The Role of Palaeogene Clastics in the Tectonic Interpretation of Northern Dalmatia (Southern Croatia)

Abstract

The Palaeogene coarse-grained clastics of Northern Dalmatia (Jelar breccia, Promina deposits and Flysch) are syntectonic deposits related to the structural evolution of the Dinaride Thrust Belt. The Jelar breccia is a proximal sedimentary unit deposited in response to early compression of the carbonate platform (Lutetian to Bartonian). Flysch deposits are considered as their distal equivalents. The Early Jelar breccia displays a blended clast composition related to the simultaneous erosion of various carbonate stratigraphic units along the Early Velebit Fault. The Late Jelar breccia, the next tectonically generated deposit, has an inverted clast composition related to the erosion of the faulted Velebit anticline. The next tectonic phase (Bartonian to possibly Oligocene) caused folding and thrusting of underlying platform carbonates and tectonic transport, cannibalisation and reworking of the existing Flysch, Early and Late Jelar breccias. Continuing compression created a new elongated foreland basin with NW-SE extension, filled with about 2000 m of prograding Promina deposits. The final structural setting of Northern Dalmatia was the result of thrusting of the northeast edge of the Promina deposits. This produced duplexing of internal thrusts, uplift of the Promina deposits on the highest topographic position and significant erosion. This polyphase and complex tectonism can be described by a thin skin tectonic model in which Upper Jurassic - Lower Cretaceous platform anhydrites acted as a perfect gliding surface.