SULFUR ISOTOPIC TRENDS AND PATHWAYS OF IRON SULFIDE FORMATION IN UPPER HOLOCENE SEDIMENTS OF THE ANOXIC BLACK SEA

Abstract

Down-core trends for extents of iron sulfidation in upper Holocene microlaminated deposits of the Black Sea abyssal plain imply that most of the pyrite in these sediments is formed in the sulfidic water column and/or very close to the sediment-water interface. Sulfur isotopic data for pyrite within microlaminated muds from two localities in the deep basin show striking uniformity between sites and down core, with a mean δ³⁴SCDT value of −37.2 ± 0.9‰ (1σ, n = 18). These isotopic trends support the hypothesis of early pyrite formation.