Methane Discharge at High Northern Latitudes: Past and Present

Climate is intimately tied to Earth’s hydro- and cryo-spheres. To understand the consequences that predicted global warming can have on biogeochemical cycling and mass inventories in the Arctic Ocean, I will present results on two study sites: the Svalbard margin and the Chuchki sea, that provide information on present-day methane discharge and evidence for the likelihood that groundwater flow during the Early Holocene Thermal Maximum (EHTM). I will review how data collected in the water column and shallow sediment can be used to constrain sources, transport, transformation and timing of methane fluxes, including the potential role of gas hydrate dissociation. Specifically I will discuss the concentration and isotopic composition of various dissolved species and modeling approaches that are valuable to interpret these data in the context of geophysical surveys

Identifying Slope Failure Deposits from a Potentially Mixed Magnetic Susceptibility Signal in Gas Hydrate Bearing Regions

The marine gas hydrate stability zone (GHSZ) occurs in the slope environment along many active and passive continental margins. In this environment, slope failures are common and can occur near the shelf slope break, within submarine canyons, or on the flanks of bathymetric highs, resulting in a spectrum of slope failure deposits from landslides to turbidites. On the Cascadia margin, the GHSZ occurs within the bathymetric thrust ridges and slope basins of the accretionary wedge. Here, the ridges are composed of uplifted abyssal plain deposits associated with submarine fans and/or paleoslope basin deposits formed during the evolution of the accretionary wedge (Johnson et al., 2006; Torres et al., 2008). The adjoining slope basins contain the deposits from slope failure of the ridges. Both ridges and slope basins offshore Central Oregon and Vancouver Island were sampled by drilling during ODP Leg 204 and IODP Expedition 311, respectively (Figure 1). The recovered cores document the distribution and abundance of gas hydrate in these regions within a stratigraphy that is dominated by silt and sand turbidites, debris flows, and intervals of silty clay, separated by hemipelagic clay

Methane hydrate formation in Ulleung basin under conditions of variable salinity: reduced model and experiments

In this paper, we present a reduced model of methane hydrate formation in variable salinity conditions, with details on the equilibrium phase behavior adapted to a case study from Ulleung Basin. The model simplifies the comprehensive model considered by Liu and Flemings using common assumptions on hydrostatic pressure, geothermal gradient, and phase incompressibility, as well as a simplified phase equilibria model. The two-phase threecomponent model is very robust and efficient as well as amenable to various numerical analyses, yet is capable of simulating realistic cases. We compare various thermodynamic models for equilibria as well as attempt a quantitative explanation for anomalous spikes of salinity observed in Ulleung Basin

Isolating detrital and diagenetic signals in magnetic susceptibility records from methane-bearing marine sediments

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Johnson, J. E., Phillips, S. C., Clyde, W. C., Giosan, L., & Torres, M. E. Isolating detrital and diagenetic signals in magnetic susceptibility records from methane-bearing marine sediments. Geochemistry Geophysics Geosystems, 22(9), (2021): e2021GC009867, https://doi.org/10.1029/2021GC009867.Volume-dependent magnetic susceptibility (κ) is commonly used for paleoenvironmental reconstructions in both terrestrial and marine sedimentary environments where it reflects a mixed signal between primary deposition and secondary diagenesis. In the marine environment, κ is strongly influenced by the abundance of ferrimagnetic minerals regulated by sediment transport processes. Post-depositional alteration by H2S, however, can dissolve titanomagnetite, releasing reactive Fe that promotes pyritization and subsequently decreases κ. Here, we provide a new approach for isolating the detrital signal in κ and identifying intervals of diagenetic alteration of κ driven by organoclastic sulfate reduction (OSR) and the anaerobic oxidation of methane (AOM) in methane-bearing marine sediments offshore India. Using the correlation of a heavy mineral proxy from X-ray fluorescence data (Zr/Rb) and κ in unaltered sediments, we predict the primary detrital κ signal and identify intervals of decreased κ, which correspond to increased total sulfur content. Our approach is a rapid, high-resolution method that can identify overprinted κ resulting from pyritization of titanomagnetite due to H2S production in marine sediments. In addition, total organic carbon, total sulfur, and authigenic carbonate δ13C measurements indicate that both OSR and AOM can drive the observed κ loss, but AOM drives the greatest decreases in κ. Overall, our approach can enhance paleoenvironmental reconstructions and provide insight into paleo-positions of the sulfate-methane transition zone, past enhancements of OSR or paleo-methane seepage, and the role of detrital iron oxide minerals on the marine sediment sulfur sink, with consequences influencing the development of chemosynthetic biological communities at methane seeps.This research was supported by the American Chemical Society-Petroleum Research Fund Award #53006-ND8 and U.S. Department of Energy Grant #DE-FE0010120

Isolating Detrital and Diagenetic Signals in Magnetic Susceptibility Records From Methane-Bearing Marine Sediments

Volume-dependent magnetic susceptibility (κ) is commonly used for paleoenvironmental reconstructions in both terrestrial and marine sedimentary environments where it reflects a mixed signal between primary deposition and secondary diagenesis. In the marine environment, κ is strongly influenced by the abundance of ferrimagnetic minerals regulated by sediment transport processes. Post-depositional alteration by H2S, however, can dissolve titanomagnetite, releasing reactive Fe that promotes pyritization and subsequently decreases κ. Here, we provide a new approach for isolating the detrital signal in κ and identifying intervals of diagenetic alteration of κ driven by organoclastic sulfate reduction (OSR) and the anaerobic oxidation of methane (AOM) in methane-bearing marine sediments offshore India. Using the correlation of a heavy mineral proxy from X-ray fluorescence data (Zr/Rb) and κ in unaltered sediments, we predict the primary detrital κ signal and identify intervals of decreased κ, which correspond to increased total sulfur content. Our approach is a rapid, high-resolution method that can identify overprinted κ resulting from pyritization of titanomagnetite due to H2S production in marine sediments. In addition, total organic carbon, total sulfur, and authigenic carbonate δ13C measurements indicate that both OSR and AOM can drive the observed κ loss, but AOM drives the greatest decreases in κ. Overall, our approach can enhance paleoenvironmental reconstructions and provide insight into paleo-positions of the sulfate-methane transition zone, past enhancements of OSR or paleo-methane seepage, and the role of detrital iron oxide minerals on the marine sediment sulfur sink, with consequences influencing the development of chemosynthetic biological communities at methane seeps

Data report : composition of clay minerals from hemiplegic sediments at Hydrate Ridge, Cascadia subduction zone

This report describes the results of semiquantitative analysis of clay mineral composition by X-ray diffraction. The samples consist of hemipelagic mud and mudstone cored from Hydrate Ridge during Leg 204 of the Ocean Drilling Program. We analyzed oriented aggregates of the clay-sized fractions (<2 μm) to estimate relative percentages of smectite, illite, and chlorite (+ kaolinite). For the most part, stratigraphic variations in clay mineral composition are modest and there are no significant differences among the seven sites that were included in the study. On average, early Pleistocene to Holocene trench slope and slope basin deposits contain 29% smectite, 31% illite, and 40% chlorite (+ kaolinite). Late Pliocene to early Pleistocene strata from the underlying accretionary prism contain moderately larger proportions of smectite with average values of 38% smectite, 27% illite, and 35% chlorite (+ kaolinite). There is no evidence of clay mineral diagenesis at the depths sampled. The expandability of smectite is, on average, equal to 64%, and there are no systematic variations in expandability as a function of burial depth or depositional age. The absence of clay mineral diagenesis is consistent with the relatively shallow sample depths and corresponding maximum temperatures of only 24°–33°C

Data report : isotopic characterization of dissolved inorganic carbon in pore waters, leg 204

Isotopic characterization of carbon in the dissolved inorganic carbon (DIC) pool is fundamental for a wide array of scientific studies directly related to gas hydrate research. In order to generate integrated and internally consistent data of δ¹³C of DIC in pore waters from Hydrate Ridge, we used the modern continuous flow technology of a GasBench II automated sampler interfaced to a gas source stable isotope mass spectrometer for the rapid determination (~80 samples/day) of δ¹³C DIC in small-volume water samples. The overall precision of this technique is conservatively estimated to be better than ±0.15‰ (1 σ), which is similar to the precision of methods in current use. Here we present the data generated from Ocean Drilling Program Leg 204 pore water samples

Embolización cartilaginosa en la aorta abdominal secundaria a una lesión arterioesclerótica en la aorta torácica en un perro

Se describe un caso de paraplegia aguda no progresiva en una perra adulta ocasionado por una embolización cartilaginosa en la aorta abdominal cuyo origen se encontraba en una lesión arterioesclerótica en la aorta torácica.

Variability of Baccharis crispa Spreng. wild populations in the Province of Córdoba, Argentina

Entre las plantas medicinales de Argentina registradas en la Farmacopea, se encuentra la especie Baccharis crispa Spreng.,"carqueja". Es un subarbusto rizomatoso, dioico, con ramas provistas de tres alas, de 2 a 6 mm de ancho. Según el Índice de Prioridad de Conservación (elaborado para el Valle de Paravachasca de la Provincia de Córdoba), la carqueja se encuentra tercera en orden de importancia como prioritaria para su conservación. De manera general, la conservación abarca la preservación y la utilización sostenible de los recursos genéticos, protegiendo la variabilidad, esencial para su mantenimiento. El objetivo del presente trabajo fue determinar la existencia de variabilidad, a partir de datos de evaluaciones morfológicas, químicas y edafológicas, entre poblaciones silvestres de Baccharis crispa Spreng. de la Provincia de Córdoba, Argentina. En cuanto al estudio de la variación entre las poblaciones, se comprobó la existencia de variabilidad entre ellas y se determinaron las variables que permiten la diferenciación entre las poblaciones. Se encontró que las tres series de variables estudiadas tuvieron un importante grado de consenso para discriminar entre las cuatro poblaciones evaluadas.Baccharis crispa Spreng., "Carqueja", is found among the medicinal plants of Argentina, registered in the pharmacopoeia, the species. It is a rhizomatous dioic subshrub, with branches provided with three wings, 2 to 6 mm wide. According to the Conservation Priority Index (developed for the Paravachasca Valley of the Province of Córdoba), the carqueja is third in order of importance as a priority for conservation. In general, conservation includes the preservation and sustainable use of genetic resources, protecting their variability, which is essential for their maintenance. The aim of this study was to determine the existence of variability, from morphological, chemical, and edaphic data among wild populations of Baccharis crispa in the Province of Córdoba, Argentina. We confirmed the existence of variability among the study populations, and determined the variables that allowed their differentiation. It was found that the three sets of the studied variables had a signifcant consensus degree to discriminate among the four evaluated populations.Fil: Chaves, Ana Guadalupe. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bruentti, P. C.. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; ArgentinaFil: Massuh, Yamile. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ocaño, Sonia Fabiana. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; ArgentinaFil: Torres, L. E.. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; ArgentinaFil: Ojeda, Marta Susana. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin