Investigations on the emplacement mechanisms of the Eocene olistoliths of the Miramare Castle (Trieste, Italy)

Eocene Flysch deposits are widespread in north-eastern Italy, Slovenia and Croatia and represent the sedimentation in the foreland basin of the Dinaric chain. Flysch extensively outcrops in the surroundings of Trieste at the front of the Carso Anticline. The Carso Anticline is a large NW/SE trending structure in the thick carbonate succession of the Friuli Carbonate Platform, a shallow water carbonate domain representing the northeastern termination of the large Adriatic Carbonate Platform that stretched from northeastern Italy to Montenegro and hosted shallow water sedimentation for large part of the Mesozoic and the Cenozoic.A rather unknown peculiarity of the Trieste Fysch succession is that at Castle of Miramare, in the vicinity of Trieste, it is found in association with a series of large calcareous blocks that make up the promontory on which the castle is built. Approximately, a hundred calcareous blocks having volumes ranging from about 500,000 m3 to 1,300,000 m3, were identied in previous mapping campaigns. Tonelli (2001) highlighted that the blocks are made of Eocene platform limestone belonging to the Miliolid, Alveolinids and Nummulites Limestone. The Miliolids, Alveolinids and Nummulites Limestone represents a phase of carbonate deposition that took place when the Friuli Platform in this sector was inuenced by fore-bulging of the Dinaric chain that was advancing from the northeast. The blocks overlie and are overlain by ysch, thus testifying that their deposition was, at least in part, contemporaneous to that of the ysch itself. The presence of marly conglomerate lithofacies, in places associated to the blocks, has been interpreted as the matrix of a cohesive debris Flow of which the calcareous blocks are olistoliths. Whereas the blocks have been mapped and some of their features identied, the mechanisms of their deposition are not yet completely understood. In this contribution, we present new data concerning the characteristics of the calcareous blocks, their spatial relationships with the Flysch and the associated deformations that help shedding light on the processes that operated during the emplacement of the Miramare olistoliths. Tonelli N. (2001) - L’origine dei blocchi calcarei del parco di Miramare (Trieste). Tesi di laurea inedita. Università degli Studi di Trieste.