https://scholars.lib.ntu.edu.tw/handle/123456789/571632
標題: | Ice Age-Holocene Similarity of Foraminifera-Bound Nitrogen Isotope Ratios in the Eastern Equatorial Pacific | 作者: | Studer A.S Mekik F Ren H Hain M.P Oleynik S Mart?nez-Garc?a A Haug G.H Sigman D.M. HAO-JIA REN |
關鍵字: | deglaciation; denitrification; diagenesis; foraminifera; Holocene; Last Glacial Maximum; nitrogen isotope; Pleistocene; sediment core; Pacific Ocean; Pacific Ocean (Tropical); Foraminifera; Neogloboquadrina dutertrei; Neogloboquadrina incompta | 公開日期: | 2021 | 卷: | 36 | 期: | 5 | 來源出版物: | Paleoceanography and Paleoclimatology | 摘要: | Bulk sediment δ15N records from the eastern tropical Pacific (ETP) extending back to the last ice age most often show low glacial δ15N, then a deglacial δ15N maximum, followed by a gradual decline to a late Holocene δ15N that is typically higher than that of the Last Glacial Maximum (LGM). The lower δ15N of the LGM has been interpreted to reflect an ice age reduction in water column denitrification. We report foraminifera shell-bound nitrogen isotope (FB-δ15N) measurements for the two species Neogloboquadrina dutertrei and Neogloboquadrina incompta over the last 35?ka in two sediment cores from the eastern equatorial Pacific (EEP), both of which have the typical LGM-to-Holocene increase in bulk sediment δ15N. FB-δ15N contrasts with bulk sediment δ15N by not indicating a lower δ15N during the LGM. Instead, the FB-δ15N records are dominated by a deglacial δ15N maximum, with comparable LGM and Holocene values. The lower LGM δ15N of the bulk sediment records may be an artifact, possibly related to greater exogenous N inputs and/or weaker sedimentary diagenesis during the LGM. The new data raise the possibility that the previously inferred glacial reduction in ETP water column denitrification was incorrect. A review of reconstructed ice age conditions and geochemical box model output provides mechanistic support for this possibility. However, equatorial ocean circulation and nitrate-rich surface water overlying both core sites allow for other possible interpretations, calling for replication at non-equatorial ETP sites. ? 2021. The Authors. |
URI: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-85106695096&doi=10.1029%2f2020PA004063&partnerID=40&md5=c1a20ecfe40ee51028c4fdb93da1bf20 https://scholars.lib.ntu.edu.tw/handle/123456789/571632 |
ISSN: | 25724517 | DOI: | 10.1029/2020PA004063 |
顯示於: | 地質科學系 |
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