Commune: Dwikozy (pow. sandomierski, woj. świętokrzyskie)
Framework element or context represented:
Sequence of the Middle Cambrian, Kielce subregion of the Świętokrzyskie (Holy Cross) Mts, northern part of the Małopolska Caledonian massif.
Primary geological/geomorphological interest:
Stratotype of the Góry Pieprzowe Formation, microtectonic forms, geomorphology.
Comparative assessment justification:
It is the largest outcrop of the Cambrian in the region and in Poland, the first in the country, where Cambrian rocks were documented by fossils (in 1892).
Protection status and accessibility:
Nature reserve “Góry Pieprzowe” (since 1979) – accessible by touristic trail.
Character of site: Slope with natural outcrops.
Area: 18.1 ha
Altitude: 140-200 m a.s.l.
Lithology: sandstones, conglomerates, breccias, shales
Discipline: Palaeobiology, Geomorphology, Stratigraphy of Phanerozoic, Tectonics
Process Age: Pleistocene, *all periods
Bedrock Age: Cambrian, *all periods
Description of primary interest:
Strongly folded and faulted shales form high (to 60 m) and steep slope of the Vistula river valley on the distance 2 km long. The shales are greyish black, argillous, with salt (alunite) efflorescences on the surfaces. They pass locally to grey silty-sandy shales with thin inserts of quartzitic sandstones and conglomerates. The last ones, belonging to the Komorna Member bear shale pebbles and pebbles (concretions) of phosphorites. Fossils are represented with brachiopods (new species), foraminifers and trilobites (documenting the Middle Cambrian age). Microtectonic forms represent: a) asymmetric or dysharmonic microfolds and scales – flexure drag folds and/or flow foldings related to early diagenesis; b) faults and clevage; c) boudinage. E-W strike and N dips of beds prevail in the western section of the slope. In the central and eastern sections orientations of microfolds axes are closer to N-S and beds dip to W. The axes of most of microfolds plunge towards NW or WNW, although the NE plunging is observed, too. The microforms enable to interprete mesotectonic structure of the rock – asymmetric fold with axis striking WNW-ESE and plunging to WNW. The shales could have been tectonically framed during the Caledonian, Variscan and Alpine movements (significant role of the post Caledonian tectonics is possible). The slope formed of the Cambrian shales is characterized by specific features typical for continuously and intensively eroded surfaces. The slope is partly bare, partly overgrown by thickets, inclined (30-50º) and dissected by numerous cuts 1-3 m deep. It is shaped by mechanical disintegration and chemical alteration, pluvial erosion and debris falls.
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