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1

Slope failure on a Cambrian carbonate platform, mass-flow transitions and resulting complex deposit

Wang Zhaopeng, Liu Jiaye, Van Loon A. J. (Tom), Zhu Decheng, Qin Peng, Han Zuozhen

Geological Quarterly

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2020

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Vol. 64, No. 1

3--15

EN

The quiet environment of the carbonate platform in the epeiric sea that existed during the Cambrian between present-day China and Korea was occasionally affected by processes that have hitherto not been described from such a setting. A conglomerate was found in the Middle Cambrian Gushan Formation near Chengouwan (Shandong Province, E China), eroded into the underlying sediments. The conglomerate is explained as a deposit consisting of material that was eroded up-slope when slope-failure took place, resulting in a slump that passed into a high-density debris flow with erosive power that passed, in turn, again into a slump. The slump came to rest when it lost its momentum on a less inclined part of the basin slope. Immediately after deposition, fluidization occurred in the lower part of the slump deposit, as proven by a funnel-shaped water-escape structure and a lateral injection of some metres long of brecciated material.

2

Analiza mikrofacjalna dolomitu głównego (Ca2) we wschodniej części wielkopolskiej platformy węglanowej

Krzyżak Ewelina

Przegląd Geologiczny

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2019

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Vol. 67, nr 3

172--175

EN

Investigation of the Permian Basin in the western part of the Polish Lowland was initiated in 1961 when the Rybaki field was discovered - the first one outside the Carpathians in Poland. The Main Dolomite (Ca2) in the eastern part of the Wielkopolska Platform, located in western Poland, is characterized by a significant variety of microfacies, hence this research is aimed at better interpretation and understanding of depositional environments of current reservoir rocks as well as possibility of identification of facies distribution within the investigated carbonate platform. A detailed microfacies analysis of the Main Dolomite was conducted, which was supported by core logging. The author interpreted depositional environments and generated a 3D model of the top of the Main Dolomite using seismic reflection data. An attempt to correlate microfacies between the analyzed wells was also performed. Integrated analyses of thin sections and drill cores from 4 wells allowed me to interpret the depositional environments of the Main Dolomite. The generated 3D model of the top of the Main Dolomite provided a better insight into subsurface tectonics, paleogeography of the analyzed area and a better understanding of depositional lithofacies environments.

3

The siliciclastics/carbonates shift in the Jurassic of the Western Caucasus (central northern Neo-Tethys): reconsidering research over the last 50 years

Ruban Dmitry A.

Geologos

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2019

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Vol. 25, No. 2

153--162

EN

A chain of carbonate platforms evolved in the northern Neo-Tethys during the Late Jurassic, but current knowledge remains incomplete as long as data from several larger regions, such as the Western Caucasus, are not included. In order to fill this gap, it is here suggested to reconsider the information accumulated chiefly during Soviet times. Although these data are too general, they still matter with regard to some regional characteristics and tentative interpretations. Available data on the spatio-temporal distribution of Bajocian-Callovian sedimentary rocks are summarised in a novel way which permits documentation of depositional trends at six representative localities in the Western Caucasus. The extent of the carbonate platform increased at two localities since the Late Callovian and at a third since the Middle Oxfordian. Three additional sites were characterised either by non-deposition or deep-marine sedimentation. The onset of carbonate platform development marked a remarkable shift from chiefly siliciclastic to carbonate deposition, although this event was not sudden everywhere. The Bathonian pulse of tectonic activity, coupled with the eustatic sea level rise, allowed shelves to expand during the Callovian-Oxfordian, with a reduction in siliciclastic input from islands and seawater that became well oxygenated and warmer. These conditions were conducive to biogenic carbonate production, allowing the carbonate platform to expand subsequently.

4

Palaeoenvironmental changes recorded in the oxygen and carbon isotope composition of Kimmeridgian (Upper Jurassic) carbonates from central Poland

Wierzbowski Henryk

Geological Quarterly

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2019

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Vol. 63, No. 2

359--374

EN

Oxygen and carbon isotope ratios of well-preserved calcitic bivalves from the Lower-lowermost Upper Kimmeridgian of Central Poland (SW margin of the Holy Cross Mountains) have been studied to reconstruct palaeoenvironmental conditions and variations in ancient water chemistry. Low and scattered δ18O and δ13C values of bivalve shells from shallow carbonate deposits of the Hypselocyclum and the Hypselocyclum-Divisum zone boundary (-3.5 to -1.5, and 2.6 to 4.0‰, respectively) are a result of salinity changes, and local variations in the composition of dissolved inorganic carbon (DIC) in conditions of restricted water circulation. A slight increase in bivalve δ13C values and more densely clustering of δ18O values is observed after the marine transgression at the Divisum-Mutabilis zone boundary. A global decrease of δ13C values of marine carbonates is partly recorded in Lower-lowermost Upper Kimmeridgian bulk carbonates from central Poland (from the Radomsko Elevation and the Wieluń Upland). Local negative shifts and the data scatter are, however, observed in rocks deposited in a very shallow environment of carbonate platforms during the Platynota and Hypselocyclum chrons. This interval corresponds to the uppermost part of the lowstand systems track of a major regressive trend, which had started already in the Late Oxfordian.

5

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

Szczurek S., Bąk M., Dulemba P.

Geotourism / Geoturystyka

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2016

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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.

6

Analiza statystyczna parametrów mikrofacji dolomitu głównego w granicznej strefie platformy węglanowej

Semyrka R., Jarzyna J. A., Krakowska P. I., Semyrka G.

Gospodarka Surowcami Mineralnymi

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2015

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T. 31, z. 1

123--140

PL

Duża liczba wyników badań laboratoryjnych parametrów zbiornikowych dolomitu głównego na obszarze platformy węglanowej, w rejonie wschodniej części platformy Gorzowa, w zatoce Noteci wraz z mikroplatformą Krobielewka, na półwyspie Grotowa, oraz na fragmencie platformy wielkopolskiej, sięgającym rejonu Pniew umożliwiła wykonanie wiarygodnych analiz statystycznych. Standardowe badania na próbkach skał (gęstości objętościowej, porowatości efektywnej i przepuszczalności fizycznej) wzbogacone zostały o wyniki pomiarów porozymetrii rtęciowej. Wyniki badań laboratoryjnych, przede wszystkim porozymetrii rtęciowej, rozszerzyły znacznie informację o skale zbiornikowej (dolomicie głównym) i przyczyniły się do wydzielenia różnorodnych mikrofacji oraz stref paleogeograficznych. Na podstawie wyników przeprowadzonej analizy statystycznej porównano parametry petrofizyczne trzech mikrofacji i stwierdzono, że utwory ziarnozwięzłe charakteryzowały się najlepszymi właściwościami zbiornikowymi. Dla tych utworów stwierdzono wysoką średnią porowatość efektywną oraz wysoką średnią porowatość dynamiczną dla gazu i ropy. Utwory te charakteryzowały się także wysoką przepuszczalnością. [...]

EN

Reliable statistical analysis was carried out for the Main Dolomite reservoir parameters on the area of carbonate platform in the vicinity of the east part of Gorzów Platform, in the Noteć Bay, together with Krobielewko Microplatform, on the Grotów Peninsula and on the part of Wielkopolska Platform, reaching Pniewy region thanks to large number of laboratory measurements results. The standard measurements on the core samples (bulk density, effective porosity and absolute permeability) were enriched by mercury porosimetry results. Laboratory measurements results, especially mercury porosimetry, extended considerably information about the reservoir rock (the Main Dolomite) and contributed to the separation of diverse microfacies and paleogeographic zones. Petrophysical parameters of the three microfacies were compared based on the results of statistical analysis. It was found that grainstones were characterized by the best reservoir parameters. For these microfacies high average effective porosity and average dynamic porosity for oil and gas were discovered. Additionally, grainstones characterized by high permeability. [...]

7

Small-scale cyclic deposition in the Frasnian (Upper Devonian) of the Holy Cross Mountains, Poland

Vierek A.

Geologos

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2014

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Vol. 20, No. 4

239--258

EN

In sections exposing Frasnian limestones at five outcrops in the Holy Cross Mountains, five lithofacies (L1 to L5) that represent upper slope to basinal environments are identified. These lithofacies are characterised by dark-coloured micritic limestones–marly shale couplets with many light-coloured intercalations of fine- to coarse-grained limestones (= event beds). This lithofacies pattern characterises mostly low-energy domains punctuated by storm episodes. In addition, these upper-slope to basinal lithofacies are arranged into small-scale, coarsening-upward beds and cycles. The cycles are locally composed of fining/thinning-upward beds. The small-scale cycles have a calculated duration of 19 to 42 kyr. The differential thickness of beds and cycles within and between sections was probably caused by differential subsidence and local tectonics. Possible evidence of tectonic activity is also related to a difference in number of cycles recorded in the time-equivalent sections. The recognised cyclicity shows sea-level fluctuations and a few deepening episodes. Some of them are correlated with the Timan global eustatic events. However, local tectonics and episodic subsidence may have played a significant role in recording brief deepening pulses. Thus, low-amplitude sea-level changes were major factors in platform generation and evolution in the Frasnian of the Holy Cross Mountains modified by local, block-related subsidence.

8

Prolific development of pachythecaliines in Late Barremian, Bulgaria: coral taxonomy and sedimentary environment

Kołodziej B., Ivanov M., Idakieva V.

Annales Societatis Geologorum Poloniae

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2012

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Vol. 82, No. 4

291–-330

EN

Diversified and abundant corals of the suborder Pachythecaliina (order Hexanthiniaria) are described from Upper Barremian, biostromal reefs of the Emen Formation, Lovech Urgonian Group, north central Bulgaria. The corals are mostly of the phaceloid growth form and represent 14 species (six new), 12 genera (three new), belonging to five families. Pachythecaliines occur with the small, monopleurid cylindrical rudist Mathesia darderi. The rudists frequently are densely clustered, occur between coral branches or are in contact with them. Other corals, with the exception of the phaceloid Calamophylliopsis, and other rudists, are rare. Non-laminated microbialite crusts provided additional, structural support for bioconstruction development. Microbialites (automicrites) can be interpreted as a product of microbial activity, or alternatively, as a result of carbonate precipitation, brought about by non-living organic substrates (organomineralization s.s.). In addition to microbialites, metazoans are encrusted by heterotrophic skeletal microorganisms, while photophilic and oligotrophic microencrusters, usually common in other coral-bearing limestones of the Emen Formation, are very rare. The section at the Rusalya Quarry (NW of Veliko Tarnovo), about 42 m thick, provides the sedimentary and environmental context for the reefal biostromes. The vertical biotic and sedimentary succession displays a general shallowing trend: from the outer carbonate platform with bioclastic limestones containing small boundstone patches (corals, but not pachythecaliines, Lithocodium aggregatum), to the inner platform with rudist biostromes. The pachythecaliine-rich biostromes, 2.5 m thick, were developed in a low-energy environment, referred to the distal part of the rudist-dominated area of the platform. The development of microbialites was facilitated by a low sedimentation rate, and possibly by increased nutrient level. Only poorly diversified and non-phaceloid pachythecaliines occur in other coral-rich limestones and marls of the Urgonian complex in Bulgaria. The assemblage described is the most remarkable, Early Cretaceous coral community worldwide, with regard to pachythecaliines. Phaceloid pachythecaliines are only more common in the Upper Jurassic rocks, being particularly diversified in the Tithonian–Lower Berriasian Štramberk Limestone (Czech Republic) and its equivalent in the Polish Outer Carpathians. However, their sedimentary context differs from that described for the corals of the Emen Formation.

9

Corals from the Tithonian carbonate complex in the Dąbrowa Tarnowska–Szczucin area (Polish Carpathian Foreland)

Morycowa E.

Annales Societatis Geologorum Poloniae

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2012

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Vol. 82, No. 1

1–-38

EN

The studied corals have been collected from cores of boreholes located in the central part of the Polish Carpathian Foreland in the Dąbrowa Tarnowska–Szczucin area. The Jurassic complex in this area presents a continuous stratigraphic section from the Upper Callovian to Tithonian, locally passing to the Lower Cretaceous (Berriasian). Its thickness exceeds 1,100 m in this area. This complex is composed of marine, mainly shallow-water deposits. The corals occur within the upper part of the Upper Jurassic (Tithonian) deposits, almost entirely within the Swarzów Limestone Formation (= coral-algal limestone formation). This occurrence marks the northernmost extent of Tithonian shallow-water corals in Poland and one of the northernmost in Europe. 42 coral species (among them 14 in open nomenclature) were identified in deposits of this formation. They include two new species: Complexastrea magna and Complexastrea dabroviensis. All taxa, except one, belong to the order Scleractinia. The described assemblage displays a Late Jurassic character. The broader stratigraphic span is assigned to some species, which are quoted from the Middle Jurassic and some species lasted until the Early Cretaceous, Berriasian and/or Valanginian.

10

The Steinplatte complex (Late Triassic, Northern Calcareous Alps, Austria) - subsidence-controlled development of a carbonate-platform-to-intrashelfbasin-transition

Kaufmann B.

Acta Geologica Polonica

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2009

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Vol. 59, no. 3

341-357

EN

In Rhaetian (Late Triassic) times, the Hauptdolomit/Dachstein carbonate shelf situated at the passive continental margin of the northwestern Tethys was characterized by an extensional tectonic regime. Rifting and spreading movements fragmented this shelf into a loosely fitted mosaic of fault-bounded blocks characterized by a differential subsidence pattern. This is expressed in significant thickness variations of platform carbonates and in the formation of the intrashelf Kossen Basin. In this study, it can be demonstrated that tectonic subsidence triggered the development of a carbonate platform margin and that the influence of eustatic sea-level changes was negligible. The Steinplatte complex developed at the transition of the Kossen Basin to the Dachstein Carbonate Platform. Small-scale isolated carbonate mounds situated on a smoothly inclined homoclinal ramp characterized the initial phase and acted as nuclei of further carbonate buildup growth. However, only the ideal palaeogeographic position far enough away from the carbonate-suppressive terrigenous influence of the Kossen Beds, combined with vigorous carbonate production stimulated by rapid subsidence-caused sea-level rise, favoured continuous mound growth. Once established, the carbonate buildup was characterized by rapid aggradational growth, developing a palaeogeographic high with a steep slope and a depression with decreased sedimentation behind, several kilometres distant from the Dachstein Carbonate Platform. Contemporaneously, isostatic adjustment caused an accommodation minimum on the nearby margin of the Dachstein Carbonate Platform leading to its westward progradation. Fading out of subsidence caused filling of the former depression in the back of the buildup by prograding shallow-water Dachstein Limestones. Thus, a new platform margin was established in the Steinplatte area, elevated almost 200 m above the adjacent Kossen Basin. At the Triassic-Jurassic boundary, the Steinplatte complex was subjected to subaerial exposure by a sudden tectonic uplift followed by a rapid isostatic drop. Emergence is indicated by levels of karstified limestones directly underlying supposed exposure surfaces. Final drowning of the Steinplatte complex as well as of the whole Dachstein Carbonate Platform is indicated by the cover of Early Jurassic (Sinemurian) deeper water, ammonitebearing limestones (Adnet Formation).

11

Układ faz węglowodorowych w obszarze złożowym Lubiatów - Międzychód - Grotów (LMG)

Słupczyński K., Machowski G., Papiernik B., Semyrka R.

Geologia / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

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2008

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T. 34, z. 3

469-487

PL

Dla strefy złożowej Lubiatów - Sowia Góra - Międzychód - Grotów (LMG), umiejscowionej w obszarze platformy węglanowej i na jej przedpolu, w poziomie dolomitu głównego Ca2, kryteriami równowagi statycznej zachodzącej w ośrodkach porowo-szczelinowych wypełnionych oddzielnymi fazami węglowodorowymi, wyznaczono fazowe powierzchnie rozdziału kondensatowego gazu ziemnego od nasyconej gazem ropy naftowej. Udowodniono łączność hydrauliczną pomiędzy poszczególnymi komercyjnymi polami zasobów reprezentującymi oddzielne złoża węglowodorów. Wykazano, że wąskie strefy o miąższości poniżej 15 m, o różnej hipsometrii, spełniają tylko rolę semiprzepuszczalnych ograniczeń komercyjnych pól zasobowych. Wyznaczone powierzchnie rozdziału gazu ziemnego i ropy naftowej znacznie rozszerzają powierzchnię akumulacyjną w obszarze występowania platformy węglanowej i jej przedpola.

EN

For the Lubiatów - Sowia Góra - Międzychód - Grotów (LMG) hydrocarbon reservoir zone, situated within the area of the Main Dolomite carbonate platform and its foreland, interfacial surfaces between natural condensate gas and gas-saturated oil was determined applying the criterion of stable equilibrium in porous-fractured media filled with separate hydrocarbon phases. Hydraulic connection between individual hydrocarbon accumulations was proved. It was evidenced that narrow zones with Main Dolomite thickness less than 15 m and different hypsometric positions play the role of semi-permeable boundaries only. The determined surfaces between natural gas and crude oil considerably extend the accumulation zone in the area of the carbonate platform and its foreland.

12

Storm-dominated deposition on a Frasnian carbonate platform margin (Wietrznia, Holy Cross Mts., Poland)

Vierek A.

Geological Quarterly

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2007

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Vol. 51, No 3

307-318

EN

The Wietrznia quarry in Kielce is situated between the shallow-water Devonian carbonate platform in the Kielce region and the deeper Łysogóry basin. This palaeogeographic setting affected carbonate sedimentation in Late Devonian times. The transitional facies of the Wietrznia Frasnian comprises two over lapping types of deposits: (1) micritic and marly limestone of shelf basin facies and (2) coarse-grained limestone of fore-reef facies. The first type includes laminated- and graded micritic limestone and modular limestone. The second includes intraformational conglomerates and breccias, and crinoidal limestone. The limestones in the middle Wietrznia Beds formed within storm wave basein a shal ow (possibly only a few tens of metres) sea that deepened eastwards. Storms are likely to have been the main cause of erosion and transport. In the western part of the quarry, proximal tempestites show evidence of amalgamation and cannibalism as do some high-energy flat-pebble conglomerates. With abating storm winds, finer-grained graded and laminated limestones accumulated. To ward the eastern part of the quarry, the high-energy effects of near-shore storm waves are less evident; the deposits there are transitional or more distal tempestites.

13

The Torrecilla Reef Complex (Early Kimmeridgian, N Spain): an example of tectonically forced regression

Benito M., Mas R.

Volumina Jurassica

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2006

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Vol. 4, no. 1

79-80

EN

Palaeontological, sedimentological, palaeoecological and/or depositional aspects of most Late Jurassic reefs, specifically coral reefs, have been studied in detail (e.g. see references in Flugel & Flugel-Kahler 1992; Leinfelder et al. 1996; Insalaco et al. 1997; Dupraz & Strasser 2002; among others), but only a few papers deal with their depositional architecture and response to tectonics and/or sea-level change. For example, Leinfelder et al. (1994, 1996) conclude that both eustatic and tectonic changes were important in controlling platform geometry and evolutionary trends in Upper Jurassic reefs. The Early Kimmeridgian Torrecilla Reef Complex in the northern Iberian Basin of Spain consists of a fringing reef composed of eight accretionary units (Alonso et al. 1986-1987;Mas et al. 1997; Benito & Mas 2002, 2006). The first four were deposited along a steep margin. They display down-lapping and off-lapping geometries, and are characterized by poor reef-framework development, large volumes of reworked corals and transported sediment, and limited growth of micro-encrusters.In contrast, deposition of the fifth and younger accretionary units occurred on a shallow platform without a pronounced slope where coral reefs grew in a shallow protected environment (Benito & Mas 2006). The main features of these reefs are: an absence of reef-slope facies, a high proportion of preserved framework elements, relatively low volumes of intrareef sediment, high proportions of terrigenous material, and abundant micro-encrusters and microbialites. These reefs were protected from storm waves by long-shore sand bars, which also protected a very shallow lagoon during the last stage of sedimentation. The Early Kimmeridgian was a period of rising global sea level (Haq et al. 1988; Hallam 2001), a trend apparent across other portions of the Iberian Basin. However, geometry and sedimentary evolution of the Torrecilla Reef Complex is consistent with those of off-lapping reefs that develop during sea-level fall. Thus, we conclude that down-stepping geometries and evolution to progressively shallower environments within the Torrecilla Reef Complex occurred as a result of a tectonically forced regression.

14

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

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

Volumina Jurassica

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2006

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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.

15

Architecture, evolution and hydrocarbon potential of the Late Jurassic - Early Cretaceous carbonate platform in SE Poland and W Ukraine

Gutowski J., Popadyuk V., Urbaniec A., Złonkiewicz Z., Gliniak P., Krzywiec P., Maksym A., Wybraniec S.

Volumina Jurassica

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2006

|

Vol. 4, no. 1

46-48

EN

Well, outcrop, seismic and gravity data were used to construct a series of palaeogeographic maps revealing architecture and evolution of the carbonate platform developed within the northern shelf of Tethys in SE Poland and W Ukraine during Oxfordian through Barremian times. The platform developed in a transition zone between the epicontinental Mid-Polish Trough and the Outer-Carpathian basins. A variety of depositional systems included open shelf spongemicrobial bioherms, coral reefs and oolitic-bioclastic grainstones (see Gutowski et al. 2005, Gliniak et al. 2005) which form hydrocarbon reservoirs in connection with overlying Cenomanian sandstones. Palaeogeographic distribution of the depositional systems evolved in time and was controlled by syn-depositional basement normal/transtensional and strike-slip faulting. A series of analogue models (Gutowski & Koyi 2006a, b) helped to understand a role of strike-slip movements along deep fault zones directed obliquely to the axis of the Mid Polish Through and related to modifications of the extension direction (Gutowski & Wybraniec 2006). These movements controlled fault geometry and the shift of depocenters. Pelagic, black and grey, often bituminous shales (Karolina Formation in Western Ukraine and Cieszyn Shales in Poland), deposited in front of the bioherm-reef belt on the shelf margin, form excellent source rocks. They were deposited since the Late Kimmeridgian due to breaking-up of the peri-Tethyan carbonate platform (Âtramberk type carobonates) and opening of the Silesian Basin (Fig. 1). Consequently, promising traps should mainly be located close to the Late Kimmeridgian - Early Cretaceous shelf margin (Fig. 1), the location of which was inferred using gravity data (Gutowski & Wybraniec 2006). Additional source rocks are of Palaeozoic or Middle Jurassic age. Quality of the reservoirs was often enhanced by diagenesis (e.g. dolomitization), fracturing and pre-Cenomanian karstification. The reservoirs are sealed by Miocene evaporates and/or clays and Upper Cretaceous marls. The Mid-Polish Trough was inverted during the Late Cretaceous and Palaeogene. As a result of Carpathian thrusting, the basin in its southernmost part was covered by the Miocene sediments of the Carpathian foredeep and/or by the Outer Carpathian nappes. Although these tectonic processes modified the evolution of the hydrocarbon system, the Late Jurassic - Early Cretaceous facies development and evolution of the carbonate platform were decisive for the primary distribution of the source rocks and potential reservoirs. Therefore, they should play a key role in hydrocarbon exploration strategy.

16

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

Silva da A. C., Boulvain F.

Geological Quarterly

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2004

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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.

17

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

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

Przegląd Geologiczny

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2003

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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.

18

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

Sylwestrzak J.

Przegląd Geologiczny

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2001

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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.