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    Evolution of a rift basin dominated by subaerial deposits: The Guaritas Rift, Early Cambrian, Southern Brazil
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    Keywords:
    Subaerial
    Alluvial fan
    Tectonic subsidence
    Rift valley
    East African Rift
    Rift zone
    Inland soda and saline lakes of the East African Rift Valley (EARV). This study reviews the chemical properties of inland soda-saline lakes of the EARV, classifies lake water chemical types, and assesses the spatial distribution of the major ions. The chemical data were collected from published articles (1968–2022) where the salinity (TDS) exceeded 1 g/l concentration. Based on the total alkalinity and pH, the modified formula was used to estimate the concrete proportions of CO32- and HCO3-. The lake's water chemical type was classified using (Boros and Kolpakova, 2018) classification criteria. ESRI ArcMap 10.2 GIS software was used to analyze the spatial distributions of major ions. Following the critical review of the EARV soda saline lakes the dominance of cations and anions followed the order: Na+ > K+ > Ca2+ > Mg2+ and HCO3- + CO3- > Cl- > SO42-. Tanzania had the most soda-chemical type lakes (20), followed by Ethiopia (9), Kenya (8), and Uganda (4). Soda-saline lakes were the most common in Tanzania (5). Saline lakes were mostly found in Uganda (4), Tanzania (3), and Ethiopia (1). Except for Afrera Lake in North Ethiopia and Uganda (Western Rift), the concentration of Na+, Cl-, CO3- ions, and TDS showed an increasing concentration gradient tendency from north to south in the Eastern Rift.
    East African Rift
    Rift valley
    Alkalinity
    Dominance (genetics)
    Saline water
    Total dissolved solids
    Citations (14)
    All the epicenters determined in the central part of the West African Rift Valley up to the middle of 1958 have been plotted on a map. Most of them are on the faults which border the Rift; a few are on faults which crosscut it. The eastern Virunga ‘extinct’ volcanoes show a fairly strong seismic activity. The most important discovery is that of a transverse zone stretching west from Lake Kivu to the Congo River (450 km); extinct or active volcanoes are located at the intersection of this zone with the Rift Valley. Diagrams show the amount of seismic energy liberated per year within 500 km of Lwiro. The mean value is 3.5×1020 ergs/year, which is about 0.03 per cent of that of the earth as a whole.
    East African Rift
    Rift valley
    Rift zone
    Citations (43)
    The rift valley lakes of East Africa exhibit considerable variety in size, hydrology, hydrochemistry, and sedimentary regime. Although tectonics and climate are ultimately responsible for lake formation, vol-canism may exert a significant influence upon the lake characteristics. In the Eastern Rift (Kenya, Ethiopia), extensive volcanic activity has disrupted drainage and helped create small, shallow lake basins. Weathering of volcanic rocks produces runoff waters rich in and , and smectite is a common clay mineral. In contrast, the Western Rift (Uganda, Mozambique) has localized volcanism; the lakes are large and deep with significant fluvial influents and effluents. Dissolved and are proportionately greater and detrital mineralogy is more variable. Carbonates and evaporites also reflect the hy-drochemical differences. In addition, the topographic elevation of the lake within the rift may determine the composition and rate of sedimentation.
    East African Rift
    Rift valley
    Rift zone
    Citations (30)