Projects / Programmes
Jurassic and Cretaceous radiolarian stratigraphy of the Southern Alps in northwestern Slovenia: age constraints on basin dynamics at the edge of the Neotethys
| Code |
Science |
Field |
Subfield |
| 1.06.02 |
Natural sciences and mathematics |
Geology |
Palaeontology and biostratigraphy |
| Code |
Science |
Field |
| P450 |
Natural sciences and mathematics |
Stratigraphy |
| Code |
Science |
Field |
| 1.05 |
Natural Sciences |
Earth and related Environmental sciences |
Jurassic, Cretaceous, Radiolaria, basin dynamics, Adriatic plate, Southern Alps, Dinarides, Slovenia
Researchers (7)
Organisations (2)
Abstract
The study area belongs to the eastern Southern Alps where the Southalpine and the Dinaric structures now overlap. In the Mesozoic times, this area belonged to the eastern Adriatic continental margin facing the Meliata-Maliac Ocean, which opened in the Middle Triassic as an embayment of the Neotethys. On its western side, the Adriatic plate was bordered by the Alpine Tethys, which opened in the Middle Jurassic and was part of the Atlantic system. Precise stratigraphic research in this area can thus provide clues for better understanding of interrelation between rifting histories of the two oceanic domains and geodynamic evolution of the ensuing Alpine-Dinaride-Carpathian orogenic system.
Four paleogeographic units are differentiated in the study area: the Bovec and Bled troughs that formed near the end of the Early Jurassic, the Julian High (a pelagic plateau since the Middle Jurassic), and the Tolmin Trough, which existed since the earliest Jurassic and was bordered by a large stable carbonate platform. Among these basins, the Bled Trough occupied the most distal position on the continental margin. This position is inferred from the age of flysch-type deposits that started to accumulate in the Early Cretaceous in the Bled Trough but much later, in the Campanian-Maastrichtian, in the Tolmin Trough.
Complete Lower Jurassic to mid-Cretaceous successions of these paleogeographic units are well exposed. For each unit we have selected reference sections, in which the sedimentary record and its fossil content will be examined in detail. The emphasis will be given to those parts of the stratigraphic record that are relevant for the reconstruction of basin dynamics. Precise age constraints will be primarily obtained through paleontological studies, mostly on radiolarians and, in the Cretaceous, also on nannoplankton. The successions will be correlated with corresponding successions in the Dinarides (from Croatia to Greece), Northern Calcareous Alps and Carpathians (Austria, Slovakia to Romania), and the Southern Alps (northern Italy).
The aim of the proposed project is 1) to study in detail the key sections, for which the existing data are poor or out-of-date, and 2) to compile relevant stratigraphic data from different localities into an integral correlation, which will synthesise discernible tectono-stratigraphic events and their timing. The correlation will focus on the following events:
- Subsidence phases in the Early and Middle Jurassic (probably one in the Pliensbachian and another one in the Bajocian).
- Early emplacement of ophiolite nappes in the most internal units and development of carbonate platforms on top of emplaced ophiolites (possibly Late Jurassic to earliest Cretaceous).
- Formation of initial foreland basins (Early Cretaceous).
- Renewed subsidence (associated with an erosional event) in the Tolmin Trough, possibly coinciding with formation of large neptunian dykes on the margins of the Julian High (mid-Cretaceous).
The relevance of the expected results can be summarized as follows:
1) Precise age constraints will elucidate the Jurassic and Cretaceous basin dynamics in the study area and will contribute to further development of palinspastic models on a regional scale.
2) Accurate dating of different formations will, in addition, enable global correlations and interpretation of basin fill in terms of climate change and eustatic sea-level fluctuations.
3) On a more local scale, the refined stratigraphy will serve as a basis to improve tectonic reconstructions of the Julian Alps.
4) The hitherto poorly dated and unnamed lithostratigraphic units will be formally described. These results will improve the local stratigraphic nomenclature.
5) An important objective of the project is to promote Slovenian natural heritage. The sites to investigate are located in the Triglav National Park and will be evaluated in terms of conservation, protection and educational value.
Significance for science
In this project, precise age constraints were obtained in Jurassic and Cretaceous successions of the Pokljuka, Krn and Tolmin nappes in the Julian Alps. These results are a novel contribution to the understanding of basin dynamics on the northeastern margin of the Adriatic plate. The studied successions were correlated to similar successions in the Southern Alps, Northern Calcareous Alps and Dinarides. The results enable broader regional correlations and will thus substantially contribute to further development of palinspastic models for the Alpine realm. On a more local scale, the results can serve as a basis to improve tectonic reconstructions of the Julian Alps. The proposed lithostratigraphic subdivision (lithostratigraphic units are revised and some of them are newly described) are an essential tool for future mapping. The updated stratigraphy of the Pokljuka Nappe, that is, of the Bled Basin is the most important result. The stratigraphic evolution of this basin bears striking similarities with those of the Central Dinarides and the Tirolic units of the Northern Calcareous Alps. It is now clear that the Pokljuka Nappe is the most far-travelled nappe in the Julian Alps. A still open question remains, whether the nappe emplacement occurred in one or perhaps in two phases, of which the first phase may have started already in the mid-Cretaceous.
Significance for the country
The results are primarily applicable for educational purposes. The successions are easily accessible and provide a very good training locality for students, particularly for stratigraphy, sedimentology and micropaleontology. The area is particularly suitable for student exercises at making graphic logs and undertaking basic and advanced geological mapping. The direct educational impact was the training of one doctoral student within this project. The results further provide a basis for the evaluation of geological sites in terms of their conservation, protection and educational value. The study area is of special interest, since it is located in the Triglav National Park. Popular science articles contribute to the promotion of Slovenian geological heritage, to the awareness of geology as a science in society, and will potentially have an impact to the development of tourism in the area. The members of the project team cooperated in organization and writing of guidebooks for four congress field trips. In this way, we contributed to popularization of geological and other sites of interest in domestic and international geological community.
Most important scientific results
Annual report
2011,
2012,
2013,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2011,
2012,
2013,
final report,
complete report on dLib.si
