June 21, 2019

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Nathan Schachtman Coauthored a Paper on Physical and Chemical Erosion in the Geological Society of America

Nathan Schachtman coauthored a paper entitled "The Interplay between Physical and Chemical Erosion Over Glacial-Interglacial Cycles" that was published in the Geological Society of America's journal Geology on May 2, 2019.

Nathan was the lead author, and his coauthors were Joshua Roering, Jill Marshall, Daniel Gavin, and Darryl Granger.

Nathan is a Staff Geologist based in Washington focused on geological sciences. He has experience conducting geochemical characterizations of soil, rock, and sediment as well as preparing samples for geochemical analyses, including XRF, XRD, cosmogenic/meteoric Be, and organic/inorganic carbon. Nathan has led multiple field exploration and sampling campaigns, with a focus on lake core and sediment extraction.

The mission of the Geological Society of America is to advance geoscience research and discovery, service to society, stewardship of Earth, and the geosciences profession. Their vision is to be the premier geological society supporting the global community in scientific discovery, communication, and application of geoscience knowledge.


Mineral dissolution rates in the critical zone (CZ) depend on physical, chemical, and biotic processes, although the means by which climate variations regulate the relative importance of these processes remain ambiguous. We analyzed trace-element and bulk chemical concentrations in a 50 k.y. sedimentary archive at our unglaciated, mid-latitude study area to show that glacial-interglacial transitions generate systematic and offsetting variations in chemical weathering intensity and denudation. The transition from cool and wet to colder and drier conditions prior to the Last Glacial (LG) coincides with a monotonic decline in chemical alteration, estimated by the chemical depletion fraction (CDF), and an increase in denudation rate, estimated from in situ 10Be. During the cold and sparsely forested LG (29–14 ka), we observe low CDF values (<0.1) and rapid denudation (>0.22 mm yr–1), consistent with increased physical weathering and soil transport by periglacial processes. Conversely, slower denudation (~0.1 mm yr–1) and higher CDF values (~0.25) characterize the warm and densely vegetated late Holocene. These opposing trends in chemical depletion and denudation rate imply relatively consistent chemical weather­ing fluxes during Quaternary climate extremes, despite significant variations in temperature and vegetation. Additionally, our observations of weakly altered LG lake sediments and highly altered modern soils and shallow bedrock imply substantial post-LG alteration and deepening of the CZ. Our novel approach and results demonstrate how changes in the efficacy of abiotic and biotic processes modulate the CZ and reveal the influence of past climates on modern CZ characteristics.

More Information

Learn more about the article: "The Interplay between Physical and Chemical Erosion Over Glacial-Interglacial Cycles."
Learn more about the Geological Society of America: https://www.geosociety.org/gsa.
For consultation regarding Physical and Chemical Erosion Over Glacial-Interglacial Cycles, contact Nathan Schachtman at This email address is being protected from spambots. You need JavaScript enabled to view it..
Learn more about Nathan Schachtman at: https://www.linkedin.com/in/nathan-schachtman-176b4784/.