Biomarker proxies for reconstructing Quaternary climate and environmental change

To reconstruct past environmental changes, a range of indirect or proxy approaches can be applied to Quaternary archives. Here, we review the complementary and novel insights that have been provided by the analysis of chemical fossils (biomarkers). Biomarkers have a biological source that can be highly specific (e.g. produced by a small group of organisms) or more general. We show that biomarkers are able to quantify key climate variables (particularly water and air temperature) and can provide qualitative evidence for changes in hydrology, vegetation, human–environment interactions and biogeochemical cycling. In many settings, biomarker proxies provide the opportunity to simultaneously reconstruct multiple climate or environmental variables, alongside complementary and long-established approaches to palaeoenvironmental reconstruction. Multi-proxy studies have provided rich sets of data to explore both the drivers and impacts of palaeoenvironmental change. As new biomarker proxies continue to be developed and refined, there is further potential to answer emerging questions for Quaternary science and environmental change.