28 Undergraduate Research Poster Session II (Posters)

Saturday, 18 March 2023
8:00 AM - 12:00 PM
Grand Ballroom A–D

PALEOENVIRONMENTAL RECONSTRUCTION OF MENDON PONDS PARK, NY THROUGH HIGH RESOLUTION X-RAY FLUORESCENCE AND LOSS-ON-IGNITION ANALYSES

Paper number: 28-20
Program: Theme Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

High-resolution geochemical records from a small, shallow, pond in western New York were used to investigate its post-glacial and Holocene environmental history. We collected a ~7-m long core from the wetland fringe of Deep Pond that spans the last ~13 ka. We identified five lithofacies on the basis of visual core description, magnetic susceptibility (MS), m-XRF core scanning, loss-on-ignition, and smear slides. Unit 1, a basal silty clay, reflects deposition of primarily clastic sediment in a deep proglacial lake. High MS, high % lithogenous, high Ti and K, and low concentrations of Zr/Rb confirms clay-sized phyllosilicates and silt-sized quartz dominates. A rapid transition to unit 2, a silty carbonate unit with scattered mollusks, is coincident with a dramatic drop in MS, % lithogenous, Ti and Zr and rise in % carbonate, Ca/Ti, % organic matter, and Zr/Rb. The abrupt transition between units 1 and 2 likely signals a hiatus followed by a period of reduced erosion in the watershed, perhaps because the landscape became more vegetated based on pollen records from a neighboring kettle lake. The transition to unit 3, comprised of interbedded carbonate mud with abundant mollusks and sapropel, was gradual. Higher Zr/Rb in unit 3 suggests the aquatic system became shallower as coarser grained sediment, silt- and sand-sized siliciclastic sediment, accumulated. Overall, siliciclastic inputs continued to decrease as evident from the decline in MS, % lithogenous, and Ti. Ca/Ti and % carbonate values are high, indicative of calcite precipitation in the lake-water column. Higher % organic matter and Si/Ti values suggest higher levels of primary productivity, including diatoms, increased during this interval. It is possible that higher Mn/Ti indicates Mn mobilization and precipitation as a result of changes in oxic-anoxic conditions at the sediment-water interface. Unit 4 (sapropel) and unit 5 (peat) signal a transition to predominantly organic-sediment deposition. The % organic matter steadily increased up-core. The overall shift in sediment composition reflects the progressive in-filling of the water body since ~13 ka. Superimposed on this gradual trend are variations in Ti, Ca/Ti, and Zr/Rb. These likely reflect changes in sediment influx, likely from changes in precipitation and runoff.

Geological Society of America Abstracts with Programs. Vol. 55, No. 2

doi: 10.1130/abs/2023SE-385457

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