GACKI

Description of primary interest:
Gacki quarry represents outcrop of complete sequence of the gypsum formation of the northern part of the Miocene basin. Primary, depositional structures have been preserved in the gypsum. The formation is characterised by horizontal and vertical diversity, which is related to evolution of the basin and its water. In the sequence 15 layers and 7 lithosomes were distinguished. The lithosome A (3 m) represents layer of giant, mainly palisade crystal intergrowths growing directly on the substratum due to precipitation from oversaturated brine. It is overlain by bedded grass-like gypsum intercalated with fine-crystalline one – originated in very shallow brine (B – 3 m). Lithosomes C and D (12 m) consist of bedded, sabre-like gypsum deposited in deeper basin. Their sedimentation was interrupted by short period of dilution of brine by fresh, meteoric waters. Microcrystalline, usually laminated gypsum and clastic gypsum (breccias) represent lithosomes E and G (16 m). According to the most reliable hypothesis their deposition is related to halite oversaturation and Ca ion depletion, which caused mixed gypsum-halite deposition and precipitation of gypsum crystals in the brine above the bottom and their mechanical deposition. Formation of breccias is referred to halite dissolution (during several events of salinity falls due to water refreshment) and gypsum redeposition related to gravitation or tectonic processes. The largest event was connected with influx of open-marine waters and local deposition of grass-like gypsum (lithosome F absent in Gacki). Other interesting geological phenomena represent: a) fault in gypsum and underlying marls; b) cave in gypsum Jaskinia w Krzyżanowicach Górna with archaeological site.

Literature:

BĄBEL M. 1999–Facies and depositional environment of the Nida gypsum deposits (Middle Miocene, Carpathian Foreddep, southern Poland). Geol. Quater. 43, 4: 405-428.     BĄBEL M. 1999–History of sedimentation of the Nida gypsum deposits (Middle Miocene, Carpathian Foredeep, southern Poland). Geol. Quater. 43, 4: 429-448.     GŁAZEK J. 1993–Nowe dane o krasie gipsowym Niecki Nidziańskiej (in Polish only). Streszcz. Ref. Wygł. na Posiedz. Oddz. Pozn. Pol. Tow. Geol., 2: 32-37.     GŁAZEK J., HARTON P., WICIK B. 1994–Kras gipsowy Niecki Nidziańskiej (in Polish only). Streszcz. Ref. Wygł. na Posiedz. Oddz. Pozn. Pol. Tow. Geol., 3: 19-21.     GUBAŁA J., KASZA A., URBAN J. 1998–Jaskinie Niecki Nidziańskiej (in Polish only). Pol. Tow. Przyj. Nauk o Ziemi, Warszawa, 173 pp.     KASPRZYK A. 1993–Lithofacies and sedimentation of the Badenian (Middle Miocene) gypsum in the northern part of the Carpathian Foredeep, southern Poland. Ann. Soc. Geol. Pol., 63: 33-84.     KASPRZYK A. 1999–Sedimentary evolution of Badenian (Middle Miocene) gypsum deposits in the northern Carpathian Foredeep. Geol. Quater. 43, 4: 449-465.     KUBICA B. 1992–Litofacial development of the Badenian chemical sediments in the northern part of the Carpathians Foredeep (English sum.). Pr. Państw. Inst. Geol. 133: 1-60.     URBAN J., GUBAŁA J., KASZA A. 2003–Caves in gypsum of the Nida basin, Southern Poland (English sum.). Przegl. Geol. 51, 1: 79-86.     URBAN J., WRÓBLEWSKI T. 1999–Representative geosites of the Góry Świętokrzyskie (Holy Cross Mts.) and the Nida Basin, Central Poland. Pol. Geol. Inst., Special Papers, 2: 61-70.