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EN
Morphometric attributes of 705 stromatoporoid specimens from a number of exposures from the Silurian of Podolia (Ukraine) and the Devonian of the Holy Cross Mountains (Poland), representing a wide array of shallow water carbonate sedimentary environments, have been analysed. Taken into account were such parameters as: general shape of the skeleton, shape of the final growth form (living surface profile), upper surface character, latilaminae arrangement, burial ratio and type of initial surface. A number of new ratios has been introduced, designed mainly to improve the mapping of the outlines of the stromatoporoids upper surfaces. All studied specimens were treated as belonging to one group, and relations between particular attributes were tested. The results were analysed in terms of potential environmental factors influencing stromatoporoid morphometric features. Most of the distinguished attributes are common in the studied group and occur in various combinations, with an important exception of parameters designed to reflect the shape of the skeleton’s upper surface, which are distinctly predominated by convex variants. This indicates that surface concavity was a highly undesired feature among stromatoporoids. Upper surface convexity is interpreted herein as a response to the hazard of clogging of the animals pores by tiny sediment particles suspended in the bottom turbid water layer. Common low burial ratios of final living surface profiles and the occurrence of specimens with a smooth upper surface but a non-enveloping latilaminae arrangement are other reflections of this phenomenon. Burial by sediments and redeposition were also important factors governing stromatoporoid development. No direct arguments indicating photosensitivity of stromatoporoids can be deduced from the presented results. The hitherto postulated allometric tendency among stromatoporoids of starting growth as laminar forms and later adopting consecutively higher profile shapes has not been confirmed here. On the contrary, a tendency for gradual elimination of very high profile forms with increasing stromatoporoid size has been observed. The final shape of a stromatoporoid skeleton was always an effect of a combination of various agents.
EN
A diverse sclerobiont community is described from the Kaugatuma Formation (lower Pridoli) of Saare- maa, Estonia. The stromatoporoid substrates studied here vary from low-domical to high-domical shapes. The community is numerically dominated by microconchids, which may have been characteristic of the sclerobiont fauna in the Pridoli of Baltica. Palaeoconchus aff. tenuis, Anticalyptraea calyptrata, Aulopora sp., sheet-like bryozoans, branching bryozoans, erect bryozoan holdfasts, rugosans, favositids, discoidal crinoid holdfasts, star- like crinoid holdfasts and sheet-like stromatoporoids encrust the domical stromatoporoids. Endobionts are repre- sented by embedded, symbiotic rugosans, Aulopora sp., and two rare borings Trypanites.
3
Content available remote Oxfordian biofacies and palaeoenvironments of Saudi Arabia
EN
The Hanifa Formation in Saudi Arabia consists of a succession of carbonates, over 100 m thick, that were deposited during the Late Jurassic. It consists of two depositional sequences represented by the lower Hawtah Member and an upper Ulayyah Member, respectively. The Hawtah Member is assigned an Early (?) to Middle Oxfordian age, based on brachiopod, nautiloid and coccolith evidence. The Ulayyah Member is assigned a Late Oxfordian age based on ammonite, nautiloid, coccolith and foraminiferal evidence. Detailed study of the microbiofacies and lithology of the late highstand succession of the Ulayyah sequence in 41 cored wells distributed across the Kingdom was aimed at determining the most suitable locations for porous and permeable grainstone accumulation as lithofacies hosts the Hanifa Reservoir elsewhere in the region. A range of palaeoenvironments has been determined, based on integrated biofacies and lithofacies, that include shallow lagoon packstones and foraminiferal dominated grainstones and deep lagoon wackestones and packstones with Clypeina/Pseudoclypeina dasyclad algae. In addition, a series of basin-margin, shoal-associated biofacies are present that include stromatoporoid back-bank packstones and grainstones with the branched stromatoporoid Cladocoropsis mirabilis, bank-crest grainstones with encrusting and domed stromatoporoids. A few wells also proved the presence of intrashelf basin-flank mudstones and wackestones containing sponge spicules, deep marine foraminifera and coccoliths. This study provided control to delimit an intrashelf basin with an irregular margin situated in the east-central part of the Saudi Arabian portion of the Arabian Plate carbonate platform during Late Oxfordian. The basin is flanked by a belt of stromatoporoid banks that pass laterally into a back-bank facies before developing into a lagoon facies. There is no evidence for the shoreline of this basin, although the presence of rare charophytes in the northwest testifies to possible proximity of fluviatile input. The grainstone dominated basin margin facies presents good hydrocarbon reservoir facies and its juxtaposition to intrashelf basinal sediments with potential source rock character provides exciting new prospects in areas hitherto uninvestigated for hydrocarbon reservoirs.
EN
Well preserved palaeobottom surfaces with stromatoporoids are exposed in two Devonian localities in the Holy Cross Mountains in central Poland: Skały and Bolechowice-Panek quarries. The stromatoporoids were subjected to morphometric analysis and distribution studies. Stromatoporoids were studied hitherto only in vertical cross sections; the study of three-dimensional stromatoporoid domes has created a need to introduce a new set of parameters describing their shapes, which includes: horizontal length and width, vertical height, elongation ratio and elongation azimuth. In order to make the measurements made by various methods comparable, and thus to allow comparable interpretations, recalculation formulas have been presented. Comparison of the results obtained by the two methods indicates that the measurements made in vertical cross sections substantially bias the dimensions and shapes of the stromatoporoids, which may influence stromatoporoid-based palaeoenvironmental reconstructions. The results of the measurements were interpreted in terms of palaeonvironmental conditions. In Bolechowice-Panek the stromatoporoids lived in a quiet shallow water setting with a low and stable sedimentation rate. In Skały the stromatoporoids grew in a shallow subtidal setting and located themselves on parallel ripples, most probably to escape being buried by deposits accumulating in inter-ripple depressions.
EN
A survey of the principal benthic faunas from the Devonian of the Ardennes is presented. The [alfa] diversity is very high (707 species, including 138 species of stromatoporoids, 113 species of tabulates, hydroids and chaetetids, and 456 species of brachiopods). Analysis of their distribution through time indicates two brachiopod diversity peaks (Emsian/Eifelian and Frasnian), a single stromatoporoid diversity peak (Givetian), and no clear peak of tabulate corals (with the highest diversification during the Eifelian.Frasnian). The highest diversity of bioconstructors in the Givetian correlates with a decrease in brachiopod diversity. Changes in the vertical distribution of the faunas are correlated with the facies development: the development of carbonates correlates with the abundance of stromatoporoids and tabulates, while brachiopods were most abundant before and after the peak of carbonate development. Bioconstructors are absent (or nearly absent) in siliciclastic facies.
EN
Stromatoporoid skeletons from polished slabs of stromatoporoid- and coral-bearing limestones of the Upper Devonian Kowala Formation from the Holy Cross Mountains in Central Poland have been measured using a classic parameterization method, introduced by KERSHAW & RIDING (1978) and improved by KERSHAW (1984, 1998). The stromatoporoid shape appeared to be strongly dependent on its size - the V/B ratio decreases along with increasing B. The relation can be well matched by a curve described by a formula: f(x) = 5.7103x^0.81633. The size of the measured specimens must therefore be taken into account in those studies of the stromatoporoid morphology, where it is concerned a palaeoenvironmental indicator. The stromatoporoids adopted several types of initial surfaces, corresponding to various growth strategies in the first phase of their growth in response to various environmental conditions, such as substrate consistency and sedimentation rate. Latilaminae arrangement well records the stromatoporoid growth history and therefore its studies are crucial in environmental interpretations, as the conclusions inferred from the shape alone might be very misleading.
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