1,354,432 research outputs found
Taphonomy and ichnofabric of the trace fossil Avetoichnus luisae Uchman & Rattazzi, 2011 in Paleogene deep-sea fine-grained turbidites: examples from Italy, Poland and Spain.
No full textThe poorly known, helical spiral trace fossil Avetoichnus luisae Uchman & Rattazzi, 2011 has been investigated in fine-grained Paleogene turbidites in Italy, Poland and Spain. It shows a typical stratinomic preservation as endichnia and was developed in turbiditic mud and bioclastic deposits occupying the upper intervals (typically E3-F) of turbidite sequences. Other ichnotaxa occur in deeper levels (e.g., Alcyonidiopsis and Zoophycos in the Trasimeno area), while tree-like forms (e.g., Chondrites intricatus, C. targionii and Cladichnus in the same area), string-like forms (e.g., Planolites or Palaeophycus) and other undetermined burrows are usually found in shallower levels. The distribution of the ichnotaxa indicates an upwards increasing ichnodensity towards the higher intervals in many mud-bioclastic turbidite sequences. Detailed taphonomic analysis of 104 specimens of frequently branched Avetoichnus luisae has shown that a high degree of variation can be observed in their length, general shape, maximum diameter, maximum width of dots, shape of dots, dot distribution, spiral arrangement, central part (axis) and raised edges. These variations suggest that an unknown organism adjusted its activity (agrichnial or fodinichnial) using different strategies in accordance with changes in the turbiditic environment
Probable root structures and associated trace fossils from the Lower Pleistocene calcarenites of Favignana Island, southern Italy : dilemmas of interpretation
No full textTwo types of large, branched structures from the Lower Pleistocene (Calabrian) high-energy calcarenites of Favignana Island are described: Faviradixus robustus gen. et sp. nov. and Egadiradixus rectibrachiatus gen. et sp. nov. They may be interpreted as root structures of large plants, trees and trees or shrubs, respectively. The former taxon co-occurs with the marine animal trace fossils Ophiomorpha nodosa, Ophiomorpha isp., Thalassinoides isp. and Beaconites isp. The interpretation as root structures although tentative is probable and can be related to short emergence episodes for the formation of E. rectibrachiatus or to longer emergence, responsible for the discontinuity at the base of the overlying Tyrrhenian deposits, for F. robustus. Calcified root mats of smaller plants associated with the Tyrrhenian or younger emergence surfaces are common
Oligocene trace fossils from temporary fluvial plain ponds: An example from the Freshwater Molasse of Switzerland
No full textKonjugáty klastrů bóru jako stavební bloky pro přípravu polymerních nanostruktur
No full textCharles University in Prague Faculty of Science Department of Physical and Macromolecular Chemistry Author: Bc. Filip Steiner Supervisor: prof. RNDr. Pavel Matějíček, Ph.D. Advisor: Ing. Mariusz Uchman, Ph.D. Title: Boron Cluster Conjugates as Building Blocks for the Preparation of Polymeric Nanostructures Abstract This diploma thesis investigates the synthesis and supramolecular behaviour of amphiphilic conjugates of closo-dodecaborate dianion, [B12H12]2- , with polycationic diblock copolymer poly(ethylene oxide)-block-poly(2-(N, N, N', N'-tetramethyl guanidium ethyl acrylate), PEOn-b-PGEAm. The boron cluster dumbbells were synthesised by the exoskeletal, electrophile-induced nucleophilic substitution (EINS) and by subsequently ring-opening reaction with various aliphatic diols, resulting in a hybrid dumbbell molecule. These molecules were used for preparation of nanoparticles by co- assembly with polycationic diblock copolymer in water. Resulted nanostructures were characterised by static and dynamic light scattering and NMR spectroscopy. Keywords: boron cluster compounds, polymeric nanoparticles, co-assembly, NMR, light scatteringUniverzita Karlova v Praze Přírodovědecká fakulta Katedra fyzikální a makromolekulární chemie Autor: Bc. Filip Steiner Vedoucí práce: prof. RNDr. Pavel Matějíček, Ph.D. Konzultant: Ing. Mariusz Uchman, Ph.D. Název diplomové práce: Konjugáty klastrů bóru jako stavební bloky pro přípravu polymerních nanostruktur Abstrakt Tato diplomová práce se zabývá syntézou a supramolekulárním chováním amfifilních konjugátů closo-dodekaborátového dianiontu, [B12H12]2- , s polykationtovým diblokovým kopolymerem poly(ethylen oxid)-b-poly(2-(N, N, N', N'-tetramethylguanidium ethylakrylát), PEOn-b-PGEAm. Konjugáty klastrů bóru byly syntetizovány pomocí exoskeletální, elektrofilem indukované nukleofilní substituce (EINS) a následnou reakcí s různými alifatickými dioly, což vedlo ke vzniku amfifilních molekul činkovitého tvaru. Ty byly následně využity k přípravě nanočástic spoluskládáním s polykationtovými blokovými kopolymery ve vodě. Výsledné nanostruktury byly charakterizovány pomocí statického a dynamického rozptylu světla a spektroskopie NMR. Klíčová slova: klastrové sloučeniny bóru, polymerní nanočástice, spoluskládání, NMR, rozptyl světlaKatedra fyzikální a makromol. chemieDepartment of Physical and Macromolecular ChemistryFaculty of SciencePřírodovědecká fakult
Taphonomy and ichnofabric of the trace fossil Avetoichnus luisae Uchman & Rattazzi, 2011 in Paleogene deep-sea fine-grained turbidites : examples from Italy, Poland and Spain
No full textThe poorly known, helical spiral trace fossil Avetoichnus luisae Uchman & Rattazzi, 2011 has been investigated in fine-grained Paleogene turbidites in Italy, Poland and Spain. It shows a typical stratinomic preservation as endichnia and was developed in turbiditic mud and bioclastic deposits occupying the upper intervals (typically E3-F) of turbidite sequences. Other ichnotaxa occur in deeper levels (e.g., Alcyonidiopsis and Zoophycos in the Trasimeno area), while tree-like forms (e.g., Chondrites intricatus, C. targionii and Cladichnus in the same area), string-like forms (e.g., Planolites or Palaeophycus) and other undetermined burrows are usually found in shallower levels. The distribution of the ichnotaxa indicates an upwards increasing ichnodensity towards the higher intervals in many mud-bioclastic turbidite sequences. Detailed taphonomic analysis of 104 specimens of frequently branched Avetoichnus luisae has shown that a high degree of variation can be observed in their length, general shape, maximum diameter, maximum width of dots, shape of dots, dot distribution, spiral arrangement, central part (axis) and raised edges. These variations suggest that an unknown organism adjusted its activity (agrichnial or fodinichnial) using different strategies in accordance with changes in the turbiditic environment
Fossilized bioelectric wire : the trace fossil Trichichnus
No full textThe trace fossil Trichichnus is proposed as an indicator of fossil bioelectric bacterial activity at the oxic–anoxic interface zone of marine sediments. This fulfils the idea that such processes, commonly found in the modern realm, should be also present in the geological past. Trichichnus is an exceptional trace fossil due to its very thin diameter (mostly less than 1 mm) and common pyritic filling. It is ubiquitous in some fine-grained sediments, where it has been interpreted as a burrow formed deeper than any other trace fossils, below the redox boundary. Trichichnus, formerly referred to as deeply burrowed invertebrates, has been found as remnant of a fossilized intrasediment bacterial mat that is pyritized. As visualized in 3-D by means of X-ray computed microtomography scanner, Trichichnus forms dense filamentous fabric, which reflects that it is produced by modern large, mat-forming, sulfide-oxidizing bacteria, belonging mostly to Thioploca-related taxa, which are able to house a complex bacterial consortium. Several stages of Trichichnus formation, including filamentous, bacterial mat and its pyritization, are proposed to explain an electron exchange between oxic and suboxic/anoxic layers in the sediment. Therefore, Trichichnus can be considered a fossilized "electric wire"
Environmental fluctuations during the latest Cenomanian (Bonarelli Level) in the Gubbio area (central Italy) based on an ichnofabric approach
No full textA bed by bed analysis of the Bonarelli Level (late Cenomanian) in the Bottaccione Gorge and the Contessa Valley (Gubbio, Italy, area) reveals ichnofabric variations that follow lithofacies changes. Ichnofabric analysis has been approached in ~60 samples for every section, using thin sections of rocks and wet cut surfaces for three-dimensional observations.The ichnofabric includes five ichnotaxa: Chondrites isp., Planolites isp., Thalassinoides isp.,Trichichnus linearis, and Zoophycos isp.; their abundance and preservation fluctuate with the substrate consistency, oxygen content, and productivity. The ichnotaxa are absent in many beds that show primary lamination and were deposited under true anoxic conditions, but it is surprising that they are present in many thin beds inside the Bonarelli interval (10 in Bottaccione and 14 in Contessa). In the underlying and overlying Scaglia Bianca (late Cenomanian) carbonate deposits, the presence of a totally bioturbated background, together with superimposed discrete trace fossils (the same ichnotaxa as in the Bonarelli Level), reveals the absence of anoxic conditions (except for cherty layers), but the presence of minor fluctuations between aerobic and slightly dysaerobic conditions is marked by changes in ichnotaxa abundance
The ichnocoenosis of the bottom nepheloid layer (BNL) deposits : a case study from the Scaglia Toscana Formation (Paleogene, central Italy)
No full textSome fine-grained sediments from the Eocene in age Scaglia Toscana Formation in the Northern Apennines (Trasimeno area), previously interpreted as mud-silt turbidites, have been reinterpreted herein as bottom nepheloid layers (BNL). They contain a rich ichnocoenosis dominated by endichnial forms, that formed progressively in line with the slow accumulation rate of mud transported by the oceanic thermohaline bottom currents. In a BNL idealized sequence, a slight upward increasing density of trace fossils, suggests some differences with typical muddy turbidites. Together with sedimentary structures, trace fossils form an ichno-sedimentary sequence through the bed, which is explained by a step by step colonization that accompanies deposition of the bottom nepheloid layer by continuous currents. It is possible that these ichnological features are recurrent and helpful in recognition of similar deposits within other geological contexts
Avetoichnus luisae ichnocoenosis in Paleogene bottom nepheloid layer deposits, Scaglia Toscana Formation, central Italy
No full textBottom nepheloid layers (BNL) are deep dense waters transporting suspended clay, silt or fine sand with organic matter particles in the central part of basins, with usual suspended sediment concentrations of 1 mg/l and lesser concentrations < 1 mg/l progressively towards the basin plain (Puig et al., 2013). BNL are very common in recent basin margins (e.g. the continental rise of French Mediterranean, North Atlantic), but poorly studied in the geological record. Some authors think that turbulent flow in BNL is more responsible for deposition of mud in flat basin plains than fine-grained turbidites (P. Pilgrim, personal communication 2010). The thickness of BNL deposits depends on bottom current velocity and the balance between gravitational settling of particles, basin plain morphology and turbulence of the current. Burrowing organisms intensively exploit the organic matter deposited in the sea floor by BNL; in Canadian Atlantic basin plain, the upper surface is extremely bioturbated with hundreds of burrow openings per m2 (Hunkins et al., 1969, figs 3, 4). In the Paleogene Scaglia Toscana Formation (central Italy; Trasimeno area, Montanare, M. Solare, M. Maggio, Fig. 1), grey to red mudstones occur in beds which are 40 to 60 cm thick (Fig. 2). They are much thicker than typical mud turbidites of overlying Macigno Formation (Amendola et al. 2015). A typical increasing upward density of trace fossils (Monaco et al., 2012) has been detected. In lower tiers dominate deep endichnia (Zoophycos, Taenidium, Planolites); in middle and shallow tiers dominate very common Avetoichnus luisae, Chondrites targionii, C. intricatus, and Cladichnus. Then, utilizing ichnocoenoses is possible differentiate turbulent flow deposits (see Shanmugam, 2002; turbidites versus BNL deposits), because currents caused variation in food resources and the presence or absence of nutrient-rich fine-grained substrates. Ichnocoenoses of BNL sediments are a new interesting topic of studies in deep-sea depositional systems, as a proxy to elucidate paleoenvironmental and ethological conditions that influenced distribution, concentration, burrow diameter, burrow depth, ichnodiversity and traces fossil assemblages
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