A ~13,000 YEAR RECORD OF CLIMATE AND ENVIRONMENTAL CHANGE AT ZURICH BOG, NY

Long, continuous sediment core records are critical for assessing the evolution of climate and ecosystems during the Holocene. A ~7.3 m long vibracore was collected from Zurich Bog in order to learn about past climate and environmental conditions in the New York Finger Lakes region over the last ~13,000 years. We analyzed the core using several climate proxies: loss-on-ignition (weight percent organic matter, carbonate, and terrigenous sediment), bulk magnetic susceptibility, atomic C/N ratios, and the stable carbon isotopic composition (δ¹³C) of bulk organic matter. Five radiocarbon ages, from three stratigraphic levels in the core, were calibrated to calendar years using CALIB 7.1 and then a constant linear sedimentation rate was assumed between these dated intervals to create an age-depth model.

We recognized three main units in the core. The base of the core (Unit 1) is ~0.4 m thick and comprised of alternating light gray silty clay and sand beds with very minor, if any, organic matter. The middle unit (Unit 2), ~3.2 m thick, is made up of banded to laminated brown to beige silt. Autochthonous organic matter and calcite are the primary components of this unit. The uppermost unit (Unit 3), ~3.7 m thick is made of peat. This unit exhibits a gradual increase in terrestrial organic matter from ~70 to ~95% upcore. Each transition between units demarcates an important shift in the landscape. Between Unit 1 and 2, the region abruptly transitioned from a relatively shallow bay of proglacial Lake Iroquois to a smaller isolated lake at ~13,000 years ago. This small, relatively shallow lake probably existed for ~7,000 years. The lake slowly became more eutrophic as it filled in with mainly terrigenous sediment and terrestrial organic matter. Since then, this site has been a fen to bog-type environment. Future work includes spectral analysis of the climate proxy datasets to identify significant periodicities using the Singular Spectrum Analysis and Multi Taper Method.