278 Understanding Temporal Dynamics in Hydrogeochemistry and Sedimentary Processes in Estuarine Environments

This session explores temporal changes in estuarine environments with respect to water chemistry and sediment inputs. Effects of evolving physiochemical properties and isotopic composition of water, as well as the geochemical attributes of sediments on the environment will be presented.

Wednesday, 22 October 2025
1:30 PM - 5:30 PM
HBGCC, 213AB

Decoding palynodebris, C/N, diatoms, and pollen sediment sources in the Lake Erie: Insights from pre-Columbian deforestation and hydrological change

Paper number: 278-4
Program: Technical Sessions
Time: 2:25 PM – 2:45 PM

Authors

Abstract

This study provides pollen and the first palynodebris (phytoclasts, amorphous organic matter, and non-pollen palynomorphs) records in a dated, 10 m core, 84A, from Lake Erie’s central basin to establish a record of regional climate, water sources, and their relationship to lake levels. Cluster analysis of pollen, spores, diatoms, phytoclasts, and amorphous organic matter identified 4 zones. The zone boundaries correspond to changes in C/N, and to time periods where geomorphologic evidence indicates changes in lake level. Zone I, between 800-1000 cm (~11000-15000 cal Yr. BP), features the highest abundances of Picea and trilete spores (mostly Sphagnaceae), as well as the highest C/N, being consistent with old age and cold conditions. These findings confirm the early Holocene age for the zone despite anomalously young radiocarbon ages (~5,000 cal Yr. BP) below the zone in the bottom 20 cm of the core. Zone II, from 800-550 cm (~8,000-5,000 cal Yr. BP) has higher abundances of Quercus, Acer, and Salix consistent with warmer middle Holocene climate. Zone III from 550-250 cm (~5,000-2,000 cal Yr. BP) is similar to Zone II in tree and grass pollen and fern spores but has a higher proportion of small, equant opaque phytoclasts relative to larger, lath-shaped opaque phytoclasts. The Zone II-Zone III boundary corresponds to an increase in C/N, which may have been controlled by increased erosion of glacial till bluffs driven by a water level rise related to the influx of Upper Great Lakes water; the change in phytoclast size and shape may reflect a longer transport distance associated with this influx. While diatoms in most samples were apparently lost to dissolution, we did find diatoms (Aulacoseira granulata, Stephanodiscus niagarae, and Gyrosigma sp.) < 200 cm (~2000 cal yBP).  The diatoms may have persisted because of their thick silicification. Their formation may have required elevated silicon/phosphorous. In addition, their presence indicates a unique tolerance of these species over the lake chemistry and need for further study. This also, correspond with increase in Ambrosia, palynodebris, and other indicators of disturbance taxa in Zone IV (<350 cm and ~2000 cal Yr. BP) and may record anthropogenic deforestation associated with early stages of development of pre-Columbian agriculture.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412129

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