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<br /> <br />Peter E. Barkmann <br /> <br /> BOOOl <br /> 7000 <br />--. <br />-l <br />en <br />:2 <br />!S 6000 <br />c <br />0 <br />:;:::; <br />('(l <br />> <br />CJ) 5000 <br />[jj <br /> 4000 <br />A <br /> <br />I:' <br /> <br />Aquifer Terminology <br /> <br />DAWSON <br />BUTTE <br />i~,.~~~o~~~r"~'J""'j'~ Denver A <br />. ~. ~ ,..,....... <br />~...~....\:..... ..oj. .. .. .. -', <br />'.. ......"'5''";.......-;::--.,.-::. ' <br />.......... ,. <br />........ .. <br /> <br /> <br /> BOOO <br />:::J 7000 <br />(/) Paleo501 <br />~ <br />=- 6000 <br />--- <br />c <br />0 <br />:;:::; <br />ell <br />> <br />~ 5000 <br />w <br /> 4000 <br />B <br /> <br /> <br />Figure 2. A. The principal aquifers of the Denver Basin aquifer system consist of interbedded sandstone, conglomerate and shale that have <br />been subdivided into four principal aquifers separated by specific shale beds identified in geophysical logs. B. Recent stratigraphic inter- <br />pretations of the Denver Basin subdivide the synorogenic sediments into two primary units, D1 and D2. Detailed analysis of geophysical <br />logs from hundreds of water wells further reveals great lateral variability in the sediments with coarser grains near the sediment source to <br />the west grading to finer-grained shaly sediments across the basin to the east. From Raynolds, 2002. <br /> <br />in the characteristics of the sediments filling the basin. <br />Generally, the coarser-grained sediments found closer to <br />the source on the west give way eastward across the Basin <br />to finer-grained, shale-dominated sediments (Raynolds, <br />2002). Figure 2B illustrates this horizontal variability. This <br />relationship is also apparent in net saturated sand and <br />transmissivity maps of the Basin (Topper et al., 2003). Fur- <br />thermore, detailed paleontological work combined with <br /> <br />mapping of well-developed soil horizons (paleosols) <br />within the sedimentary package in the years following the <br />statutory definition of the Denver Basin aquifers has led to <br />a new interpretation delineating the synorogenic sequence <br />into two primary sedimentary packages identified as the <br />Dl and D2 sequences (Raynolds, 2002). <br />Two critical characteristics influencing the hydrologic <br />behavior of the aquifer system are the relative proportion <br /> <br />The Rocky Mountain Association of Geologists <br /> <br />172 <br />