Commune: Kraków (pow. Kraków, woj. małopolskie)
Framework element or context represented:
Upper Cretaceous transgression and stratigraphy.
Primary geological/geomorphological interest:
Abrasion surface developed on Upper Jurassic limestones covered with Upper Cretaceous marls.
Comparative assessment justification:
The best outcrop of abrasion surface documentary the Upper Cretaceous transgression. One and only site of this type in Poland and in Europe also.
Protection status and accessibility:
Nature reserve Bonarka was established in 1961. The quarry is arranged as a didactic locality and has an educational trail.
Character of site: Abandoned quarry.
Area: 2.29 ha
Altitude: 240 m a.s.l.
Lithology: other siliceous rocks, limestones, marls, silts, clays
Discipline: Palaeobiology, Palaeoenvironment, Stratigraphy of Phanerozoic, Tectonics
Process Age: *all periods
Bedrock Age: Neogene, Cretaceous, Jurassic, *all periods
Description of primary interest:
Upper Cretaceous marls were excavated during the long time about hundred years ago in the big quarry for the cement factory "Bonarka" in Cracow. The most part of this outcrop was recultivated and only one segment of them exists till now. Upper Jurassic bedded limestones with cherts and a scarce fauna of ammonites, brachiopods and sponges crop out on the bottom of the old quarry. An abrasion surface connected with the Upper Cretaceous (Santonian) transgression cuts the top of these limestones. It is very well developed and slopes down toward the southeast. A sequence of green-grey and white marls with cherts containing numerous sponges, belemnites, echinoids and other fossils represents Upper Cretaceous deposits of the Santonian -Lower Campanian age. It covers the abrasion surface and is visible in the eastern part of the outcrop. A rare mineral chatchettine (C38H78) filling locally small spaces within marls was accessible during exploitation. A few faults cut Jurassic limestones forming steps at the bottom of the quarry. Traces of Miocene caliche, overlain with marly clays rich in microfauna indicating the Lower Badenian, occur in the south-eastern part of this locality. The abrasion surface dislocated by Miocene faults is the exceptional value of the referred site.
ALEXANDROWICZ S.W. 1954–Turonian of the southern part of the Cracow Upland (English sum.). Acta Geol. Polonica IV: 361-390. ALEXANDROWICZ S.W. 1968–Les dépods transgressif du Santonien aux environs de Cracovie (French sum.). Zesz. Nauk. AGH, Geologia, 11: 45-59. GRADZINSKI R. 1961–The project of the reserve at Bonarka (English sum.). Ochr. Przyr., 27: 239-251. GRADZINSKI R. 1972–Przewodnik geologiczny po okolicach Krakowa (Polish only). Wyd. Geol. MOROZEWICZ J. 1909–O haczetynie i jego Bonarskim złożu (Polish only). Kosmos, 34: 610-624. SZCZEPAŃSKA M., PILECKA (EDS)–Geologiczno-przyrodnicze rozpoznanie terenów pogórniczych Krzemionek Podgórskich dla potrzeb ochrony ich wartości naukowo-dydaktycznych i ekologicznych (Polish only). WIECZOREK J., DUMONT T., BOUILLIN J.P., OLSZEWSKA B. 1994–Neptunian dykes of Bonarka (Cracow, southern Poland) - a testimony of the late Cretaceous tectonic movements in the Cracow Upland (English sum.). Prz. Geol. 42: 988-995.