Higher abundance of greigite during glacial intervals coincides with small increases of the S content (Fig. 11B). Greigite levels in glacial sediments cannot be correlated between cores (Fig. 12), which suggests that greigite concentrations are driven by local processes. We suggest that faecal pellets could be a suitable microenvironment for sulphate reduction. And while greigite could potentially act as proxy for faecal pellets in glacial sediments, unfortunately, we cannot rely on this possible indicator since the greigite is very sensitive to onshore alterations after sampling (Snowball and Thompson, 1990).