Giant gastropods are among the largest mollusks in the fossil record, but their potential as paleoseasonality archives has received little attention. Here, we combine stable isotope and trace element analyses with microscopic observations and growth modeling on shells of two species of the gastropod genus Campanile: the extinct Campanile giganteum from Lutetian (~45 Ma) deposits in the Paris Basin (France), the longest gastropod known from the fossil record, and its modern relative Campanile symbolicum from southwestern Australia. The C. giganteum shells contain original aragonite and have pristine nacre in their apertures. We show that these gastropods attained growth rates exceeding 600 mm/year along their helix, depositing over 300 cm 3 aragonite per year. High growth rates and excellent preservation make C. giganteum excellent archives for reconstructing environmental change at high (potentially daily) temporal resolution, while providing enough material for methods such as clumped isotope analysis. Growth models show that Campanile gastropods grew nearly year-round, albeit slower in winter. Stable oxygen isotope ratios in modern C. symbolicum faithfully record a seasonal variability of 18-25°C in sea surface temperature, only failing to record the coolest winter temperatures (down to~16°C). Similarly, C. giganteum specimens likely record a nearly complete seasonal temperature range. Assuming constant sea water isotope composition, their oxygen isotope seasonality of up to 2.5‰ would translate to a Lutetian temperature range of 21-32°C in the Paris Basin. We hypothesize that these high and seasonally variable temperatures formed the breeding ground for the Lutetian shallow marine biodiversity hotspot in the Paris Basin.

<p>Instrumental climate data are only available for the last few hundred years. To extend this record back in time, climate proxies are used. However, on the geological timescale, the temporal resolution of most paleoclimate records does not provide information about seasonality, let alone events on the weather-timescale. These weather-timescale events are becoming more frequently integrated in models to predict future climate change, but reconstructions of variability with such short timescales in the geological record are extremely rare.</p><p>A recent study by de Winter et al. (2020) has revealed that the Eocene giant marine gastropod <em>Campanile giganteum</em> (Lamarck, 1804) had growth rates exceeding 600 mm/year along the helix, far exceeding those of most other modern and fossil molluscs. With such high growth rates, these giant gastropods have the unique potential to record weather-timescale variability in the Eocene greenhouse world. Therefore, we generated a high-resolution (mm-scale) δ<sup>18</sup>O record on a well-preserved specimen of <em>C. giganteum</em> from the Paris Basin in Fleury-la-Rivière, France, in order to generate a unique ultra-high resolution record of intra-annual, weather-timescale variability in the Eocene. Our preliminary results show a clear seasonal pattern with δ<sup>18</sup>O values ranging between 0.1‰ and -2.5‰, superimposed by weekly variations of up to 0.5‰. This could provide insights in weather patterns in the Eocene greenhouse climate and potentially allow the identification of extreme weather events.</p><p> </p><p><strong>Reference</strong></p><p>de Winter N.J., Vellekoop J., Clark A.J., Stassen P., Speijer R.P., Claeys P., (2020) The Giant Marine Gastropod <em>Campanile Giganteum</em> (Lamarck, 1804) as a High‐Resolution Archive of Seasonality in the Eocene Greenhouse World., Geochemistry, Geophysics, Geosystems, 21(4), https://doi.org/10.1029/2019GC008794</p>

<p>During the Lutetian (middle Eocene, 48-41 Ma), Earth’s climate was in transition from greenhouse to icehouse conditions, sometimes referred to as a “doubthouse climate”. These circumstances allowed the Paris Basin (France) and Hampshire Basin (UK) to be hotspots for marine biodiversity, hosting a diverse assemblage of molluscs, including members of the Conidae family. Most species within the family are known to live for multiple years, possibly up to a decade, in fully marine conditions and mostly in shallow waters. Under these fully marine conditions, Conidae shells would be excellent recorders of sea water temperatures, allowing paleotemperature reconstruction for the two basins. However, climatic parameters such as temperature extremes or seasonality have not been well documented in the two basins during the Lutetian, with only a handful of studies available [Andreasson & Schmitz 2000, Huyghe et al. 2015]. Here, we made longitudinal and latitudinal comparisons between the two basins, using carbon and oxygen stable isotope data measured on different Conidae species, in order to provide seasonality reconstructions in north-western Europe. The focus of this research is mainly on assessing isotopic variation of seasonality within a basin and comparison between basins, including previously published data. SEM and cold cathodoluminescence shows that for both basins the preservation of the mollusc carbonate is sufficient to allow for approximations of the original environmental conditions. Three specimens from each basin were sampled by means of manual drilling along the growth axis of the shells. Obtained stable carbon and oxygen isotope data were used to reconstruct variation in paleotemperature and productivity. Following the methodology of Kobashi & Grossman 2003, patterns in the isotopic signature throughout the life of each specimen give an indication of the environmental reconstruction and any internal variability. By comparing existing and newly collected data from the same localities and family, we examine whether differences in seasonality are species-specific, due to climatic variation, or reflect environmental differences. <br>Andreasson, F.P., Schmitz, B. (2000) Temperature seasonality in the early middle Eocene North Atlantic region: Evidence from stable isotope profiles of marine gastropod shells, GSA Bulletin, 112, 628-640. <br>Huyghe, D., Lartaud., F., Emmanuel, L., Merle, D., Renard, M. (2015) Palaeogene climate evolution in the Paris Basin from oxygen stable isotope (δ18O) compositions of marine molluscs. Journal of the Geological Society, 172, 576-587. <br>Kobashi, T., Grossman, E.L. (2003) The oxygen isotopic record of seasonality in Conus shells and its application to understanding late middle Eocene (38 Ma) climate, Paleontological Research, 7, 343-355. </p>

<p>Carbonate clumped isotope thermometry, based on the temperature-dependence of clumping of <sup>13</sup>C and <sup>18</sup>O in the carbonate molecule (Δ<sub>47</sub>) is a promising tool for paleoclimate reconstruction. In the last few years many discrepancies among Δ<sub>47</sub>-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 pCO<sub>2</sub> 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 pCO<sub>2</sub> and media carbon chemistry are known to trigger vital effects in carbon and oxygen isotopes in coccoliths, we decoupled the temperature solubility effect on CO<sub>2</sub> by manipulating culture CO<sub>2</sub> independently. Three pCO<sub>2</sub> 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 pCO<sub>2</sub> conditions.</p> <p>References:</p> <p>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." <em>Geophysical Research Letters</em> 48 (7).</p> <p>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.” <em>Geochimica et Cosmochimica Acta </em>208: 335-353.</p> <p>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." <em>Geochimica et Cosmochimica Acta</em> 270: 160-183.</p>

During the Eocene greenhouse (56.0–33.9 Ma), northwest Europe was dominated by a semi-arid para-tropical climate but the paleohydrological conditions are poorly known. To gain more insight into seasonal hydrological conditions in the region, we compare Lutetian (middle Eocene, ~44-45 Ma) mollusk δ18O records from two shallow marine basins on either side of the English Channel, i.e. the Paris and Hampshire Basins. The semi-circular Paris Basin was open to the Atlantic Ocean, while the Hampshire Basin was more enclosed and influenced by the draining of several rivers. The proximity of the basins suggests that they experienced roughly similar seawater temperatures but the seasonal hydrology is expected to have been different between these basins. Among the numerous mollusks present in both basins are several members of Conidae, a gastropod family that is particularly well-suited for paleoseasonality reconstructions. To assess the paleohydrological differences between these basins we analyzed the stable oxygen isotopic composition of three specimens of Eoconus deperditus from the Banc a Verrains in the middle part of the Calcaire Grossier Formation of the Paris Basin (France), and three specimens of Eoconus edwardsi from the Shepherd’s Gutter Bed in the upper part of the Selsey Formation of the Hampshire Basin (United Kingdom). While the seasonal variability appears to have been similar between these basins, the δ18O values of the Hampshire Basin specimens are consistently lower than those in the Paris Basin, suggesting a regional difference in δ18Osw of 1-2‰ between the basins. This difference in δ18Osw was likely related to a hydrological disparity between the Paris and Hampshire basins.