Rift lake

Table 3 lists examples of more than a dozen different chemical types of river water. Although Ca and HCO j" are generally dominant, Mg dominance over Ca + can be found in rivers draining various lithologies such as basalt, peridotite, serpentinite, dolomite, coal, or where hydro-thermal influence is important (Semliki). Sodium may dominate in sandstone basins, in black shales (Powder, Redwater in Montana), in evaporitic sedimentary basins (Salt), in evaporated basins (Saoura), and where hydrothermal and volcanic influence is important (Semliki, Tokaanu). rarely exceeds 4% of cations, except in some clayey sands, mica schists, and trachyandesite it exceeds 15% in extremely dilute waters of Central Amazonia and in highly mineralized waters of rift lake outlets (Semliki, Ruzizi). 

Hillaire-Marcel, C., Aucour, A.-M., Bonnefille, R., Riollet, G., Vincens, A., and Williamson, D. (1989). C/palynological evidence of differential residence times of organic carbon prior to its sedimentation in East African rift lakes and peat bogs. Q. Sci. Rev. 8,207-212. 

Lake Tanganyika lake level changes and mixing regimes in a tropical rift lake... 

Lake Baikal differentiating turbiditesfrom other deposits in a mid-latitude rift lake... 

Cohen, A. S., K.-E. Lezzar, I. J.Tiercelin M. Soreghan, 1997. New palaeogeographic and lake-level reconstructions of Lake Tanganyika implications for tectonic, climatic and biological evolution in a rift lake. Basin Res. 9 107-132. 

Rift lake Lake fonned in a basin produced by continental rifting. Typical modern examples are Lake Baikal and most of the large East African lakes. 

T. Chemet, Y. Trafi, V. Valles, Mechanism of degradation of the quality of natural water in the lakes region of the Ethiopian rift valley, Water Res. 35 (12) (2002) 2819-2832. 

In rift and/or volcanic regions and in recent mountain ranges such as the Caucasus, hydrothermal inputs may add significant quantities of dissolved material (Na, K, Cl, S04, Si02) to surface waters. The Semliki River, outlet of Lake Edward, is particularly enriched in (Table 3, F) the Tokaanu River (New Zealand) drains a hydrothermal field with record values of silica, Na and Cl (Table 3, F). 

Von Damm and Edmond (1984) utilized the lakes of the Ethiopian and northern Kenya rift zones to examine reverse weathering (the formation of authigenic clay minerals), because here evaporative concentration had not proceeded to the extent that salt precipitation interfered with a mass balance approach. They found that —60% of an alkalinity deficit could be accounted for by processes other than carbonate precipitation, and concluded that solute magnesium was lost as rapidly to clay as solute calcium was to carbonate. This situation, particularly in volcanic terrain, was also initially recognized at saline Lake Abert, Oregon, by Jones and VanDenburgh (1966). 

Areally close compositional contrast is seen in the recent rift area of Djibouti. On the western border, the terminal Lake Abhe is fed by the sodium-carbonate-type Awash River from the Ethiopian volcanic highlands, whereas the Asal Lake near an arm of the Gulf of Aden is fed by seawater through recent fault zones and hydrothermal inputs in addition to local runoff, and precipitates halite and gypsum (Fontes et al., 1979). 

Behr H.-J. (2002) Magadiite and magadi chert a critical analysis of the silica sediments in the Lake Magadi Basin, Kenya. In Sedimentation in Continental Rifts (eds. R. W. Renaut and G. M. Ashley). Society for Sedimentary Research (SEPM), Tulsa, pp. 257-273. 

Johnson T. C. (1996) Sedimentary processes and signals of past climatic change in the large lakes of the East African Rift Valley. In The Limnology, Climatology, and Paleoclimatol-ogy of the East African Lakes (eds. T. C. Johnson and E. O. Odada). Gordon and Breach, Amsterdam. 

Renaut R. W. and Tiercelin J. J. (1994) Lake Bogoria, Kenya Rift Valley—a sedimentological overview. In Sedimentology and Geochemistry of Modern and Ancient Saline Lakes (eds. R. W. Renaut and W. M. Last). SEPM (Society for Sedimentary Geology), Tulsa, pp. 101-123. 

The Mesoproterozoic Midcontinent Rift System, Lake Superior region, USA. Sedimentary Geology, 141-142, 421-442. 

When lakes form in large topographic depressions, such as rift valleys or wide glacial U-shaped valleys, their biogeochemical sediments are differentially eroded, forming hills with flat tops (Figure 9.4A, D). Erosion of lake sediments can also lead to relief inversions. For example, ephemeral lakes... 

Broadhurst CL, Cunnane SC, Crawford MA. Rift Valley lake fish and shellfish provided brain-specific nutrition for early Homo. Br J Nutr 1998 79( 1 ) 3—21. 

Both Lake Tiberias and the Dead Sea are located within one rift valley, striking approximately north-south, at a distance of about 100 miles from one another. The stratification of the water column and... 

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