Millennial-timescale climate change over the last 800 kyrs evidenced by magnetic, colorimetric and ATR-FTIR data from the Suhia Kladenetz quarry loess-paleosol sequence (Pleven, Bulgaria)

Eastern European loess-paleosol sequences (LPS) are excellent archives of past climate change. Millennial-timescale climate change is successfully evidenced in loess of the last and penultimate glacial periods. However, study designs with similar or lower sampling resolution strategies and/or single proxy investigations do not favor their identification for earlier glacials, which are generally scarcer, thinner and characterized by lower sedimentation rates. The high-sampling resolution multi-proxy study presented here demonstrates the first evidence of millennial-timescale climate change for periods older than MIS6 archived in an Eastern European LPS.

The Suhia Kladenetz 27 m long profile was sampled continuously at a 2 cm resolution for bulk sediment. Magnetic and colorimetric measurements are performed on all samples. ATR-FTIR data is acquired at the same resolution through loess units and at a 12 cm interval elsewhere, while grain size analyses are conducted continuously at a 12 cm interval. Rock magnetic data and microscopic observations, from our previous work, characterized a 20-cm-thick outcropping tephra in the MIS6 loess unit and identified several cryptotephras. Moreover, a correlative age model demonstrating that the LPS covers the last ~800 kyrs allowed to provide age estimates for the tephra and cryptotephras and thereafter to deduce their likely volcanic sources.

The integrated age model in combination with high-resolution colorimetry-based estimates of goethite and hematite concentrations, and clay mineralogy highlight a cyclicity undoubtedly driven by climate change within interstadials/stadials as shown by correlations with the NGRIP δ18O ice core records for the last glacial/interglacial cycle.