Commune: Pińczów (pow. pińczowski, woj. świętokrzyskie)
Framework element or context represented:
Evaporite (gypsum) formation of the Nida Basin, representing sediments of northern, peripheral part of the fore-Carpathian marine basin.
Primary geological/geomorphological interest:
Sequence of Badenian gypsum rocks, sedimentary structures, karst and tectonic forms.
Comparative assessment justification:
Gacki site represents the best cross-section of the evaporite formation in the northern, peripheral part of the Miocene fore-Carpathian marine basin. In the gypsum primary depositional structures are preserved.
Protection status and accessibility:
The small fragment of area is protected only as nature monument (since 1987) and the important Gacki quarry is proposed for protection, well accessible.
Character of site: Abandoned quarry, cave.
Area: 30 ha
Altitude: 200-250 m a.s.l.
Lithology: conglomerates, breccias, marls, gypsum (anhydrites)
Discipline: Geomorphology, Palaeoenvironment, Petrography, Stratigraphy of Phanerozoic, Tectonics
Process Age: Quaternary, *all periods
Bedrock Age: Neogene, *all periods
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.
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