Carbonate: an ever changing spatial and temporal record of life and the events that shaped it

Abstract:

Carbonate, an abundant precipitate in modern and ancient oceans, is at once a record of mineralized life living at a moment in time and a record of Earth’s aquatic environments. Life and environment inform the macro- and microscopic character of carbonates as well as the chemical composition. Here we explore the processes recorded in the abundance of ¹³C and ¹⁸O in carbonates through time and space. The relative depletion or enrichment of these two isotopes can reflect climate, including both temperature and evaporative history, biomineralization, dynamics between photosynthesis and respiration on multiple scales, and alteration after formation. Here, we explore the results of a meta-analysis of δ¹³C and δ¹⁸O through time, space and species. When are carbon and oxygen isotopes a biosignature? When do they inform planetary habitability? When are they an imperfect historian? These questions are difficult to answer in a record that is changing through space and time. Our meta-analysis of co-variation in these two isotopic proxies aims to assess the relative contributions of life, environment, and alteration through time and space.