scholarly journals Complex Biomineralization Pathways of the Belemnite Rostrum Cause Biased Paleotemperature Estimates

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1406
Author(s):  
René Hoffmann ◽  
Benjamin J. Linzmeier ◽  
Kouki Kitajima ◽  
Gernot Nehrke ◽  
Martin Dietzel ◽  
...  
Keyword(s):  
Isotope Fractionation ◽  
Pore Space ◽  
Liquid Ratio ◽  
Ambient Seawater ◽  
Temperature Bias ◽  
Temperature Calculation ◽  
Significant Obstacle ◽  
Isotope Equilibrium ◽  
Carbonate Precursor

Paleotemperatures based on δ18O values derived from belemnites are usually “too cold” compared to other archives and paleoclimate models. This temperature bias represents a significant obstacle in paleoceanographic research. Here we show geochemical evidence that belemnite calcite fibers are composed of two distinct low-Mg calcite phases (CP1, CP2). Phase-specific in situ measurement of δ18O values revealed a systematic offset of up to 2‰ (~8 °C), showing a lead–lag signal between both phases in analyses spaced less than 25 µm apart and a total fluctuation of 3.9‰ (~16 °C) within a 2 cm × 2 cm portion of a Megateuthis (Middle Jurassic) rostrum. We explain this geochemical offset and the lead–lag signal for both phases by the complex biomineralization of the belemnite rostrum. The biologically controlled formation of CP1 is approximating isotope fractionation conditions with ambient seawater to be used for temperature calculation. In contrast, CP2 indicates characteristic non-isotope equilibrium with ambient seawater due to its formation via an amorphous Ca-Mg carbonate precursor at high solid-to-liquid ratio, i.e., limited amounts of water were available during its transformation to calcite, thus suggesting lower formation temperatures. CP2 occludes syn vivo the primary pore space left after formation of CP1. Our findings support paleobiological interpretations of belemnites as shelf-dwelling, pelagic predators and call for a reassessment of paleoceanographic reconstructions based on belemnite stable isotope data.

scholarly journals Cyclic Subcritical Water Injection into Bazhenov Oil Shale: Geochemical and Petrophysical Properties Evolution Due to Hydrothermal Exposure

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4570
Author(s):  
Aman Turakhanov ◽  
Albina Tsyshkova ◽  
Elena Mukhina ◽  
Evgeny Popov ◽  
Darya Kalacheva ◽  
...  
Keyword(s):  
Energy Demand ◽  
Oil Shale ◽  
Oil And Gas ◽  
Subcritical Water ◽  
Pore Space ◽  
Water Injection ◽  
Microstructural Properties ◽  
Gas Generation ◽  
Geochemical Parameters

In situ shale or kerogen oil production is a promising approach to developing vast oil shale resources and increasing world energy demand. In this study, cyclic subcritical water injection in oil shale was investigated in laboratory conditions as a method for in situ oil shale retorting. Fifteen non-extracted oil shale samples from Bazhenov Formation in Russia (98 °C and 23.5 MPa reservoir conditions) were hydrothermally treated at 350 °C and in a 25 MPa semi-open system during 50 h in the cyclic regime. The influence of the artificial maturation on geochemical parameters, elastic and microstructural properties was studied. Rock-Eval pyrolysis of non-extracted and extracted oil shale samples before and after hydrothermal exposure and SARA analysis were employed to analyze bitumen and kerogen transformation to mobile hydrocarbons and immobile char. X-ray computed microtomography (XMT) was performed to characterize the microstructural properties of pore space. The results demonstrated significant porosity, specific pore surface area increase, and the appearance of microfractures in organic-rich layers. Acoustic measurements were carried out to estimate the alteration of elastic properties due to hydrothermal treatment. Both Young’s modulus and Poisson’s ratio decreased due to kerogen transformation to heavy oil and bitumen, which remain trapped before further oil and gas generation, and expulsion occurs. Ultimately, a developed kinetic model was applied to match kerogen and bitumen transformation with liquid and gas hydrocarbons production. The nonlinear least-squares optimization problem was solved during the integration of the system of differential equations to match produced hydrocarbons with pyrolysis derived kerogen and bitumen decomposition.

scholarly journals A microscopic approach to investigate bacteria under in situ conditions in sea-ice samples

2001 ◽  
Vol 33 ◽  
pp. 304-310 ◽  
Author(s):  
Karen Junge ◽  
Christopher Krembs ◽  
Jody Deming ◽  
Aaron Stierle ◽  
Hajo Eicken
Keyword(s):  
Sea Ice ◽  
Pore Space ◽  
Three Dimensional ◽  
Epifluorescence Microscopy ◽  
Microbial Populations ◽  
Microbial Life ◽  
Dimensional Network ◽  
In Situ Conditions ◽  
Fluorescent Stain

AbstractMicrobial populations and activity within sea ice have been well described based on bulk measurements from melted sea-ice samples. However, melting destroys the micro-environments within the ice matrix and does not allow for examination of microbial populations at a spatial scale relevant to the organism. Here, we describe the development of a new method allowing for microscopic observations of bacteria localized within the three-dimensional network of brine inclusions in sea ice under in situ conditions. Conventional bacterial staining procedures, using the DNA-specific fluorescent stain DAPI, epifluorescence microscopy and image analysis, were adapted to examine bacteria and their associations with various surfaces within microtomed sections of sea ice at temperatures from −2° to −15°C. The utility and sensitivity of the method were demonstrated by analyzing artificial sea-ice preparations of decimal dilutions of a known bacterial culture. When applied to natural, particle-rich sea ice, the method allowed distinction between bacteria and particles at high magnification. At lower magnifications, observations of bacteria could be combined with those of other organisms and with morphology and particle content of the pore space. The method described here may ultimately aid in discerning constraints on microbial life at extremely low temperatures.

scholarly journals Oxygen isotope equilibrium in brachiopod shell fibres in the context of biological control

2008 ◽  
Vol 72 (1) ◽  
pp. 239-242 ◽  
Author(s):  
M. Cusack ◽  
A. Pérez-Huerta ◽  
P. Chung ◽  
D. Parkinson ◽  
Y. Dauphin ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Isotope Composition ◽  
Seawater Temperature ◽  
Environmental Data ◽  
Ambient Seawater ◽  
Secondary Layer ◽  
Vital Effect ◽  
Vital Effects ◽  
Stable Oxygen ◽  
Isotope Equilibrium

With their long geological history and stable low-Mg calcite shells, Rhynchonelliform brachiopods are attractive sources of environmental data such as past seawater temperature (Buening and Spero, 1996; Auclair et al., 2003; Brand et al., 2003; Parkinson et al., 2005). Concerns about the influence of vital effects on the stable isotope composition of brachiopod shells (Popp et al., 1986), led to isotope analyses of different parts of brachiopod shells in order to identify those parts of the shell that are influenced by any vital effect and those parts that may be suitable recorders of seawater temperature via stable oxygen isotope composition (Carpenter and Lohmann, 1995; Parkinson et al., 2005). Such detailed studies demonstrated that the outer primary layer of acicularcalcite is isotopically light in both δ18O and δ13C while the secondary layer, composed of calcite fibres, is in oxygen-isotope equilibrium with ambient seawater(Fig. 1) (Parkinson et al., 2005).

THE VARIATION OF IN SITU MEASURED SOIL WATER PROPERTIES WITHIN SOIL MAP UNITS

1980 ◽  
Vol 60 (3) ◽  
pp. 497-509 ◽  
Author(s):  
G. C. TOPP ◽  
W. D. ZEBCHUK ◽  
J. DUMANSKI
Keyword(s):  
Pore Space ◽  
Size Distributions ◽  
Water Capacity ◽  
Intermediate Group ◽  
Pore Size Distributions ◽  
Soil Units ◽  
Soil Water Properties ◽  
Soil Unit

The in situ saturated hydraulic conductivities of nine soil units were measured and cores of the same soil were taken to the laboratory for determination of desorption water capacity relationships. Hydraulic conductivities for the coarse- and fine-textured soils were equivalent and higher than that for medium-textured soils. However, the coarse- and fine-textured soils showed measurably different desorption curves for each of three soil units tested. Variability of duplicate measurements of hydraulic conductivity at sites were found to be considerably less than that of the soil unit as a whole. The highly variable in situ hydraulic conductivities resulted in separations of two groups of soil with significantly different values. A third intermediate group was not significantly different from the other two. The desorption curves were discussed in relation to differences in pore size distributions, identifying proportions of the pore space attributable to structural pores and to textural pores.

A flow-through reaction cell that couples time-resolved X-ray diffraction with stable isotope analysis

2011 ◽  
Vol 44 (2) ◽  
pp. 429-432 ◽  
Author(s):  
Andrew J. Wall ◽  
Peter J. Heaney ◽  
Ryan Mathur ◽  
Jeffrey E. Post ◽  
Jonathan C. Hanson ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Stable Isotope Analysis ◽  
Isotope Fractionation ◽  
Isotope Analysis ◽  
X Ray Diffraction ◽  
Reaction Cell ◽  
Time Resolved ◽  
X Ray ◽  
Flow Through

A non-metallic flow-through reaction cell is described, designed forin situtime-resolved X-ray diffraction coupled with stable isotope analysis. The experimental setup allows the correlation of Cu isotope fractionation with changes in crystal structure during copper sulfide dissolution. This flow-through cell can be applied to many classes of fluid–mineral reactions that involve dissolution or ion exchange.

15 years of in situ cement–argillite interaction from Tournemire URL: Characterisation of the multi-scale spatial heterogeneities of pore space evolution

2011 ◽  
Vol 26 (12) ◽  
pp. 2159-2171 ◽  
Author(s):  
S. Gaboreau ◽  
D. Prêt ◽  
E. Tinseau ◽  
F. Claret ◽  
D. Pellegrini ◽  
...  
Keyword(s):  
Pore Space ◽  
Multi Scale

scholarly journals Evaluation of two genera of benthic foraminifera for down-core paleotemperature studies in the western south atlantic

2006 ◽  
Vol 54 (1) ◽  
pp. 75-84 ◽  
Author(s):  
Karen B. Costa ◽  
Felipe A. L. Toledo ◽  
Maria A.G. Pivel ◽  
Cândido A.V. Moura ◽  
Farid Chemale Jr.
Keyword(s):  
Isotopic Composition ◽  
Water Temperature ◽  
Benthic Foraminifera ◽  
Small Difference ◽  
Oxygen Isotopic Composition ◽  
South Atlantic ◽  
Ambient Seawater ◽  
Oxygen Isotopic ◽  
Isotope Equilibrium ◽  
Equilibrium Oxygen

In this study we have compared the oxygen isotopic composition of two genera of benthic foraminifera (Uvigerina and Cibicidoides) from core-top samples with modern oxygen isotopic composition of seawater (delta18O). Based on a new relationship between delta18O and salinity for the mid-latitude western South Atlantic, we estimated the isotopic composition of equilibrium calcite (delta18Oeq) using two different equations: (1) O'Neil et al. (1969), modified by McCorkle et al. (1997) and (2) Kim & O'Neil (1997). When using (1), the small difference between delta18Oeq and delta18O of Uvigerina suggests that this genus precipitates its shell close to equilibrium with ambient seawater. The delta18O Cibicidoides data are 0.82 ‰ lower than the predicted (equilibrium) oxygen isotopic composition. Conversely, using (2) the Cibicidoides delta18O data show excellent agreement with the oxygen isotopic composition predicted from delta18O and water temperature while Uvigerina delta18O data are 0.69 ‰ higher than predicted oxygen isotope equilibrium values. Based on the evidences presented here and on the results from previous studies we suggest using the genus Cibicidoides and applying Kim & O'Neil's (1997) equation for down-core paleotemperature investigations. In the absence of enough Cibicidoides specimens we suggest using Uvigerina delta18O data and applying a correction factor of -0.69 ‰.

THE DEUTERIUM ISOTOPE EFFECT AND THE MOLECULAR DYNAMICS OF WATER IN BENZENE

1966 ◽  
Vol 44 (24) ◽  
pp. 3009-3015 ◽  
Author(s):  
D. C. Moule
Keyword(s):  
Isotope Fractionation ◽  
Near Infrared ◽  
Deuterium Isotope Effect ◽  
Liquid Benzene ◽  
Least Squares Fit ◽  
Equilibrium Data ◽  
Solvent Shifts ◽  
Isotope Equilibrium ◽  
Infrared Frequencies ◽  
Fractionation Factors

Infrared spectra of H2O and D2O in benzene have been recorded and the solubilities of light and heavy water in benzene from 10 to 50 °C measured. Isotope fractionation factors for the distribution of HDO and H2O between the vapor and liquid benzene phases were calculated from the relative solubilities and the vapor pressure ratios of pure H2O and D2O. The isotope equilibrium data was fitted to the expression ln α = −A/T2 + B/T and interpreted by the Bigeleisen formulism. The intramolecular B term was determined from the solvent shifts of the near infrared frequencies and the intermolecular A term calculated by a least squares fit to the isotope equilibrium data. Spectral and equilibrium data were combined to give [Formula: see text].

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