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GEOLOGICAL STRUCTURE
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In the geological structure of the Cracow-Częstochowa Upland two structural levels can be distinguished: the krakovid level containing folding and partly metamorphisized pre-Cambrian deposits up to upper Carboniferous and the level of the Mesozoic Cracow-Częstochowa monoclinal fold, which is most frequently visited by tourists on account of the beauty of the inselbergs and wonderful historic monuments like chapels, churches and unique "Eagle Nests". The oldest formations confirmed by drilling are metamorphic slates and phyllite dating back to the pre-Cambrian. The Cambrian period is represented by argillaceous slates, mudstone and sandstone whose thickness exceeds 1000 m. Those rocks eroded and became folded, and then were covered with carbonate deposits of the Ordovician (limestone, marl, dolomites). On top, there are partly metamorphisized Silurian slates whose layers blend with course-grained sandstone and gravel. While drilling in the region of Mrzygłód, the occurrence of graptolitic slates was also confirmed, with numerous diabase inserts. The oldest formations that can be seen on the surface are Devonian forms represented by 400-metre carbonate rock complex. Those are mainly dolomites and limestone showing in lower sections of sub-Cracovian valleys (the valleys of: Racławka, Czernka, Szklarka) and in the region of Siewierz. Higher in the geological cross-section there is dinant limestone (lower Carboniferous), which forms a complex of considerable thickness measuring up to 1200 m. Those rocks are exploited in a large, several-level quarry in Czatkowice near Krzeszowice. As a result of many tectonic movements taking place at the turn of lower and upper Carboniferous, the character of sedimentation changed from the sea to land type. Owing to the communicational activity of the rivers, the terrigenous material has been carried and deposited along with accumulated flora material. That was the way the upper-Carboniferous complex of sandstone, mudstone an slates came into being, including carbon deposits and inserts. The deposits are visible from the surface only in the region of Tenczynek, where until quite recently coal was mined. Above, there is Kwaczała arkosa forming light, thick-layer sandstone with traces of flinted tree trunks of the Dadoxylon genus. The Permian is marked here by numerous tectonic movements resulting in the Sławkowa Trench which occurs in the western vicinity of the Jurassic, abounding in lower Permian deposits made of: Karniowice sinter, Mylachowice conglomerates, and in the northern part of the trench - sands and slates with marl inserts. In the Permian there were also numerous volcanic eruptions which led to forming volcanic rocks in the southern part of the Cracow Upland: the Zalas porphyry, Miękinia melaphyry, Regulice and Niedwiedzia Góra diabase. The Trias and Jurassic formations are sloping at a slight angle towards the north-western direction, where they become hidden under the Miechów Basin chalk. The Trias is represented by flat sea deposits which flooded the area at that time. Those rocks (sandstone, marl, dolomites, limestone) are revealed only in the western part of described region. Jurassic formations prevail in the whole area of the Kraków - Częstochowa Jurassic (hence the name ).Where do they come from? The answer is very simple. The rocks here had been formed by decaying remains of organisms which once inhabited the sea here. The upper-Jurassic sea had the greatest importance, when the thickness of arising rocks reached thickness of several hundred metres (presently, as a result of erosion we observe rocks whose thickness comes even to 300 m in the Cracow Jurassic ). The most numerous fossils that can be observed today are: ammonites, belemnites, sponges, the Mollusca and the Brachiopoda. Owing to those marvellous fossils, this place is frequently visited by throngs of novice geologists who can often create a fantastic collection. The most dominant form of the Jurassic landscape is rocky limestone occurring as isolated rocks called inselbergs and rocks in river valleys. That kind of limestone came into being at the bottom of the sea within the structures similar to those of a reef, where they were made with the cooperation of organisms, mainly: sponges, blue-green alga and bacteria. Another form of limestone existing in this area is plate limestone which can be seen only in the quarry, as it does not form natural exposures. However, it is characterized by very rich ammonite fauna: Perisphinctes, Cardioceras, Kosmoceras, Peltoceras. The last type of limestone is bedding limestone whose characteristic feature is the presence of thick layers, sometimes exceeding 2 m thickness. Jurassic limestone`s outstanding feature is strong karst formation which developed mainly in the Tertiary. There are about 1500 caves and hostels, which puts the region of the Cracow - Częstochowa Upland in the first place in Poland in that respect. The longest of them is the Wierna Cave -1027m, situated in the Wiercica Valley. Wonderful rock formations grouped into large massifs in the area of OPN, Rabsztyn, Ryczowski Rocky Region, Podzamcze or Sokole Mountains attract great numbers of tourists. Lots of walking paths, the chance to travel by bike and continuously developing tourist infrastructure, make it possible to increase the amount of money left here by the tourists every year and favourably affect further development of this wonderful corner of Polish land. Chalk occurs only in the eastern part of the region, where the Cracow Jurassic comes close to already mentioned chalk Miechów Basin. For the most part of the Tertiary described area was a land and there were various denudative processes (erosion, weathering), which led to forming so-called palaeogene planation surface, i.e. characteristic tops, particularly in the southern part of the Jurassic, scattered with numerous limestone inselbergs. In the Miocene, as a result of sea transgression, limestone was formed at the bottom of the reservoir, and first of all scales filling mainly tectonic trenches which came into being in that period due to frequent orogenic movements. In the Quaternary, owing to Scandinavian continental glacier present in that area, clay, sand and gravel accumulated there, and at the end of the Ice Age, loess clay was wind-blown which currently covers the Cracow -Częstochowa Upland making up very fertile soil.
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