Open AccessBiogeochemical changes within the Benguela Current upwelling system during the Matuyama Diatom Maximum: Nitrogen isotope evidence from Ocean Drilling Program Sites 1082 and 1084
Author(s) -
Robinson Rebecca S.,
Meyers Philip A.
Publication year - 2002
Publication title -
paleoceanography
Language(s) - English
Resource type - Journals
eISSN - 1944-9186
pISSN - 0883-8305
DOI - 10.1029/2001pa000659
Subject(s) - upwelling , oceanography , biogeochemical cycle , geology , diatom , nitrate , biogeochemistry , sediment , total organic carbon , oxygen minimum zone , paleontology , ecology , environmental chemistry , chemistry , biology
The Matuyama Diatom Maximum (MDM) is a time of peak opal accumulation from 2.6 to ∼2.0 Ma within the Benguela Current upwelling system that was initiated by increased influence of Southern Ocean water on the eastern South Atlantic. We measured opal, total organic carbon (TOC), and CaCO 3 fluxes and C and N stable isotopes in sediments deposited from 2.4 to 1.95 Ma at Sites 1082 and 1084 to explore the biogeochemical dynamics within the Benguela region. The infusion of Southern Ocean water delivered dissolved nutrients and Southern Ocean flora and fauna, resulting in local opal accumulation increasing up to 8 g/cm 2 ky and the production of diatom mats. Some δ 15 N measurements of diatom‐bound organic matter indicate that the mats grew within the Benguela region. The bulk sediment δ 15 N records are taken to reflect changes in the δ 15 N of nitrate in the incoming water, where lower values at 2.4 Ma reflect less nitrate utilization in the Antarctic. A long‐term increase in relative nitrate uptake in the Southern Ocean is evidenced by the gradual increase in δ 15 N toward 1.9 Ma.