EVIDENCE OF PALEOCLIMATE FLUCTUATIONS AT THE END OF THE LAST ICE AGE, UNION CITY, IN

Little is known about the small-scale fluctuations in climate during the last Glacial/Interglacial transition. Sediments deposited in relict basins during the retreat of the Laurentide Ice Sheet can provide evidence of this climate change.

Site 0209 is a bog formed from a relict basin just north of the Union City Moraine near Union City, IN. An 8 meter sediment core recovered from this bog shows a base of glacial till overlain by ~4m bed of mottled silt and a transition into a ~1m bed of laminated silt. High resolution loss-on-ignition (LOI) analysis records an initial spike in organic productivity occurring in the middle of the mottled silt unit, and an even greater increase in organics is seen in the transition to laminated silt and throughout that unit. Chlorophyll analysis performed on the sediment is also used and an indicator for organic productivity in the basin.

This data shows relatively cool and stable climate conditions occurred at site 0209 during the deposition of the base of the mottled silt unit. The younger sediments found above this point show greater variability in organic content and could indicate climate fluctuations that occurred during the end of the Younger Dryas and into the beginning of the Holocene.