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<br />002418 exclusively fine-grained marine shale and muddy limestone. As the amount of clays <br /> <br />increase with 1 <br /> <br />.distance from seawater. and GonseRtr.atieR ey organic matter Rave-increase~Q..the <br /> <br />concentrations of arsenic, chromium, copper, selenium, uranium, and other trace <br /> <br />minerals in the formations present in the watershed area. <br /> <br />Quaternary deposits overl~y the bedrock throuahoutElWf much of the watershed area. <br /> <br />These deposits generally consist of unconsolidated clay, silt, sand, gravel, and <br /> <br />sometimes cobbles and boulders. <br /> <br />Groundwater in the watershed is found in both confined and unconfined fwater table t <br /> <br />conditions. The youngest confined aquifer in the area is the Lower Cretaceous <br /> <br />Dakota sandstone, which is not exposed in the watershed. The flow in the Dakota <br /> <br />sandstone is toward the northeast and the recharge area of the Dakota formation is <br /> <br />the outcrop area to the southwest of the watershed. Activities and surficial <br /> <br />contamination sources in the watershed generally have little if any effect on water <br /> <br />quality in the confined aquifers. <br /> <br />Unconfined conditions in the watershed occur primarily in the alluvial and terrace <br /> <br />deposits along the Arkansas River and its tributaries. Groundwater flow in the <br /> <br />unconfined aquifer is generally toward the river. Recharge to the unconfined aquifer <br /> <br />is from precipitation, irrigation, and leakage from canals, ditches, and drains in the <br /> <br />watershed. It is this unconfined aquifer that is the most susceptible to contamination <br /> <br />from septic systems, feed lots, fertilizer, and pesticides. <br /> <br />'Check in reference section for geology reports for the area. <br />2.6. <br />2.6. <br />