Geologia Croatica, Vol. 79 No. 3, 2026.
Original scientific paper
Radiolarian dating of Mala Palagruža pelagic succession: direct evidence of Middle Jurassic evolution of the central Adriatic Basin
Duje Kukoč
; Croatian Geological Survey, Zagreb, Croatia
*
Tvrtko Korbar
; Croatian Geological Survey, Zagreb, Croatia
Ivan Mišur
; Croatian Geological Survey, Zagreb, Croatia
* Corresponding author.
Abstract
The Adriatic Basin was one of the pelagic basins of the Adriatic microplate formed as a consequence of Late Palaeozoic–Early Mesozoic extension. However, unlike other pelagic domains of the Adriatic microplate, that have successions exposed in the peri-Adriatic mountain chains, the Lower Jurassic to Miocene deposits of the Adriatic Basin are mostly buried beneath the modern Adriatic Sea. One of the rare places where pieces of this pelagic succession are exposed above sea level is the Palagruža Archipelago in the central Adriatic. There, blocks of pelagic lithologies are brought to the surface by active diapirism of Triassic evaporites. A succession several tens of metres thick, composed of thin-bedded microcrystalline and partially silicified grey dolostone, interlayered with very thin-bedded siliceous siltstone is exposed on the island of Mala Palagruža. This succession is informally named the Mala Palagruža formation, however, it lacks underlying and overlying deposits. Radiolarians extracted from three samples of siliceous siltstone from the Mala Palagruža succession indicate a late Bajocian–Bathonian to possibly early Callovian age. Correlations with the offshore industrial wells drilled in the Adriatic Sea and onshore successions of the central Apennines, indicate that the investigated block is likely to be equivalent to the Calcari Diasprigni Formation, a deep-marine facies deposited in the central part of the Adriatic microplate during a period of eutrophic conditions, which favoured radiolarian productivity. This is the first discovery of Jurassic pelagic deposits above sea level in the central Adriatic.
Keywords
Middle Jurassic; dolostone; siliceous siltstone; biostratigraphy; Mid-Adriatic Ridge; Adriatic foreland; salt diapir
Hrčak ID:
352770
URI
Publication date:
30.10.2026.
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