Characterizing the Eemian-Weichselian transition in northwestern Europe with three multiproxy speleothem archives from two Belgian cave systems (Han-sur-Lesse and Remouchamps)
Résumé
IInterglacial to glacial transitions represent the most drastic turnovers in the Quaternary climate system.
Yet, millennial-scaled climate variability and stochastic internal variability that result in these transitions
remain still poorly understood. Here, three speleothem archives from two different cave systems in
Belgium (Han-sur-Lesse and Remouchamps) are investigated using a multiproxy approach in order to
characterize the last interglacial to glacial transition. The studied samples roughly span the period
between 125 ka and 100 ka, covering a large part of the Eemian and early Weichselian. The speleothems
show a high reproducibility for δ13C, which is interpreted as a proxy for past vegetation activity,
controlled by vegetation assembly above the cave. All three speleothems show a drastic increase in δ13C
between 118 to 117 ka, reflecting a rapid change of vegetation assembly from last interglacial temperate
tree species towards glacial more open grass vegetation. This event shows a strong affinity in terms of
timing and climatic expression with the Late Eemian Aridity Pulse (LEAP) at 118 ± 1 ka, identified in
pollen records from Western Germany. Aligning the chronologies of the two independently dated Han-sur-Lesse speleothem records enables a more precise absolute chronology and provides an age of 117.7 ±
0.5 ka to the start of this event in the Belgian speleothems. This event marks a distinct transition in the
Belgian speleothem proxies between Eemian optimum conditions and increased variability during the
glacial inception and the start of this event at 117.7 ± 0.5 ka is therefore proposed as the Eemian-
Weichselian transition and consequently the start of the glacial inception in the studied speleothems.
High-resolution analysis shows that the 117.7 ± 0.5 ka event is initiated by a cooling pulse followed by a
decrease in precipitation. A similar short-lived cooling event is also registered in multiple North-Atlantic
sediment archives. This study hypothesizes that the origin of the cooling event at 117.7 ka is an internal
climate response caused by the substantial amount of freshwater input from degraded ice-sheets by the
end of the Eemian (~120-118 ka). There is thus a clear climatic connection between the Belgian
speleothems and other continental European archives and North Atlantic marine archives, providing the
possibility of improving less constrained chronologies by alignment to the independently constructed
speleothem age-depth model presented in this study.
Origine : Fichiers produits par l'(les) auteur(s)