engleski

Origin and composition of Upper Tithonian marly layers from Kirmenjak Quarry (Istria, Croatia)

The Upper Tithonian carbonate succession of the Kirmenjak quarry belongs to the lowermost part of the second Istrian megasequence and is characterized by numerous shallowing-upward cycles and dinosaur footprints as well. Shallowing-upward cycles range from 0.5 to 1.5 m in thickness and usually begin with black pebble breccia or mudstones, followed by fenestral mudstone, and usually end with peloidal packstone/grainstones and grainstones. On the top of one of the shallowing-upward succession, dinosaur footprints were found in intertidal fenestral mudstones. Almost a thousand of sauropod footprints, including 23 single trackways, have been recognized on the locality. Approximately one meter below the trackbearing horizon a 2-3 cm thick marly layer occurs. Investigated marly layer overlay black-pebble breccia and represent an emersion phase in the succession. The marl samples were preliminary examined by X-ray diffraction method. The results show the presence of vermiculite, muscovite and/or illite, quartz and calcite. Such composition could be the result of the different mineral origin. Muscovite and quartz could be of an eolian origin whereas vermiculite and illite probably indicates paleo-soils. Together with the dinosaur footprints this marly layer implies frequent emersion phases and establishment of continental conditions during the long-lasting period

Marls; Upper Tithonian; Kirmenjak; Croatia

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