A Test of the Biogenicity Criteria Established for Microfossils and Stromatolites on Quaternary Tufa and Speleothem Materials Formed in the “Twilight Zone” at Caerwys, UK

Natural Resources Wales and Steven Griffiths are thanked for access to Caerwys quarry and permission to work on the site. Sebastiaan Edelman and Thomas Logeman assisted with fieldwork and provided some of the field photographs. Bouke Lacet (Sedimentology laboratory, VU University Amsterdam) prepared the thin-sections. Three anonymous reviewers helped to sharpen the manuscript, and Sherry Cady provided valuable editorial advice and assistance. A.T.B. was inspired by Martin Brasier. He dedicates this manuscript to his father’s memory.

A Test of the Biogenicity Criteria Established for Microfossils and Stromatolites on Quaternary Tufa and Speleothem Materials Formed in the “Twilight Zone” at Caerwys, UK

Natural Resources Wales and Steven Griffiths are thanked for access to Caerwys quarry and permission to work on the site. Sebastiaan Edelman and Thomas Logeman assisted with fieldwork and provided some of the field photographs. Bouke Lacet (Sedimentology laboratory, VU University Amsterdam) prepared the thin-sections. Three anonymous reviewers helped to sharpen the manuscript, and Sherry Cady provided valuable editorial advice and assistance. A.T.B. was inspired by Martin Brasier. He dedicates this manuscript to his father’s memory.

A Test of the Biogenicity Criteria Established for Microfossils and Stromatolites on Quaternary Tufa and Speleothem Materials Formed in the “Twilight Zone” at Caerwys, UK

Natural Resources Wales and Steven Griffiths are thanked for access to Caerwys quarry and permission to work on the site. Sebastiaan Edelman and Thomas Logeman assisted with fieldwork and provided some of the field photographs. Bouke Lacet (Sedimentology laboratory, VU University Amsterdam) prepared the thin-sections. Three anonymous reviewers helped to sharpen the manuscript, and Sherry Cady provided valuable editorial advice and assistance. A.T.B. was inspired by Martin Brasier. He dedicates this manuscript to his father’s memory.

Central Algarve karst system tufa-related dynamics, Portugal.

Geomorphological mapping is a powerful instrument improving the geomorphological interpretation and understanding of the processes and forms used in landscape studies, with the ability of organizing different thematic layers in the same map. The presented map provide relevant information about the different geomorphological units of the central Algarve (i.e. the Carboniferous flysch mountains; the Barrocal, with marly and karstified subunits), where a karst system is prominent. Solution karst morphologies and large dry areas are common in the elevated areas of the Barrocal, suggesting deep circulation of groundwater. These recharge areas feed the perched aquifers of the area, where discharge is controlled by the impervious lithologies (clay-rich strata of the turbidites, marls and argilites) in the valley bottoms or other leaks in dammed aquifers. In springs related to the main aquifers tufa are actively being formed and, close coupled to spring location, different tufa depositional systems develop.

Caracterização da geometria de depósitos sedimentares na borda sudoeste da Bacia`Potiguar

This study focuses on the potential of several techniques used to identify depositional geometries and paleogeographical investigation on the SW border of the Potiguar Basin. Three areas were selected for an integrated geological, geophysical and geochemistry study. The main used techniques were facies analysis, remote sensing,ground penetrating radar (GPR) and gamma-ray in outcrops, as well as petrographic microscope observations and the using of scanning eletronic microscopic (SEM), and Carbon and Oxygen Isotopic study in the carbonate tufa. These methodological approaches were very efficient in the facies analysis of 2D geometries. The GPR profiles carried out in Quixeré identified important geological reflectors which allowed to the identification of depositional geometries of tufa. However, GPR profiles were not able to identify geological reflectors in the Apodi and Olho d´Água da Bica outcrops. Gammaray profiles also presented good results, which justify their use in 1D and 2D geometric analysis. Carbon and Oxygen Isotopic analyses were also used to investigate paleoenvironmental setting of tufa deposits. It is important to remark the excellent resultsof GRP using in the identification of deposition al geometries of tufa and their contact relationships with the underlying rocks. Field analysis of faults indicate a vertical sigma-1 orientation which was associated to normal faults

Sand bioconsolidation through the precipitation of calcium carbonate by two ureolytic bacteria

Two ureolytic strains, B. sphaericus LMG 22257 and Bacillus sp (I-001), were tested for their ability to consolidate sand by submitting them to two days` treatment using 10(7) viable cell concentrations of inocula and medium precipitation with calcium ions. The results showed that B. sphaericus LMG 22257 induced greater calcium carbonate formation. Both strains produced calcite and were able to consolidate sand. Tensile strength of consolidated sand was not a function of the amount of precipitated CaCO(3) but a linear function of the ratio bioconsolidation index (BC) defined as the ratio of CaCO(3) volume to initial sand porosity. A simple model to estimate the engineering benefits of consolidation is proposed. (C) 2011 Elsevier B.V. All rights reserved.

Characterization and application of the solid waste generated in the production of calcium carbonate precipitate as a corrective for the soil acidity

The calcium carbonate industry generates solid waste products which, because of their high alkaline content (CaO, CaCO(3) and Ca (OH)(2)), have a substantial impact on the environment. The objectives of this study are to characterize and classify the solid waste products, which are generated during the hydration process of the calcium carbonate industry, according to ABNT`s NBR 10.000 series, and to determine the potential and efficiency of using these solid residues to correct soil acidity. Initially, the studied residue was submitted to gross mass, leaching, solubility, pH. X-ray Diffractometry, Inductive Coupled Plasma - Atomic Emission Spectrometry (ICP-AES), granularity and humidity analyses. The potential and efficiency of the residue for correcting soil acidity was determined by analysis of the quality attributes for soil correctives (PN, PRNT, Ca and Mg contents, granularity). Consequently, the results show that the studied residue may be used as a soil acidity corrective, considering that a typical corrective compound is recommended for each different type of soil. Additionally, the product must be further treated (dried and ground) to suit the specific requirements of the consumer market.

Soil carbon determination by high temperature combustion - A comparison with dichromate oxidation procedures and the influence of charcoal and carbonate carbon on the measured value

The measurement of organic carbon in soils has traditionally used dichromate oxidation procedures including the Wakley and Black and the Heanes methods. The measurement of carbon in soils by high temperature combustion is now widely used providing a rapid automated procedure without the use of toxic chemicals. This procedure however measures total carbon thus requiring some means of correction for soil samples containing carbonate and charcoal forms of carbon. This paper examines the effects of known additions of charcoal to a range of soil types on the results obtained by the Walkley and Black, Heanes and combustion methods. The results show, that while the charcoal carbon does not react under Walkley and Black conditions, some proportion does so with the Heanes method. A comparison of six Australian Soil and Plant Analysis Council reference soil samples by the three methods showed good agreement between the Heanes method, the combustion method and only slightly lower recoveries by the Walkley and Black procedure. Carbonate carbon will cause an overestimation of soil organic carbon by the combustion method thus requiring a separate determination of carbonate carbon to be applied as a correction. This work shows that a suitable acid pre-treatment of alkaline soils in the sample boats followed by a drying step eliminates the carbonate carbon prior to combustion and the need for an additional measurement. The measurement of carbon in soils by high temperature combustion in an oxygen atmosphere has been shown to be a rapid and reliable method capable of producing results in good agreement with one of the established dichromate oxidation procedures.

Petrographic and isotope constraints on the origin of authigenic carbonate minerals and the associated fluid evolution in Late Permian coal measures, Bowen Basin (Queensland), Australia

Authigenic carbonate minerals are ubiquitous throughout the Late Permian coal measures of the Bowen Basin, Queensland, Australia. In the northern Bowen Basin, carbonates include the following assemblages: siderite I (delta O-18(SMOW) = +11.4 to + 17%, delta C-13(PDB) = - 5.3 to + 120), Fe-Mg calcite-ankerite-siderite II mineral association (delta O-18(SMOW) = +7.2 to + 10.20, delta C-13(PDB) = 10.9 to - 1.80 for ankerite) and a later calcite (delta O-18(SMOW) = +5.9 to + 14.60, delta C-13(PDB) = -11.4 to + 4.40). In the southern Bowen Basin, the carbonate phase consists only of calcite (delta O-18(SMOW) = +12.5 to + 14.80, delta C-13(PDB) = -19.4 to + 0.80), where it occurs extensively throughout all stratigraphic levels. Siderite I occurs in mudrocks and sandstones and predates all other carbonate minerals. This carbonate phase is interpreted to have formed as an early diagenetic mineral from meteoric waters under cold climate and reducing conditions. Fe-Mg calcite-ankerite-siderite Il occur in sandstones as replacement of volcanic rock fragments. Clay minerals (illite-smectite, chlorite and kaolinite) postdate Ca-Fe-Mg carbonates, and precipitation of the later calcite is associated with clay mineral formation. The Ca-Fe-Mg carbonates and later calcite of the northern Bowen Basin are regarded as having formed as a result of hydrothermal activity during the latest Triassic extensional tectonic event which affected this part of the basin, rather than deep burial diagenesis during the Middle to Late Triassic as previously reported. This hypothesis is based on the timing relationships of the authigenic mineral phases and the low delta O-18 values of ankerite and calcite, together with radiometric dating of illitic clays and recently published regional geological evidence. Following the precipitation of the Ca-Fe-Mg carbonates from strongly O-18-depleted meteoric-hydrothermal fluids, continuing fluid circulation and water-rock interaction resulted in dissolution of these carbonate phases as well as labile fragments of volcaniclastic rocks. Subsequently, the later calcite and day minerals precipitated from relatively evolved (O-18-enriched) fluids. The nearly uniform delta O-18 values of the southern Bowen Basin calcite have been attributed to very low water/rock ratio in the system, where the fluid isotropic composition was buffered by the delta O-18 values of rocks. (C) 2000 Elsevier Science B.V. All rights reserved.

Calcium Carbonate Particle Growth Depending on Coupling among Adjacent Layers in Hybrid LB/LbL Films

There are practical and academic situations that justify the study of calcium carbonate crystallization and especially of systems that are associated with organic matrices and a confined medium. Despite the fact that many different matrices have been studied, the use of well-behaved, thin organic films may provide new knowledge about this system. In this work, we have studied the growth of calcium carbonate particles on well-defined organic matrices that were formed by layer-by-layer (LbL) polyelectrolyte films deposited on phospholipid Langmuir-Blodgett films (LB). We were able to change the surface electrical charge density of the LB films by changing the proportions of a negatively charged lipid, the sodium salt of dimyristoyl-sn-glycero-phosphatidyl acid (DMPA), and a zwitterionic lipid. dimyristoyl-sn-glycero-phosphatidylethanolamine (DMPE). This affects the subsequent polyelectrolyte LbL film deposition, which also changes the the nature of the bonding (electrostatic interaction or hydrogen bonding). This approach allowed for the formation of calcium carbonate particles of different final shapes, roughnesses, and sizes. The masses of deposited lipids, polyelectrolytes, and calcium cabonate were quantified by the quartz crystal microbalance technique. The structures of obtained particles were analyzed by scanning electron microscopy.

Surface modification of metals by calcium carbonate thin films on a layer-by-layer polyelectrolyte matrix

A multilayer organic film containing poly(acrylic acid) and chitosan was fabricated on a metallic support by means of the layer-by-layer technique. This film was used as a template for calcium carbonate crystallization and presents two possible binding sites where the nucleation may be initiated, either calcium ions acting as counterions of the polyelectrolyte or those trapped in the template gel network formed by the polyelectrolyte chains. Calcium carbonate formation was carried out by carbon dioxide diffusion, where CO, was generated from ammonium carbonate decomposition. The CaCO3 nanocrystals obtained, formed a dense, homogeneous, and continuous film. Vaterite and calcite CaCO3 crystalline forms were detected. (c) 2007 Elsevier B.V All rights reserved.

Efficacy and Tolerability of Lodenafil Carbonate for Oral Therapy in Erectile Dysfunction: A Phase II Clinical Trial

Oral treatment with phosphodiesterase type 5 inhibitor (PDE5) is considered the first-line treatment for patients with erectile dysfunction (ED). Lodenafil carbonate (LC) is a novel PDE5. This is a phase II, prospective, randomized, double-blind, and placebo controlled clinical trial of LC. Efficacy end points were International Index of Sexual Function (IIEF) erectile domain, IIEF questions 3 and 4, and Sexual Encounter Profile (SEP) questions 2 and 3, before and after the use of LC or placebo. Seventy-two men older than 18 years, with ED for at least 6 months with stable sexual relationship were enrolled. Patients were randomized to placebo or LC 80 mg, 40 mg, or 20 mg and followed for 4 weeks. IIEF erectile domain scores before and after the use of medications were (mean +/- standard deviation [SD]): placebo: 11.9 +/- 3.4 and 12.6 +/- 5.5; LC 20 mg: 15.8 +/- 4.1 and 18.9 +/- 6.6; LC 40 mg: 11.9 +/- 4.4 and 15.4 +/- 8.1; LC 80 mg: 14.2 +/- 4.7 and 22.8 +/- 6.0 (anova P < 0.01). The SEP-2 scores before and after the use of medications were (Mean +/- SD): placebo: 71.0 +/- 33.1 and 51.2 +/- 43.1; LC 20 mg 70.3 +/- 34.2 and 75.5 +/- 31.5; LC 40 mg: 48.4 +/- 42.1 and 60.8 +/- 42.5; LC 80 mg: 68.6 +/- 33.5 and 89.6 +/- 26.0. The SEP-3 scores were: placebo 23.3 +/- 27.6 and 33.6 +/- 42.3; LC 20 mg: 32.3 +/- 38.9 and 51.2 +/- 41.7; LC 40 mg: 39.7 +/- 44.7 and 46.7 +/- 41.1; LC 80 mg* 17.2 +/- 29.5 and 74.3 +/- 36.4 (*P < 0.05 for difference to placebo). The drug was well tolerated. Adverse reactions were mild and self-limited and included headache, rhinitis, flushing, color visual disorders, and dyspepsia. This study showed that the dosage of 80 mg of LC was significantly more efficacious than placebo and well tolerated. Glina S, Toscano I, Gomatzky C, de Goes PM, Junior AN, de Almeida Claro JF, and Pagani E. Efficacy and tolerability of lodenafil carbonate for oral therapy in erectile dysfunction: A phase II clinical trial. J Sex Med 2009;6:553-557.

The geochemistry of late Archaean microbial carbonate: Implications for ocean chemistry and continental erosion history

Trace element concentrations and combined Sr- and Nd-isotope compositions were determined on stromatolitic carbonates (microbialites) from the 2.52 Ga Campbellrand carbonate platform (South Africa). Shale-normalised rare earth element and yttrium patterns of the ancient samples are similar to those of modern seawater in having positive La and Y anomalies and in being depleted in light rare earth elements. In contrast to modem seawater (and microbialite proxies), the 2.52 Ga samples lack a negative Ce anomaly but possess a positive Eu anomaly. These latter trace element characteristics are interpreted to reflect anoxic deep ocean waters where, unlike today, hydrothermal Fe input was not oxidised, and scavenged and rare earth elements were not coprecipitated with Fe-oxyhydroxides. The persistence of a positive Eu anomaly in relatively shallow Campbellrand platform waters indicates a dramatic reversal from hydrothermally dominated (Archaean) to continental erosion-dominated (Phanerozoic) rare earth element flux ratio. The dominant hydrothermal input is also expressed in the initial Sr- and Nd-isotope ratios. There is collinear variation in Sr-Nd systematics, which range from primitive values (Sr-87/Sr-86 of 0.702386 and epsilon (Nd) of +2.1) to more evolved crustal ratios. Mixing calculations show that the range in trace element ratios (e.g., Y/Ho) and initial isotope ratios is not a result of contamination by trapped sediment, but that the chemical band isotopic variation reflects carbonate deposition in an environment where different water masses mixed. Calculated Nd flux ratios yield a hydrothermal input into the 2.52 Ga oceans one order of magnitude larger than continental input. Such a change in flux ratio most likely required substantially reduced continental inputs, which could, in turn, reflect a plate tectonic causation (e.g., reduced topography or expansion of epicontinental seas). Copyright (C) 2001 Elsevier Science Ltd.

A mechanistic model for carbon dioxide corrosion of mild steel in the presence of protective iron carbonate films - Part 3: Film growth model

A model of iron carbonate (FeCO3) film growth is proposed, which is an extension of the recent mechanistic model of carbon dioxide (CO2) corrosion by Nesic, et al. In the present model, the film growth occurs by precipitation of iron carbonate once saturation is exceeded. The kinetics of precipitation is dependent on temperature and local species concentrations that are calculated by solving the coupled species transport equations. Precipitation tends to build up a layer of FeCO3 on the surface of the steel and reduce the corrosion rate. On the other hand, the corrosion process induces voids under the precipitated film, thus increasing the porosity and leading to a higher corrosion rate. Depending on the environmental parameters such as temperature, pH, CO2 partial pressure, velocity, etc., the balance of the two processes can lead to a variety of outcomes. Very protective films and low corrosion rates are predicted at high pH, temperature, CO2 partial pressure, and Fe2+ ion concentration due to formation of dense protective films as expected. The model has been successfully calibrated against limited experimental data. Parametric testing of the model has been done to gain insight into the effect of various environmental parameters on iron carbonate film formation. The trends shown in the predictions agreed well with the general understanding of the CO2 corrosion process in the presence of iron carbonate films. The present model confirms that the concept of scaling tendency is a good tool for predicting the likelihood of protective iron carbonate film formation.

Microfacies studies of carbonate rocks from Jurassic outcrops in the north of Faro, Southern Portugal

The Middle and Upper Jurassique limestones investigated were sub-divided into nine microfacies (MF) types. The firsts four represent Bathonian sediments with shallow water characteristics typical for carbonate platforms. They are comparable with Wilson's facies zones 6 to 8. Reef and reef debris, near-shore clastic-dominated limestones are not present. These MF-types are reiterated several times without cyclicity. The vertical development of the differentiated facies units indicates a close interfingering. The microfacies data are typical of inter to shallow subtidal environments; both authigenous quartz and low faunal and floral diversity of several layers point to temporary restricted conditions. The occurrence of Dictyoconus cayeuxi LUCAS and Callovian ammonites from the above lying strata argue for a Bathonian age. The MF-types 5-9 (Oxfordian-Kimmeridgian) show completely different sedimentation conditions. Fully marine nearshore recifal limestones alternate with pelagic sediments formed at deeper shelf areas. The pelagic micritic limestones of Oxfordian age are characterized by allodapic intercalations whereas the Oxfordian/Kimmeridgian limestones with tuberolithic fabrics often show intensive silifications. Only initial patch reef growth-stages were reached during the development of the Oxfordian and Kimmeridgian shallow water limestones.