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Lithological and geochemical features of Turonian carbonates with stylolites in Pokuttya–Bukovyna (Ukrainian Carpathians)

Radkovets N., Manzhar N.

Biuletyn Państwowego Instytutu Geologicznego

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2012

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nr 449

131--136

EN

Chemical analysis of carbonates with stylolites from the autochthon of the Pokuttya–Bukovyna Carpathians showed that the СаСО3 content in the rocks ranges between 68 and 92%, insoluble residue makes 8–32%. Investigation of clayey limestones using the polarizing microscopy allowed to establish that the 0.02–1 mm sized organic debris (foraminifera, gastropods, brachiopods and inocerams) makes 40–55% of the rock. The rest is the matrix represented by pelitomorphic calcite. X-ray diffractometry showed that insoluble residue of the organic-rich clay from stylolites is represented by the hydromicaceous mineral – illite with admixture of organic matter. Results of quantitative spectral analysis revealed the increased iron and strontium (>10 times) content in both limestones and organic-rich clays. Infrared spectrometry of chloroform bitumen extracted from the organic-rich clay from stylolites showed that the dispersed organic matter by its origin consists mainly of planktonogenic (autochthonous) microcomponents and underwent significant postsedimentary transformations: polymerization and oxidation.

PL

Badania składu materialnego węglanów ze stylolitami w Karpatach pokucko-bukowińskich wykazały, że zawartość CaCO3 w skałach waha się od 68 do 92%, a pozostałości nierozpuszczalnej od 8 do 32. Szczątki organiczne wielkości od 0,02 do 1 mm (otwornice, ślimaki, ramienionogi i inoceramy) stanowią 40–55% skały, a reszta to kalcyt pelitomorficzny. Części nierozpuszczalne materiału stylolitów to na ogół minerał hydromikowy – illit oraz materia organiczna, cechująca się zwiększoną zawartością żelaza i strontu (>10 razy). Spektoskopia infraczerwona bituminu chloroformowego zawartego w stylolitach wykazała, że materia organiczna powstała głównie z mikroskładników planktonicznych (autochtonicznych) i uległa istotnym zmianom postsedymentacyjnym: polimeryzacji oraz utleniania.

2

Struktury hydratacyjne i deformacyjne w skałach czapy gipsowej wysadu solnego Dębiny w rowie Kleszczowa

Krzesińska A., Redlińska-Marczyńska A., Wilkosz P., Żelaźniewicz A.

Przegląd Geologiczny

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2010

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Vol. 58, nr 6

522-530

EN

The Dębina salt dome is situated in central part of the Tertiary Kleszczów Graben, central Poland. Cap rocks of the dome were characterized on the basis of analysis of core material from a well drilled in the northern part of that structure. The cap rock sequence may be subdivided into two parts. Its lower part with breciated structure represents residuum from dissolution of saline series whereas the upper comprises rocks developed by coalescence of shale cover with gypsum. Gypsum rocks of the cap form 6 lithotypes. In these lithotypes it is possible to distinguish: 1) recrystallizational structures developed during diagenesis and multiple hydration transformations, 2) structures developed in a local stress field related to displacements evoked by dissolution of the cap rocks and fluid circulation. Structures of the first type include microcrystalline gypsum with anhydrite relics and carbonate nodules, lenticular and acicular gypsum, porphyroblastic and even-grained gypsum as well as vein gypsum and first generation of stylolites. The other type of structures is represented by: gypsum showing shape fabrics and associated gypsum nodules, gypsum grains with geometry of -clasts, fibrous gypsum in pressure shadows, structures of the core-and-mantle type, subgrains developing in bigger crystals and second generation of stylolites and slickolites. Five sets of fractures were recorded. These fractures developed in the cape rocks under stress field with the vertical maximum stress axis and active shear planes. The normal faults of B, C and D sets could be formed during upward motion of the dome, its stagnation, or during gravitational collapse triggered by karst processes. Oblique striations on microfault B surfaces point to later reactivation under local normal-slip regime caused by ongoing subsidence of the cap rocks, or alternatively - a reactivation that occurred in response to external stress field which controlled evolution of the extensional Kleszczów Graben.

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Pochodzenie stylolitów w gipsach z czapy wysadu solnego Wapna

Jaworska J.

Przegląd Geologiczny

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2006

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Vol. 54, nr 2

166-169

EN

Stylolites have been found in a core sample from the gypsum cap rock of the Wapno salt dome (figs 1-3) at a depth of 40 m below the land surface. These structures are inclined at 40-45ş to the core axis and cut by neomorphic gypsum crystals. Stylolites are products of the solution pressure. They commonly occur in carbonates but are very rarely encountered in evaporates, thus the origin and preservation of these structures in the cap rock of Wapno dome are interesting problems. Lithostatic pressure near the surface where the cap rock has been formed is insufficient to develop stylolites. Thus stylolites (fFigs 4-5) in gypsum cap rock of the Wapno salt diapir are probably early diagenetic structures preserved in a fragment of Zechstein anhydrite of Z2 or Z3 cyclothems. This anhydrite block with stylolites have been carried inside intruding salt masses to the top ofWapno dome. Halite and other easy soluble minerals had been dissolved, but the anhydrites with preserved stylolites have been incorporated in the cap rock and secondary altered into gypsum, similarly to the phenomenon found in Gorleben Salt Dome by Bäuerle et al. (2000).