Holocene records of chlorin N isotopes

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doi: 10.1180/minmag.2013.077.5.8
Author(s): Higgins, Meytal B.; Robinson, Rebecca S.; Pearson, Ann
Author Affiliation(s): Primary:
Princeton University, Department of Geosciences, Princeton, NJ, United States
University of Rhode Island, United States
Harvard University, United States
Volume Title: Goldschmidt abstracts 2013
Source: Mineralogical Magazine, 77(5), p.1299; Goldschmidt 2013, Florence, Italy, Aug. 25-30, 2013. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0026-461X CODEN: MNLMBB
Note: In English
Summary: Nitrogen isotope ratios measured in sedimentary chlorophyll degradation products provide a diagenetically unaltered signal of the marine nitrogen cycle during deposition. Additionally, due to taxonomic differences in fractionation associated with chlorophyll biosynthesis, these records can be used to reconstruct the cyanobacterial contribution to buried organic matter. If diazotrophic cyanobacterial contribution to biomass increases during enhanced N2 fixation, then chlorin N isotope records may provide an additional constraint on the importance of this source of N to surface waters in the geologic past. We reconstructed low resolution records of chlorin δ15N values from the last glacial maximum to recent sediments in four oceanographically distinct settings. Samples were taken from ODP sites 1234 (Chile Margin), 1237 (Nazca Ridge, Peru), 1063 (Bermuda Rise), and core 17964 from the South China Sea. These four globally-distributed sites represent different nutrient regimes characterized by a wide range of modern P* values and potential rates of N2 fixation. Chlorin δ15N data were compared to new or previously published bulk N data to examine for diagenetic enrichment of bulk N (causing 15N offsets to increase) or cyaobacterial contribution to export (causing 15N offsets to decrease). Preliminary data show an average δ15N offset of ∼5-5.5ppm between bulk and chlorin N at all sites, suggesting predominantly algal export production irrespective of N2 fixation regime and bulk values of δ15N.
Year of Publication: 2013
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 24 Surficial Geology, Quaternary Geology; Atlantic Ocean; Bermuda Rise; Biogenic processes; Cenozoic; Chlorophyll; Cyanobacteria; Degradation; Diagenesis; East Pacific; Fixation; Holocene; Isotope ratios; Isotopes; Leg 172; Leg 202; N-15/N-14; Nazca Ridge; Nitrogen; North Atlantic; ODP Site 1063; ODP Site 1234; ODP Site 1237; Ocean Drilling Program; Organic compounds; Pacific Ocean; Pigments; Porphyrins; Quaternary; South Pacific; Southeast Pacific; Stable isotopes
Coordinates: S361300 S361300 W0734100 W0734100
N334111 N334111 W0573654 W0573654
S160000 S160000 W0762300 W0762300
Record ID: 2014025276
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland

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