Increased presence of greigite (high SIRM/κLF) coincides with maximum sulphur contents observed at the beginning of interglacial stages (Fig. 11A). At similar levels in another sediment core of Lake Baikal, Watanabe et al. (2004) observed pyrite mineralization. They attributed these pyrite-rich levels to mineralization at sediment/water interface under anoxic bottom water conditions. However, we prefer to interpret the greigite as a result of magnetite transformation when sulphate reduction occurs in the interglacial sediments. Peak sulphur contents would therefore be due to sulphur mineralization within the sediment and would not result from an enrichment of the sediment in sulphur at the sediment/water interface.
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).
Higher abundance of greigite during glacial intervals also 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).
Downcore variations of rock magnetic parameters and simplified lithological description for the sedimentary sequence VER 98-1-14. Here, MIS are denoted by numbers in the lithological column. The black squares filled intervals mark occurrences of greigite characterised by a high magnetic susceptibility (κLF) in parts, with a low coercive mineral dominating the magnetic signal (S-ratio close to 1), a high SIRM/κLF, a strong loss of ARM intensity between the demagnetisations steps 50 and 65 mT and finally a deviation of the inclination of ARM. The dark grey intervals mark occurrences of magnetite dissolution, with a low S-ratio resulting from relative higher hematite content in the ferromagnetic components. The assignment of greigite and dissolved magnetite is based on subsequent interpretation. Magnetic susceptibility (κLF) vs. S-ratio for the sedimentary sequence VER 98-1-14 showing S-ratio gathered around 0.95 in glacial sediments and scattered from 0.7 to 1 in interglac