Browsing by Subject "tetrapod"

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Access status: Open Access ,
Walory geoedukacyjne kamieniołomu Zachełmie w Górach Świętokrzyskich (Polska Południowa)
(Wydawnictwa AGH, 2018) Złonkiewicz, Zbigniew; Mader, Anna
The abandoned Zachełmie quarry, a unique place on the geological map of the Holy Cross Mountains, is located in Zagnańsk, about 12 km northwards from Kielce. Deposits of two stages of geological development, separated by tectonic movements, are exposed in the section. The older complex is represented by the Middle Devonian grey dolomites and dolomitic claystones, steep inclined to the north. They were folded in the Carboniferous and Permian by the Variscan tectonic movements. The younger complex comprises various Permian-Lower Triassic deposits, inclined about 10° eastwards. They were deformed during the Paleogene by Alpine tectonic movements. Contact of both complexes, well exposed in the northern walls of the quarry, testifies Variscan orogenic movements, while the tectonic-erosion gap, separating them, comprises about 140 million years. Dolomites originated in the shelfal and lagoonal environments of the slowly deepening sea. Fossils typical for their Devonian environment may be found: stromatolites, amphipores, brachiopod shells and trace fossils. The unique surface with numerous structures interpreted as tetrapod trucks, the oldest in the world, is exposed in the southern wall of the quarry. Moreover, minerals occur in the north-eastern part of the quarry: calcite, hematite, dolomite, siderite, ankerite, quartz and barite. They originated in fissures cutting dolomites during the Variscan orogenic movements. The Permian and Triassic, red-brown deposits crop out in the northern walls of the quarry. They represent infilling of a narrow palaeo-valley/ravine, cut in the surface of Devonian dolomites. Their section is commenced with dolomite breccia and conglomerates that fill cavities in an uneven surface of ravine basement. These conglomerates represent a debris cover lain on its sides. The breccia and conglomerates laying further above, originated as abrupt debris flow deposits. In the upper parts of the section, they were intercalated and eventually entirely substituted with sandstones and mudstones being deposits of fine creeks. Periods of the flow extinction are documented with clays deposited in temporal ponds. Fine current structures, scarce flora remains and desiccation cracks may be distinguished in that part of the section. The oldest trace fossils of dinosaurs were found here. The thick-bedded grey sandstones distinguished in the uppermost part of section were deposited in alluvial channels of braided rivers. The unique values of the object are protected in a natural reserve formed in the eastern part of the quarry and in the narrow passage in the central part. The fragment of the wall in the passage with exposition of a tectonic-erosion unconformity is a natural monument. Authors intend to present the unique geological values of the quarry and to suggest how to improve the actual geotouristic infrastructure - location of several information boards with descriptions of geological phenomena and processes.