1.88 Ga old cyanobacterial specialization revealed by nano-XRF mapping of trace metals in Hurniospora fossils

This experiment searches for indications of the oxygenic photosynthesis of exceptionally well-preserved 1.88 Ga old spheroidal microfossil of cysts from the Gunflint biota (Huroniospora). The aim is to evaluate the transition metals quota by nano-XRF imaging by least damaging conditions of few exceptionally well-preserved 1.88 Ga specimens whose cyanobacterial taxonomy is still debated by comparison with younger Proterozoic microfossils of unambiguous cyanobacterial phylogenetic classification. This experiment will provide the smallest statistical and control robust sampling to demonstrate cyanobacterial specialization 1 billion years earlier than estimated by morphological dating. It is the continuation of the first session of 9 shifts (ES-1566 in Janv. 2025) in which nano-XRF maps were acquired for the Gunflint biota. We thus require 9 additional shifts on ID16B in pink beam mode at 17 keV for nano-XRF to establish the necessary younger controls.