Redox dynamics of later Cambrian oceans
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Redox dynamics of later Cambrian oceans. / Gill, Benjamin C.; Dahl, Tais W.; Hammarlund, Emma U.; LeRoy, Matthew A.; Gordon, Gwyneth W.; Canfield, Donald E.; Anbar, Ariel D.; Lyons, Timothy W.
In: Palaeogeography, Palaeoclimatology, Palaeoecology, Vol. 581, 110623, 2021.Research output: Contribution to journal › Journal article › Research › peer-review
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T1 - Redox dynamics of later Cambrian oceans
AU - Gill, Benjamin C.
AU - Dahl, Tais W.
AU - Hammarlund, Emma U.
AU - LeRoy, Matthew A.
AU - Gordon, Gwyneth W.
AU - Canfield, Donald E.
AU - Anbar, Ariel D.
AU - Lyons, Timothy W.
N1 - Publisher Copyright: © 2021 Elsevier B.V.
PY - 2021
Y1 - 2021
N2 - A growing body of evidence suggests that the deep oceans during the early Paleozoic Era were widely oxygen deficient, despite evidence for increased marine oxygenation during the Neoproterozoic. However, the temporal and geographic extents and dynamics of reducing marine conditions within these oceans are not well understood. Here, we investigate marine redox history during the Drumian through the earliest Jiangshanian International Stages of the Cambrian Period, using concentrations of redox-sensitive metals (vanadium, uranium, and molybdenum), iron speciation, and Mo isotope stratigraphy of the Alum Shale Formation of Scandinavia. These data suggest a major perturbation occurred in trace metal cycling during the later Cambrian Period that was linked to a transient change in marine redox conditions coincident with the well-known Steptoean Positive Isotope Excursion or SPICE. The δ98Mo measurements of the Alum shale show systematic variations during the interval that contains the SPICE which are broadly consistent with a transient expansion of sulfidic, reducing marine environments — indicating a significant exacerbation of an already-common condition during the Cambrian Period. Additionally, iron speciation data record a local transition from predominantly anoxic, ferruginous (Fe+2 containing) to anoxic, euxinic (sulfide containing) water column conditions near the initiation of the SPICE. Trace metal abundances, however, appear to decline well before the start of the SPICE, suggesting an earlier initiation of the global expansion of reducing environments. More broadly, our data and modeling support the notion that significant portions of the oceans remained oxygen deficient throughout the later portion of the Cambrian, and that these oceans were also prone to transient intervals of more reducing conditions similar to the Oceanic Anoxic Events of the Mesozoic.
AB - A growing body of evidence suggests that the deep oceans during the early Paleozoic Era were widely oxygen deficient, despite evidence for increased marine oxygenation during the Neoproterozoic. However, the temporal and geographic extents and dynamics of reducing marine conditions within these oceans are not well understood. Here, we investigate marine redox history during the Drumian through the earliest Jiangshanian International Stages of the Cambrian Period, using concentrations of redox-sensitive metals (vanadium, uranium, and molybdenum), iron speciation, and Mo isotope stratigraphy of the Alum Shale Formation of Scandinavia. These data suggest a major perturbation occurred in trace metal cycling during the later Cambrian Period that was linked to a transient change in marine redox conditions coincident with the well-known Steptoean Positive Isotope Excursion or SPICE. The δ98Mo measurements of the Alum shale show systematic variations during the interval that contains the SPICE which are broadly consistent with a transient expansion of sulfidic, reducing marine environments — indicating a significant exacerbation of an already-common condition during the Cambrian Period. Additionally, iron speciation data record a local transition from predominantly anoxic, ferruginous (Fe+2 containing) to anoxic, euxinic (sulfide containing) water column conditions near the initiation of the SPICE. Trace metal abundances, however, appear to decline well before the start of the SPICE, suggesting an earlier initiation of the global expansion of reducing environments. More broadly, our data and modeling support the notion that significant portions of the oceans remained oxygen deficient throughout the later portion of the Cambrian, and that these oceans were also prone to transient intervals of more reducing conditions similar to the Oceanic Anoxic Events of the Mesozoic.
KW - Cambrian
KW - Iron Speciation
KW - Marine redox
KW - Molybdenum isotopes
KW - SPICE
KW - Trace metals
U2 - 10.1016/j.palaeo.2021.110623
DO - 10.1016/j.palaeo.2021.110623
M3 - Journal article
AN - SCOPUS:85114139893
VL - 581
JO - Palaeogeography, Palaeoclimatology, Palaeoecology - An International Journal for the Geo-Sciences
JF - Palaeogeography, Palaeoclimatology, Palaeoecology - An International Journal for the Geo-Sciences
SN - 0031-0182
M1 - 110623
ER -
ID: 281702092