-Early Cretaceous deep-sea sediments (Tithonian-Berrisian). They are represented by interbeds of claystones, siltstones, marlstones and detritic limestones (marlstones contain calpionellids and calcispheres, while detritic limestones contain transported calcareous algae and benthic foraminifers). The third group, named as Campanian-Maastrichtian to Eocene/Oligocene sediments, includes two facies: conglomerates with subordinate breccias, sandstones, shales, marlstones and limestones (Fig. 4b) of Campanian-Maastrichtian age (located between Fruška Gora and Srem dislocations; “Chaotic Blocky Formations”, previously “Srem_Slavonian” type or “Čerević Upper Cretaceous”), and Maastrichtian to Oligocene flysch, as a postcollisional formations (occurs north of Srem dislocation; named also “Bačka-Banat” type or “Stražilovo Upper Cretaceous”). To the forth group belong Latites of Eocene/Oligocene age, which build very shallow Eocene/Oligocene intrusions (around 35 Ma) in different, older and deeper levels of the mentioned flysch.

Figure 4. a. Jazak, Upper Triassic metamorphosed cherty limestones, b. Srednje brdo, Campanian-Maastrichtian red beds

Appearances of metallic and non-metallic deposits and thermomineral waters

It is very important to mention the appearances of metallic and non-metallic deposits and thermomineral waters in the Fruška Gora mountain. The Pb-Zn (less Cu, Ag, Au, Ni) appearances are in connection with Paleogene dacite-andesite-latite subvolcanic intrusions. They are followed by hydrothermal activities, which caused occurence of opals and quartzites (for ex. locality Srebro).

The non-metallic deposits, such as clays, bentonites, limestones, tuffs, marlstones etc., whichmainly use in the construction, are of special interest. In addition, coal occurrences (Vrdnik, Poljana) has already known and exploited earlier.

Occurences of thermomineral waters are mainly on the marginal parts of the mountain, where aquifers lie deep below sediments of Tertiary age (Protić, 1995):

– Spa Ljuba (7 kmsouth of Ilok, is located on the western part of Fruška Gora, h 220 m). It dates from Turkish times (Koch, 1896); water temperature is 22.5 ºС, from Triassic limestone.

– Spa Vrdnik (30 km from Novi Sad, located on the southern part of Fruška Gora, h 190 m; known from Luković, 1931); During the mining, the Tertiary karst formation was penetrated resulting in the thermal water influx of 38 ºC. the temperature of water is 33ºC.  and this place is well known as a thermal spa.

Stari Slankamen. The source of water is on contact of Tertiary sediments and serpentinites at great depth Temperature of water is constant 18.4ºC, with a mineralization of more than 6 g/l, and high concentrations of Na and Cl.

Voda Jazak was found near the monastery Jazak and village Jazački Prnjavor in 1998 during exploration drilling to depth of 128 m in Lower-Middle Triassic sediments; water is with low mineralization (500 mg∕l) and has a very good quality HCO3, Ca, Mg it is used for a water bottling as Jazak water.



Divna Jovanović, Petar Stejić, Rodoljub Gajić
GSS – Geological Survey of Serbia




References:

Dulić, I., Dulić, M. 2018. The Birth of Fruška gora mountain. Institute for Nature Conservation of Vojvodina Province, Novi Sad.

Protić, D. 1995. Mineral and Thermal Water of Serbia, Special Issue of Geoinstitute, Book 33, Belgrade (in Serbian).

Sudar M., Dulić I., Dunčić M., Bogićević G., Rabrenović D., Milovanović D., Mojsić M., Jovanović D., Jovanović R., Banjac N, Gajić V. (Eds.) 2006. Field guide, 1st Int. Workshop „Mesozoic Sediments of Carpatho-Balkanides and Dinarides“ (Novi Sad, 25-30. 5 2006),NIS-a.d. Naftagas-Department of Development, Novi Sad, Center for Earth sciences, Vienna University, Vienna (manuscript), 35-68, Novi Sad (unpublished).

Tasić, Z. 2008. Report: Investigation of heritage of Fruška Gora, its protection and valorization in frame of future geopark. Geological Survey of Serbia, Beograde (unpublished).




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