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Middle Lower Jurassic coarsening-upward sedimentary signature within the carbonate platform succession of Velika Kapela Mt. (Karst Dinarides, Croatia)

The middle Lower Jurrasic sedimentary succession has been formed within the interior of the isolated Adriatic carbonate platform area. It reveals successive coarsening-upward trend from the subtidal below the fair-weather wave-base as the predominant response to the autocyclicity in the sedimentary environment. Gradual aggradation of the muddy carbonate material, deposited below the fair-weather wave-base reduced accommodation space, causing the sea-bottom to rise above the fair-weather wave-base. Here, more grainy carbonates were deposited, creating one coarsening upward cycle with mudstones or peloidal-bioclastic wackestones as the lower cycle member and peloidal-bioclastic wackestones/packstones to grainstones as the upper cycle member. During the "lag phase", the sea-bottom has sunk below the fair-weather wave-base, which enabled the formation of the next coarsening upward cycle. The progradations of the neighbouring oolitic shoals periodically and randomly interrupted this process. Oolitic shoals sporadically formed on topographic highs within the subtidal area, progradated over the surrounding environment below or above the fair-weather wave-base, producing sporadic coarsening-upward cycles with ooid grainstons and/or ooid-bioclastic packestones to grainstones as the upper cycle member. Therefore, the middle Lower Jurassic coarsening-upward arhitecture of Velika Kapela Mt. resulted from interplay of repeated sediment aggradations, interrupted by periodical and random oolitic shoal progradations.

Middle Lower Jurassic; coarsening-upward cycles; Velika Kapela Mt.; Karst Dinarides; Croatia

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