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Wykształcenie mikrofacjalne i procesy diagenetyczne utworów dolomitu głównego (cechsztyn) na izolowanej platformie węglanowej Cychr

100%

Sylwestrzak J.

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tom Vol. 49 nr 10

873-880

EN

The purpose ofpetrographic studies was to describe dolomite deposits of the Main Dolomite (Ca2) that make up a small carbonate platform on the Gorzów Wielkopolski Block (western Poland). This structure contains a gas pool formed as a result ut microfacies development and diagenetic history of the Ca2 deposits. Vadoid packstones and grainstones predominate in borehole Cychry 4, whereas the deposits from borehole Cychry 2 are developed primarily as peloid and oncoid packstones and grainstones /and bioclastic packstones in the upper part of the profile). Diagenetic processes, responsible for formation and preservation of good reservoir properties, intensively overprinted the original features of sediments. The lack or presence of anhydrite cements is the most important effect of diagenesis.

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From palaeosols to carbonate mounds: facies and environments of the middle Frasnian platform in Belgium

86%

Silva da A. C. , Boulvain F.

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tom Vol. 48, No 3

253--266

EN

This paper provides a synthetic sedimentological overview of themiddle Frasnian carbonate platform of Belgium and associated carbonate mounds. Carbonate mounds started usually in a relatively deep, quiet subphotic environment with a crinoid-coral-sponge assemblage, then reached the fair-weather wave base and the euphotic zone with an algal-microbial facies. The upper parts of themounds are characterised by lateral facies differentiation with the algal-microbial facies protecting a central sedimentation area with a dendroid stromatoporoids facies and fenestral limestone. The lateral facies reflect different kinds of input of reworked mound material in the proximal area, from transported fine-grained sediment to coarse-grained fossil debris. On the platform, environments range from the outer zone (crinoidal facies) to stromatoporoid-dominated biostromes and to the lagoonal area of the inner zones (subtidal facies with Amphipora floatstone, algal packstone, intertidal mudstone and laminated peloidal packstone and palaeosols). These facies are stacked in metre-scale shallowing-upward cycles. The larger scale sequential organisation corresponds to transgressions and regressions, whose cycles are responsible for differentiating a lower open-marine biostrome dominated unit from an upper lagoonal unit. The last regression- transgression cycle, responsible for the platform-scale development of lagoonal facies, can be correlated with an atoll-stage evolution of the carbonate mounds belonging to the Lion Member.

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Biostratigraphy and palaeoenvironmental development of the Callovian-Valanginian carbonate platform from the Lyubash unit (SW Bulgaria)

86%

Ivanova D. , Koleva-Rekalova E. , Kołodziej B. , Metodiev L. , Roniewicz E.

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tom Vol. 4, no. 1

174-175

EN

This study deals with the successions located in the Lyubash unit (SW Bulgaria), which represents a part of the Moesian Carbonate Platform in Middle Jurassic – Early Cretaceous time interval. According to the recent tectonic scheme of Bulgaria (Dabovski et al. 2002) the Lyubash unit belongs to Srednogorie tectonic zone of the Balkan orogenic system. Three sections have been sampled and studied – Rebro, Lyalintsi and Velinovo, which are built up by thick-bedded to massive light grey to whitish organogenic and micritic limestones of the Javorets, Gintsi and Slivnitsa formations. Detailed studies on foraminifera and calcareous dinocyst, provided new biostratigraphic data, and confirmed the Middle Callovian-Valanginian age of the examined sediments as assumed previously by Sapunov et al. (1985). Foraminifera are particularly abundant in the lagoon facies, and represented by genera: Globuligerina, Ophthalmidium, Cornuspira, Ammobaculites, Mesoendothyra, Labyrinthina, Kurnubia, Pseudocyclammina, Dobrogelina, Rumanoloculina, Hechtina, Meandrospira, Valvulina, Trocholina, and Neotrocholina. The sedimentological analysis allowed recognizing microfacies groups assigned to three facies zones: platform slope facies, reef and peri-reef facies and lagoon-tidal flat facies. The development of the platform is characterized by complex vertical and lateral alternation of the studied microfacies. Platform slope facies are prevalent at the section Rebro; the Lyalintsi section is dominated by reef and peri-reef facies, and the section Velinovo is mainly dominated by lagoon facies. Sea-level fluctuations are observed, however generally, a shallowing-upward trend in the platform evolution is observed in all three sections. Coral-microbial reefs are developed as biostromes, and contain numerous and highly differentiated scleractinian corals: 70 species (6 new) from 50 genera (4 new). Among them following corals are the most common: phacelloid Latomeandra, Stylosmilia, Thecosmilia, Cladophyllia, ramose Solenocoenia, Meandrophyllia, lameller Synastraea and Microsolena. Reef development has been disturbed by sea level rise, evidenced by limestones with Saccocoma, intercalated with coral biostromes.

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The Racławka Valley – an example of an educational geosite related to the development of a Paleozoic carbonate platform

72%

Szczurek S. , Bąk M. , Dulemba P.

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tom nr 1-2

45--56

EN

The location and most interesting geological features of the Upper Devonian through Lower Carboniferous limestones in the Racławka Valley were presented. The limestones outcropped almost continuously along the natural valley cutting. They comprise over 60 million years of continuous growth of the carbonate platform, which developed on the ancient terrane – the Upper Silesian Block. Geosites described herein may constitute a destination for geological trips for undergraduate students of Environmental Sciences, where they can actively discover the development of an ancient carbonate platform and accompanied post depositional structures.

PL

W dolinie Racławki znajdują się ważne geologicznie naturalne odsłonięcia wapieni (od późnego dewonu do wczesnego karbonu). Wapienie te obejmują okres ponad 60 milionów lat ciągłej sedymentacji węglanowej, która występowała na obszarze paleozoicznego kratonu – bloku górnośląskiego. Opisane stanowiska mogą być celem wycieczek geologicznych studentów pierwszego stopnia studiów przyrodniczych, w czasie których mogą oni w aktywny sposób śledzić rozwój kopalnej platformy węglanowej i struktur postdepozycyjnych.

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Potencjał naftowy utworów dolomitu głównego w strefie Kamienia Pomorskiego. Część 1 - Macierzystość

58%

Kotarba M. J. , Kosakowski P. , Więcław D. , Kowalski A.

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tom Vol. 51, nr 7

587-594

PL

Na podstawie wyników badań geochemicznych wykonanych dla 55 profili dolomitu głównego, w obrębie platformy węglanowej Kamienia Pomorskiego i jej bezpośredniego otoczenia, dokonano kompleksowej charakterystyki macierzystości skał z uwzględnieniem wydzieleń paleogeograficznych i mikrofacjalnych. Najwyższe zawartości węgla organicznego TOC, do 5,8% wag., występują w obrębie facji madstonowej zatoki równi basenowej. Facje madstonowe płytszej części równi basenowej oraz stoku platformy węglanowej cechują się niższą zawartością węgla organicznego, do 1,36% wag. Facja bandstonowa saliny ma bardzo niski rezydualny potencjał genetyczny. Jednakże skała ta prawdopodobnie zawierała znaczną ilość algowej materii organicznej, której pierwotny potencjał węglowodorowy wyczerpał siępodczas przeobrażenia termicznego. W wyniku tego facja bandstonowa saliny została zakwalifikowana do efektywnych skał macierzystych. W dolomicie głównym analizowanego obszaru dominuje kerogen ropotwórczy II typu z nieznacznym udziałem kerogenu typu I i III. Zidentyfikowany kerogen II typu jest w klasie wysokiego potencjału węglowodorowego. Stopień przeobrażenia materii organicznej badanych utworów odpowiada przejściu generowania fazy mikrobialnej w początkowe stadia generacyjne okna ropnego.

EN

Basedon the results ofgeochemical analyses, 56 Main Dolomite profiles in the Kamień Pomorski carbonate platform and its immediate vicinity were characterised for source rock properties. The highest TOC values, to 5.8% wt., could be observed in the mudstone fades in the bay of basin plain. Mudstone fades in the shallower part of the basin plain and in the slope of the carbonate platform had a lower TOC, down to 1.36% wt. The boundstone fades in the saline zone had a very low residual genetic potential. However this rock probably contained algal organic matter which initial hydrocarbon potential run down during thermal maturation. As a result, the boundstone fades was classified as efficient source rock. In the analysed area of the Main Dolomite, oil-prone kerogen type II dominates. The share of kerogen type I and III is small. Identified kerogen II type has a high hydrocarbon potential. The organic matter in the analysed Main Dolomite strata is immature or low mature which corresponds to the end of microbial phase generation and beginning of the "oil window "phase.