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EN
The Jabłonna Reef, one of the reefs formed in Wuchiapingian time in the western part of the Wolsztyn palaeo-High (SW Poland), is characterized by quite irregular outlines and consists of three separate reef bodies (ca. 0.5–1.5 km2 each; the thickness of the reef complex is usually >60 m). It is penetrated by four boreholes, which show two distinct phases of bryozoan reef development during deposition of the the Zechstein Limestone. The first one occurred early in the depositional history and botryoidal aragonitic cementation played a very important role in reef formation. This phase of bryozoan reef development terminated suddenly; one possible reason was that a relative change of sea level – first a fall and then a rise – disturbed the upwelling circulation. Consequently, bioclastic deposition predominated for a relatively long time until the second phase of bryozoan reef development occurred, but the latter was not accompanied by dubious early cementation. During this second phase, reticular fenestellid bryozoans were predominant. Subsequently, microbial reefs developed and abound in the upper part of the Zechstein Limestone sections. The general shallowing-upward nature of deposition in the Jab³onna Reef area resulted in reef-flat conditions with ubiquitous, microbial deposits, in the central part of the Jab³onna Reef. Then, the reef-flat started to prograde and eventually the entire Jab³onna Reef area became the site of very shallow, subaqueous deposition. Five biofacies are distinguished in the Jab³onna Reef sections: the Acanthocladia biofacies at the base, then mollusc-crinoid, brachiopod-bryozoan, Rectifenestella and at the top, stromatolite biofacies. They represent a shallowing-upward cycle, possibly with some important fluctuation recorded as the distinctive lithofacies boundary, corresponding to the Acanthocladia/mollusc-crinoid biofacies boundary. The 13C curves of the Jab³onna 2 and Jab³onna 4 boreholes permit correlation of the trends in the middle parts of both sections and confirm the strong diachroneity of the biofacies boundaries, with the exception of the roughly isochronous Acanthocladia/ mollusc-crinoid biofacies boundary. The presence of echinoderms and strophomenid brachiopods indicates that until deposition of the lower part of the Rectifenestella biofacies, conditions were clearly stenohaline. The subsequent elimination of stenohaline organisms and progressively poorer taxonomic differentiation of the faunal assemblage are characteristic for a slight, gradual rise in salinity. The taxonomic composition of organisms forming the Jab³onna Reef shows a similarity to reefs described from England and Germany, as well as the marginal carbonate platform of SW Poland. Filled fissures were recorded in the lower part of the Jabłonna Reef. The aragonite cementation recorded in some fissure fillings implies that they originated in rocks exposed on the sea floor and are neptunian dykes.
EN
The Buila-Vânturariţa Massif consists of massive Upper Jurassic reef limestones (Kimmeridgian–Tithonian) and Lower Cretaceous (Berriasian–Valanginian, and Barremian–?Lower Aptian) deposits. Besides corals and stromatoporoids, a wide range of micro-encrusters and microbialites has contributed to their development. In this study, the authors describe briefly and interpret the main facies associations and present the microfossil assemblages that are important for age determination. The distribution of facies associations, corroborated with the micropalaeontological content and early diagenetic features, indicate different depositional environments. The carbonate successions show the evolution of the Late Jurassic–Early Cretaceous depositional environments from slope and reef-front to internal-platform sedimentary settings, including peritidal environments in the lowermost Cretaceous. Early diagenesis, represented by synsedimentary cementation in the form of micritization (including cement crusts in the reef microframework), followed by dissolution, cementation and dolomitization in a meteoric regime, and void-filling late cementation during the burial stage.
EN
Dolomitisation was the main diagenetic process in the Upper Permian Zechstein Limestone of the Wolsztyn High-dolomite cementation (“over-dolomitisation”) also occurred. The rocks studied usually have a mixed mineralogy and represent a continuous spectrum from pure limestone to pure dolomite. This is due to varying degrees of dolomitisation, dolomite cementation and dedolomitisation. There are two main types of dolomite: replacement dolomite (mostly planar unimodal dolosparite mosaics that are mainly fabric-destructive) and cement dolomite (planar isopachous rims and pore-filling non-planar saddle-dolomite crystals). The timing of dolomitisation and dolomite cementation is difficult to ascertain, but comparing petrographical and geochemical data indicates that the reef carbonates were dolomitised shortly after deposition in a near-surface sabkha/seepage-reflux and then in burial systems. It seems that many of the dolomites gain their present isotopic composition when buried in relatively high-temperature conditions, as shown by low oxygen isotopic ratios ( δ18O as low as –9‰ PDB) and the presence of saddle dolomite. No isotopic support for a water-mixing mechanism is documented.
EN
Neptunian dykes were recently recorded within the Middle Miocene (Upper Badenian and Lower Sarmatian) Medobory reef complex of the Carpathian Foreland in western Ukraine. The Upper Badenian reefs are cut by a regular, semi-perpendicular network of intersecting fissures that penetrate the Badenian reef limestone down for more than 10 m. The dykes are filled by several generations of Sarmatian microbialites coating the fracture walls and by bedded bioclastic sediment (including foraminifers) which is more important volumetrically. The fissure fillings containing both the Sarmatian material as well as rare clasts of Badenian rocks indicate that the fissures were open during the onset of Sarmatian deposition. They originated following the emergence and fracturing of the Badenian limestones, either due to fault tectonics at basin margins induced by basin subsidence, around the Badenian-Sarmatian boundary, or to gravitational instability of large lithified Badenian reef bodies. Only one phase of fracture opening occurred. The filling of fractures was episodic, with pulses of cementation and microbial growth and sediment injection. Four different foraminiferal assemblages recorded in the neptunian dykes indicate that the process of fracture filling was long-lasting.
EN
The Middle Miocene (Upper Badenian) coralline algal reefs of Western Ukraine contain caverns (up to 1 m across) and fissures that are filled by Sarmatian deposits: marly clays, clayey carbonate sand and bioclastic, bryozoan-rich sand. These deposits often contain abundant and very well preserved calcareous benthic foraminifera; agglutinated forms have not been recorded. Foraminiferal tests quite commonly show morphological abnormalities, e.g. twin forms or tests with irregularities in size or shape in last chambers. Each of the three analysed samples is characterized by a different foraminiferal assemblage: Elphidium aculeatum assemblage, Hauerinidae assemblage and Lobatula lobatula assemblage. These assemblages are characteristic for a shallow marine environment. Low taxonomic diversity and high dominance or monospecific foraminiferal assemblages indicate generally a restricted marine environment. It seems that the increasing salinity and very high-energy environment were the most probable factors controlling the composition of the foraminiferal assemblages.
PL
Górnobadeńskie rafy koralowe zachodniej Ukrainy posiadają kawerny o przekroju do 1 m oraz szczeliny, które obecnie są wypełnione osadami sarmackimi – iłami marglistymi i zasilonym piaskiem węglanowym i bioklastycznym, często mszywiołowym. Osady te często zawierają liczne i bardzo dobrze zachowane węglanowe otwornice bentosowe; nie stwierdzono natomiast otwornic zlepieńcowatych. Dość częste są skorupki z morfologicznymi nieprawidłowościami, np. formy bliźniacze albo skorupki z nieregularnością rozmiaru lub kształtu ostatnich komór. Każda z trzech próbek zawiera inny zespół otwornicowy: w pierwszej występuje zespół z Elphidium aculeatum, druga zawiera zespół z Hauerinidae, a trzecia – zespół z Lobatula lobatula. Wszystkie te zespoły są charakterystyczne dla środowiska płytkomorskiego. Niskie zróżnicowanie taksonomiczne i wysoka dominacja lub jednogatunkowe zespoły otwornicowe wskazują na ogólnie ograniczone środowisko morskie; wydaje się, że w takich warunkach najbardziej prawdopodobnym czynnikiem warunkującym skład zespołów otwornicowych było podwyższone zasolenie i środowisko bardzo wysokoenergetyczne.
PL
Przedstawiono charakterystykę litologiczną utworów mioceńskich występujących na Roztoczu i terenach sąsiednich (zachodnia Ukraina). Utwory dolnobadeńskie rozpoczynają się transgresywnymi piaskami i piaskowcami kwarcowymi; w wyższej części obocznie przechodzą w margle i wapienie litotamniowe. Powstały w płytkowodnym, wysokoenergetycznym morskim środowisku sedymentacji, o zmieniającym się w czasie chemizmie wód. Środkowobadeński gips pierwotny tworzy szeroką brzeżną platformę siarczanową; w trakcie jego depozycji następowały znaczne wahania składu chemicznego solanek. W płytszych częściach zbiornika na gipsach występują utwory wapienia ratyńskiego, związane genetycznie z transgresją morską. W późnym badenie obszar Roztocza był strefą tranzytową dla materiału bioklastycznego i terygenicznego, w jej obrębie odbywało się przemieszczanie materiału ziarnowego związane z falowaniem i prądami wywołanymi przez falowanie oraz z ruchami masowymi. Węglany dolnosarmackie Roztocza cechują się nietypowym wykształceniem facjalnym oraz ubogim składem taksonomicznym organizmów, wskazującym na anomalne warunki środowiskowe – obniżone zasolenie wody i silne jej przesycenie względem węglanu wapnia.
EN
Lithological characteristics of Middle Miocene strata of the Roztocze region (SE Poland and western Ukraine) is summarized. The Lower Badenian sequence begins with transgressive quartz sands and sandstones that subsequently are passing laterally into marls and coralline algal limestones. They originated in shallow-water, high-energy marine environment. The chemistry of waters at that time as well as during subsequent gypsum sedimentation fluctuated quite considerably. Middle Badenian gypsum deposits build a wide marginal sulphate platform. In shallower parts of the basin the Ratyn Limestone deposits cover gypsum; they are related genetically to new marine transgression. During the Late Badenian the Roztocze region was a transit zone for bioclastic and terrigenous material, and the grainy material was transported owing to waves and wave-generated currents as well as mass movements. The Lower Sarmatian carbonates of Roztocze show a typical facies and poor taxonomic composition of fossil assemblages that indicate abnormal environmental conditions – decreased water salinity and its oversaturation in respect to calcium carbonate.
EN
Three sections (Rebro, Lyalintsi and Velinovo) of the Upper Jurassic-Lower Cretaceous carbonate sequences from the Lyubash unit (Srednogorie, Balkanides, SW Bulgaria) have been studied for elucidation of biostratigraphy and palaeoenvironmental evolution. Palaeontological studies of foraminifera, supplemented by studies of calcareous dinoflagellate cysts and corals, enabled the determination of the Oxfordian-Valanginian age of the analysed sequences. They were deposited on the Dragoman Block (western part of the Moesian Platform), and during Mid-Late Cretaceous included to the Srednogorie. A possible Middle to Late Callovian age of the lowermost part (overlying the Bajocian-Lower Bathonian Polaten Formation) of the studied sections assumed till now has not been confirmed by the present studies. Eleven facies have been distinguished and attributed to depositional environments. Marine sedimentation on a homoclinal ramp started in the Oxfordian and till the Early Kimmeridgian - in all three sections - was dominated by fine-grained peloidal-bioclastic wackestones to grainstones. Since the Late Kimmeridgian, when a rimmed platform established, facies pattern underwent differentiation into (i) the inner platform (lagoon and tidal flat facies) - only in Velinovo, (ii) reef and peri-reef facies/bioclastic shoals - mainly in Lyalintsi, and (iii) platform slope - mainly in Rebro. Sedimentation generally displays a shallowing-upward trend. Two stages in evolution of the rimmed platform are postulated. The mobile stage lasting till the Tithonian/Berriasian boundary was followed by a more stable stage in the Berriasian to Valanginian time. Reefs are developed mainly as coral-microbial biostromes, lower coral bioherms or coral thickets, in the environment of moderate energy and sedimentation. They contain highly diversified corals (72 species). Micro- bialites contributed to the reef framework, but they never dominated. Locally, microencrusters and cement crusts formed important part of reefal framework. During the mobile stage of the platform evolution a relative sea-level rise interrupted reef development, as evidenced by intercalations of limestones with Saccocoma. During the second stage high carbonate production and/or regressive eustatic events, not balanced by subsidence, decreased accommodation space, limiting reef growth and enhancing carbonate export to distal parts of the platform.
EN
The Sciacca area, in Southwestern Sicily, belongs to the external zone of the Neogene Maghrebian thrust and fold belt. Two different groups of south-verging thrust sheets crop out in this area: the so called "Saccense" units that consist of thick Mesocenozoic neritic and pelagic platform carbonates; the "Sicanian" units made of Permian to Cenozoic deeper-water sediments. The tectonic boundary between Saccense and Sicanian units runs NW-SE from Monte Genuardo to Caltabellotta. This boundary is orthogonal to the main thrust fronts and nearly parallel to the direction of thrust propagation. Thrust-top-basin deposits of Pliocene age obscure the tectonic relationships along this alignment leaving different solutions open for its structural interpretation and for the palinspastic restorations between platform and basin-derived units. Recent sedimentological and stratigraphical studies focused in this zone document the presence of Upper Triassic reef limestones in the Saccense units (Pizzo Telegrafo unit), close to the tectonic alignment. The macro and microfacies analysis reveal a typical Dachstein-type reef composition of these deposits. As consequence they can be interpreted as markers of platform edges facing high-energy, open marine basins. The collected data are thus consistent with the presence of a Late Triassic platform-basin transition close to the present-day tectonic boundary. An intense Jurassic paleotectonic activity along this margin is proved by in situ brecciation and the presence of large polyphase neptunian dykes crosscutting the reef deposits and the overlying Lower Jurassic platform limestones (Inici Formation). The dykes are filled up by Middle to Upper Jurassic Rosso Ammonitico type condensed limestones. Basaltic pillow lavas occur as thick wedges intercalated to the Jurassic pelagic limestones. They indicate repeated episodes of (trans)tensional stresses along the paleomargin. An anomalous thin Cretaceous to Miocene sedimentary cover (Scaglia type calcilutites and glauconitic sandstones) is punctuated by deep erosional truncations and megabreccias. These sediments fill up later generations of neptunian dykes confirming the paleotectonic activity in this zone throughout the Jurassic-Miocene times. In the Sicanian basinal units flanking the tectonic alignment the influence of the platform paleomargin is recorded by extensive Lower Jurassic carbonate aprons interbedded to cherty calcilutites. Upper Triassic reef-derived elements are common constituents of these clastics as recently documented at Campofiorito and Monte Triona. Looking at the present day structural relationships in the studied area we can conclude that the Triassic/Jurassic paleomargin has played an important role as major transpressional dextral escape during the Neogene Sicanian mountain building.
EN
The Middle Miocene (Lower Sarmatian = Middle Serravallian) carbonate buildups called “serpulid-microbialite reefs” that occur in the Medobory and Roztocze regions (Paratethys Basin, western Ukraine and southeastern Poland) are composed mainly of calcite precipitates. Skeletal organisms represented by serpulid tubes and bryozoans (in places) are of minor importance and comprise merely a few percent of the rock volume. They are overgrown with micritic peloidal microbialites that are the major reef component. The microbialites and serpulids/bryozoans make together a porous reef framework that is usually filled up with abundant synsedimentary fibrous cements and micritic internal sediments. Other biota is taxonomically impoverished but often rich in individuals and comprises few species of bivalves, gastropods, benthic foraminifers. In places, the serpulid-microbialite limestone masses are incrusted with coralline algae, bryozoans and nubeculariid foraminifers. Bivalve coquinas, bioclastic limestones, breccias and conglomerates are associated with the reefs. The synsedimentary precipitates represented by microbialites and fibrous cements have quite unusual geochemical characteristics. They are composed of Mg-calcite with 5–6 mole % MgCO3 in average with a very high content of strontium (1000–1650 ppm Sr). The precipitates are enriched in heavy oxygen and carbon isotopes. Fibrous cements exhibit the highest values (18O ca. +1.5 [PDB] and 13C 2.8 [PDB]. It is generally believed that in the Early Sarmatian the Paratethys was a brackish basin due to restricted connections to theWorld Ocean. This is indicated by taxonomically poor biotic assemblages that inhabited the basin. On the other hand, however, the predominance of calcitic precipitates (such as microbialites and synsedimentary cements) is indicative of water highly supersaturated in respect to calcite due to high carbonate alkalinity content. Oxygen isotopic composition of the precipitates indicates that the brackish water, in which the reefs originated, had to be enriched in the heavy oxygen isotope due to strong evaporation. The low Mg content in calcite (if compared to modern tropical settings) could be the result of a relatively low precipitation temperature coupled with lower Mg/Ca ratio in Miocene than today, and the elevated Sr content may be indicative of a high precipitation rate resulting from high supersaturation. It seems therefore that the origin of the serpulid-microbialite buildups is related to a peculiar interplay of regional and local controls in the Sarmatian Paratethys. First, the relative isolation of the entire Paratethys basin resulted in the brackish water environment that could be inhabited by taxonomically poor opportunistic biota only and simultaneously enabled blooming of microbial communities. Second, a strong evaporation of the brackish water with high alkalinity content caused a supersaturation in respect to calcium carbonate and consequently a widespread precipitation of calcite (including calcification of microbial mats).
10
Content available remote Dynamika rozwoju utworów koralowych środkowego oksfordu okolic Bałtowa
EN
Coral facies developed on the Middle Oxfordian carbonate ramp were controlled in the region of Bałtów, NE margin of the Holy Cross Mts., Poland, by syndepositional activity of extensional fault blocks. Elevated parts of sea bottom were occupied since Early Oxfordian time by sponge bioherms successively colonized by coral reefs when grown up to the sea level. Micritic sedimentation prevailed in interbioherm denivelations. This micritic succession was replaced by soft-bottom coral buildups constructed by flat coral colonies, typical of a relatively quiet environment of the depths 20-70 m, and finally by coarse bioclastic grainstones and oncolites which are interpreted as talus of the coral reef constructed on tops of former sponge bioherms by branched and hemispherical coral colonies in very dynamic and extremely shallow water conditions.
PL
Poziom wapienia cechsztyńskiego stał się jednym z najbardziej perspektywicznych poziomów zbiornikowych z punktu widzenia poszukiwań w Polsce. Rejon paleoelementu zwanego wałem wolsztyńskim był na początku transgresji morza cechsztyńskiego naturalnym miejscem sedymentacji typu rafowego na lokalnych paleopodniesieniach szelfu. Rafy te w wyniku gry naftowej stały się pułapkami akumułującymi gaz migrujący z utworów wieku karbońskiego. Dane sejsmiki 3D integrowane z pozostałymi rodzajami danych pozwalają na wydzielenie ciał rafowych-pułapek w procesie interaktywnej, komputerowej interpretacji opartej na czynniku litofacjalnym. Wykorzystuje ona informacje dostarczane przez geofizykę otworową i elementy paleogeografii możliwe do pozyskania z danych sejsmiki 3D. Wydzielenie pułapek umożliwia przejście do następnego etapu, polegającego na określeniu ich geometrii i porowatości. Pozwala to obliczyć zasoby złoża. Zastosowane procedury interpretacyjne zostały potwierdzone rezultatami 12 otworów odwierconych na rafie Kościan i czteroma następnymi na rafach Bonikowo, Białcz, Brońsko i Kokorzyn. Ich efektem jest osiągnięcie, niespotykanej w polskiej praktyce poszukiwań węglowodorów, skuteczności wierceń.
EN
The Zechstein LHmestone formation became one of the most perspective reservoirs as far as the to exploration carried out in Poland is concerned. The region ofpalaeoelement, referred to as the Wolsztyn ridge, used to be a natural sedimentation place of the reef type on the local palaeoelevation of the shelf at the beginning of the Zechstein sea transgression. As a result of hydrocarbon play, these reefs became accumulation traps for the migrating gas that takes it origin in the strata of the Carboniferous age. The 3D seismic data integrated with other types of data allow for the selection of reefs-traps in the process of interactive, computer analysis based on the lithofacies factor. It makes use of the information supplied by well logging and elements ofpalaeogeography which can be acquired from 3D seismic data. The selection of traps open the possibility of passing to the next stage which consists in determining geometry and porosity. The determination of the said allows to calculate reservoir reserves. The applied interpretation procedures have been confirmed by the results received in 12 wells in the Kościan reef and four others in the Bonikowo, Białcz, Brońsko and Kokorzyn reefs. The effect is the efficiency of drilling unprecedented so far in Polish practice of exploration.
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