GEOCHEMISTRY AND PALYNOLOGY GO HAND IN HAND: TESTING THE TOXIC EFFECT OF REDOX-SENSITIVE METALS ON PALEOZOIC PALYNOMORPHS

Our collaborative research has repeatedly demonstrated the presence of malformed fossil organic-walled microplankton at the onset of δ¹³C_carb excursions, and throughout the early phases of the extinctions associated with dramatic periods of global climate and environmental change (e.g. Delabroye et al. 2012). By analogy with metal-induced malformations in modern marine microplankton, we posit that teratology might serve as an independent proxy for monitoring changes in the metal concentration of the Paleozoic ocean. In order to test this hypothesis we systematically evaluate palynomorph (chitinozoans, acritarchs) geochemistry at high-resolution through O-S events and δ¹³C excursions, and identify changes in plankton population dynamics across these events. Vandenbroucke et al.(2015) used ToF-SIMS to analyse chitinozoans, however, although the trends are informative in a single section, these data were semi-quantitative. Instead, we are developing a new methodology combining electron microprobe analysis and LA ICP-MS, to fully quantify the major and trace element composition of microfossils. Palynomorph microprobe measurements from the well-known Upper Ordovician strata of Anticosti Island (Canada), reveal trends in the elemental behaviour throughout the section that coincide with periods of biologic and environmental change. Importantly, a series of single specimen analyses demonstrate taxon differentiation for certain trace elements (Ni, Ti, V) at specific levels, which raises the tantalizing possibility that the elemental signature represents the in vivo composition. If in fact primary, these chemical signatures might help unravel the biology of these organisms and their sensitivity/tolerance to metals that might ultimately identify chemical changes in marine environments. These preliminary findings suggest that chemical palynology might be an exciting frontier with the potential to revolutionize our understanding of biologic and geochemical interactions that may help illuminate Earth’s deep history.