ACTA GGM DEBRECINA Geology, Geomorphology, Physical Geography Series DEBRECEN Vol. 3, 121–125 2008

Basic geomorphological characteristics of the Dinarides Mountain System A Dinaridák f bb geomorfológiai jellemz i András Bognár

University of Zagreb, Department of Geography, Maruli 5ev trg 19., 10000 Zagreb,

Abstract – The mountain system of Dinarides, representing a part of the Alpine-Himalayan mountain belt, was characterized by complex geotectonic development, marked by changing regimes. Geosyncline and especially orogenic evolution stages have played the most significant role in the creation of present structural-morphologic characteristics of Dinaric relief. Namely, specific orogenic development of the area (collision) defined the basic structural-genetic properties of existing morphostructures. Dinarides are typical episubductional mountain systems having domed structure with internal abundance of structural-genetic type of morphostructures: folded, folded-block, domed-folded-block, folded-block-thrust, etc. Three morphostructural zones are identified: Inner, Central and Outer Dinarides. They are mutually different according to properties of their structure as well as the grade of conformity between relief and geologic structure. As a significant element of relief shaped in folded-thrust-nappe morphostructures polygenetic erosional surfaces should be distinguished (so-called karst plateau like South-Istria, Northern Dalmatian-Kistanje, Brotnjo- Dubrave, Zadvarje, plateau around Cista, Imotsko and Sinjsko poljes, etc.). They have fluvial-corrosive origin, but probably have been predisposed additionally by allochtonous tectonics.

Összefoglalás – A tanulmányban a szerz összegzi kutatásait a Dinári-hegylánc morfológiájával kapcsolatban. Az Eurázsiai- hegységrendszer részeként számon tartott hegységívet komplex geológiai-tektonikai szerkezet jellemzi, mely az id k folyamán többször is módosult. A geoszinklinális és orogén folyamatok játszották a legfontosabb szerepet a tipikusan episzubdukciós Dinári-hegység szerkezetmorfológiájának alakításában. A morfostruktúrát gy 9r dések, blokkos feltolódások, töréses-gy 9rt szerkezetek jellemzik, melyek 3 szerkezetmorfológiai régiót alkotnak: a Bels -, Központi- és Küls -Dinaridákat. Geológiájuk, reliefjük és szerkezetmorfológiájuk eltér . A gy 9rt-feltolódásos-takaróred s struktúrákon különféle poligenetikus eróziós felszínek különíthet k el, melyek zömmel fluviális-korróziós eredet 9ek, de vélhet en allochton tektonika is szerepet kapott átformálásukban.

Keywords – Dinarides Mountain system, folded-thrust-nappe morphostructures, polygenetic erosional surfaces, allochtonous tectonism Tárgyszavak – Dinári-hegység, gy 9rt-feltotlódásos-takaróred s szerkezet, poligenetikus eróziós felszínek, allochton tektonika

Introduction

Relief structures are represented by mutually parallel The Inner Dinarides mountain ranges, massifs and ridges, which, owing to the stress interchange in a more recent neotectonic stage The structural-morphologic zone of the Inner (Pliocene, Quaternary), experienced deformations as a Dinarides represents a geo-tectonic and structural- consequence of strike-slip faults, rotations of particular morphologic entity spreading among the Central Alps to blocks and tectonic inversions. In an orographic sense, the north, the Pannonides to the south, the Moravides to these are all linear or arched elevations generally elongated the east, and Central Dinarides to the south-west. In towards the NW-SE. As a step-like outline dominates in structural genetic sense it represents the oldest part of the the transversal profile of elevations, it is evident that the mountain system originating from the Upper Jurassic. This uplift (T>D) and planation (T=

121 ACTA GGM DEBRECINA Geology, Geomorphology, Physical Geography Series Vol. 3 2008

Suvobor 864m, Rudnik 1,132m, 6emerno 1,579m, by the stress change from the direction NE-SW to the 2,017m, etc.) having a predominantly radial and general direction N-S under the influence of faulted arch-radial, and, to a lesser extent, linear (ridges) orography. tectonics and rotation of particular blocks (mountain The shape of the massifs is commonly isometric. In massif of Risnjak, mountain massif of Li 7ko Sredogorje, morpho-tectonic sense, they are classified as folded block- and mountain massif of Poštak). The planated higher thrust mountain massifs belonging to the ophiolitic Dinaric regions of the tallest mountain structures (Dinara and zone (B OGNAR , 1992) On some massifs, denudation levels Velebit) correspond to the remains of a Mesozoic erosional (i.e. pediments) and remnants of poly-genetic plateau surface – the peneplain. As a consequence of the prevailing (Kopaonik, Zlatibor, etc.) are common. The pre-glacial carbonate composition (limestones and dolomites), the modelling, and subsequent glaciation of the highest morphosculpture of the mountain elevation surfaces is mountain zones, was the result of a large-scale uplifting of marked by the domination of various types of karst and the area. Evidence comes from the remnants of the fluviokarst relief. The mountain tops above 1,300 metres corresponding morphologic forms (cirques, moraines, etc.). are characterised by morphologic traces of the Pleistocene The domed folded block-massifs of so called Drina- glaciation (moraines, cirques, glacial waves – the mountain Ivanjica and Vlaši 5-Blizonja anticlinorium are characterised structures of Risnjak, Velebit, Li 7ka Plješivica, Dinara and by a predominantly arch-radial orographic structure, and Kamešnica). they represent a significant structural-genetic element of the mountain zone of the Inner Dinarides. H ERAK in 1991 The Outer Dinarides described them as a remobilised section of the Adriatic- Puglia microplate, due to their allochtonous position; in The Outer Dinarides geotectonic zone comprises reality these massifs consist of a block characterised by a mountain ranges, mountain groups, and mountain ridges of continental basement. Block-folded and block structural- a folded-faulted-imbricated geologic structure. The Dinaric genetic characteristics are typical of the moprhostructures direction (NW-SE) of the mountain structures, the dry found along the flysch zones on the Inner Dinarides, valleys, and smaller basins (pull-apart structures basin of within the south-western limb of the North-Western poljes in karst: Imotsko Polje, Sinjsko Polje, Livanjsko Croatian Basin, northern Bosnia, and northern . Polje, Mostarsko Blato, Krbavsko Polje, Gacko Polje, Eocene flysch sediments deposited in the trough valley, Glamo 7, Grahovsko Polje, Biha 5ka Zavala, etc.) parallel to were partly folded during the younger Palaeogene, being them, prevails. During the neotectonic period, the stress subsequently subdued to strong disjunctive deformations in change (from the direction NE-SW to the direction N-S) the neotectonic stage. Consequently, the formation of caused changes in the expansion direction of certain horsts and horst-anticlinories (Zrinska 616m, Vu 7jak elevations by rotation of blocks into the N-S direction 368m, Trebovac 692m, Majevica 915m, and 626m) (mountain range of U 7ka, range of Promina). The coastal followed. In morphological sense, they are expressed as mountain ranges and the ridges have mainly an low and moderately high massifs having a radial ridge asymmetrical transversal outline. This is in accordance with orography. the dominant reverse tectonics and imbricated structure of In a morphostructural sense, the SW part of the Inner the elevations. Examples are the mountain ranges and Dinarides mountain zone represents a transitional area. It is ridges of Boraja-Vilaja-Opor--Mosor-Perun-Omiška visible through the development of polycyclic compound Dinara-Biokovo-Rili 5 and the ridge of the Central morphostructures. The exhumation of the Hercynian Dalmatia’s interior; here, a carbonate structure with various basement, and re-preparation of the folded zones, took types of karst is common. Dry valleys (in Ravni Kotari) and place along the sections of the platform characterised by a basins (Dicmo, Imotsko-Bekijsko Polje) run parallel with thin carbonate cover. Mountain massifs with domed- the elevations and they are filled with flysch and folded-block structure-genetic properties formed over Quaternary sediments. The present erosional surfaces on those structures during the neotectonic stage, as, for the Dinarides ( Fig. 1 ) can be found at various levels (South- instance, the Bosnian Schist Mountains, which have a Istrian, North-Dalmatian, Zadvar’s, Brotnjo-Dubrava, prevailing radial, radial-arch, and ridge orography (Vranica Lika’s, the erosional surface on Northern Velebit, on the 2,110m, Raduša 1,955m, and Komar 1,510m). During the mountain massifs of 6vrsnica, Bjelašnica, Treskavica, neotectonic stage, faulting of blocks having different uplift Durmitor, etc:); consequently, nearly from sea level to rates took place in the area, with the prevailing thrust cover 1,000m and more than 2,000m above sea-level, they formed a gravitational platforms. Additionally, mountain represent traces of one, once larger, complete, and older massifs and morphostructural ridges with predominantly planation surface. During the neotectonic development folded-block-thrust and block-folded-thrust structure- stage, this surface was intensively disarranged and genetic properties (Bjelašnica 2,066m, Jahorina 1,900m, fragmented, and its surviving sections were transported to Treskavica 2,086m, Viso 7ica 1,927m, etc.) also emerged. various hypsometric positions. Some evidence for this During the orogenic stage nearly all the uplifted mountain model can be deduced by the observation of regionally massifs and ranges were exposed to glaciation and extensive bauxites, which can be treated as correlative periglacial modelling. The morphology of their highest weathering sediments in tropic-equatorial climatic sections is marked by the corresponding glacial and conditions. The existence for such climatic regime has periglacial morphosculpture (Vranica, Bjelašnica, never been proposed for the Cainozoic; consequently, this Treskavica, Zelengora, Magli 5, etc.). In the neotectonic model describes a unique peneplained planated surface of period, besides the typical structure of parallel range the Mesozoic age. sequences, the block mountain massifs were also formed

122 Bognár, A.: Basic geomorphologic characteristics of the Dinarides… GENERAL GEOMORPHOLOGY

Figure 1 Erosional surfaces and pediments in the mountain zone of the Outer Dinarides. A. Parts of the erosional surfaces of the Mesozoic age 1. Fragments of denudational erosional surface on autochthonous structures (Adriatic platform) – exhumed and disturbed during the Tertiary and Quaternary – several times exposed to denudational processes during the younger Palaeogene and in Neogene (South Istrian erosional surface). 2. Fragment of erosional surface on allochthonous structures

21 Fragments of denudational erosional surfaces – disturbed in the Palaeogene, Tertiary and Quaternary and exposed to repeated denudational processes during particular time intervals of the quoted geologic periods with traces of partly exhumed peripedimentation (erosional surfaces Brotnja, Dubrava, etc.).

22 Fragments of denudation-accumulation planation surfaces – disturbed and partly exhumed, as well as exposed to the repeated denudational planation processes with peripedimentation traces – less expressed relative relieves (Northern Dalmatian erosional surface).

23 Fragments of denudational planation surfaces – intensively disturbed and elevated to various heights above sea-level with a prominent relative relief (even to 300m/km 2) – exposed to the repeated denudational processes during the Tertiary and Quaternary with traces of pedimentation, probably exhumed (most of high erosional surfaces). B. Younger pediments formed by the end of the Miocene, and with the traces of the Quaternary denudational planation processes in the Pliocene – partly disturbed and destroyed – elevated to various heights. C. Uplifting 1. ábra Eróziós felszínek és pedimentek a Küls -Dinaridák hegységi zónájában. A. Mezozóos eróziós felszínek 1. Dnudációval átformált, a harmad- és negyedid szakban exhumált eróziós felszínmaradványok Autochton szerkezeteken (Adriai-platform), melyek a paleogén végén és a neogén során többször voltak kitéve denudációs folyamatoknak (dél-isztriai eróziós felszín). 2. Allochton szerkezeteken kialakult eróziós felszínmaradványok 21 Paleogénben, a harmadid szakban és a negyedid szakban bolygatott, majd az említett korokban ismételt denudációs folymatoknak kitett és szemiexhumált, peripedimentáció nyomait mutató denudációs felszínmaradványok (Brotnja, Dubrava eróziós felszínek stb).

22 Denudációs-akkumulációs elegyengetett térszínek maradványai, részben exhumáltak, bolygatottak és ismételt denudációs folyamatoknak voltak kitéve peripedimentációs nyomokkal (észak-dalmáciai eróziós felszín). 23 Denudációval elegyengetett felszínmaradványok, intenzíven átformált és különböz magasságokba kiemelt, helyenként igen jelentékeny relativ relieffel (akár 300m/km 2) bíró felszínek a harmad- és negyedid szak során ismételt denudációs folyamatoknak kitéve, feltehet en exhumált magas eróziós felszínek. B. Miocénben kiformálódott pliocén elegyengetés által érintett, részben megsemmisült, különböz magasságokra kiemelt fiatal pedimentek. C. kiemelkedés

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Figure 2 Morphological and structural genetic profile of Dinarides range 2. ábra A dinári vonulat morfológiai és szerkezeti genetikai szelvénye

Erosional surfaces can be observed on the majority of Dinarides mountain zone. These are characterised by a the mountain ranges and massifs of folded-thrust and specific step-like outline of their transversal profiles ( Fig. folded-imbricated structural-genetic material in the Outer 2). This scenario supports their complex geomorphologic

124 Bognár, A.: Basic geomorphologic characteristics of the Dinarides… GENERAL GEOMORPHOLOGY evolution marked by the alternation of uplift stages with M. Srakane, Cres, Lošinj, Plavnik, Rab, Krk and Prvi 5) into those of relative tectonic inactivity favourable to a fan-shaped (radial) extension outline. denudational-planation processes, relations proved by the existence of two clearly marked steps-pediments. Conclusions Exceptions are the fragments of older erosional levels, i.e. the surface, which are, in view of their morphologic The mountain system of Dinarides, representing a part position, connected with the mountain ranges’ tops and of Alpine-Himalayan mountain belt, was characterized by massifs, then with the parts of the karst poljes bottoms, the complex geotectonic development, marked by changing marginal parts of the Outer Dinarides towards the Adriatic regimes. Geosyncline and especially orogenic evolution basin, and with the Pannonian basisn. stages have played the most significant role to creation of The mountain ranges, massifs, and the mountain present structural-morphologic characteristics of Dinaric groups of folded-faulted-thrust geologic structure of the relief. Namely, specific orogenic development of the area Dinaric mountain system were formed during the Alpine (collision) was defined the basic structural-genetic orogeny. In geotectonic sense, they represent a part of the properties of existing morphostructures. Outer Dinarides zone. It is important to note the prevailing Dinarides are typical episubductional mountain system specific Dinaric direction (NW-SE) of the expansion of having domed structure with internal abundance of mutually parallel, linearly elongated or arched mountain structural-genetic type of morphostructures: folded, folded- elevations (Risnjak – V. Kapela – M. Kapela – Li 7ka block, domed-folded-block, folded-block-thrust, etc. Three Plješivica; Uilica – Dinara – Kamešnica; Tuhobi 5 – morphostructural zones are identified: Inner, Central and Medve Gak – Kobiljak – Range of Veljun – Velebit; Kozjak Outer Dinarides. They are mutually different according to – Svilaja), and intermontane basins and uvalas. Generally, properties of their structure as well as a rate of conformity we find a strong relation between the orographic and between relief and geologic structure. As a significant geologic structure (elevations-anticlines, anticlinoria; element of relief shaped in folded-thrust-nappe recesses – synclines, depressions, synclinoria), but some morphostructures polygenetic erosional surfaces should be deviations of discomforming features have also been distinguished (so-called karst plateau like South-Istrian, determined (elevations – synclinorium of Dinara and Northern Dalmatian-Kistanje, Brotnjo-Dubrave, Zadvarje, Svilaja, successions of the upper Cetina flow basins – plateau around Cista, Imotsko and Sinjsko poljes, etc.). anticline –anticlinorium). The insular relief of the NE part They have fluvial-corrosive origin, but probably have been of the Adriatic Sea maritime zone commenced during the predisposed additionally by allochtonous tectonics. post-Pleistocene by glacio-eustatic rising of the sea level by around 100 metres. Geo-tectonically, it belongs to the zone References of the Outer Dinarides with a prevailing folded-faulted- imbricated geologic structure. An identical folded-block- BOGNAR , A., 2001: Geomorphological Regionalisation of imbricated geologic structure was mainly comfortably Croatia. Acta Geographica Croatia, 34 reflected in the relief. The Dinaric direction (NW-SE) BOGNAR , A., 1992: Basic Structural-Morphological dominated the extension of the islands, the mutually Characteristics of the Dinarides. – Proceedings of the parallel mountain ridges, and the ranges formed on them, international symposium “Geomorphology and Sea” as well as those dry valleys and basins which consequently and the meeting of the Geomorphological became channels, bays, gulfs, and straits as a result of sea Commission of the Carpatho-Balcan Countries, transgression in the post-Pleistocene. In the neotectonic Department of Geography, Faculty of Science period, the stress change from the NE-SW direction to the HERAK , M., 1991: Dinarides – Mobilistic View of the general N-S direction, and rotation of certain smaller Genesis and Structure. Acta Geologica, 21, tectonic blocks, resulted into the change of the expanding PÉCSI , M., (special consultant Bognar, A.) 1975: direction of some relief entities: the Central Adriatic Islands Geomorphological Map of the Carpathian and (the islands of Drvenik, Šolta, Bra 7 and Hvar – so called Balcan Regions (1:1.000 000). – Geographical Block of Hvar) to the E-W direction, a part of the Research Institute of Hungarian Academy of Dalmatian Island to the E-W and WNW-ESE direction Sciences, Budapest. (Kor 7ula) (Mljet), and the Kvarner Islands (Unije, V. and

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