scholarly journals New insights into organic matter accumulation from high-resolution geochemical analysis of a black shale: Middle and Upper Devonian Horn River Group, Canada

2021 ◽  
Author(s):  
Haolin Zhou ◽  
Nicholas B. Harris ◽  
Tian Dong ◽  
Korhan Ayranci ◽  
Jilu Feng ◽  
...  
Keyword(s):  
Organic Matter ◽  
High Resolution ◽  
Second Order ◽  
Upper Devonian ◽  
Redox Conditions ◽  
Geochemical Data ◽  
Third Order ◽  
Data Set ◽  
Organic Matter Accumulation ◽  
Geochemical Proxies

Organic matter (OM) accumulation in organic matter-rich mudstones, or black shales, is generally recognized to be controlled by combinations of bioproductivity, preservation, and dilution. However, specific triggers of OM deposition in these formations are commonly difficult to identify with geochemical proxies, in part because of feedbacks that cause geochemical proxies for these controls to vary synchronously. This apparent synchronicity is partly a function of sample spacing, commonly at decimeter to meter intervals, which may represent longer periods of time than is required for the development of feedbacks. Higher resolution data sets may be required to fully interpret OM accumulation. This study applies a novel combination of technologies to develop a high-resolution geochemical data set, integrating energy-dispersive X-ray fluorescence (EDXRF) and infrared imagery analyses, to record proxies for redox conditions, bioproductivity, and clastic and carbonate dilution in millimeter-resolution profiles of 133 core slabs from the Middle and Upper Devonian Horn River shale in the Western Canada Sedimentary Basin, which provides decadal-scale temporal resolution. A comparison to a more coarsely sampled data set from the same core results in substantially different interpretations of variations in bioproductivity, redox, and dilution proxies. Stratigraphic distributions of organic matter accumulation patterns (bioproductivity-control, siliciclastic/carbonate-dilution, and redox conditions-control) show that organic enrichment events were highly varied during deposition of the shale and were closely related to second- and third-order sea-level changes. High-resolution profiles indicate that bioproductivity was the predominant trigger for organic matter accumulation in a second-order highstand, particularly during deposition of third-order transgressive systems tracts. Organic matter accumulation was largely controlled by dilution from either carbonate or clastic sediments in a second-order lowstand. Bioproductivity-redox feedbacks developed on timescales of decades to centuries.

scholarly journals Paleoenvironment and Organic Matter Accumulation of the Upper Ordovician-Lower Silurian, in Upper Yangtze Region, South China: Constraints from Multiple Geochemical Proxies

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 858
Author(s):  
Zisang Huang ◽  
Xingzhi Wang ◽  
Xiyan Yang ◽  
Rukai Zhu ◽  
Jingwei Cui ◽  
...  
Keyword(s):  
Organic Matter ◽  
Redox Conditions ◽  
Geochemical Data ◽  
Upper Ordovician ◽  
Longmaxi Formation ◽  
Structural Controls ◽  
Lower Silurian ◽  
Organic Matter Accumulation ◽  
Hypoxic Environment ◽  
Accumulation Mechanism

The origin of the organic-rich shale in the Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation is complex and controversial. This paper reports the geochemical data of Wufeng-Longmaxi Formations in the Upper Yangtze region to restore the paleoenvironment and explore the accumulation mechanism of organic matter. The total organic carbon (TOC) content of the Wufeng Formation was relatively high, with an average of 2.86%. The Lower Longmaxi Formation showed the highest TOC content, with an average of 3.99%, and the upper part was a continuously low value with an average of 1.22%. The paleoproductivity proxies (Babio, Cu/Al, Ni/Al, Siexcess) showed that in the Katian and Rhuddanian-Aeronian Stages, the Upper Yangtze Sea had high primary productivity, indicating that organic matter accumulation was more affected by terrigenous influx and redox conditions. Al, Zr, and Zr/Al indicated that terrigenous influx was relatively high in the Kaitian-Hirnantian Stages, it was at a constant low in the Rhuddanian Stage, and increased again in the Aeronian Stage. The correlations between redox-sensitive trace elements (Mo, U, V) and TOC indicate that the organic-rich shale of the Wufeng Formation was deposited in the anoxic–euxinic environment. In the Longmaxi Formation, organic-rich shales formed in a more hypoxic environment, and overlying organic-lean shales formed in a suboxic environment. Therefore, the anoxic–euxinic conditions of the Late Ordovician Yangtze Sea were the main reason for the organic matter accumulation, but the high terrigenous influx caused by regression and/or structural controls diluted the organic matter to some extent. For the Early Silurian, a complete transgression–regression cycle changed terrigenous influx and redox conditions, resulting in significant differences in organic matter accumulation.

Onset of Oceanic Anoxic Event 2 in the Lower Saxony Basin – Insights fromhigh-resolution stable isotope stratigraphy and geochemical modelling

2021 ◽  
Author(s):  
Pia Müller ◽  
Ulrich Heimhofer ◽  
Christian Ostertag-Henning
Keyword(s):  
Organic Matter ◽  
High Resolution ◽  
Stable Isotope ◽  
Carbon Cycle ◽  
Geochemical Modelling ◽  
Positive Anomaly ◽  
Lower Saxony ◽  
Data Set ◽  
Oceanic Anoxic Event ◽  
Anoxic Event

<p>The Oceanic Anoxic Event (OAE) 2 spanning the Cenomanian-Turonian boundary (93.5 Ma)<br>represents a major perturbation of the global carbon cycle and is marked by organic-rich<br>sediments deposited under oxygen-depleted conditions. In many studies the eruption of the<br>Caribbean LIP is considered to be the cause for rapidly increasing CO2 concentrations and<br>resulting global warming accompanied by widespread oceanic anoxia. In the Lower Saxony<br>Basin of northern Germany, the deposits of the OAE 2 are exposed in several industry drill<br>cores. In this study, the lower part of the OAE 2 has been studied in the HOLCIM 2011-3 drill<br>core. Sedimentary rocks are composed of limestones, marly limestones, marls and black<br>shales and have been analysed with a high-resolution stable isotope approach<br>(approximately one sample every 2 cm) combined with geochemical modelling. Using stable<br>carbon isotopes, bulk rock parameters and petrographic analysis, the onset of OAE 2 has<br>been investigated in detail. The high-resolution δ<sup>13</sup>C curve exhibits overall stable values<br>around 3 ‰ before the onset of the Plenus event. This background level is interrupted by<br>three short-lived and small but significant negative carbon isotope excursions (CIEs) down to<br>δ<sup>13</sup>C values of 2.5 ‰, 2.7 ‰ and 1.9 ‰. Immediately before the main rise in the Plenus bed,<br>a longer-lasting negative CIE down to 2.8 ‰ is observed, preceding the large positive CIE of<br>the OAE 2 to values of 5.2 ‰ over 33 ka. Thereafter, the δ<sup>13</sup>C values decrease to 3.5 ‰ over<br>a period of approximately 130 ka. The results can be correlated with the lower-resolution<br>data set of Voigt et al. (2008) but enable a more accurate characterization of the subtle<br>features of the CIE and hence events before and during this time interval. Carbon cycle<br>modelling with the modelling software SIMILE using a model based on Kump & Arthur (1999)<br>reveals that the negative excursion before the Plenus bed can be explained by a massive<br>volcanic pulse releasing of 0.95*10<sup>18</sup> mol CO2 within 14 ka. This amount corresponds to only<br>81 % of the calculated volume of CO<sub>2</sub> release during emplacement of the Caribbean LIP by<br>Joo et al. (2020). In the model the volcanic exhalation increases atmospheric CO<sub>2</sub><br>concentrations. This will increase global temperatures, intensify the hydrological cycle and<br>thus increase nutrient input into the ocean, resulting in an expansion of the oxygen minimum<br>zone, the development of anoxic conditions and an increase in the preservation potential for<br>organic material. In the model enhanced primary productivity and organic matter preservation<br>can be controlled by the implemented riverine phosphate input and the preservation factor for<br>organic matter. For the positive anomaly, the riverine phosphate input must be nearly<br>doubled (from 0.01 μmol/kg PO<sub>4 </sub>to 0.019 μmol/kg) for the period of the increasing δ<sup>13</sup>C<br>values (app. 33 ka), with a concomitant rise of the preservation factor from 1 % to 2 %. This<br>model scenario accurately reproduces the major features of the new high-resolution δ<sup>13</sup>C<br>record over the onset of the OAE 2 CIE.</p>

Cyclostratigraphic calibration of the Eifelian Stage (Middle Devonian, Appalachian Basin, Western New York, USA)

2020 ◽  
Vol 133 (1-2) ◽  
pp. 277-286 ◽  
Author(s):  
Damien Pas ◽  
Anne-Christine Da Silva ◽  
D. Jeffrey Over ◽  
Carlton E. Brett ◽  
Lauren Brandt ◽  
...  
Keyword(s):  
New York ◽  
High Resolution ◽  
Time Scale ◽  
Middle Devonian ◽  
Accurate Determination ◽  
Total Duration ◽  
Appalachian Basin ◽  
Geochemical Data ◽  
Ionization Mass ◽  
Data Set

Abstract Over the past decade the integration of astrochronology and U/Pb thermal ionization mass spectrometry dating has resulted in major improvements in the Devonian time scale, which allowed for accurate determination of ages and rates of change in this critical interval of Earth history. However, widely different durations have been published for the Middle Devonian Eifelian stage. Here we aim to solve this discrepancy by building an astronomically calibrated time scale using a high-resolution geochemical data set collected in the early to late Eifelian outer-ramp and deep-shelf deposits of the Seneca section (Appalachian Basin, Western New York, USA). The Middle Devonian Eifelian Stage (GTS2012; base at 393.3 ± 1.2 m.y. and duration estimate of 5.6 ± 1.9 m.y.), is bracketed by two major bioevents, respectively the Choteč event at its base and the Kačák event just prior to the Eifelian–Givetian boundary. To capture the record of Milankovitch-scale climatic cycles and to develop a model of the climatic and oceanographic variations that affected the Appalachian Basin during the Eifelian, 750 samples were collected at typically 2.5 cm intervals across the Seneca section. Major and trace elements were measured on each sample with an inductively coupled plasma–optical emission spectrometer. To estimate the duration of the Seneca section sampled, we applied multiple spectral techniques such as harmonic analysis, the multi-taper, and evolutionary spectral analysis, and we tuned the Log10Ti series using the short orbital eccentricity ∼100 k.y. cycle. Then, to assess the reliability of our cyclostratigraphic interpretation we ran the Average Spectral Misfit method on selected proxies for detrital input variation. The estimated duration derived using this method falls in the range of durations estimated with the tuning method. Using the approximate position of the Emsian–Eifelian and Eifelian–Givetian boundaries, constrained within <1 m, the proposed estimation of the total duration of the Eifelian age is ∼5 m.y. Interpolated from the high-resolution U-Pb radiometric age available for the Tioga F Bentonite, the numerical ages of the Emsian–Eifelian and the Eifelian–Givetian were respectively recalibrated at 393.39 Ma and 388.24 Ma. The uncertainty from the radiometric date is respectively ± 0.86 Ma and ± 0.86 Ma.

Inversion of Chromophoric Dissolved Organic Matter From EO-1 Hyperion Imagery for Turbid Estuarine and Coastal Waters

2013 ◽  
Vol 51 (6) ◽  
pp. 3286-3298 ◽  
Author(s):  
Weining Zhu ◽  
Qian Yu
Keyword(s):  
Organic Matter ◽  
High Resolution ◽  
Dissolved Organic Matter ◽  
Coastal Waters ◽  
Ocean Color ◽  
Chromophoric Dissolved Organic Matter ◽  
Significant Implication ◽  
Coastal Regions ◽  
Data Set ◽  
Wide Range

The significant implication of chromophoric dissolved organic matter (CDOM) for water quality and biogeochemical cycle leads to an increasing need of CDOM monitoring in coastal regions. Current ocean-color algorithms are mostly limited to open-sea water and have high uncertainty when directly applied to turbid coastal waters. This paper presents a semianalytical algorithm, quasi-analytical CDOM algorithm (QAA-CDOM), to invert CDOM absorption from Earth Observing-1 (EO-1) Hyperion satellite images. This algorithm was developed from a widely used ocean-color algorithm QAA and our earlier extension of QAA. The main goal is to improve the algorithm performance for a wide range of water conditions, particularly turbid waters in estuarine and coastal regions. The algorithm development, calibration, and validation were based on our intensive high-resolution underwater measurements, International Ocean Color Coordinating Group synthetic data, and global National Aeronautics and Space Administration Bio-Optical Marine Algorithm Data Set data. The result shows that retrieved CDOM absorption achieved accuracy (root mean square error (RMSE) = 0.115 m-1andR2= 0.73) in the Atchafalaya River plume area. QAA-CDOM is also evaluated for scenarios in three additional study sites, namely, the Mississippi River, Amazon River, and Moreton Bay, whereag(440) was in the wide range of 0.01-15 m-1. It resulted in expected CDOM distribution patterns along the river salinity gradient. This study improves the high-resolution observation of CDOM dynamics in river-dominated coastal margins and other coastal environments for the study of land-ocean interactive processes.

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