Deep into an interglacial: A compound-specific biomarker study of Marine Isotope Stage 11 (Tenaghi Philippon, Greece)
Abstract:Marine Isotope Stage (MIS) 11 is a mid-Pleistocene interglacial, characterized by a minimum in orbital eccentricity, and therefore often studied as a climate analogue for the Holocene (MIS 1). However, a slightly different phasing of obliquity and precession between these two interglacials sparks strong interrogatives about the MIS 1-11 alignment and its meaningfulness for Holocene predictions.
MIS 11c represents an unusually long warm subphase immediately after the “Mid-Brunhes Event” (≈430 ka bp), which marks the passage from the 40 ka (obliquity-) to the 100 ka (eccentricity-driven) world. The following subphases MIS 11b and MIS 11a, represent a series of cold-warm oscillations, terminated by the glacial inception of MIS10.
Our aim is to describe atmospheric circulation patterns and their changes through glacial and interglacial transitions while tracking the evolution of the respective terrestrial temperatures and levels of biomass burning.
We worked on a peat core from Tenaghi Philippon, an intramontane peat deposit in Eastern Macedonia (Greece); its position at the convergence zone of Atlantic, monsoonal and Siberian-influenced climates makes it an excellent archive to study climate change during MIS11 in the Eastern Mediterranean.
We show the stable hydrogen isotopic composition of higher plant waxes (δD) as proxy for changes in atmospheric circulation and related shifts of moisture source, together with changes in air temperature based on GDGTs (Glycerol Dialkyl Glycerol Tetraethers) analysis. In addition, we studied the chain-length distribution of higher plant-wax n-alkanes to derive the “aquatic index” (Paq), a measure of wetland aggradation. Paq varies between 0.2 and 0.9, indicating pronounced shifts of the water table throughout the record, and neatly traces Termination V (the warming leading to MIS11), MIS11c as well as the inception of MIS10.
Levoglucosan in turn, a marker for biomass burning, shows a strong glacial-interglacial dichotomy with low levels throughout Termination V and MIS11 followed by elevated values after the MIS10 glacial inception.