TY - JOUR
T1 - Biomarker Evidence of Algal-Microbial Community Changes Linked to Redox and Salinity Variation, Upper Devonian Chattanooga Shale (Tennessee, USA)
AU - Song, Yi
AU - Gilleaudeau, Geoffrey J.
AU - Lyons, Thomas J.
AU - Jeffrey Over, D.
AU - Lyons, Timothy W.
AU - Anbar, Ariel D.
AU - Xie, Shucheng
N1 - Funding Information:
This work was supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (grant no. 41821001), the Key Research and Development Project of Ministry of Science and Technology (grant no. 2016YFA060H00), and the 111 project (National Bureau of Foreign Experts and the Ministry of Education of China; grant no. B08030). We thank Dr. Albert Horton and the Tennessee Geological Survey for loan of the Chattanooga Shale core used in this study, and Tim Lyons for access to analytical facilities at the University of California at Riverside. G.J.G thanks the National Aeronautics and Space Administration Postdoctoral Program, and TJA thanks the National Science Foundation Sedimentary Geology and Paleobiology program for funding. We thank Brad Singer for editorial handling and Michael Tuite for a constructive review of the manuscript.
Funding Information:
This work was supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (grant no. 41821001), the Key Research and Development Project of Ministry of Science and Technology (grant no. 2016YFA0601100), and the 111 project (National Bureau of Foreign Experts and the Ministry of Education of China; grant no. B08030). We thank Dr. Albert Horton and the Tennessee Geological Survey for loan of the Chattanooga Shale core used in this study, and Tim Lyons for access to analytical facilities at the University of California at Riverside. G.J.G thanks the National Aeronautics and Space Administration Postdoctoral Program, and TJA thanks the National Science Foundation Sedimentary Geology and Paleobiology program for funding. We thank Brad Singer for editorial handling and Michael Tuite for a constructive review of the manuscript.
Publisher Copyright:
©2020 Geological Society of America
PY - 2020/6/29
Y1 - 2020/6/29
N2 - climate change and widespread oceanic anoxia. Here, we provide high-resolution lipid biomarker chemostrati- graphic records from the Upper Devonian Chattanooga Shale (Tennessee, USA) to investigate algal-microbial community changes in the southern Illinois Basin that were related to contemporaneous shifts in marine redox (as proxied by trace metals, Fe-species, and Corg/P) and salinity conditions (as proxied by B/Ga, Sr/Ba, and S/total organic carbon). The Frasnian was characterized by dominantly bacterial lipids (high hopane/sterane), near-marine salinity, and a shift from oxic to increasingly reducing conditions in response to increasing organic carbon sinking fluxes. Aryl isoprenoids and aryl isoprenoid ratios reveal that the O2-H2S chemocline was unstable and intermittently shallow (i.e., within the photic zone). The Frasnian-Famennian boundary was marked by a shift in micro- algal community composition toward green algal (e.g., prasinophyte) dominance (lower C27 and higher C28 and C29 steranes), a sharp reduction in watermass salinity, and a stable O2-H2S chemocline below the photic zone, conditions that persisted until nearly the end of the Famennian. We infer that changing watermass conditions, especially a sharp reduction in salinity to possibly low-brackish conditions (10 psu), were the primary cause of concurrent changes in the microalgal community, reflecting tolerance of low-salinity conditions by green algae. Transient spikes in moretane/hopane (M/H) ratios may record enhanced terrestrial weathering at the Fras- nian-Famennian and Devonian-Carboniferous boundaries, triggered by coeval glacio- eustatic falls and increased inputs of soil organic matter. High M/H and pristane/phy- tane, in combination with low chemical index of alteration and K/Al, record a decrease in chemical weathering intensity during the Famennian that may have been due to contemporaneous climatic cooling, and a concurrent reduction in silt content may reflect stabilization of land surfaces by vascular plants and resulting reduced sediment yields. This study demonstrates the effectiveness of combining organic and inorganic geochemical proxies (including novel paleosalinity indices) for determination of environmental controls on the composition and productivity of plankton communities in paleomarine systems.
AB - climate change and widespread oceanic anoxia. Here, we provide high-resolution lipid biomarker chemostrati- graphic records from the Upper Devonian Chattanooga Shale (Tennessee, USA) to investigate algal-microbial community changes in the southern Illinois Basin that were related to contemporaneous shifts in marine redox (as proxied by trace metals, Fe-species, and Corg/P) and salinity conditions (as proxied by B/Ga, Sr/Ba, and S/total organic carbon). The Frasnian was characterized by dominantly bacterial lipids (high hopane/sterane), near-marine salinity, and a shift from oxic to increasingly reducing conditions in response to increasing organic carbon sinking fluxes. Aryl isoprenoids and aryl isoprenoid ratios reveal that the O2-H2S chemocline was unstable and intermittently shallow (i.e., within the photic zone). The Frasnian-Famennian boundary was marked by a shift in micro- algal community composition toward green algal (e.g., prasinophyte) dominance (lower C27 and higher C28 and C29 steranes), a sharp reduction in watermass salinity, and a stable O2-H2S chemocline below the photic zone, conditions that persisted until nearly the end of the Famennian. We infer that changing watermass conditions, especially a sharp reduction in salinity to possibly low-brackish conditions (10 psu), were the primary cause of concurrent changes in the microalgal community, reflecting tolerance of low-salinity conditions by green algae. Transient spikes in moretane/hopane (M/H) ratios may record enhanced terrestrial weathering at the Fras- nian-Famennian and Devonian-Carboniferous boundaries, triggered by coeval glacio- eustatic falls and increased inputs of soil organic matter. High M/H and pristane/phy- tane, in combination with low chemical index of alteration and K/Al, record a decrease in chemical weathering intensity during the Famennian that may have been due to contemporaneous climatic cooling, and a concurrent reduction in silt content may reflect stabilization of land surfaces by vascular plants and resulting reduced sediment yields. This study demonstrates the effectiveness of combining organic and inorganic geochemical proxies (including novel paleosalinity indices) for determination of environmental controls on the composition and productivity of plankton communities in paleomarine systems.
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U2 - 10.1130/B35543.1
DO - 10.1130/B35543.1
M3 - Article
AN - SCOPUS:85088289739
SN - 0016-7606
VL - 133
SP - 409
EP - 424
JO - Bulletin of the Geological Society of America
JF - Bulletin of the Geological Society of America
ER -