Formation and preservation of greigite (Fe3S4) in sediments from the Santa Barbara Basin: implications for paleoenvironmental changes during the past 35 ka.

Blanchet, Cécile, Thouveny, N. and Vidal, L. (2009) Formation and preservation of greigite (Fe3S4) in sediments from the Santa Barbara Basin: implications for paleoenvironmental changes during the past 35 ka. Open Access Paleoceanography, 24 (PA2224). DOI 10.1029/2008PA001719.

[img]
Preview
Text
805_Blanchet_2009_FormationAndPreservationOfGreigite_Artzeit_pubid12411.pdf - Published Version

Download (1630Kb)

Supplementary data:

Abstract

Diagenetic processes are known to modify sedimentary records, but they can also reveal important
paleoenvironmental changes. Here we investigate variations in sedimentary iron diagenesis and depositional
environments for the last 35 ka by analyzing the rock magnetic and geochemical properties of two sediment
cores collected in the Santa Barbara Basin (California). In organic-rich sediments, early diagenesis often leads to
partial dissolution of detrital iron oxides and stepwise formation of authigenic pyrite (FeS2). The pyritization
process takes place following several geochemical pathways, sometimes involving intermediate iron sulfide
species such as greigite (Fe3S4). Sedimentary conditions in the basin appear to have recurrently favored
preservation of greigite (identified by its magnetic properties) and inhibited its complete transformation into
pyrite. The Holocene interval contains a series of centimeter-thick greigite-bearing layers that are associated
with large flood deposits, which are known in the basin as ‘‘gray layers.’’ We propose that greigite preservation
was enabled in these sediments by their relative enrichment in reactive iron over organic matter and/or hydrogen
sulfide (because of their high ratio of terrigenous over organic material), which limited pyritization reactions.
Within the glacial deposits, formation and preservation of meter-thick greigite layers occurred in terrigenous-rich
and organic-poor sedimentary layers and is proposed to result from a similar diagenetic process to that in the
Holocene greigite-bearing layers (dominance of reactive iron over organic matter and/or HS�). The terrigenous
enrichments in the glacial greigite-bearing layers are probably related to climatic or sea level changes because
they occur at times of massive iceberg releases in the North Atlantic, the so-called Heinrich events.

Document Type: Article
Keywords: greigite, Diagenesis, Paleoenvironment, terrigenous input, Energie- und CO2-Deponierungstechnologien
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2008PA001719
ISSN: 0883-8305
Date Deposited: 11 Nov 2009 12:56
Last Modified: 10 May 2017 08:02
URI: http://oceanrep.geomar.de/id/eprint/4535

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...