POST-GLACIAL AND HOLOCENE WATER-TABLE RECONSTRUCTION OF A WETLAND IN CENTRAL-WESTERN NEW YORK

In the northeastern United States, many paleoclimate studies document fluctuations in effective moisture and temperatures since the last deglaciation. However, these studies show considerable disagreement constraining the timing of wet and dry climates across New York State. We targeted one wetland in the southern Lake Ontario watershed north of Geneva, NY for study to better understand the spatial and temporal variation in hydroclimate conditions between the Catskill and Finger Lakes regions. We collected multiple cores along a N-S transect using a Russian peat corer and vibracorer. We analyzed each core for magnetic susceptibility (MS; 1-cm interval), loss-on-ignition (1-cm interval), and u-X-ray fluorescence (0.5 mm interval). Bayesian age-depth models constructed using Bacon constrained the timing of events.

The cores bottomed in grey lacustrine silty clay. In most cores, the silty clay was overlain by a sandy unit, banded carbonate-sapropel unit, herbaceous peat, and then fragmental woody peat, documenting a gradual infilling of the lake basin. We used MS, Ti, K, Zr, Rb, and % terrigenous as proxies for detrital sediment input and lower water levels. Fe was used with caution to infer detrital inputs as it may also be a redox indicator. Mn/Fe was used as a proxy for oxidation where higher values reflect an oxygenated water column or drop in water table in the sapropel and peat. Ca and Sr were either from allochthonous sources or from autochthonous precipitation of carbonate (mud or mollusks).

The siliciclastic sandy unit with high Ti, K, Rb, Zr, Mn, MS values accumulated across the basin by ~13.2 cal ka. A transition to a shallow (2-9 m) carbonate-rich (high Ca, Sr, mollusks) lake occurred at ~12.2 ka and this lake existed for nearly 6 ka. The abrupt shift from the carbonate lake to fen phase (higher % organic matter) at ~6.3 cal ka is concurrent with evidence for low lake levels in the Finger Lakes and a transition to warm, dry conditions in Catskill lakes. The transition from fen to bog conditions occurred about 4.2 cal ka, coincident with even lower lake levels in the Finger Lakes and warm but wet conditions in the Catskills. Smaller-scale fluctuations in water-level were inferred using Ti, Mn/Fe and Ca/Ti.