BIOMARKERS OF NEOPROTEROZOIC BIOTA

Organic matter provides an important source of information about Neoproterozoic biota and environmental change. Sediments with abundant and well preserved organic matter occur widely and include the full range of facies and environments. Heightened relative abundances of specific kinds of hydrocarbons such as steranes and waxy n-alkanes mark the rise to prominence of algae while C30 steranes indicate that sponges were important constituents of shallow water Neoproterozoic to Early Cambrian environments. Ethyl and diethyl alkanes are characteristic of microbial mat facies in many sediments and appear to be markers for benthic communities of sulfide oxidizing microbes that are also prominent at this time. Bulk and compound-specific isotopic data show anomalous ordering patterns quite unlike those seen in Phanerozoic rocks and these may be related to the prevailing oceanic redox systems. The disappearance of this feature near the Cambrian boundary may be related to the reorganization of biogeochemical cycles that accompanied the metazoan radiation1. 1. Logan G.A., Hayes J.M., Hieshima G.B. and Summons R.E., 1995, Terminal Proterozoic reorganisation of biogeochemical cycles. Nature 376, 53-56.