Atypical δ15N variations at the southern boundary of the East Pacific oxygen minimum zone over the last 50 ka

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doi: 10.1016/j.quascirev.2006.04.009
Author(s): Martinez, Philippe; Lamy, Frank; Robinson, Rebecca R.; Pichevin, Laetitia; Billy, Isabelle
Author Affiliation(s): Primary:
Université Bordeaux I, EPOC, Talence, France
GeoForschungsZentrum Potsdam, Federal Republic of Germany
University of Rhode Island, United States
University of Edinburgh, United Kingdom
Volume Title: Quaternary Science Reviews
Source: Quaternary Science Reviews, 25(21-22), p.3017-3028. Publisher: Elsevier, International. ISSN: 0277-3791
Note: In English. 59 refs.; illus., incl. sketch map
Summary: We report a nitrogen isotope record (ODP Site 1233) from the southern Chile margin at 41°S. The site is located slightly south of the southern boundary of the Peru-Chile upwelling system and the associated oxygen minimum zone off Peru and northern Chile. We show that our nitrogen isotope record, from the time interval 0-50 calendar kiloyears before present (ka B.P.), bears an atypical pattern both in shape and timing when compared with records obtained from either the continental margin of the eastern Pacific or the Subantarctic Zone (SAZ) of the Southern Ocean. The δ15N values at Site 1233 are relatively high throughout the record, varying between 9 ppm and 13 ppm. The major features are a pronounced δ15N increase at the beginning of the deglaciation, a maximum from 19 to 10 ka B.P.; thereafter a large decrease during the early Holocene, and millenial scale oscillations showing an Antarctic timing. We propose that the record results from an amalgam of low-latitude and high-latitude processes. Low-latitude processes, including a stronger advection signal of heavy nitrates from the denitrifying zones off Peru and northern Chile, would explain the timing of the deglaciation rise and the heaviest values found over this interval, excluding the Antarctic Cold Reversal period. The overall differences between site 1233 and records from Peru and northwest American margins suggest however that the origin of the δ15N signal off Chile is largely controlled by hydrologic and climatic changes in the Southern Ocean. We propose that the interplay between nutrient demand in the SAZ and latitudinal shifts of hydrologic fronts controlled both the concentrations and the isotopic signature of the remaining nitrate delivered to the Chile margin. Then, the glacial surface waters of the southern Chile margin were likely lower in nitrate concentration and bear a higher δ15N than during interglacial periods. Abstract Copyright (2006) Elsevier, B.V.
Year of Publication: 2006
Research Program: ODP Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Biochemistry; Carbon sequestration; Cenozoic; Climate change; Continental margin; Cores; Denitrification; East Pacific; Holocene; Hydrology; Isotope ratios; Isotopes; Leg 202; Marine sediments; N-15; N-15/N-14; Nitrogen; ODP Site 1233; Ocean Drilling Program; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Pleistocene; Productivity; Quaternary; Sediments; South Pacific; Southeast Pacific; Stable isotopes; Upper Pleistocene
Coordinates: S410000 S410000 W0742700 W0742700
Record ID: 2010003384
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands