Open AccessMid‐Miocene paleoproductivity in the Atlantic Ocean and implications for the global carbon cycle
Author(s) -
DiesterHaass Liselotte,
Billups Katharina,
Gröcke Darren R.,
François Louis,
Lefebvre Vincent,
Emeis Kay C.
Publication year - 2009
Publication title -
paleoceanography
Language(s) - English
Resource type - Journals
eISSN - 1944-9186
pISSN - 0883-8305
DOI - 10.1029/2008pa001605
Subject(s) - benthic zone , geology , oceanography , total organic carbon , carbon cycle , deep sea , sedimentary organic matter , sedimentary rock , productivity , organic matter , isotopes of carbon , carbon sequestration , carbonate , paleontology , carbon dioxide , ecosystem , environmental chemistry , ecology , chemistry , macroeconomics , organic chemistry , economics , biology
A prominent, middle Miocene (17.5–13.5 Ma) carbon isotope excursion ubiquitously recorded in carbonate sediments has been attributed to enhanced marine productivity and sequestration of 13 C depleted organic carbon in marine sediments or enhanced carbon burial in peat/lignite deposits on land. Here we test the hypothesis that the marine δ 13 C record reflects a change in productivity with proxy records from three Atlantic Ocean sites (Deep Sea Drilling Program Site 608 and Ocean Drilling Program Sites 925 and 1265). Our multiproxy approach is based on benthic foraminiferal accumulation rates, elemental ratios (Ba/Al and P/Al), the δ 13 C of bulk sedimentary organic matter, and dissolution indices. We compare these proxies to benthic foraminiferal δ 13 C values measured on the same samples. Our results indicate that marine paleoproductivity in the Atlantic Ocean is not related to the benthic foraminiferal δ 13 C excursion. A numerical box model confirms that marine productivity cannot account for the δ 13 C maximum. The model shows that sequestration of 1.5 × 10 18 mol C in the terrestrial realm over a period of 3 Ma leads to a 0.9‰ δ 13 C increase in the deep ocean, which is near the observed records. Therefore, an increase in continental organic carbon sequestration is the most plausible way to enrich the ocean's carbon pool with 13 C, which is consistent with coeval lignite deposits worldwide. The δ 13 C values of bulk sedimentary organic matter parallel the δ 13 C of dissolved inorganic carbon as reflected by benthic foraminiferal δ 13 C values suggesting no significant change in atmospheric p CO 2 levels over the investigated period.