In cold seep areas, carbonates form as a result of the anaerobic oxidation of methane, which incr... more In cold seep areas, carbonates form as a result of the anaerobic oxidation of methane, which increases alkalinity in pore waters. Upon formation, cold seep carbonates incorporate dissolved alkali earth elements, such as Ca and Sr. The Ca and Sr isotopic compositions of authigenic carbonates and associated pore waters can hence provide information into fluid sources and biogeochemical processes at cold seeps. Over the last decades, radiogenic 87Sr/86Sr ratios in sediment interstitial fluids have been used for identifying deep fluid sources in seepage areas. However, recent studies have demonstrated that significant fractionation of stable Sr isotopes can occur in marine carbonates, which led to a revisited view of the oceanic budget [1]. Here, we report paired 87Sr/86Sr and #88/86Sr values on a series of authigenic carbonate crusts and associated pore waters from fluid seepage areas of the Niger and Nile deep-sea fans. Sr isotopes were measured on a Neptune MC-ICP-MS using Zr for mas...
Mineralogical Magazine | www.minersoc.org 1866 Mg isotope composition of the bulk silicate earth ... more Mineralogical Magazine | www.minersoc.org 1866 Mg isotope composition of the bulk silicate earth constrained by first princeples calculation FANG HUANG, ZHONG-QING WU, LI-JUAN CHEN 1 CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, USTC, Hefei, Anhui 230026. Email: fhuang@ustc.edu.edu 2 School of Earth and Space Sciences, University of Science and Technology, Hefei, Anhui 230026, China
Jianianhualong tengi is a key taxon for understanding the evolution of pennaceous feathers as wel... more Jianianhualong tengi is a key taxon for understanding the evolution of pennaceous feathers as well as troodontid theropods, and it is known by only the holotype, which was recovered from the Lower Cretaceous Yixian Formation of western Liaoning, China. Here, we carried out a large-area micro-X-Ray fluorescence (micro-XRF) analysis on the holotypic specimen of Jianianhualong tengi via a Brucker M6 Jetstream mobile XRF scanner. The elemental distribution measurements of the specimen show an enrichment of typical bones couponing elements such as S, P and Ca allowing to visualize the fossil structure. Additionally, to this, the bones are enriched in several heavier elements such as Sr, Th, Y and Ce over the surrounding rocks. The enrichment is most likely associated to secondary mineralization and the phosphates from the bones. Interestingly the plumage shape correlates with an enrichment in elements such as Cu, Ni and Ti, consistent with a previous study [1] on Archaeopteryx using sync...
ABSTRACT Carbon isotope, sulfur isotope, and trace element (including Rare Earth Elements, REE) a... more ABSTRACT Carbon isotope, sulfur isotope, and trace element (including Rare Earth Elements, REE) analyses were conducted on the carbonates of the Dengying Formation at Lianghekou section in southern Shaanxi to reconstruct the terminal Ediacaran shallow-water environment on the northwestern margin of the Yangtze Platform. At Lianghekou section, samples in the middle 50-m of the Beiwan Member show characteristics of low ΣREE concentrations, no MREE-enriched REE distribution patterns, high Ce/Ce* values close to 1, and enriched redox-sensitive elements, whereas samples in the lower 30-m and upper 10-m show opposite characteristics of high ΣREE concentrations, MREE-enriched REE distribution patterns, low Ce/Ce* values around 0.6, and no redox-sensitive elements enriched, indicating that oxygenation did occur in the shallow water on the northwestern margin of the Yangtze Platform and redox conditions of the shallow water fluctuated from relatively oxygenated to anoxic and then back to oxygenated again. We propose that the anoxia appeared in middle of the Beiwan time may associate with the anoxic upwelled water. On one hand, abundant nutrients were brought in by this upwelling event, which stimulated the photosynthetic carbon fixation and increased the organic carbon burial under this anoxic condition, causing a peak of 3.6‰ in γ 13 C. On the other hand, because the anoxic upwelled water replaced the oxic shallow water, together with the increasing organic matter in the water column, bacterial sulfate reduction was enhanced and therefore quickly reduced the sulfate concentration, which eventually caused γ 34 S increasing to 50‰. However, as the upwelling gradually disappeared, γ 13 C and γ 34 SCAS values decreased as well in the late Beiwan time, indicating the shallow water went back to suboxic or oxic again.
Investigation of climatic conditions prior to the Sturtian glaciations is critical to understandi... more Investigation of climatic conditions prior to the Sturtian glaciations is critical to understanding the trigger mechanism for the series of Neoproterozoic global glaciations. In this study, we report high-resolution chemical index of alteration (CIA) records in the sediments of South China prior to the Sturtian glaciation (820~720 Ma). Our results showed there occurred multiple climate cooling before the Sturtian glaciations in South China: (1) a series of episodic and possibly global climate cooling periods from ca. 750 Ma to 725 Ma, which also caused some diachronous regional glaciations; (2) a permanent climate cooling period between ca. 800 Ma and 770 Ma, probably contemporaneous to the global "Bitter Springs stage" δ(13)C negative excursion; (3) a climate cooling period between ca. 815 Ma and 810 Ma. The three stages of climate cooling are also supported by their correspondence to previously reported extremely low δ(18)O records of igneous/metamorphic minerals from So...
Oceans Before the Dawn Although the fossil record shows a clear explosion of animal diversity in ... more Oceans Before the Dawn Although the fossil record shows a clear explosion of animal diversity in the oceans at the beginning of the Cambrian period (∼542 million years ago), the evolutionary pressures driving this increase in diversity remain unclear. The likely scenario involves drastic changes in the distribution of oxygen in ocean basins, but global glaciations and poor preservation of rocks from this time often prevent a clear picture of global ecology before the dawn of animal life. Li et al. (p. 80 , published online 11 February; see the Perspective by Narbonne ) characterized the geochemical makeup of sedimentary rocks from south China that indicate alternating layers of sulfide- and iron-rich (i.e., sulfate-limited) anoxic waters in the several million years leading up to the Cambrian. These conditions may have set the stage for an eventual increase in productivity of photosynthetic life that oxygenated the oceans and allowed for rapid animal evolution.
Abstract A new set of δ34Ssulfide δ34Ssulfate and δ13Ccarbonate values has been reported from Neo... more Abstract A new set of δ34Ssulfide δ34Ssulfate and δ13Ccarbonate values has been reported from Neoproterozoic sedimentary rocks in southern China. The interglacial blackshales of the Datangpo Fm. display higher δ34Ssulfied values with>+ 20‰. average, ...
Proceedings of the National Academy of Sciences, 2008
Recent geochemical data from Oman, Newfoundland, and the western United States suggest that long-... more Recent geochemical data from Oman, Newfoundland, and the western United States suggest that long-term oxidation of Ediacaran oceans resulted in progressive depletion of a large dissolved organic carbon (DOC) reservoir and potentially triggered the radiation of acanthomorphic acritarchs, algae, macroscopic Ediacara organisms, and, subsequently, motile bilaterian animals. However, the hypothesized coupling between ocean oxidation and evolution is contingent on the reliability of continuous geochemical and paleontological data in individual sections and of intercontinental correlations. Here we report high-resolution geochemical data from the fossil-rich Doushantuo Formation (635–551 Ma) in South China that confirm trends from other broadly equivalent sections and highlight key features that have not been observed in most sections or have received little attention. First, samples from the lower Doushantuo Formation are characterized by remarkably stable δ 13 C org (carbon isotope compo...
Biogeochemical signatures preserved in ancient sedimentary rocks provide clues to the nature and ... more Biogeochemical signatures preserved in ancient sedimentary rocks provide clues to the nature and timing of the oxygenation of the Earth's atmosphere. Geochemical data suggest that oxygenation proceeded in two broad steps near the beginning and end of the Proterozoic eon (2,500 to 542 million years ago). The oxidation state of the Proterozoic ocean between these two steps and the timing of deep-ocean oxygenation have important implications for the evolutionary course of life on Earth but remain poorly known. Here we present a new perspective on ocean oxygenation based on the authigenic accumulation of the redox-sensitive transition element molybdenum in sulphidic black shales. Accumulation of authigenic molybdenum from sea water is already seen in shales by 2,650 Myr ago; however, the small magnitudes of these enrichments reflect weak or transient sources of dissolved molybdenum before about 2,200 Myr ago, consistent with minimal oxidative weathering of the continents. Enrichmen...
In cold seep areas, carbonates form as a result of the anaerobic oxidation of methane, which incr... more In cold seep areas, carbonates form as a result of the anaerobic oxidation of methane, which increases alkalinity in pore waters. Upon formation, cold seep carbonates incorporate dissolved alkali earth elements, such as Ca and Sr. The Ca and Sr isotopic compositions of authigenic carbonates and associated pore waters can hence provide information into fluid sources and biogeochemical processes at cold seeps. Over the last decades, radiogenic 87Sr/86Sr ratios in sediment interstitial fluids have been used for identifying deep fluid sources in seepage areas. However, recent studies have demonstrated that significant fractionation of stable Sr isotopes can occur in marine carbonates, which led to a revisited view of the oceanic budget [1]. Here, we report paired 87Sr/86Sr and #88/86Sr values on a series of authigenic carbonate crusts and associated pore waters from fluid seepage areas of the Niger and Nile deep-sea fans. Sr isotopes were measured on a Neptune MC-ICP-MS using Zr for mas...
Mineralogical Magazine | www.minersoc.org 1866 Mg isotope composition of the bulk silicate earth ... more Mineralogical Magazine | www.minersoc.org 1866 Mg isotope composition of the bulk silicate earth constrained by first princeples calculation FANG HUANG, ZHONG-QING WU, LI-JUAN CHEN 1 CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, USTC, Hefei, Anhui 230026. Email: fhuang@ustc.edu.edu 2 School of Earth and Space Sciences, University of Science and Technology, Hefei, Anhui 230026, China
Jianianhualong tengi is a key taxon for understanding the evolution of pennaceous feathers as wel... more Jianianhualong tengi is a key taxon for understanding the evolution of pennaceous feathers as well as troodontid theropods, and it is known by only the holotype, which was recovered from the Lower Cretaceous Yixian Formation of western Liaoning, China. Here, we carried out a large-area micro-X-Ray fluorescence (micro-XRF) analysis on the holotypic specimen of Jianianhualong tengi via a Brucker M6 Jetstream mobile XRF scanner. The elemental distribution measurements of the specimen show an enrichment of typical bones couponing elements such as S, P and Ca allowing to visualize the fossil structure. Additionally, to this, the bones are enriched in several heavier elements such as Sr, Th, Y and Ce over the surrounding rocks. The enrichment is most likely associated to secondary mineralization and the phosphates from the bones. Interestingly the plumage shape correlates with an enrichment in elements such as Cu, Ni and Ti, consistent with a previous study [1] on Archaeopteryx using sync...
ABSTRACT Carbon isotope, sulfur isotope, and trace element (including Rare Earth Elements, REE) a... more ABSTRACT Carbon isotope, sulfur isotope, and trace element (including Rare Earth Elements, REE) analyses were conducted on the carbonates of the Dengying Formation at Lianghekou section in southern Shaanxi to reconstruct the terminal Ediacaran shallow-water environment on the northwestern margin of the Yangtze Platform. At Lianghekou section, samples in the middle 50-m of the Beiwan Member show characteristics of low ΣREE concentrations, no MREE-enriched REE distribution patterns, high Ce/Ce* values close to 1, and enriched redox-sensitive elements, whereas samples in the lower 30-m and upper 10-m show opposite characteristics of high ΣREE concentrations, MREE-enriched REE distribution patterns, low Ce/Ce* values around 0.6, and no redox-sensitive elements enriched, indicating that oxygenation did occur in the shallow water on the northwestern margin of the Yangtze Platform and redox conditions of the shallow water fluctuated from relatively oxygenated to anoxic and then back to oxygenated again. We propose that the anoxia appeared in middle of the Beiwan time may associate with the anoxic upwelled water. On one hand, abundant nutrients were brought in by this upwelling event, which stimulated the photosynthetic carbon fixation and increased the organic carbon burial under this anoxic condition, causing a peak of 3.6‰ in γ 13 C. On the other hand, because the anoxic upwelled water replaced the oxic shallow water, together with the increasing organic matter in the water column, bacterial sulfate reduction was enhanced and therefore quickly reduced the sulfate concentration, which eventually caused γ 34 S increasing to 50‰. However, as the upwelling gradually disappeared, γ 13 C and γ 34 SCAS values decreased as well in the late Beiwan time, indicating the shallow water went back to suboxic or oxic again.
Investigation of climatic conditions prior to the Sturtian glaciations is critical to understandi... more Investigation of climatic conditions prior to the Sturtian glaciations is critical to understanding the trigger mechanism for the series of Neoproterozoic global glaciations. In this study, we report high-resolution chemical index of alteration (CIA) records in the sediments of South China prior to the Sturtian glaciation (820~720 Ma). Our results showed there occurred multiple climate cooling before the Sturtian glaciations in South China: (1) a series of episodic and possibly global climate cooling periods from ca. 750 Ma to 725 Ma, which also caused some diachronous regional glaciations; (2) a permanent climate cooling period between ca. 800 Ma and 770 Ma, probably contemporaneous to the global "Bitter Springs stage" δ(13)C negative excursion; (3) a climate cooling period between ca. 815 Ma and 810 Ma. The three stages of climate cooling are also supported by their correspondence to previously reported extremely low δ(18)O records of igneous/metamorphic minerals from So...
Oceans Before the Dawn Although the fossil record shows a clear explosion of animal diversity in ... more Oceans Before the Dawn Although the fossil record shows a clear explosion of animal diversity in the oceans at the beginning of the Cambrian period (∼542 million years ago), the evolutionary pressures driving this increase in diversity remain unclear. The likely scenario involves drastic changes in the distribution of oxygen in ocean basins, but global glaciations and poor preservation of rocks from this time often prevent a clear picture of global ecology before the dawn of animal life. Li et al. (p. 80 , published online 11 February; see the Perspective by Narbonne ) characterized the geochemical makeup of sedimentary rocks from south China that indicate alternating layers of sulfide- and iron-rich (i.e., sulfate-limited) anoxic waters in the several million years leading up to the Cambrian. These conditions may have set the stage for an eventual increase in productivity of photosynthetic life that oxygenated the oceans and allowed for rapid animal evolution.
Abstract A new set of δ34Ssulfide δ34Ssulfate and δ13Ccarbonate values has been reported from Neo... more Abstract A new set of δ34Ssulfide δ34Ssulfate and δ13Ccarbonate values has been reported from Neoproterozoic sedimentary rocks in southern China. The interglacial blackshales of the Datangpo Fm. display higher δ34Ssulfied values with>+ 20‰. average, ...
Proceedings of the National Academy of Sciences, 2008
Recent geochemical data from Oman, Newfoundland, and the western United States suggest that long-... more Recent geochemical data from Oman, Newfoundland, and the western United States suggest that long-term oxidation of Ediacaran oceans resulted in progressive depletion of a large dissolved organic carbon (DOC) reservoir and potentially triggered the radiation of acanthomorphic acritarchs, algae, macroscopic Ediacara organisms, and, subsequently, motile bilaterian animals. However, the hypothesized coupling between ocean oxidation and evolution is contingent on the reliability of continuous geochemical and paleontological data in individual sections and of intercontinental correlations. Here we report high-resolution geochemical data from the fossil-rich Doushantuo Formation (635–551 Ma) in South China that confirm trends from other broadly equivalent sections and highlight key features that have not been observed in most sections or have received little attention. First, samples from the lower Doushantuo Formation are characterized by remarkably stable δ 13 C org (carbon isotope compo...
Biogeochemical signatures preserved in ancient sedimentary rocks provide clues to the nature and ... more Biogeochemical signatures preserved in ancient sedimentary rocks provide clues to the nature and timing of the oxygenation of the Earth's atmosphere. Geochemical data suggest that oxygenation proceeded in two broad steps near the beginning and end of the Proterozoic eon (2,500 to 542 million years ago). The oxidation state of the Proterozoic ocean between these two steps and the timing of deep-ocean oxygenation have important implications for the evolutionary course of life on Earth but remain poorly known. Here we present a new perspective on ocean oxygenation based on the authigenic accumulation of the redox-sensitive transition element molybdenum in sulphidic black shales. Accumulation of authigenic molybdenum from sea water is already seen in shales by 2,650 Myr ago; however, the small magnitudes of these enrichments reflect weak or transient sources of dissolved molybdenum before about 2,200 Myr ago, consistent with minimal oxidative weathering of the continents. Enrichmen...
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