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8.1 MAJOR IONS ~.VD DISSOLVED SOLIDS <br />~f!e; .._ .. . <br />ty i <br />`_ <br />i .. _ `.: <br />Ground-water Quality Deteriorates from West to <br />East Across the Raton Basin <br />The water quality deteriorates as <br />ground water flows from sandstone, <br />conglomerate, and basalt in plateaus and <br />mesas to shale in stream valleys and plains. <br />From west to east across the Raton Basin, ground water gains <br />dissolved solids and changes from bicarbonate to sulfate and chloride <br />in composition (figs. 8.1-1 and 8.1-2). The regional chemical <br />e~ vlu-Flon of ground water is summarized in figure 8.1-3. <br />The Raton Basin is higher on the western side than on the <br />eastern side (fig. 8.1-2), and as ground water flows down this <br />topographic gradient, it gains dissolved solids by reaction with <br />bedrock. Geologic formations on the western side of the basin are <br />predominantly sandstone and conglomerate, which consist of minerals <br />like quartz,that resist reaction with ground water. Precipitation <br />and surface water that infiltrate these rocks and become ground <br />water are calcium bicarbonate solutions low in dissolved solids. <br />Since sandstone and conglomerate minerals do not react readily with <br />ground water, the ground water is little changed as it flows through <br />the rock. Geologic formations on the eastern side of the basin aze <br />predominantly shale, which is composed of clay ~==.~ minerals G~~:~~f5 <br /> <br />66 <br />