| OBJECTID | DescriptionOfMapUnits_ID | Category | Type | Symbol | Label | MapUnit | Name | FullName | Age | AgeType | AgeOldest | AgeYoungest | Description | HierarchyKey | ParagraphStyle | AreaFillRGB | AreaFillPatternDescription | GeoMaterialDictID | GeoMaterial | GeoMaterialConfidence | Notes | DataSourceMethod | DescriptionSourceID | GlobalID |
|---|
| 65 | {D8666115-FFE4-4793-9C2D-E5940BA33B5F} | header | header, generic | None | None | None | SURFICIAL DEPOSITS | SURFICIAL DEPOSITS | None | None | None | None | None | 01 | dmu, header | None | None | None | None | None | None | 9 | DAS24 | {D8666115-FFE4-4793-9C2D-E5940BA33B5F} |
| 40 | {D347C355-F233-4630-B5FE-9E40C791716D} | map unit | map unit, generic | Qpa | Qpa | Qpa | paludal deposit | paludal deposit | Holocene | unprovided | Holocene | Holocene | Culbertson quadrangle: Brown, dark-gray, or black fine sand, silt, and clay in depressions that retain ephemeral ponds. Commonly includes thin laminae of windblown sand and silt. Depressions in the till plain and other areas are partially or completely filled with dark, tough, plastic, organic, silty or sandy clay containing scattered granules and pebbles. Most deposits are less than an acre in aerial extent; a few are larger than 2.6 sq km (1 sq mi); all have flat surfaces. Shallow ponds form in them during wet weather but disappear during dry weather. The deposits are well bedded to massive; beds generally are thin. Natural exposures in pond deposits do not exist, but auger holes revealed as much as 5 m (16 ft) of black or brown plastic, stiff clay, and scattered pebbles. Pond deposits are not indurated or cemented, and apparently do not contain concretions. Pond deposits are as thick as 5 m (16 ft) thick, the average thickness is about 2 m (6 ft). Generally, the deposit is thickest near the center of the closed depression. The cross section of most deposits resembles that of a shallow bowl. DAS36. Glasgow and Opheim quadrangles: Dark-gray plastic clay, silt, and sandy clay. Size distribution: 50 percent clay, 40 percent silt, and 8 percent sand. Thickness as much as 4 m (13 ft). DAS15 and DAS37. Scobey quadrangle: Brown, dark-gray, or black fine sand, silt, and clay in depressions that retain ephemeral ponds. Commonly includes thin laminae of windblown sand and silt. Depressions in the till plain and other areas are partially or completely filled with dark, tough, plastic, organic, silty or sandy clay containing scattered granules and pebbles. Shallow ponds form in them during wet weather but disappear during dry weather. A sample was composed of 68 percent clay, 26 percent silt, and 6 percent sand. The organic content is high, about 7 percent of a sample was consumed during an ignition test. The deposits are well-bedded to massive; beds generally are thin. Auger holes revealed as much as 5 m (16 ft) of black or brown plastic, stiff clay, and some scattered pebbles. Not indurated or cemented. As much as 5 m (16 ft) thick, but the average thickness is only about 2 m (6 ft). Generally, the deposit is thickest near the center, where the closed depression is deepest. The cross section of most deposits resembles that of a shallow bowl. [Slightly abridged from DAS33]. Plentywood quadrangle: Brown, dark-gray, or black fine sand, silt, and clay in depressions that retain ephemeral ponds. Commonly includes thin laminae of windblown sand and silt. Hundreds of closed depressions in the till plain and other areas are partially or completely filled with dark, tough, plastic, organic, silty or sandy clay containing scattered granules and pebbles. Only the larger ones are shown on the map. Most deposits are less than an acre in areal extent; a few are larger than 2.6 sq km (1 sq mi); all have relatively flat surfaces. Shallow ponds form in them during wet weather but disappear during dry weather. Mechanical analyses were made of two samples of pond deposits. About 50 percent of the samples consisted of clay, 42 percent was silt, and 8 percent was sand. The two samples had liquid limits of 46 and 76 and plastic limits of 36 and 38. The plastic indices were 10 and 38. Specific gravity was 2.50 and 2.62. The deposits are well bedded to massive; beds generally are thin. Natural exposures in pond deposits do not exist, but auger holes revealed as much as 5 m (16 ft) of black or brown plastic, stiff clay, and some scattered pebbles. Pond deposits are not indurated or cemented. Pond deposits are as much as 5 m (16 ft) thick, but the average thickness is only about 2 m (6 ft). Generally, the deposit is thickest near the center, where the closed depression is deepest. The cross section of most deposits resembles that of a shallow bowl. [Abridged from DAS35]. Wolf Point quadrangle: Brown, dark-gray, or black fine sand, silt, and clay in ice-block or deflation depressions that retain ephemeral ponds. As revealed by auger holes, most depressio | 01-01 | dmu, map unit | 255,227,60 | None | {35DC81C5-0B94-4280-A0D7-F4E65BB9CC45} | Clastic sediment | high | None | 5 | DAS36 | DAS15 | DAS37 | DAS33 | DAS35 | DAS34 | DAS13 | {D347C355-F233-4630-B5FE-9E40C791716D} |
| 38 | {43E65C1D-48BE-4EE9-9893-934A5C48D1C5} | map unit | map unit, generic | Ql | Ql | Ql | lacustrine deposit | lacustrine deposit | Holocene | unprovided | Holocene | Holocene | Pale yellow, grayish yellow, bluish green, yellowish brown, olive brown, grayish brown, brown, olive, yellowish gray, brownish gray, olive gray, bluish gray, gray, olive black, bluish black, black, or mottled, calcareous clay and silt. Generally stratified; well sorted; massive or weakly bedded. Commonly laminated, locally varved, clay and silty clay in lower part and massive or horizontally bedded silty clay and silt in upper part. Upper part generally is clast free. Thickness 3-16 ft (1-5 m), locally > 50 ft (15 m). | 01-02 | dmu, map unit | 220,239,59 | None | {1F5343B9-92D0-4717-BE09-18D334AA8173} | Lacustrine sediment | high | None | 5 | DAS13 | {43E65C1D-48BE-4EE9-9893-934A5C48D1C5} |
| 39 | {E6226A9D-72C6-4134-8BBD-B29DE4980496} | map unit | map unit, generic | Qls | Qls | Qls | landslide deposit | landslide deposit | Holocene | unprovided | Holocene | Holocene | Glasgow and Opheim quadrangles: Large slump blocks of various formations. Thickness as much as 20 m (66 ft). DAS15. Plentywood quadrangle: Large slump blocks of Fort Union Formation and till. Many small deposits have not been shown. Composition is that of the parent material affected by landsliding. Thickness is variable but may be as much as 10 m (33 ft). Sizes of particles range from clay to blocks of sandstone a few meters in diameter. DAS35.Culbertson, Scobey and Wolf Point quadrangles: Slump, rockfall, and earthflow deposits (individual or in series) produced by gravity downslope movement of bedrock or surficial materials. Colors, textures, and lithologies vary, reflecting parent material. Size of detritus ranges from clay to blocks of sandstone and clinker as large as 3 m (10 ft) in diameter. Thicknesses of some landslide deposits are estimated to be as much as 30 m (100 ft). DAS36. Western quadrangles: Slump-block landslide deposits and rockslide deposits. Slump-block landslide deposits: Masses of bedrock and unconcolidated materials that rotated or slid downslope as a unit, with little or no flow. The physical properties of the transported materials are not greatly altered; original textures, stratification, bedding, and other sedimentary structures of slumped materials are disturbed, but retained. Bearpaw and Claggett Formations are especially prone to slump. Rockslide deposits: Clasts are granules to slabs and blocks; some blocks are >3 m in diameter; some deposits are jumbled blocks. Thickness 10-16 ft (3-5 m), locally > 50 ft (10 m). DAS21. | 01-03 | dmu, map unit | 234,234,89 | None | {017338DF-E8E0-4EE7-BAED-C9EBC828F436} | Debris flows, landslides, and other localized mass-movement sediment | high | None | 5 | DAS15 | DAS35 | DAS36 | DAS21 | {E6226A9D-72C6-4134-8BBD-B29DE4980496} |
| 27 | {FD74C742-E446-4B52-A498-FDBCF8038BB3} | map unit | map unit, generic | Qal | Qal | Qal | alluvium | alluvium | Holocene | unprovided | Holocene | Holocene | Culbertson quadrangle: Light-yellowish-brown, yellowish-brown, grayish-brown, and light-gray coarse to fine gravel, sand, silt, and clay deposited on floodplains and in stream channels. Poorly- to well-stratified; poorly- to well sorted. Most of the alluvium is yellowish brown and moderate brown; most of the clay plugs are yellowish brown, medium gray, or bluish gray. The upper several feet contain lenticular dark-brown or dark-gray beds alternating with light brown beds. Light-brown iron staining occurs as isolated blebs along rootlets and irregularly through some beds, staining individual laminae. Staining is prominent in some areas. Floodplain alluvium is chiefly unconsolidated, well-sorted, silt and fine and medium sand; in valleys of some small streams, it includes fine to coarse gravel. Silt and organic clay generally are present in discontinuous lenses or beds or are mixed with fine sand. In general, the upper part of the floodplain alluvium consists of unconsolidated, well-sorted very fine sand, silt, and clay, whereas the lower part (channel alluvium, and locally, outwash) consists of coarse sand and gravel. Vertical and horizontal facies changes within short distances are common. Grain size analyses of alluvium indicate great variation of texture: 28-58 percent clay, 5-60 percent silt, 4-100 percent sand, 0-14 percent granules, and 0-53 percent pebbles. Seventeen test holes were drilled by the Bureau of Reclamation in the Ft. Kipp 7.5-minute quadrangle in sec. 6, T. 28 N., R. 55 E., and sec. 1, T. 28 N., R. 54 E. across the valley of Big Muddy Creek. The profile indicates that the center of the valley is underlain by 95 ft of clay, which is underlain by 12.2 m (40 ft) of clay, silt and sand; that rests on 6 m (20 ft) of sand and gravel (outwash?) which lies on bedrock. Five test holes were drilled southwest of the alluvial plain and indicate that there are two tills, each as much as 80 ft thick, on as much as 53 m (175 ft) of sand and gravel. The axis of an older buried valley is just south of the edge of the present alluvial plain of Big Muddy Creek. [Abridged from DAS 36]. Glasgow and Opheim quadrangles: Light yellowish gray to medium brown clay, silt, sand, and fine gravel; vertical and horizontal variations in composition and in bedding. Upper part finer grained than lower part. Thickness as much as 42 m (164 ft) under floodplain of Missouri and Milk Rivers, but generally only 5-8 m (16-26 ft) under floodplains of tributaries. DAS15 Plentywood quadrangle: Light-yellowish-brown, yellowish-brown, grayish-brown, and light-gray coarse to fine gravel, sand, silt, and clay deposited on floodplains and in stream channels. Poorly to well stratified, and poorly to well sorted. Underlain by glacial outwash, especially under the floodplain of Big Muddy Creek. Most of the alluvium is yellowish brown and moderate brown; most of the clay plugs are yellowish brown, medium gray, or bluish gray. The upper several feet of the alluvium commonly contain lenticular dark-brown or dark-gray beds alternating with light brown beds. Light-brown iron staining occurs as isolated blebs along rootlets and irregularly through some beds, staining individual laminae. Iron staining is prominent in some areas. Floodplain alluvium deposited by Big Muddy Creek underlies about 100 square km (65 square mi) of the quadrangle. The alluvium is composed mostly of thin beds of fine sand, silt, and clay, and is rich in organic matter. Moist alluvium is generally light yellowish gray (5Y 7/2) to medium brown (5YR ¾), but many beds are tan; most of the moist clay beds are gray. Dry alluvium is commonly gray. The upper several feet contain a few dark-brown or black beds alternating with light grayish brown. Beds range from less than 1 inch to 2 feet in thickness. Bedding is virtually horizontal with little conspicuous channeling. Some irregularities in bedding are due to irregularities in the surface of deposition. Individual channels in some cutbanks are a few feet deep and 10 to 15 feet wide. Shells of fresh-water clams (Anodonta) occur in the alluviu | 01-04 | dmu, map unit | 255,255,214 | None | {0447A5CB-B7E3-4C67-B8DF-F6C9329CD6FF} | Alluvial sediment | high | None | 5 | DAS36 | DAS15 | DAS35 | DAS33 | DAS34 | DAS13 | {FD74C742-E446-4B52-A498-FDBCF8038BB3} |
| 29 | {1E54CA21-6809-4913-8F52-963EA6391717} | map unit | map unit, generic | Qc | Qc | Qc | colluvium | colluvium | Holocene | unprovided | Holocene | Holocene | Unconsolidated, angular poorly sorted clasts derived from upslope rock exposures. Maximum thickness generally about 15 ft (5m). | 01-05 | dmu, map unit | 244,232,0 | None | {6C2D6A29-29B2-4583-B4D5-D7B0A66B031F} | Colluvium and other widespread mass-movement sediment | high | None | 5 | DAS20 | {1E54CA21-6809-4913-8F52-963EA6391717} |
| 25 | {76AEB8E0-11D7-46B1-AEA0-1494317C7724} | map unit | map unit, generic | Qac | Qac | Qac | alluvium and colluvium | alluvium and colluvium | Holocene | unprovided | Holocene | Holocene | Glasgow and Opheim quadrangles: Slopewash and creep deposits along valley walls. Composition and color reflect that of parent material. Deposits are gently sloping, poorly sorted, and poorly stratified. Composed of silty clay, sandy silt, pebbly clay, pebbly silt, gravelly clays, and gravel. Composition is variable but size analyses indicate 43 percent clay, 42 percent silt, and 15 percent sand. Includes small alluvial fans. Thickness as much as 6 m (20 ft), but thins to feather edge upslope and downslope. DAS15 and DAS17. Culbertson and Plentywood quadrangles: Light-brown, brown, grayish-brown, and gray nonstratified or poorly stratified gravel, sand, silt, and clay deposited by sheet wash, stream flow, and gravity processes on slopes. Primarily sheetwash alluvium, derived from bedrock outcrops and other surficial deposits higher on slopes and deposited by unconfined sheet flow and rill wash. Colluvium is generally present only on and below slopes steeper than 8 percent. Sheetwash alluvium is chiefly fine sand and silt with scattered granules and small pebbles; colluvium is chiefly gravel and sand or a heterogeneous mixture of boulders, cobbles, pebbles, and granules in a clayey to sandy matrix. Colors, textures, and particle lithologies vary, reflecting those of the parent bedrock and surficial materials higher on slopes. The downslope surface profile of alluvial/colluvial deposits is concave upward. Sheetwash alluvium commonly interfingers with and overlaps flood-plain alluvium (Qal), and it forms fans and aprons on terraces in major valleys. Buried soils (humic horizons) are present locally in the sheetwash alluvium and colluvium; fossil snail shells and vertebrate fossils are present locally. Unit includes small areas of windblown deposits (Qe) that interfinger with and overlie sheetwash alluvium. The composition and color of the alluvial fan and colluvial deposit vary considerably depending on the lithologies of the source bedrock and surficial materials. Composition is variable but averages 43 percent clay, 42 percent silt, and 15 percent sand. Great variation in thickness within short distances is characteristic of fan alluvium and colluvium. Generally, the thickness of colluvium is less than 3 m (10 ft), seldom more than 2 m (6 ft), and averages only 0.3 m (1 ft). The thickness of alluvial fans ranges from zero at the apex and reaches a maximum about one-third or one-fourth of the distance to the toe. At the toe, the fan alluvium is thin and commonly interfingers with the adjacent floodplain alluvium. Fans are as much as 15 m (50 ft) thick but average 3 m (10 ft) and seldom exceed 8 m (25 ft) thick. Generally, the deposits have not been mapped where they are less than 0.3 m (1 ft) thick. DAS36 and DAS35 Scobey and Wolf Point quadrangles: Light brown, brown, grayish brown, and gray non-stratified or poorly stratified gravel, sand, silt, and clay deposited by sheet wash, stream flow, and gravity processes on slopes. Primarily sheetwash alluvium, derived from bedrock outcrops and other surficial deposits higher on slopes and deposited by unconfined sheet flow and rill wash. Colluvium is generally present only on and below slopes steeper than 8 percent. Sheetwash alluvium is chiefly fine sand and silt with scattered granules and small pebbles; colluvium is chiefly gravel and sand or a heterogeneous mixture of boulders, cobbles, pebbles, and granules in a clayey to sandy matrix. Colors, textures, and particle lithologies vary, reflecting those of the parent bedrock and surficial materials higher on slopes. Sheetwash alluvium commonly interfingers with and overlaps flood-plain alluvium (Qal), and it forms fans and aprons on terraces in major valleys. Buried soils (humic horizons) are present locally in the sheetwash alluvium and colluvium; fossil snail shells and vertebrate fossils are present locally. Unit includes small areas of windblown deposits (Qe) that interfinger with and overlie sheetwash alluvium. Generally, the thickness of colluvium is less than 3 m (10 ft), seldom more than 2 m (6 ft), and averages only 0 | 01-06 | dmu, map unit | 239,239,135 | None | {76B03527-703E-4EFC-9E22-9D3C58158F5D} | Sediment | high | None | 5 | DAS36 | DAS15 | DAS37 | DAS35 | DAS33 | DAS34 | DAS13 | {76AEB8E0-11D7-46B1-AEA0-1494317C7724} |
| 30 | {3FE07CC4-994E-494C-96E7-1463BB3032E8} | map unit | map unit, generic | Qe | Qe | Qe | eolian deposit | eolian deposit | Holocene | unprovided | Holocene | Holocene | Culbertson quadrangle: Light-brown to light-gray windblown silt (loess) and sand with some granules. Generally massive or crossbedded; quartz grains are commonly frosted. Buried soils (humic horizons) are present locally. Most of the sand grains are well-rounded quartz coated with organic matter; locally the grains are clean angular quartz. The deposits of windblown sand and silt unconformably overlie all other map units in the area. Four analyses of dune sand indicate that the dunes consist of 0-6 percent clay, 1-9 percent silt, and 85-99 percent sand. Two samples of loess indicate it consists of 10-20 percent clay, about 60 percent silt, and 20-30 percent sand. Local relief in the sand dunes a few miles south of Johnson Lake and southeast of Medicine Lake is as much as 15 m (45 ft); therefore, the maximum thickness of eolium is probably approximately 17 m (57 ft). In interdune areas, the thickness is probably only a few meters. Generally, the thickness is 5 to 6 m. Parabolic dunes indicate winds from the northwest moved the sand southeastward from outwash deposits that are now buried under the floodplain of Big Muddy Creek. DAS 36. Glasgow and Opheim quadrangles: Light to dark brown, medium- to fine-grained, windblown silt and sand. Consists of 5 percent clay, 7 percent silt, and 88 percent sand. Thickness as much as 6 m (20 ft) in dunes, but generally less than 2 m (6 ft). DAS 15 and DAS 37. Plentywood quadrangle: Light-brown to light-gray windblown silt (loess) and sand with some granules. Generally massive or crossbedded; quartz grains are commonly frosted. Buried soils (humic horizons) are present locally. Most of the sand grains are well-rounded quartz coated with organic matter; locally the grains are clean angular quartz. The deposits of windblown sand and silt unconformably overlie all other map units in the area. A veneer of eolian deposits, generally 1 m (3 ft) thick, but locally m (13 ft) thick, is present on most flat or nearly flat surfaces throughout the quadrangle. Deposits of windblown sand were mapped in two small areas in the western part of sec. 11, T. 32 N., R. 55 E. A mantle of eolian silt too thin to map covers large parts of the quadrangle. The sand dunes are the result of wind action. Other eolian deposits have formed along fences where piles of tumbleweeds have trapped sand and silt blowing off fields. Dune sand is composed of medium- to fine-grained sand and less than 10 percent silt; it is noncohesive. The color ranges from light tan to brown. The organic content is low but there are some humified layers. Fine sand and silt of windblown origin is similar to the dune sand but does not have the typical dune form. It forms a thin silty veneer overlying glacial till. The sand is dark brown owing to organic coatings on individual grains. No fossils have been found in the dune sands and other eolian deposits. The sand has A sample of eolian sand was collected from the NW ¼ NE ¼ SW ¼ sec. 1, T. 32 N., R. 55 E., and from NW ¼ SE ¼ NW ¼ sec. 11, T. 33 N., R. 55 E. The results were nearly identical and showed that about 5 percent was clay sized, 7 percent was silt sized, and 88 percent was sand sized. The specific gravity of these two samples was 2.64. The coefficients of sorting were 1.31 and 1.86, respectively. DAS 35. Scobey quadrangle: Light brown to light gray windblown silt (loess) and sand with some granules. Generally massive or cross-bedded; quartz grains are commonly frosted. Buried soils (humic horizons) are present locally. Most of the sand grains are well-rounded quartz coated with organic matter; locally the grains are clean angular quartz. The deposits of windblown sand and silt unconformably overlie all other map units in the area. The deposits are not all of the same age; for example, some of those on the driftless parts of the Flaxville plateau may be as old as early Pleistocene but most of the windblown sand and silt in the driftless areas is probably late Pleistocene or Holocene in age. Three analyses of eolian deposits indicate that it consists of 7-30 percent clay, 10-38 percent | 01-07 | dmu, map unit | 242,237,0 | None | {F498A054-CE7D-4202-A334-54F1810CE137} | Eolian sediment | high | None | 5 | DAS36 | DAS15 | DAS37 | DAS35 | DAS33 | DAS34 | DAS13 | {3FE07CC4-994E-494C-96E7-1463BB3032E8} |
| 26 | {B68D660A-813A-4918-95B4-EE65B74D281B} | map unit | map unit, generic | Qaf | Qaf | Qaf | alluvial fan deposit | alluvial fan deposit | Holocene and Pleistocene | unprovided | Pleistocene | Holocene | Yellowish brown, grayish brown, yellowish gray, brownish gray, gray, or mottled clay, silt, sand, and gravel. Poorly to well stratified; poorly to well sorted. Poorly sorted gravel and pebbly sand near fan apex, grading to pebbly silt and clay near toe. Clasts are subangular to well rounded. Includes some sheetwash alluvium and flood-plain and channel alluvium. Small alluvial fan deposits are included in other map units. Thickness typically 2 to 33 ft (0.5-10 m); maximum thickness > 33 ft (10 m). | 01-08 | dmu, map unit | 247,237,96 | None | {0447A5CB-B7E3-4C67-B8DF-F6C9329CD6FF} | Alluvial sediment | medium | None | 5 | DAS13 | {B68D660A-813A-4918-95B4-EE65B74D281B} |
| 35 | {AC2C90C5-0F20-44A3-A64E-17863057A5F0} | map unit | map unit, generic | Qgr | Qgr | Qgr | gravel deposit | gravel deposit | Holocene and late Pleistocene | unprovided | Pleistocene | Holocene | Scobey quadrangle: Light-yellowish brown, yellowish brown, grayish brown, and light gray coarse to fine gravel, sand, silt and clay deposited by streams. Deposits are poorly to well-stratified, and poorly to well-sorted. Deposits are 5 to 10 m (15 to 30 ft) above adjacent alluvial deposits. Thickness ranges from 2 to 3 m (6 to 10 ft). DAS33. Western quadrangles: Well to poorly sorted and stratified deposits of silt, sand, and gravel. Most are light brown. Thickness typically 10-13 ft (3-4 m), but as much as 33 ft (10 m). DAS21 | 01-09 | dmu, map unit | 242,230,82 | None | {1EA7E66A-155C-44AA-9F48-2FC62780A963} | Sand and gravel of unspecified origin | high | None | 5 | DAS33 | DAS21 | {AC2C90C5-0F20-44A3-A64E-17863057A5F0} |
| 41 | {6D9C6886-5EF3-43D6-8DDE-91AAC7B826C1} | map unit | map unit, generic | Qsg | Qsg | Qsg | sand and gravel deposit | sand and gravel deposit | Holocene and late Pleistocene | unprovided | Pleistocene | Holocene | Primarily based on parent material for USDA Turner and Beaverton soil series. Turner series: Very deep, well drained soils that formed in alluvium and have very gravelly loamy coarse sand at a depth of 20 to 40 inches. These soils are on alluvial fans, stream terraces, and relict stream terraces. Slopes are 0 to 15 percent. Beaverton soil series: Very deep, well drained soils that formed in gravelly alluvium or glacial outwash materials. These soils have extremely gravelly sand at a depth of 10 to 20 inches. These soils are on alluvial fans, stream terraces, hills, and outwash plains. Slopes are 0 to 25 percent. Primarily represents reworked Flaxville and glacial deposits. | 01-10 | dmu, map unit | -25,-25,-25 | None | {1EA7E66A-155C-44AA-9F48-2FC62780A963} | Sand and gravel of unspecified origin | high | None | 5 | DAS44 | DAS45 | DAS46 | {6D9C6886-5EF3-43D6-8DDE-91AAC7B826C1} |
| 28 | {F921EA3F-8FC2-4D3D-8B67-13FAC013D8EF} | map unit | map unit, generic | Qalo | Qalo | Qalo | alluvium, older than Qal | alluvium, older than Qal | Holocene or Pleistocene | unprovided | Holocene | Pleistocene | Glasgow quadrangle: Well to poorly sorted and stratified deposits of silt, sand, and gravel. Most are light brown. Thickness as much as 10 m (33 ft) but generally only 3 or 4 m (10-13 ft) thick. Opheim quadrangle: Light brown, light to dark gray clay, silt, sand and sandy gravel. Upper 5-6 m (15-20 ft) consists of fine-grained overbank deposits. Underlain by sand and fine gravel and becomes coarser downward to gravel containing clasts as much as 50 cm (2 in) in diameter. Thickness under floodplains of Missouri and Milk Rivers is as much as 60 m (180 ft) but averages only 30 m (99 ft). Thickness under floodplains of tributary streams is only 5-10 m (16-33 ft.) DAS15 Scobey quadrangle: Light-yellowish brown, yellowish brown, grayish brown, and light gray coarse to fine gravel, sand, silt and clay deposited by streams. Deposits are poorly to well-stratified, and poorly to well-sorted. Deposits are 5 to 10 m (15 to 30 ft) above adjacent alluvial deposits. Thickness ranges from 2 to 3 m (6 to 10 ft). DAS33. Western quadrangles: Channel alluvium: Chiefly loose, stratified, poorly sorted to well sorted, pebbly, fine to medium sand and/or coarse sand and gravel; locally very poorly sorted sandy shale gravel. Cobbles and boulders are common to abundant in some areas. Generally cross-bedded or has crude horizonatal bedding or lenticular bedding. Overlying flood-plain alluvium: Chiefly poorly sorted to well sorted clay, silt, and sand, with scattered granules and pebbles. Moderately to well stratified. Local thin buried soils. Thickness as much as 65 ft (20 m). DAS13. | 01-11 | dmu, map unit | 237,237,167 | None | {0447A5CB-B7E3-4C67-B8DF-F6C9329CD6FF} | Alluvial sediment | high | None | 5 | DAS15 | DAS33 | DAS13 | {F921EA3F-8FC2-4D3D-8B67-13FAC013D8EF} |
| 33 | {E7C34E1F-3084-44DA-BDC0-5F0092B36165} | map unit | map unit, generic | Qgle | Qgle | Qgle | glacial lake and eolian deposits | glacial lake and eolian deposits | Holocene and late Pleistocene | unprovided | Pleistocene | Holocene | Complex map unit of lake sand and silt, and eolian sand and silt. Lake deposits in many places were reworked by wind and are overlain by eolian deposits. Eolian deposits: Yellow, yellowish brown, olive brown, grayish brown, brown, brownish gray, gray, or mottled windblown sand and silt in blanket-like deposits and local low dunes. Calcareous. Well stratified; poorly sorted to well sorted. Typically loose, homogeneous, massive, fine sand and silt with faint beds or crossbeds. Very friable, weakly compact; slightly hard; not sticky or plastic when moist. Generally clast free. Thickness 1.5-10 ft ( 0.5-3 m); maximum 20 ft (6 m). Lake deposits: Grayish yellow, yellowish brown, grayish brown, brown, yellowish gray, olive gray, brownish gray, gray, or mottled, calcareous silt and sand mixed with minor clay and gravel. Generally well stratified and well sorted. Typically horizontally bedded or massive, fine or medium sand containing scattered granules or small pebbles. Commonly interbedded or intercalated with massive, bedded or laminataed silt containing dropstones. Commonly slumped and contorted on hillslopes. Detrital fragments of bedrock lignite are abundant in many areas, concentrated in sand crossbeds. Thickness 3-26 ft (1-8 m), locally > 33 ft (10 m). | 01-12 | dmu, map unit | 255,255,153 | None | {1F5343B9-92D0-4717-BE09-18D334AA8173} | Lacustrine sediment | medium | None | 5 | DAS13 | {E7C34E1F-3084-44DA-BDC0-5F0092B36165} |
| 34 | {0BAD6F73-F758-4E0C-BBEA-83C4A6AD3D72} | map unit | map unit, generic | Qgo | Qgo | Qgo | glacial outwash deposit | glacial outwash deposit | Pleistocene | unprovided | Pleistocene | Pleistocene | Culbertson quadrangle: Light-brown, yellowish-brown, brown, and light-gray sand and gravel with minor silt, deposited by glacial meltwater streams. Generally horizontally bedded and well stratified; moderately well sorted to well sorted. Granules and larger clasts are subrounded to well rounded. Clast lithology consists of reworked erratic glacial pebbles, cobbles, and boulders of limestone, dolomite, granite, gneiss, and schist from Canada. Outwash deposits typically consist of 2-18 percent clay, 2-8 percent silt, 20-27 percent sand, 4-20 percent granules, 42-73 percent pebbles, and 2-5 percent cobbles. Most of the outwash deposits are thin, long, narrow sandy gravel fills in ice-marginal channels that formed between the ice margin and the higher ground, or beneath the ice margin. Most outwash deposits are less than 1.6 km (1 mi) long, but a few are as much as 8 km (5 mi) long; generally, they are less than 30 m (100 ft) wide, but some irregularly shaped outwash deposits are a mile wide. The lower parts of some alluvial deposits may be outwash. Locally, some of the outwash deposits may be deltaic. In places, outwash may be overlain by a thin discontinuous veneer of till (Qgt), glacial lake deposits (Qgl), and sheetwash alluvium (Qac). Those that formed during each advance were overridden and veneered by till and/or glaciolacustrine deposits. Most of the outwash deposits are about 3 m (10 ft) thick but some are as much as 6 m (20 ft) thick.[Slightly abridged from DAS36]. Glasgow and Opheim quadrangles: Poorly to well sorted sandy gravel interbedded with clay, silt, and well sorted sand. Contains numerous glacial erratics. Diameter of rounded clasts in gravel as much as 10 cm (4 in) but averages 1.5 cm (0.43 in). Composition varies but averages 6 percent silt, 44 percent sand, 10 percent granules, and 40 percent pebbles. Lithology is approximately 5 percent quartzite, 25 percent limestone and dolomite, and 9 percent granite. Thickness as much as 5 m (16 ft); most deposits are only 6-15 m (20-50 ft). DAS15. Plentywood quadrangle: Light-brown, yellowish-brown, brown, and light-gray sand and gravel with minor silt, deposited by glacial meltwater streams. Generally horizontally bedded, well stratified and moderately well sorted. Granules and larger clasts are subrounded to well rounded. Clast lithology in most places is similar to that of the Flaxville Formation, but reworked erratic glacial pebbles, cobbles, and boulders of limestone, dolomite, granite, gneiss, and schist from Canada are conspicuous. Outwash deposits typically consist of 2-18 percent clay, 2-8 percent silt, 20-27 percent sand, 4-20 percent granules, 42-73 percent pebbles, and 2-5 percent cobbles. Lithology is approximately 55 percent quartzite, 25 percent limestone and dolomite, and 9 percent granite. Thickness is as much as 52 m (171 ft); however, most deposits are 6 to 15 m (19.6 ft to 49 ft) thick. The lithology of the outwash deposits that cover the Flaxville formation cannot be distinguished easily from the underlying gravel from which they were largely derived. Scattered outwash gravel deposits along Big Muddy Creek are exposed in several pits near the town of Plentywood. These gravel deposits are extensive and have been traced up where the border of the Medicine Lake readvance crosses the old abandoned valley of Big Muddy Creek. The thickness of the outwash deposits in Big Muddy Valley ranges from 0 to an inferred 135 feet. A thickness of more than 20 feet was observed in many places. Drilling for seismic shot holes a few miles west of Plentywood indicated that a thickness of 70 to 120 feet is common. [Abridged from DAS35]. Scobey and Wolf Point quadrangles: Light-brown, yellowish-brown, brown, and light-gray sand and gravel with minor silt, deposited by glacial meltwater streams. Generally horizontally bedded, well stratified and moderately well sorted. Granules and larger clasts are subrounded to well rounded. Clast lithology in most places is similar to that of the Flaxville Formation, but reworked erratic glacial pebbles, cobbles, and boulders of | 01-13 | dmu, map unit | 250,236,4 | None | {F2EBB19F-A973-4D08-880A-67F9FA280BBC} | Glacial till | low | None | 5 | DAS36 | DAS15 | DAS35 | DAS33 | DAS13 | {0BAD6F73-F758-4E0C-BBEA-83C4A6AD3D72} |
| 37 | {530EA720-7A95-4DFC-86E9-B24DD7C2F9F6} | map unit | map unit, generic | Qki | Qki | Qki | Kintyre Formation | Kintyre Formation | Pleistocene | unprovided | Pleistocene | Pleistocene | Culbertson quadrangle: Brown, olive-brown, light-brown, light-gray sand, sandy silt, clayey silt, and clay. Consists of a basal clay, overlain by light-brown silt, fine sand interbedded with minor amounts of clay and silty clay. The upper half of the formation is dark-brown clay and silty clay. The sediments were originally deposited on glacial ice, partly by slowly flowing glacial meltwater and partly as lacustrine deposits laid down in shallow ponds and lakes on the melting ice. The silts and clays in ponded waters are thinly laminated, whereas the deposits laid down by flowing water are somewhat coarser. As the underlying ice melted, the clay, silt, and sand deposits collapsed and were folded and fractured. Thickness of the formation is as much as 21 m (70 ft) but generally ranges from 6 m (20 ft) to 21 m (70 ft). [Abridged from DAS36]. Glasgow quadrangle: Olive brown clay, fine-grained sand, sandy silt, clayey silt, clay, medium- to coarse-grained sand, and minor gravel lanses. Lower half is light brown silt and very fine-grained sand interbedded with minor amounts of clay and silty clay. Upper half is dark olive brown clay and silty clay. Beds were folded, broken, and contorted on a large scale as underlying ice melted. Thickness as much as 21 m (70 ft) but most deposits are only 6 m (20 ft) thick. DAS 15. Wolf Point quadrangle: Light-brown, olive-brown, brown, or light-gray sand, sandy silt, clayey silt, and clay. The lower half of the formation typically consists of basal clay overlain by silt and fine sand that is interbedded with minor clay and silty clay. The upper half is clay and silty clay. Most of the sediment was probably deposited on stagnant glacial ice, partly by slowly flowing glacial meltwater streams and partly as lacustrine sedimentBrown, olive-brown, light-brown, light-gray sand, sandy silt, clayey silt, and clay. Consists of a basal clay, overlain by light-brown silt, fine sand interbedded with minor amounts of clay and silty clay. The upper half of the formation is dark-brown clay and silty clay. The sediments were originally deposited on glacial ice, partly by slowly flowing glacial meltwater and partly as lacustrine deposits laid down in shallow ponds and lakes on the melting ice. The silts and clays in ponded waters are thinly laminated, whereas the deposits laid down by flowing water are somewhat coarser. As the underlying ice melted, the clay, silt, and sand deposits collapsed and were folded and fractured. Thickness of the formation is as much as 21 m (70 ft) but generally ranges from 6 m (20 ft) to 21 m (70 ft). The Kintyre Formation overlies the youngest till in the quadrangle, and it was deposited during the last deglaciation. Three miles south of Wolf Point, the Kintyre Formation is 11 m (35 ft) thick. The log of a test hole drilled by the U.S. Bureau of Reclamation one mile east of the Wolf Point 30’ x 60’ quadrangle indicates a thickness of 37.2 m (122 ft). DAS 34. Western quadrangle: Fluviolacustrine sediments that were in large part deposited on stagnant ice in the old Missouri River trench. In most places the basal few feet consist of fissile olive-brown clay that is shale-like when dry. The overlying deposits are semiconsolidated interbedded fine-grained sands, sandy silts, clayey silts, and clay, and include some small areas and isolated small lenses of unconsolidated medium- to coarse-grained sand. Broadly speaking, the lower half of the beds overlying the basal clay consists predominantly of light-tan silt and very fine sand interbedded with minor amounts of clay and silty clay. The upper half consists predominantly of dark-brown clay and silty clay. Locally, the formation consists mostly of light-brown silt and silty very fine sand, and includes dark-brown clay at the base. The formation ranges from 0 to more than 70 feet (21 m) thick; in most areas of exposure the formation ranges from 20 to 70 feet (6 to 21 m) thick.DAS19. | 01-14 | dmu, map unit | 244,244,115 | None | {1F5343B9-92D0-4717-BE09-18D334AA8173} | Lacustrine sediment | medium | None | 5 | DAS36 | DAS15 | DAS34 | DAS19 | {530EA720-7A95-4DFC-86E9-B24DD7C2F9F6} |
| 31 | {303AA65F-15D3-462F-B74E-A238B368232B} | map unit | map unit, generic | Qgic | Qgic | Qgic | glacial ice-contact deposit | glacial ice-contact deposit | Pleistocene | unprovided | Pleistocene | Pleistocene | Culbertson quadrangle: Brown to light-brown poorly to well-stratified, poorly- to well-sorted, fine to coarse sand and gravel with minor silt. Deposited by glacial meltwater flowing in channels beneath, within, or on top of ice and, subsequently, let down as the supporting or surrounding ice melted. Deposits are long, discontinuous, narrow and sinuous (eskers), or conical heaps or irregular ridges (kames). Esker and kame deposits are poorly bedded and sorted. Local faults and tilted and contorted bedding in the deposits indicate collapse when the enclosing ice melted. Well-stratified silt, sand, or fine gravel beds commonly abut poorly sorted material, or, locally, lenses of till; crossbedding is pronounced in some beds in eskers and kames. Bedding along the sides of eskers tends to be parallel to the side slopes owing to collapse of the retaining ice walls. The few exposures seen in the area indicate till is the material underlying esker and kame deposits. Till is on the sides and crests of some eskers and kames, indicating they were formed in and under ice. Locally, esker and kame deposits are overlain by alluvium, colluvium, lake deposits, the Kintyre Formation, and eolian deposits. Esker and kame deposits occur together and in some places grade into each other. The dimensions of kames vary greatly. Their length ranges from 100 m (300 ft) to more than 1.6 km (1 mi), their height is as much as 30 m (100 ft), but few exceed 15 m (50 ft), and is generally less than 10 m (30 ft). Their width ranges from 91 to 609 m (300 to 2,000 ft), but most are less than 152 m (500 ft) wide. Many kames are round or subround, but a few are long and narrow. The dimensions of the eskers in the Culbertson area are as follows: widths range from 30 to 100 m (100 to 300 ft), but average 61 m (200 ft); heights range from a meter (3ft) to 20 m (60 ft) but average 3 m (10 ft); lengths range from a few hundred feet to nearly 3 km (2 mi). Thickness of the esker and kame deposits varies greatly within short distances. Generally, they are at least as thick as their height above the immediately adjacent till plain. Therefore, eskers are as much as 20 m (60 ft) thick and kames are as much as 30 m (100 ft) thick. DAS36 Glasgow quadrangle: Long sinuous ridges of poorly sorted and poorly stratified ice-contact sand and gravel as much as 20 m (66 ft) thick. Contains boulders as much as 50 cm (2 ft) in diameter. Includes eskers and kames. DAS15. Plentywood quadrangle: Brown to light-brown poorly to well-stratified, poorly- to well-sorted, fine to coarse sand and gravel with minor silt. Deposited by glacial meltwater flowing in channels beneath, within, or on top of ice and, subsequently, let down as the supporting or surrounding ice melted. Deposits are long, discontinuous, narrow and sinuous (eskers), or conical heaps or irregular ridges (kames). Esker and kame deposits are composed of gravel derived from the Flaxville Formation and numerous clasts of granite, gneiss, limestone-dolomite and other erratic clasts from Canada, and consequently, these deposits are similar except for a small percentage of erratics. Esker and kame deposits are generally poorly bedded and sorted, but well stratified silt, sand, or fine gravel beds commonly abut poorly sorted material, or, locally, lenses of till; crossbedding is pronounced in some beds in eskers and kames. Bedding along the sides of eskers tends to be parallel to the side slopes owing to collapse of the retaining ice walls. Local faults and tilted and contorted bedding in the deposits indicate collapse when the enclosing ice melted. The few exposures seen in the area indicate till is the material underlying esker and kame deposits. Till is on the sides and crests of some eskers and kames, indicating they were formed in and under ice. Locally, esker and kame deposits are overlain by alluvium, colluvium, lake deposits, and eolian deposits. Thickness of the esker and kame deposits varies greatly within short distances. Generally, they are at least as thick as their height above the immediately adjacent till plain. | 01-15 | dmu, map unit | 255,250,5 | None | {9D750781-AF47-4556-BE80-8CDDF54AD27E} | Ice-contact and ice-marginal sediment, mostly coarse-grained | high | None | 5 | DAS26 | DAS15 | DAS35 | DAS33 | DAS34 | {303AA65F-15D3-462F-B74E-A238B368232B} |
| 36 | {174B068F-AC30-45B7-809B-4467F473F655} | map unit | map unit, generic | Qgt | Qgt | Qgt | glacial till | glacial till | Pleistocene | unprovided | Pleistocene | Pleistocene | Culbertson quadrangle: Heterogeneous mixture of clay, silt, sand, and gravel with rare to abundant cobbles and boulders deposited by continental ice sheets during at least three glaciations. Nonstratified or very poorly stratified; nonsorted or poorly sorted. Locally faintly layered, particularly near base and top. May be interbedded, intertongued, or intercalated with sand and gravel or clay and silt. Analyses of 28 samples of till indicated the tills are composed of 24-38 percent clay, 23-46 percent silt, 33-62 percent sand, 1-4 percent granules, 1-21 percent pebbles, and 1 percent cobbles. Deposits representing three glaciations are present in northeastern Montana. The surface till in much of the Culbertson quadrangle is the Crazy Horse till. It commonly contains lenses, pods, and stringers of sorted clay, silt, sand, and gravel. At lower altitudes the till includes subaqueous debris flow deposits. Clayey till is soft and sticky where damp. Clay minerals are dominantly montmorillonite. Thickness of the youngest till (Crazy Horse till) generally is less than 3 m (10 ft). Although the total thickness of all of the till units is generally less than 5 m (16 ft) it may be as much as 30 m (120 ft) thick in buried valleys. Because of the discontinuous lateral distribution of the tills and the sparsity of exposures, the tills deposited during the three glaciations cannot be mapped as separate units Crazy Horse till (late Wisconsin, late Pleistocene)—Yellowish-brown, grayish-brown, brown, brownish-gray, gray, or mottled clay loam and loam. Silty clay or clay where the ice incorporated lake clay and silt in the preglacial Missouri River and Big Muddy Creek valleys; sandy loam and loamy sand where ice incorporated older alluvial sand and gravel. Very calcareous; generally oxidized to depths less than 1.2 m (4 ft). Friable; granular or blocky structure. Loose or poorly consolidated; not extremely compact or hard. Slumps readily in exposures. Pencil-shaped columnar joints are common in oxidized till. White streaks of secondary carbonate and coatings of powdery gypsum (selenite) locally on joint surfaces. Selenite crystals less than 3 mm (⅛ in) long are present on joint surfaces locally; larger crystal, clusters of crystals, and crusts of selenite are absent. Iron oxide stains typically are present in matrix only adjacent to carbonate grains and granules; generally absent on joint surfaces. Manganese oxide stains very uncommon. Moderately pebbly to very pebbly; pebbles, cobbles, and boulders typically much more abundant than in older tills. Granules and pebbles are subangular to well rounded, dominantly erratic limestone and dolomite from Canada; some granite, gneiss, schist, quartzite, chert, sandstone, siltstone, shale; minor ironstone concretions, clinker, agate, silicified wood, and chalcedony. Lignite fragments are ubiquitous in the matrix. Cobbles and boulders are mostly erratic limestone, dolomite, granite, and gneiss. They litter till surfaces that have not been cultivated and cleared of large erratics. The thickness of the till is as much as 5 m (16.4 ft) and as little as 30 cm (1 ft) but generally is only 1 m (3 ft) thick under upland areas. [Abridged from DAS35]. Glasgow quadrangle: Yellowish brown (oxidized) to bluish gray (unoxidized) unstratified, unsorted, unconsolidated to moderately consolidated heterogeneous mixture of 25-30 percent clay, 25-40 percent silt, 25-30 percent sand, 1-3 percent granules, 1-2 percent pebbles and cobbles, and less than 1 percent boulders. Lithology of stones in till is: 55 percent quartzite, 26 percent limestone and dolomite, 15 percent igneous and metamorphic (from Canada), and 3-4 percent local sedimentary rocks. Thickness averages 5 m (16 ft) but may be as much as 83 m (280 ft). Includes pre-Illinoian, Illinoian, and Wisconsin tills. DAS15 Opheim quadrangle: Yellowish brown (oxidized) to bluish gray (unoxidized) unstratified, unsorted, unconsolidated to moderately consolidated heterogeneous mixture of 25-30 percent clay, 25-40 percent silt, 25-40 percent sand | 01-16 | dmu, map unit | 242,242,77 | None | {F2EBB19F-A973-4D08-880A-67F9FA280BBC} | Glacial till | high | None | 5 | DAS35 | DAS15 | DAS37 | DAS35 | DAS33 | DAS34 | DAS13 | {174B068F-AC30-45B7-809B-4467F473F655} |
| 32 | {F86130D7-11E1-4085-BFA4-3AD29E31D1FC} | map unit | map unit, generic | Qgl | Qgl | Qgl | glacial lake deposit | glacial lake deposit | Pleistocene | unprovided | Pleistocene | Pleistocene | Culbertson quadrangle: Light brown and gray clay, silt, and sand formed in shallow temporary glacial lakes. As the ice front retreated meltwater was impounded where the land sloped toward the ice. One of the largest temporary lakes was in the buried valley of the pre-glacial Missouri River west of Rocky Point and the flood plain of Big Muddy Creek. The deposits may underlie 40 square miles (64 sq. km). Several small glacial lakes formed between the retreating lobe of ice in the northeast corner of the Culbertson 30’ x 60’ quadrangle and a low drainage divide in the east central part of the quadrangle. The glacial lake deposits are thin, generally 3 to 5 m (10 to 15 ft) thick, but locally may be as much as 20 m (60 ft) thick. Analyses of glacial lake samples indicated that they range from 22 to 56% clay, 39 to 50% silt, and 2 to 30% sand. Southeastern part of quadrangle, referred to as Sprole silt: Laminated yellowish-gray silt, clay, and silty clay as much as 30.5 m (100 ft) thick that underlie till. The type locality of the silt is 9 km (6 mi) west of the Culbertson quadrangle in the NW ¼ of the SW ¼ of sec. 3, T. 27 18 N., R. 51 E.) in an abandoned gravel pit near an unnamed coulee. The exposure is 6 km (4 mi) east of Poplar and 3 km (2 mi) northwest of Sprole siding on the Great Northern Railroad. The lower half of the deposit is composed of well-stratified, thin-bedded, yellowish-gray silt and clay containing scattered pebbles. The upper half of the deposit is siltier and bedding is less pronounced. It was deposited in a lake that formed when the ice advanced into the area and blocked the Missouri River. After their deposition, it was covered by at least 5 m (15 ft) of till. No accurate figures on the thickness of the silt are available but thickness varies greatly within a short distance. The estimated thickness of an outcrop in sec. 3, T. 27 N., R. 51 E. is 30.5 m (100 ft). A thickness of 20 m (65 ft) was measured in sec. 13, T. 28 N., R. 50 E. The silt is about 18 m (60 ft) thick in sec. 27, T 29 N., R. 51 E. The deposit thins westward from that outcrop within a short distance and becomes too thin to map but may be present in many places as silt, clay, and sand overlying the Wiota gravels and underlying the till. DAS38. Plentywood quadrangle: Light brown and gray clay, silt and sand formed in temporary glacial lakes rimmed by or impounded by ice. Thickness is generally 3 to 5 meters but may be as much as 20 meters. Analyses of glacial lake samples indicated that they range from 22 to 56% clay, 39-50% silt, and 2-30% sand. The glacial lake deposits are estimated to be less than 3 m (10 ft) thick silt, and 2-30% sand. [Abridged from DAS35. Scobey and Wolf Point quadrangles: Light brown and gray clay, silt and sand with sparse scattered dropstones. Beach bar and strandline deposits are sandy fine to medium pebble gravel deposited as spits, hooks, bay mouth bars, offshore bars. Quiet and deep water deposits are varved. Analyses of glacial lake samples indicated that they range from 22 to 56% clay, 39-50% silt, and 2-30% sand. The size distribution of beach deposits is 3% silt, 49% sand, and 48% gravel. The glacial lake deposits are generally only one to 3 m (3-9 ft) thick. The bar and spit deposits are as much as 5 m (16 ft) thick. Note that glacial lake deposits are shown more extensively on DAS33 than indicated on USDA soils maps. DAS33, Western quadrangles: Grayish yellow, yellowish brown, grayish brown, brown, yellowish gray, olive gray, brownish gray, gray, or mottled, calcareous silt and sand mixed with minor clay and gravel. Generally well stratified and well sorted. Typically horizontally bedded or massive, fine or medium sand containing scattered granules or small pebbles. Commonly interbedded or intercalated with massive, bedded or laminataed silt containing dropstones. Commonly slumped and contorted on hillslopes. Detrital fragments of bedrock lignite are abundant in many areas, concentrated in sand crossbeds. Thickness 3-26 ft (1-8 m), locally > 33 ft (10 m). DAS13. | 01-17 | dmu, map unit | 234,255,40 | None | {1F5343B9-92D0-4717-BE09-18D334AA8173} | Lacustrine sediment | high | None | 5 | DAS36 | DAS35 | DAS33 | DAS13 | {F86130D7-11E1-4085-BFA4-3AD29E31D1FC} |
| 43 | {DE930CAF-FC3F-4B3A-AE25-4710CF77FB3A} | map unit | map unit, generic | Qwi | Qwi | Qwi | Wiota Formation | Wiota Formation | Pleistocene | unprovided | Pleistocene | Pleistocene | Glasgow and Opheim quadrangles: Reddish brown coarse quartzite gravel, sand, and silt. Contains sparse scattered erratic stones from Canada (granite, gneiss, schist, limestone, dolomite). Size distribution: 5 percent silt, 15 percent sand, 5 percent granules, 70 percent pebbles. Thickness is 7.5 m (25 ft). Horizontal and vertical facies changes occur within short distances. DAS15 Culbertson and Plentywood quadrangles: Light-brown, brown or gray sand, silt, clay, and fine to coarse gravel. Well stratified to poorly stratified. The lower part of the formation generally consists of moderately well-bedded sandy gravel containing numerous lenses of medium-grained sand and silt. The upper part is generally finer grained and contains intercalated lenses of clay. The formation grades laterally within short distances from deposits consisting entirely of sand, silt, or clay to those consisting of coarse gravel. Because it was stream deposited, the texture of the formation varies from outcrop to outcrop and most exposures exhibit crossbedding. A few feet of silt and fine- to medium-grained sand generally constitute the top of the deposit. Contacts with underlying units are generally sharp, but contacts with overlying units are not always sharp, especially where the upper part was partly incorporated into the overlying till. Age probably ranges from Pliocene to late Pleistocene. Some of the higher older, parts of the formation were probably deposited just after the last and lowest parts of the Flaxville Formation were laid down in late Pliocene time, whereas the youngest and lowest parts were deposited just prior to the pre-Illinoian glaciation.The thickness of the Wiota Formation varies widely within any given deposit and is commonly 3-6 m (9-20 ft). [Greatly abridged from DAS 9]. Scobey quadrangle: Light-brown, brown or gray sand, silt, clay, and fine to coarse gravel. Well stratified to poorly stratified and poorly to well sorted. Mostly clay, silt, sandy silt, and sand; gravel is a minor component. Mechanical analyses of samples indicate that the Wiota Formation is poorly graded and contains a large percentage of sand. The lower part of the formation generally consists of moderately well-bedded sandy gravel containing numerous lenses of medium-grained sand and silt. The upper part is generally finer grained and contains intercalated lenses of clay. The formation grades laterally within short distances from deposits consisting entirely of sand, silt, or clay to those consisting of coarse gravel. Texture is variable, and most exposures exhibit crossbedding. A few feet of silt and fine- to medium-grained sand generally constitute the top of the deposit. Unconformably overlies each of the bedrock formations and in turn is unconformably overlain by younger Pleistocene deposits, generally till. In unglaciated areas, the formation is locally thinly veneered with loess, alluvium, and colluvium. In glaciated areas, deposits of the Wiota Formation were overridden and buried by the advancing glaciers, and till was deposited on them. Contacts with underlying units are generally sharp, but contacts with overlying units are not always sharp, especially where the upper part of the Wiota Formation was partly incorporated into the overlying till. The earlier parts of the Wiota Formation consist of reworked gravel from the Flaxville Formation and are generally at or above 670 m (2,200 ft) but below 822 m (2,700 ft). The younger parts of the Wiota Formation are similar to the older parts but include a small additional percentage of granitic, gneissic, schistose, limestone, and dolomitic pebbles derived from Canada. Erratics may have been injected into the upper part of the formation by overriding ice. The later parts of the Wiota are generally below 640 m (2,100 ft). Most of the deposits in the Scobey 30’ x 60’ quadrangle formed around the edges of remnants of the Flaxville Fm. by erosion of those remnants and deposited as fan deposits.The thickness of the Wiota Formation varies widely within any given deposit, but is commonly 3-6 m (9-20 ft). [G | 01-18 | dmu, map unit | -25,-25,-25 | None | {1EA7E66A-155C-44AA-9F48-2FC62780A963} | Sand and gravel of unspecified origin | high | None | 5 | DAS15 | DAS36 | DAS34 | {DE930CAF-FC3F-4B3A-AE25-4710CF77FB3A} |
| 42 | {11FAED68-56C2-49C0-A969-D71FC65376CB} | map unit | map unit, generic | QTgr | QTgr | QTgr | gravel deposit | gravel deposit | Pleistocene and/or Pliocene | unprovided | Pliocene | Pleistocene | Deposits may represent remnants of alluvial braid-plain sedimentation across broad surfaces flanking the Bears Paw Mountains and other mountain uplifts of central Montana. Clast size dominantly cobble, pebble, sand, silt, and clay. May include boulders. Thickness typically 30 ft (10 m), but may be as much as 82 ft (25 m). | 01-19 | dmu, map unit | 242,229,76 | None | {1EA7E66A-155C-44AA-9F48-2FC62780A963} | Sand and gravel of unspecified origin | high | None | 5 | DAS10 | {11FAED68-56C2-49C0-A969-D71FC65376CB} |
| 44 | {D84CD41E-47AD-4768-9C4F-616670A4E322} | map unit | map unit, generic | Tf | Tf | Tf | Flaxville Formation | Flaxville Formation | Pliocene and Miocene | unprovided | Miocene | Pliocene | Culbertson quadrangle: The formation is composed of several lithologic units. In nearly all exposures, the basal part of is a coarse sandy quartzite gravel 6- 15 m (20-50 ft) thick. Lenticular sandy and clayey strata 6-12 m (20-40 ft) thick overlie this part of the formation. Clasts consist chiefly of well-rounded quartzite pebbles, although smooth, well-rounded cobbles and boulders as large as 30.5 cm (1 ft) in diameter are also common. Seventy percent of the pebbles are fine- to medium-grained quartzite, mostly grayish red but including some yellowish or grayish green. Twenty percent of the pebbles are moderate red jasperlike argillite and an even smaller percentage includes olive-gray to black argillite, chert, and agate. A minor, but distinctive, group of pebbles is composed of green tinguaite porphyry. Most of the pebbles, cobbles, and boulders in the formation are coated with a moderate yellowish-brown stain, probably iron oxide, which has penetrated the quartzites to depths of as much as 3 mm (⅛ inch). Locally, the formation has been cemented by calcium carbonate to form sandstone and conglomerate. Individual beds in the formation range in thickness from 0.3 to 3 m (1 to 10 ft). Most beds are crossbedded, indicating much cutting and filling occurred as streams deposited the formation. The formation unconformably overlies each of the older bedrock units. In places it is overlain by glacial and eolian deposits. Vertebrate fossils of Pliocene age are abundant in the Flaxville Formation. Bones of Hipparion, Procamelus, and mastodon were found in the Culbertson quadrangle. The thickness of the formation varies considerably, but remnants average about 12 m (40 ft) thick. The unit thins to a feather edge around the borders of the mesa-like remnants in the northwest corner of the quadrangle. The formation unconformably overlies the Fort Union Formation, and in places it is overlain by glacial and eolian deposits. [Abridged from DAS36]. Glasgow and Opheim quadrangles: Light reddish brown clay, silt, sand, quartzite gravel, and volcanic ash. Locally cemented by calcium carbonate. Average diameter of pebbles is 4 cm (1.6 in). Contains boulders as much as 30 cm (11 in) in diameter. Size distribution: 2 percent silt, 36 percent sand, 4 percent granules, 58 percent pebbles. Lithology: 90 percent brown and red quartzite; remainder chalcedony and fragments from the Ft. Union Formation. Locally contains large lenses of volcanic ash as much as 6 m (20 ft) thick. Thickness is as much as 25 m (82 feet but averages 10 m (33 ft) in Opheim area. DAS15 Plentywood quadrangle: The formation is composed of several different lithologic units. The basal unit, which is 6-15 m (20-50 ft) thick is nearly everywhere composed of quartzitic gravel and sand. Sandy and clayey strata 6-12 m (20-40 ft) thick, overlie the gravel and sand unit. About 70 percent of the pebbles in the gravel members of the formation consist of fine- to medium-grained quartzite. The average diameter of the pebbles is 1 ½ inches; boulders as much as 1 foot in diameter are a minor component of the gravel. The pebbles, cobbles, and boulders are smooth and well rounded. Most are moderate yellowish brown (10YR 5/4). Broken pebbles show a thin rind of weathering about 1/8 of an inch thick. Some broken pebbles are distinctly stratified; the darker parts are dark yellowish brown (10YR 4/2). Twenty percent of the pebbles are moderate red (5R 4/4) when dry but are dark reddish brown (10R ¾) when wet. Grayish-red quartzite pebbles (10R 4/2) become dark reddish brown (10R ¾) when wet. A minor percentage of the pebbles are dusky yellow green (5GY 5/2) or grayish green (10GY 5/2); when wet, they are one value darker. A small number of pebbles are olive gray (5Y 3/2) to black argillite, whereas others are chert and agate. A minor but distinctive lithologic type consists of green tinguaite porphyry whose feldspar phenocrysts are distinctly zoned. These pebbles apparently came from the Judith Mountains 200 miles west of the area. Locally, the formation has been cemented by calcium carbonate | 01-20 | dmu, map unit | 222,134,31 | None | {1EA7E66A-155C-44AA-9F48-2FC62780A963} | Sand and gravel of unspecified origin | high | None | 5 | DAS36 | DAS15 | DAS09 | DAS33 | DAS19 | {D84CD41E-47AD-4768-9C4F-616670A4E322} |
| 54 | {D9F33F00-1FAC-41E8-BAB7-3D3A36FA5E2A} | map unit | map unit, generic | To | To | To | Opheim formation | Opheim formation | Miocene | unprovided | Miocene | Miocene | Pale tan or pale grayish orange silt and sand; contains several horizons of white caliche (paleosols). Equivalent to the Ogallala Formation.Thickness approximately 10 m (33 ft). | 01-21 | dmu, map unit | 0,0,0 | None | {13254751-2CAA-450A-A8BA-9EA4DF9D4BDC} | Silt and clay of unspecified origin | medium | None | 5 | DAS37 | {D9F33F00-1FAC-41E8-BAB7-3D3A36FA5E2A} |
| 63 | {BE8A23CD-1908-4990-BC79-CAEC2E09A8BD} | map unit | map unit, generic | Tw | Tw | Tw | Wasatch Formation | Wasatch Formation | Eocene | unprovided | Eocene | Eocene | Variegated red, pink, lavender, light-green, yellow-gray, and white shale, bentonitic claystone, and siltstone with small calcareous concretions; interbedded light-gray, brown and green, fine- to coarse-grained, cross-bedded sandstones with lenses of boulder conglomerate in upper part of formation containing clasts derived from mountain uplifts to the west or southwest including argillite and quartzite from Proterozoic Belt Supergroup rocks, porphyritic igneous rocks, and limestone and dolomite; clasts locally crushed, fractured, and re-cemented; nonmarine; fossil plants and vertebrates indicate early Eocene age; top of formation missing due to pre-volcanic erosion or tectonic disruption or both. Maximum measured thickness 800 ft (240 m); original maximum thickness probably exceeded 1,000 ft (300 m). | 01-22 | dmu, map unit | 215,192,56 | None | {AB5A96BE-7478-43F0-8902-44A5D21B9FE7} | Sandstone and mudstone | medium | None | 5 | DAS10 | DAS18 | {BE8A23CD-1908-4990-BC79-CAEC2E09A8BD} |
| 49 | {582B0680-08CC-4798-991E-0747B08DFD10} | map unit | map unit, generic | Tfu | Tfu | Tfu | Fort Union Formation | Fort Union Formation | Paleocene | unprovided | Paleocene | Paleocene | Light-brown to light-yellow, thin- to thick-bedded or massive sandstone with brown sandstone concretions; interbedded with light-colored to greenish siltstone, claystone, and shale; contains carbonaceous shale and coal, locally mined; nonmarine; fossil plants and vertebrates indicate Paleocene age. Maximum thickness about 1,300 ft (400 m). | 01-23 | dmu, map unit | 255,214,35 | None | {AB5A96BE-7478-43F0-8902-44A5D21B9FE7} | Sandstone and mudstone | high | None | 5 | DAS10 | DAS18 | {582B0680-08CC-4798-991E-0747B08DFD10} |
| 46 | {E4272FAF-52D2-4469-B124-91F29E228882} | map unit | map unit, generic | Tfsb | Tfsb | Tfsb | Sentinel Butte Member | Sentinel Butte Member of Fort Union Formation | Paleocene | unprovided | Paleocene | Paleocene | Dark-gray shale locally underlain by orangish brown or brown, iron oxide-stained, cross-bedded channel sandstone with medium- to coarse-grained, angular to subangular, poorly sorted clasts. Channel bases display scour features including abundant rip-up clasts. Gray or grayish-brown, poorly resistant mudstone about 20 ft thick underlies the sandstone locally. Prominent coal beds are present near the base of the member in most areas. Upper part of member removed by erosion. Exposed thickness as much as 990 m (300 ft). | 01-23-01 | dmu, map unit | 206,173,70 | None | {AB5A96BE-7478-43F0-8902-44A5D21B9FE7} | Sandstone and mudstone | high | None | 5 | DAS22 | {E4272FAF-52D2-4469-B124-91F29E228882} |
| 48 | {BFFF04AA-D865-4D89-8094-436566DF63BB} | map unit | map unit, generic | Tftr | Tftr | Tftr | Tongue River Member | Tongue River Member of Fort Union Formation | Paleocene | unprovided | Paleocene | Paleocene | Yellow, orange, or tan, fine- to medium-grained sandstone and thinner interbeds of yellowish-brown, orange, or tan siltstone and light-colored mudstone and clay. Clay dominantly nonswelling. Contains several prominent lignite beds. Member generally poorly cemented and weathers to badland topography, but some relatively resistant sandstone beds form caprocks. Locally contains silicified wood, freshwater mollusks, and plant molds. About 183 - 260 m (600-850 ft) thick. | 01-23-02 | dmu, map unit | 247,222,86 | None | {AB5A96BE-7478-43F0-8902-44A5D21B9FE7} | Sandstone and mudstone | high | None | 5 | DAS32 | DAS38 | {BFFF04AA-D865-4D89-8094-436566DF63BB} |
| 45 | {E014BB1F-0D76-4ED6-9B8B-029C71205A92} | map unit | map unit, generic | Tfle | Tfle | Tfle | Lebo Member | Lebo Member of Fort Union Formation | Paleocene | unprovided | Paleocene | Paleocene | Medium- to dark-gray, grayish-brown and olive-gray sandstone, siltstone, and mudstone that is typically smectitic or carbonaceous, interbedded with gray to dark-gray, silty shale, thin
yellowish-gray siltstone and sandstone, and thin, lenticular lignite beds. Contains small-scale, light-gray, fine- to medium-grained, cross-bedded channel sandstones. Clay typically exhibits characteristic “popcorn”
weathering. Base of formation marked by thick coal bed, impure in places. Thickness about 60-85 m (200-275 ft). [DAS leg Scobey and Sidney] | 01-23-03 | dmu, map unit | 220,206,81 | None | {AB5A96BE-7478-43F0-8902-44A5D21B9FE7} | Sandstone and mudstone | high | None | 5 | DAS28 | DAS22 | {E014BB1F-0D76-4ED6-9B8B-029C71205A92} |
| 47 | {DFB4414C-9ECE-469D-A923-42A0DB84449F} | map unit | map unit, generic | Tft | Tft | Tft | Tullock Member | Tullock Member of Fort Union Formation | Paleocene | unprovided | Paleocene | Paleocene | Alternating tan, yellow, brown, and gray, dominantly planar beds of sandstone, siltstone, and shale, and thinner dark gray or black beds of carbonaceous or lignitic shale, and thin, lenticular lignite beds. Thickness about 180 ft. 9-55 m (30-180 ft) thick. | 01-23-04 | dmu, map unit | 234,199,53 | None | {AB5A96BE-7478-43F0-8902-44A5D21B9FE7} | Sandstone and mudstone | high | None | 5 | DAS32 | DAS38 | {DFB4414C-9ECE-469D-A923-42A0DB84449F} |
| 66 | {D027598E-8237-44C0-80E0-CCE2CFB87225} | header | header, generic | None | None | None | Montana Group | Montana Group | None | None | None | None | None | 01-24 | dmu, header | None | None | None | None | None | None | 9 | DAS24 | {D027598E-8237-44C0-80E0-CCE2CFB87225} |
| 9 | {0620A150-F048-4563-8FA6-01CB2988B49F} | map unit | map unit, generic | Khfh | Khfh | Khfh | Hell Creek and Fox Hills Formations | Hell Creek Formation and Fox Hills Formation of Montana Group | Late Cretaceous | unprovided | Late Cretaceous | Late Cretaceous | Includes, in descending order: Hell Creek Formation composed of interbedded gray to light-brown, locally massive sandstone with brown sandstone concretions, and white to light-colored to drab siltstone, claystone, and shale locally calcareous with abundant small calcareous concretions; brownish-gray carbonaceous bentonitic claystone also interbedded; persistent beds of carbonaceous shale and lenticular coal near base of formation, locally mined; nonmarine; rare fossil plants and vertebrates indicate latest Cretaceous age; thickness 250 to 500 ft (80 to 150 m); Fox Hills Formation composed of light-yellowish-gray, light-brown, and yellow, thin-bedded to massive sandstone, commonly concretionary; minor interbeds of brown and gray siltstone and shale; locally contains diagnostic marine fossils. Thickness 60 to 150 ft (20 to 45 m). Combined thickness 480 to 600 ft (146 to 597 m). | 01-24-01 | dmu, map unit | 127,229,0 | None | {AB5A96BE-7478-43F0-8902-44A5D21B9FE7} | Sandstone and mudstone | high | None | 5 | DAS10 | DAS18 | {0620A150-F048-4563-8FA6-01CB2988B49F} |
| 8 | {E794B8CF-362F-4006-B452-CAF9ED28519B} | map unit | map unit, generic | Khc | Khc | Khc | Hell Creek Formation | Hell Creek Formation of Montana Group | Late Cretaceous | unprovided | Late Cretaceous | Late Cretaceous | Culbertson quadrangle: Well stratified shales, siltstones, sandstones, and carbonaceous shales. The lower 15-30 m (50-100 ft) is predominantly a medium-tan friable sandstone; the upper half is gray siltstone and shale. The overall color of the formation is a somber greenish gray. Weathered surfaces of many bentonitic shale beds have a spongy appearance. The lower half of the formation consists of beds of coarse sandstone composed of abundant dark minerals that contrast markedly with the underlying fine-grained, lighter colored sandstone of the Fox Hills Formation. Large-scale crossbedding in channels contrasts sharply with the underlying parallel-bedded sandstone of the Fox Hills Formation. Large, log-shaped, cross-bedded sandstone concretions are in the basal conglomeratic sandstone unit of the Hell Creek Formation, and are especially common in the lower 30 m (100 ft). The concretions are circular to oval in cross section and range in diameter from 1-2 m (3-6 ft) and in length from 3-10 m (10- 30 ft). Spherical concretions, as much as 7.6 cm (3 in) in diameter, are also common in the sandy lower half of the formation. The upper half of the formation consists mainly of sandstone, siltstone, claystone, shale, lignite, and carbonaceous claystone. Individual beds are generally 0.3-1 m (1-3 ft) thick and of uniform texture over short distances. Sandstone beds are more lenticular than siltstone and claystone beds. The rest of the unit consists of bentonitic and carbonaceous shale beds. The bentonitic shale outcrops have a characteristic spongy appearance caused by the swelling of the bentonite. The carbonaceous shales, which contain a large proportion of macerated plant fragments, are brown, thick bedded, and fissile. The strata generally are greenish gray but some are shades of light olive gray, brownish gray, and gray. The carbonaceous shale beds are as much as 2.7 m (9 ft) thick. In fresh exposures, the lignite is tough and dense, has a woody structure, contains silicified plant remains, and it slakes rapidly to a black powder when exposed to air. Silicified plant remains, pyrite, marcasite, gypsum, limonite, hematite, and numerous clay partings are common impurities in lignite beds. The lower half of the formation is a conglomeratic sandstone that contains mud balls as much as 0.3 m (1 ft) in diameter, fragments of sandstone, limonite concretions, sparse well-rounded olive-gray quartzite pebbles several inches in diameter, and fragments of dinosaur bone and petrified wood. Many large blocks of lignite and silicified wood are also included locally. Some lignitized wood fragments and quartzite pebbles are present at and above the contact with the Fox Hills Formation, but none were found below this contact. Dinosaur bones are prevalent throughout the formation, and in some areas are common enough to differentiate the strata in which they occur from the underlying Fox Hills Formation and the overlying Fort Union Formation. Most of the vertebrate remains found are of Triceratops. The range in color of the formation is virtually from black to white. The carbonaceous shale and lignitic beds are black and weather to grayish black; some of the sandstone beds that are nearly white in appearance are actually light yellowish gray and weather to about the same color. Shale beds are light gray or olive gray and weather to pale olive. Some of the sandstone is dusky yellow and dark yellowish orange and weathers to pale olive. An analysis of approximately 548 m (1,800 ft) of measured sections of Hell Creek Formation revealed that 61 percent is sandstone, 4 percent is siltstone, 34 percent is claystone and shale, and 1 percent is carbonaceous shale. The Hell Creek Formation unconformably overlies the Fox Hills Formation, conformably underlies the Tertiary Fort Union Formation, and fills channels in the Fox Hills Formation in many places. Most of the channels are 3-5 m (10-15 ft) deep but one 15 m (45 ft) deep was found on the south side of Redwater Creek. Channels are filled with fragments of limonite concretions and scattered gray quartzi | 01-24-02 | dmu, map unit | 125,180,73 | None | {AB5A96BE-7478-43F0-8902-44A5D21B9FE7} | Sandstone and mudstone | high | None | 5 | DAS36 | DAS15 | DAS33 | DAS10 | DAS18 | {E794B8CF-362F-4006-B452-CAF9ED28519B} |
| 6 | {3A3B57D8-EB91-4320-9372-28B14D11A6F1} | map unit | map unit, generic | Kfh | Kfh | Kfh | Fox Hills Formation | Fox Hills Formation of Montana Group | Late Cretaceous | unprovided | Late Cretaceous | Late Cretaceous | Culbertson quadrangle: Shale and siltstone 18 m (60 ft) thick and an overlying cliff-forming sandstone as much as 10.6 m (35-40 ft) thick. The colors of the lower transition beds become gradually lighter upward from the dark olive gray of the Bearpaw shale to light olive gray. Shale beds are darker than sandy beds, which are olive brown, yellowish brown, or dusky yellow. As the sandstone part of the formation weathers, it changes from pale yellowish brown to yellowish brown or to dark yellowish orange. The lower part of the formation consists of parallel-bedded layers of gray shale, siltstone, and fine-grained clean sandstone a few inches thick. These grade upward from more clayey beds at the bottom to sandier cross-bedded layers at the top. The upper part of the formation is a cross-bedded fine-grained sandstone. In most places, spheroidal calcareous sandstone concretions predominate in a matrix of unconsolidated sand. Locally, however, the sand has been cemented by calcium carbonate into a ledge-forming sandstone. The Fox Hills Formation is conformably underlain by the Bearpaw shale and unconformably overlain by the Hell Creek Formation. Stream channels, locally as much as 15 m (50 ft) deep, were cut into the Fox Hills Formation prior to deposition of the Hell Creek Formation. In these places, the overlying Hell Creek Formation rests upon the transitional shale beds of the lower part of the Fox Hills Formation. Several types of concretions are in the formation. The largest and most abundant are disk shaped and occur in the upper sandstone part of the formation. Ball-shaped pyrite concretions as much as 5 cm (2 in) in diameter are common. Disk-shaped limonite or clay ironstone concretions as much as 15 cm (6 in) in diameter are abundant. Soft, white, round, very fine-grained sand concretions as much as 5 cm (2 in) in diameter are scattered through some of the sandstone beds. Large disk-shaped aragonite concretions as much as 0.6 m (2 ft) in diameter and several inches thick are common in some strata in the transition beds. All the cemented sandstone in the upper part of the formation above the transition beds is calcareous, but the transition beds are noncalcareous. Carbonaceous shale and lignite occur locally in the upper part of the formation. In most of the area, the lowermost silt and shale grade transitionally upward into sandstone The formation varies greatly in thickness within short distances, and in places it has been almost completely removed by erosion. [Abridged from DAS 10]. Glasgow quadrangle: Lower third of formation consists of thin yellowish gray to dark yellowish-orange soft claystone, siltstone, and fine sandstone. These beds are transitional between the underlying Bearpaw Shale and the overlying two-thirds of the formation. Their composition is 96 percent clay and silt and 4 percent sand. The upper part of the formation consists of fine-grained, thin- to massive-bedded, calcareous, yellowish brown to orange brown sandstone. Upper two-thirds consists of 44-52 percent clay and silt and 48-56 percent sand. Thickness of transitional beds is approximately 13 m (40 ft). Upper sandstone part of formation is as much as 26 m (85 ft) thick. DAS35 Opheim quadrangle: Lower part is transitional between the underlying Bearpaw Shale and the sandy part of the formation, and is composed of yellowish gray to dusky yellow or dark yellowish orange fine-grained sandstone and thin-bedded shale and siltstone. Transition zone is composed of 96 percent clay and silt and 4 percent sand. Thickness is 10-12 m (35-40 ft). Upper part of formation is 44-52 percent clay and silt and 48-56 percent sand. Thickness of upper part varies form 0 to 32 m (0 to 46 ft). Lower contact gradational with with Bearpaw Shale; upper contact is unconformable. DAS15. Scobey and Wolf Point quadrangles: Shale and siltstone 18 m (60 ft) thick in the lower part and an overlying continental cliff-forming sandstone as much as 10.6 m (35-40 ft) thick.The colors of the lower transition beds become gradually lighter upward from the dark olive gray of the Be | 01-24-03 | dmu, map unit | 169,242,72 | None | {BA96A3AA-660F-4C81-87EB-463C01EB9F06} | Sandstone | high | None | 5 | DAS35 | DAS15 | DAS33 | DAS10 | DAS18 | {3A3B57D8-EB91-4320-9372-28B14D11A6F1} |
| 3 | {D8755051-B219-45DF-B7C9-CDEA7A659FA3} | map unit | map unit, generic | Kb | Kb | Kb | Bearpaw Formation | Bearpaw Formation of Montana Group | Late Cretaceous | unprovided | Late Cretaceous | Late Cretaceous | Culbertson quadrangle: Olive-gray and dark-gray fissile marine shale containing numerous bentonite beds and fossiliferous concretionary zones. The unit is chiefly olive-gray shale. Two mechanical analyses of the shale made by the Materials Testing Laboratory, Montana State Highway Commission, Helena, Mont., indicate that the shale consists of a silty, slightly sandy clay; clay and silt range from 62 to 67 percent and sand ranges from 33 to 38 percent. A wet analysis by the U.S. Corps of Engineers showed that weathered shale is 5 percent sand, 40 percent silt, and 55 percent clay. The clay fraction is tough, highly plastic, 30 and has high compressibility. All outcrops in the Culbertson area are weathered; depth of weathering is at least 2 m (6 ft) and as much as 15 m (50 ft). Bentonite interbedded in the shale occurs as beds or as disseminated particles, and because of its swelling properties imparts a spongy texture to the weathered surfaces of the shale. Montmorillonite is the only clay mineral present. The color of unweathered bentonite ranges from pale green to pale yellow. Lower contacts of the bentonite beds are sharp but upper contacts are gradational. Two types of concretions occur in the Bearpaw shale. The most abundant concretions, composed of iron oxide and clay, are as much as 15 cm (6 in) in diameter and are disk shaped. Other concretions consisting of medium-dark-gray nearly pure limestone are round, egg-shaped, or irregularly rounded, and their diameters range from 15 cm to 2 m (6 in to 6 ft); most are about 30 cm (1 ft). The interiors of many limestone concretions are full of shrinkage cracks; some have been partly filled with yellow calcite crystals and a few contain barite crystals. Many of the limestone concretions contain well-preserved fossils such as baculites and scaphites, but only a few of the ironstone concretions contain fossils and these are poorly preserved. The lowest concretions are found 61 m 31 (200 ft) below the top of the Bearpaw Shale and contain Baculites compressus corrugatus. The next higher zone, 30-48 m (100-160 ft) below the top of the Bearpaw Shale, is characterized by Baculites n. sp., specimens. The highest zone of concretions is characterized by Baculites baculus and Discoscaphites n. sp. and occurs about 12 m (40 ft) below the top of the Bearpaw Shale. The Bearpaw shale was deposited in a sea as indicated by the numerous marine fossils. Bentonite beds and disseminated bentonite in the shale indicate that many volcanic eruptions occurred during the deposition of the shale. The formation is transitional into beds of the Fox Hills Formation. The base of the Bearpaw Shale is not exposed in the area. The formation is approximately 305 m (1,000 ft). [Abridged from DAS 10]. Glasgow quadrangle: Dark gray clayey shale with disseminated or distinct beds of bentonite as much as 30 cm (1.2 in) thick. Contains ovoid and disc-shaped septarian concretions composed of clay-ironstone and limestone. Thickness is approximately 345 m (1,140 ft). DAS36 Opheim quadrangle: Fossiliferous, semiconsolidated olive gray, fissile marine shale containing numerous bentonite beds and concretionary zones. Thickness ranges from 330 to 360 m (1,082 to 1,180 ft), but averages 345 m (1,132 ft). DAS15 Scobey and Wolf Point quadrangles: Olive-gray and dark-gray fissile marine shale containing numerous bentonite beds and fossiliferous concretionary zones. Two mechanical analyses of the shale made by the Materials Testing Laboratory, Montana State Highway Commission, Helena, Mont., indicate that the shale consists of a silty, slightly sandy clay; clay and silt range from 62 to 67 percent and sand ranges from 33 to 38 percent. A wet analysis by the U.S. Corps of Engineers showed that weathered shale is 5 percent sand, 40 percent silt, and 55 percent clay. The clay fraction is tough, highly plastic, and has high compressibility. Bentonite interbedded in the shale occurs as beds or as disseminated particles, and because of its swelling properties imparts a spongy texture to the weathered surfaces of the shale. Montmor | 01-24-04 | dmu, map unit | 145,222,121 | None | {D2A0E6BD-A10F-490C-BDF5-680E02FE5DE6} | Mudstone | high | None | 5 | DAS10 | DAS18 | DAS15 | DAS36 | {D8755051-B219-45DF-B7C9-CDEA7A659FA3} |
| 11 | {CA58309E-9A15-48F2-AFA7-7C23D2D9C333} | map unit | map unit, generic | Kjr | Kjr | Kjr | Judith River Formation | Judith River Formation of Montana Group | Late Cretaceous | unprovided | Late Cretaceous | Late Cretaceous | Glasgow and Opheim quadrangles: Medium to dark gray, brown, and greenish shale and sandstone; bentonitic shale and beds of bentonite are abundant. Shale is thinly interbedded with silt and sandstone. Composed of 26 percent shale 73 percent sandstone, and 1 percent lignite. Carbonaceous shale grades laterally into lignite. Sandstone is fine- to medium-grained, well indurated, gray to greenish gray and weathers buff to brown. Glauconitic sandstone in basal part Thickness is approximately 99-106 m. (325-290 ft). DAS15 Western quadrangles: Light-brown, light gray to yellow, fine- to medium-grained, strongly lenticular, resistant sandstone, locally gas-bearing, siltstone, and white, yellow, greenish, and light-gray claystone and shale; near top commonly are one or more horizons of oyster-shell coquina in dark shale, and several carbonaceous shales and thin coals that have been locally mined; locally, uppermost beds are white, clay-rich marine sandstone; locally, lowermost sandstone is burrowed by marine organisms (Parkman Sandstone of subsurface usage); vertebrate fossils locally common; on resistivity well logs correlation of nonmarine sandstones is uncertain because of lateral lensing. Thickness 175 to 670 ft (53 to 200 m). DAS10 and DAS18 | 01-24-05 | dmu, map unit | 132,201,127 | None | {BA96A3AA-660F-4C81-87EB-463C01EB9F06} | Sandstone | high | None | 5 | DAS15 | DAS10 | DAS18 | {CA58309E-9A15-48F2-AFA7-7C23D2D9C333} |
| 4 | {21B2B372-60AD-43A9-8955-4DDBFE58751F} | map unit | map unit, generic | Kcl | Kcl | Kcl | Claggett Formation | Claggett Formation of Montana Group | Late Cretaceous | unprovided | Late Cretaceous | Late Cretaceous | Glasgow and Opheim quadrangles: Soft dark gray shale and bentonite. Thickness approximately 64-77 m (220-250 ft). DAS15. Western quadrangles: Dark gray or grayish-brown on fresh surfaces, commonly weathered to soft brown; blocky to fissile; characteristic dull-orange weathering, smooth, ovoid, calcareous concretions in middle and upper part of unit; concretions commonly contain yellow calcite vein filling and are commonly highly fractured, forming mounds of small, sharp-edged orange-brown fragments; numerous grayish-white bentonite layers (1 to 5 inches thick (2.5 to 12.5 cm)) in lower 80 ft (20 m) of unit; upper 30 to 200 ft (10 to 60 m) contain laterally persistent sandstone beds forming transitional contact with overlying Judith River Formation. Claggett Formation is involved in extensive landsliding beneath benches formed on lower Judith River Formation. Total thickness 400 to 680 ft (120 to 200 m). DAS10 and DAS18 | 01-24-06 | dmu, map unit | 97,210,37 | None | {D2A0E6BD-A10F-490C-BDF5-680E02FE5DE6} | Mudstone | high | None | 5 | DAS15 | DAS10 | DAS18 | {21B2B372-60AD-43A9-8955-4DDBFE58751F} |
| 5 | {9E23C4D6-91A4-41FB-8CB4-5945AA08E0D5} | map unit | map unit, generic | Ke | Ke | Ke | Eagle Formation | Eagle Formation of Montana Group | Late Cretaceous | unprovided | Late Cretaceous | Late Cretaceous | Light-brown to white sandstone with interbedded gray shale, siltstone, and carbonaceous mudstone and shale; contains as many as 3 massive sandstones, some or all of which may be gas-bearing; lowest sandstone (Virgelle Sandstone) weathers yellow to buff, is massive to cross-stratified, fine- to medium-grained, resistant sandstone with interbedded gray siltstone and shale; generally forms steep cliffs and weathers to rounded forms controlled by extensive jointing, generally ranges from 70 to 170 ft (20-50 m) thick, but thins to inches thick to the east; upper 20 to 130 ft (6 to 40 m) are alternating thin glauconitic sandstone, chert-pebble conglomerate, siltstone, and shale. A prominent zone of polished, primarily black chert pebbles marks top of formation in some areas.Total thickness 140 to 300 ft (40 to 90 m). | 01-24-07 | dmu, map unit | 170,247,136 | None | {FDA3C54D-61D0-4798-ACC3-21A2F1270733} | Mostly sandstone | high | None | 5 | DAS10 | DAS18 | {9E23C4D6-91A4-41FB-8CB4-5945AA08E0D5} |
| 67 | {A7C10E20-088F-4455-A356-27C2C712D243} | header | header, generic | None | None | None | Montana and Colorado Groups | Montana and Colorado Groups | None | None | None | None | None | 01-25 | dmu, header | None | None | None | None | None | None | 9 | DAS24 | {A7C10E20-088F-4455-A356-27C2C712D243} |
| 15 | {38363FDD-2034-4F3B-A1A6-61472F263263} | map unit | map unit, generic | Ktca | Ktca | Ktca | Telegraph Creek Formation through Carlile Formation | Telegraph Creek Formation of Montana Group through Carlile Formation of Colorado Group | Late Cretaceous | unprovided | Late Cretaceous | Late Cretaceous | Includes, in descending order: Telegraph Creek Formation, composed of alternating thin-bedded sandstone, siltstone, and shale weathering gray to brownish gray, with increasing sandstone upward in transition to overlying Eagle Formation; locally massive sandstone up to 50 ft (15 m) thick may be gas-bearing; thickness varies from 0 to 170 ft (0 to 50 m); Niobrara Formation and Carlile Formation together composed of dark-gray to brownish-gray marine shale with minor siltstone, and bentonite beds, septarian calcareous claystone concretions, and concretionary limestone lenses; lower 100 to 200 ft (30 to 60 m) (Carlile Formation) are black shale with distinctive rusty-weathering iron-rich claystone concretions; resistivity logs 1 to 3 miles (2 to 5 km) apart are nearly identical, and many markers can be correlated in wells 10 to 20 miles (15 to 30 km) apart.Thickness 610 to 850 ft (190 to 260 m). Total thickness 750 to 870 ft (230 to 260 m). | 01-25-01 | dmu, map unit | 157,242,0 | None | {2D09A5AE-F0AD-462B-84BC-4092CE922275} | Mostly mudstone | medium | None | 5 | DAS10 | DAS18 | {38363FDD-2034-4F3B-A1A6-61472F263263} |
| 16 | {67CCC2C8-F7E7-4C6A-8BE0-C56D1C848D72} | map unit | map unit, generic | Ktcb | Ktcb | Ktcb | Telegraph Creek Formation through Belle Fourche Formation | Telegraph Creek Formation of Montana Group through Belle Fourche Formation of Colorado Group | Late Cretaceous | unprovided | Late Cretaceous | Late Cretaceous | Unit includes, in descending order, Telegraph Creek, Niobrara, Carlile, Greenhorn, and Belle Fourche Formations. Composed primarily of dark marine shales; creamy-weathering calcareous shale of Greenhorn Formation overlying thin, platy, locally fossiliferous sandstones of Mosby Sandstone Member of Belle Fourche Formation, which forms the only distinctive interval within the sequence. Thickness approximately 1,100 ft (335 m). | 01-25-02 | dmu, map unit | 168,229,66 | None | {2D09A5AE-F0AD-462B-84BC-4092CE922275} | Mostly mudstone | medium | None | 5 | DAS10 | DAS18 | {67CCC2C8-F7E7-4C6A-8BE0-C56D1C848D72} |
| 70 | {5A6E902F-B137-4D8A-B75F-17C88F96DBBD} | header | header, generic | None | None | None | Colorado Group | Colorado Group | None | None | None | None | None | 01-26 | dmu, header | None | None | None | None | None | None | 9 | DAS24 | {5A6E902F-B137-4D8A-B75F-17C88F96DBBD} |
| 7 | {CC0F0524-B905-457D-AE22-0D239C84E2BB} | map unit | map unit, generic | Kgrb | Kgrb | Kgrb | Greenhorn and Belle Fourche Formations | Greenhorn Formation and Belle Fourche Formation of Colorado Group | Late Cretaceous | unprovided | Late Cretaceous | Late Cretaceous | Greenhorn Formation: Gray, sandy, thin-bedded limestone, calcareous and noncalcareous siltstone, dark shale, and bentonite; marine fossils abundant; thickness 10 to 50 ft (3 to 15 m); Belle Fourche Formation: Black shale, minor gray sandstone and siltstone, bentonite; distinctive sandstone bed about 100 ft (30 m) above base contains black chert grit; iron-manganese claystone concretions near base; resistivity logs 1 to 3 miles (2 to 5 km) apart are nearly identical, and many markers can be correlated in wells 10 to 20 miles (15 to 30 km) apart; thickness 140 to 270 ft (40 to 80 m). Total thickness of map unit 170 to 290 ft (50 to 90 m). | 01-26-01 | dmu, map unit | 127,229,76 | None | {2D09A5AE-F0AD-462B-84BC-4092CE922275} | Mostly mudstone | high | None | 5 | DAS10 | DAS18 | {CC0F0524-B905-457D-AE22-0D239C84E2BB} |
| 13 | {618FAD19-E700-4C5A-9A3A-5D261F29B646} | map unit | map unit, generic | Km | Km | Km | Mowry Formation | Mowry Formation of Colorado Group | Late and Early Cretaceous | unprovided | Early Cretaceous | Late Cretaceous | Medium-gray, brittle, siliceous shale weathering light-silvery blue to white, commonly with orange stain; contains abundant fish scales locally; commonly forms light colored areas on slopes and commonly supports Lodgepole Pine. Thickness 70 ft (21 m). | 01-26-02 | dmu, map unit | 110,221,66 | None | {2D09A5AE-F0AD-462B-84BC-4092CE922275} | Mostly mudstone | high | None | 5 | DAS11 | {618FAD19-E700-4C5A-9A3A-5D261F29B646} |
| 14 | {B859A15F-6F8C-4A16-90D5-1A0C75F6F46E} | map unit | map unit, generic | Kmfr | Kmfr | Kmfr | Mowry Formation through Fall River Formation | Mowry Formation of Colorado Group through Fall River Formation of Colorado Group | Late and Early Cretaceous | unprovided | Early Cretaceous | Late Cretaceous | Includes, in descending order: Mowry Formation, composed of light silvery bluish gray-weathering, siliceous shale with prominent bentonite beds near top, and locally abundant fish scales; thickness 60 to 110 ft (20 to 35 m); Thermopolis Formation, equivalent to combined Shell Creek, Cyprian (Newcastle/Muddy), and Skull Creek intervals recognized to south and east; composed of gray to black shale with common drab to rusty iron-rich concretionary claystone nodules and lenses throughout, and abundant thin beds of sandstone and siltstone in middle part; thickness 270 to 360 ft (80 to 110 m); Fall River Formation (First Cat Creek Sandstone), composed, in upper part, of 40 to 70 ft (12 to 21 m) of light-yellowish-brown-weathering quartzose, extensively burrowed sandstone with prominent chert-pebble conglomerate, and in lower part, of 300 to 430 ft (90 to 130 m) of black shale with minor thin sandstone and siltstone beds, and phosphatic nodules in lower 30 ft (9 m). Resistivity logs 1 to 3 miles (2 to 5 km) apart are nearly identical, and many markers can be correlated in wells 10 to 20 miles (15 to 30 km) apart. Total thickness of map unit 740 to 800 ft (230 to 240 m). | 01-26-03 | dmu, map unit | 171,242,0 | None | {2D09A5AE-F0AD-462B-84BC-4092CE922275} | Mostly mudstone | medium | None | 5 | DAS10 | DAS18 | {B859A15F-6F8C-4A16-90D5-1A0C75F6F46E} |
| 17 | {D694024A-652E-47D7-91A7-44B232A62F36} | map unit | map unit, generic | Ktf | Ktf | Ktf | Thermopolis and Fall River Formations | Thermopolis Formation and Fall River Formation of Colorado Group | Late and Early Cretaceous | unprovided | Early Cretaceous | Late Cretaceous | Thermopolis Shale composed of dark-bluish gray shale bearing common small ferruginous concretions and occasional thin, white bentonite layers; a medial 25-foot (7.6-m) sandstone interval (Cyprian Sandstone) present on west side of Little Rocky Mountains is not present on the north flank of the mountains; a thin layer of predominantly black, polished chert pebbles forming its upper surface is present regionally within the shale even where sand is absent. Fall River Sandstone, First Cat Creek Sandstone of subsurface usage. Composed, in lower part, of massively bedded, arkosic, coarse-grained sandstone with locally common small “clay pellets”, and composed, in upper part, of dark-gray shale, siltstone, and argillaceous sandstone. Total thickness of combined formations approximately 600 ft (183 m). | 01-26-04 | dmu, map unit | 168,212,0 | None | {FDA3C54D-61D0-4798-ACC3-21A2F1270733} | Mostly sandstone | medium | None | 5 | DAS11 | {D694024A-652E-47D7-91A7-44B232A62F36} |
| 12 | {B8335E2E-0DFC-4DC6-A151-2D816CE826CC} | map unit | map unit, generic | Kk | Kk | Kk | Kootenai Formation | Kootenai Formation | Early Cretaceous | unprovided | Early Cretaceous | Early Cretaceous | Rocky Boy quadrangle: Nonmarine sandstone and mudstone; upper half is variegated dark-red, purple, green, and brown mudstone and siltstone locally interbedded with light-gray to light-brown sandstone; lower half is massive light-gray to light-brown, cross-bedded, chert-bearing “salt-and-pepper” sandstone with interbedded, light-colored siltstone and variegated mudstone; prominent massive, cross-bedded, coarse-grained sandstone at base (Third Cat Creek Sandstone) is locally conglomeratic, containing cobbles and pebbles of quartzite, chert, silicified limestone, and vein quartz. Total thickness 290 to 400 ft (90 to 120 m). Dodson quadrangle: Upper part is 25 ft (7.6 m) of coarse-grained arkosic sandstone; middle part is 85 ft (26 m) of variegated maroon, green, and tan, commonly mottled mudstones with interbedded, laterally discontinuous light-gray sandstones and mudstones; lower part is 80 ft (24 m) of tan, coarse grained, arkosic, thick-bedded, chert-bearing, locally cross-stratified, locally conglomeratic sandstone with light-gray shale interbeds; bed of light-gray, dense limestone at base. Total thickness 190 ft (58 m). | 01-27 | dmu, map unit | 94,203,47 | None | {2D09A5AE-F0AD-462B-84BC-4092CE922275} | Mostly mudstone | high | None | 5 | DAS10 | DAS11 | DAS18 | {B8335E2E-0DFC-4DC6-A151-2D816CE826CC} |
| 2 | {A4732846-F5E2-4768-8822-4F081E4E51D8} | map unit | map unit, generic | Jme | Jme | Jme | Morrison Formation and Ellis Group | Morrison Formation and Ellis Group | Late and Middle Jurassic | unprovided | Middle Jurassic | Late Jurassic | Morrison Formation: 60 to 65 ft (18 to 20 m) exposed on small domes on south side of Little Rockies. Swift Sandstone contains primarily light- and dark-gray shale with calcareous concretions; some glauconitic sandstone beds in upper part; abundant silicified Belemnites in lower part; about 240 ft (73 m) thick. Rierdon Formation composed of light to dark gray, clayey limestone that weathers white or light-buff; the limestone commonly weathers into rounded, pebble-size fragments that litter outcrop surface; about 140 ft (43 m) thick. Basal formation of Ellis Group, the Piper (Sawtooth) Formation, apparently is absent in Little Rocky Mountains, although a thin sandstone bed at the base of the Rierdon might be a Sawtooth lithology. Estimated total thickness of Jurassic beds approximately 380 ft (116 m). | 01-28 | dmu, map unit | 167,234,167 | None | {AB5A96BE-7478-43F0-8902-44A5D21B9FE7} | Sandstone and mudstone | medium | None | 5 | DAS11 | {A4732846-F5E2-4768-8822-4F081E4E51D8} |
| 19 | {9CD68842-1C5F-4FB5-9236-8EAAD97F383B} | map unit | map unit, generic | Mm | Mm | Mm | Madison Group | Madison Group | Middle and Early Mississippian | unprovided | Middle Mississippian | Early Mississippian | Includes, in descending order: Mission Canyon Formation and Lodgepole Formation, mapped together; exposures limited to uppermost 200 ft (60 m) of Mission Canyon Formation composed of massive, light-gray to dark-gray limestone with abundant lenses and nodules of gray chert; crinoidal and coralline fossils abundant. Total thickness of 650 to 1,050 ft (200 to 320 m), based on subsurface data; thickness variability reflects regional pre-Middle Jurassic erosion. | 01-29 | dmu, map unit | 168,188,229 | None | {9021F571-E5AC-43ED-8540-E3A1F130EC12} | Limestone | high | None | 5 | DAS10 | DAS18 | {9CD68842-1C5F-4FB5-9236-8EAAD97F383B} |
| 20 | {761057B8-5CE5-4D1C-BC3F-D2EDF2AE1CC9} | map unit | map unit, generic | Mmc | Mmc | Mmc | Mission Canyon Formation | Mission Canyon Formation of Madison Group | Middle and Early Mississippian | unprovided | Middle Mississippian | Early Mississippian | Massively bedded, white to light-buff, crystalline to fragmental limestone; locally cross-bedded, with nodules and lenses of cherty material; numerous solution cavities in upper part; forms massive white cliffs surrounding core of Little Rocky Mountains. Thickness about 330 ft (100 m). | 01-29-01 | dmu, map unit | 120,164,197 | None | {9021F571-E5AC-43ED-8540-E3A1F130EC12} | Limestone | high | None | 5 | DAS11 | {761057B8-5CE5-4D1C-BC3F-D2EDF2AE1CC9} |
| 21 | {9ED4FE36-B435-401B-9A8F-E39DEBCA31D5} | map unit | map unit, generic | Mml | Mml | Mml | Lodgepole Formation | Lodgepole Formation of Madison Group | Early Mississippian | unprovided | Early Mississippian | Early Mississippian | Light- to dark-gray-weathering, thin-bedded limestone; locally stained red from weathering of interbedded red shales. Thickness about 800 ft (244 m). | 01-29-02 | dmu, map unit | 185,202,234 | None | {9021F571-E5AC-43ED-8540-E3A1F130EC12} | Limestone | high | None | 5 | DAS11 | {9ED4FE36-B435-401B-9A8F-E39DEBCA31D5} |
| 18 | {620F94F2-40CB-401D-B58B-F112F17FF4CB} | map unit | map unit, generic | MDtm | MDtm | MDtm | Three Forks, Jefferson, and Maywood Formations | Three Forks Formation, Jefferson Formation, and Maywood Formation | Early Mississippian, and Late to Middle Devonian | unprovided | Middle Devonian | Early Mississippian | Includes, in descending order, Three Forks Formation (Mississippian and Devonian), Jefferson Formation (Devonian), and Maywood Formation (Devonian). Three Forks Formation, poorly exposed, consists of light-gray to light-green, calcareous claystone and siltstone. Jefferson Formation has three distinct units: upper unit composed of light-gray to buff, sandy, massively bedded to locally slabby limestone and dolomite; middle unit composed of shale, siltstone, and thinly laminated dolomite and limestone; lower unit composed of dark-gray and brownish gray, finely crystalline limestone that commonly weathers whitish; total Jefferson Formation thickness about 500 ft (152 m). Maywood Formation composed of shale, siltstone, limestone, and dolomite weathering bright-red in upper part, and light-gray, light-green, yellow, and brown in lower part. Lower 5 ft (1.5 m) are pinkish-weathering, silty, platy dolomite. Thickness of total map unit averages 685 ft (209 m) . | 01-30 | dmu, map unit | 141,145,224 | None | {31CBE54B-0B07-457B-8AC5-A73AB365E34C} | Mostly carbonate rock | low | None | 5 | DAS11 | {620F94F2-40CB-401D-B58B-F112F17FF4CB} |
| 22 | {0DC4BB87-FBAF-4FF3-9D34-9F29145FCDE8} | map unit | map unit, generic | Ob | Ob | Ob | Bighorn Formation | Bighorn Formation | Late and Middle Ordovician | unprovided | Middle Ordovician | Late Ordovician | Dolomitic limestone; upper half gray to white, thin-bedded, hard dolomite; lower part massive, dappled, and gray dolomitic limestone with bluish cast locally; weathered surfaces commonly pitted. Thickness about 450 ft (137 m). | 01-31 | dmu, map unit | 229,185,208 | None | {31CBE54B-0B07-457B-8AC5-A73AB365E34C} | Mostly carbonate rock | high | None | 5 | DAS11 | {0DC4BB87-FBAF-4FF3-9D34-9F29145FCDE8} |
| 23 | {6A2A210F-68E7-4F90-A676-B510FD0BDF3B} | map unit | map unit, generic | O_ef | O_ef | OCBef | Emerson Formation and Flathead Formation | Emerson Formation and Flathead Formation | Ordovician and Cambrian | unprovided | Cambrian | Ordovician | Emerson Formation: Upper part: Late Cambrian and probable Early Ordovician age, consists mostly of green shale, thin limestone beds, edgewise intraformational conglomerate, and limestone nodules. Lower part, Middle Cambrian: upper dark-green shale interbedded with thin limestone beds that overlies dark-green shale containing fossils equivalent to those of uppermost part of Meagher; lower part chiefly olive-gray shale interbedded with thin beds of limestone. Flathead Formation: Light-gray, green, and tan sandstone with some interbedded fine-grained conglomerate. Total thickness of map unit approximately 1,010 ft (310 m). | 01-32 | dmu, map unit | 197,137,192 | None | {2D09A5AE-F0AD-462B-84BC-4092CE922275} | Mostly mudstone | low | None | 5 | DAS11 | {6A2A210F-68E7-4F90-A676-B510FD0BDF3B} |
| 68 | {DA81C275-A90C-4994-A6F0-FA0D8D6A9314} | header | header, generic | None | None | None | METAMORPHIC ROCK | METAMORPHIC ROCK | None | None | None | None | None | 02 | dmu, header | None | None | None | None | None | None | 9 | DAS24 | {DA81C275-A90C-4994-A6F0-FA0D8D6A9314} |
| 24 | {424E874B-8580-46A2-B377-6503F7DC1F66} | map unit | map unit, generic | =m | =m | pCBm | metamorphic rock | metamorphic rock | Precambrian | unprovided | Precambrian | Precambrian | Metasedimentary rocks, primarily biotite schist and gneiss; metavolcanic rocks, primarily hornblende gneiss and amphibolite; also younger pre-Belt(?) ferromagnesian rocks forming a few dikes and sills. | 02-01 | dmu, map unit | 129,130,121 | None | {D4C76C58-C1DF-4615-8312-D8BB29A6FBD0} | Regional metamorphic rock, of unspecified origin | medium | None | 5 | DAS11 | {424E874B-8580-46A2-B377-6503F7DC1F66} |
| 69 | {23A9CB84-B969-4FE9-860E-7DAA80C94994} | header | header, generic | None | None | None | IGNEOUS ROCK | IGNEOUS ROCK | None | None | None | None | None | 03 | dmu, header | None | None | None | None | None | None | 9 | DAS24 | {23A9CB84-B969-4FE9-860E-7DAA80C94994} |
| 50 | {CEEDCD15-1213-4AE0-929A-15B598D0DA1F} | map unit | map unit, generic | Tla | Tla | Tla | latite | latite | Eocene | unprovided | Eocene | Eocene | Occurs as dikes, sills, laccoliths and stocks; light gray to brown; fine-grained, felsic, porphyritic; most contains less than 20 percent mafic minerals; phenocrysts of augite ubiquitous; phenocrysts of potassium feldspar, plagioclase, biotite, and hornblende in varying amounts characterize separate varieties; groundmass of feldspar, augite, and quartz; may represent several episodes of intrusion, and postdates most but not all shonkinite-syenite intrusions. | 03-01 | dmu, map unit | 255,10,33 | None | {FEC4C83D-DF31-4E74-9AF1-F0459FF36323} | Intrusive igneous rock | high | None | 5 | DAS10 | DAS18 | {CEEDCD15-1213-4AE0-929A-15B598D0DA1F} |
| 51 | {7DB80C4B-D981-4C83-901F-2DFAD5BC564C} | map unit | map unit, generic | Tmo | Tmo | Tmo | monzonite | monzonite | Eocene | unprovided | Eocene | Eocene | Occurs as dikes, sills, plugs, and stocks; light to dark gray; fine- to medium-grained, locally porphyritic; predominantly mafic; felsic varieties rare; contains potassium feldspar and plagioclase in varying ratios, augite, and subordinate olivine, biotite, and hornblende; lacks quartz, feldspathoidal varieties rare; occurs only in western half of Bears Paw Mountains; postdates most porphyritic latite and shonkinite intrusions, and is cut by porphyritic potassic syenite; fine-grained dikes not mapped separately from porphyritic latite. | 03-02 | dmu, map unit | 188,60,77 | None | {FEC4C83D-DF31-4E74-9AF1-F0459FF36323} | Intrusive igneous rock | high | None | 5 | DAS10 | DAS18 | {7DB80C4B-D981-4C83-901F-2DFAD5BC564C} |
| 52 | {B22D89DA-E318-46F2-9170-BA46C2BD689A} | map unit | map unit, generic | Tmp | Tmp | Tmp | mafic phonolite | mafic phonolite | Eocene | unprovided | Eocene | Eocene | Occurs as flows, flow breccias, agglomerate, dikes, plugs, and thin plant-bearing, water-laid volcanic sediments; red, green, gray, and greenish gray; may be porphyritic, phenocrysts of analcime, augite, biotite, and rare sanidine; occurs only in western Bears Paw Mountains where it forms topographic highs; rests unconformably on older volcanic rocks, but lower part may be interlayered with porphyritic analcime trachyte. Fossil plants indicate middle Eocene age. Maximum thickness about 1,500 ft (460 m). | 03-03 | dmu, map unit | 249,49,4 | None | {C6807901-FC56-440D-A7EB-29682692E1EE} | Extrusive igneous material | high | None | 5 | DAS10 | DAS18 | {B22D89DA-E318-46F2-9170-BA46C2BD689A} |
| 53 | {74AC1CC9-3878-4181-90CF-71F6E2BBA6CA} | map unit | map unit, generic | Tmpi | Tmpi | Tmpi | mafic phonolite, intrusive | afic phonolite, intrusive | Eocene | unprovided | Eocene | Eocene | Occurs as dikes and plugs; gray to greenish gray; fine-grained, porphyritic; phenocrysts of analcime, augite, biotite, and rare sanidine; occurs only in western Bears Paw Mountains; youngest intrusive rock; intrudes part of extrusive equivalent (mafic phonolite,Tmp). | 03-04 | dmu, map unit | 214,0,0 | None | {FEC4C83D-DF31-4E74-9AF1-F0459FF36323} | Intrusive igneous rock | high | None | 5 | DAS10 | DAS18 | {74AC1CC9-3878-4181-90CF-71F6E2BBA6CA} |
| 57 | {4FE09CE3-6066-4C52-AE0C-CB568C80E51C} | map unit | map unit, generic | Tpyr | Tpyr | Tpyr | pyroxenite | pyroxenite | Eocene | unprovided | Eocene | Eocene | Small pyroxenite stocks, dark green to black, coarse-grained, that contain augite and biotite in ratios from 10:1 to 1:1, less than 10 percent total of apatite, potassium feldspar, plagioclase, olivine, and sulfides; transitional to mafic varieties of shonkinite. Pyroxenite stocks only occur in Rocky Boy stock in western Bears Paw Mountains where it is the earliest intrusion; similar biotite pyroxenites with less apatite occur as inclusions in other igneous rocks. | 03-05 | dmu, map unit | 237,101,135 | None | {FEC4C83D-DF31-4E74-9AF1-F0459FF36323} | Intrusive igneous rock | high | None | 5 | DAS10 | DAS18 | {4FE09CE3-6066-4C52-AE0C-CB568C80E51C} |
| 55 | {2F5F12C8-EDAF-4E52-9A32-D7E6AEAA69BD} | map unit | map unit, generic | Tpyf | Tpyf | Tpyf | pyroclastic rock, felsic | pyroclastic rock, felsic | Eocene | unprovided | Eocene | Eocene | Agglomerate, tuff-breccia, lapilli tuff, tuff, water-laid volcanic sediments, and coarse mudflow deposits; contains more than 50 percent fragments of felsic volcanic rocks; inclusions of biotite pyroxenite and Precambrian basement rocks locally abundant; commonly forms lowermost volcanic unit, particularly in northwestern part of Bears Paw Mountains; in part deposited in local early collapse basins; fossil plants and fish indicate middle Eocene age. Maximum thickness about 3,000 ft (900 m). | 03-06 | dmu, map unit | 255,117,25 | None | {C6807901-FC56-440D-A7EB-29682692E1EE} | Extrusive igneous material | high | None | 5 | DAS10 | DAS18 | {2F5F12C8-EDAF-4E52-9A32-D7E6AEAA69BD} |
| 56 | {A0A496F7-8D75-49F5-9ECE-629A5582CB8A} | map unit | map unit, generic | Tpym | Tpym | Tpym | pyroclastic rock, mafic | pyroclastic rock, mafic | Eocene | unprovided | Eocene | Eocene | Agglomerate, tuff breccia, lapilli tuff, tuff, water-laid volcanic sediments, and mudflow deposits; contains more than 50 percent fragments of mafic volcanic rocks; inclusions of biotite pyroxenite and Precambrian basement rocks locally abundant; commonly forms lowermost volcanic unit, particularly in southeastern part of Bears Paw Mountains; in part deposited in local early collapse basins; fossil plants and fish indicate middle Eocene age. Maximum thickness about 3,000 ft (900 m). | 03-07 | dmu, map unit | 247,116,79 | None | {C6807901-FC56-440D-A7EB-29682692E1EE} | Extrusive igneous material | high | None | 5 | DAS10 | DAS18 | {A0A496F7-8D75-49F5-9ECE-629A5582CB8A} |
| 58 | {1573C4DC-9658-4E55-9FB6-BC836585BB20} | map unit | map unit, generic | Tss | Tss | Tss | shonkinite and syenite | shonkinite and syenite | Eocene | unprovided | Eocene | Eocene | Occurs as dikes, sills, laccoliths, plugs, and stocks; gray to black; fine- to coarse-grained, porphyritic and equigranular; mafic mineral content of shonkinite more than 40 percent, mafic syenite 20 to 40 percent, and syenite less than 20 percent; includes subsilicic-alkalic and silicicalkalic varieties; contains augite, biotite, and dominantly potassic feldspar, with or without olivine, plagioclase, nepheline, pseudoleucite, apatite, and analcime or interstitial quartz; many varieties weather to biotite-rich soil with no outcrop; represents several episodes of intrusion, and is the earliest intrusive rock in the eastern Bears Paw Mountains. | 03-08 | dmu, map unit | 201,70,76 | None | {FEC4C83D-DF31-4E74-9AF1-F0459FF36323} | Intrusive igneous rock | high | None | 5 | DAS10 | DAS18 | {1573C4DC-9658-4E55-9FB6-BC836585BB20} |
| 59 | {DB678DFB-3CDF-4760-9A32-884569144D9D} | map unit | map unit, generic | Tsyp | Tsyp | Tsyp | syenite porphyry | syenite porphyry | Eocene | unprovided | Eocene | Eocene | Occurs as dikes, sills, plugs, and stocks; light gray to green; fine- to coarse-grained; may be highly shattered and impregnated by silica veins; locally vuggy, as mapped includes a wide variety of subsilicic-alkalic rocks (pseudoleucite-sodalite tinguaite, nepheline tinguaite, aegirine-nepheline syenite, all restricted to the central and western Bears Paw Mountains) and silicic-alkalic rocks (porphyritic syenite, the only variety of this rock type in the eastern Bears Paw Mountains); fine-grained varieties commonly have phenocrysts of tabular zoned potassium feldspar, and aegirine, with or without psuedoleucite, nepheline, and sodalite, in a fine-grained green or gray groundmass; rock type associated with most sulfide deposits; plug in Rocky Boy stock contains carbonatite vein-dikes; cut by mafic analcime phonolite in western Bears Paw Mountains; in eastern Bears Paw Mountains, generally the youngest rock type with exception of one dike of porphyritic latite. | 03-09 | dmu, map unit | 255,71,86 | None | {FEC4C83D-DF31-4E74-9AF1-F0459FF36323} | Intrusive igneous rock | high | None | 5 | DAS10 | DAS18 | {DB678DFB-3CDF-4760-9A32-884569144D9D} |
| 60 | {9314E549-78CD-4BF8-95F3-F416972C3943} | map unit | map unit, generic | Ttp | Ttp | Ttp | trachyte porphyry | trachyte porphyry | Eocene | unprovided | Eocene | Eocene | Flows and flow breccias of porphyritic latite and quartz latite; light-gray, gray, and brown; green celadonitic alteration is common; phenocrysts of potassium feldspar, plagioclase, augite, hornblende, and biotite; quartz in groundmass only; interlayered with mafic and felsic pyroclastic rocks and mafic flows; as mapped includes some felsic pyroclastic rocks; extrusive equivalent of porphyritic latite (Tla). Maximum thickness about 5,000 ft (1,500 m). | 03-10 | dmu, map unit | 255,112,43 | None | {C6807901-FC56-440D-A7EB-29682692E1EE} | Extrusive igneous material | high | None | 5 | DAS10 | DAS18 | {9314E549-78CD-4BF8-95F3-F416972C3943} |
| 61 | {8687BFE7-C781-4522-9415-D8FE19CCAEAC} | map unit | map unit, generic | Tvf | Tvf | Tvf | volcanic rock, felsic | volcanic rock, felsic | Eocene | unprovided | Eocene | Eocene | Flows and flow breccias of porphyritic latite and quartz latite; light-gray, gray, and brown; green celadonitic alteration is common; phenocrysts of potassium feldspar, plagioclase, augite, hornblende, and biotite; quartz in groundmass only; interlayered with mafic and felsic pyroclastic rocks and mafic flows; as mapped includes some felsic pyroclastic rocks; extrusive equivalent of porphyritic latite (Tla). Maximum thickness about 5,000 ft (1,500 m). | 03-11 | dmu, map unit | 255,61,25 | None | {C6807901-FC56-440D-A7EB-29682692E1EE} | Extrusive igneous material | high | None | 5 | DAS10 | DAS18 | {8687BFE7-C781-4522-9415-D8FE19CCAEAC} |
| 62 | {4A9429DF-A8FD-43A0-90F0-A31CDD001AC7} | map unit | map unit, generic | Tvm | Tvm | Tvm | volcanic rock, mafic | volcanic rock, mafic | Eocene | unprovided | Eocene | Eocene | Flows and flow breccias of phonolite and mafic phonolite; brown, red, and purple; phenocrysts of olivine, augite, biotite, analcime, and rare leucite in groundmass of augite, potassium feldspar, and analcime; natrolite, analcime, and calcite are common alteration products; interlayered with felsic flows and felsic and mafic pyroclastic rocks; as mapped includes some mafic pyroclastic rocks; extrusive equivalents of shonkinite and syenite (Tss), and possibly of monzonite (Tmo). Maximum extrusive thickness about 5,000 ft (1,500 m). | 03-12 | dmu, map unit | 255,76,0 | None | {C6807901-FC56-440D-A7EB-29682692E1EE} | Extrusive igneous material | high | None | 5 | DAS10 | DAS18 | {4A9429DF-A8FD-43A0-90F0-A31CDD001AC7} |
| 71 | {95DEC881-9381-44FC-B44A-04706AC3885C} | header | header, generic | None | None | None | OTHER | OTHER | None | None | None | None | None | 04 | dmu, header | None | None | None | None | None | None | 9 | DAS24 | {95DEC881-9381-44FC-B44A-04706AC3885C} |
| 1 | {09CC1AB1-BC11-4297-BE55-0018C8371E67} | map unit | map unit, generic | af | af | af | artificial fill | artificial fill | Anthropocene | other | Anthropocene | Anthropocene | Man-made deposits of silt, sand, and rock in the Ft. Peck Dam and in spoil heaps (pieces of Bearpaw Formation) from the excavation of the spillway. Numerous smaller highway and railroad embankments are not shown. Thickness of fill in dam is approximately76 m (250 ft). | 04-01 | dmu, map unit | 114,97,87 | None | {C7111710-CE19-44B8-B9AB-DDC248DA8C1B} | "Made" or human-engineered land | high | None | 5 | DAS15 | {09CC1AB1-BC11-4297-BE55-0018C8371E67} |
| 64 | {B85BCC97-DB77-4DE5-9F0D-075061751C48} | map unit | map unit, generic | w | w | w | water | water | Anthropocene | other | Anthropocene | Anthropocene | Bodies of water in reservoirs. | 04-02 | dmu, map unit | 114,188,255 | None | {79B722F5-CAE0-4775-93CE-2B4F31413542} | Water or ice | high | None | 5 | DAS23 | {B85BCC97-DB77-4DE5-9F0D-075061751C48} |