Montana Ground-Water Assessment Atlas No. 1, Part B, Map 4 October 1998 Revision 1 - Dec. 18, 1998 Montana Bureau of Mines and Geology A Department of Montana Tech of The University of Montana Thickness of the Fox HillsLower Hell Creek Aquifer, Lower Yellowstone River Area: Dawson, Fallon, Prairie, Richland, and Wibaux Counties, Montana by Larry N. Smith Note - this map was originally published at a scale of 1:250,000 but the page sizes have been modified to fit the size of the paper in your printer. A full sized 36 X 45 colored print of this map can be ordered from the Office of Publications and Sales of the Montana Bureau of Mines and Geology, 1300 West Park Street, Butte, MT 59701. Phone: 406-496-4167 E-mail: http://mbmgsun.mtech.edu Montana Bureau of Mines and Geology A Department of Montana Tech of The University of Montana Explanation > 0-100 feet 4 100-200 feet 200-300 feet 300-400 feet 400-500 feet Well location showing aquifer thickness in feet: 322 Water well log 270 Geophysical log Location of geophysical log examples 24N County boundary 50E Township boundary County seat 23N Major road Principal stream Area where the Pierre Shale is at or near the surface k e e r Outcrop area of the Fox Hills Formation C 22N r te wa ed R 3 53E Montana Ground-Water Assessment Atlas No. 1, Part B, Map 4 55E 56E October 1998 M i s Revision 1 - Dec. 18, 1998 52E 54E s 105o o Poplar u r H i a Dome r 51E d s c 57E r a 255 b b R C i l v 27N h a e 230 rl e ie r C 59E r 58E e e k 332 C r e 270 e 300 k o o 48 48 200 26N 295 230 268 26N 100 223 323 322 157 233 238 25N 25N 270 270 Eas t Re dwa te r 175 C reek 182 215 F ir st 243 283 H 24N a 200 y 218 C 275 282 276 re ek 279 277 270 272 287303 236 288 352 237 299 265 300 330 348 292 277 326 316 23N 288 217 295 304 Sun Beagle 357 367 Sidney 307 331 264 275 275 268 295 256 308 N 337 o 309 rt 300 h F 280 ork 300 22N Fox Cr eek Fox Cr ee k 250 267 No 387 rt h F ork 284 B 387 urn 3 00 21N RICHLAND Ground-Water Characterization Study Areas 400 412 NORTH DAKOTA M 20N ONTANA DAWSON PRAIRIE WIBAUX 294 19N 322 FALLON 18N SOUTH 266 Lower Yellowstone River Study Area DAKOTA 300 17N 106o 45E 47E 48E 49E 50E N 16N 432 46E 400 Scale 1:250,000 15N 300 0 5 10 15 miles 491 Transverse Mercator Projection o 268 B 47 ra Central Meridian -105 Degrees c 300 k 1927 Horizontal Datum C e ed t Thickness interval = 100 feet ar t 420 C r 14N C e 378 r e ee k k 400 389 ns 220 C r 21N e ek 394 276 383 Bur 290 300 ns 400 Cre T ek 293 268 h ir te en m 300 i 20N 245 le 300 234 212 C re e 226 k 310 211 292 331 313 19N S 383 mit h C ree 205 k 348 305 226 18N 300 U p p er S ev C en ottonw mil oo e Cree d 304 k Creek 382 237 17N 193 200 145 190 235 200 277 293 283 150 378 332 257 314 177 149 C 16N le ar Glendive C 400 140 400 re 153 ek K reek 300 rug C 200 G l e n d 15N 170 i 411 ve 159 Cree 100 k 427 o Wibaux 47 122 320 14N 140 k 389 232 400 345 Andrau 1-29 NPRR 400 herr C y C reek 13N 479 334 45E 46E 347 106o 299 47E 48E R i v e r 12N 300 Terry 400 e 301 n to s w o 463 11N l l e Y 49E P o w d e r 10N R i 289 v e r 50E 51E Andrau 1-29 NPRR T. 14 N. R. 51 E. Sec. 29 Spontaneous Resistivity Potential 75 400 - Thickness of the Fox HillsLower Hell Creek Aquifer, Lower Yellowstone River Area: Dawson, Fallon, Prairie, Richland, and Wibaux Counties, Montana 500 - Formation Fort Union by 600 - Larry N. Smith 60 200 60 C ed 300 ar C re ek 100 13N 400 391 Ca 100 bin C 200 r ee k 12N 403 O 448 Fa Cedar llo n C re 349 300 ek 371 400 100 314 11N 305 310 400 100 300 279 200 300 10N 55E 271 B ea 306 10N ver C re 400 ek 200 54E 262 418 300 52E 53E 9N 105o 9N 374 P enn el C re ek 55E mi San dsto ne C Sun / Beagle re e T. 23 N. R. 59 E. Sec. 17 431 k Creek Spontaneous Resistivity Potential 8N 385 8N 400 100 600 - 310 Formation Fort Union 195 Pi Baker 700 - ne C reek 7N 327 7N 800 - A 700 - Introduction aquifer to calculate the thickness, using geographic information of 50 feet. It is estimated that the accuracy of the map is system software. The contours were evaluated and then between 50 and 100 feet in most of the areas, but in some redrawn by hand to fit most of the 170 data points of thickness areas with fewer control points the accuracy may be reduced. This map illustrates the thickness of the Fox Hillslower and the outcrop areas of the Fox Hills Formation (Vuke-Foster 800 - Hell Creek aquifer in the Lower Yellowstone River Area. The et al. 1986; Colton et al. 1994; Wilde and Vuke 1994; top of the aquifer is at the top of a sandstone-dominated Bergantino and Wilde 1998a, b). Of the interpretations used sequence of sandstones (aquifer materials) and mudstones from geophysical logs, about 23% are from Feltis et al. (1981), Data Sources (non-aquifer materials) near the middle or base of the Hell 12% were reported by oil and gas companies, and the remaining Creek Formation (Figure 1, Smith and LaFave 1995). The were made for this study; a total of 9% of the data were from 900 - base of the aquifer is defined at the top of the Pierre Shale, water well logs. Contours fit most data points. Geographic features: which was picked from geophysical well logs at the uppermost Population center locations and roads are from 1:100,000- shale marker in the upper Pierre, below the sandstones or scale USGS digital line graph files available from the Natural siltstones of the overlying Fox Hills Formation (Smith 1995; Resources Information System (NRIS) at the Montana State 1000 - Smith and LaFave 1995). Sandstone beds in the Fox Hills Library, Helena, Montana. Hydrography has been simplified Formation are continuous across the study area, except where Map Use from the 1:100,000 digital line graph files. Township eroded near the Cedar Creek Anticline and the Poplar Dome. boundaries are from 1:250,000-scale USGS maps and are Hell Creek Formation aThis map can be used to estimate the thickness of the Fox available from NRIS. Geologic a a aThis report a Hydrologic Hillslower Hell Creek aquifer at locations where new wells 1100 - units: units: may be drilled or where older wells may be deepened. Most Point data: a aa a a a a Terrace a a Shallow hydrologic water wells in the area penetrate less than 50% of the aquifer Water well drillers logs, well locations, and water-quality a a a Alluviuma unit aaa a a a a aaa Fort Union Formation aathickness, so increased well productivity may be obtained by data are stored in the Ground-Water Information Center data aaa a a a a a Deep hydrologic a a a a base at Montana Bureau of Mines and Geology (MBMG). aaa a a deepening a well and increasing the open interval to the total a a a a unit 1200 - aaa a a thickness of the aquifer. Geophysical logs and interpreted tops are stored at MBMG; aaa a a a a a Confining bed aaa a a a a Hell Creek a a The aquifer is more than 450 feet thick in parts of Fallon, logs are also in the files of the Montana Board of Oil and Gas Formation a Fox Hills aaa a a Prairie, and Wibaux counties. Recent erosion near the Cedar Conservation in Billings, Montana. aaa a a a a a lower Fox Hills Hell Creek Formation aquifer Creek Anticline and the Poplar Dome and changes in thickness aaa a a 1300 - of sandstone units in the lower Hell Creek Formation and the Fox H Fox Hills Formation due to depositional and erosional patterns, Hell Cr About 11% of the water wells in the area are completed cause the aquifer to vary in thickness across the map. The References in the Fox Hillslower Hell Creek aquifer. Many wells yield coincidence of aquifer thinning along the Cedar Creek Anticline large volumes of water compared with wells completed in and Poplar Dome indicates that less sediment was preserved 1400 - the other bedrock aquifers in the area (aquifers in the Fort in these areas due to uplift on these structures relative to the Bergantino R. N. and Wilde, E. M. 1998a.