In-situ provenance of brGDGTs in peat sediments: A case study from southern China and a comparison of global results

Abstract

Sedimentary branched glycerol dialkyl glycerol tetraethers (brGDGTs) have been proposed as indicators of environmental change for more than a decade. However, the origin of brGDGTs in terrestrial sediments is a fundamental issue affecting their use in paleoenvironmental reconstruction. Although peat sediments are one of the best terrestrial archives for paleoclimatic studies, the origin of brGDGTs in peat sediments remains poorly constrained. Here, we report the results of a study of brGDGTs in peat surface sediments, peat core sediments, and in the surrounding surface soils of the Shiwangutian (SWGT) peatland in southern China. Comparison of the molecular distributions and absolute concentrations of the total brGDGTs extracted from these different sample types reveals the dominant in-situ origin of the brGDGTs in the SWGT peatland. We then compare the results from globally-distributed surface peat sediments and surface soils, which confirms the dominant in-situ provenance of brGDGTs at almost all of the studied peatlands. Furthermore, in specific environments, such as in peatlands in cold and alkaline environments, the origin of brGDGTs could be different to that in other environments. Our results provide fundamental evidence for the provenance of brGDGTs in peat sediments, with relevance for peat-brGDGTs-based paleoclimatic reconstructions.