Projects / Programmes
Jurassic evolution of the transitional area between Slovenian Basin and Julian Carbonate Platform
| Code |
Science |
Field |
Subfield |
| 1.06.00 |
Natural sciences and mathematics |
Geology |
|
| Code |
Science |
Field |
| P460 |
Natural sciences and mathematics |
Sedimentology |
Transitional area, Slovenian Basin, Julian Carbonate Platform, Jurassic, sedimentology, paleogeography, geochemistry.
Researchers (1)
| no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
| 1. |
23426 |
PhD Boštjan Rožič |
Geology |
Head |
2007 - 2008 |
0 |
Organisations (1)
Abstract
Basis of the research will be focused on southern parts of the Julian Alps. In this area two main paleogeographic units are recognized: the Slovenian Basin and the Julian Carbonate Platform that drowned during Lower Jurassic and became a pelagic plateau known as the Julian High. Recently Jurassic successions of the central and northern part Julian Carbonate Platform were studied in detail, while the southern part remained poorly investigated due to scarce outcrops of Jurassic strata in this area. In the study for my Ph. D. Thesis Jurassic successions of the Slovenian Basin were investigated. The study revealed that evolution of the Slovenian Basin was substantially influenced by the Julian Carbonate Platform, especially by termination of shallow-water sedimentation on the platform in the Lower Jurassic. Nevertheless the accurate correlation between successions of the Slovenian basin and the Julian Carbonate Platform appeared to be problematic due to paleogeographically very distant investigated areas. For this reason field observations were recently carried out on the Bohinj Ridge (southern part of the Julian Alps) and Jurassic successions of the transitional area between the Slovenian Basin and the Julian Carbonate Platform were newly discovered. Preliminary research indicates that these successions exhibit drowning of the Julian Carbonate Platform. Successions therefore represent a missing link between two paleogeographic units and are essential for the understanding of complex interacting relationships between units. At the same time these successions also globally represent a great rarity, since transitional areas between basins and platforms are tectonically very deformable areas and therefore rarely preserved. Usually just stratigraphically discontinuous successions from inner parts of platforms are preserved, but no records of progressive drowning of platforms are found in such successions. The study of successions from transitional area on the Bohinj Ridge therefore highly contributes to the understanding of processes that leaded to final drowning of carbonate platforms. During the study for PH. D. Thesis in the same area continuous succession from Triassic to Jurassic was discovered. This succession is only proved such succession in the Slovenia. The discovery is important, since the Triassic/Jurassic boundary is characterized by great, but poorly understood mass extinction event and at the moment represents highly discussed subject by Jurassic scientists. Detailed sedimentological, paleontological and geochemical study of the boundary on the Bohinj Ridge will therefore contribute significantly to the understanding of global events that influenced mass extinction in this period of the Earth history. Both parts of the study will also enable a comprehensive correlation of events in the evolution of the Julian Carbonate platform as well as the Slovenian Basin.
Significance for science
Investigations concerning the project were maintained predominantly on the southern margins of the Julian Alps. The research focused on the successions of the transitional zone between the Julian Carbonate Platform (JCP) and the Slovenian Basin (SB). The detailed study included already known Upper Triassic to Jurassic sedimentary rocks of the proximal SB as well as classical successions of the JCP located in the Triglav Lakes Valley. Additionally, the research of newly discovered successions of the transitional zone between JCP and the SB was incomporated in the study. These succesions are located in the Kobla area (eastern Bohinj Range), where they partly belong to the Julian Nappe and partly to the Tolmin Nappe. All contributed data indicate the importance of the Plienbachian accelerated subsidence of the JCP margin. This tectonic event vastly influenced the evolution of the both paleogeographic units in this area. The event is particularly well manifested in the successions of the transitional zone. The base of studied sedimentary sections consists of shallow-water ooidal limestones that transitionaly turn into deeper-water bioclastic limestones characteristic of the open shelf sedimentary environment. The deepening is characterized also by the occurence of fossil assamblage (sponges, echinoderms) that indicate the eutrophication of the marine environment. Simultaneously, the uppermost parts of the successions contain thick-bedded limestone breccias and neptunian dykes, that indicate increased tectonic activity, more precisely subsidence and the disintegration of the JCP during this period. The importance of these successions is additionally manifested in good biostratigraphical datations that enable precise chronological timing of the geodinamic events. Apart from microfossil material, the new site of Pliensbachian, more precisely Upper Domerian amonites was found. It is first such site ever found in Slovenia. All this data enable very precise chronological and geodinamical understanidng of the processes that finally led to the drowning of the JCP. Additionaly, they enable the overall correlation of the evolutionary events between the JCP and the SB. It was revealed that both paleogeographic units were intimatelly related until the Pliensbachian tectonic event. Every sedimentary change on the JCP was imediatly manifested in the evolution of the proximal basin successions. This relation is still manifested during the inital stages of the platform drowning, where its is recorded in the composition of the resedimented limestones that compose the succession of basinal proximal parts. Namely, in this successions the resedimented ooidal limestone prevail in the lower part and are upwards replaced by the crinoidal resedimented limestones. After the Pliensbachian tectonic event the successions of the SB become uninfluenced by the JCP. During the thesis investigation the continous succession containing the Triassic/Jurassic boundary was discovered. It is first-known such succession in the Slovenia. The boundary was additionally sedimentologically, paleontologically and geochemically investigated in the postdoc project.
Main conclusions of the project are:
A) the Triassic/Jurassic boundary and the Pliensbachian period are both characterized by the intense tectonic activity and large impact of environmental events (biocalcification crisis and eutrophication),
B) this co-occurence of the events on the Triassic/Jurassic boundary did not result in the determination of shallow-water sedimentation on JCP,
C) contrary, the co-occurence of the events in the Pliensbachian drowned the JCP that after this period did not influence the evolution of the adjacent SB,
D) the drowning of the highly productive carbonate platforms can therefore result only from coeval environmental impact and tectonic activity that must cause the accelerated subsidence of the carbonate platforms.
Significance for the country
The results of the project contain also detailed geological maps of the investigated areas that can be used during the elaboration of the planned Basic Geological map of the Slovenia in scale 1 : 50 000. Such map is basic document of the state and contains data of geological structure, distribution of various rocks, and important tectonic elements. Geological maps represent the basis for hydrogeological investigations such as the flow of the underground waters, search of potential water resources, and protection of existing resources. Geological map are used in the geological - engeeniring researches such as land-slump and slide sanations, the geo-hazard estimations and consequently, the infrastructure planning in the examined areas. In the future the Republic of Slovenia plannes to invest large founds in the modernisation of the railway infrastructure. Contribuded geological data will be esential for the reconstruction of the railway-tunnel that connects Bohinjska Bistrica and Podbrdo exactly below the Mt. Kobla. Additionally, the data are interesting for the geo-tourism. It is quickly developing branch of tourism that tries to explain complex geological phenomenos to the geologically uneducated tourists. This branch of tourism is especially convinient on the investigated area, because it is situated in the mountains that are crossed by nomerous trekking routes. The establishment of informational boards on these routes and the book-guide the geological phenomenos would be described; i.e. fossil sites, litological changes, ore-deposits, large faults, hydrogeological characteristics, etc.. I would like to mention here that at the time of writing we are prepearing together with services of the Triglav National Park the elaboration of the geological book-guide of the Julian Alps. This guide will contains several stopping-points that were investigated during this project.
Most important scientific results
Final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Final report,
complete report on dLib.si
