Anoxic depositional overprinting of 238U/235U in calcite: When do carbonates tell black shale tales?

Geology ◽  
2021 ◽  
Author(s):  
Xinming Chen ◽  
Stephen J. Romaniello ◽  
Michael McCormick ◽  
Alyssa Sherry ◽  
Jeff R. Havig ◽  
...  
Keyword(s):  
New York ◽  
Water Column ◽  
Isotope Geochemistry ◽  
Sediment Traps ◽  
Depositional Environments ◽  
Uranium Isotopes ◽  
Carbonate Sediments ◽  
Anoxic Water ◽  
Green Lake ◽  
Bottom Waters

The fidelity of uranium isotopes (δ238U) in marine carbonates as a paleoredox proxy relies on whether carbonates can record and preserve seawater δ238U. Although modern carbonate sediments deposited under oxic conditions have been shown to track seawater δ238U, it remains unknown whether this is true for carbonates deposited under anoxic conditions. This is a crucial question because many ancient carbonates were likely deposited or reworked under anoxic bottom waters. To better understand the behavior of uranium isotopes under this scenario, we investigated U isotope geochemistry in the meromictic Fayetteville Green Lake (FGL; New York, USA), where primary calcite is precipitated from oxic surface waters, sinks past the chemocline, and is deposited under anoxic bottom waters. We observed significant depletions of dissolved U concentration (from 2.7 to 0.9 ppb) and δ238U (from –0.55‰ to –0.96‰) below the chemocline in FGL. Parallel with these depletions, δ238U of sediment traps increased progressively from –0.51‰ to –0.16‰, suggesting that U(VI) reduction was occurring in the anoxic water column. Carbonate sediments deposited under anoxic bottom waters were enriched in U by 6–18× compared to primary calcite. Our data suggest that such significant authigenic U enrichments resulted from U(VI) reduction in the anoxic water column and below the sediment-water interface. The δ238U value in the top 0.25 cm of sediments was –0.29‰ ± 0.10‰, overprinting original δ238U in primary calcite (–0.51‰ ± 0.02‰). Future applications of carbonate δ238U as a paleoredox proxy should consider depositional environments (oxic vs. anoxic) of carbonates.

WATER COLUMN AND SEDIMENT CARBON ISOTOPE GEOCHEMISTRY OF PERMANENTLY REDOX-STRATIFIED FAYETTEVILLE GREEN LAKE, NEW YORK, USA

2017 ◽  
Author(s):  
Jeff Havig ◽  
◽  
Trinity L. Hamilton ◽  
Mike McCormick ◽  
Brianna McClure ◽  
...  
Keyword(s):  
New York ◽  
Water Column ◽  
Carbon Isotope ◽  
Isotope Geochemistry ◽  
Green Lake ◽  
Sediment Carbon

scholarly journals Water column and sediment stable carbon isotope biogeochemistry of permanently redox-stratified Fayetteville Green Lake, New York, U.S.A.

2017 ◽  
Vol 63 (2) ◽  
pp. 570-587 ◽  
Author(s):  
Jeff R. Havig ◽  
Trinity L. Hamilton ◽  
Michael McCormick ◽  
Brianna McClure ◽  
Todd Sowers ◽  
...  
Keyword(s):  
New York ◽  
Water Column ◽  
Carbon Isotope ◽  
Stable Carbon Isotope ◽  
Stable Carbon ◽  
Green Lake

Projected Consequences of Dumping Sewage Sludge at a Deep Ocean Site near New York Bight

1983 ◽  
Vol 40 (S2) ◽  
pp. s228-s241 ◽  
Author(s):  
Thomas P. O'Connor ◽  
Akira Okubo ◽  
Michael A. Champ ◽  
P. Kilho Park
Keyword(s):  
New York ◽  
Sewage Sludge ◽  
Water Column ◽  
Biological Response ◽  
Deep Ocean ◽  
Sediment Traps ◽  
Open Ocean ◽  
Sediment Surface ◽  
Surface Mixed Layer ◽  
Horizontal Dispersion

Projections are made of the distribution of and biological response to New York/New Jersey sewage sludges if they are slowly discharged from barges at a deepwater location in annual volumes of 7 × 106 m3. We have used available information on sludge composition, dispersion of barge-dumped wastes, flow through the dumpsite, sewage sludge settling under quiescent conditions, rates of horizontal dispersion in the deep sea, chemical composition of open ocean water, ambient mass fluxes to the seafloor, sediment characteristics, bioturbation rates, and biological responses to sludge and its components. Within a 20-m surface mixed layer between the dumpsite and the Gulf Stream a chemical signal of dumping may be evident in iron, lead, zinc, chromium, and PCB concentrations. Water column contamination would appear to be less than necessary to affect planktonic organisms or fish. Seafloor contamination would be due primarily to sludge particles falling at 10−2 cm∙s−1 or faster. Allowing for bioturbation, the major sediment contaminants, PCB s and PAHs, could reach concentrations at the sediment surface of 0.2 and 0.3 μg∙g−1, respectively, after 100 yr. Concentrations of that order in shallow ocean benthic systems are not obviously related to altered benthic life. The strength of these projections would be increased with better understanding in many areas, especially on the effect of natural and barge-induced turbulence on particle flocculation and on rates of horizontal dispersion in the deep ocean. If sludge is dumped, the water column should be studied for chemical evidence of sludge and response of open ocean plankton. Arrays of sediment traps could be deployed to quantify the rate and areal extent of the settling sludge flux.

scholarly journals Analyses of depositional environments of the Marcellus formation in New York using biomarker and trace metal proxies

2021 ◽  
Author(s):  
Reilly M. Blocho ◽  
Richard W. Smith ◽  
Mark R. Noll
Keyword(s):  
Fatty Acids ◽  
New York ◽  
Organic Matter ◽  
New York State ◽  
Depositional Environments ◽  
Average Chain Length ◽  
Lipid Biomarker ◽  
Two Samples ◽  
Biomarker Analysis ◽  
Marcellus Formation

AbstractThe purpose of this study was to observe how the composition of organic matter (OM) and the extent of anoxia during deposition within the Marcellus Formation in New York varied by distance from the sediment source in eastern New York. Lipid biomarkers (n-alkanes and fatty acids) in the extractable organic component (bitumen) of the shale samples were analyzed, and proxies such as the average chain length (ACL), aquatic to terrestrial ratio (ATR) and carbon preference index (CPI) of n-alkanes were calculated. Fatty acids were relatively non-abundant due to the age of the shale bed, but n-alkane distributions revealed that the primary component of the OM was terrigenous plants. The presence of shorter n-alkane chain lengths in the samples indicated that there was also a minor component of phytoplankton and algal (marine) sourced OM. Whole rock analyses were also conducted, and cerium anomalies were calculated as a proxy for anoxia. All samples had a negative anomaly value, indicating anoxic conditions during deposition. Two samples, however, contained values close to zero and thus were determined to have suboxic conditions. Anoxia and total organic matter (TOM) did not show any spatial trends across the basin, which may be caused by varying depths within the basin during deposition. A correlation between nickel concentrations and TOM was observed and indicates that algae was the primary source of the marine OM, which supports the lipid biomarker analysis. It was determined that the kerogen type of the Marcellus Formation in New York State is type III, consistent with a methane-forming shale bed.

scholarly journals Micro-aerobic bacterial methane oxidation in the chemocline and anoxic water column of deep south-Alpine Lake Lugano (Switzerland)

2014 ◽  
Vol 59 (2) ◽  
pp. 311-324 ◽  
Author(s):  
Jan Blees ◽  
Helge Niemann ◽  
Christine B. Wenk ◽  
Jakob Zopfi ◽  
Carsten J. Schubert ◽  
...  
Keyword(s):  
Water Column ◽  
Methane Oxidation ◽  
Alpine Lake ◽  
Deep South ◽  
Anoxic Water ◽  
Lake Lugano

scholarly journals Amino acid composition and <i>δ</i><sup>15</sup>N of suspended matter in the Arabian Sea: implications for organic matter sources and degradation

2013 ◽  
Vol 10 (11) ◽  
pp. 7689-7702 ◽  
Author(s):  
B. Gaye ◽  
B. Nagel ◽  
K. Dähnke ◽  
T. Rixen ◽  
N. Lahajnar ◽  
...  
Keyword(s):  
Organic Matter ◽  
Amino Acid ◽  
Water Column ◽  
Residence Time ◽  
Mixed Layer ◽  
Suspended Matter ◽  
Arabian Sea ◽  
Monsoon Season ◽  
Sediment Traps ◽  
Surface Mixed Layer

Abstract. Sedimentation in the ocean is fed by large aggregates produced in the surface mixed layer that sink rapidly through the water column. These particles sampled by sediment traps have often been proposed to interact by disaggregation and scavenging with a pool of fine suspended matter with very slow sinking velocities and thus a long residence time. We investigated the amino acid (AA) composition and stable nitrogen isotopic ratios of suspended matter (SPM) sampled during the late SW monsoon season in the Arabian Sea and compared them to those of sinking particles to understand organic matter degradation/modification during passage through the water column. We found that AA composition of mixed layer suspended matter corresponds more to fresh plankton and their aggregates, whereas AA composition of SPM in the sub-thermocline water column deviated progressively from mixed layer composition. We conclude that suspended matter in deep waters and in the mixed layers of oligotrophic stations is dominated by fine material that has a long residence time and organic matter that is resistant to degradation. SPM in areas of high primary productivity is essentially derived from fresh plankton and thus has a strong imprint of the subsurface nitrate source, whereas SPM at oligotrophic stations and at subthermocline depths appears to exchange amino acids and nitrogen isotopes with the dissolved organic carbon (DOC) pool influencing also the δ15N values.

scholarly journals Modulation of the vertical particles transfer efficiency in the Oxygen Minimum Zone off Peru

2018 ◽  
Author(s):  
Marine Bretagnon ◽  
Aurélien Paulmier ◽  
Véronique Garçon ◽  
Boris Dewitte ◽  
Sérena Illig ◽  
...  
Keyword(s):  
Organic Matter ◽  
Water Column ◽  
Sediment Traps ◽  
Biogeochemical Cycles ◽  
High Temporal Resolution ◽  
Oxygen Minimum Zones ◽  
Marine Life ◽  
Minimum Zone ◽  
Earth’S System ◽  
Oxygen Minimum

Abstract. The fate of the Organic Matter (OM) produced by marine life controls the major biogeochemical cycles of the Earth’s system. The OM produced through photosynthesis is either preserved, exported towards sediments or degraded through remineralisation in the water column. The productive Eastern Boundary Upwelling Systems (EBUSs) associated with Oxygen Minimum Zones (OMZs) should foster OM preservation due to low O2 conditions, but their intense and diverse microbial activity should enhance OM degradation. To investigate this contradiction, sediment traps were deployed near the oxycline and in the OMZ core on an instrumented moored line off Peru, providing high temporal resolution O2 series characterizing two seasonal steady states at the upper trap: suboxic ([O2] 

Clay mineral distribution related to rift activity, sea-level changes and paleoceanography in the Cretaceous of the Atlantic Ocean

Clay Minerals ◽  
1993 ◽  
Vol 28 (1) ◽  
pp. 61-84 ◽  
Author(s):  
M. Thiry ◽  
T. Jacquin
Keyword(s):  
Atlantic Ocean ◽  
Sea Level ◽  
Clay Minerals ◽  
Clay Mineral ◽  
Deep Sea ◽  
Depositional Environments ◽  
Sea Level Changes ◽  
Sea Floor ◽  
Deep Sea Sediments ◽  
Bottom Waters

AbstractThe distribution of clay minerals from the N and S Atlantic Cretaceous deep-sea sediments is related to rifting, sea-floor spreading, sea-level variations and paleoceanography. Four main clay mineral suites were identified: two are inherited and indicative of ocean geodynamics, whereas the others result from transformation and authigenesis and are diagnostic of Cretaceous oceanic depositional environments. Illite and chlorite, together with interstratified illite-smectite and smectite occur above the sea-floor basalts and illustrate the contribution of volcanoclastic materials of basaltic origin to the sediments. Kaolinite, with variable amounts of illite, chlorite, smectite and interstratified minerals, indicates detrital inputs from continents near the platform margins. Kaolinite decreases upward in the series due to open marine environments and basin deepening. It may increase in volume during specific time intervals corresponding to periods of falling sea-level during which overall facies regression and erosion of the surrounding platforms occurred. Smectite is the most abundant clay mineral in the Cretaceous deep-sea sediments. Smectite-rich deposits correlate with periods of relatively low sedimentation rates. As paleoweathering profiles and basal deposits at the bottom of Cretaceous transgressive formations are mostly kaolinitic, smectite cannot have been inherited from the continents. Smectite is therefore believed to have formed in the ocean by transformation and recrystallization of detrital materials during early diagenesis. Because of the slow rate of silicate reactions, transformation of clay minerals requires a long residence time of the particles at the water/sediment interface; this explains the relationships between the observed increases in smectite with long-term sea-level rises that tend to starve the basinal settings of sedimentation. Palygorskite, along with dolomite, is relatively common in the N and S Atlantic Cretaceous sediments. It is not detrital because correlative shelf deposits are devoid of palygorskite. Palygorskite is diagnostic of Mg-rich environments and is indicative of the warm and hypersaline bottom waters of the Cretaceous Atlantic ocean.

scholarly journals Mechanisms of dissolved and labile particulate iron supply to shelf waters and phytoplankton blooms off South Georgia, Southern Ocean

2018 ◽  
Vol 15 (16) ◽  
pp. 4973-4993 ◽  
Author(s):  
Christian Schlosser ◽  
Katrin Schmidt ◽  
Alfred Aquilina ◽  
William B. Homoky ◽  
Maxi Castrillejo ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Water Column ◽  
Mixed Layer ◽  
Surface Mixed Layer ◽  
Pore Waters ◽  
Phytoplankton Blooms ◽  
Faecal Pellets ◽  
South Georgia ◽  
Shelf Sediments ◽  
Bottom Waters

Abstract. The island of South Georgia is situated in the iron (Fe)-depleted Antarctic Circumpolar Current of the Southern Ocean. Iron emanating from its shelf system fuels large phytoplankton blooms downstream of the island, but the actual supply mechanisms are unclear. To address this, we present an inventory of Fe, manganese (Mn), and aluminium (Al) in shelf sediments, pore waters, and the water column in the vicinity of South Georgia, alongside data on zooplankton-mediated Fe cycling processes, and provide estimates of the relative dissolved Fe (DFe) fluxes from these sources. Seafloor sediments, modified by authigenic Fe precipitation, were the main particulate Fe source to shelf bottom waters as indicated by the similar Fe ∕ Mn and Fe ∕ Al ratios for shelf sediments and suspended particles in the water column. Less than 1 % of the total particulate Fe pool was leachable surface-adsorbed (labile) Fe and therefore potentially available to organisms. Pore waters formed the primary DFe source to shelf bottom waters, supplying 0.1–44 µmol DFe m−2 d−1. However, we estimate that only 0.41±0.26 µmol DFe m−2 d−1 was transferred to the surface mixed layer by vertical diffusive and advective mixing. Other trace metal sources to surface waters included glacial flour released by melting glaciers and via zooplankton egestion and excretion processes. On average 6.5±8.2 µmol m−2 d−1 of labile particulate Fe was supplied to the surface mixed layer via faecal pellets formed by Antarctic krill (Euphausia superba), with a further 1.1±2.2 µmol DFe m−2 d−1 released directly by the krill. The faecal pellets released by krill included seafloor-derived lithogenic and authigenic material and settled algal debris, in addition to freshly ingested suspended phytoplankton cells. The Fe requirement of the phytoplankton blooms ∼ 1250 km downstream of South Georgia was estimated as 0.33±0.11 µmol m−2 d−1, with the DFe supply by horizontal/vertical mixing, deep winter mixing, and aeolian dust estimated as ∼0.12 µmol m−2 d−1. We hypothesize that a substantial contribution of DFe was provided through recycling of biogenically stored Fe following luxury Fe uptake by phytoplankton on the Fe-rich shelf. This process would allow Fe to be retained in the surface mixed layer of waters downstream of South Georgia through continuous recycling and biological uptake, supplying the large downstream phytoplankton blooms.

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