Sulfur diagenesis and burial on the Amazon shelf: Major control by physical sedimentation processes

Robert C. Aller*, Neal E. Blair

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

Early diagenetic properties of Amazon shelf muds are dominated by nonsulfidic Fe and Mn cycling, resulting in relatively little S deposition compared to previously studied marine margin environments. Despite abundant potential reactants typical of sulfidic deposits, authigenic sulfides represent only ∼10% of diagenetically reduced Fe, and DOP (degree of pyritization) is only ∼0.02. The average C/S (wt wt-1) ratio of buried sediment below the zone of SO42- reduction is ∼7.4, ∼2.6 times more than the commonly assumed modern shelf average of ∼2.8. The deltaic burial rate for ∑S is ∼0.65 × 106 tons yr-1. Relatively low ∑S deposition is promoted by terrestrial weathering that delivers reactive oxide debris, but apparently depends most strongly on reoxidation and rapid burial by intense physical reworking and fluid-mud formation. Diagenetic models of S distributions demonstrate rapid sediment reworking (∼10-100 cm yr-1 as apparent advection), substantial ∑S reoxidation (84-98%), and in one case, massive sediment deposition of up to ∼5 m of sediment in ∼1 year. Extremely low DOP coupled with dominance by nonsulfidic reduced-Fe minerals and lack of biogenic sedimentary structures may be an indicator in marine organic-rich muds of intense physical reworking under oxygenated waters.

Original languageEnglish (US)
Pages (from-to)3-10
Number of pages8
JournalGeo-Marine Letters
Volume16
Issue number1
DOIs
StatePublished - Jan 1 1996

ASJC Scopus subject areas

  • Oceanography
  • Environmental Science (miscellaneous)
  • Geotechnical Engineering and Engineering Geology
  • Earth and Planetary Sciences (miscellaneous)

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