SSP4.2 | (Paleo-)environmental reconstructions using biomineralized carbonates: From the early Archaean to the present
EDI
(Paleo-)environmental reconstructions using biomineralized carbonates: From the early Archaean to the present
Co-organized by BG5/CL1
Convener: Niels de WinterECSECS | Co-conveners: Johan VellekoopECSECS, Mónica Sánchez-Román, Alexandra RodlerECSECS, Sebastian ViehmannECSECS
Orals
| Tue, 25 Apr, 14:00–15:45 (CEST)
 
Room -2.31
Posters on site
| Attendance Tue, 25 Apr, 10:45–12:30 (CEST)
 
Hall X3
Posters virtual
| Attendance Tue, 25 Apr, 10:45–12:30 (CEST)
 
vHall SSP/GM
Orals |
Tue, 14:00
Tue, 10:45
Tue, 10:45
Carbonate (bio)minerals have been essential indicators for life throughout most of Earth’s history and are important archives for past climate and environmental change. Geochemical investigations are crucial for understanding (I) the paleobiology of carbonate biomineralizers, (II) the evolution of microbial habitats, and (III) complementary changes in the atmosphere-hydrosphere systems through time. With this session, we encourage contributions from sedimentology, geochemistry and (geo)biology that utilize carbonate (bio)minerals (e.g., invertebrate shells, foraminifera, microbialites and stromatolites) with the aim to reconstruct paleo-environments, seasonality, seawater chemistry and paleobiology in a wide range of modern to deep time settings, including critical intervals of environmental and climate change. This includes studies targeting original skeletal carbonate preservation and diagenetic alteration and theoretical or experimental studies of trace element partitioning and isotope fractionation in carbonate (bio)minerals.

Orals: Tue, 25 Apr | Room -2.31

Chairpersons: Niels de Winter, Johan Vellekoop
14:00–14:05
14:05–14:15
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EGU23-15203
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ECS
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Highlight
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On-site presentation
Alexander J. Clark, Ismael Torres Romero, Madalina Jaggi, Stefano M. Bernasconi, and Heather Stoll

Carbonate clumped isotope thermometry, based on the temperature-dependence of clumping of 13C and 18O in the carbonate molecule (Δ47) is a promising tool for paleoclimate reconstruction. In the last few years many discrepancies among Δ47-temperature calibrations have been resolved across the range of relevant paleoclimate temperatures (Meinicke et al., 2020; Anderson et al., 2021). However, there might be other environmental effects on biogenic carbonates from parameters such as the pCO2 and growth rates of the organisms that are still unresolved. We provide a new assessment of the temperature dependence of clumped isotopes in laboratory grown biogenic carbonate at well-constrained experimental conditions, with results from three species of coccolithophores across a growth temperature range of 6-27°C. The three cultured species cover a range of growth rates, growth conditions and species-specific carbon and oxygen vital effects. Because variations in pCO2 and media carbon chemistry are known to trigger vital effects in carbon and oxygen isotopes in coccoliths, we decoupled the temperature solubility effect on CO2 by manipulating culture CO2 independently. Three pCO2 levels at reduced, present day and elevated levels; 200, 400 and 1000 ppm respectively, were kept constant for at least two different temperatures through a continuous culturing set-up. Our new multi-parameter comparison, using updated standardization approaches, provides a critical test of previous conclusions (Katz et al., 2017) that coccolithophore clumped isotopes show little to no vital effects and are close to abiotic equilibrium. Thus, we have performed the first calibration of coccolith calcite and clumped isotopes combining different temperature and pCO2 conditions.

References:

Anderson, N. T., J. R. Kelson, S. Kele, M. Daëron, M. Bonifacie, J. Horita, T. J. Mackey, et al. 2021. "A Unified Clumped Isotope Thermometer Calibration (0.5–1,100°C) Using Carbonate‐Based Standardization." Geophysical Research Letters 48 (7).

Katz, A., M. Bonifacie, M. Hermoso, P. Cartigny, D. Calmels. 2017. “Laboratory-grown coccoliths exhibit no vital effect in clumped isotope (Δ47) composition on a range of geologically relevant temperatures.” Geochimica et Cosmochimica Acta 208: 335-353.

Meinicke, N., S.L. Ho, B. Hannisdal, D. Nürnberg, A. Tripati, R. Schiebel, and A.N. Meckler. 2020. "A robust calibration of the clumped isotopes to temperature relationship for foraminifers." Geochimica et Cosmochimica Acta 270: 160-183.

How to cite: Clark, A. J., Torres Romero, I., Jaggi, M., Bernasconi, S. M., and Stoll, H.: A new clumped isotope-temperature calibration of cultured coccoliths under different pCO2 and temperature conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15203, https://doi.org/10.5194/egusphere-egu23-15203, 2023.

14:15–14:20
14:20–14:30
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EGU23-5544
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ECS
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On-site presentation
Goulwen Le Guevel, Fabrice Minoletti, Carla Geisen, and Michael Hermoso

The major climatic forcing parameters on Earth climate are temperature and the atmospheric concentrations of CO2. Even if their evolutions covaried to the first-order, the geological record show periods with non-linear evolution between those two parameters. Such delinking requires accurate paleoclimate reconstructions with implications for the modelling studies of our future climate.

pCO2 and Sea Surface Temperature (SST) reconstructions are usually quantified using proxies relying on both the organic matter produced by coccolithophores (UK37’ index and δ13Calkenones) and calcite of foraminiferal tests (δ11B, δ18O, Mg/Ca). These proxies have been very useful for a variety of paleoclimatic advances, yet present unresolved and potentially important biases. As an example, alkenone carbon isotopes are not able to register low to moderate pCO2 levels (Badger et al., 2019). This is notoriously a major issue for paleoclimate reconstructions of the last 6 My (Plio-Pleistocene period).

Our approach is to use a unique archive – the coccoliths – for determination of coeval SST and pCO2. Coccoliths are small calcite plates produced by unicellular photosynthetic algae called coccolithophores. They are a very promising substrate to analyse for paleoclimate studies because they calcify in the uppermost water column and because their isotopic ratios are sensitive to both photosynthesis and calcification (Hermoso et al. 2020). Therefore, these isotopic ratios provide physiological and metabolic information about coccolithophores of the past. In order to infer paleoclimates from the sedimentary archives, we have to deconvolve the isotopic biological imprint (vital effect) from the environment signal. For the evaluation of the vital effects, we have undertaken a large-scaled culture experiments with various strains of coccolithophore grown under various CO2 concentrations and pH (Le Guevel et al. in prep). Even if we have managed culture until 1400ppm and 7.55 unit of pH, we were particularly interested in low pCO2 and high pH conditions because the bibliography is lacking of vital effect for Plio-Pleistocène applications. All the selected strains produce coccoliths within the size range of the one we find predominantly in the marine sediments throughout geological times.

We document a large decrease of the carbon differential vital effect with the CO2 concentration increase between Gephyrocapsa oceanica and Coccolithus braarudii. This is consistent with previous studies but the absolute values are slightly different and we provide a more precise dataset at low to moderate pCO2 than the previous ones (Rickaby et al., 2010; Hermoso et al., 2016). We propose the first study of the oxygen and carbon vital effect of the Helicosphaera carteri group with combined CO2/pH changes. Taken together, the culture data and measurements of the isotopic composition of the calcite biominerals allows better paleoreconstructions of SST and aqueous CO2.

How to cite: Le Guevel, G., Minoletti, F., Geisen, C., and Hermoso, M.: Developing a robust biogeochemical framework of the coccolith vital effects for more reliable paleoclimatic reconstructions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5544, https://doi.org/10.5194/egusphere-egu23-5544, 2023.

14:30–14:35
14:35–14:45
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EGU23-10717
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ECS
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Virtual presentation
Clément G.L. Pollier, Caroline H. Koschik, Brooke E. Vitek, Zhenghui Wu, Erica P. Suosaari, R. Pamela Reid, and Amanda M. Oehlert

Organo-sedimentary structures built by benthic microbial communities, known as microbialites, dominated the fossil record for the first 3 billion years of Earth’s history. Various microbial metabolisms contribute to microbialite lithification, each of which can be based on biogeochemical cycling of elements capable of supporting life. Arsenic (As), a common element on the surface of Precambrian Earth, has been proposed to have supported the development of early life associated with the construction of primitive microbial carbonates. These As-based metabolisms have left evidence of their existence within the 2.7 Ga old Tumbiana stromatolites, showing the potential of this metalloid to serve as an archive of the dynamic interplay between microbes, minerals, and their environment of deposition throughout Earth’s history. However, significant changes in the geochemical composition of microbialites likely occur during early taphonomic modification and later diagenetic alteration. Therefore, establishing the mechanisms driving the arsenic geochemistry of ancient microbialites can be challenging.

Motivated by these challenges, our objective was to evaluate the mechanisms controlling the initial incorporation of arsenic into actively accreting microbialites, as well as the preservation of the [As] signal during early taphonomic alteration of the structure. Hamelin Pool (Western Australia) is one of the few modern systems that host As-based metabolisms in the microbial communities involved in microbialite accretion. Conventional terminology recognizes four types of microbial mats that produce recognizable internal microfabrics in Hamelin Pool microbialites: pustular, smooth, colloform, and transitional mat types. Over time, these initial microfabrics all follow a similar evolution subdivided into two successive stages: (1) precipitation of micrite along laminations and around clots and; (2) precipitation of aragonitic marine cement. Therefore, Hamelin Pool microbialite fabrics provide a unique and step-wise window into the processes that form ancient microfabrics, particularly highlighting the importance of their early taphonomic evolution in the fate of the As biosignal originally incorporated during initial accretion of the structure.

Based on microbialites collected from Hamelin Pool that have been characterized petrographically, we evaluated the evolution of [As] recorded in the Hamelin Pool microbialites at all stages of deposition and early taphonomic modifications. Results were interpreted in relation to the distinct microbial mats and their metabolisms, as well as the physicochemical and geological variability of the depositional environment. To accomplish this, we conducted a sequential leaching experiment to chemically isolate the organic matter and carbonate fractions, and measured As concentrations on a triple-quadrupole inductively coupled mass spectrometer (Agilent 8900 ICP-QQQ). Preliminary results show that elevated As concentrations are initially incorporated into microbial organic matter before being transferred to the carbonate fraction through successive stages of early taphonomic alteration. Because the carbonate fraction is diagenetically more resistant than the organic matter, this discovery could have major implications for the preservation of geochemical biosignatures in the geological record of microbialites. Our results serve as a first step towards improving the utility of [As] as an indicator of biogenicity in the fossil record of early Earth and, possibly, other planets such as Mars.

How to cite: Pollier, C. G. L., Koschik, C. H., Vitek, B. E., Wu, Z., Suosaari, E. P., Reid, R. P., and Oehlert, A. M.: The fate of Arsenic during early microbialite taphonomy: Implications for chemical biosignature preservation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10717, https://doi.org/10.5194/egusphere-egu23-10717, 2023.

14:45–14:55
14:55–15:05
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EGU23-6697
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ECS
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On-site presentation
Isabella Leonhard, Konstantina Agiadi, Rafal Nawrot, Emilia Jarochowska, and Martin Zuschin

Climate warming is expected to lead to a reduction in the body size of marine organisms, a trend already observed in commercial fishes, but the effects of temperature rise on size distribution in exploited populations are difficult to separate from the impact of overfishing and other anthropogenic stressors. We aim to test the hypothesis that fish body sizes, as well as growth rates changed during the late Holocene and Anthropocene in the northern Adriatic Sea due to environmental perturbations caused by climate warming. We perform sclerochronological analysis on modern otoliths from fish sampled alive, as well as radiocarbon-dated fossil otoliths of non-commercial, demersal gobies (Gobius niger Linnaeus, 1758) sampled from a sediment core taken off Piran (Slovenia) to quantify changes in body size and growth parameters throughout the Holocene. Otoliths are the aragonitic structures of the fish’ inner ear with species-specific morphology, and thanks to their incremental growth, they serve as unique environmental and life-history archive. Moreover, otolith size correlates with fish size. We use otoliths cut in half to perform both sclerochronology and radiocarbon dating, obtaining a high-resolution time series of changes in fish body size, growth dynamics and life history parameters. We employ backscatter electron (BSE) imaging and electron probe microanalysis (EPMA) to identify body sizes and growth dynamics, as well as to correlate their growth increments with climatic and other environmental parameters. The reconstructed changes in body size and growth rates of very common, non-commercial fish species over the last 7.000 years, can serve as an ecological baseline for evaluating the magnitude of ongoing temperature rise and future shifts in fish populations in response to global warming.

How to cite: Leonhard, I., Agiadi, K., Nawrot, R., Jarochowska, E., and Zuschin, M.: Reconstructing Holocene body size changes of Adriatic gobies using radiocarbon dating and sclerochronological analyses of modern and fossil otoliths, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6697, https://doi.org/10.5194/egusphere-egu23-6697, 2023.

15:05–15:10
15:10–15:20
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EGU23-12307
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ECS
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On-site presentation
Pietro Bazzicalupo, Valentina Alice Bracchi, Andrea Giulia Varzi, Luca Fallati, Alessandra Savini, Antonietta Rosso, Rossana Sanfilippo, Adriano Guido, Mara Cipriani, and Daniela Maria Basso

Crustose coralline algae (CCA) form Coralligenous build-ups, which are ranked among the most important ecosystems in the Mediterranean shelf. Their skeletal framework hosts a variety of epi- and infaunal communities, which compete for space, contributing to the reef growth, or weaken the structure throughout bio-erosive activities. Investigating the relationship between the algal framework and these hosted communities is of extreme importance for ecological and palaeoecological purposes and monitoring goals. 

In this frame, the Italian project “CRESCIBLUREEF - Grown in the blue: new technologies for the knowledge and conservation of the Mediterranean reefs”, is aimed at investigating coralligenous reefs present in the  area off the Marzamemi village (South-East Sicily). 

Two build-ups have been collected: the first one at 37 m depth, from an area rich in coralligenous cover, and the second one at 36 m depth, from a submarine channel with sparsely distributed build-ups. We present here two new investigative techniques, so far seldom applied for the characterization of the Coralligenous. The first approach involved the quantification of the surficial cover, with the use of an image analysis software, both before and after the removal of their ephemeral canopy of unmineralized organisms.These models were then analysed using Object-Based Image Analysis (OBIA) algorithms that allowed the quantification of the surficial cover. Moreover, the analysis allowed the identification and categorisation of the organisms and materials on the external part of the build-ups, confirming the primary role of CCA as the major component of the samples. Afterwards, a Computed-Tomography (CT) scan was used - for the first time with Coralligenous - to reconstruct the inner structure of the build-ups and, together with radiocarbon dating, to infer the build-ups age and growth rate. CT analysis divided the framework into four main categories based on their density (Low, Medium, High and Ultra High). The structure’s cavities, either primary or developed through taphonomic processes, have been measured as porosity. The overall highly-resolved analysis points to a complex and nonlinear growth of the build-ups. The understanding of the structural density, porosity, growth rate, and surficial cover of the build-ups is shedding some light on the Coralligenous inception and growth. 

How to cite: Bazzicalupo, P., Bracchi, V. A., Varzi, A. G., Fallati, L., Savini, A., Rosso, A., Sanfilippo, R., Guido, A., Cipriani, M., and Basso, D. M.: Novel investigative techniques on calcareous red algae build-ups: photogrammetry and CT-scan on Coralligenous from Marzamemi (Sicily), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12307, https://doi.org/10.5194/egusphere-egu23-12307, 2023.

15:20–15:25
15:25–15:35
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EGU23-274
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ECS
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On-site presentation
Sreevidya Edayiliam, Sijin Kumar Adukkam Veedu, and Nagender Nath Bejugam

To evaluate the preservation pattern of pteropods and their relationship with climatic and oceanographic history in the Laccadive Sea, a temporal variation analysis of pteropod abundance was done. For that, we employed preservation indices from calcite (Globigerina bulloides%, Globorotalia menardii abundance), as well as aragonite (e.g., total pteropod abundance, Limacina Dissolution Index (LDX), fragmentation ratio). To determine if pteropod shells have been preserved over time, we used estimated pteropod abundance. The pteropod preservation record displays excellent preservation during cold stadials, evidenced by the lower values of aragonite dissolution proxies than during the interglacials/interstadials, similar to the preservation records from other northern Indian Ocean cores evidenced by the lower values of aragonite dissolution proxies than during the interglacials/interstadials. The shallow aragonite compensation depth (ACD), weaker oxygen minimum zone (OMZ), and the lower southwest monsoon (SWM)-induced productivity are thought to be the cause of the basin-wide pteropod preservation events during the cold stadials (ACD). Additionally, during an intense northeast monsoon (NEM), the advection of cold, low-saline waters from the Bay of Bengal to the Laccadive Sea, as well as the intrusion of southern-sourced intermediate water ventilation, may have caused a deep vertical mixing of oxygen-rich surface waters, raised the pH of thermocline waters and deepened the ACD. However, the local fluctuations in the water mass properties, such as the increased productivity maxima, the intense OMZ, and shallow ACD, as well as changes in the aragonite, are responsible for the poor pteropod abundance, poor preservation and strong dissolution during the Holocene, Bølling-Allerød (B/A) and interstadial periods.

The calcification proxy indicates that the aragonite undersaturation and reduced calcification occurred during 19-16.5 kyr, preferably due to the depletion in the oceanic alkalinity caused by enhanced upwelling-induced carbonate ion exchange between the intermediate and deep water. In contrast, the preferential dissolution of smaller shells in the sediments (marked by increased average shell size and higher values of Limacina dissolution index (LDX) corresponds to strengthened OMZ and shallower ACD, pointing towards the post-depositional dissolution of aragonite shells. Therefore, the overall decrease of pteropod content of the deposits in the stadial/interstadials suggests a combination of monsoon-associated changes in water column properties, variability in aragonite saturation, intermediate water ventilation and sediment rate.

How to cite: Edayiliam, S., Adukkam Veedu, S. K., and Bejugam, N. N.: Late quaternary carbonate (pteropod) preservation in the Indian Ocean sediments: inferences on the paleoclimate and paleoceanography, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-274, https://doi.org/10.5194/egusphere-egu23-274, 2023.

15:35–15:40
15:40–15:45

Posters on site: Tue, 25 Apr, 10:45–12:30 | Hall X3

Chairpersons: Johan Vellekoop, Niels de Winter
X3.84
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EGU23-4915
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ECS
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Highlight
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Niels de Winter, Julia Tindall, Andy Johnson, Barbara Goudsmit, Nina Wichern, Fynn Huygen, Stijn Goolaerts, Frank Wesselingh, Philippe Claeys, and Martin Ziegler

Accurate projections of future climate scenarios require a detailed understanding of the behavior of Earth’s climate system under varying radiative forcing scenarios. The mid-Piacenzian Warm Period (mPWP; 3.3 – 3.0 Ma) was characterized by atmospheric CO2 concentrations comparable to present-day values (~400 ppmV), while global mean annual temperatures were roughly 2-3 degrees warmer compared to pre-industrial climate (Haywood et al., 2020). Seasonally resolved climate records from fossil bivalve shells offer a snapshot of short-term variability in temperature and salinity under the mild greenhouse conditions of the mPWP (Wichern et al., 2022).

In this study, we combine a large dataset of clumped isotope measurements incrementally sampled in fossil shells from the North Sea area during the mPWP with climate model simulations for the same time period using the PlioMIP model comparison framework. This combination of data and models allows us to test whether the climate models in PlioMIP can pick up the sub-annual scale variability in temperature and salinity (reconstructed via the oxygen isotope composition of the paleo-seawater). We show that, in contrast to continental reconstructions used in previous PlioMIP data-model comparisons (Tindall et al., 2022), our shallow marine data is reproduced well by PlioMIP models. On average, both model and data show considerably (4-5°C) warmer summer sea surface temperatures during the mPWP while winter temperatures remain relatively close to pre-industrial values. This suggests that the North Sea region can expect warming concentrated in the summer season in response to elevated atmospheric CO2 conditions.

References

Haywood, A. M., Tindall, J. C., Dowsett, H. J., Dolan, A. M., Foley, K. M., Hunter, S. J., Hill, D. J., Chan, W.-L., Abe-Ouchi, A., Stepanek, C., Lohmann, G., Chandan, D., Peltier, W. R., Tan, N., Contoux, C., Ramstein, G., Li, X., Zhang, Z., Guo, C., Nisancioglu, K. H., Zhang, Q., Li, Q., Kamae, Y., Chandler, M. A., Sohl, L. E., Otto-Bliesner, B. L., Feng, R., Brady, E. C., Von der Heydt, A. S., Baatsen, M. L. J., and Lunt, D. J.: A return to large-scale features of Pliocene climate: the Pliocene Model Intercomparison Project Phase 2, Climate of the Past, 2020.

Tindall, J. C., Haywood, A. M., Salzmann, U., Dolan, A. M., and Fletcher, T.: The warm winter paradox in the Pliocene northern high latitudes, Climate of the Past, 18, 1385–1405, https://doi.org/10.5194/cp-18-1385-2022, 2022.

Wichern, N. M. A., de Winter, N. J., Johnson, A. L. A., Goolaerts, S., Wesselingh, F., Hamers, M. F., Kaskes, P., Claeys, P., and Ziegler, M.: The fossil bivalve <em>Angulus benedeni benedeni</em>: a potential seasonally resolved stable isotope-based climate archive to investigate Pliocene temperatures in the southern North Sea basin, EGUsphere, 1–53, https://doi.org/10.5194/egusphere-2022-951, 2022.

How to cite: de Winter, N., Tindall, J., Johnson, A., Goudsmit, B., Wichern, N., Huygen, F., Goolaerts, S., Wesselingh, F., Claeys, P., and Ziegler, M.: A data-model comparison of shallow marine seasonality during the Mid-Pliocene, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4915, https://doi.org/10.5194/egusphere-egu23-4915, 2023.

X3.85
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EGU23-9157
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ECS
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Marie Pesnin, Thaler Caroline, Daëron Mathieu, Kadda Medjoubi, Nomade Sebastien, and Rollion-Bard Claire

Bryozoans are one of the most invasive phyla on Earth. Since their appearance in the Upper Ordovician period, a fair proportion of these colonial organisms have developed innovative adaptation strategies, like the ability to form a carbonate skeleton. Despite the fact that these reef builders can represent up to 80% of the carbonate production of some sedimentary formation, bryozoans have been poorly studied compared to other bio-carbonate archives. The diversity of bryozoan morphology is an impediment to their identification and their use for paleoenvironmental reconstruction. The morphology of the carbonate chambers (zoecium) varies not only from one species to another, but also as a function of physiological or environmental parameters. Moreover, depending on the species, bryozoan carbonate skeleton can be polycrystalline. The abundance of each carbonate polymorph can vary spatially within the colony, which has implications for the interpretation of the geochemical record. In order to retrieve useful paleoenvironmental information from this extensive record, we thus need to fill the gaps in our knowledge of bryozoan mineralization mechanisms.

In this contribution, we characterized the mineralogical and isotopic composition of different species of bryozoan living in the same microenvironments and identical species from different locations. Samples were collected from the Western Mediterranean (Marine station of Banyuls sur Mer, France) and North Atlantic (Marine station of Roscoff, France) coasts, where environmental parameters are continuously measured. Mineral characterization by XRD measurements were done on portions of each bryozoan colonies from base to the top and completed by 3D X-Ray diffraction imaging at a nanometric scale on a single zoecium. These mineralogical characterizations were matched with δ18O, δ13C analysis and clumped isotope (Δ47) measurements. Using environmental data (T, pH, S, δ18Ow and δ13CDIC) collected in situ, the measured isotopic signatures were compared to their respective expected values (assuming pseudo-equilibrium carbonate precipitation). This comparative work yields some unexpected discrepancies from the “equilibrium” line and between different species originated from the same site in both δ18O and δ13C compositions. Δ47measurements, performed on 4 selected species (Pentapora foliacea, Cellaria fistulosa, Sertella beaniana, Tubicellepora avicularis) revealed that the magnitude of apparent isotopic disequilibrium observed in bryozoan is not related to the mineralogical composition of the skeleton nor to the species but rather to the living environment of the organisms. Surprisingly only bryozoan originated from the Mediterranean Sea seems to precipitated their skeleton out of isotopic equilibrium for Δ47. These results permit to discuss the origin of this “isotopic vital effect”, its relation to environmental conditions, and the use of bryozoan as a new paleo-tracer.

Key words: Bryozoan – 3D X-Ray map - Clumped isotopes – Stable isotopes - Isotopic disequilibrium.

How to cite: Pesnin, M., Caroline, T., Mathieu, D., Medjoubi, K., Sebastien, N., and Claire, R.-B.: Mineralogical, elemental, stable and clumped isotope composition of modern bryozoan skeletons., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9157, https://doi.org/10.5194/egusphere-egu23-9157, 2023.

X3.86
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EGU23-12060
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Highlight
Thomas Felis, Miriam Pfeiffer, and Jessica Hargreaves and the SPP2299 Programme

Climate change, in particular the rise in tropical sea surface temperatures, is the greatest threat to coral reef ecosystems today and causes climatic extremes affecting the livelihood of tropical societies. Assessing how future warming will change coral reef ecosystems and tropical climate variability is therefore of extreme urgency. Ultra-high resolution (monthly, weekly) coral geochemistry provides a tool to understand the temporal response of corals and coral reefs to ongoing climate and environmental change, to reconstruct past tropical climate and environmental variability, and to use these data in conjunction with advanced statistical methods, earth system modelling and observed ecosystem responses for improved projections of future changes in tropical climate and coral reef ecosystems. The recently established Priority Programme “Tropical Climate Variability and Coral Reefs - A Past to Future Perspective on Current Rates of Change at Ultra-High Resolution” (SPP 2299, https://www.spp2299.tropicalclimatecorals.de/) of the German Research Foundation (DFG) aims to enhance our current understanding of tropical marine climate variability and its impact on coral reef ecosystems in a warming world, by quantifying climatic and environmental changes during both the ongoing warming and past warm periods on timescales relevant for society. The programme aims to provide an ultra-high resolution past to future perspective on current rates of change to project how tropical marine climate variability and coral reef ecosystems will change in a warming world. Information on the organisational structure and research topics of this collaborative programme, which involves ten universities and five research centres from all over Germany, will be provided.

How to cite: Felis, T., Pfeiffer, M., and Hargreaves, J. and the SPP2299 Programme: Tropical Climate Variability and Coral Reefs - A Past to Future Perspective on Current Rates of Change at Ultra-High Resolution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12060, https://doi.org/10.5194/egusphere-egu23-12060, 2023.

X3.87
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EGU23-16355
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ECS
Alba Gonzalez-Lanchas and Rosalind E.M. Rickaby

To understand how coccolithophore calcification rates evolved, it is critical to disentangle which environmental parameters controls the flow of energy from photosynthesis to calcification.

The values of coccolith vital effects, the offset of the isotopic composition of coccoliths from abiogenic calcite equilibrium, are not yet unilaterally understood. Models from observations in cultures indicate that such geochemical value is controlled, in some extent, by the changes in calcification intensity (McClelland et al., 2017). However, confirmation from observations in the natural environment remains scarce, up to date.

In order to explore the suitability of coccolith isotopical values to produce consistent estimations of calcification intensity, we analyze d13C values measured in size separated coccoliths from natural assemblages in core top records across different latitudes of the Atlantic Ocean. Micro separation of coccoliths and extraction from sediments are carried out with the application of the method by Minoletti et al. (2009) and serve to produce nearly monospecific size-separated coccolith fractions.

Our preliminary results allow investigation on the variance of size-separated coccolith vital effects together with independent estimations of PIC/POC production (Particulate Inorganic Carbon/Particulate Organic Carbon) and regional changes in environmental conditions trough the Atlantic Ocean.

References:

McClelland, H. L. O., Bruggeman, J., Hermoso, M., & Rickaby, R. E. M. (2017). The origin of carbon isotope vital effects in coccolith calcite. Nature communications, 8(1), 1-16.

Minoletti, F., Hermoso, M., & Gressier, V. (2009). Separation of sedimentary micron-sized particles for palaeoceanography and calcareous nannoplankton biogeochemistry. Nature protocols, 4(1), 14-24.

 

How to cite: Gonzalez-Lanchas, A. and Rickaby, R. E. M.: Evaluation of the effect of calcification intensity on the isotopical composition of coccolith calcite, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16355, https://doi.org/10.5194/egusphere-egu23-16355, 2023.

Posters virtual: Tue, 25 Apr, 10:45–12:30 | vHall SSP/GM

vSG.20
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EGU23-618
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ECS
Venu Gopal Kella, Amitaprajna Mallik, Devapriya Chattopadhyay, and Naveen Gandhi

Seagrasses are a vital part of the marine ecosystem, owing to their contribution to oceanic primary productivity and supporting highly diverse marine ecosystems. The fossil record of seagrasses is rare because of their poor preservation potential. Sedimentological and taphonomic indicators are generally used to identify the paleo seagrass habitat. The fossil record of seagrass-associated taxa such as foraminifera, corals, bryozoans, molluscs, and sirenians can also provide indirect evidence of this specific habitat. These constitute Indirect Paleo-Seagrass Indicators (IPSIs). The early Miocene (Burdigalian) fossil assemblage of Quilon limestone of Kerala, India, has been interpreted as a seagrass habitat based on the species association of gastropods, bryozoans, and foraminifera. This is the only reported seagrass ecosystem from West Indian Province (WIP). In our study, we attempt to develop a new multi-proxy approach using morphology, ecology, and geochemical signatures of seagrass-associated molluscs from the Quilon Formation and evaluate its potential to reconstruct a paleo-seagrass ecosystem.

Our sample consisted of ~2000 specimens of microbivalves representing nine families of bivalves. We also included previously reported 16 families of macrobivalves in our ecological analysis. The molluscan community of the Quilon Formation is dominated by families that are mobile (67%), infaunal (65%), and suspension feeders (78%) in comparison to other ecological guilds. The seagrass ecosystem, characterized by soft substratum and high suspension load, favors these ecological strategies. The high proportional abundance of Lucinidae bivalves (8.9%) in the assemblage agrees with the expectation of dominance of chemosymbionts in the seagrass meadows. The small body size (<10mm ) and low predation intensity (drilling frequency 0.06, repair scar frequency 0.04) reported from this community also match the expected pattern of a seagrass ecosystem serving as a nursery.

We analyzed molluscan shells from Quilon limestone for stable isotope ratios. We also supplemented this data with published data of present and past seagrass-associated molluscs. Using this data, we evaluated the influence of ecological variables in shaping the stable isotope signature of molluscs in the seagrass ecosystem. The 𝛅13C values of bivalves ranged from -3 to 3 ‰  and of gastropods ranged from -1 to 4 ‰. Our results show that deposit feeders and grazers have 𝛅13C values in comparison to chemosymbionts. The herbivores and carnivores have comparable 𝛅13C and 𝛅18O isotopic values implying a limited role of diet in shaping the isotopic signature of seagrass molluscs. 

The multi-proxy results support the previous interpretation of Quilon limestone as a seagrass ecosystem. This study provides insight into using a multi-proxy approach of combining molluscan taxonomy, morphology, ecology, and geochemistry in developing a reliable IPSI for identifying paleo-seagrass ecosystems.

How to cite: Kella, V. G., Mallik, A., Chattopadhyay, D., and Gandhi, N.: Reconstruction of a paleo-seagrass ecosystem using molluscan paleoecology and stable isotope geochemistry: A case study from the Quilon Limestone (Miocene), India., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-618, https://doi.org/10.5194/egusphere-egu23-618, 2023.

vSG.21
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EGU23-796
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ECS
Saurav Dutta and Devapriya Chattopadhyay

Stable isotope (δ18O and δ13C) record of the shells of Crassostrea has served as trusted sclerochronological recorders for deciphering the life history and the interannual ambient seawater conditions including temperature and salinity. Several species of Crassostrea are found in modern estuarine system throughout the world. The Bay of Bengal (BOB) in the northern Indian ocean is one such region which experiences the lowest salinity in the tropics due to exceptional and complex hydrological dynamics associated to the Indian monsoon. In this study, we utilized three shells of the endemic species, that are cemented together.  We collected the specimens from Chandipur-on-sea BOB, in the eastern coast of India to understand the relationship between isotope signatures of the shells (δ18Oshell and δ13Cshell), growth history and the environmental parameters (temperature and salinity).

In terms of the microstructural variation within the shells, samples collected from the foliated layer as compared to the chalky calcite layer of the cross sectional hinge region demonstrates no significant difference in their isotopic values. The theoretical isotope profile model based on the satellite data for monthly temperature and salinity data provided the background pattern which when compared to the observed isotope values demonstrated no significant difference for Cha 2 and Cha 3, however, the isotope value of Cha 1 shifted significantly towards negative values. The isotope profile for all the individuals are sinusoidal with repeating δ18Oshell and δ13Cshell minima in the form of relatively sharper and narrower negative half cycles and demonstrates negative offset from the predicted model someimes. We infer the negative shifts and offset of the isotope minimas to be attributed to the lower salinity due to river runoff and precipitation during summer monsoon in this region which also leads to slow or limited growth of the oysters. The grey foliated calcitic bands within the chalky calcitic layers do not incorporate the amplitudes or a particular trend of the isotopic profiles representing no seasonal signature and hence cannot be utilised as age indicators for C.cuttackensis. However, the count of minimas in the isotope profiles revealed the age to be slightly more than 1 year for Cha1 and Cha3 whereas Cha 2 lived for three years atleast. The corresponding growth rates for length and height of the shells decreases with ontogeny, more so for the length than height validating the elongated shape of C.cuttackensis in their adulthood. When compared, the calculated growth rates for C.cuttackensis is highest among all other present and past Crassostrea species globally.

How to cite: Dutta, S. and Chattopadhyay, D.: Signature of monsoon driven salinity fluctuations in stable isotope (oxygen and carbon) record of bivalve shells: Insights from the sclerochronology of three confluent individuals from the Bay of Bengal, India, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-796, https://doi.org/10.5194/egusphere-egu23-796, 2023.

vSG.22
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EGU23-635
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ECS
Gayathri Narath Meethal, Sreevidya Edayiliam, Bhoi Subhakanta, Sahoo Subham Kesari, and Sijinkumar Adukkam Veedu

Deep-sea carbonate dissolution/preservation history is important to better understand marine carbonate system and surface ocean productivity. To understand carbonate dissolution during the last deglacial and Holocene periods in the Eastern BoB, we analyzed foraminifera carbonate dissolution indices viz., perfect test ratio (PTR) of Globorotalia menardii, Menardii fragmentation index (MFI), percentage of total resistant species (RSP), and percentage of total susceptible species (SSP). The core yielded rich assemblages of planktonic foraminifera though retrieved from deeper water depth (3019 m) of the Eastern Bay of Bengal. In general, the preservation is better during last glacial period on record (16-11.7 ka) and poor during Holocene. During Holocene, carbonate dissolution is intense in the early Holocene (12.5 to 8 ka), marked by increased MFI, and decreased PTR values along with less abundance of susceptible species. A slight decrease in the MFI was seen from 8 to 4.9 ka. The late Holocene period was characterized by less MFI and high PTR values. In general, MFI (PTR) was high (low) during the early Holocene compared to the deglacial and mid to late Holocene periods. Interestingly, the dissolution record shows a good relationship with Indian summer monsoon variability. The intense dissolution of the early Holocene might be due to changes in water column chemistry due to the increased river runoff and direct precipitation. We compared our data with existing records from the Andaman Sea and the Central Indian Ocean. The assemblages from the Bay of Bengal show a high degree of dissolution and low preservation during interglacial periods. The result of this study explains that dissolution is more pronounced during the warm interglacial and interstadials and MFI and PTR can be a potential proxy for quantitatively tracking deep marine CaCO3 dissolution in the Bay of Bengal.

 

Keywords: Carbonate dissolution; Planktonic foraminifera, Globorotalia Menardii, deglacial, Holocene.

 

How to cite: Narath Meethal, G., Edayiliam, S., Subhakanta, B., Subham Kesari, S., and Adukkam Veedu, S.: Deglacial- Holocene carbonate preservation in the Bay of Bengal, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-635, https://doi.org/10.5194/egusphere-egu23-635, 2023.

vSG.23
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EGU23-2432
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ECS
Mostafa Mohamed Sayed, Petra Heinz, Ibrahim Mohamed Abd El-Gaied, and Michael Wagreich

Forty-three rock samples have been collected from two sections, exposed at south east Beni-Suef area, Egypt. These samples showed richness in benthic foraminiferal assemblages and only rare occurrences of index planktonic foraminifera. The studied outcrops were lithologically subdivided into two Middle Eocene rock units named from base to top as follow: (1) the Qarara Formation (Lutetian) and (2) the El Fashn Formation (Bartonian). The investigated rock samples yielded 160 foraminifera species and subspecies which belonging to 4 suborders, 19 superfamilies, 34 families and 59 genera. The stratigraphic distribution of the identified species allowed us to construct four local benthic biozones which are: (1) Bolivina carinata Lowest Occurrence Zone (Lutetian), (2) Bulimina jacksonensis Lowest Occurrence Zone, (3) Nonion scaphum Lowest Occurrence Zone and (4) Brizalina cooki / Nonionella insecta Concurrent-Range Zone (Bartonian). These biozones were described and discussed in detail and correlated to equivalents recorded before in Egypt. The rareness of index planktonic foraminifers through the studied sections did not allow a biozonation. The shale samples showed low TOC values which may be related to high sediment influx and/or subjected to oxidation conditions. Bulk rock geochemistry, consistend with the benthic foraminifera ecological preferences, showed that the studied sections were deposited in moderate to high oxygen levels, warm climatic conditions and typical shelf marine settings. The identified species showed strong similarities with southern Tethys areas such as Libya, reflecting migration via trans-Sahara seaway, and minor similarities with those identified from the northwestern Tethys (Italy, France, Spain, England) province attributed to the benthic nature which limit their ability to move for a long distance and related to cooler, latitudinal zoned climatic conditions which was unsuitable for their biological demands.

How to cite: Mohamed Sayed, M., Heinz, P., Mohamed Abd El-Gaied, I., and Wagreich, M.: Paleoclimate and paleoenvironment reconstructions from Middle Eocene successions in Egypt: Geochemical and micropaleontological approaches, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2432, https://doi.org/10.5194/egusphere-egu23-2432, 2023.

vSG.24
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EGU23-2272
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ECS
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Adrita Choudhuri, Devyani Jambhule, Sudakshina Sinha, and Shilpa Srimani

The Precambrian stromatolites are essential proxies for early life on earth. However, recent studies on abiogenic features having gross similarity with biogenic forms have made it difficult to prove their unequivocal biogenecity. Key morphological indicators of stromatolite biogenecity include- its morphological variations, biostrome development, growth through high-energy conditions, and lamina accretion through microbial precipitation, trapping, and binding. A representative outcrop of the Proterozoic stromatolites belonging to the Bhander Limestone and a small horizon present at the base of Sirbu Shale Member, Upper Vindhyan Group of Vindhyan Basin, central India is studied during the present endeavor. Six different stromatolite morphotypes were identified within the studied intervals. Among them, five morphotypes are present within the Bhander Limestone such as large laterally-linked domal stromatolites (S1), columnar stromatolites (both bioherm (S2) and biostrome (S3) type), small-headed stromatolites (S4) and stratiform stromatolites (S5).

Numerous cycles are observed between these morphotypes, especially between the columnar and the small-headed stromatolites. The thickness of the individual cycle varies between 32 cm to 162 cm. The cycles always start with the columnar morphotype (average thickness~57.71 cm) and end with the small-headed morphotype (average thickness ~16.90 cm). The former morphotype (average column height and diameter 7.39 cm and 3.38 cm) shows different variety-branched patterns, vertical and inclined nature. Vertically oriented columns are parallel in nature. The width of the inter-columnar area between the individual parallel columns is variable (average thickness~1.33 cm). The filling material is carbonate cement, stromatolite debris, and chunks. The presence of stromatolite debris within the inter-columnar area indicates agitation within the depositional site. The inclined and branched columnar morphotypes tend to develop bioherm (S2), while the vertically oriented, parallel-natured columnar stromatolites form the biostrome (S3). At the end of each cycle, microbial laminites (thickness ranging from 1 to 8.5 cm) is frequently observed. Occasionally microbial laminites are also present when columnar stromatolites transit to small-headed stromatolites. The latter morphotype has an average column diameter of 1.84 cm. The cyclic alternation of columnar and small-headed stromatolite morphotypes indicates a shift in water depth within the depositional zone, which could be caused by seasonal fluctuation, diurnal cycles, or tectonic factors. Gradual thickness increment of the small-headed morphotypes within the individual cycles towards the upper part of the studied interval indicates a progressive shallowing. A petrographic study reveals the presence of alternate dark-colored micritic and light-colored spar-bearing laminae. The dark micritic laminae attest deposition took place under microbial influence. The sixth morphotype is cabbage-shaped domal stromatolite (S6) (average column height and diameter are 27.11 cm and 20.75 cm, respectively), present only at the basal part of the Sirbu Shale. These domal stromatolites occur above an alternating sand-shale sequence bearing emergence features and form bioherms. Under the microscope, this morphotype shows the presence of ooids and peloids within the dark micritic laminae. Both macro and micro scale variations recorded within the studied stromatolites of the Meso-Neoproterozoic Vindhyan Basin are inkling towards their biogenic origin.

How to cite: Choudhuri, A., Jambhule, D., Sinha, S., and Srimani, S.: Morphological variability of stromatolites and their cyclicity as an indicator of biogenicity- example from a Proterozoic carbonate platform of Vindhyan Supergroup, India, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2272, https://doi.org/10.5194/egusphere-egu23-2272, 2023.

vSG.25
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EGU23-12561
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ECS
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Highlight
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Giulia Piazza, Eduardo Paredes, Valentina Alice Bracchi, Leopoldo David Pena, Jason M. Hall-Spencer, Chiara Ferrara, Isabel Cacho, and Daniela Basso

Calcareous red algae have calcified cell walls constituted by high-Mg calcite or aragonite (Morse et al., 2006). They are considered suitable paleoclimate archives due to their worldwide distribution and their longevity through indeterminate growth (Kamenos et al., 2008). Boron isotopes (δ11B) measured in their calcified thallus are considered a pH proxy (Hemming and Hanson, 1992). In seawater, boron occurs as boric acid and borate ion. Both species are enriched in 11B as pH increases, with boric acid characterized by an enrichment factor of 27‰ compared to borate. The boron isotope proxy theory states that borate is exclusively incorporated in the mineral lattice (Hemming and Hanson, 1992). Therefore, if we measure δ11B in carbonates, we can derive the seawater pH at the time of precipitation. Literature data on δ11B in calcareous red algae are sparse, and the mechanisms of boron incorporation are still poorly known (Piazza et al., 2022). We tested the boron isotope-pH proxy on calcareous red algae grown at 1 m depth close to CO2 seeps off the coasts of Ischia (Italy), and Methana (Greece), which are both characterized by a broad range of natural pH in seawater (from 6.80 ± 0.43 to 8.08 ± 0.07 units). Environmental data characterizing the seawater during the algal growth were extracted from CMEMS products (Marine Copernicus Service Information), or provided by literature. The δ11B values in the algae (δ11Balgae) analysed by Multi Collector Inductively-Coupled Plasma Mass Spectrometry ranged from 22.23‰ to 26.59‰, calibrated over a range of δ11B in aqueous borate (δ11Bborate) extending from 12.68‰ to 18.05‰. A crystallographic control over boron incorporation was shown by the difference in the isotopic composition of carbonate polymorphs, with Mg-calcite enriched in 11B compared to aragonite. Values of δ11Balgae higher than δ11Bborate could be attributed to the up-regulation of the calcifying fluid pH exerted by the algae. We proposed a multi-specific calibration using literature data of boron isotopes in cultured coralline algae combined with our new data on wild-grown specimens, widening the range of pH considered for δ11B calibrations so far. The proposed calibration is particularly useful when experimental calibration is not possible, such as in the fossil record and in the case of ambiguous identifications.

References

Hemming N. G. & Hanson G. N. 1992. Boron isotopic composition and concentration in modern marine carbonates. Geochim. Cosmochim. Acta, 56, 537-543.

Kamenos N. A., Cusack M. & Moore P. G. 2008. Coralline algae are global paleothermometers with bi-weekly resolution. Geochim. Cosmochim. Acta, 72, 771-779.

Morse J. W., Andersson A. J. & Mackenzie F. T. 2006. Initial responses of carbonate-rich shelf sediments to rising atmospheric pCO2 and ‘‘ocean acidification’’: role of high Mg-calcites. Geochim. Cosmochim. Acta, 70, 5814-5830.

Piazza G., Bracchi V. A., Langone A., Meroni A. N. & Basso D. 2022. Growth rate rather than temperature affects the B / Ca ratio in the calcareous red alga Lithothamnion corallioides. Biogeosciences, 19, 1047-1065.

How to cite: Piazza, G., Paredes, E., Bracchi, V. A., Pena, L. D., Hall-Spencer, J. M., Ferrara, C., Cacho, I., and Basso, D.: Multi-specific calibration of the B isotope proxy in calcareous red algae for pH reconstruction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12561, https://doi.org/10.5194/egusphere-egu23-12561, 2023.