Changing directions of the tectonic structures, consistent paleomagnetic directions at the NE imbricated margin of Stable Adria

Abstract

The imbricated margin of stable Adria, which belongs to the External Dinarides, comprises a chain of islands, which follow the dominant NW-SE Dinaric trend in the northern segment, while the dominant tectonic orientation changes to WNW-ESE in the central Adriatic area, near Split. The new paleomagnetic results documented in this paper are from the islands of the latter and can be interpreted in terms of tectonics together with already published robust data sets from the Northern Adriatic Islands and stable Adria, respectively. The problems addressed are the proposed extra CCW rotation in the central Adriatic area relative to the rest of the Dinarides, the differences in the tectonostratigraphic models of the offshore External Dinarides, the relationship to Stable Adria and the reason for the arcuated shape of the thrust front between stable and imbricated Adria.From the five largest Central and Southern Adriatic Islands over 1000 independently oriented cores, representing 98 Upper Tithonian – Paleocene carbonate localities, were subjected to standard laboratory processing of the natural remanent magnetization, component analysis, and statistical evaluation on locality and between locality levels. The results lead to the conclusion that these islands moved in close co-ordination with both, the Northern Adriatic Islands and stable Adria, at least from the Albian on. The different tectonic trends characterizing the islands and reflected also in the arcuated shape of the thrust front between Stable and Imbricated Adria is explained by the dominance of one of the Late Cretaceous and younger compressional strain fields. The structures due to the Late Cretaceous strain field are dominant in Cres island (N-S trend), the ones formed during the Late Eocene-Early Oligocene prevail in the Northern Adriatic islands (NW-SE trend), SE of Cres. The WSW-ENE general orientation of the structures in the Central Adriatic area is due to the strong neotectonic deformation.