24 Lake Sedimentary Records of Past Climate and Environment (Posters)

This session will focus on lacustrine archives and reconstructions of past environmental changes through the use of geochemical, biological, and sedimentological proxies. Both modern and paleo proxy datasets are welcome.

Monday, 23 March 2026
8:00 AM - 12:00 PM
CCC, Ballroom C

Using 15N as a Marker of the Anthropocene in the Northeast US

Paper number: 24-12
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Nitrogen is an essential nutrient in the biosphere, and anthropogenic activity has drastically altered N cycle processes and isotopic signals, especially through increased industrial activity, fossil fuel burning, and land use change. 15N within sedimentary records is influenced by inputs such as organic matter, vegetation, and fractionation during N cycle processes, and can be used to reconstruct environmental changes over various time scales. The northeast US provides an ideal location to investigate records of 15N as a signal of anthropogenic activity, as the region experienced widespread deforestation in the 18th–19th centuries primarily for agriculture, followed by reforestation in the late-19 through 20th centuries and then increased 20–21st century urbanization, while isolated areas continued to be used for agriculture. Here we present a regional compilation of δ15N in sediment cores in the northeast US across a variety of depositional environments (kettle ponds, wetlands, lakes, and reservoirs) that represent watersheds that underwent different types, durations, and intensities of historic land use to investigate how δ15N can be used as a marker of the Anthropocene. Background δ15N values are set by the environment (wetlands <0‰, lakes and kettle ponds 0–3‰), but regardless of background values, anthropogenic sediment shifts positive across all depositional environments and land use types. However, these changes are influenced by the type and duration of land use — sustained agriculture for >50–150 years leads to shifts by >2‰, while isolated deforestation for timber harvesting leads to shifts by <2‰. Increased usage of organic fertilizer or erosion of soils due to historic land use practices likely accounts for increased anthropogenic δ15N. Individual records suggest that discrepancies in the timing of the increase in δ15N may be related to geographic differences in timing of land use, however, better age constraints are needed to fully investigate these differences.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411369

© Copyright 2026 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.