Carbonate banks and slump beds in the Upper Cretaceous (Upper Turonian-Santonian) of Haute Normandie, France

Large scale sedimentary structures present in the Upper Turonian to Santonian chalks of Haute Normandie (northern France) represent the remains of a carbonate bank complex which formerly extended over an area of at least 1500 km². Cliff exposures along the Channel coast from St Valéry-en-Caux to Cauville and along the Seine from Sandouville to Lillebonne show sections of banks up to 50 m high and 1500 m across, their internal structures picked out by hardgrounds, nodular chalks and horizons of burrow flint. Associated with banks are slump sheets up to 20 m thick, slump scars, sedimentary breccias, injection phenomena and faults contemporaneous with sedimentation. Later diagenetic features include extensive dolomitization and silicification. These structures compare closely with the Waulsortian banks of the Palaeozoic, and bryozoan bioherms known from the Upper Cretaceous and Palaeocene of Denmark. Frame-building, sediment trapping and stabilizing organisms are absent, and bank development and stabilization was probably due to a plant covering, either algal or of marine angiosperms. Banks generated much of their own sediment, whilst a pelagic constituent (calcareous nannofossils and Foraminiferida) is also present. The distribution of the bank complex is related to a basement controlled swell area, whilst the life of the complex was limited to a relatively shallow water, regressive episode in the predominantly transgressive Upper Cretaceous history of the region. Les falaises littorales du Pays de Caux comprises entre Antifer et St Valèry-enCaux, et les affleurements de la basse vallée de la Seine permettent d'observer des formations du Turonien supérieur-Sénonien inférieur qui présentent des stratifications irrégulières soulignées par de nombreux hardgrounds, des horizons de craie noduleuse et des cordons de silex. Ces structures sont identifiées à des accumulations de calcilutite et calcarénite sous forme de bancs sous-marins dont la hauteur peut atteindre 50 m et qui couvrent une surface supérieure à 1500 km²; ils apparaissent au-dessus de hardgrounds subhorizontaux qui indiquent un haut-fond régional stable. Des glissements sous-marins sont associés à ces bancs et engendrent des niveaux avec des déformations souples atteignant 20 m d'épaisseur. Des brèches apparaissent localement et contiennent des blocs basculés de hardgrounds fragmentés lors du glissement; on y observe aussi de petites failles intrasédimentaires et des phénomènes d'injection. Aucun organisme constructeur ou capable de piéger et retenir le sédiment n'a été observé. La stabilisation de ces bancs serait due à une couverture végétale (algues ou angiospermes marines) dont on sait qu'elle peut disparâitre sans laisser de trace lors de la fossilisation. La croissance de ces bancs serait réalisée par un apport de sédiment comprenant une part de nourrissage autochtone comme cela existe pour les bancs récents en eau peu profonde, associée au dépôt d'une fraction pélagique.     

Late-Glacial climatic changes in Eastern France (Lake Lautrey) from pollen, lake-levels, and chironomids

High-temporal resolution analyses of pollen, chironomid, and lake-level records from Lake Lautrey provide multi-proxy, quantitative estimates of climatic change during the Late-Glacial period in eastern France. Past temperature and moisture parameters were estimated using modern analogues and ‘plant functional types’ transfer-function methods for three pollen records obtained from different localities within the paleolake basin. The comparison of these methods shows that they provide generally similar climate signals, with the exception of the Bölling. Comparison of pollen- and chironomid-based temperature of the warmest month reconstructions generally agree, except during the Bölling. Major abrupt changes associated with the Oldest Dryas/Bölling, Alleröd/Younger Dryas, and the Younger Dryas/Preboreal transitions were quantified as well as other minor fluctuations related to the cold events (e.g., Preboreal oscillation). The temperature of the warmest month increased by ∼5°C at the start of Bölling, and by 1.5°-3°C at the onset of the Holocene, while it fell by ca. 3° to 4°C at the beginning of Younger Dryas. The comparative analysis of the results based on the three Lautrey cores have highlighted significant differences in the climate reconstructions related to the location of each core, underlining the caution that is needed when studying single cores not taken from deepest part of lake basins.     

Reconstruction of Late Glacial summer temperatures from chironomid assemblages in Lac Lautrey (Jura,France)

A chironomid–July air temperature inference model based on chironomid assemblages in the surface sediments of 81 Swiss lakes was used to reconstruct Late Glacial July air temperatures at Lac Lautrey (Jura, Eastern France). The transfer‐function was based on weighted averaging–partial least squares (WA‐PLS) regression and featured a leave‐one‐out cross‐validated coefficient of determination (r²) of 0.80, a root mean square error of prediction (RMSEP) of 1.53 ° C, and was applied to a chironomid record consisting of 154 samples covering the Late Glacial period back to the Oldest Dryas. The model reconstructed July air temperatures of 11–12 ° C during the Oldest Dryas, increasing temperatures between 14 and 16.5 ° C during the Bølling, temperatures around 16.5–17.0 ° C for most of the Allerød, temperatures of 14–15 ° C during the Younger Dryas and temperatures of ca. 16.5 ° C during the Preboreal. The Lac Lautrey record features a two‐step July air temperature increase after the Oldest Dryas, with an abrupt temperature increase of ca. 3–3.5 ° C at the Oldest Dryas/Bølling transition followed by a more gradual warming between ca. 14 200 and 13 700 BP. The transfer‐function reconstructs a less rapid cooling at the Allerød/Younger Dryas transition than other published records, possibly an artefact caused by the poor analogue situation during the earliest Younger Dryas, and an abrupt warming at the Younger Dryas/Holocene transition. During the Allerød, two centennial‐scale 1.5–2.0 ° C coolings are apparent in the record. Although chronologically not well constrained, the first of these cold events may be synchronous with the beginning of the Gerzensee Oscillation. The second is inferred just before deposition of the Laachersee tephra at Lac Lautrey and is therefore coeval with the end of the Gerzensee Oscillation. In contrast to the Greenland oxygen isotope records, the Lac Lautrey palaeotemperature reconstruction lacks a clearly defined Greenland Interstadial (GI) event 1d and the decreasing temperature trend during the Bølling/Allerød Interstadial. Copyright © 2005 John Wiley & Sons, Ltd.     

Carbonate weathering rates in the Jura Mountains, France-The influence of vegetation

In order to better understand what controls carbonate weathering rates, we report results from the Jura Mountains （East France）, an area exclusively composed of carbonate rocks. This region presents an altitude gradient increasing from 250 m to 1300 m. Over the basin, this gradient generates climatic contrasts of 5℃ and a runoff three times higher in altitude. This place offers a good opportunity for understanding the controlling factors of carbonate weathering. Contrary to thermodynamic calculations that predict the highest concentrations at low temperature, we observe that carbonate dissolution is two times higher at low elevation than in the mountains. This observation can only be explained by a variation in soil pCO2. In order to better constrain the observed variation in cation contents （principally Ca and Mg） of rivers, we used the ASPECTS ecological model （Rasse et al., 2001）. Based on both hourly climatic data, vegetation type and soil type, ASPECTS may reconstruct pCO2 in soil.     

近几十年来黑河野牛沟流域的冰川变化

利用1956年航测、1970/1973年1:50000地形图以及野牛沟流域2003年ASTER影像获取的3期冰川资料,对黑河源头西支野牛沟流域的冰川时空变化进行了分析.通过分析流域气温变化和冰川变化的关系,探讨了流域冰川变化对河川径流的影响.结果表明:野牛沟流域1956—1970/1973年冰川总面积减少9.29%,年平均消退0.54%;1970/1973—2003年冰川总面积减少了18.23%,年平均消退0.60%.流域内冰川条数由1956年的165条减少为2003年的144条,1956—1970/1973年间流域冰川储量减少了2.29×10⁸m³,年均损失约0.13×10⁸m³;从1970/1973年到2003年,冰川储量减少了4.19×10⁸m³,年均损失约0.14×10⁸m³.从1956年到2003年,冰川变化率随着冰川面积的增加而降低,冰川萎缩速度有加快的迹象,而流域年平均温度也有加快升高的趋势.冰川的消退对于流域径流量的影响不大.     

黑河上游冰沟流域典型积雪期水文情势

综合研究了黑河上游祁连山冰沟流域2008年积雪期水文情势,以积雪-冻土-径流为框架详细分析了该地区积雪水文特征.采用物质平衡计算了冰沟流域雪蒸发和融水值,并分析了冻土水热变化过程和融雪径流变化特征.积雪期降水总量达到204.6 mm,雪而蒸发为140.8 mm,雪面蒸发在积雪期水文循环中占有重要的位置.3月12日融雪开始,引起3次人规模的融雪峰值;整个融雪季,冰沟流域融雪径流总嚣为3.98×106m3.冻土解冻始于4月12日左右,随着气温升高,土壤含水量变化明显.地形和风速相巨作用,造成积雪的大规模重新分布.     

Carbonate platform depositional sequences, Upper Cretaceous, south-central Pyrenees (Spain)

The Upper Cretaceous (Cenomanian-Maastrichtian) of the south-central Pyrenees shows five carbonate platform sequences where the major parameters are tectonism, relative sea-level fluctuations and inherited depositional profile. Depositional geometries and basin analysis permit an understanding of the depositional history.Five depositional sequences have been recognized: (1) The Santa Fe sequence (Middle-Upper Cenomanian), a ramp to a skeletal rimmed shelf with an escarpment bypass margin. The lower boundary is an angular unconformity and the upper one records a sea-level drop. The platform location of the margin was determined by a listric normal fault. (2) An abrupt sea-level rise drowned the former platform. The Congost sequence (Turonian-Lower Coniacian), a distally steepened ramp with erosional distal deep slope. The depositional model was largely controlled by pre-existing basin morphology. Cessation of platform development was due to a relative sea-level drop. (3) The Sant Corneli sequence (Upper Coniacian-Lower Santonian), a mixed terrigenous-skeletal homoclinal ramp with upright margin, deep slope and dysaerobic basin. The slope results from the backstepping by 24 km of the previous margin and gentle basin tilting. The platform margin remained more or less at the same position, and relief between platform and slope increased indicating continuous relative sea-level rise. The upper boundary is an angular unconformity at the platform margin produced by an abrupt sea-level rise and platform drowning, and by listric normal faulting. (4) The Vallcarga sequence (Upper Santonian-Campanian), a distal-steepened skeletal homoclinal ramp, erosional escarpment and turbidite basin, which corresponds to the Mesozoic maximum marine expansion. A listric normal fault created two depositional areas: a more or less flat footwall block with a north-northwest prograding carbonate ramp.     

Carbonate Sedimentology of the Upper Riphean (Neoproterozoic) Uk Formation,Southern Urals

Lithology and Mineral Resources - Lithological characteristics and results of the lithofacies analysis of carbonate deposits in the most complete section of the Upper Uk Subformation of the Riphean...     

A new mawsoniid coelacanth (Actinistia) from the Upper Cretaceous of Southern France

Axelrodichthys megadromos sp. nov. is a coelacanth described based on a single specimen collected in the lower Campanian site of Ventabren motorway, Southern France. The new species is referred to the mawsoniids because of the ornamentation of the skull roof and of the proportionally wide supraorbital series. The specimen belongs to the Mawsonia-Axelrodichthys complex based on features present on the lower jaw and on the basisphenoid. The new species is referred to the genus Axelrodichthys because of proportions of its parietonasal shield and because of the arrangement of the posterior parietals relative to the supraorbitals. Autapomorphic characters, in particular on the parasphenoid, justify the inclusion of the specimen in a new species. The occurrence of a mawsoniid in the Ibero-Amorican Island that formed part of the European Archipelago in the terminal Cretaceous is an evidence of a dispersal event from the southern land masses. The occurrence of A. megadromos in the Campanian-Maastrichtian represents the last occurrence of mawsoniids worldwide, after a gap in the fossil record of about 30 million years. This belated occurrence of Axelrodichthys extends the time range of this genus to approximately 40 myr and suggests that this genus, together with its sister genus Mawsonia, were organisms with a slow morphologic evolution.     

Younger Dryas and early Holocene lake-level fluctuations in the Jura mountains, France

Lake-level fluctuations in the Jura mountains (France) during the Younger Dryas and the early Holocene are reconstructed using sedimentological analyses. Major transgressive phases culminated just before the Laacher See tephra deposition, at the beginning of the Younger Dryas, between 9000 and 8000 BP and between 7000 and 6000 BP. The Younger Dryas appears to be characterized by increasing dryness. Other major lowering phases occurred during the middle Allerød and during the Preboreal. A transgressive event developed between c . 9700 and 9500 BP. These palaeohydrological changes can be related to climatic oscillations reconstructed from pollen and isotopic records in Swiss lakes, from glacier movements and timberline variations in the Alps, and from isotopic records in the Greenland ice sheet.     

The mechanisms of overlapping of the Bresse graben by the Jura formations in the Vignoble area (France)

This paper aims to underline how powerful and important the balanced cross-section constructions are for understanding structural mechanisms, especially when several interpretations are possible. In the Vignoble area, between Lons le Saulnier and Arbois — French foothills of Jura, the frontal overlapping is proved by several drillholes. The classical interpretation is a thrusting through listric reverse faults and continuation of the décollement level underlying the Jura at the cover—basement interface. The balanced cross-section construction demonstrates that this assumption is not valid due to the necessary thinning and stretching of the overlapping formations in this region. This paper proposes a new solution where the overlapping, through listric normal faults, is like a huge gravity landslide, without any relation to the shortening and décollement of the internal Jura. The new interpretation is supported by the very consistent balanced crosssection of the displaced cover and by the extension structures observed in the field.     

末次冰消期以来长江口沉积环境演化及沿岸流变化

长江口附近的沿岸流和水团变化对研究长江三角洲沉积物的“源-汇”机制具有重要意义.对HZK2孔沉积物的粒度、年龄和有孔虫分布特征进行了研究分析.结果表明:HZK2孔52.5 m以上有孔虫均有分布,底栖有孔虫丰度在12 m以上和26.0~52.5 m含量超过40枚/g,代表不同沿岸流和水团的有孔虫属种含量在垂向上呈现明显的分带性.HZK2孔全新世以来经历了河口湾和水下三角洲两大沉积体系,并在全新世早期发育潮流沙脊.末次冰消期,钻孔所在位置受长江冲淡水和苏北沿岸流共同影响.全新世早期,则受苏北沿岸流影响为主;在此之后,长江口冲淡水的作用减弱,苏北、黄海沿岸流影响较强.全新世中晚期,苏北沿岸流、长江冲淡水、江浙沿岸流和东海外海水团多种水体共同作用钻孔所在海域,全新世晚期长江冲淡水作用占绝对优势.      

丰水期红枫湖流域氮污染特征的变化规律研究

丰水期对汇入红枫湖的后六河、麻线河、羊昌河和桃花园河等河水中氮素的形态和含量进行测定,结果表明NO3--N是氮素的主要形态,约占TN的25%~65%;三态氮在空间分布上,从上游至下游,四条河流表现出不同的变化规律,后六河NH4+-N、NO2--N与NO3--N的变化规律基本上一致外,含量总体上逐渐增加;其它三条河流中,NH4+-N与NO3--N的含量呈现相反的变化趋势,NO2--N的变化规律则不明显。该流域整体上表现为非点源污染的特征。后六河和麻线河地下水中NO3--N的含量明显高于相应河水中的含量。该研究对亚热带小流域河水中氮磷含量及形态变化研究具有借鉴意义,对该流域的环境规划、环境管理和环境污染治理具有指导意义。     

Carbonate platform-to-basin correlation by means of grain-composition logs: an example from the Vercors (Cretaceous, SE France)

Quantitative logs of grain composition for several sections of platform top and flank of the Vercors carbonate platform (Early Cretaceous, SE France) provide platform-to-basin correlation with a resolution of a few metres over an area of 70 km². Grain composition was determined by point-counting thin sections. Point-count groups that characterize palaeoenvironmental realms (i.e. open sea, platform margin) were defined for the platform–basin trajectory. Grain-composition logs revealed marked peaks in the number of open-sea biota and peaks in ooid abundance. The peaks in open-sea biota correspond to back-stepping intervals and deepening upward facies successions at the platform margin. These peaks probably relate to incipient drowning of the platform and may be used to delineate marine-flooding surface-bounded sequences. Peaks in ooid occurrence show no relationship with the progradation, aggradation or retreat of the platform. Apparently, the oolitic sands were not part of a facies tract that shifted up and down the platform. Instead, they represent a depositional mode that was either on or off. Times of prolific ooid production and shedding probably occurred during wide but shallow submergence of the platform, accompanied by suitable water chemistry. Peaks in both ooids and open-sea biota are excellent markers for platform-to-basin correlation, as they are recorded in successions on the platform top as well as on the flank. Altogether, the grain-composition logs show that each of the lithologically rather similar platform tongues of the Vercors has a unique signature or compositional fingerprint. These compositional fingerprints are most helpful in evaluating the lateral extent of different stratigraphic units. In outcrops of the Vercors platform, the physical tracing of bedding surfaces delineate wedges of toe-of-slope sediments that show a conspicuous thinning towards the platform. However, our correlation shows that these sediment bodies are not truly basin-restricted wedges but have a platform top equivalent. This implies that these units were, at least partly, deposited during high stands of sea level that flooded the platform.     

贵州省第四纪河流阶地沉积分析

本文根据贵州河流阶地发育的情况,各级阶地沉积特征、形成时间、气候和贵州新构造活动等因素,将贵州河流阶地演化分为四个阶段进行讨论。同时,与青藏高原隆升时代进行了对比分析,提出贵州河流阶地形成与青藏高原隆升有密切的联系;同时根据其河流阶地的演化,提出贵州的河流阶地成因模式为构造-气候旋回模式。     

Platinum-Group Minerals from the Durance River Alluvium,France

Summary Platinum-group minerals were discovered, during gold recovery, in the Durance river alluvium, near Peyrolles (Bouches-du-Rhône). The PGM grains (average size 130 microns) are strongly flattened (average thickness 64 microns). The PGM concentrate consists primarily of (Pt, Fe) alloys (92%), (Os, Ir, Ru) alloys (3.5%), and native gold and (Au, Cu, Ag) alloys (4.5%). The following minerals were observed: isoferroplatinum, ferroan platinum, native osmium, native iridium, iridosmine, rutheniridosmine, osmiridium, ruthenian osmium, osmian ruthenium, cuprorhodsite, guanglinite, shandite, tetrauricupride, native gold, bornite, heazlewoodite, (Pt, Pd)₂Cu₃, Pt(Cu, Au), (Ni, Pt)Sn, (Cu, Fe)_1–x (Pd, Rh, Pt)_2+xS₂, (Pt, Pd)_4–xCu₂As_1–x. Isoferroplatinum contains numerous inclusions of alloys, sulphides, arsenides, Pd-tellurides, and partly devitrified silicate glass droplets. Most of the non-silicate inclusions also exhibit a drop-like shape indicating their original entrapment in a liquid state.Cuprorhodsite crystals (up to 20 microns) are associated with bornite included in Pt₃Fe. Rarely, Pd- and Cu-sulphides, and Pd-tellurides appear in this association. Complex droplet-like arsenide inclusions in isoferroplatinum are composed of Pt bearing guanglinite and (Pt,Pd)_4+xCu₂As_1–x. Native iridium shows exsolutions of Ir-bearing isoferroplatinum and (Pt,Pd)₂Cu₃. In places, concentrations of Sn (up to 3 wt.%) were observed in (Au, Cu) alloys. Shandite and (Ni, Pt)Sn inclusions occur in (Au, Cu, Ag) alloys. Silicate-glass inclusions are TiO₂-poor and occasionally K-rich (plotting in the shoshonitic field). Taking into account mineralogical and chemical pecularities of the PGM association occurring in the studied concentrate, it seems highly probable that its primary source should be an Alaskan-type intrusion.

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Platingruppen Minerale aus dem Alluvium der Durance, Frankreich

Zusammenfassung Minerale der Platingruppe wurden im Zuge von Goldgewinnung im Alluvium der Durance in der Nähe von Peyrolles (Bouches-du-Rhône) entdeckt. Die PGM Körner (durchschnittliche Korngröße 130m) sind flach gepreßt (durchschnittliche Dicke 64m). Die PGM Konzentrate bestehen vorwiegend aus (Pt, Fe) Legierungen (92%); (Os, Ir, Ru) Legierungen (3,5%), sowie gediegen Gold und (Au, Cu, Ag) Legierungen (4,5%). Folgende Minerale wurden beobachtet:Isoferro-Platin, Fe-Platin, gediegen Osmium, gediegen Iridium, Iridosmium, Rutheniridosmium, Osmiridium, Ru-Osmium, Os-Ruthenium, Cuprorhodsit, Guanglinit, Shandit, Tetrauricuprit, gediegen Gold, Bornit, HeazIewoodit, (Pt, Pd)₂ Cu₃, Pt(Cu, Au), (Ni, Pt)Sn, (Cu, Fe), (Pd, Rh, Pt)_2+xS₂, (Pt, Pd)_4+xCu₂As_1–x.Isoferro-Platin enthält zahlreiche Einschlüsse von Legierungen, Sulfiden, Arseniden, Pd-Telluriden und teilweise devitrifzierte Silikatglaströpfchen. Die meisten nichtsili katischen Einschlüsse sind ebenfalls tröpfchenförmig. Dies weist darauf hin, daß sie in flüssigem Zustand eingeschlossen wurden.Cuprorhodsitkristalle (bis zu 20m) sind gemeinsam mit Bornit in Pt₃ Fe einge schlossen. Selten sind Pd- und Cu-Sulfide, sowie Pd-Telluride mit diesen vergesellschaftet. Bei den komplexen tröpfehenförmigen Arsenideinschlüssen im Isoferro-Platin handelt es sich um Pt-führenden Guanglinit und (Pt, Pd)_4+xCu₂ As_1–x. Gediegen Iridium zeigt Entmischung von Ir-führendem Isoferro-Platin und (Pt, Pd)₂Cu₃. Stellenweise wurden Konzentrationen von Sn (bis zu 3%) in den (Au, Cu) Legierungen beobachtet. Shandit und (Ni, Pt) Sn Einschlüsse kommen in (Au, Cu, Ag) Legierungen vor. Silikatische Glaseinschlüsse sind TiO₂-arm und manchmal K-reich (im Shoshonitfeld liegend).Auf Grund der mineralogischen und chemischen Eigenheiten der untersuchten PGM Konzentrate ist eine Intrusion des Alaska-Typs als primäre Quelle sehr wahrscheinlich.

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With 4 Figures and 2 Plates     

Distribution of nitrifying activity in the Seine River (France) from Paris to the estuary

The distribution of nitrification has been measured with the H¹⁴CO₃ ⁻ incorporation method in the Seine River and its estuary during summer conditions. The Seine River below Paris receives large amounts of ammonium through wastewater discharge. In the river itself, this ammonium is only slowly nitrified, while in the estuary nitrification is rapid and complete. We show that this contrasting behavior is related to the different hydrosedimentary conditions of the two systems, as nitrifying bacteria are associated with suspended particles. In the river, particles and their attached bacteria either rapidly settle or have a sestonic behavior. Because of the short residence times of the water masses, the slow growing nitrifying population has no time to develop sufficiently to nitrify the available ammonium. The estuary is characterized by strong tidal dynamics. Particles settle and are resuspended continuously with the strong current inversions of ebb and flood. As a result of these dynamics, particles and their attached nitrifying bacteria experience longer residence times in a temporary suspended state than the water masses themselves, providing to slow growing nitrifying bacteria the opportunity to develop a large population capable of nitrifying all the available ammonium.     

Mercury speciation in soils of the industrialised Thur River catchment (Alsace,France)

Methylmercury (MeHg) and total Hg (THg) concentrations in soil profiles were monitored in the Thur River basin (Alsace, France), where a chlor-alkali plant has been located in the city of Vieux-Thann since the 1930s. Three soil types were studied according to their characteristics and location in the catchment: industrial soil, grassland soil and alluvial soil. Contamination of MeHg and THg in soil was important in the vicinity of the plant, especially in industrial and alluvial soil. Concentrations of MeHg reached 27 ng g⁻¹ and 29,000 ng g⁻¹ for THg, exceeding the predictable no effect concentration. Significant ecotoxicological risk exists in this area and remedial actions on several soil types are suggested. In each type of soil, MeHg concentrations were highest in topsoil, which decreased with depth. Concentrations of MeHg were negatively correlated with soil organic matter and total S, particularly when MeHg concentrations exceeded 8 ng g⁻¹. Under these conditions, MeHg concentrations in soil seemed to be influenced by THg, soil organic matter and total S concentrations. It was found that high MeHg/THg ratios (near 2%) in soil were mainly related to the combined soil environmental conditions such as low THg concentrations, low organic C/N ratios (<11) and relatively low pH (5–5.5). Nevertheless, even when the MeHg/THg ratio was low (∼0.04%), MeHg and THg concentrations were elevated, up to 13 ng g⁻¹ and to 29,000 ng g⁻¹, respectively. Thus, both THg and MeHg concentrations should be taken into account to assess potential environmental risks of Hg.