Improving Climate Records Through a Mechanistic Understanding of Sub-Micron Heterogeneity in Environmental Materials
EMSL Project ID
47968
Abstract
From the pace of the ice ages to how the carbon cycle has changed through time, much of what we know about earth history and climate dynamics is based on proxies. Recorded as trace element anomalies or as isotopic shifts, proxies are geochemical relationships that connect environmental parameters to the bulk composition of a natural sample. Recent developments in high-resolution imaging, however, have shown that most environmental materials are characterized by small-scale compositional heterogeneity, complicating the traditional interpretation of proxy-based records. To accurately interpret past records, we need to develop a mechanistic understanding of proxy behavior that can explain small-scale heterogeneity, that can link this variability to bulk composition, and that can resolve specific environmental signals from the bulk record. This proposal will harness the rich and newly accessible chemical data encoded in small-scale heterogeneity, developing a set of tools that can probe the mineral growth process and that can use these data to reconstruct past environmental conditions. Focusing specifically on biomineralization, a complex chemical process occurring at the biological-mineral interface during skeletal self-assembly, our research will quantify the contribution of three key processes to small-scale heterogeneity during skeletal growth. The three processes targeted in this study are: ion transport, organic-mineral interactions, and kinetic control of impurity incorporation. To measure dynamic processes like ion transport and growth rate effects, we will use a set of stable isotope-based methods that were recently developed by our lab. These methods rely on NanoSIMS imaging, one of the only tools that can map the distribution of enriched stable isotopes at the sub-micron scale. To characterize the contribution of organic components towards small-scale heterogeneity, we will use atom probe tomography (APT) to map elemental concentrations at the organic-mineral interface. Equipped with a newly acquired NanoSIMS and an atom probe, few institutions other than EMSL have the appropriate combination of expertise and key instruments necessary for measuring small-scale heterogeneity, making this project especially well matched to the unique capabilities of EMSL.
The biomineral target of our study, the CaCO3 skeletons of foraminifera, was specifically chosen because the preserved skeletons from this organism are widely used to develop climate records. By improving the interpretation of chemical signatures in this archive, our research will directly improve the precision and accuracy of climate records, towards a better understanding of earth system dynamics. Collectively, the research detailed in this proposal will lead to a mechanistic understanding of the processes controlling small-scale heterogeneity in environmental materials, with applications in climate science, in geochemistry, and in the design of complex biomimetic materials.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2013-10-01
End Date
2014-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Bonnin E.A., Z. Zhu, J.S. Fehrenbacher, A.D. Russell, B. Honisch, H.J. Spero, and A.C. Gagnon. 2019. "Submicron Sodium Banding in Cultured Planktic Foraminifera Shells." Geochimica et Cosmochimica Acta 253. PNNL-SA-142331. doi:10.1016/j.gca.2019.03.024