Fig. 5: Mode of fossil preservation.

a, Backscattered electron microscopy image revealing white iron oxide minerals and some limited black carbonaceous material within the fossils of the Cabrières Biota. b, The iron oxides appear shapeless, lacking distinct framboids or euhedral minerals. c, Semi-quantitative elemental proportions from SEM–EDX analyses indicate that the fossils exhibit a higher iron content compared with their surrounding aluminosilicate matrices. d, Fe K-edge XANES spectroscopy shows that the iron present in the Montagne Noire fossils exists in the form of oxides and hydroxides. e,f, Synchrotron µXRF major-to-trace elemental mapping shows that modern weathering elements such as manganese and arsenic are deposited on the surface of the samples. Scale bars represent 100 µm in a, 50 µm in b and 5 mm in e and f.