Carbonate Production Research Articles

A CO2-philic ferrocene-based porous organic polymer for solar-driven CO2 conversion from flue gas

A ferrocene based polymer (Fc-POP) is designed for solar-driven CO2 cycloaddition from flue gas, resulting in high CO2-philic (adsorption capacity, 5.38 wt%, 0.15 bar) and outstanding styrene carbonate productivity (93%, 15 vol% CO2).

Paleoenvironmental constraints on shallow-marine carbonate production in central and West Texas during the Albian (Early Cretaceous)

The Albian Glen Rose Formation in central and west Texas records carbonate sedimentation in a broad epicontinental sea partly contemporaneous with Oceanic Anoxic Event 1b. The paleogeographic setting of the Comanche Platform facilitated the deposition of carbonate sediments that resulted in carbonate matrix-rich facies, with various amounts of allochems, which permitted the interpretation of shallow lagoon depositional settings. Geochemical proxies for environmental conditions (nutrient supply, detrital input, redox conditions) were calculated from the elemental geochemical analysis of samples, while their carbon and oxygen isotope composition was used to evaluate the impact of diagenesis. The statistical analysis of this dataset helps identify three intervals within the Glen Rose Formation where the matrix-rich carbonate sedimentation was modulated by environmental parameters. First, the strong correlation between MgO concentration and δ18O vectors on a Principal Component Analysis for the whole dataset confirms the deposition of dolomitic series with stromatolites in a restricted environment. Second, moderately high nutrient input and low detrital flux suggest that part of the sedimentation in west Texas was affected by upwelling. Third, mesotrophic conditions associated with a patch reef made of rudist bivalves support their suspension feeder ecological behavior. Conclusions drawn for this research may apply to other shallow-marine series deposited in broad epicontinental seas affected by greenhouse conditions.

The Influence of Agitation Rates, pH and Calcium Carbonate on L-lysine Production by Bacillus subtilis using Agricultural Products as Carbon and Nitrogen Sources

L-Lysine is an essential amino acid that is required in the diet of humans and animals. It is utilized in human medicine, cosmetics and pharmaceutical industry. ’The influence of agitation rates, pH and calcium carbonate on L-lysine production by Bacillus subtilis using agricultural products as carbon and nitrogen sources was studied. The L-lysine-producing bacteria had already been isolated from Nigerian soil. They were purified and Identified as B. subtilis PR13 and B. subtilis PR9, using cultural, biochemical and molecular characteristics. Optimization of some parameters which included agitation rates, pH values and CaCO3 concentrations, on L-lysine production by the Bacillus species was carried out. The L-lysine was produced in 250 ml flasks containing fermentation media (FM1 and FM2). The findings revealed that, enhanced L-lysine yield of 2.10 and 1.33 mg/ml was observed at agitation rate of 180 rpm for B. subtilis PR13 and PR9 respectively. There was a positive correlation between agitation rates and L- lysine production by B. subtilis PR13 and PR9 (r = 0.96 and 0.83 respectively). The pH of 7.5, stimulated optimum L- lysine yield of 2.27 mg/ml for PR13 and 1.38 mg/ml for PR9. There was a positive correlation between pH values and L-lysine production by B. subtilis PR13 and PR 9 (r = 0.63 and 0.50 respectively). The supplementation of 40g/l of CaCO3, enhanced optimum L-lysine yield of 2.18 mg/ml for B. subtilis PR 13 and 1.30 mg/ml for B. subtilis PR9. There was a positive correlation between varying concentrations of calcium carbonate and L-lysine production by the B. subtilis PR13 (r =0.35), while negative correlation was observed for B. subtilis PR 9 (r = -0.10). The results obtained in the study illustrated that the optimization of process parameters could increase the L-lysine yield from agricultural products by B. subtilis PR13 and B. subtilis PR9.

Microscopic mechanism study and process optimization of dimethyl carbonate production coupled biomass chemical looping gasification system

Biomass chemical looping gasification technology is one of the essential ways to utilize abundant biomass resources. At the same time, dimethyl carbonate can replace phosgene as an environment-friendly organic material for the synthesis of polycarbonate. In this paper, a novel system coupling biomass chemical looping gasification with dimethyl carbonate synthesis with methanol as an intermediate is designed through microscopic mechanism analysis and process optimization. Firstly, reactive force field molecular dynamics simulation is performed to explore the reaction mechanism of biomass chemical looping gasification to determine the optimal gasification temperature range. Secondly, steady-state simulations of the process based on molecular dynamics simulation results are carried out to investigate the effects of temperature, steam to biomass ratio, and oxygen carrier to biomass ratio on the syngas yield and compositions. In addition, the main energy indicators of biomass chemical looping gasification process including lower heating value and cold gas efficiency are analyzed based on the above optimum parameters. Then, two synthesis stages are simulated and optimized with the following results obtained: the optimal temperature and pressure of methanol synthesis stage are 150 °C and 4 MPa; the optimal temperature and pressure of dimethyl carbonate synthesis stage are 140 °C and 0.3 MPa. Finally, the pre-separation-extraction-decantation process separates the mixture of dimethyl carbonate and methanol generated in the synthesis stage with 99.11% purity of dimethyl carbonate. Above results verify the feasibility of producing dimethyl carbonate from the perspective of multi-scale simulation and realize the multi-level utilization of biomass resources.

Reinforcement of Calcareous Sands by Stimulation of Native Microorganisms Induced Mineralization

Calcareous sand is a special soil formed by the accumulation of carbonate fragments. Its compressibility is caused by a high void ratio and breakable particles. Because of its high carbonate content and weak cementation, its load-bearing capacity is limited. In this study, the optimal stimulation solution was obtained with response surface methodology. Then, the effect of reinforcing calcareous sand was analysed with unconfined compressive strength (UCS) tests, calcium carbonate content tests, microscopy and microbial community analyses. The components and concentrations of the optimal stimulation solution were as follows: sodium acetate (38.00 mM), ammonium chloride (124.24 mM), yeast extract (0.46 g/L), urea (333 mM), and nickel chloride (0.01 mM), and the pH was 8.75. After the calcareous sand was treated with the optimal stimulation scheme, the urease activity was 6.1891 mM urea/min, the calcium carbonate production was 8.40%, and the UCS was 770 kPa, which constituted increases of 71.41%, 35.40%, and 83.33%, respectively, compared with the initial scheme. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses showed that calcium carbonate crystals were formed between the particles of the calcareous sand after the reaction, and the calcium carbonate crystals were mainly calcite. Urease-producing microorganisms became the dominant species in calcareous sand after treatment. This study showed that biostimulation-induced mineralization is feasible for reinforcing calcareous sand.

New Stratigraphical and Sedimentological Data on the Lower Cretaceous Rocks in Section Kalotina, Western Bulgaria

Biostratigraphic, microfacies and C–O isotope data from the lowermost Cretaceous deposits in section Kalotina reveal the development of a shallow carbonate platform (Slivnitsa Formation) in a photozoan mode under moderate to high-energy conditions during the Berriasian. Around the Berriasian/Valanginian boundary the carbonate production switched to a heterozoan-type suggesting a biological crisis. After a subaerial exposure in the earliest Valanginian and subsequent karst formation the platform was drowned during the latest Valanginian. Deposition of carbonate-argillaceous sediments (Salash Formation) occurred in a deeper, open-marine environment under mesotrophic to eutrophic, low-energy conditions with periodical formation of crinoid-rich packstones probably by mass gravity flows. Limestone samples from the Slivnitsa Formation yield higher δ13C values compared to coeval open-marine deposits which can be explained by an elevated amount of aragonite in the photozoan carbonate production and an enrichment in δ13C of the shallow platform waters due to high levels of photosynthesis. The most depleted δ13C value in the uppermost part of the unit most likely reflects a change from oligotrophic to mesotrophic conditions. The C-isotope signatures in limestones of the Salash Formation indicate correspondence to the third, smooth decrease phase in the δ13C record of the global Weissert Event (latest Valanginian and Early Hauterivian) where values tend to recover to pre-excursion values.

Experimental study on the calcium carbonate production rates and crystal size of EICP under multi-factor coupling

The production and microstructure of calcium carbonate are the fundamental indicators to evaluate the effectiveness of Enzyme-induced Carbonate Precipitation (EICP). Soybean urease is extracted, and the urease activity is controlled by the soybean powder concentration in this study. The urease reacts with the cementation solution with different concentrations of urea and calcium ions at different temperatures to determine the calcium carbonate production rates (RCC). The crystal sizes of calcium carbonate (SCC) are investigated by scanning electron microscopy (SEM) and image processing method. The RCC increase and subsequently decrease with increasing calcium ion concentration and peak at 0.75 M. A lower urea concentration is more favourable to the formation of CaCO3. Increased urease activity and temperature will lead to an increased RCC and SCC. Some crystals appear as capsules when the temperature goes up. The SCC decreases slightly with increasing calcium ion concentration under low urease activity and increases under high urease activity. The SCC increases first and subsequently decreases with increasing urea concentration under high urease activity, while the effect of urea concentration under low urease activity is not significant. XRD test results show that the calcium carbonate produced in this study is dominated by calcite crystals. The study provides additional data, a useful base to move forward toward a better understanding of the method of stabilization and its applications, for example, the treatment of different soils.

Carbonate platform architecture and carbon isotope stratigraphy from the neoproterozoic Narji limestone formation, Kurnool Group, India: Decoding clues of relative sea level fluctuations

From a detail process-based facies and facies association analysis in a spatio-temporal framework, a rimmed shelf platform geometry is proposed for the Neoproterozoic Narji Limestone Formation, Kurnool Group, India. Ten carbonate facies types were delineated and clubbed under seven facies associations belonging to four different paleogeographic settings viz. Forereef (intertidal to shallow subtidal and shallow to deep subtidal), peritidal reef and back-reef lagoon. Whereas crinkly microbial laminites with subordinate domal stromatolites constitute the reef part, the fore slope deposition in the platform largely remained tide-and storm-dominated. Grey to black colored pyrite bearing bedded limestone-shale alternation without any current or wave imprint represents the back-reef lagoon deposition. A high carbonate saturation and productivity in the Narji inner and mid shelf is suggested from an overall dominance of microalgal laminite and microdigitate stromatolites over columnar stromatolites. From documentation of decimeter-to meter-thick shallowing-upward depositional hemicycles, embedded within an overall aggradational Narji lithosuccession, a combined control of sea level and carbonate productivity is inferred in course of Narji sedimentation. A short-duration medium-to large-scale rise in the base level led to the aggradation in shallow water rim of the Narji platform margin; interruption of this overall motif by short thickening- and shallowing-upward progradational hemicycles bear testimony for higher productivity in the Narji mid-to inner shelf areas. The present study intends to correlate shallowing-upward hemicycles with keep-up to catch-up depositional cycles with signature of apparent sea level fall. The control of relative base level variation in Narji depositional history is strengthened with multiple signatures including secular δ13C composition, total organic carbon (TOC) content and siliciclastic content documented from the entire Narji litho-succession.

A Biomass‐Ligand‐Based Ru(III) Complex as a Catalyst for Cycloaddition of CO2 and Epoxides to Cyclic Carbonates and a Study of the Mechanism

AbstractAiming highly efficient conversion of greenhouse gas CO2 to cyclic carbonates, a biomass Ru(III) Schiff base complex catalyst (SalRu) was constructed by employing a derivative of Lignin degradation (5‐aldehyde vanillin). The SalRu catalyst had a remarkable conversion for epoxides into corresponding cyclic carbonates even at atmospheric pressure of CO2 without the presence of co‐catalyst. As the condition at 120 °C and 2 MPa CO2 the conversion reached to 94 % with selectivity at 99 % after 8 h. 32 % cyclic carbonate production was obtained even under 0.2 MPa CO2 pressure. The epoxide activation and ring opening, CO2 insertion and cyclic carbonate formation were illuminated explicitly through the of characteristic absorption peaks changing, which further providing direct and visual evidence for the mechanism proposing. This study has important theoretical significance for the comprehensive utilization of environmental pollutants and energy.

More gaps than record! A new look at the Pliensbachian/Toarcian boundary event guided by coupled chemo-sequence stratigraphy

The Pliensbachian/Toarcian boundary (Pl/To) event precedes by ca. 1 Myr the onset of the Toarcian Oceanic Anoxic Event. It corresponds to a second order mass extinction associated with an outstanding collapse of shallow marine ecosystems at global scale. Yet, our knowledge about its exact driver(s) and unfolding is relatively ambiguous due to the numerous hiatuses present in the sedimentary record during this critical time interval. In this study, an integrated carbon isotope chemostratigraphy and sequence stratigraphy approach is applied to two case studies (the upper Pliensbachian in South-East France and the Pliensbachian–Toarcian transition in Morocco) to demonstrate how the major changes in sea-level and sedimentation supply accompanying the Pl/To event led to the formation of ubiquitous, often cryptic hiatal surfaces in the sedimentary record. Hence, as a consequence of strongly progradational stacking pattern during the latest Pliensbachian related to a global sea-level lowstand associated with cold greenhouse climate, proximal settings were characterized by bypass and/or erosion, inducing an incomplete record of the Spinatum chronozone in localities situated in the outer part of sedimentary basins. In the earliest Toarcian, the collapse of the neritic carbonate factory led to a halt of carbonate mud export into the basin, resulting in sediment starvation in most basins characterized by a carbonate-dominated sedimentation regime before the environmental perturbation. Only localities where vigorous siliciclastic sediment supply took over are likely to have a more complete sedimentary record of the immediate aftermath of the carbonate production collapse. This combination of causes explains the ubiquitous incompleteness of the record of the Pliensbachian/Toarcian transition in numerous European localities where the bulk of our current understanding about the Pl/To event derives from. A comparison between the two known most expanded and complete records of the Pliensbachian–Toarcian transition of the Llanbedr (Mochras Farm) core in Wales and Bou Oumardoul n'Imazighn section in Morocco shows that the onset of the environmental perturbations is associated with a positive carbon isotope excursion spanning the Pliensbachian/Toarcian boundary. This is followed by a negative carbon isotope excursion during the earliest Toarcian that coincides with the global collapse of neritic carbonate factory and an ample sea-level fall.

How reefs drown: A case study from the Northwest Hawaiian Islands

Thousands of deeply submerged seamounts are scattered across ocean basins, many capped by thick successions of reef carbonates accumulated over millions of years prior to island drowning. How conditions sustaining shallow-water reef development at these sites deteriorated is often unclear but could lend insights into the processes that put stress on modern reef communities. Here the authors examine reef drowning in the Northwest Hawaiian Islands, brought on by low rates of carbonate accretion that often occur at mid-latitude (> 30) locations. New strontium-isotope stratigraphy from shallow water carbonates sampled from a 499 m-long boring through Midway Atoll suggest limited accumulation has occurred at the site since the early-Miocene (~ 16 Ma). The offshore morphology of Midway indicates carbonate production has often been outpaced by wave erosion during the Pleistocene, shifting the island’s centre ~ 3 km to the south-east in the prevailing wave direction and increasing its circularity. Strong wave action and slow reef accretion may also explain development of extensive reef flats on Midway and nearby islands. Similar features are shared with some other carbonate islands at mid-latitudes but are not typical of Central Pacific atolls, more generally, or guyots. Abrupt sea-level rise may therefore provide a more plausible mechanism for atoll/guyot drowning in the geologic past than poor environmental conditions for carbonate accretion as has previously been invoked.

Geo‐ecological functions provided by coral reef fishes vary among regions and impact reef carbonate cycling regimes

AbstractCoral reef fishes perform essential and well‐documented ecological functions on reefs, but also contribute important geo‐ecological functions, which influence reef carbonate cycling regimes. These functions include reef framework modification (through bioerosion and breakage), and the production, reworking, and transport of reefal sediments. To explore how these functions vary across reefs and regions, we compiled a dataset of available taxa‐specific function rates and applied these to fish census data from sites in the Pacific Ocean (PO), Indian Ocean (IO), and Greater Caribbean (GC), each region displaying a gradient in fish biomass. The highest overall function rates occur at the highest fish biomass sites in the PO (Kingman Reef) and IO (Chagos Archipelago), where bioerosion dominates framework modification and sediment generation (up to 7 kg m−2 year−1). At the lowest biomass PO and IO sites, framework modification and sediment generation are driven mainly by breakage and occur at lower rates (~2 kg m−2 year−1). Sediment reworking rates are high across all PO and IO sites (~1–5 kg m−2 year−1) and higher than other function rates at low biomass sites. Geo‐ecological function rates are generally low across the GC sites, despite total fish biomass being comparable to, or even exceeding, some PO and IO sites, with sediment reworking (up to ~1 kg m−2 year−1) being the dominant function. These site‐level differences partly reflect total fish biomass, but fish assemblage size structure and species identity are critical, with a few fish families (and species) underpinning the highest function rates and regulating the “health” of the fish‐driven carbonate cycling regime. Reefs with high fish‐driven framework modification, sediment production and reworking rates define one end of this spectrum, while at lower biomass sites little new sediment is produced and sediment reworking dominates. While additional species‐level rate data are urgently needed to better constrain function rates, these transitions align with ideas about the progressive shutdown of carbonate production regimes on ecologically perturbed reefs, with important implications for reef‐building, shoreline sediment supply, and sediment carbon and nutrient cycling.

Acidification impacts and acclimation potential of Caribbean benthic foraminifera assemblages in naturally discharging low-pH water

Abstract. Ocean acidification (OA) is expected to negatively affect many ecologically important organisms. Here we report the response of Caribbean benthic foraminiferal assemblages to naturally discharging low-pH waters with a composition similar to that expected for the end of the 21st century. At low pH ∼ 7.8 and low saturation state with respect to calcite (Ωcalcite < 4), the relative abundance of hyaline, agglutinated, and symbiont-bearing species increased, indicating higher resistance to potential carbonate chemistry changes. Diversity and other taxonomical metrics (i.e., richness, abundance, and evenness) declined steeply with decreasing pH despite exposure of this ecosystem to low-pH conditions for millennia, suggesting that tropical foraminiferal communities will be negatively impacted under acidification scenarios SSP3-7.0 (Shared Socioeconomic Pathways) and SSP5-8.5. The species Archaias angulatus, a major contributor to sediment production in the Caribbean, was able to calcify at more extreme conditions (7.1 pH) than those projected for the late 21st century, but the calcified tests had a lower average density than those exposed to higher-pH conditions (7.96), indicating that reef foraminiferal carbonate production might decrease this century. Smaller foraminifera were particularly sensitive to low pH, and our results demonstrate their potential use to monitor OA conditions.

Highly Exposed NH2 Edge on Fragmented g-C3 N4 Framework with Integrated Molybdenum Atoms for Catalytic CO2 Cycloaddition: DFT and Techno-Economic Assessment.

This study focuses on the applicability of single-atom Mo-doped graphitic carbon nitride (GCN) nanosheets which are specifically engineered with high surface area (exfoliated GCN), NH2 rich edges, and maximum utilization of isolated atomic Mo for propylene carbonate (PC) production through CO2 cycloaddition of propylene oxide (PO). Various operational parameters are optimized, for example, temperature (130°C), pressure (20bar), catalyst (Mo2 GCN), and catalyst mass (0.1g). Under optimal conditions, 2% Mo-doped GCN (Mo2 GCN) has the highest catalytic performance, especially the turnover frequency (TOF) obtained, 36.4 h-1 is higher than most reported studies. DFT simulations prove the catalytic performance of Mo2 GCN significantly decreases the activation energy barrier for PO ring-opening from 50-60 to 4.903kcal mol-1 . Coexistence of Lewis acid/base group improves the CO2 cycloaddition performance by the formation of coordination bond between electron-deficient Mo atom with O atom of PO, while NH2 surface group disrupts the stability of CO2 bond by donating electrons into its low-level empty orbital. Steady-state process simulation of the industrial-scale consumes 4.4 ton h-1 of CO2 with PC production of 10.2 ton h-1 . Techno-economic assessment profit from Mo2 GCN is estimated to be 60.39 million USD year-1 at a catalyst loss rate of 0.01wt% h-1 .

Process simulation for technical and economic evaluation of acrolein and glycerol carbonate production from glycerol

The objective of this work is the technical and economic evaluation of acrolein and glycerol carbonate production from glycerol, byproduct of biodiesel production. The processes were simulated in Aspen HYSYS® v8.8 and the capital and production costs were estimated. Among the two analyzed processes, only glycerol carbonate production was economically viable in the base scenario, due to the high reactivity of the selected catalyst and the simplicity of the reaction and separation steps. In addition to requiring a more complex separation system, the high degree of dilution of the inlet stream of the acrolein production process entails high costs for some equipment, as well as significant expenditure on utilities and effluent disposal. Such characteristics raise both the total investment and the production cost to a degree which makes the process economically unfeasible. However, it was shown that crude glycerol processing and further reaction development could make it also possible.

Structure-from-motion photogrammetry demonstrates variability in coral growth within colonies and across habitats.

Coral growth is an important metric of coral health and underpins reef-scale functional attributes such as structural complexity and calcium carbonate production. There persists, however, a paucity of growth data for most reef-building regions, especially for coral species whose skeletal architecture prevents the use of traditional methods such as coring and Alizarin staining. We used structure-from-motion photogrammetry to quantify a range of colony-scale growth metrics for six coral species in the Mexican Caribbean and present a newly developed workflow to measure colony volume change over time. Our results provide the first growth metrics for two species that are now major space occupiers on Caribbean reefs, Agaricia agaricites and Agaricia tenuifolia. We also document higher linear extension, volume increase and calcification rates within back reef compared to fore reef environments for four other common species: Orbicella faveolata, Porites astreoides, Siderastrea siderea and Pseudodiploria strigosa. Linear extension rates in our study were lower than those obtained via computed tomography (CT) scans of coral cores from the same sites, as the photogrammetry method averages growth in all dimensions, while the CT method depicts growth only along the main growth axis (upwards). The comparison of direct volume change versus potential volume increase calculated from linear extension emphasizes the importance of assessing whole colony growth to improve calcification estimates. The method presented here provides an approach that can generate accurate calcification estimates alongside a range of other whole-colony growth metrics in a non-invasive way.

Low net carbonate accretion characterizes Florida’s coral reef

Coral reef habitat is created when calcium carbonate production by calcifiers exceeds removal by physical and biological erosion. Carbonate budget surveys provide a means of quantifying the framework-altering actions of diverse assemblages of marine species to determine net carbonate production, a single metric that encapsulates reef habitat persistence. In this study, carbonate budgets were calculated for 723 sites across the Florida Reef Tract (FRT) using benthic cover and parrotfish demographic data from NOAA’s National Coral Reef Monitoring Program, as well as high-resolution LiDAR topobathymetry. Results highlight the erosional state of the majority of the study sites, with a trend towards more vulnerable habitat in the northern FRT, especially in the Southeast Florida region (− 0.51 kg CaCO3 m−2 year−1), which is in close proximity to urban centers. Detailed comparison of reef types reveals that mid-channel reefs in the Florida Keys have the highest net carbonate production (0.84 kg CaCO3 m−2 year−1) and indicates that these reefs may be hold-outs for reef development throughout the region. This study reports that Florida reefs, specifically their physical structure, are in a net erosional state. As these reefs lose structure, the ecosystem services they provide will be diminished, signifying the importance of increased protections and management efforts to offset these trends.

Uppermost Devonian–Lower Carboniferous conodonts from the Indert Formation in the Shine Jinst area, South Mongolia

In southwestern Mongolia, conodonts from the Indert Formation at its type locality in Shine Jinst were investigated to improve regional and global correlation of the uppermost Devonian–lowermost Carboniferous. The abundance and diversity of the conodont fauna is quite low in general, whereas representatives of Siphonodella, Protognathodus, Pseudopolygnathus, Polygnathus and Bispathodus have been collected from the Indert-Uul section. Five conodont biointervals, from the Bi. costatus-Pr. kockeli Interregnum (ckI) to the Siphonodella sandbergi Zone, could be recognized from the top Heermorit Member and the lower part of the Shombon Member, while the middle and upper parts of the Shombon Member cannot be zoned based on the conodonts. Absence of index fossils Si. sulcata, Pr. kuehni and Pr. kockeli hampered precise recognition of the Devonian–Carboniferous boundary (DCB) at Indert-Uul, but this transition is well delineated by typical uppermost Famennian and Tournaisian conodont assemblages. The DCB is tentatively placed at the base of the Shombon Member, consistent with the lithological boundary and the resuming of carbonate production during the DCB transitional interval.

An equation for deriving spatial variations in carbonate production rates from sediment deposition rates and dilution: Application to Santa Maria Island, Azores

ABSTRACT Knowledge of how carbonates are produced on shelves is needed for working out how these “carbonate factories” generate stratigraphy by providing particles for potential export or local deposition. Production rates can be derived straightforwardly in low-energy environments from one-dimensional analysis (age–depth variations) but rates are less easily derived for high-energy hydrodynamical environments where particles are transported away from their sites of production. This particularly affects knowledge of spatial variations in production rates, needed for working out controlling influences of light, hydrodynamics, and nutrient availability. We show here that, if a non-carbonate component of the sediment, such as terrigenous particles arising from coastal and subaerial erosion, is conserved and thus acts as a tracer, rates of carbonate production can in principle be derived from carbonate content data, if sediment transport fluxes can also be constrained. In the equation developed here, the spatial rate of change of carbonate content is caused by dilution of the terrigenous component by the newly produced carbonate and depends on the sediment transport flux. We investigate this idea using data from Santa Maria Island, Azores, an inactive volcanic island in a temperate environment. Geochemical, X-ray diffraction (XRD), and X-ray fluorescence (XRF) data of surface–sediment grab samples indicate nearly simple mixing trends between two components (volcanic rock and marine carbonate), as needed for our simple dilution-based equation to apply. High-resolution boomer seismic data reveal thicker (> 1 m) deposits in the mid- to outer shelf of the island, which we interpret as having been emplaced during the Holocene. These effectively provide time-averaged depositional fluxes and, assuming conservation of mass, can be used to constrain transport fluxes. The derived equation is used to predict the observed deposit thicknesses into the mid-shelf alongside coincident increasing carbonate percentages. The thicknesses are replicated only if carbonate production rates increase with depth and distance away from the coastline into the mid-shelf, quantifying the variation of production of such a nearshore environment for the first time. We speculate that mollusks dominating the production have a preference for sand that is less frequently or strongly agitated by waves, although nutrient availability from occasional upwelling may also regulate growth to create this trend.

The Tethyan and Tyrrhenian margin record of the Central Apennines: a guide with insights from stratigraphy, tectonics, and hydrogeology

This guide is a 5-day geotraverse across the Central Apennines, which expose the inherited Meso-Cenozoic sedimentary successions and tectonic architecture of the Apennine Tethyan passive margin. This structure was progressively involved into orogenic and post-orogenic tectonics, related to the Tyrrhenian back-arc dynamics. To show the different margin dynamics, we present: 1) sedimentologic and stratigraphic aspects, 2) relations with Neogene compressive and Quaternary extensional structures and 3) a hydrogeological case-study. The trip starts north of Rome, where Quaternary deposits at the transition from marine to continental deposition, including travertines, record the evolution of the Tyrrhenian passive margin. The excursion then moves to the Mesozoic platform margins of the Latium-Abruzzi and Apulia carbonate platforms, where perfectly preserved Cretaceous to Neogene successions occur. The Maiella mountain and Gran Sasso range testify for carbonate production changes, as recorded in facies associations and isotope geochemistry records, related to global climate shifts and regional tectonics. A focus on the hydrogeologic dynamics of the Gran Sasso aquifer is also offered in relation to the current climate change. This guide is the result of a workshop of GeoSed, the Italian Association for Sedimentary Geology, and it also aims at providing a scientific base for geo-touristic explorers.