Agreement of bulk sedimentary and foraminifera-bound nitrogen in the detection of a 4 million year trend in equatorial Pacific N isotopes (δ15N)
Abstract
The potential for isotopic fractionation of sedimentary organic matter during sedimentary diagenesis or contamination by exogenous material has led researchers to measure the nitrogen (N) isotopic composition (δ15N) of microfossils such as foraminifera and diatoms. However, sediments underlying important ocean study sites—such as the equatorial Pacific—often have poorly preserved foraminifera and a mixture of diatoms and other opal making it difficult to target these archives for δ15N analysis. Here we compare 4 million year long records of bulk sediment δ15N from the eastern and western equatorial Pacific with both low- and high-resolution foraminifera δ15N measurements. We find that the long-term trends in bulk sediment δ15N compare well with the foram-bound δ15N measurements, with known species-specific offsets between the foram- and bulk sediment records. We explore several potential explanations for differences between the bulk and foram-bound δ15N measurements at higher resolution including variability of the microfossil assemblage and the influence of exogenous N.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP21D1631R
- Keywords:
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- 0419 Biomineralization;
- BIOGEOSCIENCES;
- 0454 Isotopic composition and chemistry;
- BIOGEOSCIENCES;
- 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES;
- 4994 Instruments and techniques;
- PALEOCEANOGRAPHY