Abstract
The Macelj formation is an informal Eggenburgian-early Ottnangian lithostratigraphic unit that is established in the area of the Hrvatsko Zagorje Basin, which represented a marginal zone of the Early Miocene Central Paratethys Sea. Modern studies, as a part of the Geologic Map of the Republic of Croatia 1:50 000 project, yielded new data that improves the knowledge of the depositional and stratigraphic characteristics of the formation. The sedimentological research within this study was focused on the two older lithostratigraphic units of the Macelj formation: the Vučji Jarek member and the Čemernica member. The Vučji Jarek mb. is represented by three facies. The Facies of horizontally bedded sandstones is characterized by mostly medium-grained, moderately sorted sandstones that reflect deposition on the foreshore to the upper shoreface. The facies of horizontally and cross-bedded glauconitic sandstones is composed of fine- to coarsegrained, well-sorted sandstones that indicate foreshore to shoreface deposition under tidal influence. The Facies of horizontally and cross-bedded pyroclastics consists of tuff, pumice, lapilli and large blocks, showing a chaotic structure in places. Deposition occurred at the shoreface under tidal influence. The Čemernica mb. is represented by the Facies of structureless clayey-silty sands that are poorly sorted and bioturbated, and indicates deposition below the fairweather wavebase, in the offshore-transition zone. Deposits of the members include marine macro- and microfossil associations. K-Ar dating of separated glauconite mineral fractions yielded an early Eggenburgian age for the Vučji Jarek mb. glauconitic sandstones (19.2±0.64 Ma) which is in accordance with biostratigraphical analyses. Sedimentological characteristics of the Eggenburgian Macelj fm., especially those that reflect the tidal influence, fit the general characteristics of the Central Paratethys Sea in the Early Miocene.
Highlights
The lower Miocene Macelj formation was described and mapped in eastern Slovenia and the northwestern part of the Hrvatsko Zagorje Basin (HZB) in Croatia (ŠIMUNIĆ, AN. et al, 1995; ANIČIĆ & JURIŠA, 1984, 1985; ANIČIĆ et al, 2002; Fig. 1A)
The Macelj formation is an informal Eggenburgian-early Ottnangian lithostratigraphic unit that is established in the area of the Hrvatsko Zagorje Basin, which represented a marginal zone of the Early Miocene Central Paratethys Sea
The sedimentological research within this study was focused on the two older lithostratigraphic units of the Macelj formation: the Vučji Jarek member and the Čemernica member
Summary
The lower Miocene Macelj formation was described and mapped in eastern Slovenia and the northwestern part of the Hrvatsko Zagorje Basin (HZB) in Croatia (ŠIMUNIĆ, AN. et al, 1995; ANIČIĆ & JURIŠA, 1984, 1985; ANIČIĆ et al, 2002; Fig. 1A). The lower Miocene Macelj formation was described and mapped in eastern Slovenia and the northwestern part of the Hrvatsko Zagorje Basin (HZB) in Croatia In Croatia, it is distributed in the area between Mts. Strahinščica and Ivanščica in the south and Ravna gora in the northeast, bounded by the Sutla River in the west and Bednja in the east (Fig. 1A). Strahinščica and Ivanščica in the south and Ravna gora in the northeast, bounded by the Sutla River in the west and Bednja in the east (Fig. 1A) These deposits are about 300-350 m thick and consist of the so-called Macelj sandstones, i.e. glauconitic sandstones, conglomerates, siltstones, pelites and pyroclastics (AVANIĆ et al, 2005; AVANIĆ, 2012) and as such, they were represented on recent geological maps (Fig. 2) More recent researches proposed a further member, i.e. the Vrbno mb. (AVANIĆ et al, 2005; AVANIĆ, 2012) and as such, they were represented on recent geological maps (Fig. 2)
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