Multiple negative molybdenum isotope excursions in the Doushantuo Formation (South China) fingerprint complex redox-related processes in the Ediacaran Nanhua Basin

Chadlin M. Ostrander, Swapan K. Sahoo, Brian Kendall, Ganqing Jiang, Noah J. Planavsky, Timothy W. Lyons, Sune G. Nielsen, Jeremy D. Owens, Gwyneth W. Gordon, Stephen J. Romaniello, Ariel D. Anbar

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

The Ediacaran Doushantuo Formation offers one of the most complete and extensively studied records of end-Neoproterozoic biotic and environmental change. Here, we report multiple coeval negative molybdenum (Mo) isotope excursions (to as low as δ98MoNIST+0.25 = −2.24 ± 0.10‰; 2SD) in shales from four separate sites in South China (Rongxi, Taoying, Wuhe, and Yuanjia) that preserve the Doushantuo Formation. The negative δ98Mo excursions appear coincident with previously discovered and seemingly peculiar redox-sensitive element (RSE) patterns in the same sedimentary rocks. We propose that these geochemical trends can be explained by some combination of (a) enhanced local marine oxygenation in the sedimentary basin where the Doushantuo Formation was originally deposited (the Nanhua Basin) and (b) changes in the degree of connectivity between this paleo basin and the open ocean. Enhanced local marine oxygenation, by exposing more sediments in the Nanhua basin to H2S-poor conditions, could have hindered quantitative tetrathiomolybdate formation within these sediments. Local marine oxygenation could have also stimulated the operation of a Mn oxide shuttle. Today, both of these processes are shown to promote the retention of lighter-mass Mo isotopes in sediments and also govern RSE enrichment patterns. Alternatively, or in addition, the Nanhua Basin may not have maintained an uninterrupted connection with the open ocean during the entirety of the Ediacaran Period. The negative δ98Mo excursions occur coincident with sea level highstands that could have also exposed more sediments in the basin to H2S poor conditions and/or catalyzed the operation of a local Mn oxide shuttle. When trying to infer temporal changes in ancient global ocean redox, it is important to consider the influence of sea level changes and associated variations in local depositional conditions on stratigraphic trends in RSE enrichments and isotope compositions.

Original languageEnglish (US)
Pages (from-to)191-209
Number of pages19
JournalGeochimica et Cosmochimica Acta
Volume261
DOIs
StatePublished - Sep 15 2019

Fingerprint

Ediacaran
Molybdenum
molybdenum
Isotopes
Oxygenation
Sediments
isotope
oxygenation
Sea level
basin
Oxides
open ocean
sediment
Sedimentary rocks
oxide
highstand
global ocean
sea level change
sedimentary basin
connectivity

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Multiple negative molybdenum isotope excursions in the Doushantuo Formation (South China) fingerprint complex redox-related processes in the Ediacaran Nanhua Basin. / Ostrander, Chadlin M.; Sahoo, Swapan K.; Kendall, Brian; Jiang, Ganqing; Planavsky, Noah J.; Lyons, Timothy W.; Nielsen, Sune G.; Owens, Jeremy D.; Gordon, Gwyneth W.; Romaniello, Stephen J.; Anbar, Ariel D.

In: Geochimica et Cosmochimica Acta, Vol. 261, 15.09.2019, p. 191-209.

Research output: Contribution to journalArticle

Ostrander, Chadlin M. ; Sahoo, Swapan K. ; Kendall, Brian ; Jiang, Ganqing ; Planavsky, Noah J. ; Lyons, Timothy W. ; Nielsen, Sune G. ; Owens, Jeremy D. ; Gordon, Gwyneth W. ; Romaniello, Stephen J. ; Anbar, Ariel D. / Multiple negative molybdenum isotope excursions in the Doushantuo Formation (South China) fingerprint complex redox-related processes in the Ediacaran Nanhua Basin. In: Geochimica et Cosmochimica Acta. 2019 ; Vol. 261. pp. 191-209.
@article{3bb153fc147e4d93a489dc79ea735c73,
title = "Multiple negative molybdenum isotope excursions in the Doushantuo Formation (South China) fingerprint complex redox-related processes in the Ediacaran Nanhua Basin",
abstract = "The Ediacaran Doushantuo Formation offers one of the most complete and extensively studied records of end-Neoproterozoic biotic and environmental change. Here, we report multiple coeval negative molybdenum (Mo) isotope excursions (to as low as δ98MoNIST+0.25 = −2.24 ± 0.10‰; 2SD) in shales from four separate sites in South China (Rongxi, Taoying, Wuhe, and Yuanjia) that preserve the Doushantuo Formation. The negative δ98Mo excursions appear coincident with previously discovered and seemingly peculiar redox-sensitive element (RSE) patterns in the same sedimentary rocks. We propose that these geochemical trends can be explained by some combination of (a) enhanced local marine oxygenation in the sedimentary basin where the Doushantuo Formation was originally deposited (the Nanhua Basin) and (b) changes in the degree of connectivity between this paleo basin and the open ocean. Enhanced local marine oxygenation, by exposing more sediments in the Nanhua basin to H2S-poor conditions, could have hindered quantitative tetrathiomolybdate formation within these sediments. Local marine oxygenation could have also stimulated the operation of a Mn oxide shuttle. Today, both of these processes are shown to promote the retention of lighter-mass Mo isotopes in sediments and also govern RSE enrichment patterns. Alternatively, or in addition, the Nanhua Basin may not have maintained an uninterrupted connection with the open ocean during the entirety of the Ediacaran Period. The negative δ98Mo excursions occur coincident with sea level highstands that could have also exposed more sediments in the basin to H2S poor conditions and/or catalyzed the operation of a local Mn oxide shuttle. When trying to infer temporal changes in ancient global ocean redox, it is important to consider the influence of sea level changes and associated variations in local depositional conditions on stratigraphic trends in RSE enrichments and isotope compositions.",
author = "Ostrander, {Chadlin M.} and Sahoo, {Swapan K.} and Brian Kendall and Ganqing Jiang and Planavsky, {Noah J.} and Lyons, {Timothy W.} and Nielsen, {Sune G.} and Owens, {Jeremy D.} and Gordon, {Gwyneth W.} and Romaniello, {Stephen J.} and Anbar, {Ariel D.}",
year = "2019",
month = "9",
day = "15",
doi = "10.1016/j.gca.2019.07.016",
language = "English (US)",
volume = "261",
pages = "191--209",
journal = "Geochmica et Cosmochimica Acta",
issn = "0016-7037",
publisher = "Elsevier Limited",

}

TY - JOUR

T1 - Multiple negative molybdenum isotope excursions in the Doushantuo Formation (South China) fingerprint complex redox-related processes in the Ediacaran Nanhua Basin

AU - Ostrander, Chadlin M.

AU - Sahoo, Swapan K.

AU - Kendall, Brian

AU - Jiang, Ganqing

AU - Planavsky, Noah J.

AU - Lyons, Timothy W.

AU - Nielsen, Sune G.

AU - Owens, Jeremy D.

AU - Gordon, Gwyneth W.

AU - Romaniello, Stephen J.

AU - Anbar, Ariel D.

PY - 2019/9/15

Y1 - 2019/9/15

N2 - The Ediacaran Doushantuo Formation offers one of the most complete and extensively studied records of end-Neoproterozoic biotic and environmental change. Here, we report multiple coeval negative molybdenum (Mo) isotope excursions (to as low as δ98MoNIST+0.25 = −2.24 ± 0.10‰; 2SD) in shales from four separate sites in South China (Rongxi, Taoying, Wuhe, and Yuanjia) that preserve the Doushantuo Formation. The negative δ98Mo excursions appear coincident with previously discovered and seemingly peculiar redox-sensitive element (RSE) patterns in the same sedimentary rocks. We propose that these geochemical trends can be explained by some combination of (a) enhanced local marine oxygenation in the sedimentary basin where the Doushantuo Formation was originally deposited (the Nanhua Basin) and (b) changes in the degree of connectivity between this paleo basin and the open ocean. Enhanced local marine oxygenation, by exposing more sediments in the Nanhua basin to H2S-poor conditions, could have hindered quantitative tetrathiomolybdate formation within these sediments. Local marine oxygenation could have also stimulated the operation of a Mn oxide shuttle. Today, both of these processes are shown to promote the retention of lighter-mass Mo isotopes in sediments and also govern RSE enrichment patterns. Alternatively, or in addition, the Nanhua Basin may not have maintained an uninterrupted connection with the open ocean during the entirety of the Ediacaran Period. The negative δ98Mo excursions occur coincident with sea level highstands that could have also exposed more sediments in the basin to H2S poor conditions and/or catalyzed the operation of a local Mn oxide shuttle. When trying to infer temporal changes in ancient global ocean redox, it is important to consider the influence of sea level changes and associated variations in local depositional conditions on stratigraphic trends in RSE enrichments and isotope compositions.

AB - The Ediacaran Doushantuo Formation offers one of the most complete and extensively studied records of end-Neoproterozoic biotic and environmental change. Here, we report multiple coeval negative molybdenum (Mo) isotope excursions (to as low as δ98MoNIST+0.25 = −2.24 ± 0.10‰; 2SD) in shales from four separate sites in South China (Rongxi, Taoying, Wuhe, and Yuanjia) that preserve the Doushantuo Formation. The negative δ98Mo excursions appear coincident with previously discovered and seemingly peculiar redox-sensitive element (RSE) patterns in the same sedimentary rocks. We propose that these geochemical trends can be explained by some combination of (a) enhanced local marine oxygenation in the sedimentary basin where the Doushantuo Formation was originally deposited (the Nanhua Basin) and (b) changes in the degree of connectivity between this paleo basin and the open ocean. Enhanced local marine oxygenation, by exposing more sediments in the Nanhua basin to H2S-poor conditions, could have hindered quantitative tetrathiomolybdate formation within these sediments. Local marine oxygenation could have also stimulated the operation of a Mn oxide shuttle. Today, both of these processes are shown to promote the retention of lighter-mass Mo isotopes in sediments and also govern RSE enrichment patterns. Alternatively, or in addition, the Nanhua Basin may not have maintained an uninterrupted connection with the open ocean during the entirety of the Ediacaran Period. The negative δ98Mo excursions occur coincident with sea level highstands that could have also exposed more sediments in the basin to H2S poor conditions and/or catalyzed the operation of a local Mn oxide shuttle. When trying to infer temporal changes in ancient global ocean redox, it is important to consider the influence of sea level changes and associated variations in local depositional conditions on stratigraphic trends in RSE enrichments and isotope compositions.

UR - http://www.scopus.com/inward/record.url?scp=85069715141&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85069715141&partnerID=8YFLogxK

U2 - 10.1016/j.gca.2019.07.016

DO - 10.1016/j.gca.2019.07.016

M3 - Article

AN - SCOPUS:85069715141

VL - 261

SP - 191

EP - 209

JO - Geochmica et Cosmochimica Acta

JF - Geochmica et Cosmochimica Acta

SN - 0016-7037

ER -