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Abstract: Globally, soils contain an estimated 1500GT of carbon, over twice that present in the atmosphere (IPCC, 2001). However the role of soils in the global carbon cycle remains highly contentious. Soil erosion redistributes organic matter (OM) within landscapes, and takes place at a range of scales from mass movement to interrill erosion. It is known that interrill erosion occurring on clay-rich stable soils causes sediment to become enriched in OM by up to a factor of 6.2 (Mora et al., 2007). However, maintenance of mass dictates that such enrichment can only be temporary unless erosion ceases due to armouring. The lack of studies showing a decline in OM erosion is attributed to the well-aggregated, slow-crusting soils used in such research. Thus, this investigation aimed to investigate the erosion of OM from rapid-crusting, sandy soils. Soils from both organically and conventionally farmed land from Shropshire, UK, were exposed to simulated rainfalls differing in both intensity and kinetic energy. The texture and OM content of soil crusts and eroded sediment were analysed. OM was enriched by more than 10% in one test only, but reduced significantly during two soil and rainfall combinations. Analysis of crust and sediment texture showed that the interaction between crust development and rainfall erosivity was responsible for the varying OM enrichment. The results also confirmed that, for practical erosion applications, the maintenance of the mass of OM has to be considered. Accordingly, a key requirement for the correct assessment of OM erosion is the proper assessment of the interaction between surface and rainfall over time in each erosion system. [Copyright &y& Elsevier]

We briefly review and expand upon classic conceptual models describing the succession of benthic communities along a gradient of organic matter (OM) enrichment developed for freshwater (the Saprobity System), coastal marine (the Pearson-Rosenberg [P-R] model) and lagoon (the Guélorget-Perthuisot [G-P] model) ecosystems. Differences and similarities between various approaches and models are highlighted and the P-R and G-P models are unified under a single conceptual framework of habitat saprobity in coastal lagoons. We refer to saprobity as the state of an aquatic ecosystem resulting from the input and decomposition of OM and the removal of its catabolites. In addition to other factors, such as salinity, saprobity is viewed as a selection factor for species diversity. The higher the saprobity is, the more impaired the system is, with progressively poorer benthic communities characterized by species that are increasingly tolerant of reducing conditions and toxicity. In coastal lagoons, these processes are strongly driven by hydrodynamics, which govern the land-sea gradient. Based on our review and analysis, we find that saprobity can be a useful descriptor of ecosystem state as determined by OM metabolism, suitable for characterizing the natural conditions of coastal lagoons and assessing their quality. [ABSTRACT FROM AUTHOR]

Abstract: To assess the impact of an artificial dyke in Chonsu Bay (CBD) on the organic carbon (Corg) cycle, we measured excess 210Pb activities, Corg and nitrogen content in sediment cores. The Corg oxidation rates (Cox) on the surface sediment and benthic nutrient fluxes were also quantified with an in situ benthic chamber. The higher excess 210Pb inventory, Corg and nitrogen in cores near the CBD indicated lateral transport and local, massive deposition of particulate matter due to tidal circulation altered by artificial dyke construction. The Cox in sediment near the CBD was about twice as high as that out of the bay, suggesting the importance of benthic remineralization of organic matter. The benthic fluxes of dissolved inorganic nitrogen and phosphate were four to six times higher than those outside the bay, corresponding to 141% and 131% respectively, of the requirements for primary production. [Copyright &y& Elsevier]

Abstract: Foraminiferal thanatacoenoses were examined around five islands in the Caribbean Sea, which forms a single biogeographic province with respect to nearshore (<3m water depth) foraminifera, which live primarily on marine vegetation. On death, they become incorporated into the sediment. The assemblage at a site reflects the live assemblage and post mortem affects such as dissolution and transport during storms. Reefal species (Amphistegina gibbosa, Asterigerina carinata) are transported towards shore during storms. Foraminiferal thanatacoenoses were examined in 65 nearshore sediment samples from around five eastern Caribbean islands: St. John (US Virgin Islands), St. Kitts, Nevis, Bequia and Tobago. Cluster and principal components analyses distinguished the following environments (indicator species in parentheses): [1.] Sediment associated with mangroves (Ammonia sobrina), [2.] Bays subject to organic matter enrichment (Quinqueloculina poeyana, Triloculina rotunda, T. trigonula), [3.] Areas subject to moderate sediment flux during storms (Quinqueloculina auberiana, Nodobaculariella mexicana, Peneroplis proteus, Archaias angulatus), [4.] Locations subject to high sediment flux during storms (Amphistegina gibbosa), [5.] Sites little stressed by organic matter enrichment or storms (Discorbis rosea). The majority of samples were from sites in the last category. The data from this study could form the nucleus of a catalogue of Caribbean beaches and their environmental influences. [Copyright &y& Elsevier]

The changes in the biofilm community due to organic matter enrichment, eutrophication and metal contamination derived from fish farming were studied. The biofilm biomass, polysaccharide content, trophic niche and element accumulation were quantified along an environmental gradient of fish farm wastes in two seasons. Biofilm structure and trophic diversity was influenced by seasonality as well as by the fish farm waste load. Fish farming enhanced the accumulation of organic carbon, nutrients, selenium and metals by the biofilm community. The accumulation pattern of these elements was similar regardless of the structure and trophic niche of the community. This suggests that the biofilm communities can be considered a reliable tool for assessing dissolved aquaculture wastes. Due to the ubiquity of biofilms and its wide range of consumers, its role as a sink of dissolved wastes may have important implications for the transfer of aquaculture wastes to higher trophic levels in coastal systems. [Copyright &y& Elsevier]

Abstract: A manipulative caging experiment was carried out to evaluate the role of wild fish and motile epibenthic invertebrates on the benthic system influenced by an open water fish farm. Chemical and biological parameters of the sediment were measured as indicators of the ecological benthic status. The combination of wild fish and currents notably lowered aquaculture waste sedimentation below the fish farm. The limited waste sedimentation rate could have limited the scavenger and predation activity of wild fish on the benthos, whose role may be taken over by motile epibenthic invertebrates. The interaction of these motile epibenthic invertebrates with the sediment differed from that observed with fish. The motile epibenthic invertebrates led to more reduced conditions with lower redox values, significantly decreased the number of species of macrofaunal benthic assemblages and significantly modified macrofaunal benthic assemblages. Therefore, epibenthic invertebrates do not seem to have an ameliorative effect on the benthic status produced by fish farming. Since the effects of epibenthic species on the benthic system can greatly vary according to their identity, further experiments should be performed to better understand the drivers that influence the epibenthic species identity that modulate the benthic system affected by fish farming. [ABSTRACT FROM AUTHOR]

Frequent hyperthermal events during the Eocene (55-47 Ma), primarily characterised by carbon isotope excursions (CIEs), have been identified from marine records worldwide. However, only a few excursions have been recognised and described in continental deposits, thereby limiting the understanding of the effect of global warming on terrestrial systems. Thick, dark, organic-rich mudstone containing complete astronomical age information was deposited during the Palaeogene in the Fushun Basin. Based on U–Pb zircon dating and Milankovitch cycle analysis, the astronomical time scale (ATS) of the Fushun Basin was established. Based on the high-resolution chronostratigraphic framework, combined with the negative migration characteristics of organic carbon isotopes (δ13C TOC), three hyperthermal events were identified: Eocene Thermal Maximum 2 (ETM2), Eocene Thermal Maximum (ETM3) and long-term Early Eocene Climatic Optimum (EECO). In particular, several periods of short-term hyperthermal events were identified in the EECO period: L, M, N, O, P, Q, R, S, T, U, V, W, C22nH3, C22nH4, C22nH5, C21rH1, C21rH2, C21rH3, C21rH4, C21rH5, C21nH1 and C21nH2. The records of sea and land hyperthermal events show that the records corresponding to land basins are timelier and more sensitive. • Established astronomical chronology scale of Eocene in Fushun basin. • The boundary ages of Guchengzi Formation and Lizigou Formation of Eocene in Fushun Basin are determined to be 54.51 Ma. • ETM2, ETM3 and EECO hyperthermal events were found in Eocene strata of Fushun Basin. [ABSTRACT FROM AUTHOR]

Organic-rich terrestrial shales, the most promising shale oil production layer, are widely distributed in major basins in China, and they are usually interbedded salt rocks. Understanding the role of salt rocks in the organic matter (OM) enrichment in shale sediments has important enlightenment for shale oil exploration. The shale of the third member of the Eocene Shahejie Formation (Es 3 shales) in the Dongpu depression of the Bohai Bay Basin is dominated by clay minerals, with a non-negligible proportion of gypsum, anhydrite, and halite. They contain abundant OM with a mean total organic carbon content of 1.26 wt %. The development of salt rocks revealed the arid and transiently humid climate during the Es 3 period and an evaporating environment with a shallow lake level at the Dongpu Ancient Lake Basin. OM enrichment was synthetically affected by the palaeoenvironment during the Es 3 period. The paleolake with a paleosalinity as high as 23.43‰ was nutritious and promoted the prosperity of salt loving organisms causing high paleoproductivity. The Es 3 shales were deposited under anoxic and dysoxic conditions in a deep lake, which provided good conditions for OM preservation. In addition, salt rocks itself are good caprocks to prevent the loss of shale oil. Under the dual guarantee of high productivity and good preservation conditions, OM is much enriched in the Es 3 shales. OM enrichment was synthetically affected by the palaeoenvironment during the Es 3 period. The horizontal difference of paleoclimate controlled the discrepancy of salinastones distribution, OM enrichment, paleosalinity, andpaleoproductivity in different saline surroundings of Dongpu Depression. The composite patterns of palaeoenvironmental variation affected the vertical anisotropic enrichment of OM. Seven stages were divided for the Es 3 period to reflect the effects of vertical anisotropy on OM enrichment. Stages I, V, and, VII deposited thick salt under an arid climate and provided a good seal-capping and preservation condition for the OM enriched in stages II, III, IV, and VI. The shale reservoirs deposited in stages III and IV were favorable for shale oil exploration. • Mid-Eocene Dongpu depression suffered arid climate with widespread salt sediments. • Dongpu Lake were nutritive during middle Eocene Es 3 formation deposited period. • Paleoenvironmental variation patterns controlled the anisotropy of OM enrichment. [ABSTRACT FROM AUTHOR]

Oil shales are developed in the Shale Member of the Middle Jurassic Shimengou Formation in the Qaidam Basin, China. The oil shales can be classified into three quality groups (low-, medium-, and high-quality oil shales) through a comprehensive analysis protocol that includes Rock-Eval pyrolysis, total organic carbon (TOC) content, proximate analysis, gas chromatography-mass spectrometry (GC-MS), X-ray diffraction (XRD), major and trace element analyses, and maceral analysis. The low-quality oil shales mainly contain type II1 kerogen, the medium-quality oil shales mainly contain type I-II1 kerogen, and the high-quality oil shales mainly contain type I kerogen. All are immature to early thermally mature. The oil yield of the oil shales is directly related to their quality and are positively correlated with TOC content and calorific value. All studied samples were deposited under anaerobic conditions but in different paleoenvironments. The low-quality oil shales were mainly deposited in fresh-water environments, whereas the high-quality oil shales were usually developed in highly saline and reducing environments. Salinity stratification and evidence of algal blooms that are conducive to organic matter enrichment were identified in both medium- and high-quality oil shales, the latter having the highest paleoproductivity and the best preservation conditions. In summary, shale quality is controlled by a combination of factors, including algal abundance, preservation conditions, the existence of algal blooms and salinity stratification, and paleoproductivity. This study reveals how these different factors affect the quality of oil shales, which might provide an in-depth explanation for the formation process of lacustrine oil shales. [ABSTRACT FROM AUTHOR]

The Paleoproterozoic dark shale of the Cuizhuang Formation is the potential petroleum source rock in the Yuncheng Basin. Mineralogy, organic and inorganic geochemical analysis were applied in this study to evaluate the sedimentary paleoenvironments and its factors that control the enrichment of organic matter and to reconstruct the organic matter accumulation model of the Cuizhuang Formation dark shale. Quartz and clay minerals are the most abundant minerals in the Cuizhuang Formation dark shale. The TOC content of the dark shale is relatively fair, ranging from 0.13% to 1.09% and averaging of 0.51%, with the organic matter having a high thermal maturity (mean of 2.24 Ro%) and type I kerogen. The Cuizhuang Formation shale was deposited in a passive continental margin setting, and the climate was under moderate warm and humid conditions with low salinity of seawater as evidenced by the proxies of chemical alteration index (CIA) and Sr/Ba. The paleoproductivity proxies Ba bio , Ba%, Ba/Al, P 2 O 5 and P/Ti indicate low productivity with negative and no correlations with TOC content and thus didn't control the organic matter enrichment. The low productivity may have significantly played a role in limiting the organic matter formation resulting in relatively low TOC content. The anoxic redox environment of the dark shale is indicated by the proxies of V/(V + Ni) and V/Sc, with strong positive correlations of V and V/Al with TOC. The anoxic redox environment in deeper waters and a higher sedimentation rate than the grey and red shale played the main role of enriching the organic matter of the dark shale. Therefore, the Cuizhuang Formation dark shale in the Yuncheng Basin is regarded as a potential source rock, holding promise for petroleum exploration. • Paleoenvironment and its relationship with organic matter enrichment was revealed. • Low productivity resulted in low TOC content of the Cuizhuang Formation shale. • Reducing environment and higher sedimentation rate contributed to the organic matter enrichment of the dark shale. • The accumulation model of the dark shale organic matter in the Cuizhuang Formation was established.. [ABSTRACT FROM AUTHOR]

The lacustrine black shales of the Chang 7 member are the main source rocks and the most important unconventional (shale oil) petroleum resources in the Ordos Basin, North China. A series of continuous core samples was analysed for main, trace, and rare earth elements. The development of thin or laminar tuffs and tuffaceous mudstones and the enrichment of Fe, Mn, and other elements demonstrate that the Chang 7 member was influenced by event deposition, such as volcanic and hydrothermal activity. The ancient lake had brackish water and a relatively high sedimentation rate during the deposition of the Chang 7 member. The palaeoclimate in the early stage was warmer and wetter than that in the middle-late stage of the Chang 7 period. The geochemical proxies for palaeoproductivity and palaeoredox indicate that the ancient lake had a relatively high primary productivity with an anoxic to euxinic sulphide bottom water in the Chang 73 stage, which decreased to dyoxic-oxic water during the Chang 71+2 periods. A parameter dataset comprising 11 elemental proxies related to the reconstruction or evaluation of the depositional environment and palaeoproductivity was analysed using principal component analysis (PCA). The first principal component (PC1) accounted for 59.88% of the total variance in the original dataset and mainly represented the characteristics of palaeoproductivity and redox conditions; thus, it can be interpreted as an indicator of these factors. Based on the excellent positive linear correlation between the total organic matter content of the Chang 7 samples and the PC1 scores, the enrichment of organic matter in the Chang 7 member was mainly controlled by palaeoproductivity and the preservation environment. PCA is an effective method for dimensionality reduction and visualisation of multi-element geochemical data, which allows for a more comprehensive and in-depth understanding of geological samples. This work provides a practical application of chemometrics in elemental geochemistry. This can serve as a model for other studies. • Insight into organic matter enrichment by combining PCA with element geochemistry. • The primary paleoproductivity of the Chang 7 member in the Ordos Basin was evaluated. • The paleosedimentary environment of the Chang 7 member was reconstructed. • The organic matter enrichment of Chang 7 member was controlled by paleoproductivity and preservation. [ABSTRACT FROM AUTHOR]

Lacustrine rift basins in Eastern China possess large amounts of petroleum, especially the shale gas and tight sand gas in deep formations, where "sweet spots" are closely related to organic-rich shale intervals. However, the OM enrichment of deep formation shale in lacustrine rift basins and the main controlling factors have not been well-researched in previous studies. The organic matter (OM) enrichment is mainly controlled by the OM input, preservation, and/or dilution. The shales deposited in deep formations of Songliao Basin, including the Jurassic Huoshiling (J 3 h), Cretaceous Shahezi (K 1 sh), and Yingcheng (K 1 yc) formations, are evaluated as fair to excellent source rocks. Taking the shales as an example, the characters and impact of input, preservation, and dilution on OM enrichment in shales are discussed by utilizing the parameters of element concentrations and biomarkers. Results show that the OM sources are mixed sources of aquatic microorganisms and higher plant materials, and the higher plant materials are dominant. The bio-productivity were moderate to high. The paleoclimate was mainly the cold and semi-humid to semi-arid. The lake salinity was fresh-to brackish-water. The redox conditions were sub-reducing to sub-oxidizing. The dilution degree in Yingcheng was the strongest, followed by the Shahezi and Huoshiling. Consequently, the OM enrichment in the J 3 h shale was called moderate bio-productivity and preservation model; the OM enrichment in the K 1 sh shale was called high bio-productivity and preservation model; the OM enrichment in the K 1 yc shale was named high dilution model. This study not only improves the model of OM enrichment but also provide some information for the research of "Deep time" in the Cretaceous of Songliao Basin, guiding the prediction of organic-rich shale distribution in lacustrine rift basin. • Fair to excellent hydrocarbon generation potential. • Organic matter origins are mainly a mixture of aquatic microorganisms and terrestrial higher plants. • Arid and cold paleoclimate and fresh- and brackish-water. • Reducing to sub-reducing, sub-reducing to oxidizing, and sub-reducing to sub-oxidizing conditions. • Moderate bio-productivity and preservation model, high bio-productivity and preservation model, high dilution model. [ABSTRACT FROM AUTHOR]

The Fushun Basin is a typical continental basin filled with organic-rich fine-grained sedimentary rocks, such as coal, oil shale and greyish green mudstone. Currently, research on this basin predominantly focuses on the enrichment mechanisms of organic matter in coal and oil shale and the controlling factors of coal seam transformation to oil shale. However, during the transformation stage, the deposition of oil shale ceased and was converted to interbeds of grey green mudstone and thin oil shale layers. The control mechanism of this type of sedimentary succession is still not clear. In this study, the thick oil shale in the upper part of the Jijuntun Formation (Unit I) and the high-frequency interbedded mudstone and thin oil shale in the Xiloutian Formation (Units II and III) were analysed as key strata. Organic and inorganic geochemical data were analysed to reconstruct the transformation of the various types and sources of organic matter and controlling factors including the palaeoclimate, palaeoweathering, bioproductivity, terrigenous clastic input, palaeosalinity, and redox conditions. Among these, Unit I was affected by humid climate conditions predominantly. The water depth and volume were large, and the input of terrigenous debris was low. Freshwater algae blooms and anoxic conditions led to a supply of organic matter and that was well preserved. This further resulted in a high abundance of organic matter in the sedimentary rocks. Unit II was affected by semihumid-semiarid and arid climate conditions. The lake became shallower while terrigenous clastic input and lake palaeosalinity increased; these changes represented the transition stage from freshwater to brackish water. The lake still exhibited suboxic/anoxic conditions, but the biological living space decreased, resulting in a limited organic matter supply and a low abundance of organic matter in the sediment. Unit III was affected by semihumid-semiarid climate conditions, and the palaeosalinity continued to increase. The lake had brackish water, with a high bioproductivity, a decreased water volume and a limited supply of organic matter. However, brackish water stratification occurred in the lake, which created a strongly anoxic environment and good preservation conditions, resulting in a secondary high abundance of organic matter. A comprehensive analysis indicates that the environmental change caused by the palaeoclimate was the main factor driving the oil shale deposition to cease and the onset to deposit grey green mudstone and thin oil shale in the Fushun Basin, Northeast Asia. • Different from the previous research, thin layer oil shale layers are also developed in the Xiloutian Formation. • The palaeoclimate, palaeosalinity and bioproductivity showed cycle evolution in the Xiloutian Formation. • High organism supply promoted the formation of thick high-quality oil shale in Jijuntun Formation in anoxic environment. • The excellent preservation condition is the key factor for the formation of oil shale in the Xiloutian Formation. [ABSTRACT FROM AUTHOR]

Limestone-marlstone (LM-MR) rhythms widely develop in the middle Permian Maokou Formation of Sichuan basin, and they are regarded as potential source rocks and important shale gas targets due to their high organic matter contents. In this study, LM-MR rhythms in the lower part of the Maokou Formation in the Changjianggou section of the Sichuan basin are selected for research because of their moderate thermal maturity of organic matter. A series of studies are implemented to investigate the organic geochemical characteristics, formation processes, organic matter enrichment mechanism, and hydrocarbon potentials of these LM-MR rhythms, from perspectives of sedimentology, organic petrology, and geochemistry. Organic matter in marlstones is suggested to be mainly contributed by cyanobacteria according to organic petrographic results, low regular steranes/17α-hopanes, and high mid-chain branched monomethyl alkanes (MMAs). In contrast, organic matter in limestones is suggested to mainly result from benthic algae. Marlstone samples have more negative carbon and oxygen isotopes and higher Fe/Mn ratios than the limestone samples, suggesting sedimentary environments with shallower water depth and stronger restrictions during marlstone deposition. Moreover, marlstone samples have lower ratios of gammacerane/C 30 αβ hopane than limestone samples, suggesting lower water salinity during marlstone deposition. Furthermore, marlstone samples have higher TOC contents than limestone samples, and this is attributed to the less carbonate dilution, the suboxic-anoxic environment, and the increased productivity during marlstone deposition, all of which are initially controlled by the high-frequency relative sea-level change. The hydrocarbon potential analysis suggests that LM-MR rhythms in the study area are with high TOC contents, Type II organic matter, and moderate thermal maturity. • Marlstone and limestone are mainly contributed by cyanobacteria and benthic algae respectively. • Marlstones are deposited in more restricted environments with shallower water than limestones. • High paleoproductivity and suboxic-anoxic condition result in high TOC of marlstones. • Maokou Formation LM-MR rhythms are potential good source rocks. [ABSTRACT FROM AUTHOR]

The Songliao Basin (SLB) is a large terrestrial petroliferous basin located in northeastern China. The Nenjiang Formation represents excellent hydrocarbon source rocks for the Daqing oil field. Previous studies have indicated that the oil shale intervals from the first (K2n1) and second (K2n2) members of the Nenjiang Formation were formed in different depositional settings. In this study, we provide a new high-resolution (1 m interval) record from SK-1s core and compile three sets of published datasets from two drilling holes (Zk3389 and LY-1) and a composite outcrop section. According to the total organic carbon (TOC) chemostratigraphy, we have divided three variation cycles spanning from K2n1 to K2n2 and detected three potential oil shale intervals in the Nenjiang Formation. Combined with the productivity, salinity, and oxygenation proxies, we discuss the paleolimnological environmental changes during deposition of the Nenjiang Formation. Our new and compiled records support the model that excellent preservation conditions were associated with the formation of organic-rich sediments in the K2n1, while the productivity was the major controlling factor for organic matter enrichment in the K2n2. [ABSTRACT FROM AUTHOR]

The formation and preservation conditions of the organic matter (OM) in the Upper Devonian Shetianqiao Formation were investigated to assess the mechanism of the OM enrichment in the shale in the Shaoyang sag. The total organic carbon (TOC) contents of the shale range from 0.2% to 4.4%. The shale can be divided into three intervals. The terrestrial input during Interval 2, as indicated by the Al 2 O 3 and Ti proxies, was relatively small. The chemical alteration index (CIA) shows that the Shetianqiao Formation mainly formed in a warm and humid climate, however, climate cooling occurred in Interval 2. Intervals 1 and 3 were mainly deposited in a restricted environment, whereas Interval 2 experienced upwelling. The climate cooling may have been the driver for the upwelling. The U EF , Mo EF , and Mo-U covariation diagrams indicate that Interval 2 was mainly deposited under reducing conditions, whereas Intervals 1 and 3 were chiefly formed in an oxidizing environment. The Cu/Al ratios and excess Si (Si xs) suggest that Interval 2 was formed in significantly higher marine productivity than Intervals 1 and 3. The plot of Co (ppm) × Mn (%) versus Cd/Mo, the logarithmic relationship between Co (ppm) × Mn (%) and TOC, and the good correlations between TOC and the productivity proxies suggest that productivity was the primary factor for the OM enrichment. We constructed a depositional model that emphasizes the control of productivity driven by upwelling on the OM enrichment. • The middle interval (Interval 2) of Upper Devonian Shetianqiao Formation develops relatively high organic shale (TOC >1%). • The high organic shale formed under reducing conditions, a higher marine productivity, and minimal terrestrial input. • The Interval 2 experienced upwelling, whereas the Intervals 1 and 3 were generally of restricted basin environment. • The improvement of productivity driven by the upwelling is the primary controlling factor for organic matter enrichment. • A depositional model has been established to emphasize the control of productivity on the organic matter enrichment. [ABSTRACT FROM AUTHOR]

Organic-rich shale intervals in the Miocene Zeit Formation were collected from seven wells in the Red Sea basin for compilation of organic geochemical and petrological methods. The current study evaluated the paleo-oxygenation conditions regarding the preservation and the organic-rich sedimentation. The type of organic facies and their relation to hydrocarbon generation potential were also studied. Most of the Zeit shale samples are organically rich and include favorable source rocks, as indicated by the high TOC content of up to 1 wt%. The shale samples also have hydrogen index (HI) values between 58 and 595 mg HC/g TOC, resulting in two dominant organic facies of Types II-III, and III kerogen, with little Type II, and thereby contributing to generate both oil and gas. Biomarker fingerprints, including of n -alkanes, isoprenoids, terpanes, and steranes reveal that the Zeit shales contain mixed organic matter, with a high contribution of marine plankton/algal and microorganisms. The presence of the phytoplankton algae i.e. Chlorococcales and Tasmanites in the Zeit shales further suggests reducing conditions during deposition, thus, enhanced growth of algae and marine microorganisms owing to the presence of nutrients and contribute to good preservation of organic matter. According to maturity indicators of geochemical T max (≥430 °C) and vitrinite reflectance (VRo) values (0.52–0.98%), the analyzed Zeit shales are in a mature stage of oil window equivalent to early-mature and peak-mature. This implies that the Zeit shales were reached a sufficient maturity level for commercial oil generation. • Organic matter content, type, maturity and oil-generation potential have been investigated. • Depositional environment conditions of studied shale sediments has been interpreted. • Maturity data (vitrinite, Tmax and biomarkers) indicated prominent early-mature to late oil window stage. [ABSTRACT FROM AUTHOR]

Based on the sedimentological and geochemical analysis of total organic carbon (TOC) and major and trace elements in the marine Upper Ordovician-Lower Silurian Wufeng-Longmaxi Formations in Yichang, Central Yangtze area, paleoredox conditions (indicated by U/Th, V/Cr, Ni/Co, TOC-TS-Fe diagram, and Mo–U covariations), paleoproductivity (indicated by Ba bio , Ba/Al, P/Ti, Ni/Al, Cu/Al, and Zn/Al), terrestrial detrital influx (indicated by Ti and Al), paleoclimate (indicated by chemical index of alteration and Rb/Sr), and upwelling (indicated by Co × Mn) are revealed within the framework of sea-level changes. The influences of these factors on organic matter enrichment are also discussed. The results identify four third-order sequence boundaries in the Wufeng-Longmaxi Formations; each sequence can be divided into one transgressive systems tract (TST) and one regressive systems tract (RST) according to sea-level changes. The high-TOC interval mainly developed in TST1 (average 3.44%) and TST2 (average 3.68%). The analysis of geochemical indicators shows that during the TST1 depositional stage, the climate was dry and cold, the bottom water was in a stable anoxic condition accompanied by rising sea level, and the seawater had moderate-high paleoproductivity. In the RST1 stage, extensive sea-level fall occurred, and the water was anoxic, with decreased productivity and weakened organic matter accumulation. In the TST2 stage, the sea level rise rapidly, extensive anoxicity and high productivity of the water produced the most ideal environment for organic matter enrichment and the highest TOC. In the RST2 stage, sea level slowly fell, the water column gradually became a stable oxidized environment, productivity was low, the terrestrial detrital influx increased and tended to stabilize, and the climate gradually changed to warm and humid conditions, forming relatively organic-poor shale. The upwelling mainly developed during the period of TST1 to TST2, and ceased in the RST2. The correlation analysis between TOC and the above indicators and the Co × Mn versus Cd/Mo diagram show that TOC is chiefly controlled by paleoredox, paleoproductivity, climatic conditions, and terrestrial detrital influx, indicating that preservation conditions are the crucial factor. Sea-level change played a key role in preservation conditions. In the transgression stages, sea-level rise led to the enhancement of reducing water, which controlled the organic matter enrichment in shale. • Sequence framework has been established by the identification of boundaries. • The TOC of transgressive systems tract (TST) is relatively the highest. • The enrichment of organic matter is mainly controlled by the paleo-redox condition. • Sea-level rise is the main driver for the anoxic condition. [ABSTRACT FROM AUTHOR]

In addition to the organic-rich shale in the Chang 7 Member (Ch7 shale) of the Ordos Basin, the shale hosted in the Chang 9 Member (Ch9 shale) is another source rock and potential unconventional target. However, there is a general lack of consensus on the features and potential of the Ch9 shale. In order to determine the potential of the Ch9 shale, this study analyzes its paleoenvironment and sedimentary setting based on the integrated analysis of geochemistry and sedimentary facies. A comparison of geochemical features between the Ch9 shale and the organic-rich Ch7 shale is made to evaluate the factors controlling organic matter (OM) enrichment of the Ch9 shale. The results show that the Ch9 shale has good hydrocarbon potential, and terrestrial OM is important component of the OM in the Ch9 shale. The Ch9 shale was deposited in climatic transition period from cold and dry to warm and humid, when the water body was suboxic-anoxic and freshwater. The relatively cold and dry climate and suboxic-anoxic water condition in the Ch9 period could not provide the same excellent conditions for OM enrichment as that in the Ch7 period. The Ch9 shale is composed of sediments mixed with felsic rocks that originated from continental island arcs and active continental margins. The active tectonic setting resulted in event deposition (e.g. turbidity flows and hydrothermal fluid activity) during the deposition of Ch9 shale. The input of terrestrial OM carried by turbidity flows also promoted OM enrichment, however, the very high depositional rates caused by turbidity flows diluted the OM, which probably offset the effect of hydrothermal on OM enrichment. Our results are helpful to revealing the source potential of the Ch9 shale, providing a theoretical basis for the shale oil and gas exploration in the Ordos Basin. • The organic matter of the Ch9 shale was mainly sourced by terrigenous material. • The Ch9 shale was deposited in suboxic-anoxic and fresh water conditions. • Turbidites transported terrigenous organic matter, but also diluted it. • The enrichment conditions of the Ch9 shale is not as good as that of the Ch7 shale. [ABSTRACT FROM AUTHOR]

With the discovery of the Bozhong 19–6 large gas field in the Bohai Bay Basin, the study of lacustrine source rocks in the southwestern Bozhong Sag has garnered new interest. In this paper, 107 source rock samples of the Paleogene Shahejie Formation (Es) from the southwestern Bozhong Sag were analyzed with organic and inorganic methods and compared with other sags in the Bohai Bay Basin to reveal the depositional environment and controlling factors of organic matter enrichment during the deposition of the Es. The formation of source rocks (average total organic content = 2.76%) was subject to a combination of high organic productivity and enhanced organic preservation. Also, this was reflected by the existence of nutrient elements of P and Ba as well as other high productivity-related elements such as Cu, Zn, and Ni. The moderate Mo enrichment factor, Pr/Ph and low to moderate (C/P) org ratios were an essential part of this organic preservation. Moreover, the evidence we observed for the existence of hydrothermal activities consisted of high contents of quartz and pyrite, large positive Eu anomalies, and enrichment of elements related to hydrothermal fluids. Hydrothermal influence may lead to similarities and fluctuations in water salinity, organic productivity and preservation in the third (Es 3) and first (Es 1) members of the Es. Hydrothermal fluids may play an essential role in promoting the development of high organic productivity, stable reducing environment, and brackish water (as shown by the range of B/Ga and TS/TOC) in the lakes during the source rock deposition. This paper may provide implications for gas accumulation mechanisms and a complete set of organic and inorganic experimental data for source rock analysis in other lacustrine rift basins. • The source rocks from the Shahejie Formation (Es) were formed in brackish lakes. • The organic productivity is the main controlling factor of the source rock formation mechanisms. • The existence of hydrothermal fluids may affect environmental changes. [ABSTRACT FROM AUTHOR]

• Mudstones in small rift basins may have good potentials of hydrocarbon accumulation. • Anoxic, brackish-saline environments are favorable for deposition of effective source rocks. • Moderate sedimentation rates (60–70 m/Myr) are important for organic matter enrichment. • A "supply-preservation-dilution" model for the formation of source rock is proposed. Petrography and compositions of organic matters of Cretaceous source rocks from the Tiancao Sag, the Yin'e Basin, Northern China, have been presented in order to determine the Cretaceous sedimentary environment and processes that enriched organic matters. The mudstones of the Bayangobi Formation have medium–high total organic carbon (TOC) (0.27–2.59%) and S 1 + S 2 (0.30–12.23 mg HC/g rock) values. Vertically, three sedimentary units (2460–2600 m; 2640–2860 m; and 3020–3050 m) present good hydrocarbon potentials. The macerals, the C 27 -C 29 regular sterane distribution, and the isotopic and element geochemistry of the kerogen prove that the organic matter has a mixed origin of plankton/algae and terrestrial plants. The vitrinite reflectance, T max , and biomarker parameters collectively suggest that the source rocks have reached the mature stage. The mudstones were deposited in a reducing brackish-saline environment, and the salinity-sensitive proxies indicate a gradual evolution of the sedimentary conditions from low to high salinity. The positive correlation between the hydrogen index value and TOC content and the negative correlation between Pr/Ph ratio and TOC content suggest that the primary productivity and preservation in reducing water collectively contributed to organic matter enrichment of the Bayangobi Formation. The relationship between sedimentation rate and TOC content suggests that a sedimentation rate of 60–70 m/Myr is conducive to the formation of effective source rocks. Therefore, the organic matter enrichment of Bayangobi Formation was controlled by moderate-high paleoproductivity, reducing conditions, and an appropriate sedimentation rate. This paper proposes a "supply-preservation-dilution" model for the source rocks in the Tiaocao Sag, Yin'e Basin. [ABSTRACT FROM AUTHOR]

Organic-rich shale, the third member of the PaleogeneShahejie Formation (Es 3), is considered as an excellent lacustrine source rock in the Bohai Bay Basin. However, studies on how paleosedimentary environments affect organic matter enrichment are still lacking. In this study, cores of the Es 3 shale in the Dongpu Depression (DD) nearly 200 m in length were collected at well Pu 115 to investigate organic matter enrichment mechanism. Results suggest that the Es 3 shale was deposited under reductive conditions based on the redox index (V/(V + Ni)) and the large amount of pyrite. The Mg/Sr and Fe/Mn ratios indicate a generally arid climate with a frequently changing paleowater depth. The paleosalinity analyses indicate the Es 3 shale developed under fresh-brackish conditions. The Ba content ranges from 75 to 435 ppm (avg. 284 ppm), showing a moderate paleoproductivity. Correlation analyses among the total organic carbon (TOC) and major and trace element ratios show that the TOC rises with the increasing water reduction degree. With increasing water paleosalinity, the TOC increases initially and then decreases, reaching a maximum TOC at a paleosalinity of 11‰. In addition, the TOC increases initially and then decreases with increasing detrital input, indicating that a moderate detrital input would be beneficial for organic matter enrichment. The redox conditions, paleosalinity and quantity of detrital input are the key factors controlling the organic matter enrichment. Further analyses show that the redox conditions were controlled by the paleoclimate, and the paleosalinity and terrestrial detrital input quantity were affected by the paleowater depth. The root factors controlling the organic matter enrichment are paleoclimate and paleowater depth in the saline lacustrine rift basin. • Organic matter enrichment mechanism of saline lacustrine shale was analyzed by combing paleo-salinity, redox condition, terrestrial input, and paleo-productivity in response to paleo-sedimentary environment. • The Es 3 shale was developed in a fresh-brackish and reducing water body with changeable arid climate. • Reduction condition, paleosalinity, and terrestrial detrital input jointly controlled organic matter enrichment. [ABSTRACT FROM AUTHOR]

The organic-rich shales deposited in marine-continental transitional environments are well developed in China. Previous studies mainly focused on the petrology and geochemical characteristics of the transitional shale. However, the factor controlling organic matter (OM) enrichment in the shale has not been studied adequately, limiting the optimal reservoir selection in shale gas exploration. Based on laboratory analyses and field investigations, this paper documents the geochemical features of the transitional shales in Upper Paleozoic (the Benxi, Taiyuan and Shanxi Formations) of the northeastern Ordos Basin, China. The sedimentary environment evolution and the relevant influence on OM enrichment are discussed to reveal the factor controlling the interlayer difference of the OM enrichment in the shale. The results show that the shale in the Taiyuan Formation hosts the highest OM content in the Upper Paleozoic. The sedimentary setting of the study area transited from barrier-flats to fluvial deltas, accompanied by gradually arid climates, decreasing degree of reduction and salinity of waters, and increasing clastic influx. During the middle stage of the marine-continental transition (the depositional stage of the Taiyuan Formation), the warm and humid climate was beneficial to the OM production, and the anoxic condition was conducive to the OM preservation. In addition, the increasing clastic influx ensured the OM input, and the moderate depositional rate favored the OM preservation. All the factors above commonly established an excellent environment for the OM enrichment. Our results reveal the OM enrichment mechanism in transitional shales, which is helpful to the optimal reservoir selection in the shale gas exploration in the Ordos Basin as well as the similar basins. • The organic matter content shows interlayer difference. • The changes of paleoenvironment and clastic influx of transitional shales are discussed. • Paleoenvironments and clastic influxes jointly influence organic matter enrichment. • The sedimentary environment in the middle of the transition stage is optimal for organic matter enrichment. [ABSTRACT FROM AUTHOR]

Turbidite-associated black shale of the Semanggol Formation is extensively distributed in the northwestern part of the Western Belt, Peninsular Malaysia. The black shale occurs as a dark grey to black and thick to medium-bedded deposit. It represents the distal part of submarine fan system (outer-fan) overlying interbedded sandstone to shale facies of the mid-fan and conglomeratic pebbly sandstone facies of the inner-fan. Field observations and its widespread occurrence have resulted in the black shale being considered as a potential analog for a source rock in offshore Peninsular Malaysia. The present study includes detailed mineralogical (XRD, SEM, and EDX analysis), inorganic geochemical (major oxides, trace elements TEs, and rare earth elements REEs), and Rock-Eval pyrolysis analyses of the black shale samples, collected from the Gunung Semanggol, Bukit Merah, and Nami areas in northwestern Peninsular Malaysia. The primary focus of this study is to investigate the provenance, paleoredox conditions, paleoclimate, sedimentary rate, paleoproductivity, and upwelling system that would be helpful to understanding the role of these parameters in the enrichment of organic matter (OM) in the black shale. The Rock-Eval analysis shows that the black shale of the Semanggol Formation comprises type-III kerogens, which suggests organic input from a terrestrial source. The black shale also contains mature to postmature organic matter. Based on the mineralogical analysis, the mineral composition of the black shale comprises illite and kaolinite, with abundant traces of quartz and feldspar as well as few traces of titanium and zircon. Inorganic geochemical data designate black shale deposition in a passive margin setting that has experienced moderate to strong weathering, semi-arid to hot arid climate, and moderate sedimentation rate. Ratios of Ni/Co, U/Th, and V/(V+Ni) along with slightly negative to positive Ce* anomalies and UEF-MoEF cross-plot unanimously indicate anoxic/dysoxic water conditions that are suitable for organic matter preservation. Geochemical proxies related to modern upwelling settings (i.e., Cd/Mo, Co vs. Mn) show that the deep marine black shale was strongly influenced by persistent upwelling, a first-order controlling factor for organic matter enrichment in the distal part (outer fan of the submarine fan system) of the Semanggol Basin. However, productivity-controlled upwelling and a high sedimentary rate, as well as high-productivity in oxygen-depleted settings without strong anoxic conditions, has played an essential role in the accumulation of organic matter. [ABSTRACT FROM AUTHOR]

The lower 1st Member (Es1L) of the Oligocene Shahejie Formation in the Raoyang Sag, the particularly noteworthy source rock interval in the Jizhong Subbasin, were analyzed with sedimentological and geochemical techniques to describe the distribution of organic-rich source rocks and reveal the lacustrine environment and lake types during source rocks deposition. Results of the Raoyang Sag demonstrate that the organic-rich source rocks are mainly distributed in the north-central region with a maximum thickness of up to 120 m in the Maxi Subsag and gradually decreases to the southern tectonic regions such as Liuxi Subsag. These horizontal and vertical heterogeneities are attributed to depositional environments and lake types during the sedimentary period of the Es1L. Lakes in the Raoyang Sag are generally characterized by saline water during the Es1L deposition. The samples representing the south part of the Raoyang Sag display high pristane/phytane (Pr/Ph), C 19 /C 23 TT, and C 24 Tet/C 26 TT ratios as well as low gammacerane index, 4-methyl sterane index, and sterane/hopane ratio. These findings suggest that hydrological open lake type has unstable water-column stratification, less reducing bottom water, and significant terrigenous supply. However, the samples representing the north-central part of the Raoyang Sag display high gammacerane index, 4-methyl sterane index, and sterane/hopane ratio as well as low Pr/Ph, C 19 /C 23 TT, and C 24 Tet/C 26 TT ratios. A strong correlation exists between δ13C and δ18O, indicating hydrological closed lake-type with excellent water stratification, anoxic bottom water, and enhanced algae productivity. This lake-type is of great significance for continuing research on organic matter enrichment in the Bohai Bay Basin. • We presented the distribution of organic-rich source rocks in the Raoyang Sag. • The north-central and south parts differ obviously in depositional environments. • Lacustrine provenance influenced the lake-types in the Raoyang Sag. • The redox conditions are important for the formation of source rocks. [ABSTRACT FROM AUTHOR]

The Lower Cretaceous Xiagou Formation in Qingxi Sag consists of more than 1000 m of lacustrine sediments, including dolomitic mudstone/argillaceous dolomite and sandstone/mudstone, which is considered to be the most important source rock in the Jiuquan Basin. Power spectra, evolutionary fast Fourier transform (FFT), and correlation coefficient analyses of the gamma-ray (GR) series from four wells, including Liu 8 well, Long 14 well, Q2-36 well and Liu 9 well, through the Xiagou Formation reveal strong astronomical signals of long eccentricity (405 kyr), short eccentricity (100 kyr), obliquity (37 kyr) and precession (22 kyr). These provide an excellent opportunity to establish a floating astronomical time scales (ATS) then to determine variations in the sediment accumulation rate (SAR). Based on the floating ATS of the Xiagou Formation, the Xiagou Formation covers a 10.3 myr period depositional duration, and depositional duration of three members in the Xiagou Formation are 3.5 ± 0.1 myr, 3.1 ± 0.1 myr and 3.65 ± 0.15 myr, respectively. The high-resolution SARs of the Xiagou Formation vary from 8.5 cm/kyr to 19.8 cm/kyr. The different lithologies in the Xiagou Formation exhibit the same variation tendency in SARs, but the mechanisms of astronomical forcing that affect the SARs are different. In addition, the correlation between total organic carbon (TOC) and SARs can be used to investigate the impact of the SAR on organic matter abundance and conclude that relatively high SAR can protect organic matter and prevent oxidation, but rapid SAR can also dilute organic matter abundance of source rock. [ABSTRACT FROM AUTHOR]

Based on the field investigation of oil shales in the southern Ordos Basin, detailed observations, and systematic sample analyses of core samples from a well that penetrated an oil shale, the influence of volcanic and hydrothermal activity on the Chang 8–Chang 7 members of the Yanchang Formation on organic matter (OM) enrichment was geochemically and petrologically analyzed. According to maceral analyses and rock pyrolysis, the kerogen types of the samples in the study area are widely distributed. Those of the oil shale with the highest OM abundance are mostly type II-I, and are immature or in a stage of low-maturity. Six layers of tuff and tuffaceous mudstone were identified by core observation and element characteristics; they are characterized by higher total rare earth element (∑REE) and δCe values and Th contents, and lower (La/Yb) N and δEu values. Mineral assemblages of anhydrite–pyrite–marcasite and relevant diagrams of the elemental geochemistry confirmed the existence of hydrothermal deposits. The high Y n /Ho n and U/Th ratios and total sulfur (TS) contents indicate that the Chang 7 Member experienced four episodes of intense hydrothermal activity. Early in the Chang 73 Member, volcanic ash and hydrothermal fluids brought in a large amount of nutrients, which not only increased primary productivity, but also increased the salinity of the water column, enhanced anoxia in the sedimentary environment of the lake bottom, promoted the preservation of OM, and finally formed the oil shale layer with the richest OM. However, the strong volcanic eruption in the late Chang 73 Member led to changes in the regional climate, causing it to dry and become colder and resulting in a decrease of primary productivity. Earthquakes triggered by volcanism resulted in turbidite deposits, which destroyed the preservation and diluted the enrichment of OM. This study reveals in detail the influence of volcanic and hydrothermal activity on OM enrichment during the evolution of the basin, and thereby deepens our theoretical understanding of OM enrichment. • The influence of volcanic and hydrothermal activities on OM enrichment is revealed. • Volcanic ash and hydrothermal fluids promoted the enrichment of OM. • Strong volcanic eruptions may lead to changes in paleoclimate, which is not conducive to the enrichment of OM. • Sedimentary models of OM in the Chang 8–Chang 7 Members of Yanchang Formation are established. [ABSTRACT FROM AUTHOR]

The removal characteristics of various pollution factors in municipal wastewater by membrane-based physical and chemical treatment, especially the enrichment characteristics of dissolved organic matter, were investigated by high performance liquid chromatography and three-dimensional fluorescence spectroscopy. The results showed that the municipal wastewater had a low COD/TN ratio after the treatment. The micro-flocculation filtration mainly enriched the non-dissolvable organic matter in the raw water and aromatic protein substances with relative molecular mass greater than 30 000. The enrichment degree was up to 60.93%, especially for tyrosine-like and tryptophan-like substances. The dissolved organic matter (DOM) with a molecular weight greater than 30 000 was enriched fully by 0.45 μm and 0.22 μm acetate membranes, but the microfiltration membrane was not selective for the enrichment of organic matter. Thus, NF mainly enriched the fulvic acid and humic acid in urban sewage. The enrichment degree was 52.01% and 53.57%, respectively, and the total enrichment degree of dissolved organic matter was about 42%.

The Datang Formation black rock series deposited in an inter-platform basin are considered to be one of the main source rocks in Southwest China. However, their depositional conditions and organic matter enrichment in such a setting are not well understood. In this study, geochemical characteristics of total organic carbon (TOC), major, trace and rare earth elements (REEs) of thirty black rock series samples from a newly-cut roadside outcrop (Zhenning section) in Southern Guizhou, Southwest China are systematically investigated to examine provenance, paleoredox conditions, paleoclimate, paleoproductivity and sedimentary rate, and further to explore their influence on organic matter enrichment. Results show that TOC contents of the investigated samples range from 0.90% to 2.83%, with an average of 1.45%, with TOC variations being in accord with the stratigraphic cyclicity. These data also indicate that the target black rock series were deposited in a combination of continental island arc and active continental margin tectonic setting that exhibited moderate weathering, oxic/dysoxic oxygen levels, hot and arid to semiarid climate, and a higher sedimentary rate. Multiple paleoredox indicators (e.g., Ni/Co, V/Cr, U/Th and V/(V + Ni) ratios), together with slightly negative Ce anomalies and EFU-EFMo covariation, totally suggest an oxic/dysoxic water environment, which is usually considered unfavorable for organic matter preservation. Average (La/Yb)N ratios (1.41) reflect a higher sedimentary rate, resulting in shortening the exposure time of organic matter in the degradation region of aerobic bacteria under oxic/dysoxic conditions. Of the three factors that could affect organic matter enrichment, including paleoproductivity, paleoredox conditions and sedimentary rate, the relatively high paleoproductivity indicated by the relatively high TOC contents appears to be the dominant factor. In contrast, the other two factors, i.e., paleoredox conditions and the rate of sedimentation play relatively less significant roles. Based on these factors, an enrichment model of organic matter for the black rock series in Southern Guizhou Depression is established. These findings also contribute to constraining the sedimentary environment in such a setting and further deepen our understanding of the potential shale gas resources of the Southern Guizhou Province. [ABSTRACT FROM AUTHOR]

Aquatic ecosystem enrichment can lead to distinct and irreversible changes to undesirable states. Understanding changes in active microbial community function and composition following organic-matter loading in enriched ecosystems can help identify biomarkers of such state changes. In a field experiment, we enriched replicate aquatic ecosystems in the pitchers of the northern pitcher plant, Sarracenia purpurea . Shotgun metaproteomics using a custom metagenomic database identified proteins, molecular pathways, and contributing microbial taxa that differentiated control ecosystems from those that were enriched. The number of microbial taxa contributing to protein expression was comparable between treatments; however, taxonomic evenness was higher in controls. Functionally active bacterial composition differed significantly among treatments and was more divergent in control pitchers than enriched pitchers. Aerobic and facultative anaerobic bacteria contributed most to identified proteins in control and enriched ecosystems, respectively. The molecular pathways and contributing taxa in enriched pitcher ecosystems were similar to those found in larger enriched aquatic ecosystems and are consistent with microbial processes occurring at the base of detrital food webs. Detectable differences between protein profiles of enriched and control ecosystems suggest that a time series of environmental proteomics data may identify protein biomarkers of impending state changes to enriched states., Competing Interests: The authors declare no conflict of interest.