scholarly journals Relationships between depositional conditions and microtextures in the organic-rich Lower Oxford Clay sediments (U.K.)

1992 ◽  
Vol 6 ◽  
pp. 24-24
Author(s):  
Sophie Belin ◽  
Fabien Kenig
Keyword(s):  
Organic Matter ◽  
Sedimentation Rate ◽  
Woody Debris ◽  
Carbon Isotopic ◽  
Reducing Conditions ◽  
Geochemical Parameters ◽  
Energy Environment ◽  
Electron Mode ◽  
History Of ◽  
Quartz Grains

Six representative samples of the Lower Oxford Clay (LOC) and the Middle Oxford Clay (MOC) sediments have been assessed for total organic carbon (TOC from 1.2 to 14.2%), hydrogen indices (HI from 813 to 130), and carbon isotopic values (δ13C from −23.1 to −27.7±) (Kenig et al., this symposium), and have been extensively studied using petrographic techniques. The use of the scanning electron microscope and particularly the backscattered electron mode was emphasized as it is the most suitable tool to study the relationships between organic matter and minerals at a micrometric scale.The bulk mineralogy appears similar in all samples studied. The argillaceous matrix is predominantly composed of illite and kaolinite with detrital mineral grains of quartz, feldspar, mica (biotite and muscovite) and calcitic bioclasts (e.g. coccoliths). Diagenetic features consist mainly of dissolution of quartz grains, rim epigenization of quartz grains to kaolinite, and the presence of pyrite. The concentration of pyrite increases with the concentration of organic matter. Both framboidal and euhedral forms of pyrite are present Euhedral pyrite crystals are more abundant in organic-rich samples, indicative of the more reducing conditions occurring in the organic-rich sediments. In organic-rich samples, coccoliths are concentrated in well preserved fecal pellets, suggesting a relatively high sedimentation rate. Preservation of coccospheres indicates a low energy environment of deposition and mild diagenesis. Unusually well-preserved biotite crystals may be indicative of the proximity of sediment sources and of the weakness of diagenetic processes.In organic-rich samples, organic matter is encountered as elongated “patches” 20 to 50 μm in length and composed of several particles of marine phytoplanktonic origin; and as thin isolated particles closely associated with clays. These thin particles are both of marine phytoplanktonic and of terrestrial origin (woody debris, vegetal tissues and rare palynomorphs). In organic-poor samples, the frequency and the size (5 to 20 μm) of the patchy composite particles of phytoplanktonic organic matter decrease. Palynological studies indicated that 80% to 95% of the organic matter is amorphous and probably of marine origin. However, the proportion of structured organic matter, woody debris and vegetal tissues, increases from 5% to 20% as the TOC decreases.None of the samples studied exhibited laminations at a sub-millimetric scale. However, the organic “patches” in the organic-rich samples lie parallel to the plane of stratification even if there is no obvious stratification of the mineral matrix. Clay minerals show a random and disorganized distribution that may be indicative of microbioturbation, even in the most organic-rich samples.Organic and mineral microtextures are controlled by the environment of deposition and the diagenetic history of the sediments and are related to geochemical parameters as HI, δ13C and TOC. Microbioturbation would indicate that the water column was never anoxic. In contrast, euhedral pyrites crystals suggest anoxia in the organic-rich sediments. The decrease in size of organic “patches” with decrease in TOC, as well as the variable distribution of coccoliths, may be indicative of changes in primary productivity and sedimentation rate.

scholarly journals Origin and alteration of organic matter of the Oxford Clay Formation (U.K.) determined from bulk geochemical analyses

1992 ◽  
Vol 6 ◽  
pp. 163-163
Author(s):  
Fabien Kenig ◽  
Brian Popp ◽  
Roger Summons
Keyword(s):  
Organic Matter ◽  
Isotopic Composition ◽  
Water Column ◽  
Sedimentation Rate ◽  
Carbon Isotopic Composition ◽  
Deposit Feeder ◽  
High Sedimentation Rate ◽  
Carbon Isotopic ◽  
Shell Beds ◽  
High Sedimentation

To understand the processes controlling production, accumulation, and preservation of organic matter in the Lower Oxford Clay (LOC), we determined the hydrogen index (HI), the oxygen index (OI), the Tmax (from Rock-Eval), the content of total organic carbon (TOC), total carbon and total sulfur, and the carbon isotopic composition of bulk organic matter from 160 samples collected from 6 different quarries and one continuous core. With concentrations of TOC varying between 0.5% and 16.6%, the LOC is an organic-rich shale. For samples dominated by organic matter of phytoplanktonic origin, the hydrogen and oxygen indices and the Tmax (~418°) indicate low levels of maturity, and, thus, the shallow burial of the LOC through geologic time.Two main sources of organic matter can be distinguished: a major phytoplanktonic source with high HI and low OI and a minor terrestrial source with low HI and high OI. A third group, represented by samples with low HI and low OI, consists mainly of altered materials from the Middle Oxford Clay and the LOC. Selection of samples for chemical analysis was based on the macrofaunal assemblages defined by Duff (1975). These various biofacies are characterized by specific organic geochemical features indicating the relationship between conditions affecting faunal assemblages and those controlling accumulation and preservation of organic matter. For example, Duff's ‘deposit feeder shales', which are dominated by epifaunal bivalves and are depleted in infaunal organisms, exhibit the highest concentration and best preservation of marine organic matter, with an average TOC of 6.8% for 56 samples analyzed. The preservation of such organic matter requires a dysaerobic water column and a high sedimentation rate.Carbon isotopic compositions within the ‘deposit feeder shale’ biofacies (−27.6 to −23.2±) appear to have been controlled by the intensity of primary productivity. The highest-TOC, marine-dominated, 13C-rich samples reflect photosynthetic drawdown of dissolved-CO2 level, and, thus, originated in highly productive environments. On the other hand, variations in the carbon isotopic composition of organic matter in shell beds (−27.5 to −26±) probably reflect heterotrophic reworking of the organic matter, winnowing of the sediments, and mixing with a source of organic matter enriched in 13C, such as wood (δ13C from −25 to −23±). Such mixing phenomena may also explain the high variability of the carbon isotopic compositions of TOC-depleted and altered samples from the Middle and Upper Oxford Clay.The environment of deposition of the LOC would be characterized by the alternation of two major conditions: 1) periods of high productivity, dysoxic water column and high sedimentation rate leading to the development of organic-rich shales dominated by phytoplanktonic organic matter, and 2) periods of low productivity, oxic water column and high current activity implying winnowing and alteration of organic matter, and leading to the formation of shell beds where marine and terrestrial organic matter are mixed.

scholarly journals Depositional environment and burial history of a Lower Cretaceous carbonaceous claystone, Bornholm, Denmark

1996 ◽  
Vol 43 ◽  
pp. 133-142
Author(s):  
H. I. Petersen ◽  
J. A. Bojesen Koefoed ◽  
H. P. Nytoft
Keyword(s):  
Organic Matter ◽  
Lower Cretaceous ◽  
Depositional Environment ◽  
Lower Jurassic ◽  
Plant Litter ◽  
Burial History ◽  
Transport Distance ◽  
Geochemical Parameters ◽  
Kerogen Type ◽  
History Of

A c. 1 m thick carbonaceous claystone from the type locality of the Lower Cretaceous Skyttegård Member (Rabekke Formation), Bornholm, has been investigated by organic pétrographie and organic geochemical methods in order to assess the depositional environment of the claystone and the thermal maturity of the organic matter. The claystone was deposited in a low-energy, anoxic lake which occasionally was marine influenced. The organic matter is terrestrial and can be classified as kerogen type III and lib. Detrital organic matter and cutinite are characteristic components. The organic matter is allochthonous but the transport distance was short, and the plant material was probably mainly derived from plants growing at the edge of, or nearto, the lake. Source-specific biomarkers such as norisopimarane suggest that the plant litter was derived from a gymnospermous, low-diversity vegetation. Evidence for early angiospermous plants cannot be demonstrated with any certainty. A huminite reflectance value of 0.24%Rm and several geochemical parameters indicate that the organic matter is highly immature. It has only experienced coalification corresponding to the peat stage. Estimates show that, prior to uplift, the claystone was buried to a maximum of approximately 260 m. Reflectance data further suggest that a maximum c. 550 m thick sediment package was removed by erosion prior to deposition of the ?uppermost Jurassic-Lower Cretaceous sediments on Lower Jurassic strata.

scholarly journals The use of biological markers in determination of origin and type of organic matter in the Tisza river sediments

2014 ◽  
Vol 79 (5) ◽  
pp. 597-612 ◽  
Author(s):  
Snezana Strbac ◽  
Gordana Gajica ◽  
Aleksandra Sajnovic ◽  
Nebojsa Vasic ◽  
Ksenija Stojanovic ◽  
...  
Keyword(s):  
Organic Matter ◽  
Oil Pollution ◽  
River Sediments ◽  
Fuel Oil ◽  
Danube River ◽  
Heavy Fuel Oil ◽  
Reducing Conditions ◽  
Geochemical Parameters ◽  
Tisza River ◽  
Recent Sediments

The objective of the study was to determine the origin and type of organic matter (OM) of the Tisza recent sediments along the distance of 153 km through the territory of Serbia. For this purpose group organic-geochemical parameters and biomarker compositions were used. All samples contain approximately same amount of OM, which was deposited under uniform, slightly reducing conditions. Based on the distribution of n-alkanes, the origin and type of OM could not be precisely estimated. However, n-alkane patterns suggest the presence of immature singenetic organic matter of terrestrial origin. Distributions of terpanes and steranes and values of corresponding maturity parameters indicate that Tisza River sediments, apart from immature singenetic organic matter, contain oil pollutant of anthropogenic origin. Identical composition of these biomarkers in all samples confirms that the recent sediments of the Tisza River, from Kanjiza town to the confluence into the Danube River, contain the same type of oil pollutant. Based on the compositions of terpanes and steranes and values of biomarker parameters in Tisza sediments, it is supposed that oil pollution generally could be related to heavy fuel oil from tankers due to intense river transport and, in lower extent, to crude oils from the Elemir and Rusanda oil fields.

Elements for a General Organology

Derrida Today ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 72-94
Author(s):  
Bernard Stiegler
Keyword(s):  
Organic Matter ◽  
Planetary Scale ◽  
General Account ◽  
Inorganic Matter ◽  
History Of

These lectures outline the project of a general organology, which is to say an account of life when it is no longer just biological but technical, or when it involves not just organic matter but organized inorganic matter. This organology is also shown to require a modified Simondonian account of the shift from vital individuation to a three-stranded process of psychic, collective and technical individuation. Furthermore, such an approach involves extending the Derridean reading of Socrates's discussion of writing as a pharmakon, so that it becomes a more general account of the pharmacological character of retention and protention. By going back to Leroi-Gourhan, we can recognize that this also means pursuing the history of retentional modifications unfolding in the course of the history of what, with Lotka, can also be called exosomatization. It is thus a question of how exteriorization can, today, in an epoch when it becomes digital, and in an epoch that produces vast amounts of entropy at the thermodynamic, biological and noetic levels, still possibly produce new forms of interiorization, that is, new forms of thought, care and desire, amounting to so many chances to struggle against the planetary-scale pharmacological crisis with which we are currently afflicted.

scholarly journals Effective source rock selection and oil–source correlation in the Western Slope of the northern Songliao Basin, China

2021 ◽  
Vol 18 (2) ◽  
pp. 398-415
Author(s):  
He Bi ◽  
Peng Li ◽  
Yun Jiang ◽  
Jing-Jing Fan ◽  
Xiao-Yue Chen
Keyword(s):  
Organic Matter ◽  
Source Rock ◽  
Thermal Evolution ◽  
Songliao Basin ◽  
Source Rocks ◽  
Crude Oils ◽  
Western Slope ◽  
Geochemical Parameters ◽  
Group I ◽  
Oil Source

AbstractThis study considers the Upper Cretaceous Qingshankou Formation, Yaojia Formation, and the first member of the Nenjiang Formation in the Western Slope of the northern Songliao Basin. Dark mudstone with high abundances of organic matter of Gulong and Qijia sags are considered to be significant source rocks in the study area. To evaluate their development characteristics, differences and effectiveness, geochemical parameters are analyzed. One-dimensional basin modeling and hydrocarbon evolution are also applied to discuss the effectiveness of source rocks. Through the biomarker characteristics, the source–source, oil–oil, and oil–source correlations are assessed and the sources of crude oils in different rock units are determined. Based on the results, Gulong and Qijia source rocks have different organic matter primarily detrived from mixed sources and plankton, respectively. Gulong source rock has higher thermal evolution degree than Qijia source rock. The biomarker parameters of the source rocks are compared with 31 crude oil samples. The studied crude oils can be divided into two groups. The oil–source correlations show that group I oils from Qing II–III, Yao I, and Yao II–III members were probably derived from Gulong source rock and that only group II oils from Nen I member were derived from Qijia source rock.

Carbon Isotopic Studies of Organic Matter in Precambrian Rocks

Science ◽  
1972 ◽  
Vol 175 (4027) ◽  
pp. 1246-1248 ◽  
Author(s):  
D. Z. Oehler ◽  
J. W. Schopf ◽  
K. A. Kvenvolden
Keyword(s):  
Organic Matter ◽  
Precambrian Rocks ◽  
Carbon Isotopic ◽  
Isotopic Studies

Log landings are methane emission hotspots in managed forests

2021 ◽  
Author(s):  
Juliana Vantellingen ◽  
Sean C. Thomas
Keyword(s):  
Organic Matter ◽  
Soil Properties ◽  
Management Practices ◽  
Emission Rate ◽  
Woody Debris ◽  
Organic Matter Content ◽  
Growing Season ◽  
Matter Content ◽  
Emission Rates ◽  
Managed Forests

Log landings are areas within managed forests used to process and store felled trees prior to transport. Through their construction and use soil is removed or redistributed, compacted, and organic matter contents may be increased by incorporation of wood fragments. The effects of these changes to soil properties on methane (CH<sub>4</sub>) flux is unclear and unstudied. We quantified CH<sub>4</sub> flux rates from year-old landings in Ontario, Canada, and examined spatial variability and relationships to soil properties within these sites. Landings emitted CH<sub>4</sub> throughout the growing season; the average CH<sub>4</sub> emission rate from log landings was 69.2 ± 12.8 nmol m<sup>-2</sup> s<sup>-1</sup> (26.2 ± 4.8 g CH<sub>4</sub> C m<sup>-2</sup> y<sup>-1</sup>), a rate comparable to CH<sub>4</sub>-emitting wetlands. Emission rates were correlated to soil pH, organic matter content and quantities of buried woody debris. These properties led to strong CH<sub>4</sub> emissions, or “hotspots”, in certain areas of landings, particularly where processing of logs occurred and incorporated woody debris into the soil. At the forest level, emissions from landings were estimated to offset ~12% of CH<sub>4</sub> consumption from soils within the harvest area, although making up only ~0.5% of the harvest area. Management practices to avoid or remediate these emissions should be developed as a priority measure in “climate-smart” forestry.

scholarly journals Biomass of Coarse Woody Debris Following Fire and Clearcutting in Lodgepole Pine Forests

1997 ◽  
Vol 21 ◽  
pp. 33-35
Author(s):  
Dennis Knight ◽  
Daniel Tinker
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Coarse Woody Debris ◽  
Significant Contribution ◽  
Woody Debris ◽  
Mineral Soil ◽  
Primary Source ◽  
Timber Harvesting ◽  
Micro Organisms

In forest ecosystems, the decomposition of coarse woody debris, woody roots, twigs, leaves and micro-organisms is a primary source of mineral soil organic matter. Primary productivity, the accumulation of nutrients, and other important ecosystem processes are largely dependent on the mineral soil organic matter that has developed during hundreds or thousands of years. Large quantities of coarse woody debris are typically produced following natural disturbances such as fires, pest/pathogen outbreaks, and windstorms, and make a significant contribution to the formation of soil organic matter (SOM). In contrast, timber harvesting often removes much of the coarse woody debris (CWD), which could result in a decrease in the quantity and a change in the quality of mineral soil organic matter.

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