Productivity patterns and N-fixation associated with Pliocene-Holocene sapropels; paleoceanographic and paleoecological significance

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doi: 10.5194/bg-8-415-2011
Author(s): Gallego-Torres, David; Martinez-Ruiz, Francisca; Meyers, P. A.; Paytan, A.; Jimenez-Espejo, Francisco J.; Ortega-Huertas, Miguel
Author Affiliation(s): Primary:
Utrecht University, Faculty of Geosciences, Utrecht, Netherlands
Other:
CSIC-Universidad de Granada, Spain
University of Michigan, United States
University of California, Santa Cruz, United States
Volume Title: Biogeosciences
Source: Biogeosciences, 8(2), p.415-431. Publisher: Copernicus GmbH on behalf of the European Union, Katlenburg-Lindau, International. ISSN: 1726-4170
Note: In English. Includes supplement, http://www.biogeosciences.net/8/415/2011/bg-8-415-2011-supplement.pdf; published in Biogeosciences Discussion: 11 June 2010, http://www.biogeosciences-discuss.net/7/4463/2010/bgd-7-4463-2010.html; accessed in Jan., 2012. 99 refs.; illus., incl. 1 table, sketch map
Summary: We have studied a suite of 35 sapropel sequences from a transect of four ODP sites across the Eastern Mediterranean to explore for paleoproductivity patterns and provide new insights on ecological changes during their deposition. Paleoproductivity variations were identified using TOC and Babio mass accumulation rates and δ15Ntotal and δ13Corg values. Elevated Ba/Al and TOC mass accumulation rates record periods of basin-wide amplified productivity. Our data further support that sapropels were formed by cyclic increases in primary production of marine organic matter largely sustained by N-fixing bacteria. This productivity increase was triggered by climate factors leading to increased fluvial discharge and amplified nutrient input that also favored the establishment of N-fixing bacteria. Enhanced productivity led to depletion of deepwater dissolved oxygen and consequently improved organic matter preservation. Primary production was more intense during the middle to Late Pleistocene compared to Pliocene equivalents, coinciding with increasing total sedimentation rates. δ15N values are dramatically lower in the sapropels than in TOC-poor background sediments, indicating a major contribution from nitrogen-fixing bacteria to the higher productivity during sapropel deposition. Additionally, different degrees of denitrification occurred as a consequence of water column oxygenation which in turns evolved from stagnant anoxic bottom waters during Pliocene sapropels to oxygen depleted and sluggish circulation in late Quaternary layers. These differences between sapropel layers provide new evidences for the general evolution of the Eastern Mediterranean basin during the last 3 Mys in terms of paleoceanographic conditions and the intensity of climate variability leading to sapropel deposition.
Year of Publication: 2011
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Alkaline earth metals; Barium; Biogenic processes; Bottom water; C-13/C-12; Carbon; Cenozoic; Denitrification; East Mediterranean; Holocene; Ionian Sea; Isotope ratios; Isotopes; Leg 160; Levantine Basin; Mediterranean Ridge; Mediterranean Sea; Metals; N-15; Neogene; Nitrogen; ODP Site 964; ODP Site 966; ODP Site 967; ODP Site 969; Ocean Drilling Program; Oceanic anoxic events; Organic compounds; Paleo-oceanography; Paleoecology; Pliocene; Quaternary; Sapropel; Sedimentation; Sedimentation rates; Stable isotopes; Sulfates; Tertiary; Total organic carbon; Upper Quaternary
Coordinates: N334212 N370209 E0324513 E0131040
Record ID: 2013024304
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Copernicus Gesellschaft, Katlenburg-Lindau, Germany