{"681784":{"#nid":"681784","#data":{"type":"event","title":"EAS Specially Invited Speaker - Dr. Itay Halevy","body":[{"value":"\u003Cp\u003EFe and S isotope ratios in sedimentary pyrite (\u03b456Fepyr and \u03b434Spyr) are extensively used in reconstructions of the coupled biogeochemical Fe, S, C and O2 cycles and investigations of sub-seafloor microbial activity. However, an underlying assumption that \u03b434Spyr variation is related to global S-cycle drivers is refuted by a growing number of observations. To elucidate the controls on \u03b456Fepyr and \u03b434Spyr values, we combine (i) bulk and microscale multi-isotope (Fe and multi-S) analyses of well-understood Pleistocene marine sediments, and (ii) a coupled microbial-diagenetic model, which accounts for the transport and (bio)reaction of C, S and Fe species.\u003C\/p\u003E\u003Cp\u003ERather than global Fe-cycle and S-cycle drivers of isotopic variation, the studied sediment cores demonstrate clear controls by local variations in depositional parameters like the sedimentation rate, organic matter and reactive Fe content, and reworking by currents. Incorporating these insights into a microbial-diagenetic model, and using gridded datasets of the relevant depositional factors, we reproduce modern \u03b434Spyr spatial patterns and distributions compiled from the sedimentary rock record. In agreement with the bulk and microscale observations, the model microbial S isotope fractionation remains uniformly large under modern marine conditions, and the main determinants of isotopic variations in pyrite are the depositional parameters. These factors govern the degree of sulfate drawdown and isotopic distillation, and the degree of porewater sulfide accumulation, and through these, the distribution of \u03b434Spyr.\u003C\/p\u003E\u003Cp\u003EWith the understanding that mostly local depositional parameters control the isotopic composition of pyrite, coupled \u03b456Fepyr, \u03b434Spyr and \u003Cstrong\u003E\u0394\u003C\/strong\u003E33Spyr measurements by secondary-ion mass spectrometry (SIMS) offer a way forward. Such measurements provide a wealth of information about microbial activity, pyritization pathways, burial diagenesis and the dynamics of the depositional system.\u003C\/p\u003E","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EFe and S isotope ratios in sedimentary pyrite (\u03b456Fepyr and \u03b434Spyr) are extensively used in reconstructions of the coupled biogeochemical Fe, S, C and O2 cycles and investigations of sub-seafloor microbial activity. However, an underlying assumption that \u03b434Spyr variation is related to global S-cycle drivers is refuted by a growing number of observations. To elucidate the controls on \u03b456Fepyr and \u03b434Spyr values, we combine (i) bulk and microscale multi-isotope (Fe and multi-S) analyses of well-understood Pleistocene marine sediments, and (ii) a coupled microbial-diagenetic model, which accounts for the transport and (bio)reaction of C, S and Fe species.\u003C\/p\u003E\u003Cp\u003ERather than global Fe-cycle and S-cycle drivers of isotopic variation, the studied sediment cores demonstrate clear controls by local variations in depositional parameters like the sedimentation rate, organic matter and reactive Fe content, and reworking by currents. Incorporating these insights into a microbial-diagenetic model, and using gridded datasets of the relevant depositional factors, we reproduce modern \u03b434Spyr spatial patterns and distributions compiled from the sedimentary rock record. In agreement with the bulk and microscale observations, the model microbial S isotope fractionation remains uniformly large under modern marine conditions, and the main determinants of isotopic variations in pyrite are the depositional parameters. These factors govern the degree of sulfate drawdown and isotopic distillation, and the degree of porewater sulfide accumulation, and through these, the distribution of \u03b434Spyr.\u003C\/p\u003E\u003Cp\u003EWith the understanding that mostly local depositional parameters control the isotopic composition of pyrite, coupled \u03b456Fepyr, \u03b434Spyr and \u003Cstrong\u003E\u0394\u003C\/strong\u003E33Spyr measurements by secondary-ion mass spectrometry (SIMS) offer a way forward. Such measurements provide a wealth of information about microbial activity, pyritization pathways, burial diagenesis and the dynamics of the depositional system.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Sedimentary Fe and S Isotope Records Encode a Complex Suite of Local to Global Processes"}],"uid":"36678","created_gmt":"2025-04-15 12:36:07","changed_gmt":"2025-04-15 14:45:17","author":"tbuchanan9","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2025-04-21T14:00:00-04:00","event_time_end":"2025-04-21T15:00:00-04:00","event_time_end_last":"2025-04-21T15:00:00-04:00","gmt_time_start":"2025-04-21 18:00:00","gmt_time_end":"2025-04-21 19:00:00","gmt_time_end_last":"2025-04-21 19:00:00","rrule":null,"timezone":"America\/New_York"},"location":"ES\u0026T 1177","extras":[],"hg_media":{"676839":{"id":"676839","type":"image","title":"Halevy Headshot.png","body":null,"created":"1744720818","gmt_created":"2025-04-15 12:40:18","changed":"1744720818","gmt_changed":"2025-04-15 12:40:18","alt":"Halevy Headshot.png","file":{"fid":"260684","name":"Halevy---Headshot.png","image_path":"\/sites\/default\/files\/2025\/04\/15\/Halevy---Headshot.png","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/2025\/04\/15\/Halevy---Headshot.png","mime":"image\/png","size":5149911,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/2025\/04\/15\/Halevy---Headshot.png?itok=AYDzywIe"}}},"media_ids":["676839"],"groups":[{"id":"364801","name":"School of Earth and Atmospheric Sciences (EAS)"}],"categories":[],"keywords":[{"id":"175623","name":"EAS Seminar"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}