Jurassic pelagic succession of NW Croatia &#8211; a key to better understanding tectonic setting of the Southern Alps &#8211; Dinarides transition zone
Authors: Vukovski Matija , Kukoč Duje , Grgasovic Tonći , Fuček Ladislav , Slovenec Damir 
Published: August 2022

&lt;p&gt;Ivan&amp;#353;&amp;#269;ica Mt. is an inselberg in the transitional area where S-verging Southern Alpine structures overprint NNW-verging Dinaric structures (van Gelder et al. 2015, and references therein). It is composed of Triassic to Cretaceous shallow to deep-marine sedimentary succession of the Adriatic continental passive margin (&amp;#352;imuni&amp;#263; et al. 1976), overthrust by ophiolitic m&amp;#233;lange (Babi&amp;#263; et al. 2002). Early Cretaceous siliciclastic flysch-type deposits continuously overlaying pelagic limestones clearly indicates distal position of these successions on the continental margin. However, so far complete Jurassic succession on Mt. Ivan&amp;#353;&amp;#269;ica was never found, causing different interpretations of its Mesozoic history. Babi&amp;#263; (1974) assumed the existence of Jurassic pelagic succession on top of the Late Triassic shallow-water carbonates, describing up to few meters of Early to Middle Jurassic condensed pelagic limestone overlain by Late Jurassic radiolarian cherts and pelagic limestones. Contrary, &amp;#352;imuni&amp;#263; et al. (1976) assumed shallow-marine conditions throughout the Early Jurassic followed by emersion until latest Jurassic. Our study revealed for the first time complete shallow-water to pelagic Jurassic succession on Mt. Ivan&amp;#353;&amp;#269;ica.&lt;/p&gt;
&lt;p&gt;Southern slopes of Ivan&amp;#353;&amp;#269;ica Mt. are mostly built of ophiolitic m&amp;#233;lange, except for prominent hills built of the Late Triassic Dachstein limestone, which were so far interpreted as klippes (&amp;#352;imuni&amp;#263; et al. 1976), or olistoliths (Babi&amp;#263; &amp; Zupani&amp;#269; 1978). Our new data indicate continuous succession on top of Dachstein limestones composed of shallow-marine carbonates, represented by intraclastic-peloidal packstones to grainstones, gradually transitioning to wackestones with pelagic influence. The onset of pelagic sedimentation took place around the end of the Early Jurassic when thin bedded marls, shales, marly limestones with intercalated fine-grained calciturbidites were deposited. Higher in the succession Callovian to possibly early Tithonian radiolarian cherts are overlaid by calcarenites, late Tithonian to Early Cretaceous pelagic limestones and Early Cretaceous flysch-type deposits.&lt;/p&gt;
&lt;p&gt;Discovery of the Jurassic pelagic sediments allows for a new interpretation of structural relations on the Ivan&amp;#353;&amp;#269;ica Mt. In our opinion occurrence of Dachstein limestone, previously interpreted as klippes or olistoliths represent an imbricate fan. Because the Southern Alps thrust front in this area was interpreted according to these mapped klippes and nappe contact, our findings may also have an impact on the redefining of the easternmost Southern Alps thrust front.&lt;/p&gt;
&lt;p&gt;&amp;#160;&lt;/p&gt;
&lt;p&gt;Babi&amp;#263;, Lj. (1974). Jurassic&amp;#8722;Cretaceous sequence of Mt. Ivan&amp;#353;&amp;#269;ica (North Croatia). &lt;em&gt;Bull. Sci. Cons. Acad. Yugoslav.&lt;/em&gt; (A), 19/7&amp;#8722;8, 180&amp;#8722;181. Zagreb.&lt;/p&gt;
&lt;p&gt;Babi&amp;#263;, Lj. &amp; Zupani&amp;#269;, J. (1978). Mla&amp;#273;i mezozoik Ivan&amp;#353;&amp;#269;ice. In Babi&amp;#263;, Lj. &amp; Jelaska, V. (ured.): &lt;em&gt;Fieldtrip Guidebook 3. Skupa sedimentologa Jugoslavije&lt;/em&gt;, 11&amp;#8211;23. Hrvatsko Geolo&amp;#353;ko Dru&amp;#353;tvo, Zagreb.&lt;/p&gt;
&lt;p&gt;Babi&amp;#263;, Lj., Hochuli P. A.. &amp; Zupani&amp;#269;, J. (2002). The Jurassic ophiolitic m&amp;#233;lange in the NE Dinarides: dating, internal structure and geotectonic implications. &lt;em&gt;Eclogae Geologicae Helvetiae&lt;/em&gt; 95, 263&amp;#8211;75.&lt;/p&gt;
&lt;p&gt;&amp;#352;imuni&amp;#263;, A., Pikija, M., &amp;#352;imuni&amp;#269;, Al., &amp;#352;iki&amp;#263;, K. &amp; Milanovi&amp;#263;, M. (1976): Stratigrafsko - tektonski odnosi centralnog i isto&amp;#269;nog dijela Ivan&amp;#353;&amp;#269;ice. &lt;em&gt;8. Jugosl.geol.kongres&lt;/em&gt;, Bled, 1974., 2, 3003-313, Ljubljana.&lt;/p&gt;
&lt;p&gt;van Gelder, I., Matenco, L., Willingshofer, E., Tomljenovi&amp;#263;, B., &amp; Andriessen, P., &amp;#160;Ducea, M., Beniest, A. &amp; Grui&amp;#263;, A. (2015). The tectonic evolution of a critical segment of the Dinarides-Alps connection: Kinematic and geochronological inferences from the Medvednica Mountains, NE Croatia. &lt;em&gt;Tectonics.&lt;/em&gt; 34. n/a-n/a. 10.1002/2015TC003937.&lt;/p&gt;