Submit a preprint


Evidence of high Sr/Ca in a Middle Jurassic murolith coccolith speciesuse asterix (*) to get italics
Baptiste Suchéras-Marx, Fabienne Giraud, Alexandre Simionovici, Rémi Tucoulou, Isabelle Daniel
<p>Paleoceanographical reconstructions are often based on microfossil geochemical analyses. Coccoliths are the most ancient, abundant and continuous record of pelagic photic zone calcite producer organisms. Hence, they could be valuable substrates for geochemically based paleoenvironmental reconstructions but only Sr/Ca is exploited even if it remains poorly understood. For example, some murolith coccoliths species have very high Sr/Ca compared to the common 1-4 mmol/mol recorded in placolith coccoliths. In this study, we analyzed the elemental composition of the Middle Jurassic murolith *Crepidolithus crassus* by synchrotron-based nanoXRF (X-ray Fluorescence Spectroscopy) mapping focusing on Sr/Ca and compared the record to two placolith species, namely *Watznaueria contracta* and *Discorhabdus striatus*. In *C. crassus*, Sr/Ca is more than ten times higher than in both placoliths and seems higher in the proximal cycle. By comparison with the placoliths analyzed in the same analytical set-up and from the same sample, we exclude the impact of the diagenesis and seawater Sr/Ca to explain the high Sr/Ca in *C. crassus*. Based on comparisons to *Pontosphaera discopora* and *Scyphosphaera apsteinii* which also have high Sr/Ca, it seems more likely that high Sr/Ca in *C. crassus* is either due to the vertical elongation of the R-units of the proximal cycle or related to the action of the special polysaccharide controlling the growth of those vertically elongated R-units that may have affinities to Sr 2+. In order to apply the Sr/Ca proxy to muroliths, further investigations are needed on cultured coccoliths.</p> should fill this box only if you chose 'All or part of the results presented in this preprint are based on data'. URL must start with http:// or https://
You should fill this box only if you chose 'Scripts were used to obtain or analyze the results'. URL must start with http:// or https://
You should fill this box only if you chose 'Codes have been used in this study'. URL must start with http:// or https://
Calcareous nannofossils; Coccoliths; ESRF; Muroliths; Sr/Ca; Ultrastructure; XRF
Microfossils, Micropaleontology, Nanofossils
No need for them to be recommenders of PCIPaleo. Please do not suggest reviewers for whom there might be a conflict of interest. Reviewers are not allowed to review preprints written by close colleagues (with whom they have published in the last four years, with whom they have received joint funding in the last four years, or with whom they are currently writing a manuscript, or submitting a grant proposal), or by family members, friends, or anyone for whom bias might affect the nature of the review - see the code of conduct
e.g. John Doe []
2020-05-18 16:11:35
Antonino Briguglio