Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Molybdenum speciation as a paleo-redox proxy; a case study from Late Cretaceous Western Interior Seaway black shales

Allyson Tessin, Anthony Chappaz, Ingrid Hendy and Nathan D. Sheldon
Molybdenum speciation as a paleo-redox proxy; a case study from Late Cretaceous Western Interior Seaway black shales
Geology (Boulder) (November 2018) 47 (1): 59-62

Abstract

Molybdenum (Mo) geochemistry is widely used to reconstruct ocean oxygenation throughout Earth's history. However, gaps in our fundamental knowledge of Mo burial within sediments hinder the utility of Mo as a proxy for paleo-redox reconstruction. To improve our understanding of Mo burial pathways and sedimentary Mo speciation, we present combined geochemical analysis and X-ray absorption fine structure spectroscopy from black shales deposited in the North American Western Interior Seaway (WIS) during the Late Cretaceous. Molybdenum was present in multiple phases during deposition of the black shales, probably as a combination of Mo(IV) and Mo(VI) species with no more than 54% of Mo associated with Mo-sulfide phases. These Mo molecular geochemistry results indicate that sediments were not deposited under permanent euxinic conditions, but rather weakly euxinic, periodically euxinic, or anoxic conditions (with sulfide restricted to pore waters). This is the case even in samples where other redox indicators would indicate strongly euxinic conditions. Additionally, differences in Mo speciation between our two localities highlight variability in the intensity of oxygen limitation within the WIS, providing a more nuanced redox reconstruction from sections deposited in conditions between weakly and strongly euxinic, suggesting that Mo molecular geochemistry may allow for more detailed spatial reconstructions of past stratified anoxic basins and oxygen minimum zones.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 47
Serial Issue: 1
Title: Molybdenum speciation as a paleo-redox proxy; a case study from Late Cretaceous Western Interior Seaway black shales
Affiliation: University of Michigan, Department of Earth and Environmental Sciences, Ann Arbor, MI, United States
Pages: 59-62
Published: 20181130
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 28
Accession Number: 2019-007030
Categories: StratigraphyGeochemistry of rocks, soils, and sediments
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2019023
Illustration Description: illus. incl. 1 table, sketch map
N38°28'60" - N38°28'60", W101°58'00" - W101°58'00"
N38°22'60" - N38°22'60", W105°01'00" - W105°01'00"
Secondary Affiliation: Central Michigan University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201906
Close Modal

or Create an Account

Close Modal
Close Modal