Analyzing the Effects of Grain Size on Activation Energy in Antarctic Margin Sediments
Abstract
Modeling the last deglaciation in Antarctica requires accurate radiocarbon dates because sediments collected from the Antarctic margin are depauperate in biogenic carbonate, research relies on bulk acid-insoluble organic matter (AIOM) for radiocarbon dating. These dates, however, are often inaccurate due to deposition of older organic carbon driving the AIOM date older than the true depositional age of the sediments. Alternative methods of radiocarbon dating, like Ramped PyrOx, are necessary to provide more accurate dates and insight into rates of the last natural glacial retreat to assess current warming trends. Here, we focus on understanding the kinetics of Ramped PyrOx sample preparation to improve radiocarbon dating. We analyzed grain size distribution and corresponding Ramped PyrOx samples to assess any relationships between grain size and the activation energy distribution (or bond strength) of each Ramped PyrOx temperature interval. We analyzed sediments from two cores from the Anvers Trough of the West Antarctic Peninsula and targeted the laminated diatom ooze and silt units. This sedimentary unit represents a glacial retreat and the transition from subglacial/ice proximal to seasonally open ocean depositional environments. We were able to sample from several diatom ooze and silt couplets to compare the results between the sediment horizons. We test the null hypothesis that there is no relationship between activation energy and grain size. Regardless of whether we refute that hypothesis or not, we observe a difference between the activation energy distributions of silt and ooze layers of the laminated sediment facies typically overlying glacial diamict on the Antarctic margins. In comparing these distributions to compound specific diatom radiocarbon dates, we hypothesize that the diatom-bound organic carbon is pyrolyzing at higher temperatures than previously thought. These findings improve our overall understanding of radiocarbon ages generated via Ramped PyrOx sample preparation methods and provide an important avenue to investigate in future studies.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP41B1545D
- Keywords:
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- 0424 Biosignatures and proxies;
- BIOGEOSCIENCES;
- 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES