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Marine carbonates record geochemical information on the state of Earth's surface environment in the geological past, but recrystallization during burial can make the records difficult to interpret. Here, we report shore to basin gradients in δ44Ca values in matrix limestone and burrow dolomite across a sequence of Late Ordovician (Katian Stage) burrow-mottled carbonates in the Williston Basin, an intracratonic epeiric marine basin in North America. Both gradients are interpreted to have diagenetic origins. The gradient in limestone δ44Ca values developed in a bathymetrically controlled sediment- to fluid-buffered diagenetic system operating between the center and the edges of the basin. Two dolomitizing events formed the gradient in dolomite δ44Ca values. The sediment-buffered end of the limestone gradient preserves the δ44Ca value of the original carbonate mud (∼–1.28 ± 0.10 ‰). The fluid-buffered end of the gradient conserves the δ44Ca value of contemporaneous seawater (–0.47 ± 0.10 ‰), because: (1) pore water exchange drivers operated with greater variety and intensity in shallow water settings, (2) shallow nearshore deposits exchanged more Ca with seawater during recrystallization to diagenetic calcite than deeper offshore deposits, and (3) diagenetic calcite formed with negligible fractionation under equilibrium conditions. The gradient conserves the local value of Δ sed (–0.81 ± 0.20 ‰) despite its diagenetic origin, and the magnitude of Δ sed is consistent with primary calcite precipitation in a 'calcite sea'. Field assessment of the equilibrium Ca isotope fractionation factor between calcite and dolomite of –0.41 ± 0.17 ‰ at ambient temperature is applied to correct basin-centered dolomite for fractionation, yielding –1.62 ± 0.27 ‰, which is very different from the –0.25 ± 0.07 ‰ value of Ca in evaporatively concentrated seawater from which the dolomite originally formed. Applying the same fractionation factor to correct literature data on early diagenetic dolomite in the Great Basin, North America, yields –0.69 ± 0.22 ‰ for the δ44Ca value of seawater, which is ∼0.2 ‰ lower than 'normal marine' waters in stratigraphically equivalent deposits in the Willison Basin, and 0.44 ‰ lower than evaporatively concentrated seawater during a brief period of basin restriction and anhydrite deposition. The nearly 0.5 ‰ variation in the δ44Ca value of Katian seawater falls within the range of scatter in the brachiopod reconstruction of seawater Ca isotopes. Here, we propose that the true ocean record of secular change lies towards the bottom of the range of scatter, and that the higher values in the record reflect local Ca cycling and circulation restriction in epeiric seas. Epeiric seas cultivate the fluid-buffered diagenetic conditions required to promote Ca isotope exchange between reactive carbonate sediments and seawater through carbonate mineral dissolution/recrystallization, crystal coarsening by way of Ostwald ripening, and replacive dolomitization. It is not the apportioning of kinetically fractionated aragonite and calcite in the carbonate deposition flux that drove secular changes in global value of Δ sed between 'calcite' and 'aragonite' seas, but rather the replacement of kinetic fractionations with equilibrium fractionations during fluid-buffered diagenesis with seawater. [ABSTRACT FROM AUTHOR]

The analysis of the thermal damages in Notre-Dame de Paris is necessary to estimate the impact of the dramatic 2019 fire on the remaining structure prior to reconstruction. In doing so, the large amount of data being generated creates a benchmark environment to test the relevance of numerical fire models in the unconventional configuration of a medieval roof. While being an uncontrolled and complex configuration, it can provide insights regarding the relevance of numerical tools for fire risk assessment in historic buildings. Analysing the thermal degradation of the Lutetian limestone in a vault of the choir, experimental techniques are developed to track the in-depth maximum temperature profile reached during the fire. Numerical simulations of the fire development in the roof space then aim at replicating the observations through the evaluation of the heat flux impinging the vaults during the fire. These simulations are carried out using Fire Dynamic Simulator, which requires a large range of assumptions prior to any simulation regarding materials, geometry, meshing and scale. These assumptions are described and pave the way to a future sensitivity analysis to confront the upcoming outcomes of the simulations with the experimental observations. [ABSTRACT FROM AUTHOR]

The main objective of this study is to investigate surface adsorption characteristics and physical conditions of laterite for the removal of nitrate in aqueous solutions with the appropriate amendment for the effective removal of nitrate from drinking water. The physico-chemical properties of laterite soil were analyzed. The effects of various operational parameters such as solution pH, adsorbent dosage, contact time, and the initial concentration of nitrate were examined on nitrate adsorption by laterite and laterite-limestone soil mixtures using the batch experiments. The obtained results showed that the maximum percentage of nitrate adsorption attained by raw laterite was at initial pH 3, after 60 min of contact time, and with an adsorbent dose of 2 g. Pseudo-first-order kinetic model and Langmuir isotherm model showed the best fit for the experimental adsorption data, and a maximum adsorption capacity of 0.628 mg/g was observed. Laterite-limestone mixture containing 60% laterite showed the highest removal efficiency. The results obtained by the limestone-laterite mixture showed that the maximum removal efficiency attained was at pH 3, after 180 min of contact time, and with an adsorbent dose of 2 g. Although the optimum pH was similar in both soil samples, the final pH of the solution had increased to 6.75 ± 0.17. Pseudo-second-order kinetic model and Freundlich isotherm model showed the best fit for the experimental adsorption data. This soil mixture was used to determine the effect of competing anions on the nitrate removal efficiency. It was found that phosphate ions have shown maximum influence. [ABSTRACT FROM AUTHOR]

This study focuses on the wettability alteration (changing from a hydrophobic state to a hydrophilic state) of Indiana limestone for hydrogen (H 2) geological storage. We examine the effect of hexanoic acid C 6 , lauric acid C 12 , and stearic acid C 18 , on the wettability of Indiana limestone at ambient (298 K and 0.1 MPa) and reservoir (323 K and 8.27 MPa) conditions. The effects of silica nanofluids (silica with deionized water) at various concentrations (0.1 wt%, 0.25 wt%, and 0.5 wt%) on the wettability reversal of stearic-aged samples were tested at ambient and reservoir conditions. The results revealed increased H 2 -wetness (hydrophobicity) of the rock exposed to these organic acids in reservoir conditions. However, this hydrophobicity significantly decreased with the nanofluid treatment of the stearic-aged samples. This wettability reversal may increase the H 2 storage capacity and containment security and lead to successful large-scale geological storage operations if H 2 residual trapping is minimized. • Hydrophobicity of the rock increased by exposing to organic acids. • Hydrophobicity of the stearic-aged samples decreased by treating with nanofluid. • The wettability reversal may increase the H 2 storage capacity and H 2 residual trapping. [ABSTRACT FROM AUTHOR]

The systematics of the coral assemblages of the Vršatec Limestone from the Pieniny Klippen Belt (Western Carpathians) that inhabited the NW Tethyan margin during the Bajocian is revisited here based on a new and extensive sampling of coral specimens collected at four outcrops. The assemblage consists of 12 genera and 13 species, including the new species Proaplophyllia slovakensis and the first Bajocian occurrence of the genus Enallhelia. Morphometric analyses also allow us to synonymize multiple species citations of the genus Thecosmilia into a single species. A quantitative study shows that five genera tend to be most common at all outcrops, namely Cladophyllia , Dendraraea , Isastrea , Periseris , and Thecosmilia , documenting relatively high homogeneity in the qualitative generic composition of coral assemblages but quantitative differences among the four outcrops. Coral specimens are frequently affected by macroborings (Gastrochaenolites , Entobia , and Trypanites) and coated by microbialitic components. We suggest that these reefs grew in the optimum of the Bajocian reefal window (i.e., shallow-water photic environments above storm wave base). We also identify three traps (typological, nominal, and induction traps) that led in the past to the false stratigraphic attribution of these reefs, when they were erroneously assigned to the Oxfordian rather than to the Bajocian. [ABSTRACT FROM AUTHOR]

Stone consolidation is one of the most important and complex treatment actions performed in museums. However, products routinely applied on limestone objects are often chemically incompatible with the treated substrate. Despites the established efficiency of nanolime for outdoor conservation and its chemical compatibility with the carbonate mineral matrix, its performance in a museum context needs to be verified. As a result, this work addresses a shortcoming in the field of Stone Conservation as nanolime has never been officially introduced in museums before. Three British Museum limestone objects affected by superficial damages were treated using an Enhanced Nanolime Consolidation Technique (En−NCT) which was developed in the Materials Engineering Research Institute (Sheffield Hallam University) and tested for the first time in a museum context. The results show that the use of alcoholic nanolime by means of a tailored consolidation technique is a realistic and promising museum conservation approach. The En−NCT does not impair the aesthetical appearance of the objects and restores the mineral cohesion of the treated surface by increasing the hardness of the near-to-surface layers. [Display omitted] [ABSTRACT FROM AUTHOR]

In windy conditions, dry bulk material storage sites for limestone fugitively emit dust, causing occupational hazards and posing harmful health effects to nearby residents. According to this investigation, the threshold friction velocity for the limestone was 7 m s−1. As wind speed increases from 7 to 10 m s−1, the concentrations of TSP, PM 10 , and PM 2.5 rose by 148%, 121%, and 76%, respectively. Separate tests were conducted to evaluate fog cannons' and heavy-duty sprinklers' ability to capture TSP, PM 10 , and PM 2.5 and prevent re-suspension from the pile's surface. Eight cases of parameter combinations were investigated, where PM 2.5 had the lowest dust capture efficiencies in six instances, while TSP had the highest dust capture in all eight cases. Low spray angles and intermittent water flow regimes showed the best dust collection efficiency. For the fog cannon it was 85.3% and for the heavy-duty sprinkler, it was 79.5%, and they occurred at low and high wind velocities, respectively. The wettability of dust particles smaller than 4 µm in diameter was more difficult than that of larger particles, because the size differences between dust particles and wetting agent's droplets reduces the probability of collision. An artificial neural network was applied to predict dust capture efficiencies from model parameters such as wind speed, spray angle, and water supply regimes. The relative errors in the predicted capture efficiencies for TSP, PM 10 , and PM 2.5 capture were 1.86–4.73%, 2.15–4.57%, and 1.99–6.53%, respectively, implying a good learning ability of the neural network. The results of different wind speed predictions were verified by the F test, where the P values for TSP, PM 10 , and PM 2.5 ranged between 0.17–0.44, 0.18–0.45, and 0.16–0.48, respectively. Overall, intermittent waterflows and low wind speeds optimized the spread of the mist released from the fog cannon, while intermittent waterflows and higher wind speeds were necessary for the optimal performance of the heavy-duty sprinkler. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic atomization (EHDA) of limestone slurry is anticipated to significantly enhance desulfurization efficiency and reduce desulfurization wastewater discharge. In this study, a visual electrospray experimental system is established to obtain the characteristics of EHDA. Initially, the breakup modes of the slurry are investigated, identifying three distinct modes: dripping mode, microdripping mode, and oscillating microdripping mode. The electric field shortens the liquid thread, reducing secondary droplet formation in the oscillating microdripping mode. Furthermore, it is found that a slight increase in droplet size and an initial decrease followed by stabilization in generation frequency with voltage increasing in the oscillating microdripping mode. In addition, the nondimensionalized droplet size prediction formulas for each breakup mode are provided. Subsequent desulfurization characteristic experiments in an absorption tower reveal optimal desulfurization efficiency in the oscillating microdripping mode. The relationship between desulfurization efficiency and droplet size is discussed, highlighting the pivotal role of the gas-liquid contact area in determining desulfurization efficiency. The present work is expected to provide theoretical guidance for efficient desulfurization. [Display omitted] • The EDHA characteristics of limestone slurry are investigated. • The effect of particles on the EDHA behavior of meniscus is discussed. • The droplet diameter reaches the minimum in oscillating microdripping mode. • Increasing gas-liquid contact areas with electric field promotes absorption rate. [ABSTRACT FROM AUTHOR]

A Cambrian sedimentary sequence with a predominant lithology of limestone, sandy limestone, and quartzite pertaining to the Bolsa and Abrigo formations is exposed in the Sierra Los Ajos to the east of Cananea city (northeastern Sonora, Mexico). Two fossil assemblages from Guzhangian layers of the Abrigo Formation are described herein. The trilobites identified comprise Tricrepicephalus texanus (Shumard), Crepicephalus sp., Coosia ariston (Walcott), Coosia sp., Cedaria cf. eurycheilos Palmer, Coosella sp., Llanoaspis modesta Lochman, and Llanoaspis ? sp., representing the Cedaria and Crepicephalus zones (Miaolingian, Guzhangian). The Cambrian rocks of northeastern Sonora (Sierra Los Ajos, El Tule, and Mesteñas hills), southern Arizona, and Texas, were deposited as part of a thick sedimentary sequence on the southwestern margin of Laurentia, associated with an inner shelf marine environment. The distribution of the trilobites identified confirms the existence of a widespread Cambrian faunal province that includes the southeastern United States of America and northwestern Mexico. • Cambrian (Guzhangian) trilobites are described from Mexico. • The faunal association comprises the Cedaria and Crepicephalus zones. • The sequence was deposited on the southwestern margin of Laurentia. • The sediments were deposited in an inner shelf marine environment. [ABSTRACT FROM AUTHOR]

The central region of Sonora state, Mexico, is recognized by its different upper Paleozoic outcrops, highlighting the La Cueva Limestone and Mina México Formation. The rocks of Cerro Las Rastras and Sierra Martínez are considered among the most important Permian localities in central Sonora. This work studies the fusulinid faunas in two different sections, focusing on their biostratigraphical and paleoenvironmental relevance. Both sections comprise strata from the La Cueva Limestone and Mina México Formation. The fusulinids identified are Parafusulina sp., Paraskinnerella cf. skinneri , Praeskinnerella crassitectoria , Skinnerella cobachiensis , Skinnerella imlayi , and Eoparafusulina cf. linearis. The presence of Pa. cf. skinneri , Pr. crassitectoria , S. cobachiensis and S. imlayi indicates a lower–middle Leonardian (=upper Artinskian–lower Kungurian) age for the Las Rastras Section. The occurrence of E. cf. linearis in the base of the Sierra Martínez 2 Section suggests a youngest age of upper Wolfcampian for the bearing rocks. The microfacies analysis allowed the identification of six facies associations in the Las Rastras Section related to deep shelf, slope, and ramp-margin sand shoals. While three associations were identified in the Sierra Martínez 2 Section, indicating the deposition of open marine and slope environments. Fusulinids from both sections are classified as allochthonous elements in most facies associations (except those of open waters) since they are found in environments that are known to not been inhabited by these foraminifera. The fusulinids identified have a paleobiogeographic affinity with coeval assemblages from the North American Province. • Six species of fusulinids from Cerro Las Rastras and Sierra Martínez of Sonora, Mexico, are described. • Fusulinids belong to La Cueva Limestone and the Mina México Formation outcrops. • Fusulinids allow establishing a middle Wolfcampian–early Leonardian age for the sections studied. • The microfacies suggest the paleoenvironment varying from shallow to deep water. • The fusulinids identified can be correlated with the coeval fusulinids from the North American Province. [ABSTRACT FROM AUTHOR]

Mixtures of powders of waste glass (WG), limestone (LS), Na 2 CO 3 and CaO were used to formulate novel one-part in situ alkali-activated cement (WG-AAC). The in-situ interaction Na 2 CO 3 -CaO-H 2 O promoted the formation of CaCO 3 and NaOH, which promoted the WG and LS dissolution and influenced the micro- and molecular features of the resulting cementitious products. Pastes and mortars developed 1-year strengths of up to 29 MPa and were stable underwater. Characterization by XRD, SEM, EDS, and 29 Si -NMR indicated that a Na 2 CO 3 :CaO ratio close to 1:1 resulted in polymerized C-S-H, CaCO 3 , silica gel, and Ca-modified silica gel, which were intimately intermixed and possibly crosslinked through Q3 bonds. Such phases interacted synergistically improving the underwater stability of the WG-AAC, indicating that in-situ caustification is a suitable and practical alkaline activation for SiO 2 -rich precursors. • One-part activation of waste glass produced mortars with up to 29 MPa and stable underwater. • Caustification reactions positively influenced the micro and molecular features of the matrix. • Ca-modified silica gel, CaCO 3 , C-S-H and silica gel coexisted synergistically. [ABSTRACT FROM AUTHOR]

Three experiments were conducted to determine effect of feeding 5 commercial limestones varying in solubility (88–97%), mean particle size (500–700 microns), and geographical origin on Ca bioavailability and digestibility in commercial broiler and crossbred chickens. In Experiment 1, both crossbred and commercial chickens were used to measure the effect of dietary Ca level on tibia bone ash to develop a slope-ratio Ca bioavailability assay. Chickens were fed diets that contained Ca levels ranging from 0.20% to 0.95% from 9 to 22 d-of-age. Regressions of bone ash (mg/tibia and %) on supplemental Ca intake yielded large linear responses in both types of chickens in Experiment 1. In Experiment 2, relative bioavailability of Ca in 5 limestones using bone ash as primary response criterion was determined. Thirteen diets were fed to commercial Ross 308 male broilers which were either a Ca-deficient diet (0.30% Ca) or that diet supplemented 0.15 or 0.30% Ca from either reagent grade calcium carbonate (RCaCO 3) or 1 of the 5 commercial limestones from 9 to 22 d-of-age. Bioavailability of Ca in limestones relative to RCaCO 3 was determined using multiple linear regression of bone ash (mg/tibia and %) on supplemental Ca intake, which yielded slope-ratio relative Ca bioavailability values ranging from 90% to 106% in Experiment 2. In Experiment 3, apparent ileal digestibility (AID) and apparent total tract retention (TTR) of Ca in broiler chickens was measured for the 5 limestones using corn-based diets. The AID and TTR of Ca at 21 d-of-age were low and variable with a range of 20 to 34% for AID of Ca and 12 to 31% for TTR of Ca. Results from these studies indicate that a slope-ratio bone ash assay with either crossbred or modern commercial chickens can be used to measure relative bioavailability of Ca in limestones and there were few consistent differences in relative Ca bioavailability, AID of Ca, and TTR of Ca among 5 commercial limestones evaluated herein. [ABSTRACT FROM AUTHOR]

Dietary phytate P (PP) concentration impacts Ca and P digestibility in broilers. Research was conducted to determine the impact of increasing concentration of dietary PP, with and without phytase, on broiler standardized ileal digestibility (SID) of Ca and P. Digestible (Dig) Ca and P were calculated by multiplying SID and the analyzed dietary Ca and P concentrations. The experiment was a factorial arrangement of 2 phytase (0 and 1,000 U/kg) and 4 PP (0.16, 0.23, 0.29, and 0.34%) concentrations. Treatments were fed for 36 h from 20 to 22 d of age (4 b/pen, n ≥ 7 replicate pens/treatment). Different ratios of corn and corn germ were used to achieve the desired PP concentrations. A limestone with 800 µm geometric mean diameter was used as the sole Ca source to achieve 0.7% Ca in the final diets (96% Ca from limestone). An additional diet was fed that was N, Ca- and P-free, for the determination of endogenous losses of each nutrient. Distal ileal digesta were pooled from all birds in a pen. There were no interactions between PP and phytase on SID Ca or Dig Ca from limestone. Irrespective of phytase inclusion, increasing PP from 0.16 to 0.34% decreased SID Ca from 53.8 to 38.1% (P < 0.05). The SID Ca averaged 41.5 and 51.4% in diets containing 0 and 1000 U phytase/kg, respectively, across all PP concentrations (P < 0.05). Interactions were seen between PP and phytase on SID and Dig P (P < 0.05) with SID P of 31.1, 24.0, 20.1, and 16.3% for broilers fed 0.16, 0.23, 0.29, and 0.34% PP diets without phytase, respectively. When phytase was included at 1000 U/kg, SID P was 89.9, 87.5, 73.9 and 60.4% for diets containing 0.16, 0.23, 0.29 and 0.34% PP, respectively (P < 0.05). Overall, phytase improved SID Ca and P independent of PP concentration. However, with increasing PP concentration, both SID Ca and P were negatively affected. [ABSTRACT FROM AUTHOR]

Carbon/Oxygen logging is an effective method to perform oil layer recognition and oil saturation calculation, which plays an important role in the evaluation of remaining oil after casing. At present, there are two main methods to calculate the ratio of carbon to oxygen (C/O). Compared with the energy window count method, the element yield method can avoid the influence of background count in the gamma spectrum and calculated carbon/oxygen value has the higher sensitivity and better accuracy, but it is still greatly affected by carbon and oxygen elements in the formation skeleton. Therefore, a new carbon/oxygen calculation method is proposed in this paper to overcome the influence of formation skeleton and improve the response sensitivity of Carbon/Oxygen logging. Based on Monte Carlo method, the inelastic gamma spectrum of pure sandstone and pure limestone skeletons are obtained. Based on spectrum analysis technology, the ratio relationship of carbon, oxygen yield and skeleton mark element (Si, Ca) yield in two skeletons are obtained. Using these ratio relationships, the carbon and oxygen yields from the sandstone and limestone reservoir skeletons are deducted from the total carbon and oxygen yield. A new carbon/oxygen parameter called the residual carbon/oxygen value (C/O) R is calculated to perform oil-water recognition and a set of oil saturation calculation model suitable for the residual carbon/oxygen value is proposed. The environment application of the residual carbon/oxygen value is also analyzed. The study shows that the residual carbon/oxygen value has higher sensitivity than original carbon/oxygen value in oil layer recognition and has a great accuracy in oil saturation calculation. In environment application aspect, the residual carbon/oxygen value is basically unaffected by formation water salinity and is affected by wellbore fluid and wellbore size obviously. This new carbon/oxygen value calculation method has an important significance to improve the application effect of Carbon/Oxygen logging. • A part carbon and oxygen yield of skeleton is deducted and the residual carbon/oxygen value is calculated. • The residual carbon/oxygen weakens the influence of skeleton carbon and oxygen and improves the recognition sensitivity. • A new oil saturation calculation model for the residual carbon/oxygen is established and gets good effects in simulated well. [ABSTRACT FROM AUTHOR]

This paper presents a feasibility study on the production of ternary blended cements with low-kaolinite calcined coal gangue (CCG) and limestone, considering kaolinite contents varying from 11.7 % to 40.6 % in coal gangue (CG). The ternary systems were designed with 15 %, 30 %, 45 % and 60 % by mass of cement replaced by CCG and limestone with a fixed mass ratio of 2:1. The fluidity and compressive strength of the mortars were measured, followed by the strength efficiency analysis combined with CO 2 emission. The potential hydration mechanism was revealed by analysing the hydration kinetics, hydrates and microstructural evolution of these ternary pastes. The results showed that it is possible to use low-kaolinite CCG and limestone to prepare ternary blended cements with adequate mechanical strength that can fulfill the 28-day strength requirement of 32.5 or 42.5 grade cement. In addition, Increasing the kaolinite content in CG can increase the substitution of cement up to 60 %. Microstructural studies indicated that the compressive strength of these ternary mortars at 3 and 7 days was mainly dominated by cement hydration and the pozzolanic reaction between CCG and portlandite (CH), respectively. The precipitation of carboaluminates from the synergy of CCG and limestone significantly reduced critical pore size and increased the volume fraction of fine capillary pores from 7 days, well supporting the strength development of the ternary mortar. The findings of this work underscores the potential of using low-kaolinite CCG as a supplementary cementitious material (SCM) to reduce carbon footprint in the field of construction, and also in contributing to a high-value green utilization of solid waste. • Good linear correlations are obtained between the strength of ternary mortars and the kaolinite content in CCG. • The pozzolanic reaction between CCG and portlandite supports the strength development of ternary mortars before 7 days. • The synergistic addition of CCG together with limestone enhances the precipitation of carboaluminates. • CCG20LS10 has a higher promising for engineering application with considering CO 2 emission and strength development. [ABSTRACT FROM AUTHOR]

The substitution of Portland cement clinker with a combination of calcium carbonate and calcined clay is a promising binder concept to lower the CO 2 footprint of the cement industry due to the synergetic effect of both materials which form carbo-aluminate hydrates. In this study, the reactivity of several calcined clays was tested using the R3 test and mortar strength testing in different combinations with calcium carbonate and Portland cement. A multiple regression analysis revealed that the reactivity in the R3 test depends mainly on the amorphous Al 2 O 3 and to a minor extent on the grain size and the MgO content. It was found that the most reactive calcined clay according to the R3 test led to no significant increase in compressive strength between 7 and 28 days. This clay also shows a slightly lower overall strength after 28 days than a calcined clay that was rated "medium reactive" according to the R3 test. The most reactive calcined clay was further investigated in a hydration study using X-ray diffraction. Based on this, a thermodynamic model was built and revealed that only a comparatively small percentage of the calcined clay reacted after 28 days. • Amorphous Al2O3 as most important factor for calcined clay reactivity using R3 test. • Low strength gain after 7 days using a highly reactive calcined clay. • Combining XRD with thermodynamic modeling. • Low reaction degree after 28 days of the highly reactive calcined clay. • Lower reactive calcined clays can outperform higher reactive ones. [ABSTRACT FROM AUTHOR]

In order to reveal the influence mechanism of limestone powder on the mechanical properties of concrete, the manufactured sand concrete with a water-cement ratio of 0.45 was taken as the research object. The effects of different limestone powder contents (0 %, 5 %, 10 %, 15 %, and 20 %) on the compressive strength of concrete were explored based on Griffith's microcracking theory. The nano-indentation, ultra-depth-of-field microscopy, LF NMR, and other methods were used for testing. The test results show that with the increase of limestone powder content, the elastic modulus of the Interfacial Transition Zone (ITZ) and the paste increases first and then decreases, the thickness of the ITZ decreases first and then increases, and the total porosity of the paste decreases first and then increases. The microstructure of the ITZ and the paste is the densest, corresponding to the maximum compressive strength of the concrete as the limestone content is 10 %. It is found that the thickness of ITZ can be regarded as the initial crack of concrete. The compressive strength of concrete calculated by Griffith's microcracking theory formula is the same as the measured value. The research results provide a theoretical reference for the influence mechanism of limestone powder on the mechanical properties of concrete. • The thickness of the interfacial transition zone of concrete was quantitatively characterized by nanoindentation technique. • The interfacial transition zone is regarded as the initial crack when the concrete is damaged. • The influence of limestone powder on the interfacial transition zone and mechanical properties of concrete was analyzed. • Based on Griffith's microcracking theory, the influence mechanism of limestone powder on the mechanical properties of concrete was explored. [ABSTRACT FROM AUTHOR]

To explore the potential of magnesite adopted as supplementary cementitious material (SCM) in cement industry, the authors of this paper investigated the hydration characteristics of ternary slag cement mixtures containing magnesite or limestone. All cement pastes were formulated with a water-to-binder ratio of 0.4, and a total of 50 % substitution level was applied across the blends, with varying slag and magnesite/limestone contents. Experimental results confirmed that adding limestone to slag cement can promote the hydration of cement clinker through the nucleation effect, while not for magnesite addition. As the substitution ratio of magnesite increased, there was a notable increase in both the critical pore diameter and cumulative pore volume, leading to a continuous decrease in the compressive strength of cement pastes. Compared to limestone-containing blends, the incorporation of magnesite was more beneficial to the compressive strength at 7 and 28 days. Additionally, limestone facilitated the precipitation of hemi- and mono-carboaluminate, whereas no hemicarbonate was observed in mixtures containing magnesite. The addition of magnesite promoted the formation of hydrotalcite-like phase, and the quantitative analysis revealed that the dissolution of magnesite primarily occurred in the first 7 days. The authors believed that the results obtained in this paper proposed new perspectives on utilizing magnesite as SCM in cement industry. • The hydration characteristics of cement-slag-magnesite ternary systems. • The differences with respect to hydration characteristics with magnesite or limestone addition. • The correlation of porosity and chemically bound water content vs. compressive strength of ternary pastes. [ABSTRACT FROM AUTHOR]

Carboniferous-Permian successions in the Amotape Mountains (NW Peru) are poorly dated due to the predominant siliciclastic intervals and the scarcity of fossils. The biostratigraphy of the formations is thus poorly constrained and, in general, limited to major systems or subsystems. The Cerro Prieto Formation was assigned to the Pennsylvanian or middle Pennsylvanian, but at the Caseta de la Antena section, the lower half of the formation contains carbonate horizons where diverse foraminiferal assemblages are recorded. Foraminifers allow to assign the base of the formation to the basal Bashkirian Stage, Morrowan Substage or Globivalvulina-Millerella Zone. This biostratigraphy can be extrapolated to the base of the Tarma Formation in central and south Peru, where this part of the latter formation remains undated. The upper limestone levels at Caseta de la Antena are assigned to the late Bashkirian, Atokan Substage or Eoschubertella-Pseudostaffella Zone. The upper half of the Cerro Prieto Formation, only composed of siliciclastics, might correspond to the uppermost late Bashkirian/lowermost Moscovian, or the mid-upper Atokan, due to fusulinids recorded at the top of the Tarma Formation. Foraminiferal assemblages are rather similar to those recorded from the lower part of the Copacabana Formation in Bolivia, although some differences occur, and apparently rather different from those in south Peru, a fact which suggests a slight biogeographic differentiation between the Amotape Mountains and the Central Andean Belt possibly related to its distinct geological setting. • Middle Carboniferous Foraminiferal assemblages from Peru are similar to those in Bolivia. • The Globivalvulina-Millerella and Eoschubertella-Pseudostaffella zones occur. • The Cerro Prieto Formation is Baskhirian to Moscovian. • Differences in the foraminiferal assemblages support a continental-margin forearc setting. [ABSTRACT FROM AUTHOR]

This paper analyses the lower to middle Eocene carbonate succession exposed at the Island of Pag (Croatia), in the External Dinarides, providing its palaeoenvironmental, palaeobathymetric, and stratigraphic reconstruction. A total of 125 samples have been collected within the Foraminiferal Limestone and the overlying Transitional Beds units cropping out in the sites of Vrčići and Pag for the quantitative analysis of the skeletal assemblage (point counting) and the foraminiferal association (area counting), including both large benthic and small benthic foraminifera. Further samples were collected from the overlying Dalmatian Flysch, to constrain the age of the top of the succession using calcareous nannofossil biostratigraphy. On these bases, the Foraminiferal Limestone has been dated from the Ypresian to the middle Eocene (late Lutetian/early Bartonian). Thanks to the analysis of the skeletal and foraminiferal assemblages, and the use of multivariate statistics, seven main biofacies were identified within the Foraminiferal Limestone and one biofacies within the Transitional Beds. The porcelaneous and agglutinated benthic foraminifera biofacies (BF1) indicates a well-illuminated, oligotrophic to mesotrophic, shallow water, lagoonal environment. The hyaline SBF and encrusting benthic foraminifera biofacies (BF2) developed in a shallow water, inner-ramp environment, and is related to a vegetated seafloor. The nummulitid biofacies (BF3) indicates a moderately high energy, shallow water environment, whereas the comminuted bioclasts and nummulitid biofacies (BF4) corresponds to a low-energy, shallow water environment, and both deposited in inner-to-middle ramp settings. The nummulitid and orthophragminid biofacies (BF5) indicates a moderate energy environment, deposited in middle ramp settings. The nummulitid and serpulid biofacies (BF6) consists of transported material from the inner ramp deposited in middle ramp settings. The orthophragminid and nummulitid biofacies (BF7) indicates a below-wave base, outer shelf setting and the planktic foraminifera biofacies (BF8), recorded in the Transitional Beds, indicates a hemipelagic environment. Based on the foraminiferal counting, quantitative parameters such as the orthophragminids/nummulitids ratio, the planktic/benthic foraminifera ratio, and the hyaline/porcelaneous foraminifera ratio were calculated. These parameters indicate that the succession formed along a distally steepened ramp profile, showing a progressively tectonically-controlled deepening of the depositional environment, culminating with the final drowning of the carbonate ramp. Quantification serves as a crucial instrument for a precise and reliable palaeoenvironmental reconstruction, allowing the comparison amongst different successions. • Eight biofacies identified in the Eocene carbonate succession of Pag (Croatia). • Quantitative analysis of the skeletal and the foraminiferal assemblages • Biofacies formed along a distally steepened ramp profile. • Tectonically-controlled deepening and final drowning of the carbonate ramp • Quantification as a crucial instrument for palaeoenvironmental reconstructions [ABSTRACT FROM AUTHOR]

• Key MFCC factors for limestone and coal distinction was identified. • Mechanics behind MFCC's differentiation of AE in rocks was clarified. • Rock fracture mechanics was revealed by AE parameters. Fractures in the rock surrounding karst caves can result in substantial surface subsidence, especially in mining areas with abundant carbonate rocks. Acoustic emission (AE) is a crucial signal associated with rock fracture mechanics and lithology. This study aimed to distinguish the AE features between coal and limestone using the MFCC-based method and universal AE analysis method in conjunction with uniaxial compression tests. The results indicated that the MFCC-4–6 of AE could distinguish between coal and limestone prior to rock failure. The MFCC-1–6 of limestone exhibited a tail-like pattern change on the stress sawtooth and a step-like pattern change after reaching peak stress. The fluctuation degree of MFCC-2–5 exhibited an initial transition from small to large, followed by a subsequent transition from large to small, reaching its maximum value during the elastic deformation stage. Additionally, the power law distribution index of AE energy in the magnitude range of 102–104 for coal was larger than that for limestone. The AE events in coal were mainly characterized by shear fractures, while limestone exhibited more tension fractures than coal, as indicated by the AF/RA analysis. Furthermore, the lower the AE peak frequency, the larger the scale of fracturing in coal and limestone. These findings are valuable for ground control and early warning of rock failure. [ABSTRACT FROM AUTHOR]

• A dissolution reaction mechanism near the wellbore is expected by injecting CO2 in saline water aquifers. • The injection velocity of CO 2 -saturated brine in limestone significantly impacts the dissolution rate. • At the optimum velocity, the CO 2 -saturated brine creates the thinnest and fastest wormhole. • An optimum Damkholer number is needed to determine the generalized CO2-saturated brine/limestone dissolution mechanism. Deep limestone aquifers are potential CO 2 storage sites, but CO 2 -saturated brine reacts with the carbonate rock, changing its transport and storage properties. This study provided a preliminary investigation of the optimal injection rate of CO 2 -saturated brine in carbonate rocks. Indiana limestone cores were subjected to CO 2 -saturated brine injection at varied rates using an HPHT coreflooding setup with X-ray CT monitoring. The samples were characterized pre- and post-treatment in terms of porosity and pore size distribution using a gas porosimeter and NMR T 2 measurements. Moreover, the reaction was evaluated by measuring the aqueous effluent calcium ions concentration as a function of throughput using ICP-OES analysis. A high-resolution micro-CT scan was used to capture the dissolution post-treatments and characterize the wormhole's size and patterns. Results showed that the wormholes broke through to the sample exit face after injecting 160, 48, and 36 pore volumes at 0.5, 1, and 2 cm3/min, respectively thereby revealing the importance of injection velocity. The ICP-OES analysis revealed that a larger dissolution rate was achieved at 2 cm3/min, which explained the fast wormhole propagation. An increase in rock porosity and the pore-size distributions was observed after coreflooding on all samples with minimum precipitation, as concluded from the NMR T 2 relaxation time. A universal optimum Damköhler number can be obtained that enables calculating the optimum injection rate of CO 2 -saturated brine at different rock and fluid conditions. We speculated that the optimum Damköhler number could be different from the value of 0.29 proposed by Fredd and Fogler (1998). This study provides a preliminary understanding of the optimal CO 2 -saturated brine injection velocity that has an application for CO 2 storage, water alternating gas (WAG) operations, and acid stimulation of carbonate formations. [ABSTRACT FROM AUTHOR]

Detailed field and stratigraphic (lithostratigraphy & biostratigraphy) studies were carried out on the Upper Cretaceous–lower Paleogene successions at Esh-ElMellaha half-graben, Gulf of Suez, Egypt. Four stratigraphic sections were investigated and arranged in a geologic profile extends from south to north as follow: Gabal El-Mellaha, Wadi Abu Had, Wadi Dib and Gabal Tarbul. The field work led to recognize four lithostratigraphic units (formations): Sudr (upper part), Dib, Esna and Thebes (top). The distinctive Dababiya Quarry Member (DQM) which characterizes the Paleocene Eocene Thermal Maximum (PETM) was initially recorded at Esh-ElMellaha region. Sudr Formation is stratigraphically differentiated into two distinctive informal rock units, argillaceous bedded limestone unit and calcareous shale unit. The Dib Formation is here reviewed and correlates with the Dakhla Formation (upper part) in the different geographic neighborhoods of Egypt. It consists of glauconitic carbonate rocks (bioclastic limestone) embracing reworked gravelly and pebbly extra-clasts and broken exhumed mega-fossils (e.g. cephalopods, gastropods and bivalves, corals). Dib Formation is assigned to thelower Paleocene (Danian Stage) according to the occurrence of praemuricids taxa (e.g. Praemurica inconstans and P. uncinata) index fossils. Esna and Thebes formations are assigned to the Ypresian Stage. Dib Formation is bounded by two regional unconformity surfaces (erosional surfaces) as a result of two tectonic events (I and II) linked to Syrian Tectonic Event. • New insights into Esh-ElMellaha stratigraphy were achieved. • Reference section of the Dib Formation was introduced for the first time. • El-Dababiya Quarry Member, which marks the PETM, was defined. • Unconformity surfaces (Paleosol and irregular surfaces) were observed. • Two major syn-sedimentary tectonic events (K/Pg & P/E) were documented. [ABSTRACT FROM AUTHOR]

The rate and amount of Al3+ released from re-solubilization of the Al-containing polymers and minerals due to the increase in proton activity in the soil solution in subtropical regions is scarce in the literature. The objective of the present study was to track the Al3+ reappearance following its neutralization during the switch from a conventional tillage system to a no-till (NT) system. For this purpose, we evaluated a long-term lime experiment under NT on a subtropical Ultisol. The treatments included varying lime rates, with different historic of lime reapplication. Soil samples were taken at the 0–5, 5–10, and 10–15 cm depth in 1988, 1994, 1995, 1996, 2001, 2003, 2006, 2012, and 2022. The re-solubilization of Al-containing soil polymers and minerals in the 0–15 cm soil layer proceeds slowly in the first 10 years; afterwards, the rate and amount of Al3+ released increased. However, regardless of the lime treatment, the soil never returns its natural acidic state, even after 34 years of the first liming operation. A decrease in the intensity of reappearance of exchangeable Al3+ in the soil profile is clearly observed, compared to the treatment without reapplication of surface lime. We have observed that it takes 7–9 years for 10% of the effective cation exchange capacity to be occupied by Al3+ if limestone is not reapplied on the soil surface; if underdoses are reapplied this level can be maintained for 13–15 years. Furthermore, if larger and more frequent lime doses are used, a low Al3+ saturation (<10%) can be maintained permanently. These findings emphasize the importance of an appropriate liming process at the start of NT, followed with surface limestone reapplication, to ensure a very low Al3+ saturation over a long period of time in the 0–15 cm soil layer. • Al re-solubilization in the 0–15 cm layer proceeds slowly in the first 10 years. • After that, the Al3+ released accelerates the acidification in a chain reaction. • Even 34 years after the first liming, the soil never recovered its natural acidity. • It takes 7–9 years to reach 10% of Al saturation when surface liming is not performed. • Findings reinforce the mandatory of an adequate liming process at the beginning of NT. [ABSTRACT FROM AUTHOR]

The Cenomanian-Turonian strata of the Second White Specks (2WS) Formation on the cratonic margin of the Western Interior Seaway (WIS) are comprised of organic-rich, carbonate-siliciclastic successions. This study focuses on a carbonate-siliciclastic succession of the 2WS in two cored wells located on the eastern margin of the Cretaceous Interior Seaway. Based on sedimentary facies and organic/inorganic geochemistry representing distal and proximal sections of the 2WS, it was possible to interpret factors, including productivity, preservation, and dilution of the Organic Matter (OM). The results revealed eight subfacies and three main facies associations, including deep shelf calcareous mudstones and marlstones, and shallow shelf bioclastic limestones. The carbonaceous mudstones have high type II immature kerogen content and the bioclastic limestones have low organic content dominated by type III and degraded type II kerogen. The 2WS mineralogy primarily consists of calcite, clay minerals, and quartz, and is characterized by a low degree of physical and chemical diagenesis. Based on mineralogical analysis, carbonate is the dominant component, and its proportion is inversely associated with terrigenous silica content. There is a general increase in carbonates and a decrease in siliciclastics from the distal to the proximal sections within the study area. Lateral changes in physical and chemical properties of similar facies associations are mainly controlled by changes in water depth. The 2WS was deposited during a long-lived transgression comprised of higher order parasequences. Core logging data from multiple drillholes show that these parasequences have a general coarsening upward trend with an upward shift from pelagic (i.e., planktonic foraminifera and coccoliths) to benthic (i.e., Inoceramus) carbonate productivity. During deposition of the mudstone/marlstone facies association, a clear and oxygenated water column allowed for a high photosynthetic activity to occur within the photic zone, which is reflected in OM enrichment and higher micronutrient content, such as Zn and Ni, predominance of fecal aggregates, and planktonic foraminifera. In the mudstone/marlstone facies, oxygen deficient pore water conditions, which are reflected in the high redox-sensitive trace element concentrations such as V, contributed to the high degree of OM preservation. The 2WS along the eastern margin of the WIS was deposited on a low gradient carbonate ramp environment. The oxygenated broad ramp accommodated the bioclastic limestones, which are characterized by high benthic carbonate dilution rate that resulted in lower OM preservation potential. The shallow shelf setting was characterized by restricted wave energy and minimal fluvial input from the adjacent craton under temperate climatic conditions. This study contributes to our understanding about paleo-oceanography and hydrocarbon exploration in analogous epeiric seas and mixed siliciclastic‑carbonate marine settings around the world. [ABSTRACT FROM AUTHOR]

Recognizing the challenges of low strength, inadequate cementation, significant pore development, and excellent connectivity of reef limestone, as well as the persistent issues of 're-leakage' and increasing leaks when using rigid bridge plugs, this paper posits the use of materials possessing both flexible and rigid properties for the prevention of leaks and plugging in reef limestone formations. Consequently, a plugging material exhibiting external flexibility and internal rigidity is developed (EFIR Material). This synergistic approach employs the deformability of flexible materials and the skeletal support of rigid materials to create a high-strength, dense plugging section. The new design enhances the formation's pressure-bearing capacity while effectively addressing leakage issues. The material's functional structure design, a core-shell structure of EFIR, is achieved by reverse-phase suspension polymerization of acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and alkyl ketone polymer (NVP), water-soluble monomers functioning as the shell and modified sand as the core. The results indicate that EFIR retains significant flexibility and strength upon water absorption and expansion. A sand bed made from 10 to 18 mesh calcareous sand exhibits excellent sealing properties. The optimal dosage of 3%-4% produces robust sealing effects, withstands pressures up to 7 MPa, and results in a tightly cemented, high-strength sand bed post-sealing with reef tuff, displaying high-quality sealing that is resistant to re-leakage. [Display omitted] [ABSTRACT FROM AUTHOR]

This study utilized a synthetic engineering limestone calcined clay (LC3) system to simulate the effects of different grades of calcined clay on the rheological, hydration, and mechanical properties of LC3 mortar. By finely grinding quartz to a particle size akin to that of calcined metakaolin and blending it in proportions ranging from 0 % to 100 %, it was able to explore the detailed relationships between metakaolin content and key properties of the mortar. The results show a nonlinear correlation between metakaolin content and rheological behavior, with 85 % metakaolin content identified as the optimal proportion. At this level, the compressive strength values closely approached those of the 100 % group. The result also highlights the significant influence of water to binder ratio and the substitution of wollastonite for limestone on mortar flowability and mechanical strength. Notably, mixes with higher proportions of ground quartz exhibited delayed hydration and reduced early strength but increased long-term strength due to enhanced pozzolanic reactions. A significant contribution of this study is the modification of the traditional rheological formula specifically for LC3 materials, providing new insights for future research on the rheological properties of LC3 systems. These findings are crucial for the formulation of more efficient, sustainable LC3 systems tailored for specific engineering applications. The optimized rheological formula offers a robust foundation for further exploration and refinement of the balance between workability and mechanical performance in LC3 systems. • Developed a novel LC3 system to explore the effects of different clay grades on rheology. • Unveiled key factors affecting the rheological performance of LC3 mortar. • Recommended clay grades for optimizing both rheological and mchanical properties of LC3. • Modifies the traditional rheological formula of OPC to develop a specific formula for LC3. [ABSTRACT FROM AUTHOR]

Cement manufacturing, a fundamental process industry characterized by high CO 2 emissions, sees over 58% of its emissions stemming from the limestone calcination process. However, this significant source of CO 2 has not yet been adequately addressed by most existing cement decarbonization processes. As such, systematic environmental and economic comparisons between different cement processes are essential. This paper proposes a new cement process (NCP) that uses natural gas to react with limestone to reduce CO 2 emissions and simultaneously produce high-value-added chemical products (methanol). To explore strategies for further improving the performance of the CO 2 emission reduction, two processes are developed, integrating the organic Rankine cycle (ORC) and carbon capture and storage (CCS) units with the traditional cement process (TCP) and the NCP, namely TCP-ORC-CCS and NCP-ORC-CCS respectively. Life cycle assessment (LCA) and economic analysis were performed on the TCP, NCP, TCP-ORC-CCS, and NCP-ORC-CCS processes, revealing their advantages and limitations in different scenarios. LCA adopts the "cradle to gate" system boundary, which includes the whole cement process from ore mining to clinker generation and other processes used for carbon reduction. The LCA results show that four cement processes exhibit different environmental performances when choosing different allocation methods. Under economic allocation, the global warming potential (GWP) of TCP, NCP, TCP-ORC-CCS, and NCP-ORC-CCS are 933, 300, 432, and 194 kgCO 2 eq/ton·clinker, respectively. The comprehensive analysis indicates that NCP has the best comprehensive economic and environmental performance when natural gas and methanol prices are 332 and 319 $/ton, respectively. The price fluctuation of natural gas and methanol is found to greatly impact the levelized cost of clinker (LCOC) of NCP through sensitivity analysis. NCP is economically preferred over TCP when the price of methanol (MeOH) is at least $76 above approximately two-thirds of the price of methane (CH 4). Similarly, NCP-ORC-CCS is more advantageous than TCP-ORC-CCS when the price of MeOH is at least $87 above nearly two-thirds of the price of CH 4. This study provides a comprehensive analysis for low-carbon cement process design to achieve CO 2 emissions reduction. [Display omitted] • Detailed designing and modeling of the low-carbon cement processes. • Adopt CH 4 to calcine limestone, producing syngas and CH 3 OH for carbon reduction. • A framework of life cycle environmental and economic assessment is established. • NCP's GWP and LCOC are 67.84% and 20.79% lower than TCP under specific conditions. • Price fluctuation of CH 4 and CH 3 OH strongly impacts the LCOC of NCP-based. [ABSTRACT FROM AUTHOR]

The benefits of limestone waste as a partial replacement of cement have been well established. In this paper, to better understand the effect of limestone waste on the properties of cement-based materials, the hydration process and microstructural properties of cement are evaluated. The results showed that the limestone waste decreased the fluidity of cement mortar, while the mortar having up to 10 % limestone waste provided competitive properties with pure cement mortar. It is concluded that the presence of limestone waste has both negative and positive effects simultaneously on the hydration and microstructural properties of the cement paste. During the hydration process, the net reaction heat of limestone waste in the cement blends ranged from 0.38 J/g to 4.1 J/g. In addition, the thermodynamic modeling and XRD indicated that the monocarbonate and hemicarbonate were stable in the limestone-cement blends, and the limestone waste increased the stability of ettringite. • The effect of limestone waste on the hydration and strength development of cement was investigated. • The net reaction heat of the limestone fines in the cement system was 3.5 J/g∼4.1 J/g. • An appropriate content of the limestone waste improves the chemical shrinkage of cement. [ABSTRACT FROM AUTHOR]

Dissolution of carbonate minerals in karst aquifers has long been recognized to result from recharge of surface water undersaturated with respect to calcite from carbonic acid produced by hydration of dissolved atmospheric and respired CO 2. However, dissolution also results from additional acids produced by reactions of redox sensitive solutes in the subsurface, which may represent a source of CO 2 to Earth's atmosphere. Because the magnitude of dissolution by these additional acids is poorly constrained, we compare here fractions of dissolution from initial surface water undersaturation and subsurface redox reactions. Estimates are based on chemical mixing and geochemical (PHREEQC) modeling of time series measurements of water compositions at a spring vent that receives surface water during stream flooding and a stream sink-rise system in north-central Florida. During a single spring reversal, 9.2 × 105 kg of limestone dissolved. At the stream sink-rise system, where subsurface residence times are shorter than during the spring reversal, both limestone dissolution (102–104 kg) and precipitation (102–105 kg) occur as water flows through the conduits with residence times ranging from 10 to 70 h. At both sites, maximum calcite dissolution rates of ∼10 μM hr−1 occurs at subsurface residence times between 30 and 50 h. For subsurface residence time > ∼20–60 h, the models indicate that production of additional acid in the subsurface is required for ∼53 ± 7% of dissolution. Oxidation of organic carbon, ammonium, pyrite, iron, and/or manganese produce sufficient acid for additional dissolution, but dissolved oxygen is insufficient for these reactions, indicating some acidity is generated under anerobic conditions. Dissolution caused by subsurface reactions in our samples represents mobilization of 20 × 104-30 × 104 kg of CO 2 via remineralization of organic carbon or carbonate dissolution by nitric and sulfuric acids. Acid produced by subsurface redox reactions during surface water-groundwater interactions, including non‑carbonic acids, are important in conduit development and carbon cycling in the carbonate critical zone. • Surface water-groundwater exchange enhances carbonate dissolution. • Dissolution depends on residence time of recharged water in the subsurface. • Carbonic, sulfuric, and nitric acids from subsurface reactions aid dissolution. • Surface and subsurface acid sources can cause equal amounts of dissolution. • Dissolution by subsurface acid sources may release CO 2 to the atmosphere. [ABSTRACT FROM AUTHOR]

Almost all igneous rocks are composed of silicate minerals; carbonatites are the main exception to this rule. They form only a minor proportion of the continental crust but are of fundamental scientific and economic importance. These rocks, originally described as a limestone (Kaiserstuhl, Germany) or magmatic limestone (Alnö, Sweden), were recognized in 1921 by W. C. Brøgger as a distinct magmatic rock type under the name "Karbonatite" in the Fen complex (Norway). Extensive field mapping in Africa, and particularly studies within the Chilwa Alkaline Province (Malawi), have led to the discovery of diverse intrusive and extrusive carbonatites. The latter, including the Fort Portal volcanic field in Uganda, Rufunsa Province in Zambia, and Oldoinyo Lengai volcano in Tanzania (the only volcano ever to have been seen to erupt carbonatites), have been exceptionally important in the recognition of carbonatites as truly magmatic rocks. The possibility of the existence of carbonate melts has been confirmed and shown by experimental studies of diverse carbonate systems with added volatile components (H 2 O, F) and alkali elements (Na, K). The study of the Oldoinyo Lengai gregoryite-nyerereite carbonatites, which are mineralogically and compositionally different from all known carbonatites worldwide, has led to long-lasting discussions about the origin of carbonatites. This includes composition of primary/parental carbonate melt, derivation of carbonatites by either liquid immiscibility or fractional crystallization, carbonatite evolution, and especially, the possible genetic relationships between alkali-rich and alkali-poor carbonatites. The rapid alteration of Oldoinyo Lengai carbonatites and their transformation to calcite carbonatite-like rocks has been proposed as the explanation for the absence of alkali-rich carbonatites in the geological past. Detailed mineralogical studies have shown that the occurrence of nyerereite is not restricted to Oldoinyo Lengai and that this mineral is now known to occur in other carbonatites (e.g., Guly, Kovdor, Oka, Kerimasi), alkaline rocks, and kimberlites (and even in diamond). This would suggest compositionally different mantle-derived melts enriched in alkali elements. In addition, carbonatite tephra has an important role in the preservation of some key paleontologic and anthropologic localities in East Africa. Despite these important discoveries, several problems related to carbonatite petrogenesis are not yet resolved. Future work is required, and carbonatites within Africa, with its key localities, may help to solve these problems. • The Kaiserstuhl volcano is the first locality where carbonatites were described in 1783. • Field observations are the key evidences for recognition of carbonatites as magmatic rocks. • Oldoinyo Lengai is the only active volcano that erupts gregoryite-nyerereite carbonatite. • Alkali-rich carbonatites are important for the understanding of carbonatite genesis and evolution. • Existence of compositionally different carbonatite melts is confirmed by experimental studies. [ABSTRACT FROM AUTHOR]

Most carbonation reactions are characterized by products encasing unreacted particles, leading to incomplete reactions and consequently lower material utilization efficiency. This study introduces a novel approach for preparing gradient carbonated materials by partially calcined limestone (PCL), which is calcined below full calcination temperatures to maintain some original limestone while partially transforming into lime. The mechanical strength, phases evolution and microstructure were investigated. The results indicated that the mechanical properties of the materials improve continuously and porosity markedly decreases as the calcination degree of PCL increases, peaking at around 35 %. However, excessive calcination degree impedes the formation of a compact structure. Simultaneously, the carbonation process yields CaCO 3 with a lower decomposition temperature, exhibiting two distinctive microstructural features: an encapsulating layer on the surface of unreacted limestone and the tiny particles (<5 μm) scattered between the layers. This study presents a promising approach to carbonated material design, demonstrating that through controlled partial calcination of limestone, opening avenues for more efficient material utilization. [ABSTRACT FROM AUTHOR]

Late Pleistocene (≈21000 BP) travertine and calcareous tufa deposits have been recognized in the region of Boulaaba, Kasserine in Central Tunisia with a variety of morphological aspects and depositional facies. Morphological aspects of these deposits consist of two elongated continental Ca-carbonate masses defined as fissure-ridges built-up around old fissure networks. Distinction between travertine and tufa lithofacies, based on textural, compositional and topographic settings regarding the entire carbonate masses, have led for travertine to 5 lithofacies: (1) banded travertine fissure infill, (2) bacterial shrubs, (3) stromatolitic laminae, (4) pisoids and (5) speleothem-like travertine growth habits. Tufa is composed of autochtonous tufa lithofacies with (1) phytoherme framestone tufa, (2) calcified insect larval constructions, and clastic alllochtonous tufa lithofacies with (1) matrix-supported microdetrital tufa and (2) grain-supported macrodetrital phytoclast tufa. Both lithofacies show variable diagenetic evolutions with an overall lithification. These deposits are concentrated along the Foussana trough-related normal faults and fractures that belong to the extensional regime of the major strike slip fault of Kasserine that enhanced and facilitated fluid upwelling along with movements of faults which damage and fracture the rocks and increase the overall permeability. During this phase (Late Pleistocene), the deposition of Boulaaba travertine and tufa has implied some paleo-hydroclimatic conditions marked in most North African travertine and tufa depositing sites by (1) a higher water table with abundant effective rainfall on the recharge areas, (2) dense plant cover and soils giving acidic water infiltrations, (3) karstic dissolution of Cretaceous limestones (especially the limestone aquifers of Bireno and Abiod), and (4) a strong water mineralization of the groundwater. [ABSTRACT FROM AUTHOR]

• Laser induced breakdown spectroscopy (LIBS) technique for the in-depth analysis of nanoparticles used in cultural heritage field. • Biocidal treatment based on silver/titanium nanoparticles applied to limestone employed in heritage buildings for protective purposes. • High sensitivity LIBS technique for detecting a small amount of nanoparticles treatment. Four biocidal treatments based on nanoparticles were designed and their penetration depths were characterized by laser-induced breakdown spectroscopy (LIBS) technique. This kind of biocidal nanoparticles are being studied to be employed in historic buildings and stone monuments due to their capability to inhibit the growth of biofoulings. The effectiveness of the treatment is related to the penetration depth of the nanoparticles in the limestone pore. For this reason, LIBS depth profiling was used in this work to characterize the diffusion of the nanoparticles in the limestone matrix and to compare the penetration depth of the different treatments. Four different nano-biocides based on silver/titanium dioxide nanoparticles were analysed by LIBS in limestone from Novelda quarry (Alicante, Spain). This limestone has been widely employed in both historical and contemporary buildings in Spain. The positive detection of the emission line of Ag at 338.289 nm was examined in the depth-related emission spectra as evidence of the presence of the silver nanoparticles and derived nanocomposites in the limestone matrix. The LIBS depth-profiles that were generated, showed a decrease of the Ag net signal with depth due to the diffusion of the nanoparticles in the limestone. Furthermore, the comparison of the in-depth sequences of spectra, and of the Ag depth profiles evidenced penetration differences between the nano-biocides which were explained by differences in the hydrodynamic diameter of the nanoparticles that would affect their diffusion in the limestone pore. The results of this assessment demonstrate the capability and potential of LIBS technique for the in-depth characterization of the nanoparticles and for the comparison of the effectiveness of nanoparticles biocidal treatments based on their penetration in the stone matrix. [ABSTRACT FROM AUTHOR]

Removal of cationic and anionic contaminants from surface waters with the same natural material is relevant both from environmental and economic points of view. Cationic contaminants can be removed by adsorption, while anionic ones – by the formation of insoluble calcium salts. In this study, nickel was taken as an example of a cationic pollutant and phosphate – an anionic pollutant. To test the removal efficiency of these substances, natural limestone and dispersed, thermally activated limestone were compared. Dispersed, thermally activated limestone gave better results of Ni2+ and PO43– removal from all water solutions than natural limestone. This was due to its dispersion and subsequent heating to 240°C–250°C. As a result, limestone was destroyed and the calcite crystals broke apart. The doses of limestone were 2.0 and 4.0 g/L, the initial pH was 5 and 7, and the total dissolved solids (TDS) was at 0.02 and 0.55 g/L. Measurements of changes in the pH, Eh and TDS values were carried out. At water pH increase, the efficiency of Ni2+ removal decreased, while the efficiency of PO43– removal increased. For purification of surface water by limestone, the selection of its type and dose depends on the usage of the water body. [ABSTRACT FROM AUTHOR]

The vinasse is a liquid effluent resulting from the sugarcane processing for ethanol production. Ten to 18 L of vinasse are generated per liter of ethanol produced. It has a high polluting potential due to its organic load and solid concentration that can cause environmental damage if mismanaged, but since the 1980s it has been used for fertirrigation. Treatment by anaerobic digestion removes organic matter, solids, and as a by-product produces biogas and biofertilizer. As vinasse has low buffering power, it generates instability in the anaerobic process. In reactors, the gradual neutralization with limestone is adequate because this material is available in the rural environment, which is capable of providing alkalinity in an easy-to-use process. The same occurs when we use bovine manure as an inoculum alternative. The objective of the study was to evaluate the reactors startup to propose criteria for the anaerobic treatment of vinasse at thermophilic temperature. We used two 15-liter useful-volume UASB reactors, each inoculated with fresh sieved manure, in addition to 16 kg of limestone as fixed bed and alkalizing agent. The reactors acclimatization happened in three temperature ranges: (i) ambient (26 ± 2 °C); (ii) mesophilic (36 ± 2 °C), and thermophilic (52 ± 2 °C). We evaluated efficiency by the biogas yield generated and the removal of COD, when the temperature increased from 26 to 52 °C and the organic load from 0.02 to 1.70 gCOD.L−1.d−1. We quantified solids (Totals and Volatile Totals), pH, total alkalinity, and volatile acidity. Results showed that diluted manure produced 0.11 Lgas.gConsumedCOD−1 at 48 days of the stabilization phase, which lasted 72 days, ending with the sludge COD at 8.4 gO 2.L−1. During the inoculum acclimatization, HRT was adjusted to 4 days, maximum vinasse organic load to 1.70 gCOD.L−1, and total alkalinity/volatile acidity ratio varied from 0.14 to 0.86; pH remained between 6.6 and 8.3. This demonstrates the reactors' capacity to withstand load variation and temperature increase. In the same period, the average gas production was 0.13 Lgas.gConsumedCOD−1, which is considered adequate for the startup. [Display omitted] [ABSTRACT FROM AUTHOR]

The stratigraphical features and palaeoenvironmental conditions of the uppermost Albian-lower Turonian succession of the eastern Algerian Saharan Atlas domain are described for the first time. Two formations have been recognised, called the Ouled Serradj and the Chemla, respectively. Ammonites and calcareous nannofossils enable us to assign the Ouled Serradj Formation to the upper Albian-Cenomanian and the Chemla Formation to the uppermost Cenomanian-lower Turonian. Based on the field data and microfacies studies, the strata of these formations are arranged into eight microfacies types (MT 1 to MT 8) that are described in terms of depositional environments and grouped into three main facies associations (FA-1 to FA-3): FA-1 (MT 1–4), deep-water outer platform marl-dominated facies association 1 with limestone intercalations; FA-2 (MT 5 and 6), mid-platform marl-dominated facies association 2; and FA-3 (MT 7 and 8), mid- and inner platform limestone-marl facies association 3. • Cenomanian-Turonian sea-level change and OAE2 deposition in the Southern Tethys shelf. • Cenomanian-Turonian ammonite and calcareous nannofossil biostratigraphy. • Microfacies and depositional sequences. [ABSTRACT FROM AUTHOR]

In this paper, multi-ion transference numbers were determined throughout the chloride migration testing of low clinker cement-based materials. For this purpose, five cement pastes were studied: pure Portland paste (as a reference) and four other pastes, based on limestone filler, fly ash, slag or silica fume. The transference numbers were calculated from the concentration evolution in the three zones of the migration cell (catholyte, anolyte and sample), considering that: (i) ions moved in the catholyte and anolyte; (ii) ions leached from the sample; (iii) ions were generated from the electrode processes, and (iv) the pore solution of the sample evolved during the test. The chloride transference numbers of pastes with pure Portland cement, limestone filler, fly ash, slag or silica fume are almost zero at the beginning of the migration test but 0.23; 0.18; 0.06; 0.05 and 0.20 at the end of the test, respectively. The ion transference numbers obtained were used for the calculation of diffusion coefficients of chlorides, sodium and potassium using the Nernst-Einstein equation. [ABSTRACT FROM AUTHOR]

Calcined clays, combined with limestone, exhibit significant potential as SCMs for achieving high clinker substitution levels. This is partly related to their high aluminum and silicon contents. Binary Portland cement – calcined clay (PC2) blends and ternary blends with limestone (LC3) have been examined using metakaolin (MK) as calcined clay for blends with low and high MK/clinker ratios. The hydration reactions (up to 420 days) and aluminum distribution within the C-(A)-S-H and calcium aluminate hydrate phases have been quantitatively assessed by 27Al and 29Si NMR spectroscopy. The presence of limestone induces higher amounts of ettringite in the LC3 blends, resulting in lower amounts of Al(4) in the C-(A)-S-H. For the high MK/clinker ratio blends, the increase of aluminum incorporated in the C-(A)-S-H phase after prolonged hydration coincides with a leveling off for the amount of AFm phases for the binary and ternary blends at 60 % and 40 % of MK reaction, respectively. [ABSTRACT FROM AUTHOR]

Upper Paleozoic rocks crop out in the central part of Sonora, northwestern Mexico. The Sierra La Flojera, located southeast of Hermosillo City, is an isolated hill with a north-south orientation whose age remains controversial due to the scarcity of well-preserved fossils. However, previous information points out the occurrence of rocks from the Pennsylvanian-Permian and the Upper Triassic (Carnian). This paper focuses on the Permian rocks and describes a stratigraphic succession mainly composed of sandstone, conglomerate, limestone, and fossiliferous limestone with abundant fusulinids, and bryozoan, brachiopod, gastropod, and crinoid remains deposited on a shallow marine shelf. The Permian (early Leonardian) age was determined based on the occurrence of the fusulinids Paraskinnerella sp., Skinnerella sp., and Chalaroschwagerina sp., and Paraschwagerina sp. (reworked), which were associated with crinoid-isolated columnar plates of Preptopremnum cf. laeve. The fossil record studied points out that the Sierra La Flojera section was deposited during the early Leonardian and is coeval with other localities of Sonora, Chihuahua, and Coahuila (Mexico), and California and Texas (USA). • Permian stratigraphy from Sierra La Flojera, central Sonora, is described by first time. • These rocks were deposited on a shallow marine shelf. • Biota is composed of Paraskinnerella, Skinnerella, Chalaroschwagerina , and Paraschwagerina. • The Sierra La Flojera section was deposited during the early Leonardian. [ABSTRACT FROM AUTHOR]

Well-preserved, distinctive columnar microbialites were discovered in the Wirrealpa Limestone (Stage 4, Series 2 of Cambrian) of South Australia. However, further studies are still required to unveil the microstructure and formation process of these microbialites. A microbial buildup from the Wirrealpa Limestone examined herein suggests that the microbialitic columns are composed of densely-distributed, polymorphic, and patched fabrics produced by microbes. These fabrics are inter-framed by packstone sediments that characterized by calcareous metazoan skeletons and cerebroid ooids. The patched fabrics can be categorized into three types: 1) laminated 'patches', 2) homogeneous microsparitic 'patches' (mesoclots), and 3) cemented 'patches' containing tightly-packed chancelloriid sclerites. There are two preservational conditions of chancelloriid sclerites. After death of the chancelloriid individuals (belonging to Chancelloria and rare Allonnia) that dwelled among or near the microbial reef, abundant sclerites were exfoliated, transported, and concentrated. Then, some of them were cemented by microbial communities, forming the third type 'patches', while others were accumulated in the packstones within reefal cavities and inter-framework space along with many skeletal fragments from trilobites and mollusks. Thus, this lower Cambrian thrombolite-stromatolite complex was formed within an ecosystem lacking archaeocyaths but dominated by microbes (reef builders) and chancelloriids (reef dwellers). • A columnar Cambrian microbialite is composed of three types of microstructures. • Chancelloriids were important dwellers of an early Cambrian microbial buildup. • Microbes have cemented chancelloriid sclerites to consolidating the microbialite. • Metazoan-microbial reefs/consortia were sophisticated during the Cambrian Explosion. [ABSTRACT FROM AUTHOR]

• Research shows dolomite increases upwards in unique stromatolites. • Proposes microbial involvement in dolomitization, differing from traditional models. • Evidence includes XPS, isotopes, and pyrite findings. Clarifying the mechanism of dolomitization is of pivotal importance and represents a burning issue among geologists. A comprehensive model to define the genesis of dolomitization in the Cambrian Chaomidian Formation carbonates is still lacking. In the highly focused study, the advanced integration of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), clumped isotope and carbon/oxygen isotope analyses was used to reveal complex interactions between the genesis and dolomitization of a stromatolite mound in the late Cambrian Chaomidian Formation of China. The results show that the dolomite content increases from bottom to top, along with a shift in lithology from limestone to dolostone. Additionally, as we moved from the base to the summit of the stromatolite mound, the Fe, Mn, and Na contents increase with increasing Mg levels, whereas the δ13C and δ18O values became more positive. Conversely, the levels of Sr and total rare earth elements (REEs) gradually decreased. The dolomite grains in the stromatolite mound are micritic and euhedral to subhedral, with foggy cores and bright edges and low cation ordering. The stromatolite limestone, dolostone, and underlying lime mudstone samples exhibit similar REE patterns: light REE enrichment, heavy REE loss, negative δEu anomalies, and weak negative δCe anomalies. The δ13C and δ18O values fall within the late Cambrian seawater range, suggesting that dolomitizing fluids originated mainly from concentrated seawater and migrated from top to bottom. The δ18O values indicate lower dolomite formation temperatures than calcite formation temperatures, supporting dolomitization during the penecontemporaneous diagenetic stage. Petrographic evidence reveals the presence of pyrite, indicating sulfate-reducing bacterial activity during diagenesis. XPS analysis revealed similar organic functional groups in both the stromatolite limestone and the dolostone, including C-(C = O)-O, C–C/C-(C–H), C-O and C-N. However, the dolostone spectrum exhibited a larger C-OH/C-O peak area, suggesting significant microbial organic matter involvement in dolomite formation. While a kinetic obstacle is recognized as a primary cause of dolomite formation, this study also suggested that microbial activity weakened this obstacle during diagenesis. Thus, microbial metabolism or cyanobacterial decomposition facilitates dolomite formation during the penecontemporaneous diagenetic stage. [ABSTRACT FROM AUTHOR]

The Inception Horizon Hypothesis (IHH) postulates that certain stratigraphic horizons in a limestone sequence, combined with structural surfaces such as joints, provide a framework for cave development. Although subsurface and surface karst landforms are fundamentally linked, the IHH has not yet been extended to surface karstification. We tested this extension of the IHH in the world-renowned Burren karst due to its stratigraphic and structural simplicity. We used very high-resolution remote sensing datasets and detailed fieldwork to develop an updated map of the Burren's surface karst features, combined with a 3D geological model containing over 60 km of mapped cave passages. Our analysis shows that karstic connectivity between the surface and subsurface is primarily provided by a suite of vertically-persistent calcite and silica-rich veins, which form a non-stratabound fracture system across the Burren. The flow pathways provided by these veins then intersect the following inception horizons: (i) boundaries between distinct lithological units in the limestone sequence; (ii) crinoidal cycle tops, and more sporadically chert lenses, within one of those units (the Slievenaglasha Formation); (iii) thin horizons of non‑carbonates ('clay wayboards') within another unit (the Aillwee member). At the surface, the same horizons have been preferentially exploited by glacial processes, creating surfaces from which meteoric waters now recharge the subsurface and form new surface karst depressions and other karst landforms. Our new inception framework for karstification thus provides a new basis for understanding surface and subsurface connectivity in the karst critical zone in the Burren landscape, and it provides new geological insight into the functioning of carbonate critical zones more generally. [ABSTRACT FROM AUTHOR]

Thermochemical energy storage has received wide attention recently due to its high energy storage density and power cycle efficiency. However, most researchers focus on synthesizing new calcium-based heat storage materials, and there is still a significant knowledge gap on the effects of operating conditions on the carbonation behaviors of the calcium-based particles. In this study, the effects of carbonation temperature, CO 2 concentration and raw particle size on the carbonation rate, conversion ratio and particle diameter were experimentally investigated. The results showed that the carbonation rate peaked between 873 K and 973 K, and it decreased at 1023 K due to sintering. Increasing the CO 2 concentration from 15 vol% to 50 vol% enhanced the carbonation rate, while the promotional effect was weaker at higher CO 2 concentrations. The maximum conversion ratio of the CaO particles was independent of the CO 2 concentration, and the particle diameter increased by 7.3 % after the carbonation process. Additionally, a carbonation model was developed and validated by the experimental results. Simulation results revealed that increasing the raw particle size from 0.1 mm to 0.5 mm caused the carbonation reaction to transition from a kinetic-controlled regime to a diffusion controlled regime, significantly reducing the carbonation rate. • Effects of operating conditions on limestone carbonation behaviors are investigated. • The maximum conversion ratio of limestone is independent of the CO 2 concentration. • The limestone particle diameter increases by 7.3 % after the carbonation reaction. • A carbonation model is developed and validated by the experimental results. • Carbonation is diffusion controlled when the raw particle size is 0.5 mm. [ABSTRACT FROM AUTHOR]

This paper focuses on the study of the reaction between limestone and sodium hydroxide solution. This reaction is used to produce alkali-activated mortars after curing and in the presence of unreactive siliceous sand. The kinetics of this reaction is investigated by semi-adiabatic calorimetry experiments. The formulation parameters are fixed but the curing parameters are tested: temperature (38 and 45°C) and time of drying (14, 25, 27 and 28 days). Their impact on reaction products (identified by FTIR and thermal analysis), on microstructure (SEM observations and porosity measurements) and on mechanical strength (flexural and compressive tests) are determined. The reaction was fast and a temperature drying was required to obtain stabilized hydration products in mortars. The products of the alkali-activation of limestone are double sodium/calcium carbonate (mainly pirssonite and with specific conditions of curing gaylussite) and calcium hydroxide. The microstructure and the proportions of reaction products, impacted by drying conditions, influence the mechanical strength of mortars. With an appropriate time (25 days) and temperature of drying (45°C), the compressive strength reached, after 28 days, almost 25 MPa. • The reaction between limestone and sodium hydroxide solution take place in two stages. • FTIR measurements allow the identification of stages of the reaction process. • Drying in the curing process is necessary to end the crystallization stage. • Curing temperature plays an important part in the nature of reaction products. • The microstructure and the strength of alkali-activated mortars are linked to the curing process (time and temperature). [ABSTRACT FROM AUTHOR]

Limestone decarbonation to obtain CaO (calcium oxide) and produce cement is an industrial activity with enormous CO 2 emissions (CaCO 3 (s) → CaO (s) + CO 2 (g) ), due to the intrinsic calcination reaction of CaCO 3 (calcium carbonate), in addition to the use of fossil fuels. One of the most recent ideas to reduce CO 2 emissions in this process has been the electrochemical decarbonation of limestone where Ca(OH) 2 (calcium hydroxide) is obtained as an intermediate product that is then used as CaO precursor in clinker synthesis. This study shows the design of a low-cost electrochemical reactor and the optimization of the parameters to produce Ca(OH) 2 with high purity and yield from the decarbonation processes of pure CaCO 3 and limestone used in the cement industry. In addition, the remaining limestone sludge and electrolytic solutions were analyzed, and it was found that the sludge can be used as a correction material in clinker preparation, and it is also possible to reuse the electrolytic solution twice. Finally, the main finding is the proposal of a new clinker synthesis, which results in a cement with comparable characteristics to those of ordinary Portland cement, using Ca(OH) 2 obtained from the electrochemical decarbonation of CaCO 3 , achieving a reduction in CO 2 emissions of approximately 90% compared to the conventional method. [Display omitted] • Selection of electrochemical decarbonation parameters for CaCO 3 into Ca(OH) 2. • Ca(OH) 2 electrochemical production with high purity and yield. • Potential reuse of limestone sludge obtained from electrochemical process. • First approximation to clinker production using electrochemical Ca(OH) 2. [ABSTRACT FROM AUTHOR]

• Effect of initial fracture network properties on dissolution processes. • Control of boundary condition on incipient karst genesis. • Effect of fractures intersections types on karst genesis. A karst system is generally difficult to characterize especially regarding its conduits pattern and morphology. Even though speleology allows to map the geometry of cave systems, a large part of karst conduit networks remains unreachable underground. In this study, we use a reactive transport model that simulates dissolution processes in fracture networks to investigate the effect of discrete fracture network (DFN) properties (i.e., anisotropy, connectivity, fracture intersection types) on incipient karst conduit geometry under different boundary conditions (constant hydraulic head versus constant flow rate conditions, directional versus concentrated recharge conditions). We focused on single fracture (with/without cementation) and ladder like fracture networks which are common on limestone. Results show that fracture network properties, play a major role in the final geometry and topology of the incipient karst conduit patterns. Also, the presence of cement on a single fracture favors tortuous and curvilinear wormholes, while the anisotropy of the fracture network favors the formation of anisotropic incipient karst geometries. Finally, the type of hydraulic BC remains a major factor that governs dissolution processes and thus incipient karst conduit geometry. [ABSTRACT FROM AUTHOR]

The Late Triassic marks the inception of marine calcareous nannoplankton. However, calcareous nannofossil of this period have been found so far only in successions of the eastern Panthalassa Ocean, and from the western and southern Neo-Tethys Ocean. A new middle to late Norian (Late Triassic) calcareous nannofossil association is presented for the first time from Hongyan section at Baoshan block in the Palaeo-Tethys. Here, the calcareous nannofossils association is composed of Prinsiosphaera triassica , P. sp., and Orthopithonella geometrica and calcispheres. The assemblage is predominantly composed of Prinsiosphaera , accounting for >90% of the relative abundance, with a small amount of calcispheres and Orthopithonella geometrica. Similar to the western Tethys, Prinsiosphaera makes up 0.1–1.1% of the limestone volume in the Baoshan block. The mean diameter of Prinsiosphaera decreases from approximately 8.0 to 6.2 μm in the upper Norian (Sevatian), and average volume reduction of approximately 50%. The change in size is coeval with negative carbon and oxygen isotope excursions of the Norian, suggesting a temporal coincidence between C-cycle perturbations, global warming and a dwarfing of Prinsiosphaera. • First report of Norian calcareous nannofossils from the eastern Tethys. • Prinsiosphaera dominates the calcareous nannofossil association in eastern Tethys. • A dwarfing of Prinsiosphaera during the Norian warming event is observed. • Prinsiosphaera susceptible to environmental changes and may adapted to an r-strategy. [ABSTRACT FROM AUTHOR]

Turritelline gastropod-dominated assemblages (TDAs) are common in siliciclastic facies from the mid-Cretaceous to the Recent, but their distribution in carbonate facies has been thought to be limited to the Cretaceous and Paleogene, except for "cool-water" carbonates from the Miocene of Australia. This paper describes a TDA in a Pliocene limestone in northern Chile, the only known Neogene TDA limestone from outside Australia. This Chilean TDA probably formed in conditions of relative low temperatures and high productivity, and thus appears to support the hypothesis that TDAs largely disappeared from warm waters after the Oligocene. It is also possible, however, that it formed in conditions of warmer temperatures associated with upwelling during the Early Pliocene warm interval. • A turritelline gastropod-dominated assemblage from Chile is Early or Late Pliocene. • The limestone assemblage is a rarity in the Neogene, when most are in siliciclastics. • The assemblage formed under high-productivity conditions. • If Late Pliocene, conditions were cool water upwelling, unusual for a limestone. • If Early Pliocene, they were non-uniformitarian warm water upwelling in a warm ocean. [ABSTRACT FROM AUTHOR]