Fig. 2
From: Late Neoproterozoic seawater oxygenation by siliceous sponges
The estimated siliceous sponge spicule abundance and geochemical records across the Ediacaran–Cambrian boundary at the Lijiatuo section. a Stratigraphic context and age of the Lijiatuo section based on stratigraphic records from South China25(*) and a dated ash layer26(**); b Abundance of Si-bearing components calculated by a geochemical mass balance. Colour shading at the bottom indicates several estimates for the abundance of sponge-derived- and inorganic silica based on assumptions of ε30Si(sponge-seawater) between −6‰ and −2‰. Occurrences of sponge spicules and putative radiolarians, i.e., round objects (Supplementary Fig. 5) are indicated by black circles (our samples) and gray circles28. c TOC concentrations; d CeN/CeN* (Ce-anomalies); open symbols mark samples with PrN/YbN > 1, indicating flat, non-seawater REE patterns; e Al2O3-normalized Ge/Si and corresponding Ge/Si of illite; f YN/HoN ratios. For better visibility, samples are plotted with an equidistant X axis. In c-f fsponge (yellow shades) shows the abundance of Si in sponges relative to total non-detrital Si-bearing components that is independent of ε30Si(sponge-seawater). Uncertainty envelopes of fsponge are calculated from uncertainties in endmember estimates and a Monte Carlo procedure, and represent 50% confidence intervals (Supplementary Data 6)
