Preservation Of Organic Matter Research Articles

Revealing the potential of organo-mineral complexes in agricultural application using bibliometrics

Organo-mineral complexes (OMCs) are referred to as biogeochemical black boxes and are widely thought to contribute to the long-term preservation of organic matter. However, the history and potential research directions of OMC research, as well as the deep applications of OMCs, have not been fully investigated. We conducted a comprehensive bibliometric study based on the Science Citation Index core database publications from 1959 to 2020 to fill this research gap in OMC studies. The results showed that a total of 751 publications involving OMCs (OMCPs) were published. There was a significant positive correlation between the frequency of international associations and the number of OMCPs. A dendrogram containing six categories and 130 keywords was constructed to represent the research content of OMCPs. In particular, the keyword co-occurrence analysis and a laboratory-scale practice jointly verified the feasibility of using silicate minerals and manure compost to produce synthetic OMCs. The life span prediction analysis revealed that the research on OMCs is in the climax stage, while the current number of studies is still less than 50% of the saturation amount. The two most potentially promising research directions are the use of OMCs in agriculture and pollutant control, which currently account for less than 30% and 25% of the saturation amount, respectively. This report clarified the research gap and predicted the development trend of OMC research using bibliometrics for the first time, and highlighted the importance of OMCs in improving agricultural production while stabilizing pollutant migration in agricultural soil.

Geochemical factors associated with deposition of lower Aptian organic-rich sediments during OAE1a in the Basque-Cantabrian Basin, northern Spain

Introduction: The Early Aptian Oceanic Anoxic Event 1a (OAE1a) is characterized by organic matter (OM) bearing rocks identified worldwide, which also occur in the hemipelagic succession of the Cuchía section, North Basque-Cantabrian Basin (NBCB) in Northern Spain. Previous works identified OAE1a using δ13C calibrated with biostratigraphy of planktonic foraminifera, calcareous nannoplankton, and ammonites. However, the geochemical characteristics that controlled OM sources and the redox conditions during OAE1a are yet to be determined. Therefore, here we present the results of a high-resolution complementary study along 67 m of the succession at Playa de los Caballos beach that highlights how local factors in the basin modulated the effects of increased precipitation during enhanced global hydrological cycles.Methods: Samples were analyzed for total inorganic carbon (TIC), total organic carbon (TOC), δ13C, major elements (Al, Ti, Si), redox sensitive trace elements (RSTEs), clay mineralogy, bulk mineralogy, and biomarkers.Results and Discussion: Carbon isotope segments C2 to C6 were recognized to determine the age of the outcrop. Lipid biomarkers indicated that OM is predominantly marine with significant terrestrial contribution. Terrigenous OM was carried to the basin through pulses of fluvial input as attested by the major elements and by high relative proportions of quartz, feldspar, and clay minerals. Increased terrestrial inputs also enhanced primary production and facilitated OM preservation. Periods with hightened RSTE content correspond with increases in the major elements, thus implying their common provenance. High sedimentation rates together with the presence of less labile OM and the interaction with clay minerals most likely played a major role in preserving the OM. This study further highlights how enhanced hydrological cycles significantly influenced the marine conditions that controlled the expression of OAE1a in the NBCB.

Carbon cycle during the late Aptian–early Albian OAE 1b: A focus on the Kilian–Paquier levels interval

The Oceanic Anoxic Event (OAE) 1b took place over a protracted time interval during the Aptian/Albian boundary interval, at the dawn of the mid-Cretaceous climatic optimum. OAE 1b is characterized by the occurrence of several sub-events recorded by organic matter-rich levels, which can be traced on regional-to-global scale. Previous studies have highlighted that the climax of the event occurred around the Kilian – Paquier interval, with this latter sub-event being the most extended and pronounced stratigraphic interval. Numerous studies on OAE 1b have however only focused on high-precision investigations of the Kilian and/or Paquier levels, leaving vast uncertainties about the environmental changes and their drivers during the entire OAE 1b, and hence also on the mechanisms leading to the formation of the sub-events themselves. In this study, we have performed a high-resolution multi-proxy analysis of the Briers section, a well-exposed section in the Blue Marls Formation of the SE France Vocontian Basin, continuously covering the Kilian – Paquier interval. Pyrolysis analyses show that most of the organic matter in this section is immature and of continental origin, averaging 1.5% TOC. The Kilian and Paquier levels are characterized by higher TOC values and a substantial increase in the amount of marine organic matter. Comparing TOC values with changes in Al or Ti concentration (proxies for continental weathering) and Hydrogen index (HI values, tracer for the type of organic matter) reveals that the background long-term change in TOC is linked to change in the continental organic matter delivery to the Vocontian Basin tied to changes in continental weathering rates. Sporadic increases in TOC values associated with the Kilian, HN 8, and Paquier levels, are most likely the result of short-lived events of increased marine primary productivity and organic matter preservation superimposed on the background influx of continental organic matter. A high-resolution bulk organic matter carbon isotope record shows that, apart from the Paquier level, all the fluctuations observed in the carbonate carbon isotope ratios are also mirrored in the organic matter record, although with higher amplitudes. This discrepancy in amplitude can be resolved by correcting the bulk organic matter carbon isotope record for fluctuations in the type of organic matter, demonstrating that both oceanic and atmospheric reservoirs were affected by similar carbon isotope fluctuations, which were hence of global extent. The abnormal bulk organic matter carbon isotope record of the Paquier level further confirms the large geographical expansion of unusual organic matter production and/or accumulation during this peculiar event. Overall, this study suggests that Milankovitch-paced (long eccentricity) changes in monsoonal activity and their effect on the accumulation of organic matter in continental wetlands best explains the rhythmic change in the global carbon isotope record across the OAE 1b interval.

Organic matter sulfurization and organic carbon burial in the Mesoproterozoic

Throughout the Proterozoic Era, sedimentary organic carbon burial helped set the pace of global oxygenation and acted as a major modulator of atmospheric CO2 and climate. Although Proterozoic rocks generally contain low concentrations of organic matter (OM), there are key exceptions to this rule, including the relatively OM-rich Arctic Bay shales from Baffin Island, Canada (Bylot Supergroup, Borden Basin, ∼1.05 Ga). The mechanisms driving elevated OM concentrations in these and other Proterozoic shales remain poorly understood. In the Mesozoic and Cenozoic, organic matter sulfurization can be a major driver of enhanced OM burial across a range of redox conditions comparable to those inferred for many Proterozoic environments. Therefore, in this study, we evaluate the role of sulfurization in driving OM preservation in the Mesoproterozoic Borden Basin and discuss its relevance to Proterozoic systems in general. We present the first evidence for syngenetic-to-early-diagenetic OM sulfurization in a Proterozoic basin, which begins to fill a several-billion-year gap in our record of organic S across Earth history. We find that OM sulfurization was particularly extensive in shales from a relatively shallow-water section (Alpha River) but less extensive in shales deposited in deeper water (Shale Valley), which is consistent with models that infer sulfidic ‘wedges’ or O2-minimum-zone-type structures on shelf margins at least intermittently at this time. At the shallower site, organic S and pyrite are similarly 34S-depleted and thus likely formed at roughly the same time near the sediment–water interface under conditions previously interpreted to have been ferruginous to intermittently sulfidic. In contrast, at the deeper-water site, large S-isotope differences between pyrite and organic S along with low apparent OM sulfurization intensities indicate that pyrite formation was favored over OM sulfurization during early sedimentation under variable but primarily ferruginous conditions. Although Mesoproterozoic biomass can be substantially sulfurized, indicators of sulfurization intensity are not correlated with OM concentrations, and therefore sulfurization does not appear to have been the primary driver of enhanced OM concentrations in Arctic Bay Formation shales. The link between sulfurization and total OM preservation may have been modulated during the deposition of Arctic Bay Formation shales by differences in iron availability, nutrient cycling, and particle dynamics in the Mesoproterozoic.

Controls on Organic Matter Accumulation from an Upper Slope Section on the Early Cambrian Yangtze Platform, South China

The early Cambrian witnessed profound environmental changes and biological evolution in Earth’ history. During this period, organic-rich shales were widely distributed over almost the entire Yangtze Block. However, the dominant factor that drove the significant accumulation of organic matter (OM) remains controversial and is still debated. Here, we analyzed TOC, organic carbon isotopes, iron speciation, major and trace elements for the lower Cambrian Niutitang Formation in the upper slope Meiziwan section, to investigate the dominant factor controlling OM accumulation. High contents of TOC and Baxs reveal an OM-enriched feature of the Niutitang Formation, and the coupled relationship between them suggest a strong production control on OM accumulation at Meiziwan. Meanwhile, negative relationships between TOC and chemical index of alteration (CIA) values as well as Al contents suggest that influence of chemical weathering and terrestrial input on OM accumulation were limited. Fairly low CoEF × MnEF values provide strong evidence that the deposition of organic-rich shales was under the control of oceanic upwelling event. The upwelling event would bring nutrient-rich deep waters into surface water, stimulating phytoplankton bloom and primary productivity in surface water and facilitating OM enrichment. Meanwhile, enhanced accumulation of OM would have promoted subsequent bacterial sulfate reduction, leading to the occurrence of occasional euxinia (evidenced by iron speciation and redox-sensitive trace element data) and promoting preservation of OM. Taken together, our results shed light on the critical role of oceanic upwelling on the marine primary productivity on the earliest Cambrian Yangtze Platform.

Detection of organic matter on Mars, results from various Mars missions, challenges, and future strategy: A review

This review paper summarizes the literature on the organic matter detection by various Mars lander/rover missions, in order to understand the progress towards dealing with methodological challenges in the analysis of the Martian regolith and drilled mudstone samples. This paper shows that Martian missions are so far successful in detecting simple and some complex organic molecules, but their origin i.e., whether sourced by cosmic dust, meteoric bombardment, geochemical reduction of inorganic carbon during hydrothermal or igneous activity, or produced biologically in the ancient habitable Martian deposition environment, remains unknown. The preservation of organic matter in the Martian depositional realm has also been found as one of the biggest hurdles in its search. Therefore, upcoming ExoMars mission has been equipped with the instruments that would be able to drill and retrieve 2 m subsurface cores for organic matter analysis, with the assumption that the subsurface samples would have better chances of preserving original organic matter from the disintegration by ultraviolet (UV) radiation, galactic cosmic rays, and solar energetic particles. In addition to the method used for organic matter detection in previous missions [simple pyrolysis-GCMS and the use of combination of thermal combustion and derivatization (thermochemolysis)-GCMS], other alternative organic matter detection methodologies i.e., Raman spectroscopy (laser 523) plus deep resonant Raman and fluorescence spectroscopy are used in Mars 2020 Perseverance rover and will be used in ExoMars mission as well. Learning from the past and upcoming Mars missions will help in developing strategies and tools for the future Martian missions with goal to better understand it is ancient habitability.

Isotopic and spectral signatures unravel the sources, preservation and degradation of sedimentary organic matter in the Dongzhai Harbor mangrove estuary, southern China

Sedimentary organic matter (SOM) production and transformation processes have a prominent role in regulating biogenic element cycling in mangrove ecosystems. However, aquaculture biodeposits can substantially affect source apportionments and biogeochemical processes of SOM within mangroves. In this study, natural stable isotopes (13C and 15N), spectral techniques, and hydrogeochemical analysis were used to elucidate the sources, preservation, and degradation of SOM across the Dongzhai Harbor (DZH) estuary, southern China, where aquaculture systems are extensive. Along the estuarine salinity gradient, sediment and bottom water samples were collected from the upper fluvial mangrove zones to the lower marine endmember. Results indicated that source contributions to SOM along the estuarine gradient were spatially heterogeneous. Aquaculture-derived organic matter was the largest contributor to the Sanjiang River (44.29 %) in the upper estuary, and terrestrial sources from C3 mangrove forests were highest in the Yanfeng East River (62.87 %) near the middle estuary. Farther seaward, marine plankton sources were elevated in the Dongzhai Harbor channel (64.15 %) and Yanfeng West River (48.83 %) of the lower estuary. The terrestrial/microbial humic-like component (C1), tryptophan-like component (C2), and soil-derived fulvic acid (C3) were identified from the samples using fluorescence excitation emission matrices and parallel factor analysis (EEM-PARAFAC). Results show that in the upper and middle estuary, SOM was preserved by sedimentation due to the abundance of fine-grained aquaculture-derived biodeposits, weak hydrodynamic conditions, and the formation of Fe/Mn-humus complexes. In contrast, in the lower estuary, SOM originated from marine plankton and was rapidly degraded via aerobic respiration. Moreover, correlations between δ13C and δ15N values vs C/N ratios further suggest progressive SOM degradation from initial diagenesis to post-depositional geochemical processes. This study provides new insights into aquacultural and environmental factors controlling SOM preservation and degradation within estuaries. The findings have implications for shoreline stability and the protection and restoration of estuarine mangrove wetlands.

Humus and nitrogen content of sod-podzolic soil under the influence of biopreparations for potato cultivation

In organic potato cultivation technologies, various biopreparations are used, which have a considerable impact on both the growth and development of crops, and on soil fertility indicators, which is especially important for sod-podzolic soils characterised by low potential fertility. The purpose of the study is to establish the changes in humus content and mineral nitrogen in sod-mediumpodzolic loam soil under the influence of biopreparations for the decomposition of white mustard as a cover crop and for the treatment of potato tubers and vegetative potato plants. In a two-factor experiment, the following factors were examined: factor 1: control without a destructor and “Ecostern” destructor at a dosage of 1.2 litres per hectare; factor 2: nine options of biopreparations application, including Agat, Regoplant, Mycohelp, Phytohelp, and Stimpо. Soil samples were collected from the 0-30 cm layer of sod-medium-podzolic sandy loam soil on water-glacial deposits. In them, the total humus content was established by the Tyurin method, and the mineral nitrogen content was calculated as the sum of ammonium and nitrate nitrogen determined potentiometrically. The application of the destructor on the green biomass of the cover crop contributed to an increase in the humus content in the 0-30 cm soil layer, where it ranged from 1.135% to 1.24%, compared to 1.025% to 1.15% in the options without the use of the bio-destructor. A reverse dependence was observed in terms of mineral nitrogen content. In the options with the use of the Ecostern destructor, the mineral nitrogen content was on average 2.09 mg/kg lower compared to the options without the application of the destructor. The highest humus content was observed in option 8, which involved the use of “Phytohelp” for treating potato tubers at a dosage of 1.0 litre per ton and three-fold treatment by “Phytohelp” at a dosage of 1.0 litre per hectare during the vegetation period. In the option without the destructor, the humus content was 1.15% and 1.24% with the application of the Ecostern bio-destructor. It slightly lagged behind option 9 with the “Phytohelp” biopreparations. The materials presented in the study may have practical value for agricultural enterprises engaged in growing organic potatoes to ensure the preservation and reproduction of organic matter in soils

Shale gas potential of Ordovician marine Pingliang shale and Carboniferous–Permian transitional Taiyuan-Shanxi shales in the Ordos Basin, China

The assessment of shale gas potential for the Ordovician Pingliang Formation and Carboniferous–Permian Taiyuan and Shanxi formations in the northwest margin of Ordos Basin, China provides insight into how fluctuation in depositional environments has a significant role on lithofacies and shale gas potential. To investigate the shale gas potential, a series of measurements (i.e. Rock-Eval pyrolysis, maceral composition analyses and X-ray powder diffraction, etc.) on representative outcrop samples were conducted to characterise shale properties. The organic matter from marine Pingliang shale is predominantly type I with a strong predominance of sapropelinite, whereas the transitional Taiyuan-Shanxi shales are dominated by types II to III kerogen. Furthermore, the Pingliang shale is characterised as a ‘poor’ source rock mainly owing to the lower total organic carbon (TOC) content (average 0.79 wt%) and higher maturity [average 1.78% in vitrinite reflectance (R o)], while the transitional Taiyuan-Shanxi shales are mostly characterised as ‘fair’ source rocks, and some samples with high TOC content (more than 2.0 wt%) present good source rocks. It is also found that the sedimentary environment, as a key factor determining the organic matter and TOC content, inevitably influences the type and content of minerals in shale, and controls the shale gas potential. For example, the transitional argillaceous Taiyuan-Shanxi shales are significantly different from the siliceous Pingliang shales, specifically, total clay content for the former is more than 50 wt%, while the latter is rich in quartz content (more than 70 wt%). Additionally, the quartz and clay contents of the Taiyuan shale range widely, especially the smectite content of I–S ML. The barrier coastal facies in the Taiyuan Formation are more conducive to the enrichment and preservation of organic matter because the Shanxi shale was deposited in shallow delta facies with a greater terrestrial influence. Conclusively, the Taiyuan and Shanxi formations have relatively good exploitation potential for shale gas, especially the relatively high TOC content (average 2.45 wt%) and moderate R o value (average 1.25%). For future exploration, selecting areas with relatively large shale thickness, high brittle mineral content, stable tectonics and better preservation conditions are key to optimising favourable exploration areas for shale gas. KEY POINTS The shale gas potentials of the argillaceous Taiyuan-Shanxi shales and siliceous Pingliang shale are compared. The influence of sedimentary facies on reservoir parameters of marine and transitional shales is established. This is a first detailed comparison of the marine and transitional shale gas potential in the northwest margin of Ordos Basin, China.

Shift in the Mode of Carbon Cycling Recorded by Biomarkers and Carbon Isotopic Compositions in the Yanchang Formation, Ordos Basin: Autotrophy vs Heterotrophy.

Organic-rich shales and mudstones have long been investigated regarding the control of source, environment, climate, etc. on the enrichment of organic carbon. However, little is documented about how autotrophy and heterotrophy influence organic carbon cycling/export. Here, we show molecular and carbon isotopic compositional changes of the shale or mudstone source rocks from the Chang 3 to 7 members of the Yanchang Formation. The Chang 7 member source rocks have higher quality (480-500 mg/g) and total organic carbon (TOC) (15.3% on average) than other member source rocks; the sterane/hopane ratio and the δ13C of organic carbon and kerogen decrease from the Chang 3 to 7 members, but Δδ ([average δ13C of n-C17 + n-C18] - [average δ13C of pristane + phytane]) increases, and no aryl isoprenoids and C40 aromatic carotenoids (e.g., isorenieratane) were observed. These low maturity biomarker features suggest that there were no water stratification, photic zone euxinia (PZE), and no obvious change in the organic matter source, and the water column is generally anoxic. A comparison of the δ13C of Pr and Ph with the δ13C of the n-C17 and n-C18 alkanes reveals a shift in the mode of carbon cycling/export (autotrophy versus heterotrophy) in the Yanchang Formation and that there was dominant heterotrophic bacterial activity or bacterial biomass in the Chang 7 member. The TOC spike in the Chang 7 member may result from boosted carbon cycling/export that improves organic carbon preservation than other members. Possible external forcings on the shift are abundant hydrothermal- or volcanic-derived metal salts as electron acceptors in the palaeowater, which is a reasonable explanation for enhanced heterotrophic bacterial activity. This finding improves our understanding of heterotrophic bacterial activity control on organic matter (OM) preservation and may be a significant supplement for understanding the ecological or environmental forcings in the Yanchang Formation, Ordos Basin.

Complex pattern of environmental changes and organic matter preservation in the NE Ordos lacustrine depositional system (China) during the T-OAE (Early Jurassic)

The lower Toarcian black shale and mudstone succession of the Anya section in the northeastern Ordos Basin records a climatically controlled evolution of the lacustrine system during the negative carbon isotope excursion (NCIE) of the Toarcian oceanic anoxic event (T-OAE; ca. 183 Ma). In the Anya section, petrography integrated with climate proxies (Sr/Cu and Rb/Sr) and weathering indices (weathering index of Parker, chemical index of weathering and plagioclase index of alteration), suggests that a warm-humid climate with sporadic semihumid-semiarid intervals developed during the early Toarcian and was coincident with strong chemical weathering. Sr/Ba and S/TOC ratios suggest that the Anya section's rocks were generally deposited in freshwater. Four phases (phases A, B, C and D) in lake evolution are distinguished from the variation in petrographical and geochemical proxies providing clues about the drivers of environmental change and organic matter accumulation in the lacustrine basin. Phases A and C have a high preservation of organic matter derived from lake plankton (Type II-III kerogens), were characterized by anoxia, and coincided with high primary productivity. On the contrary, phases B and D indicate a low primary productivity and suboxic-oxic conditions, with a lower organic matter content of predominantly higher land plant origin (Type III kerogen). The accumulation of organic matter was mainly controlled by changes in primary productivity and redox conditions that were tightly linked to the local sedimentary evolution of the Ordos Basin and to global and regional climate. During the early Toarcian NCIE, the accumulation of organic-poor sediment and terrestrial organic matter may have been driven by enhanced seasonality, superimposing on local lake level changes. As a consequence, the peak of the T-OAE carbon cycle perturbation does not coincide with lacustrine black shale deposition and/or peak anoxia in this continental depositional system. This emphasizes the significance of local or regional environmental change on the carbon sequestration within lacustrine systems.

Copper and Zinc isotopes trace the evolution of the Ediacara-Early Cambrian paleo-ocean redox condition in the Tarim Basin, China

The Ediacaran-early Cambrian transition is a critical period in the Earth's evolutionary history. A series of important geological and biological events are likely related to environmental change. Ocean oxygenation levels during the early Cambrian are still controversial and barely constrained although abundant geochemical studies have been conducted. The black shale widely developed in the Early Cambrian can record paleo-environmental information of contemporaneous seawater. The early Cambrian Yuertusi Formation black shale in the Luntan 3 well from the Tarim Basin was studied in terms of Cu and Zn isotopic composition and redox sensitive trace element to improve the knowledge of the extent of ocean oxygenation during the Ediacaran-Early Cambrian. The Yuertusi Formation is divided into four stages according to lithology variation and records of Cu and Zn isotopes and redox sensitive elements, indicating the fluctuation of ocean redox condition. The total organic carbon (TOC) varied widely from 0.10% to 18.25% with an average of 6.34%. Enrichment of Mo, U and V elements which have a synergistic relationship with TOC and redox proxies (ratios of U/Th and V/Cr, EF(Mo)-EF(U)) of the four stages in the Yuertusi Formation, indicate an anoxic even euxinic deposition environment, especially in stages Ⅰ and Ⅲ. Most of the Cu isotope values, lower than the modern seawater values, also indicate that the ocean state was anoxic and did not reach the current ocean oxidation level, which shows the same characteristics as the other profiles in different areas. The variation in the Cu isotope ranges from −3.10‰ to +1.23‰, and the Zn isotope ranges from 0.09‰ to 1.46‰. Relatively large Cu and Zn isotopic fractionation in stages Ⅰ and Ⅲ occur with an intense reduction environment, which is attributed to the combination of sulfide deposits that are eventually immobilized in sediments. Under the overall background of an anoxic environment, the four stages show a cycle of relative anoxic-weak oxidation-anoxic-weak oxidation, which is inferred to be connected with the transgressive-regressive cycle and weathering enhancement variation based on Ce anomaly, Mo/Toc ratios and C stable isotope data. The Early Cambrian transgression provided an anoxic even euxinic environment conducive to organic matter preservation for the development of black shale during stage Ⅰ. With the sea level fluctuation and weathering enhancement, the sea retreated gradually, productivity gradually increased, and the marine environment was relatively oxidized. The increasing trend of the whole Cu and Zn isotope values from bottom to top in the Yuertusi Formation is interpreted to be gradual relative oxidizing.

Characteristics and controlling factors of the Upper Permian Dalong Formation in northwestern Sichuan Basin, China

It has been generally accepted that the Permian shale is an important target for shale oil and gas exploration. In order to precisely predict the distribution of potential excellent source rocks of shale oil and gas, it is necessary to reveal the forming process and mechanism of high-quality source rocks, such as the Dalong Formation in the Scihuan Basin. In this study, 17 samples were collected from the Dalong Formation in Longfeng Quarry, Northwest Guangyuan City, Sichuan Province. The lithofacies, organic geochemistry, and pyrolysis of these samples were analyzed to evaluate the main factors controllingthe source rock formation. In particular, the influences of hydrothermal and paleoenvironmental conditions on the accumulation of organic matter were analyzed. The total organic carbon (TOC) content of the samples, which ranges from 0.05% to 12.21%, is closely related to the lithology. High TOC has been generally observed in rock intervals developed in a deep-water sedimentary environment, including siliceous rock, dark shale, and siliceous shale. The peak pyrolysis temperature of the samples ranges from 444°C to 462°C, indicating a mature stage. Thin-section observation, combined with the results of previous studies, has confirmed that the source of the organic matter is mainly marine phytoplankton, such as algae and radiolarians, ostracods, and other marine organisms, which consist of these high-quality source rocks. The ratio of trace elements, such as Ni/Co, V/Cr, U/Th, and V/(V + Ni) indicate that high-quality source rocks are mainly formed in anoxic restricted environments. The hydrothermal activity of submarine volcanoes provided many nutrients and compounds, resulting biological prosperity and improving primary productivity. This is simultaneously conducive to the formation of anoxic environments and the preservation of organic matter.

Geochemistry of Precambrian black shales from Ossa-Morena Zone (Portugal): depositional environment and possible source of metals

The paleodepositional environments related to Ediacaran black shales from the Série Negra succession in Ossa-Morena tectonostratigraphic zone were investigated using their geochemical composition to identify the sedimentary sources and depositional conditions. Their potential for assisting the genesis of metal deposits was also discussed. The sedimentary sources of the black shales are related to the break up of a Cadomian magmatic-arc developed in the North Gondwana realm, where the Ossa-Morena Zone was located during late Ediacaran times, showing acidic to mixed signatures. Some ratios were calculated based on redox sensitive elements, indicating both anoxic and oxic paleoenvironmental conditions. The anoxic conditions were predominant and they were identified on samples with higher organic carbon content, emphasizing that the redox conditions favored organic matter preservation and the accumulation of selected metals. Considering the mode of occurrence, the elements Ag, Cd, Cu, Pb and Se are assumed to be preferentially associated with sulfides, whereas Mo and U are preferentially organically bound. The results reveal that the black shales from the Série Negra succession in Ossa-Morena Zone might represent a source of metals, which were probably remobilized during Variscan events.

Organic matter accumulation mechanism under global/regional warming: Insight from the Late Barremian calcareous shales in the Qiangtang Basin (Tibet)

The Late Barremian (Early Cretaceous) is a global/regional warming interval. Deciphering the mechanism of organic matter (OM) accumulation in this interval could cast lights on OM accumulation mechanism under global/regional warming. This study presented high-resolution geochemical data of the Late Barremian marls and calcareous shales in the Qiangtang Basin to unravel the effect of paleoclimate and hydrothermal activity on OM enrichment, and to further discuss OM enrichment mechanism under warming climates. Our work revealed that the Late Barremian calcareous shales in the Qiangtang Basin showed high total organic carbon contents and were deposited under an anoxic-euxinic condition, high bioproductivity, and relatively stable high-salinity water mass. Hydrothermal activity was intense during this calcareous shale interval deposition. Hydrothermal fluids not only released reducing gas to increase the reducibility of water column, but also provided sufficient nutrients to enhance bioproductivity, thus facilitating the preservation and accumulation of OM. A climate transition from cold-arid to warm-humid occurred at the onset of calcareous shale deposition. A warming climate evidences in the late Barremian succession in the Qiangtang Basin suggested at least a regional warming event. The OM enrichment in the Late Barremian calcareous shales in the Qiangtang Basin was caused by the combined effect of regional (warming climate) and local (hydrothermal activity) factors. Accelerated hydrological cycle under warming climates promoted fluvial delivery of nutrients to sedimentary basins, and thus flourished bioproductivity. Local factors (e.g., hydrothermal activity and water-column stratification) facilitated OM accumulation and preservation under a warming setting.

Effects of Volcanic Activity on Organic Matter Enrichment in the Sediments and its Implications for Oil and Gas Exploration and Development

Volcanic activity is an important geological phenomenon in the evolution and development of the earth and brings rich resources to benefit human society, such as geothermal resources, valuable minerals, petroleum, and natural gas, although volcanic eruptions cause serious threats to the ecological environment of our planet. The co-development of oil and gas and volcanic activity in the same basin is a common phenomenon globally. Volcanic activity can bring abundant nutrients into the basins, conducive to the development of algae and other microorganisms in the water body. After the death of organisms, their remaining settles down to the water bottom and accumulate in the sediments. Meanwhile, reducing gases, releasing along with the volcano eruption, including H2S, CO2, etc., result in anoxia in the water body, benefiting the preservation of organic matter at the bottom and brings a large amount of material basis for the generation of oil and gas. Additionally, volcanic activity and hydrothermal fluids are rich in acid substances, will dissolve part of the minerals in the formation, generates a large number of migration channels for oil and gas migration. Some volcanic rocks are rich in pores, making them natural tanks for oil and gas storage. However, volcanic activity also has destructive effects on oil and gas accumulation. High hydrothermal/volcanic input can dilute primary productivity or reduce the abundance of organic matter due to high deposition rates, while excessive volcanic activity or hydrothermal fluid input can introduce large amounts of sulfate into the water, causing strong bacterial sulfate reduction (BSR). The high consumption of organic matter can hamper the organic matter enrichment. Therefore, how to define appropriate volcanic activity conducive to organic carbon preservation, and to establish the relationship model between volcanic activity and organic matter enrichment, are key scientific issues.

Exceptional preservation of organic matter and iron-organic colloidal mineralization in hydrothermal black smoker-type sulfide mineralization from the Paleoarchean seafloor

Fossil organic matter (OM) in Paleoarchean rocks is an invaluable tracer of ancient life, yet it is often contentious due to low preservation potentials of its original organic molecular characteristics under generally high metamorphic grades. This study reports on exceptionally preserved OM within black smoker-type sulfide mineralizations from the 3.24 billion-years-old Sulphur Springs volcanic-hosted massive sulfide deposit, East Pilbara Terrane, northwestern Australia. Fine scale mineralogical and organic molecular variations – documented by SEM and TEM techniques, Raman and FTIR Spectroscopy, as well as ToF-SIMS analysis – trace the formation of millimetre-scale pyritic hydrothermal orifices. Overmature OM (≳200–250 °C) enriched in aromatic hydrocarbons occurs within earliest formed colloform-banded pyrite that could have precipitated at high temperature upon mixing of hot hydrothermal fluids with cold seawater. In contrast, mature OM (within the catagenesis window; ∼100–150 °C) with lower proportions of aromatic hydrocarbons occasionally occurs alongside pyrite within barite near the inner paleofluid conduits of the hydrothermal orifices. A deposition of this OM generation from cooler fluids enriched in sulfate during waning hydrothermal activity is corroborated by its association with original mineralogy, particularly the occurrence of isolated nanoinclusions of OM within hydrothermal barite away from grain boundaries or fissures and cracks, which renders impossible an origin from post-depositional hydrocarbon migration. When compared to the overmature OM within colloform-banded pyrite, the better-preserved inner OM not only contains less abundant, smaller, and less ordered aromatic hydrocarbons, but also higher amounts of aliphatic molecules with longer chain lengths and higher proportions of carbonyl and amide functional groups. Although the latter characteristics are consistent with contributions by microbial biomass, abiotic origins are equally plausible because hydrothermal processes can produce OM with similar organic molecular attributes. Irrespective of these uncertainties on the ultimate sourcing of OM, common intergrowths of the cooler OM with nanoscopic iron oxides – hematite and lesser magnetite – hint at its hydrothermal deposition from colloidal particles that have been stabilized by iron-organic complexation. Further research is required to ascertain the significance of this process for the hydrothermal cycling and release of organic carbons and bound iron into the Paleoarchean oceans. Collectively, our results show that ancient marine hydrothermal systems can preserve OM with differing degrees of thermal degradation, which allows for insights into its sourcing, cycling, and deposition.

Extraordinarily High Organic Matter Enrichment in Upper Permian Wujiaping Formation in the Kaijiang-Liangping Trough, Sichuan Basin

The study of extraordinarily high organic matter content (EHOMC) is beneficial to promote the fine evaluation of shale oil and gas, but so far, there have been few studies on its mechanism. This paper carried out a comprehensive lithological and geochemical analysis of the black shales of the Wujiaping Formation in the Kaijiang-Liangping Trough. The results showed that the black shales of the Wujiaping Formation can be divided into two units (the upper and lower parts), and EHOMC occurs in its upper part. The redox-sensitive trace elements (RSTEs), MoEF-UEF covariation, and Ni/Co correlation showed that the lower part of Wujiaping Formation was a weakly restricted oxidation environment, while the upper part evolved into a sulfidation reducing environment. The productivity indicator elements (BaXS, NiXS, CuXS, P, and Mo) indicated that the upper Wujiaping Formation had higher primary productivity than the lower part. However, rare earth elements ((La/Yb)N) indicated that the deposition rate in the lower part of the Wujiaping Formation was higher than that in the upper part. In general, although the oxygenated water in the lower part of the Wujiaping Formation is not conducive to the preservation of organic matter, the high input of nutrients from land sources and the high deposition rate inhibit the decomposition of organic matter, so the lower part has a certain degree of organic matter accumulation. The sulfidation reducing environment and high paleoproductivity are the main reasons for the enrichment of organic matter in the upper part of the Wujiaping Formation. In addition, the sulfidation reducing environment and high paleoproductivity occurred during the violent upwelling at the end of Guadeloupe, a period of high sea level, these factors have jointly contributed to the enrichment of OM in the upper the Wujiaping Formation.

Sabretache from Burial 8 of the Krasnogorsk Burial Ground. Historical Aspect

The finds of purses/sabretache with front side coating of metal sheets are of considerable interest for the study of the cultural ties of the population of the Vetluga-Vyatka interfluvial area. Purses/sabretache, decorated with sheets and plates, are well known since the 10th century in the Carpathian basin and East European region, and even found on some Scandinavian burial grounds. Items of this type in the Vetluga-Vyatka interfluve were found on the Veselovsky, Rusenikha and Anatkasy burial grounds. But, unfortunately, the finds are poorly preserved, which does not allow a complete reconstruction of the items. In 2019, another handbag was found on the Krasnogorsk burial ground of Mari culture of the 10th century. A good preservation of organic matters and a comprehensive study of the details of the sabretache made it possible to reconstruct the full view of the item. The find from burial 8 of the Krasnogorsk burial ground was examined against a background of wide analogies from the medieval sites of the Carpathian basin, East European and Eurasian regions that allowed to find the place of the item in the system of international connections and to take a closer look at the issue of the genesis and ways of spread of this type of objects.

Organic matter accumulation of the Upper Triassic Ma'antang shales in the Longmenshan Foreland Basin (western Sichuan, China)

The Upper Triassic Ma'antang Formation is not only an important set of source rocks in the Sichuan Basin but may also be a successor for shale gas in China. In this study, the provenance, tectonic setting, chemical weathering, environment and productivity of the middle–late Carnian (Tuvalian) are reconstructed from petrological and geochemical data to determine the origin of the Ma'antang shales. The brachiopod-dominated fossil composition, type II-dominated organic matter, and fluctuating water salinity reflect that the shale formed in a marine environment influenced by terrestrial influx. TiO2 vs. Zr and La/Th vs. Hf diagrams, as well as the combination of major elements indicate that the Sichuan Basin was a collisional setting in the Tuvalian, and the provenance was felsic igneous source rocks. Redox-sensitive elements indicate dysoxic–anoxic conditions. Samples with Cd/Mo < 0.1 and Co*Mn > 0.4 show normal levels of Cd and relative enrichment of Mn and Co, which supports that the shale is more likely to be a product of anoxic preservation mode associated with the restricted basin. In contrast, the moderate productivity conditions reflected by Babio and P/Ti are also positive factors for organic matter accumulation. Based on the reconstruction of these environmental parameters, several driving factors that promote the formation of high TOC shales are explored. It is believed that the rapid tectonic subsidence in the early stage of foreland basin evolution (undercompensation period) created accommodation space for the shale, and the deep water also promoted anoxic bottom water, which facilitated the preservation of organic matter. The Carnian Pluvial Episode (CPE) increased global weathering and rainfall, allowing the oceans to receive more terrestrial nutrients, and freshwater influx caused stratification due to differences in salinity between the surface water and bottom water. Volcanic ash from the Wrangellia Large Igneous Province (W-LIP) and volcanic ash from local volcanoes were transported over long distances in the Late Triassic megamonsoons. Both were able to stimulate marine productivity, maintain and expand oceanic anoxia, and were beneficial for organic matter accumulation.