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Groundwater phreatic zone

Figure 2.1 Settings for calcrete development. In fluvial settings pedogenic calcretes can develop on floodplains and terraces, whereas groundwater calcretes may form in channel deposits or around the capillary fringe and upper part of the phreatic zone in more permeable parts of the floodplain. In alluvial fans paired calcretes may develop on the fans, with hydromorphic calcretes near discharge zones. Figure 2.1 Settings for calcrete development. In fluvial settings pedogenic calcretes can develop on floodplains and terraces, whereas groundwater calcretes may form in channel deposits or around the capillary fringe and upper part of the phreatic zone in more permeable parts of the floodplain. In alluvial fans paired calcretes may develop on the fans, with hydromorphic calcretes near discharge zones.
Aeolianites that become submerged below the groundwater table may become cemented in the phreatic environment. In this zone, pore spaces between sand grains are completely filled with water and any cements derived from the interstitial waters are often isopachous in nature (Muller, 1971). Large solution volumes and longer residence times in the phreatic zone can result in coarser spar compared with the vadose zone. Increases in temperature, degree of supersaturation and NaCl content appear to result in larger cement crystal sizes (Badiozamani et al., 1977). [Pg.151]

Ovoid and elongate concretions and type 1 tabular units appear to have formed principally in the phreatic zone, because they have poikilotopic and blocky spar cements, are associated with coarser, better sorted units, show preservation of original sedimentary structures, and are not associated with rhizocretions. In the Zia, preferential cementation of coarser, better sorted layers operates on the scale of both thin section and outcrop, something also noticed by Lynch (1996). Elongate concretions have been noted by other workers and attributed to groundwater flow in the phreatic zone (McBride et al., 1994, 1995 Mozley Davis, 1996). Orientations of these elongate concretions tend to be uniform within a single outcrop, often on the scale of several kilometres, as would be unexpected in vadose-zone cementation (Mozley Davis, 1996). [Pg.45]

Fig. 2.5 Basic components of a phreatic groundwater system intake outcrops, an aerated zone, the water table, the saturated zone that constitutes a water-bearing aquifer, and impermeable rock beds of the aquiclude that seal the aquifer at its base. Fig. 2.5 Basic components of a phreatic groundwater system intake outcrops, an aerated zone, the water table, the saturated zone that constitutes a water-bearing aquifer, and impermeable rock beds of the aquiclude that seal the aquifer at its base.
Figure 2.9 Characteristics of groundwater calcretes. (A) Generalised macroscopic features based on various sources. Some workers, such as Carlisle (1980), identify two zones in the massive phreatic unit an upper earthy zone with remnant soil and alluvium, and a lower, dense porcellaneous zone with abundant cracks and cavities. Phreatophytic plants may also produce features such as rhizocretions and laminar rhi-zolite crusts (Seminiukand Meagher, 1981). (B) Generalised model for the evolution of groundwaters and their precipitates in semi-arid to arid alluvial systems based on Arakel (1986). Figure 2.9 Characteristics of groundwater calcretes. (A) Generalised macroscopic features based on various sources. Some workers, such as Carlisle (1980), identify two zones in the massive phreatic unit an upper earthy zone with remnant soil and alluvium, and a lower, dense porcellaneous zone with abundant cracks and cavities. Phreatophytic plants may also produce features such as rhizocretions and laminar rhi-zolite crusts (Seminiukand Meagher, 1981). (B) Generalised model for the evolution of groundwaters and their precipitates in semi-arid to arid alluvial systems based on Arakel (1986).

See other pages where Groundwater phreatic zone is mentioned: [Pg.318]    [Pg.83]    [Pg.10]    [Pg.30]    [Pg.122]    [Pg.47]    [Pg.131]    [Pg.137]    [Pg.112]    [Pg.332]    [Pg.339]    [Pg.351]    [Pg.367]    [Pg.429]    [Pg.430]    [Pg.260]    [Pg.12]    [Pg.269]    [Pg.7]    [Pg.860]   
See also in sourсe #XX -- [ Pg.83 , Pg.117 ]




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Phreatic zone

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