Sediment characteristics and water physicochemical parameters of the Lysimachia Lake, Western Greece

In the present paper, we present the sedimentological characteristics and the water physicochemical parameters of Lysimachia Lake, which is one of the most important lakes of Western Greece, as it is protected by international conventions and is listed in the Natura 2000 European Network. Sedimentological analysis involved grain size analyses, moment measures, total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) measurements, as well as determination of the clay minerals content. Water physicochemical parameters such as pH, temperature, conductivity and dissolved oxygen were measured in situ with portable equipment, while nutrients such as nitrates, nitrites, phosphates and ammonium ions, as well as TOC and TN were analyzed in a time period of 1 year seasonal monitoring. Geographical distribution of grain size and geochemical parameters indicated a clear partition in the northern and southern parts of the lake. This phenomenon can related to the discharging of a channel into the lake, the discharging of sewage effluents from Agrinio city during the last years as well as the type of clay minerals distribution. Clay minerals analyses indicated that smectite predominates in the northern part of the lake, whereas chlorite is more abundant in the southern parts. This explain the higher amounts of TOC and TN observed in the northern part of the lake and can be correlated with the higher external surface and adsorption capacity of minerals in the smectite-rich sediments. The four seasons monitoring of water physicochemical parameters indicates a relatively higher values of TOC and TN in the northern part of the lake, while nutrient concentrations indicate a uniform geographical distribution along the lake.     

Chernobyl 137Cs redistribution in the small basin of the Lokna river,Central Russia

The redistribution of Chernobyl ¹³⁷Cs within a small drainage basin was studied in the Lokna river basin, Tula region, Central Russia. Sheet erosion on the cultivated part of basin is the main reason for ¹³⁷Cs horizontal migration. However there is no statistically significant ¹³⁷Cs redistribution within cultivated field because of relatively low erosion rates. The valley bottom is the main sink of ¹³⁷Cs, where 73–84% eroded soil is stored. The resulting ¹³⁷Cs level in the valley bottom is 1.5–2 times that of the initial ¹³⁷Cs fallout.     

Hydrological and geochemical characteristics of the Jamari and Jiparana river basins (Rondonia,Brazil)

The authors investigate the hydrological and geochemical characteristics of the Jamari (30430 km²) and Jiparana (60350 km²) river basins (Amazonia), during the period 1978–1984. A spectral analysis of Fourier is applied to time series of mean monthly river discharges, in order to assess the contribution (7 to 8%) of the surface runoff to the total river flow. The mean annual runoff coefficient calculated for the Jiparana river basin (36%), is higher than for the Jamari (32%), and this coefficient increases during the study period, only for the Jiparana. The total specific suspended sediment discharge calculated for both rivers shows the same value 13 t/km²/y, and the estimated suspended sediment concentration in the surface runoff is slightly superior for the Jiparana river (0.3 g/l) than for the Jamari one (0.2 g/l). The river suspended sediments are mainly composed of kaolinite, quartz and feldspar, but the Jiparana is more enriched in quartz. For both rivers, the dominant clay mineral is the kaolinite which is in agreement with the rock weathering type determined for both basins using the Tardy's weathering index: the monosiallitisation. The total chemical erosion rate calculated after correction for the atmospheric inputs (ions and CO₂), is higher for the Jiparana (10.11 t/km²/y) than for the Jamari river basin (7.75 t/km²/y). These values are lower than the mechanical denudation rate calculated previously for both river basins.     

燕山山地伊逊河下游河流阶地沉积物特征及古环境意义

河流沉积物蕴藏着其形成之时水动力条件及古气候变化等重要信息,因此研究河流相沉积物不仅可指示其沉积之时的水动力条件,还可对其反演的古气候进行一定的探索。伊逊河地处燕山东段,开展其下游河流相沉积物粒度、磁化率及形成年代的探讨,可为燕山山地河流相沉积物蕴藏的古环境意义研究提供参考。笔者等通过野外实地调查、光释光测年、粒度分析及磁化率实验对伊逊河下游三级阶地（T3）前缘剖面展开研究,初步确立了伊逊河下游T3的形成时间,大致为晚更新世晚期至全新世早期（13.14±0.76 ka BP至9.55±0.58 ka BP）,结合野外实测及实验数据分析发现此剖面可划分为11层,探讨了伊逊河在晚更新世晚期至全新世早期水动力条件的变化,厘定了伊逊河下游9次较为明显的水文事件,并提出新仙女木事件始末及全新世初期此剖面沉积物记录与多种气候变化指标和区域气候变化有较高的一致性,揭示了伊逊河下游河流阶地沉积物对气候变化的响应较为明显,研究结果为该地区古环境研究提供了基础地质依据。     

燕山山地伊逊河下游河流阶地沉积物特征及古环境意义

河流沉积物蕴藏着其形成之时水动力条件及古气候变化等重要信息,因此研究河流相沉积物不仅可指示其沉积之时的水动力条件,还可对其反演的古气候进行一定的探索.伊逊河地处燕山东段,开展其下游河流相沉积物粒度、磁化率及形成年代的探讨,可为燕山山地河流相沉积物蕴藏的古环境意义研究提供参考.笔者等通过野外实地调查、光释光测年、粒度分析...     

Archaean and Lower Proterozoic units in Central Brazil

The following main units have been recognized as Archaean basement rocks in central Brazil: a) High-grade granite-gneiss terrain composed predominantly by granodioritic and tonalitic gneisses; these rocks are cut by amphibolite dykes and present several nucleii locally surrounded by an array of Archaean greenstone belts, b) Greenstone belts presenting basal komatiitic ultramafic-mafic lavas with abundant spinifex textures, followed by basalts and chemical sediments such as cherts, limestones and graphitic pelites, that are often interbedded with acid and intermediate volcanics; metamorphism is within greenschist facies. Granulite mobile belt, including the granulitized mafic-ultramafic complexes of Barro Alto, Niquelândia and Brava. The Lower Proterozoic is represented by: a) metasedimentary sequences overlying the granite-greenstone terrains, with several tin bearing granite intrusions. b) Gabbro-anorthosite layered plutons and their associated mafic volcanics which are followed by acid and intermediate volcanics and ocean floor sediments. c) Mafic-ultramafic layered intrusions in the granulite terrain.

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Zusammenfassung Im zentralen Brasilien wurden folgende Haupteinheiten als Archaischer Sockel erkannt: a) hochmetamorphes Granit-Gneis-Gebiet mit vorwiegend granodioritischen und tonalitischen Gneisen; diese Gesteine werden von amphibolitischen Gängen durchschlagen. Sie bilden einzelne Kerne, die von Zonen Archaischer Grünsteingürtel umgeben werden. b) Grünsteingürtel, die basale komatiitische ultramafitische bis mafischen Laven representieren mit häufig auftretenden Spinifex-Gefügen. Diesen folgen Basalte und chemische Sedimente wie Kieselschiefer, Kalke und graphitische Pelite, in die häufig saure und intermediäre Vulkanite eingeschaltet sind. Die Metamorphose liegt in der Grünschiefer-Fazies. c) Mobiler Granulit-Gürtel, der die granulitisierten mafisch-ultramafischen Komplexe von Barro Alto, Niquelândia und Cana Brava einschließt.Das untere Proterozoikum wird durch folgende Einheiten vertreten: a) Metasedimentfolgen, die die Granit-Grünstein-Serien überlagern und die einige zinnführende GranitIntrusionen aufweisen. b) Lagige Gabbro-Anorthosit-Plutone mit dazugehörenden mafischen Vulkaniten, die von sauren und intermediären Vulkaniten und ozeanischen Sedimenten gefolgt werden. c) Mafisch-ultramafische Intrusionen innerhalb des Granulit-Gebietes.

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Resumo As seguintes unidades geológicas principais foram reconhecidas no embasamento da região central do Brasil: a) Terrenos granito-gnáissicos constituídos dominantemente por gnaisses de composição granodiorítica e tonalítica cortados por diques de anfibolito e mostrando vários núcleos graníticos localmente envolvidos por seqüências vulcano-sedimentares do tipo greenstone belt. b) Cinturões arqueanos de rochas verdes apresentando na base lavas komatiíticas com abundantes texturas tipo spinifex, seguidas de basaltos almofadados e de sedimentos químicos tais como chert, calcário e pelitos grafitosos, frequentemente intercalados com vulcânicas intermediárias e ácidas; o metamorfismo é de facies xisto verde. c) Cinturão móvel granulítico incluindo os complexos granulitizados de Barro Alto, Niquelândia e Cana Brava. Proterozóico Inferior é representado por: a) Seqüências sedimentares sobrepostas aos terrenos granito-greenstone, localmente intrudidas por granitos estaniferos; b) Plutões gabro-anortosíticos acamadados; c) Intrusões máfico-ultramáficas alojadas nos terrenos granulíticos.-- : ) - ; , , ) , . , , , , , . ; ) , - Barro Alto, Niguelandia Brava. : ) , - , , ; ) -- , ; ) - .

     

Supply and Removal of Sediment in a Landslide-Dominated Mountain Belt: Central Range, Taiwan

A strong coupling between hillslope and valley systems is often inferred for mountain landscapes dominated by bedrock landsliding. We reveal the nature of this link using data sets on landsliding and sediment transport from two montane catchments draining the eastern Central Range of Taiwan. Here, the magnitude-frequency distribution of landslides can be modeled by a robust power law, but this scale invariance is not mirrored in the sediment discharge at the mountain front. Instead, downstream sediment loads reflect a complex response to both sediment supply and ambient hydraulic conditions. The rivers do not transport significant amounts of sediment unless it is provided by hillslope mass wasting in the catchment. Removal of landslide debris is a function of the transport capacity of the stream at the site of entry; thus, there is a dual supply and transport control on sediment loads in bedrock-floored streams. Over a monitoring period of >25 yr, the bulk of the sediment leaving the mountain belt was supplied by climate-triggered mass wasting. Peaks in water discharge were always closely followed by sediment load maxima, and the rapid decay of the latter indicates an effective removal of most supply. Where an important part of a catchment's sediment yield is derived from interfluves, sediment transport cannot simply be estimated from known water discharge time series, using a sediment rating curve, but requires instead a detailed knowledge of the spatial and temporal patterns of hillslope mass wasting and sediment transfer into the fluvial system.     

Groundwater geochemistry of a small reservoir catchment in Central Tunisia

Due to the scarcity of water resources in semiarid sedimentary basins, hill reservoirs are often constructed to recharge groundwater and limit runoff induced water loss. The impact of such reservoirs on groundwater chemistry is investigated in the aquifers of the El Gouazine watershed, Central Tunisia. Three groundwater types are recognised, Ca–HCO₃, Na–Cl and Ca–SO₄. The strong similarity between host rock and groundwater chemistries indicates significant rock–water interaction. A flowpath, along which the chemical composition of the groundwater evolves, can be identified using the contrast in stable isotope signature between upstream and downstream groundwater. Shallow upstream groundwater is recharged by the infiltration of rainwater with the rate of recharge strongly linked to the permeability of the host lithology. Calcium and HCO₃ are supplied to an alluvial aquifer from a more rapidly recharged limestone aquifer with the concentration of Ca and HCO₃ ions decreasing by dilution. The alluvial aquifer is also enriched in Ca and SO₄ during the downstream flow of groundwater through gypsiferous materials. There is evidence of mixing between meteoric groundwater and evaporated reservoir water. Below the reservoir and partly responsible for reservoir leakage is a sandy aquifer, formed by weathering and erosion of a sandstone host which also supplies water to the alluvial aquifer.     

Effects of multiple source pollution on a small Mediterranean river

The small Mediterranean riverine system of the Litheos river, which flows through the city of Trikala, and its drainage area are subjected to pollution from point and non point sources,which results in poor quality of surface waters. The pollution sources include urban activities, agriculture, industrial activities, handicrafts and traffic. The concentration levels and the geochemical behaviour of nutrients, trace metals and organic pollutants were studied during the period 1991–1992, in a project supported by the Municipality of Trikala. The simultaneous existence of several polluting sources leads to significant variations in the concentrations and distributions of main pollutants, which are elevated in the neighbourhood of polluting activities in various parts of the river (NO₃⁻ above the city, NH₃, NO₂⁻ and detergents near central rainwater collector, into the city, P04 below the city, near the waste water treatment plant, PAI-Is and metals in another river branch in the ‘industrial’ zone of the city). The appearance of concentration maxima of various pollutants in various parts of the river indicates environmental problems in the whole length of the river. The water quality is significantly influenced and in most cases is unsuitable for human consumption. The mean values of the main pollutants in Litheos (NO₃⁻ 4.0 mg N/1, NH₃ 0.23 mg N/1, NO₂⁻ 0.10 mg N/1, P 0.37 mg P/1, Cu 7.1 μg/l, Pb 4.8 μg/l, Zn 3.9 μg/l, Ni 12.8 μg/l, Cr 3.5 μg/l) characterize Litheos as a moderately polluted river, but the observation of eutrophication phenomena and the appearance of some high concentrations of heavy metals and/or organic pollutants in certain parts of the river reveal that a serious effort must be made in order to avoid further deterioration of Litheos water quality.     

Sediment characteristics and mineralogy of salt mounds linked to underground spring activity in the Lop Nor playa,Western China

Salt mounds are commonly distributed along playa margins and typically comprise alternating layers of loose fine sand and slightly hard halite-rich sediments as a result of long-term underground spring activity. A model of salt mound development was constructed for this study. It suggests that wind-blown sand supply and upward recharge of underground springs are two important factors in salt mound construction. Furthermore, it proposes that salt mound height is mainly controlled by the vertical transport range of underground springs and the thickness of the capillary fringe. A 1.5 m representative profile dug from the center of salt mound LP1 in the Lop Nor playa revealed a fairly complicated mineral assemblage including halite, gypsum, anhydrite, glauberite, epsomite, anhydrite, calcite, bischofite, polyhalite, schoenite, kieserite and carnallite. This matches closely with the assemblage predicted by the EQL/EVP model. The groundwater in the area is highly concentrated brine rich in Cl⁻ and Na⁺ and poor in Ca²⁺, displaying low alkalinity, and containing considerable amounts of SO₄²⁻, Mg²⁺ and K⁺. Chemical analysis of groundwater revealed considerable variation in the salinity and chemical composition of groundwater over time. The Cs-137 technique was used to measure the accumulated ages of the salt mounds. This method may prove useful in the research of relatively young playa environments where carbon dating techniques are unworkable because of an absence of carbon-rich materials in recent saline sediments.     

Assessment of characteristics and distinguished hydrological periods of a river regime

This study was carried out to analyze the hydrological characteristics and assess the distinguished hydrological periods of Upper Indus Basin (UIB) Rivers of Pakistan. For this purpose, statistical analysis (variation coefficient, the auto-correlation coefficient, sequential Mann–Kendall’s test) and a proposed method for distinguishing hydrological periods (described in methodology section) were applied. The results revealed that all rivers reflect moderate variability. The results of auto-correlation displayed that the river flow observed at Astore gauging station only indicated independency, while for Gilgit, Hunza and Kachura guaging at Indus River exhibited 2, 2, 4-year lag. The mutation analysis indicated that after 1980, the change point occurred at all UIB rivers. During analysis, it was also observed that river regimes have the same hydrological periods (i.e., 4), but with different dates of occurrence. The Gilgit River showed a low high-flow hydrological period compared to Astore, Hunza and Kachora (Indus). This difference may be due to the river’s own area natural conditions. The current analysis may be helpful for planning and management of water resources, designing of hydraulic structures and to make better policies in response to agricultural water requirement downstream of UIB River.     

贵州中西部地区煤层气成藏特征

基于贵州地区煤层气富集成藏条件,结合统计资料和实验测试数据成果．从含气性、储层物性及成藏规律三个方面探讨了贵州中、西部地区煤层气藏特征。结果表明：贵州中、西部地区2000m以浅煤层气资源量约31511亿m^3,资源丰度高,一般〉2亿m^3／km^2,最高可达7．15亿m^3／km^2,主要集中分布在六盘水煤田、织纳煤田及黔北煤田煤,且以富甲烷（〉8m^3／t）为主,500m以深范围内煤层气CH4含量〉80％;不同地区不同煤层的孔裂隙发育、渗透性、吸附能力、解析能力、储层压力及储层压力系数等差别较大,地域、层域差异明显,煤储层原地应力较高,原地应力梯度普遍〉1．5MPa／100m;区内煤系地层“广覆式”生烃．沉积构造史控制着气田的分布,并以大型向斜或复向斜为煤层气富集主要场所。     

The coastal transition at the mouth of a small mountainous river in Taiwan

The Tseng-wen River is a small mountainous river in southern Taiwan that has distinct dry and flood seasons. Several lines of evidence have revealed that the depositional system at the mouth of the river has transformed from a deltaic system to an estuarine system. The evidence includes long to short-term shoreline changes, geomorphology of the river mouth, mixed sediment sources inside the river mouth, mixing and suspended sediment characteristics inside the river mouth, and the grain-size distribution patterns on the river bed. Unlike the long-term evolution of many other coastal systems, the transformation at the Tseng-wen River mouth is largely caused by the building of a reservoir in the middle reaches of the river. The present study provides an example that coastal environments can be influenced by human activities farther inland on a time scale much faster than what would occur naturally.     

Sediment pathways and transport rates through a tide-dominated entrance, Rangaunu Harbour, New Zealand

Bed load sediment traps were deployed at two sections across channels in Rangaunu Harbour entrance. Traps were inspected and emptied by divers at hourly intervals through both spring and neap tidal cycles for a total of 292 trap deployments. Current velocities were measured simultaneously with the trap inspections. Transport is concentrated in sandy megaripple fields on the channel banks and sub-tidal platforms flanking the channels. There, transport is almost continuous throughout the tidal cycle, increasing with flow velocity but lagging by approximately one hour. The channel floors are lined with shell-gravel lag across which bedload transport rates are low and discontinuous. Tidal asymmetry produces a net seaward transport through the channel troughs and a net landward transport across the channel banks and flanking sub-tidal platforms. Sediment leaving the harbour recirculates in anticlockwise gyres across the ebb-tide delta to re-enter the harbou and maintain the supply of sand to the megaripple field. Transport during spring tides is typically 25–30 times that during neaps. Predictions of transport rates, from a method developed by Black & Healy utilizing the Yalin bedload equation, produced transport rates similar to the traps over sand beds. Transport over shell lag surfaces appears independent of near-bed velocity and more dependent on the passage of ribbons of sand across the lag surface.     

Sediment dynamics and hydrodynamics in the lower course of a river highly regulated by dams: the Ebro River

The lowest part of the Ebro River is a microtidal salt-wedge estuary. Penetration of the salt-wedge is largely controlled by the fluvial discharge and the morphology of the river bed, although sea level variations caused by tides and atmospheric conditions can also play significant roles. The concentration and distribution of suspended particulate matter in this part of the river and the fluvial sediment discharge are strongly influenced by the dynamics of the salt-wedge. Damming of the river has caused sediment to be trapped in reservoirs and has regulated the fluvial discharge. Intrusion of the salt wedge has thus also been regulated. At present, sediment discharge is between 1 and 1·5 × 10⁵ tons per year, which is less than 1% of the sediment that the Ebro River discharged into the sea before construction of the dams. This extreme reduction in sediment supply has allowed marine erosional processes to dominate in the delta.     

Tertiary--Quaternary Extension-Related Alkaline Magmatism in Western and Central Europe

Primitive mafic alkaline volcanic rocks from the Tertiary-Quaternaryextension-related magmatic province of western and central Europehave major and trace element and Sr–Nd–Pb isotopiccharacteristics which suggest the involvement of both lithosphericand asthenospheric mantle source components in their petrogenesis.Oxygen isotope data for the volcanic rocks, mantle xenoliths,and lower-crustal mafic xenoliths indicate that extensive crustalcontamination is not involved in the petrogenesis of these magmas. The geochemical characteristics of the lithospheric componentare in part constrained by those of spinel lherzolite and maficgranulite xenoliths entrained within the magmas. This componentappears to be the product of partial melting of phlogopite/amphibole-bearingmantle which was meta-somatized as a consequence of magmaticactivity during and preceding the Hercynian orogeny and duringphases of Permo-Carboniferous extension. Partial melting ofphlogopite is required to account for the generation, of potassicmagmas (leucitites and leucite nephelinites) with K₂O/Na₂O>1. This component appears to differ between the individual Hercynianterrane blocks of Europe, reflecting, in part, their previousmagmatic histories. The asthenospheric component has affinities with the sourceof St. Helena type (HIMU) OIB and may, in part, be 500–400 Ma recycled oceanic lithosphere subducted during the Hercynianorogeny. Alternatively, it could represent a zone of enrichedmantle at the base of the subcontinental lithosphere which ispreferentially partially melted during extension. There appearsto be no need to invoke the existence of deep mantle plumesto explain the HIMU characteristics, although the data do notpreclude them.     

Sediment accumulation rates in Conowingo reservoir as determined by man-made and natural radionuclides

The Susquehanna River is the major contributor to sediment loadings in the Chesapeake Bay. Because many environmental contaminants are associated with suspended particulates, the degree of particle retention within the reservoirs of the lower Susquehanna River is an important consideration in evaluating contaminant loadings to the Chesapeake Bay. Profiles of weapons-test Cs-137, nuclear power plant-related Cs-134 and Cs-137, and naturally-derived Pb-120 were used to estimate rates of sediment accretion in the conowingo Reservioir, an impoundment of the Susquehanna River along the Maryland-Pennsylvania border. Net accretion rates ranged from about 2 cm yr^?1 downstream of a nuclear power plant cooling discharge to a high of about 7 cm yr^?1 at the mount of an incoming creek. Slight, but consistent, increases in the annual rate of accretion since the creation of the reservoir in 1928 are apparent. The current net average annual sediment load reatined by the reservoir is estimated to be 0.4×10⁶ to 1.5 × 10⁶ metric tons yr^?1. The retained sediment load represents about 8–23% of the long-time average sediment input to the reservoir.     

Challenges of an integrated water resource management for the Distrito Federal, Western Central Brazil: climate, land-use and water resources

Land-use/cover change (LUCC) and climate change are major controlling factors for water resources in the Distrito Federal in Western Central Brazil. Dynamic LUCC in the region has severe impacts on water resources, while climate changes during the last three decades is thought to have only moderate effects. LUCC affects water quantity mostly during base flow conditions. River basins with substantial expansion of agriculture since the end 1970s show a dramatic decrease of base flow discharge by 40?C70%, presumably due to irrigation. In contrast, the effects of urbanization on runoff are less distinct, since factors controlling runoff generation might be more variable. For water quality, we found urban areas to have a strong influence on the parameters CSB, NH₄ ⁺, and suspended solids. In addition, we assume emerging pollutants, e.g. organic (micro)pollutants, might play a major role in the future. The project IWAS-áGUA DF focuses on creating the scientific base to face these problems in frame of an IWRM concept for the region. Results of our study will be a contribution to an IRWM concept for the Distrito Federal and will help to maintain high standards in water supply for the region.     

Geosynclinal evolution of the Epi-Baykalian platform of Central Brazil

Evidences of geosynclinal polarity (orogenic and sedimentary) in foldbelts of Central Brazil led the authors to the recognition of seven tectonic isopic zones as parts of a wide geosynclinal system policyclically developed during a long Baykalian Cycle of 1,500-500 m. y. ago. Tectonic and stratigraphic evolutions are reinterpreted on the light of the new concepts.The orogenic polarity of contiguous miogeosynclinal and eugeosynclinal foldbelts provided the basis for enlarging the Brasiliane Cycle of short duration (850–550 m. y.) to a Brasiliane Cycle of 1,500-550 m.y. (= Baykalian Cycle). The Minas Cycle is viewed as a phase within a distinct platform-making process.

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Zusammenfassung Die PolaritÄt orogener und sedimentÄrer Erscheinungen in Geosynklinalen der Faltengürtel Zentralbrasiliens veranla\te die Autoren, sieben tektonische Zonen als Teile eines gro\rÄumigen geosynklinalen Systems, das wÄhrend eines langen Baykalischen Zyklusses vor 1500 bis 500 Millionen Jahren entstand, zu unterscheiden. Tektonische und stratigraphische Entwicklungen werden im Lichte dieser neuen Auffassung neu interpretiert.Die orogene PolaritÄt von aneinandergrenzenden miogeosynklinalen und eugeosynklinalen Faltengürteln lieferte die Grundlage für die Erweiterung des Brasilianischen Zyklusses von kurzer Dauer (850-550 Millionen Jahre) zu einem Brasilianischen Zyklus von 1500-500 Millionen Jahren (=Baykalischer Zyklus). Der Minas-Zyklus wird als eine Phase innerhalb eines Plattform bildenden Prozesses angesehen.

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Résumé Certaines évidences de polarité géosynclinale (orogéniques et sedimentaires) dans les régions plissées du Brésil Central ont conduit les auteurs a établir sept zones tectoniques rassemblées dans un seul système géosynclinal, qui s'est développé policycliquement au cours d'un Cycle Baykalien de 1500 à 500 millions d'années. Les évolutions stratigraphiques et tectoniques sont réinterprétées à la lumière de nouveaux concepts.La polarité orogénique du couple eugéosynclinal-miogéosynclinal de ces zones plissées a fourni des données suffisantes pour étendre les limites du Cycle Brésilien (= Baykalien) de 850–550 millions d'années à 1500–550 millions d'années: le Cycle Minas est devenu simplement une phase dans ce processus de formation de plateformes.

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