T157 New Voices in Geobiology (Posters)

Monday, 23 October 2017
9:00 AM - 6:30 PM
Halls 4EF

SEPARATION AND ISOTOPIC ANALYSIS OF FRAMBOIDAL PYRITES FROM MEROMICTIC FAYETTEVILLE GREEN LAKE, NY

Paper number: T157-16
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Changes in ocean redox throughout Earth history have been examined and evaluated using sulfur isotope measurements (δ34S) of both pyrite and calcite-associated sulfate. During intervals of ocean euxinia, rapid changes in δ34S of pyrites are often observed but the underlying dynamics of these changes remain incompletely understood. Difficulty in interpreting such rapid, high amplitude changes may result from the presence of both syngenetic water column pyrites and diagenetic sedimentary pyrites in traditional bulk δ34S measurements. The aim of this work is to examine the relationship between framboid diameter and δ34S in a modern euxinic analog to examine the extent to which sedimentary δ34Spyrite reflects water column versus sedimentary sulfide composition. Here, we measure the δ34S of framboidal pyrites isolated from sediments collected from depths above, at, and below the chemocline in meromictic Fayetteville Green Lake (FGL, New York). Density separation was used to separate pyrites from other sediment components. Pyrite yields from density separation of standard samples with known pyrite abundance were improved from ~20% up to a maximum of approximately 80%. These revised separation and sample preparation methods improved our ability to measure pyrites via SEM and measure δ34S of individual framboids via SIMS. This high-resolution S isotope approach may improve our understanding of pyrite formation and preservation in FGL as well as in euxinic intervals of the rock record.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-304946

© Copyright 2017 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.