IDAHO GEOLOGICAL SURVEY DIGITAL WEB MAP 137 MOSCOW-BOISE-POCATELLO WWW.IDAHOGEOLOGY.ORG PHILLIPS AND WELHAN

CORRELATION OF MAP UNITS GEOLOGIC MAP OF THE MENAN BUTTES QUADRANGLE, Artificial Alluvial Units Eolian Units Mass Movement Volcanic Unit Units Units Units m Qls HOLOCENE JEFFERSON and MADISON COUNTIES, IDAHO Qa Qas Qes Qc 11.43 ka*

LATE Qt Qto Qblg PLEISTOCENE William M. Phillips and John A. Welhan Qg ? Menan Buttes Volcanic Complex QUATERNARY 2011 Qtcb Qtca QtnQQtns tna QtsQQtss tsa Qtu Qtc 126 ka* ? Qto MIDDLE Qa PLEISTOCENE 781 ka* *Stage boundaries of the Pleistocene from Gradstein, F.M., J.G. Ogg, A.G. Smith, Wouter Bleeker, and L.J. Lourens, Qblg 2004, A new geologic time scale, with special reference to Precambrian and Neogene: Episodes v. 27 no. 2, p. 83-100.

Qto Older terrace alluvium of Egin terrace (late? to middle? Pleistocene)— tionary lapilli as large as 2 cm are commonly found about midway down Qblg Qa INTRODUCTION Medium sand and pebbly sand forming extensive fill terrace. Sand largely outer flanks, particularly on the northwest and southeast flanks. Vesicular Qto obsidian but mixed with quartz and rhyolitic lithics near surface. Pebbles lapilli of juvenile basalt are also present. Thin sections of the lapilli average Qa This map depicts bedrock and surficial geological units in the Menan Butte consist of subrounded to rounded quartzite, obsidian, rhyolitic tuff, and 67.4 percent black opaque glass groundmass, 28.7 percent vesicles, 3.9 Qa quadrangle. The area sits on the edge of the eastern Snake River Plain, a basalt (Kuntz, 1979). Generally lies beneath basalt of Little Grassy Butte percent phenocrysts (2.5 percent plagioclase and 1.4 percent olivine), 0.9 major crustal downwarp associated with the Yellowstone hotspot. Late (Qblg). However, about 3 m (10 ft) of coarse fluvial sand correlated with percent palagonite, and 0.2 percent accidental lithics. Miocene–Pliocene rhyolitic volcanic rocks of the Heise Volcanic Field were Egin terrace overlies Qblg in a now-closed landfill in sec. 26, T. 6 N., R. 38 Qa Qa erupted in this portion of the Snake River Plain between 6.62–4.45 Ma as E. (G. Embree in Ferdock, 1987, p. 45). Also, reported to be both under and Qtns Ash tuff of North Menan Butte (late Pleistocene)—Black, thinly laminated Qblg on top of Qblg in the Juniper Buttes area to the northeast (Kuntz , 1979). The to thinly bedded, cross- to planar-bedded, moderately sorted, fine to Qa the hotspot passed beneath the region (Morgan and McIntosh, 2005). At 2.06 Ma, when the hotspot was located near its present position, the Huck- surface northeast of North Menan Butte in sec. 35, T. 6 N., R. 38 E. mapped medium sideromelane ash. Ash has the appearance and consistency of leberry Ridge Tuff was erupted from the Henrys Fork Caldera (Christiansen, as Qes may be a partially dissected portion of Egin Bench covered by Holo- sand. Locally contains small channels, stoss and lee structures, rip-up 2001). In the Menan Buttes quadrangle, both the Heise rhyolites and the cene eolian sand and colluvium. Age of unit uncertain. May partially clasts, armored lapilli, and sag structures. Also occurs as thin interbeds Huckleberry Ridge Tuff are covered by Snake River alluvium and basaltic record high discharge glacial outburst flooding in the headwaters of the within the main tuff unit and at distances well away from the vent. Total Qa lava flows. The map lies at the junction of the two major tributaries of the Henrys Fork during Bull Lake glaciation at ~140 ka (W. Scott quoted in thickness varies with position relative to the northeastward dispersal direc- tion of tephra from the cone. At least 50 m (160 ft) thick on the northeast Qa Snake River. On the north, the Henrys Fork drains highlands largely under- Allison, 2001, p. 18). Water wells indicate minimum thickness of 37 m (120 ft) lain by rhyolitic caldera deposits of the Island Park-Yellowstone area. These in map; thickness is 13-30 m (43-98 ft) in Juniper Buttes area (Kuntz, 1979). flank. Composed of 59.2 percent silderomelane, 34.9 percent open spaces, rocks tend to break down relatively quickly to form sandy alluvium rich in 2.7 percent black tacylyte, 2.9 percent olivine and plagioclase phenocrysts, obsidian. To the east, the South Fork originates in the Grand Teton area 0.4 percent accidental lithics, and trace palagonite. Interpreted to represent underlain by Precambrian, Paleozoic, and Mezosoic rocks. These rocks EOLIAN UNITS dry surge eruptions. North of Menan Butte in an abandoned quarry at SE1/4, NW1/4, sec. 34, T. 6 N., R. 38 E., about 1 m (3 ft) of planar-bedded Qa produce the diverse clast lithologies found in the South Fork. During the Qes Dunes and sand sheets (Holocene)—Loose, tan to brown, medium sand. black tuff is exposed beneath basalt of Little Grassy Butte (unit Qblg). The Qblg course of at least two glaciations at ~140 ka and 25-13 ka (Licciardi and Pierce, 2008), the Snake River transported enormous quantities of gravel Composed of rounded quartz, obsidian, sideromelane, and basaltic tuff tuff is reddened for a thickness of about 30 cm by baking from the basalt. A Qa onto the Snake River Plain (Scott, 1982). In the map, the two streams filled grains. Forms active small dunes and sand sheets on the crater floors of the similar contact can be viewed at SW1/4, SW1/4, sec. 26, T. 6 E., R. 38 E. a subsiding basin with hundreds of feet of alluvium. When basaltic magma Menan Buttes where it is also bedded with pebbly colluvium. At least 6 m The contact between Qblg and about 1 m (3 ft) of the black ash is also erupted into this basin, steam explosions occurred that mixed quenched (20 ft) thick in crater of South Menan Butte. Northeast of North Menan Butte present in the Lower Teton Observation Well #1 (IDWR Permit number in sec. 35, T. 6 N., R. 38 E., silty-sand covers the low-relief surface lying 818955) drilled by the U.S. Bureau of Reclamation in SW1/4, NE1/4, sec. Qa magma with gravel and sand to form the tuff cones of Menan Buttes. These structures are unusual for the Snake River Plain and are among the largest topographically above the active floodplain of Henrys Fork. Parent material 25, T. 6 N., R. 38 E. tuff cones in the world (Ferdock, 1987). Following the formation of the tuff for the Mathon sandy loam soil (Noe, 1981). Undated; assigned a Holocene age based upon regional studies of sand dune activity (Gaylord and others, Qtna Altered tuff of North Menan Butte (late Pleistocene)—Massive, brittle, cones, a voluminous lava flow erupted from Little Grassy Butte about 24 km relatively featureless, orange to brown palagonitic tuff. Found on the south- Qa 2000; Forman and Pierson, 2003, Rittenour and Pearce, 2009). (15 mi) northwest of the map. This flow impinged onto the floodplain of the western rim and locally within the crater; interpreted to form large portion Henrys Fork, causing the stream to move eastward. During the Holocene, of the cone at depth (see cross section A-A’). In contrast to the craggy, alveo- sand carried by northeast-directed winds was trapped in the craters of MASS MOVEMENT UNITS lar weathering of the unaltered tuff, the altered tuff weathers to smooth, Qa Menan Buttes, and formed small dunes and sand sheets on the irregular exfoliating slopes punctuated by occasional accidental basalt clasts. Qa topography of the Little Grassy Butte lavas and on Egin Bench. The Henrys Qc Colluvium (Holocene-late Pleistocene)—Massive, semi-indurated, brown to Composed of about 50 percent orange-yellow palagonite, and medium Qto Fork and South Fork (including small splays such as Texas Slough and tan, sand, cobbles, and pebbles in a clayey matrix. Composed of ash-sized brown sileromelane and black tachylyte coated with palagonite. Qblg Bannock Jim Spring Slough) reworked alluvium and deposited new sideromelane sand and rounded tuff fragments. Thickness 0.5-2.5 m (1.6 - Relative to unaltered ash, pore space has been reduced to about 12 sediments. On June 5, 1976, much of the area flooded when the Teton Dam 8.6 ft). Best developed on flanks of the Menan Buttes. Includes alluvial percent. Contacts between unaltered and altered ash are usually sharp. The Qls failed catastrophically (Thomas and others; 1976). This flood was about 100 Qa fans composed of bedded silt and sand on northeast sides of North and contacts cross bedding and locally show control by fractures. times larger than any historic Snake River flood; hence it provides perspec- South Menan Butte. tive on the effects of exceptionally large prehistoric events (Scott, 1977). Qa South Menan Butte Qls Landslide (Holocene-late Pleistocene)—Rotational slump of older terrace Qts Qa alluvium of Egin (unit Qto) onto the floodplain of Henrys Fork. Scarp has Tuff of South Menan Butte (late Pleistocene)—Indurated, gray-green to SOURCE OF DATA been modified by road construction. brown, poorly sorted, massive to thin bedded, palgonitic, lapilli tuff to fine tuff. Similar to tuff of North Menan Butte except for accidental lithic The map is based upon compilation and consultation of master thesis concentration. Tuff of South Menan Butte contains more than 1.5 times the Qa Qa studies (Ferdock, 1987; Allison, 2001; Creighton, 1982), county soil surveys VOLCANIC ROCKS accidental lithics by volume as tuff of North Menan Butte. Accidental clasts Qblg (Noe, 1981; Jorgensen, 1979), regional geologic mapping (Scott, 1982), are most common on the rim and interior of the crater and tend to be domestic water well logs (available from Idaho Department of Water Qblg Basalt of Little Grassy Butte (late Pleistocene)—Gray to dark-gray, porphyritic concentrated in thin beds with large lapilli of juvenvile vesicular basalt. The Resources at http://www.idwr.idaho.gov/apps/appswell/searchWC.asp), and to nonporphyritic, tube-fed pahoehoe lava flows erupted from Little Grassy basalt lapilli have nearly the same petrographic composition as those of field work conducted in 2007. Butte, about 24 km (15 mi) northwest of Menan Butte quadrangle (Kuntz, North Menan Butte. The accidental clasts range from cobble to sand size for Qa quartzite clasts, and boulder size (as large as 1.5 m) for vesicular basalts. Qto Qa 1979). Consists of rare phenocrysts of olivine (1 mm) and plagioclase (3 mm) in a diktytaxitic groundmass of plagioclase, olivine, and augite crystals Most of the accidentals show signs of breakage. The quartzite-to-basalt ratio DESCRIPTION OF MAP UNITS (<0.5 mm). Pressure ridges and tumuli as much as 9 m (30 ft) in height with is about 4:1. Minor amounts of granite, gneiss, and rhyolitic tuff are also present. Qa well-preserved pahoehoe flow surfaces are surrounded by local accumula- Qtss Ash tuff of South Menan Butte (late Pleistocene)—Black, thinly laminated tions of eolian sediment. Well-drained loam soils have formed on these Qblg to thinly bedded, cross- to planar-bedded, moderately sorted, fine to Qa deposits (Mathon-Modkin-Bondranch complexes; Noe, 1981). Water well A ARTIFICIAL UNIT medium sideromelane ash. Similar to unit Qtna but less common than on logs and exposures at edges of unit indicate flow thicknesses of 2-10 m (6- North Menan Butte. m Artificial fill (Holocene)—Landfill (garbage dump). 35 ft). Paleomagnetic measurements show the unit to have normal polarity B' (Table 1). Unit is undated; possibly 10-20 ka (Kuntz, 1987, quoted in Qtsa Altered tuff of South Menan Butte (late Pleistocene)—Massive, orange to Qa Ferdock, 1987, p. 45). The basalt overlies ash deposits of Menan Butte brown palagonitic tuff, similar to unit Qtna. Restricted to exposures in the m ALLUVIAL UNITS Complex and both underlies and overlies alluvium of Egin Bench (unit Qto; southwestern inner crater but inferred to be more common within the butte Qa Kuntz, 1979). at depth. Qa Alluvium of active channels and floodplain of the Snake River and main Qt tributary streams (Holocene)—Sand, gravel, and sandy silt. On Henrys Menan Volcanic Complex Center Menan Butte Fork and South Teton River, sand consists of quartz, black obsidian and rhyolitic lithic grains while gravel clasts consist of rhyolite, basalt, and lesser The Menan Volcanic Complex consists of phreatomagmatic tuff cones Center Menan Butte is a partially eroded and poorly exposed tuff cone quartzite, sandstone, and granitic cobbles. Thickness <10 m (33 ft). On produced by the injection of basaltic magma into alluvial sediments and covering an area of about 1.8 km2 (1.1 mi2) and rising about 42 m (135 ft) Qa South Fork of Snake River, dominated by hard, well-rounded quartzite m basalts of the Snake River Plain aquifer. Magma quenching and steam above the surrounding landscape. Tuffs from both North and South Menan Qa cobbles with lesser sandstone, basalt and limestone. Forms small islands explosions produced tuffs composed of basaltic glass (sidermelane and Buttes partially bury the cone. It has the largest rim crater diameter of any Qes Qa Qa and bar-tops exposed at low water levels. Subject to flooding and high trachylite), hydrothermally altered glass (palagonite), and phenocrysts of of the Menan Butte Complex structures as well as a unique, late stage water tables during spring and early summer. Parent material for poorly plagioclase and olivine. Fragments of the sediments and basalts underlying agglutinate ring and explosion breccia inferred to mark the position of lava Qtns drained, channeled Haplaquolls soils (Noe, 1981; Jorgensen, 1979). the cones (accidental lithics) together with bombs of quenched basalt and erupted into a small lake. Qa clumps of pebble-sized tephra forming small balls (accretionary lapilli) Qas Alluvium of side streams (Holocene)—Gravel, sand, and sandy silt. Forms Qtc Tuff of Center Menan Butte (late Pleistocene)—Indurated gray-green to Qa were also incorporated into the tuffs. Slumping and faulting of the cones islands, and bar-tops and beaches exposed at low water levels; also consists occurred both during and shortly after eruptions along with hydrothermal tan, lapilli to fine, palagonitic tuff. Bedding is weakly developed, thin to Qa of deposits in numerous relic channels. Thickness <10 m (33 ft). Side alteration of the tuff. The volcanic edifices define a north-northwest- medium, and planar. The tuff grades from coarse lapilli tuff on interior of the 32 Qtn streams of the South Fork of the Snake River are dominated by quartzite trending lineament that probably mirrors basalt dike orientations. Prevail- cone to medium tuff on the outer flanks. Tuffs on the interior of the cone are Qc cobbles and lesser sandstone, metamorphic and granitic rocks, while side ing winds during the eruptions caused the cones to be elongated to the composed of 35 percent fresh black, rounded, scoriaceous to dense lapilli; 2 16 streams of Henrys Fork contain obsidian sands and rhyolite cobbles as well northeast. Mapping and unit descriptions of the Menan Volcanic Complex 10 percent angular to rounded, sand to boulder-sized accidental lithics of Qtn as lesser quartzite, sandstone, and granitic rocks. Subject to flooding and quartzite and dense basalt, and 55 percent tan to dark gray-green ash 14 Qas are taken from the detailed study of Ferdock (1987). Qa high water tables during spring and early summer. matrix. Accretionary lapilli and vesicles within the tuff are rare. Scattered 12 13 Qa The age of Menan Volcanic Complex is not precisely known. It probably on the surface of the tuff beds are large accidental lithics of broken cobbles Qtn 20 Qt 13 Terrace alluvium of the Snake River and tributary streams (late Pleistocene)— falls between 140 and 10 ka. The complex was erupted into water-saturated Qtn Qg of red, green, and white quartzite, and broken boulders of vesicular basalt. Qa Qt Sand and gravel similar in clast composition to unit Qa; forms fill terraces sediments of late Pleistocene age formed from the outwash of glaciers in the 20 Qa separated by 1.5-3 m (5-10 ft) scarps from flood plain and active channels headwaters of the Henrys Fork and South Fork drainages. These glacial Qtcb Explosion breccia of Center Menan Butte (late Pleistocene)— Unconsoli- 5 Qtns 11 Qtn Qa Qa of the Henrys Fork and South Fork of Snake River. Terrace riser height gener- dated lapilli and block-sized, angular clasts of dense black, and red/black Qtns Qt Qas Qas deposits date to the Bull Lake and Pinedale glaciations at ~140 ka and Qa ally increases to the north along the Henrys Fork. Terrace surfaces have ~22-14 ka (Licciardi and Pierce, 2008), indicating an age for the complex scoriaceous basalt fragments, 1-6 cm thick. Shown as stipple pattern where Qc 13 Qa Qa 34 Qtns gentle northwest slope indicating source of most terrace alluvium is South found only within colluvium. Interpreted to be remnants of lava lake 15 2 Qtn of less than 140 ka. This is supported by water well logs showing that ash Qtn Qtn Qa Qas Fork of Snake River. Thickness uncertain because unit cannot be distin- destroyed by explosion. Qtn 23 Qas deposits from the Menan Buttes Complex appear to lie upon alluvial depos- 31 guished from older or younger alluvial units in water well logs. Minimum its of Egin Bench (unit Qto). North of the map, the Egin Bench deposits Qtns 4 Qtca 35 thickness about 10 m (33 ft). Unit interpreted to have been deposited during Agglutinate spatter of Center Menan Butte (late Pleistocene)—Poorly Qc 15 Qas Qas contain black obsidian gravels (Kuntz, 1979) thought to have formed from Qblg Qa exposed, broad, circular mound, 250 m (830 ft) in diameter, 11 m (36 ft) period of waning discharge and stream incision during termination of glacial outburst flooding along the Henrys Fork during the Bull Lake glacia- Qtns 13 Qa Qa Qas Qt high. Composed of oxidized, welded, scoriaceous spatter bombs and 32 Qt Pinedale glaciation at ~13-14 ka. Parent material for the Blackfoot, tion (W. Scott quoted in Allison, 2001, p. 18). The Menan Butte deposits lie Qc 6 pillow lava fragments. Interpreted to be remnants of late-stage spatter Labenzo, Heiseton, and Harston soils (Noe, 1981; Jorgensen, 1979). beneath basalt lava flows erupted from Little Grassy Butte (unit Qblg), Qtna Qas Qtns Qtn Qtna Locally poorly drained with water levels <1.5 m (<5 ft) from surface, as ramparts and pillows formed when magma erupted into small lake occupy- Qtna 3 Qa Qas Qas Qt believed to be ~10-20 ka. 21 Qtn indicated by soils with aquic textures. ing Center Menan Butte. Qtn Qtns Qa North Menan Butte Qg Alluvium of Snake River outwash (late Pleistocene)—Gravel and sand Menan Buttes, Undivided composed dominantly of very hard pink, purple and gray quartzite with Qtn Tuff of North Menan Butte (late Pleistocene)—Indurated, gray-green to Qtns Qtu Tuff of Menan Buttes, undivided (late Pleistocene)—Indurated, gray-green Qes Qtna lesser rhyolite, basalt, sandstone, gneiss, and granitic rocks. Poorly exposed brown, poorly sorted, massive to thin bedded, palgonitic, lapilli tuff to fine Qa to brown, poorly sorted, massive to thin bedded, palagonitic, lapilli to fine Qc Qtns in map. Exposures in nearby gravel pits indicate unit is thickly planar- to tuff. Average grain sizes of tuff decrease from medium to coarse ash on vent Qa Qa tuff. Cannot be reliably correlated with eruptive source. Qtn cross-bedded, separated locally by thin, cross-bedded sand layers. Gravel is interior, to fine ash in distal deposits. Accidental lithics composed of basalt Qa mostly pebble- to cobble-sized, clast-supported, locally normally graded are rare; quartzite and sandstone also decrease in grain size from proximal Qtns Qtn Qtna 12 and imbricated. Gravel framework is filled by fine to medium sand to distal deposits. The concentration of accidental lithics on North Menan Qa Qtn composed of subangular black obsidian, quartzite, quartz and feldspar Butte is the lowest in the Menan Volcanic Complex. Thin sections of tuff Qtn Qas crystals, muscovite, and fragments of basalt and rhyolite. Sand beds are average 56.5 percent angular sideromelane, 27.6 percent pore space, 8.5 Qtn 15 C'' locally black because of high obsidian content. Water well logs suggest Qtn Qtn Qt percent tachylite, 2.6 percent phenocrysts (1.1 percent plagioclase and 1.5 ACKNOWLEDGMENTS Qtns minimum thickness of ~50 m (164 ft). Thickness uncertain because possible percent olivine), 4.3 percent palagonite, and 0.5 percent accidental Qtn Qa We thank the landowners in the area for access to their property. K. 4 older units cannot be reliably separated in water well logs. Unit is part of material. Along the crater rim and more rarely along slopes, cobble- to Qtns 4 Qa Othberg (IGS) and C. Kersey (University of Idaho) assisted with paleomag- Qtn Qtn 5 the regional braided-stream outwash plain deposited during the Pinedale boulder-sized accidental basalt clasts are concentrated by erosional Qc 10 netic sample collection and analysis. G. Embree (BYU-Idaho) led several Qtn Qc Qtn glaciation by meltwaters from the Snake River headwaters (Scott, 1982). processes that remove surrounding tuff. Many of the larger accidental clasts Qtc Qtc helpful field trips to the Menan Buttes Volcanic Complex. Qtn Qtu Qtn Qa OSL ages between 25.2 ka and 12.6 ka (Phillips and others, 2009) are display ventifacting. Where the tuff is well exposed and undisturbed by consistent with cosmogenic surface exposure ages of Pinedale-age redeposition, reverse and normally graded beds are present. Most beds are Qtu Qtc Qa Qas Qa Qtc Qtu Qtc moraines in the Yellowstone headwaters (Licciardi and Pierce, 2008). planar, with rare mantle and cross-bedding structures, and lobate beds of Qtcb unarmored vesicular lapilla interbedded with fine tuff. Armored and accre- Qtc Qts C' Qa Qts 8 Qtc Qtn 7 Qtc Qc Qc A A'' Qas 5,600 North Menan Butte 5,600 A' Qc Qa Qtca Qts Qc 8 Qa slumped vent A' Qc Qa deposits South Menan Butte Qa 5,400 5,400 18 Qc Qtn slumped vent Qes basalt of vent Qtc Qc Qc Qa deposits 21 18 31 Qc Qc 5,200 5,200 4 Qes 3 Qt Central Menan Butte 13 14 Qc Qtna FEET 33 22 22 Qc Qa Qa Qt 17 14 5,000 5,000 6 FEET Qts Qa B Qtn Qa Qtna Qtn Qtc Qts Qts 22 Qc Qa Qblg Qblg Qc Qg 4,000 Qtn Qtsa 4,000 11 22 Qes 17 Qa Qa 12 Qa Qa 50 Qtn sand and gravel gravel and sand Qts 11 Qc Qa Qa sand and gravel ? Qa Qa 4,600 clay 4,600 C Qts Qa Qa Qas 9 sand and gravel clay 23 Qc Qtsa Qa ? basalt gravel and sand 37 ? ? 25 Qa basalt Qc Qa 4,400 ? 4,400 Qtsa Qa Qtss Qa gravel and sand 25 basalt of vent clay Qa Qt Qt Qa ? ? ? Qts Qa Qa 4,200 basalt of vent basalt 4,200 Qa Qa 8 Qts (projected) basalt of vent ? Qg (projected) Qa Qa 5 Qc 12 Qa Qa Qc Qa Qc 4,000 4,000 Qa 11 Qa Qt 33 4x vertical exageration Modified from Ferdock (1987). Qa Qa Qa Qas Qa Qa Qa Qas Qa A'' B B’ Base map scanned from USGS film positive, 1979. Field work conducted 2007. 6,000 6,000 Shaded elevation from 10 m DEM. MN This geologic map was funded in part by the U.S. Geological Survey profile at PLANO ARKER GN MARKET P Topography from aerial photographs by Kelsh plotter and by SCALE 1:24,000 LAKE NE National Cooperative Geologic Mapping Program, maximum plane-table surveys 1951. Aerial photographs taken 1950. 1 0.5 0 1 USGS Award No. 07HQAG0070. 5,800 extent 5,800 0o 39 17o North Menan Butte MILE Digital cartography by Collette Gantenbein,Theresa A. Taylor, Revisions from aerial photographs taken 1976 and other source FEET DEER Loudon R. Stanford, and Jane S. Freed at the Idaho Geological Survey’s data. Map edited 1979. Not field checked. ARKS MENAN 1000 0 1000 2000 3000 4000 5000 6000 7000 P REXBURG BUTTES Digital Mapping Lab. 5,600 5,600 Projection: Idaho coordinate system, east zone (Transverse Mercator). 1927 North American Datum. UTM Grid and KILOMETER Reviewed by J.D. Kauffman, Idaho Geological Survey. 1 0.5 0 1 Qtn 1979 Magnetic North Map version 10-11-2011. 10,000-food grid ticks based on Idaho coordinate system, east RIRIE 5,400 5,400 Declination at Center of Map RIGBY IDAHO Contour interval 10 feet LEWISVILLE zone. PDF (Acrobat Reader) map may be viewed online at Qes Qtna 1000-meter Universal Transverse Mercator grid ticks, zone 11. www.idahogeology.org. slump folds QUADRANGLE ADJOINING QUADRANGLES 5,200 5,200 LOCATION Qtn

5,000 5,000 FEET

REFERENCES FEET Qtna Qblg Qa Qg Qes Qtn Qtn 4,800 4,000 Allison, R.R., 2001, Climatic, volcanic, and tectonic infuences on late Pleisto- Noe, H.R., 1981, Soil survey of Madison County area, Idaho: U.S. Department SYMBOLS of Agriculture, Soil Conservation Service, 128 p., 29 map plates, scale sand and gravel cene sedimentation along the Snake River and in Market Lake: Bonneville, gravel and sand gravel and sand clay 1:24,000. Contact: dashed where approximately located. Jefferson, and Madiison counties, Idaho: Idaho State University M.S. thesis, 4,600 clay 4,600 Phillips, W.M., T.M. Rittenour, and Glenn Hoffmann, 2009, OSL chronology of sand and gravel 153 p. sand and gravel sand and gravel clay Christiansen, R.L., 2001, The Quaternary and Pliocene Yellowstone Plateau late Pleistocene glacial outwash and loess deposits near Idaho Falls, Idaho: Normal fault: ball and bar on downthrown side. basalt basalt basalt Geological Society of America Abstracts with Programs, v. 41, p. 12. 4,400 4,400 volcanic field of Wyoming, Idaho, and Montana: U.S. Geological Survey sand and gravel sand and gravel Professional Paper 729-G, p. G1-G145. Rittenour, Tammy, and H.R. Pearce, 2009, Drought and dune activity in the Strike and dip of tuff. basalt Creighton, D.N., 1982, The geology of the Menan Complex, a group of Idaho Falls dune field, Snake River Plain, southeastern Idaho: Geological 3 basalt basalt 4,200 sand and gravel 4,200 phreastmagmatic constructs in the eastern Snake River Plain, Idaho: The Society of America Abstracts with Programs, v. 41, no. 7, p. 619. Strike and dip of overturned tuff. basalt basalt State University of New York, University at Buffalo M.S. thesis, 76 p. Scott, W.E., 1982, Surficial geologic map of the eastern Snake River Plain and 12 adjacent areas, 111º to 115º W., Idaho and Wyoming: U.S. Geological basalt of vent Ferdock, G.C., 1987, Geology of the Menan Volcanic Complex and related Horizontal tuff. 4,000 4,000 volcanic features, northeastern Snake River Plain, Idaho: Idaho State Survey Miscellaneous Investigation Series Map I-1372, scale 1:250,000. 4x vertical exaggeration. Modified from Ferdock (1987). University M.S. thesis, 171 p., geologic map and cross-sections, scale Scott, W.E., 1977, Geologic effects of flooding from Teton Dam failure, south- Landslide block: slump blocks of tuff (Qtn and Qts) on flanks of North 1:12,000. eastern Idaho: U.S. Geological Survey Open-File Report 77-507, 11 p., 1 and South Menan Buttes. C C'' Forman, S.L., and J. Pierson, 2003, Formation of linear and parabolic dunes on plate, scale 1:48,000. Crater rim. 5,400 5,400 the eastern Snake River Plain, Idaho in the nineteeth century: Geomorphol- Thomas, C.A., H.A. Ray, and W.A. Harenberg, 1976, Teton dam flood of June Central Menan Butte ogy, v. 56, no. 1-2, p. 189-200. 1976, Menan Buttes quadrangle, Idaho: U.S. Geological Survey Hydro- Extent of 1976 Teton Dam flood (Thomas, Ray, and Harenberg, 1976). Gaylord, D.R., J.J. Coughlin, A.J. Coleman, M.R. Sweeney, and R.H. Rutford, logic Investigation HA-570. 5,200 C' 5,200 2000, Holocene sand dune activity and paleoclimates from Sand Creek, St. slumped vent profile at Anthony dune field, Idaho: Geological Soceity of America Abstracts with deposits 5,000 maximum 5,000 Programs, v. 32, no. 5, p. 10. Table 1. Paleomagnetic data for basalt of Little Grassy Butte. extent Qtca Jorgensen, Wendell, 1979, Soil survey of Jefferson County, Idaho: U.S. Depart- Samples are from the Deer Parks quadrangle. Qtc Qtc FEET ment of Agriculture, Soil Conservation Service, 219 p., 66 map plates, Site Demag 4,800 4,000 FEET scale 1:20,000. number* Unit Latitude Longitude n D l α k Polarity level (mT) 95 gravel and sand Kuntz, M.A., 1979, Geologic map of the Juniper Buttes area, eastern Snake clay Qtc sand and gravel 07P020 Qblg 43.82689 -112.04051 7 334.6 67.9 2.6 540.9 N 20 River Plain, Idaho: U.S. Geological Survey Miscellaneous Investigations 4,600 4,600 Map I-1115, scale 1:48,000. 07P021 Qblg 43.81417 -112.00854 8 322.5 64.9 4.0 189.1 N 40 gravel and sand clay basalt Licciardi, J.M., and K.L. Pierce, 2008, Cosmogenic exposure-age chronologies n = number of oriented cores. basalt 4,400 4,400 of Pinedale and Bull Lake glaciations in greater Yellowstone and the Teton D = site mean declination of characteristic remnant magnetism. basalt gravel and sand basalt sand and gravel Range, USA: Quaternary Science Reviews, v. 27, p. 814-831. I = site mean inclination of characteristic remnant magnetism. α 95 = confidence limit for the mean direction at the 95% level. Morgan, L.A., and W.C. McIntosh, 2005, Timing and development of the Heise 4,200 4,200 volcanic field, Snake River Plain, Idaho, western USA: Geological Society k = precision parameter. N = normal polarity. of America Bulletin, v. 117, no. 3/4, p. 288-306. basalt of vent 4,000 4,000 4x vertical exageration Modified from Ferdock (1987).

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