POSTSEDIMENTARY DOLOMITIZATION BRECCIAS IN THE JURRASIC SHALLOW-MARINE CARBONATE SEDIMENTS OF THE MALI ALAN – SOUTH VELEBIT Mt

• Main Author: Josip Tišljar
• Format: Article
• Language: English
• Published: Faculty of Mining, Geology and Petroleum Engineering 1990-12-01
• Series: Rudarsko-geološko-naftni Zbornik
• Subjects: Postsedimenrary dolomitization breccia: Jurassic shallowmarine carbonates of the Velebit Mt.; rhythmic peritidal sedimentation; tempestites: late-digenetic dolomitization
• Online Access: http://hrcak.srce.hr/index.php?show=clanak&id_clanak_jezik=38918&lang=en

Thin layers of ooid grainstones and/or thin layers and intercalation of tempestite breccias are very frequent as a rhythmic sedimentation members in the shallow—marine, prevailing lagoo-nal, mudstone/wackestone Dogger limestones. Such a sedimentation is a consequence of carbonate mud deposition in lagoons and restricted shallows and temporary flooding and deposition of ooid sand and/or coarser detritus by enhanced water energy, i.e. stormy waves. The shallow- marine limestones in the Lower and Middle Dogger comprise zones of carbonate breccias thick several to tens meter, consisting of darkgray »fragments« of mudstone and wackestone and dolomite "cement". This postse-dimentary dolomitization breccias are definitely not synsedimen-tary formation, and became by incomplete late-diagenetic dolomitization of previously tectonized, fractured and crashed Dogger limestones. Their misinterpretation by a synsedimentary process, especially as a intraformational breccia type, since they appeared confomably stratified in the Dogger limestone, may lead to serious mistakes in interpretation of paleomorphology of carbonate platform and erroneous reconstruction of sedimentary environment and depositional conditions for the Dogger limestones (the paper is published in Croatian).