Search USGS⌕ Search

SEARCH · Search USGS

Results for “Quaternary”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,009 records · Page 56Linked to original sources
USGS2002

Geologic map of the Yucca Mountain region, Nye County, Nevada

Yucca Mountain, Nye County, Nev., has been identified as a potential site for underground storage of high-level radioactive waste. This geologic map compilation, including all of Yucca Mountain and Crater Flat, most of the Calico Hills, western Jackass Flats, Little Skull Mountain, the Striped Hills, the Skeleton Hills, and the northeastern Amargosa Desert, portrays the geologic framework for a saturated-zone hydrologic flow model of the Yucca Mountain site. Key geologic features shown on the geologic map and accompanying cross sections include: (1) exposures of Proterozoic through Devonian strata inferred to have been deformed by regional thrust faulting and folding, in the Skeleton Hills, Striped Hills, and Amargosa Desert near Big Dune; (2) folded and thrust-faulted Devonian and Mississippian strata, unconformably overlain by Miocene tuffs and lavas and cut by complex Neogene fault patterns, in the Calico Hills; (3) the Claim Canyon caldera, a segment of which is exposed north of Yucca Mountain and Crater Flat; (4) thick densely welded to nonwelded ash-flow sheets of the Miocene southwest Nevada volcanic field exposed in normal-fault-bounded blocks at Yucca Mountain; (5) upper Tertiary and Quaternary basaltic cinder cones and lava flows in Crater Flat and at southernmost Yucca Mountain; and (6) broad basins covered by Quaternary and upper Tertiary surficial deposits in Jackass Flats, Crater Flat, and the northeastern Amargosa Desert, beneath which Neogene normal and strike-slip faults are inferred to be present on the basis of geophysical data and geologic map patterns. A regional thrust belt of late Paleozoic or Mesozoic age affected all pre-Tertiary rocks in the region; main thrust faults, not exposed in the map area, are interpreted to underlie the map area in an arcuate pattern, striking north, northeast, and east. The predominant vergence of thrust faults exposed elsewhere in the region, including the Belted Range and Specter Range thrusts, was to the east, southeast, and south. The vertical to overturned strata of the Striped Hills are hypothesized to result from successive stacking of three south-vergent thrust ramps, the lowest of which is the Specter Range thrust. The CP thrust is interpreted as a north-vergent backthrust that may have been roughly contemporaneous with the Belted Range and Specter Range thrusts. The southwest Nevada volcanic field consists predominantly of a series of silicic tuffs and lava flows ranging in age from 15 to 8 Ma. The map area is in the southwestern quadrant of the southwest Nevada volcanic field, just south of the Timber Mountain caldera complex. The Claim Canyon caldera, exposed in the northern part of the map area, contains thick deposits of the 12.7-Ma Tiva Canyon Tuff, along with widespread megabreccia deposits of similar age, and subordinate thick exposures of other 12.8- to 12.7-Ma Paintbrush Group rocks. An irregular, blocky fault array, which affects parts of the caldera and much of the nearby area, includes several large-displacement, steeply dipping faults that strike radially to the caldera and bound south-dipping blocks of volcanic rock. South and southeast of the Claim Canyon caldera, in the area that includes Yucca Mountain, the Neogene fault pattern is dominated by closely spaced, north-northwest- to north-northeast-striking normal faults that lie within a north-trending graben. This 20- to 25-km-wide graben includes Crater Flat, Yucca Mountain, and Fortymile Wash, and is bounded on the east by the 'gravity fault' and on the west by the Bare Mountain fault. Both of these faults separate Proterozoic and Paleozoic sedimentary rocks in their footwalls from Miocene volcanic rocks in their hanging walls. Stratigraphic and structural relations at Yucca Mountain demonstrate that block-bounding faults were active before and during eruption of the 12.8- to 12.7-Ma Paintbrush Group, and significant motion on these faults continued unt

IMAP↗
USGS1978

Geologic map of the Boulder-Fort Collins-Greeley area, Colorado

This digital map shows the geographic extent of rock stratigraphic units (formations) as compiled by Colton in 1976 under the Front Range Urban Corridor Geology Program. Colton used his own geologic mapping and previously published geologic maps to compile one map having a single classification of geologic units. The resulting published color paper map (USGS Map I-855-G, Colton, 1978) was intended for land-use planning and to depict the regional geology. In 1997-1999, another USGS project designed to address urban growth issues was undertaken. This project, the USGS Front Range Infrastructure Resources Project, undertook to digitize Colton's map at 1:100,000 scale, making it useable in Geographical Information Systems (GIS). That product is described here. In general, the digitized map depicts in its western part Precambrian igneous and metamorphic rocks, Pennsylvanian and younger sedimentary rock units, major faults, and brecciated zones along an eastern strip (5-20 km wide) of the Front Range. The central and eastern parts of the map (Colorado Piedmont) show a mantle of Quaternary unconsolidated deposits and interspersed outcrops of sedimentary rock of Cretaceous or Tertiary age. A surficial mantle of unconsolidated deposits of Quaternary age is differentiated and depicted as eolium (wind-blown sand and silt), alluvium (river gravel, sand, and silt of variable composition), colluvium, and a few landslide deposits. At the mountain front, north-trending, Paleozoic and Mesozoic formations of sandstone, shale, and minor limestone dip mostly eastward and form folds, fault blocks, hogbacks and intervening valleys. Local dikes and sills of Tertiary rhyodacite and basalt intrude rocks near the range front, mostly in the Boulder area.

Colorado↗
USGS1979

Geologic map of the greater Denver area, Front Range urban corridor, Colorado

This digital map shows the areal extent of surficial deposits and rock stratigraphic units (formations) as compiled by Trimble and Machette from 1973 to 1977 and published in 1979 under the Front Range Urban Corridor Geology Program. Trimble and Machette compiled their geologic map from published geologic maps and unpublished geologic mapping having varied map unit schemes. A convenient feature of the compiled map is its uniform classification of geologic units that mostly matches those of companion maps to the north (USGS I-855-G) and to the south (USGS I-857-F). Published as a color paper map, the Trimble and Machette map was intended for land-use planning in the Front Range Urban Corridor. This map recently (1997-1999) was digitized under the USGS Front Range Infrastructure Resources Project. In general, the mountainous areas in the western part of the map exhibit various igneous and metamorphic bedrock units of Precambrian age, major faults, and fault brecciation zones at the east margin (5-20 km wide) of the Front Range. The eastern and central parts of the map (Colorado Piedmont) depict a mantle of unconsolidated deposits of Quaternary age and interspersed outcroppings of Cretaceous or Tertiary-Cretaceous sedimentary bedrock. The Quaternary mantle comprises eolian deposits (quartz sand and silt), alluvium (gravel, sand, and silt of variable composition), colluvium, and a few landslides. At the mountain front, north-trending, dipping Paleozoic and Mesozoic sandstone, shale, and limestone bedrock formations form hogbacks and intervening valleys.

Colorado↗
USGS1983

Aeromagnetic map of the West Clear Creek roadless area, Coconino and Yavapai Counties, Arizona

The West Clear Creek Roadless Area lies within the Coconino National Forest in central Arizona (fig. 1) and includes parts of Yavapai and Coconino Counties. Camp Verde, the nearest population center, is approximately 7 miles (11 km) west of the area. West Clear Creek canyon begins on the east at the confluence of the incised gorges of Willow Valley and of Clover Creek and is joined toward the west by Black Mountain Canyon. The canyon of West Clear Creek is very rugged; in several places it is more than 1,900 ft (580 m) deep. Creek elevation ranges from 6,100 ft (1,860 m) near the junction with Clover Creek to 3,200 ft (975 m) at the mouth of the canyon. The elevation of peaks and ridges near the canyon range from 4,000 ft (1,220 m) to 7,000 ft (2,135 m). Uplands at the head of Willow Valley and Clover Creek reach elevations up to 7,100 ft (2,165 m) above sea level. The greater part of the surface is underlain by late Tertiary volcanic rocks, mainly alkali olivine basalts. These overlie Lower Per i an sedimentary rocks consisting mostly of dolomite, limestone, and sandstone strata that dip gently westward. Late Tertiary and Quaternary sedimentary rocks and deposits mantle several ridges (terrace gravels) and cover basalt flows in Verde Valley at the west end of the area (Verde Formation). Quaternary alluvial deposits occur in the main West Clear Creek drainage and its larger tributaries at the west end of the area.

Arizona↗
USGS2002

Geologic Map of the Sheep Hole Mountains 30' x 60' Quadrangle, San Bernardino and Riverside Counties, California

This data set describes and maps the geology of the Sheep Hole Mountains 30' x 60' quadrangle in southern California. The quadrangle covers an area of the Mojave Desert characterized by desert ranges separated by broad basins. Ranges include parts of the Old Woman, Ship, Iron, Coxcomb, Pinto, Bullion, and Calumet mountains as well as Lead Mountain and the Kilbeck Hills. Basins include part of Ward Valley, part of Cadiz Valley including Cadiz Lake playa, and broad valleys occupied by the Bristol Lake and Dale Lake playas. Bedrock geologic units in the ranges range in age from Proterozoic to Quaternary. The valleys expose Neogene and Quaternary deposits. Proterozoic granitoids in the quadrangle include the Early Proterozoic Fenner Gneiss, Kilbeck Gneiss, Dog Wash Gneiss, granite of Joshua Tree, the (highly peraluminous granite) gneiss of Dry Lakes valley, and a Middle Proterozoic granite. Proterozoic supracrustal rocks include the Pinto Gneiss of Miller (1938) and the quartzite of Pinto Mountain. Early Proterozoic orogeny left an imprint of metamorphic mineral assemblages and fabrics in the older rocks. A Cambrian to Triassic sequence deposited on the continental shelf lies above a profound nonconformity developed on the Proterozoic rocks. Small metamorphosed remnants of this sequence in the quadrangle include rocks correlated to the Tapeats, Bright Angel, Bonanza King, Redwall, Bird Spring, Hermit, Coconino, Kaibab, and Moenkopi formations. The Dale Lake Volcanics (Jurassic), and the McCoy Mountains Formation of Miller (1944)(Cretaceous and Jurassic?) are younger Mesozoic synorogenic supracrustal rocks in the quadrangle. Mesozoic intrusions form much of the bedrock in the quadrangle, and represent a succession of magmatic arcs. The oldest rock is the Early Triassic quartz monzonite of Twentynine Palms. Extensive Jurassic magmatism is represented by large expanses of granitoids that range in composition from gabbro to syenogranite. They include the Virginia May Quartz Monzonite and other members of the Bullion Intrusive Suite, the Chubbock Porphyry, and rocks that form the Goat Basin pluton, Music Valley pluton, and Ship Mountains pluton. The Jurassic plutons range in emplacement depths from mid-crustal to hypabysasal. Mafic and felsic dikes that probably are part of the Late Jurassic Independence dike swarm intrude the Jurassic batholithic rocks. A Mesozoic ductile fault (tectonic slide), the Scanlon thrust, places an inverted sequence of lower Paleozoic rocks and their Proterozoic basement over a lower plate of younger Paleozoic and Triassic rocks. The lower- plate rocks are internally sliced and folded. They in turn are superposed along an attenuation tectonic slide, the Kilbeck fault, over highly strained tectonic schist. The major tectonic slides and associated fabrics are cut by Late Cretaceous batholithic rocks. Widespread Late Cretaceous granitoids assigned to the Cadiz Valley batholith and the Old-Woman Piute Range batholith together form a contiguous super-unit of granite and granodiorite compositions. The Old- Woman Piute Range batholith includes the granite of Sweetwater Wash in the Painted Rock pluton and the Old Woman Mountains Granodiorite forming the Old Woman pluton. The large Cadiz Valley batholith is divided into the Iron Mountains Intrusive Suite and the Coxcomb Intrusive Suite. The Iron Mountains Intrusive Suite includes the Granite Pass Granite (which forms the Granite Pass pluton), the Danby Lake Granite Gneiss, and the Iron Granodiorite Gneiss. The Coxcomb Intrusive Suite consists of many units including the Clarks Pass Granodiorite, the Sheep Hole Mountains Granodiorite (forms the Sheep Hole Mountains pluton), and the Sheep Hole Pass Granite (forms the Sheep Hole Pass pluton). The Cretaceous rocks were emplaced at a range of deep to shallow depths, and their intrusion resulted in an aureole 2-3 km wide in older rocks. Mylonitic fabrics developed through a thickness of >1.3 km, together

Miscellaneous Field Studies Map↗
USGS2001

Geologic map of the Clifton Quadrangle, Mesa County, Colorado

1:24,000-scale geologic mapping in the Clifton 7.5' quadrangle, in support of the USGS Colorado River/I-70 Corridor Cooperative Geologic Mapping Project, provides interpretations of the Quaternary stratigraphy and geologic hazards in this area of the Grand Valley. The Clifton 1:24,000 quadrangle is in Mesa County in western Colorado. Because the map area is dominated by various surficial deposits, the map depicts 16 different Quaternary units. Five prominent river terraces are present in the quadrangle containing gravels deposited by the Colorado River. The map area contains a large landslide deposit on the southern slopes of Mount Garfield. The landslide developed in the Mancos Shale and contains large blocks of the overlying Mesaverde Group. In addition, the landslide is a source of debris flows that have closed I-70 in the past. The major bedrock unit in the quadrangle is the Mancos Shale of Upper Cretaceous age. The map is accompanied by text containing unit descriptions, and sections on geologic hazards (including landslides, piping, gullying, expansive soils, and flooding), and economic geology (including sand and gravel). A table indicates what map units are susceptible to a given hazard. Approximately 20 references are cited at the end of the report.

Colorado↗
USGS2002

Geologic map of the Eagle Quadrangle, Eagle County, Colorado

The Eagle quadrangle covers an area that straddles the Eagle River and Interstate 70 (I-70) and it includes the town of Eagle, Colo., which is located in the southwestern part of the quadrangle, just south of I-70 and the Eagle River, about 37 km west of Vail, Colo. The map area is part of the I-70 urban corridor, which is experiencing rapid and escalating urban growth. Geologic mapping along this corridor is needed for ongoing land-use planning. A variety of rocks and deposits characterize the map area and areas nearby. Sedimentary rocks present in the map area range in age from Pennsylvanian rocks, which were deposited in the ancestral Eagle basin during the formation of the ancestral Rocky Mountains, to Late Cretaceous rocks that were deposited just prior to the formation of the present Rocky Mountains. The Pennsylvanian rocks in the map area include a thick sequence of evaporitic rocks (Eagle Valley Evaporite). These evaporitic rocks are commonly complexly folded throughout the southern part of the quadrangle where they are exposed. In general, in the central and northern parts of the quadrangle, the sedimentary rocks overlying the evaporite dip gently to moderately northward. Consequently, the youngest sedimentary rocks (Late Cretaceous rocks) are exposed dipping gently to the north in the northern part of the quadrangle; landslide complexes are widespread along the northerly dipping, dip slopes in shaly rocks of the Cretaceous sequence in the northeastern part of the map area. During the Early Miocene, basaltic volcanism formed extensive basaltic flows that mantled the previously deformed and eroded sedimentary rocks. Erosional remnants of the basaltic flows are preserved in the southeastern, west-central, and north-central parts of the map area. Some of these basaltic flows are faulted and downdropped in a manner that suggests they were downdropped in areas where large volumes of the underlying evaporitic rocks were removed from the subsurface, beneath the basaltic rocks, by dissolution or flowage of the evaporite in the subsurface. Quaternary and late Tertiary(?) surficial deposits in the map area consist mainly of Quaternary alluvium and colluvium, late and middle Pleistocene terrace gravels of the Eagle River, Miocene(?) gravel remnants of the ancestral Eagle River and its tributaries, and Pleistocene to recent mass movement deposits that include landslides and debris flows. Potential geologic hazards in the map area include landslides, debris flows, rockfalls, local flooding, ground subsidence, and expansive and corrosive soils.

Colorado↗
USGS2002

Geologic map of the Vail West quadrangle, Eagle County, Colorado

This new 1:24,000-scale geologic map of the Vail West 7.5' quadrangle, as part of the USGS Western Colorado I-70 Corridor Cooperative Geologic Mapping Project, provides new interpretations of the stratigraphy, structure, and geologic hazards in the area on the southwest flank of the Gore Range. Bedrock strata include Miocene tuffaceous sedimentary rocks, Mesozoic and upper Paleozoic sedimentary rocks, and undivided Early(?) Proterozoic metasedimentary and igneous rocks. Tuffaceous rocks are found in fault-tilted blocks. Only small outliers of the Dakota Sandstone, Morrison Formation, Entrada Sandstone, and Chinle Formation exist above the redbeds of the Permian-Pennsylvanian Maroon Formation and Pennsylvanian Minturn Formation, which were derived during erosion of the Ancestral Front Range east of the Gore fault zone. In the southwestern area of the map, the proximal Minturn facies change to distal Eagle Valley Formation and the Eagle Valley Evaporite basin facies. The Jacque Mountain Limestone Member, previously defined as the top of the Minturn Formation, cannot be traced to the facies change to the southwest. Abundant surficial deposits include Pinedale and Bull Lake Tills, periglacial deposits, earth-flow deposits, common diamicton deposits, common Quaternary landslide deposits, and an extensive, possibly late Pliocene landslide deposit. Landscaping has so extensively modified the land surface in the town of Vail that a modified land-surface unit was created to represent the surface unit. Laramide movement renewed activity along the Gore fault zone, producing a series of northwest-trending open anticlines and synclines in Paleozoic and Mesozoic strata, parallel to the trend of the fault zone. Tertiary down-to-the-northeast normal faults are evident and are parallel to similar faults in both the Gore Range and the Blue River valley to the northeast; presumably these are related to extensional deformation that occurred during formation of the northern end of the Rio Grande rift system in Colorado. In the southwestern part of the map area, a diapiric(?) exposure of the Eagle Valley Evaporite exists and chaotic faults and folds suggest extensive dissolution and collapse of overlying bedrock, indicating the presence of a geologic hazard. Quaternary landslides are common and indicate that landslide hazards are widespread in the area, particularly where old slide deposits are disturbed by construction. The late Pliocene(?) landslide that consists largely of a smectitic upper Morrison Formation matrix and boulders of Dakota Sandstone is readily reactivated. Debris flows are likely to invade low-standing areas within the towns of Vail and West Vail where tributaries of Gore Creek issue from the mountains on the north side of the valley.

Miscellaneous Field Studies Map↗
USGS1976

Geologic map of the McCarthy Quadrangle, Alaska

Diverse Quaternary surficial deposits are abundant in the quadrangle. Quaternary processes of deposition and erosion strongly influenced the landscape, producing many of the scenic and physiographic features.

Alaska↗
USGS2000

Geologic map and digital database of the Cougar Buttes 7.5' quadrangle, San Bernardino County, California

The Southern California Areal Mapping Project (SCAMP) of Geologic Division has undertaken regional geologic mapping investigations in the Lucerne Valley area co-sponsored by the Mojave Water Agency and the San Bernardino National Forest. These investigations span the Lucerne Valley basin from the San Bernardino Mountains front northward to the basin axis on the Mojave Desert floor, and from the Rabbit Lake basin east to the Old Woman Springs area. Quadrangles mapped include the Cougar Buttes 7.5' quadrangle, the Lucerne Valley 7.5' quadrangle (Matti and others, in preparation b), the Fawnskin 7.5' quadrangle (Miller and others, 1998), and the Big Bear City 7.5' quadrangle (Matti and others, in preparation a). The Cougar Buttes quadrangle has been mapped previously at scales of 1:62,500 (Dibblee, 1964) and 1:24,000 (Shreve, 1958, 1968; Sadler, 1982a). In line with the goals of the National Cooperative Geologic Mapping Program (NCGMP), our mapping of the Cougar Buttes quadrangle has been directed toward generating a multipurpose digital geologic map database. Guided by the mapping of previous investigators, we have focused on improving our understanding and representation of late Pliocene and Quaternary deposits. In cooperation with the Water Resources Division of the U.S. Geological Survey, we have used our mapping in the Cougar Buttes and Lucerne Valley quadrangles together with well log data to construct cross-sections of the Lucerne Valley basin (R.E. Powell, unpublished data, 1996-1998) and to develop a hydrogeologic framework for the basin. Currently, our mapping in these two quadrangles also is being used as a base for studying soils on various Quaternary landscape surfaces on the San Bernardino piedmont (Eppes and others, 1998). In the Cougar Buttes quadrangle, we have endeavored to represent the surficial geology in a way that provides a base suitable for ecosystem assessment, an effort that has entailed differentiating surficial veneers on piedmont and pediment surfaces and distinguishing the various substrates found beneath these veneers.

California↗
USGS2000

Geophysical constraints on the Virgin River Depression, Nevada, Utah, and Arizona

Gravity and aeromagnetic data provide insights into the subsurface lithology and structure of the Virgin River Depression (VRD) of Nevada, Utah, and Arizona. The gravity data indicate that the Quaternary and Tertiary sedimentary deposits hide a complex pre-Cenozoic surface. A north-northwest-trending basement ridge separates the Mesquite and Mormon basins, as evidenced by seismic-reflection, gravity, and aeromagnetic data. The Mesquite basin is very deep, reaching depths of 8?10 km. The Mormon basin reaches thicknesses of 5 km. Its northern margin is very steep and may be characterized by right steps, although this interpretation could change with additional gravity stations. Most of the young (Quaternary), small-displacement faults trend within 10? of due north and occur within the deeper parts of the Mesquite basin north of the Virgin River. South of the Virgin River, only a few, young, small-displacement faults are mapped; the trend of these faults is more northeasterly and parallels the basement topography and is distinct from that of the faults to the north. The Virgin River appears to follow the margin of the basin as it emerges from the plateau. The high-resolution aeromagnetic data outline the extent of shallow volcanic rocks in the Mesquite basin. The north-northwest alignment of volcanic rocks east of Toquop Wash appear to be structurally controlled because of faults imaged on seismic-reflection profiles and because the alignment is nearly perpendicular to the direction of Cenozoic extension. More buried volcanics likely exist to the north and east of the high-resolution aeromagnetic survey. Broader aeromagnetic anomalies beneath pre-Cenozoic basement in the Mormon Mountains and Tule Springs Hills reflect either Precambrian basement or Tertiary intrusions. These rocks are probably barriers to groundwater flow, except where fractured.

Arizona, Nevada, Utah↗
USGS2001

Surficial geology of the lower Comb Wash, San Juan County, Utah

The surficial geologic map of lower Comb Wash was produced as part of a master’s thesis for Northern Arizona University Quaternary Sciences program. The map area includes the portion of the Comb Wash alluvial valley between Highway 163 and Highway 95 on the Colorado Plateau in southeastern Utah. The late Quaternary geology of this part of the Colorado Plateau had not previously been mapped in adequate detail. The geologic information in this report will be useful for biological studies, land management and range management for federal, state and private industries. Comb Wash is a south flowing ephemeral tributary of the San Juan River, flanked to the east by Comb Ridge and to the west by Cedar Mesa (Figure 1). The nearest settlement is Bluff, about 7 km to the east of the area. Elevations range from 1951 m where Highway 95 crosses Comb Wash to 1291 m at the confluence with the San Juan River. Primary vehicle access to lower Comb Wash is provided by a well-maintained dirt road that parallels the active channel of Comb Wash between Highway 163 and Highway 95. For much of the year this road can be traversed without the aid of four-wheel drive. However, during inclement weather such as rain or snow the road becomes treacherous even with four-wheel drive. The Comb Wash watershed is public land managed by the Bureau of Land management (BLM) office in Monticello, Utah. The semi-arid climate of Comb Wash and the surrounding area is typical of the Great Basin Desert. Temperature in Bluff, Utah ranges from a minimum of –8° C in January to a maximum of 35° C in July with a mean annual temperature of 9.8° C (U.S. Department of Commerce, 1999). The difference between day and nighttime temperatures is as great as 20° C. Between 1928 and 1998, annual rainfall in Bluff averaged 178 mm per year (U.S. Department of Commerce, 1999). Annual rainfall in Comb Wash averaged 240 mm per year from 1991 to 1999 while Bluff received an average of 193 mm for the same 8 year period. Most precipitation is monsoonal, convective storms that bring moisture from the Gulf of Mexico beginning in early July and ending by October. Large frontal storms during December and January are responsible for most winter precipitation (Figure 2). The record from U.S. Geological Survey gauging station number 09379000 operated by the BLM from 1959 through 1968 indicates that Comb Wash flows in direct response to precipitation events. Most daily discharge and peak events occur in late July through September, coinciding with high intensity monsoon thunderstorms. Comb Wash supports a variety of vegetation typical of the Great Basin Desert and the northern desert shrub zone as described by Fowler and Koch (1982). On the lower alluvial terraces, bushes and shrubs dominate the vegetation, including: sagebrush (Artemesia tridentata), rabbitbrush (Chrysothamnus nauseosus), fourwing saltbush (Atriplex canescens), winterfat (Eurotia lanata), greasewood (Sarcobatus vermiculatus), and shadscale (Atriplex concertifolia). Juniper trees (Juniperus osteosperma) can be found on the rocky colluvial slopes near Comb Ridge and on the higher terrace near Cedar Mesa. The floodplain contains an abundance of riparian vegetation including cottonwood (Populus fremontii), willow (Salix exigua), and tamarisk (Tamarix ramosissima). Tamarisk is one of 7 non-native species present in the lower Comb Wash watershed. At least seven known species of noxious weeds have invaded the watershed, including Bermuda grass (Cynodon dactylon), field bindweed (Convolvulus avensis), Canada thistle (Cirsium arvense), Russian knapweed (Centaurea repens), tamarisk and camel thorn (Alhagi pseudalhagi). Of these, tamarisk or salt-cedar has most aggressively colonized the southwestern United States, including the San Juan watershed. Graf (1978) estimates that since the late 19th century, tamarisk has spread at a rate of 20 km per year. Tamarisk first appeared in Comb Wash during the mid to early 20th century based on photographs taken by Gregory in the early 1900’s (Gregory, 1938).

Utah↗
USGS2002

Merged digital aeromagnetic data for the middle Rio Grande and southern Espanola basins, New Mexico

The U. S. Geological Survey (USGS) recently conducted a multi-disciplinary study of the Middle Rio Grande basin (Bartolino and Cole, 2002; Fig. 1). The main purpose of this study was to gain a better multi-dimensional understanding of the basin's hydrogeologic framework and use this new understanding to construct an improved regional ground-water flow model. The Middle Rio Grande basin fill serves as the primary water resource for Albuquerque and surrounding communities (Thorn and others, 1993). It is composed of poorly consolidated, Tertiary to Quaternary sediments, collectively called the Santa Fe Group. These sediments were deposited during the Tertiary to Quaternary development of the Rio Grande rift (Fig. 1, inset). The strata vary in thickness from 1,000 to more than 4,000 m and range from mudstone to conglomerate (Kelley, 1977; May and Russell, 1994).

New Mexico↗
USGS2002

Cruise report RV Moana Wave Cruise M-1-02-GM bathymetry and acoustic backscatter of the mid and outer continental shelf, head of De Soto Canyon, northeastern Gulf of Mexico June 17, through July 9, 2002 Pensacola, FL to Pensacola, FL

The mid to outer continental shelf off Mississippi-Alabama and off northwest Florida were the focus of US Geological Survey (USGS) multibeam echosounder (MBES) mapping cruises in 2000 and 2001, respectively. These areas were mapped to investigate the extent of "deep-water reefs" first suggested by Ludwick and Walton (1957). The reefs off Mississippi and Alabama were initially described in water depths of 60 to 120 m (Ludwick and Walton, 1957) but the 2000 mapping found reef and hardgrounds to be much more extensive than previously thought (Gardner et al., 2001). The persistent trend of reef-like features along the outer shelf of Mississippi-Alabama suggested the trend might continue along the northwest Florida mid and outer shelf so a MBES-mapping effort was mounted in 2001 to test this suggestion. It is critical to determine the accurate location, geomorphology, and types of the ridges and reefs that occur in this region to understand the Quaternary history of the area and to assess their importance as benthic habitats for fisheries. The 2001 survey found a series of shelf-depth platforms with ridges (possibly reefs) constructed on their surfaces (Gardner et al., 2002). The area known as the "head of De Soto Canyon" is the large unmapped region between the 2000 and 2001 mapped areas. The head of De Soto Canyon is an outer shelf zone with a relatively steep western wall and a much gentler eastern wall. It was unknown prior to this cruise whether the reefs of the Mississippi-Alabama shelf continue eastward into the head of De Soto Canyon and connect with the ridges and reefs mapped on the northwest Florida outer shelf. The existence of carbonate-cemented latest Quaternary to Holocene sandstones along the western wall of the head of De Soto Canyon (Shipp and Hopkins, 1978; Benson et al., 1997; W.W. Schroeder, personnel comm., 2002) is of interest because of the potential benthic habitats they may represent. Precisely georeferenced high-resolution mapping of bathymetry is a fundamental first step in the study of an area suspected to be critical benthic habitats. Morphology is thought to be critical to define the distribution of dominant demersal plankton/planktivores communities. Community structure and trophodynamics of demersal fishes of the outer continental shelf of the northeastern Gulf of Mexico presently are focuses of a major USGS research project. A goal of the project is to answer questions concerning the relative roles played by morphology and surficial geology in controlling biological differentiation. Deep-water ridges, reefs, and outcrops are important because they are fish havens and key spawning sites, and are critical habitats for larval, juvenile, and economically important sport/food fishes.

Gulf of Mexico, head Of De Soto Canyon↗
USGS2003

A spatial database of bedding attitudes to accompany Geologic Map of Boulder-Fort Collins-Greeley area, Colorado

This digital map shows bedding attitude data displayed over the geographic extent of rock stratigraphic units (formations) as compiled by Colton in 1976 (U.S.Geological Survey Map I-855-G) under the Front Range Urban Corridor Geology Program. Colton used his own mapping and published geologic maps having varied map unit schemes to compile one map with a uniform classification of geologic units. The resulting published color paper map was intended for planning for use of land in the Front Range Urban Corridor. In 1997-1999, under the USGS Front Range Infrastructure Resources Project, Colton's map was digitized to provide data at 1:100,000 scale to address urban growth issues(see cross-reference). In general, the west part of the map shows a variety of Precambrian igneous and metamorphic rocks, major faults and brecciated zones along an eastern strip (5-20 km wide) of the Front Range. The eastern and central part of the map (Colorado Piedmont) depicts a mantle of Quaternary unconsolidated deposits and interspersed Cretaceous or Tertiary-Cretaceous sedimentary rock outcrops. The Quaternary mantle is comprised of eolian deposits (quartz sand and silt), alluvium (gravel, sand, and silt of variable composition), colluvium, and few landslides. At the mountain front, north-trending, dipping Paleozoic and Mesozoic sandstone and shale formations (and sparse limestone) form hogbacks, intervening valleys, and in range-front folds, anticlines, and fault blocks. Localized dikes and sills of Tertiary rhyodacite and basalt intrude rocks near the range front, mostly in the Boulder area.

Colorado↗
USGS2003

A spatial database of bedding attitudes to accompany Geologic map of the greater Denver area, Front Range Urban Corridor, Colorado

This digital map shows bedding attitude symbols display over the geographic extent of surficial deposits and rock stratigraphic units (formations) as compiled by Trimble and Machette 1973-1977 and published in 1979 (U.S. Geological Survey Map I-856-H) under the Front Range Urban Corridor Geology Program. Trimble and Machette compiled their geologic map from published geologic maps and unpublished geologic mapping having varied map unit schemes. A convenient feature of the compiled map is its uniform classification of geologic units that mostly matches those of companion maps to the north (USGS I-855-G) and to the south (USGS I-857-F). Published as a color paper map, the Trimble and Machette map was intended for land-use planning in the Front Range Urban Corridor. This map recently (1997-1999), was digitized under the USGS Front Range Infrastructure Resources Project (see cross-reference). In general, the mountainous areas in the west part of the map exhibit various igneous and metamorphic bedrock units of Precambrian age, major faults, and fault brecciation zones at the east margin (5-20 km wide) of the Front Range. The eastern and central parts of the map (Colorado Piedmont) depict a mantle of unconsolidated deposits of Quaternary age and interspersed outcroppings of Cretaceous or Tertiary-Cretaceous sedimentary bedrock. The Quaternary mantle is comprised of eolian deposits (quartz sand and silt), alluvium (gravel, sand, and silt of variable composition), colluvium, and few landslides. At the mountain front, north-trending, dipping Paleozoic and Mesozoic sandstone, shale, and limestone bedrock formations form hogbacks and intervening valleys.

Open-File Report↗
USGS2003

Geochemistry of bedrock and glacial deposits in the vicinity of the Bend massive sulfide deposit, north central Wisconsin

In 1998 the U.S. Geological Survey (USGS) initiated a study to examine the natural regional environmental impact of sulfide mineralization exposed to episodic weathering and glaciation. The study focused on the Bend copper-gold massive sulfide deposit located in the Medford District of the Chequamegon National Forest in north central Wisconsin. The Bend massive sulfide deposit is a small, metal-rich sulfide body hosted by Paleoproterozoic metavolcanics. The mineralized horizon subcrops beneath 100-120 feet of glacial cover, and consists of massive pyrite and other sulfides. Bedrock and ore geochemistry are well characterized by analyses of diamond drill core provided to the USGS by Sharpe Energy and Resources. In July 1999, five rotasonic drillholes were completed through the unconsolidated Quaternary sediment, averaging about 100 feet thick, on a transect across the Bend deposit. Nearly continuous core was recovered from the surficial material along with several feet of the underlying bedrock. Samples representing the entire section were analyzed by the USGS to give a two-dimensional representation of element dispersal from the unmineralized bedrock. In addition, one hundred regional till samples were subsampled from the archives of the Quaternary Sediment Laboratory in the University of Wisconsin-Madison Department of Geology and Geophysics. These regional samples were collected mainly from Taylor County, where the Bend deposit is located, as well as contiguous parts of Clark and Marathon Counties. This open file report presents all of the geochemical data collected for this study. Additional publications describing the data in more detail are being completed.

Wisconsin↗
USGS2003

Surficial and bedrock geologic map database of the Kelso 7.5 Minute quadrangle, San Bernardino County, California

This geologic map database describes geologic materials for the Kelso 7.5 Minute Quadrangle, San Bernardino County, California. The area lies in eastern Mojave Desert of California, within the Mojave National Preserve (a unit of the National Parks system). Geologic deposits in the area consist of Proterozoic metamorphic rocks, Cambrian-Neoproterozoic sedimentary rocks, Mesozoic plutonic and hypabyssal rocks, Tertiary basin fill, and Quaternary surficial deposits. Bedrock deposits are described by composition, texture, and stratigraphic relationships. Quaternary surficial deposits are classified into soil-geomorphic surfaces based on soil characteristics, inset relationships, and geomorphic expression. The surficial geology presented in this report is especially useful to understand, and extrapolate, physical properties that influence surface conditions, and surface- and soil-water dynamics. Physical characteristics such as pavement development, soil horizonation, and hydraulic characteristics have shown to be some of the primary drivers of ecologic dynamics, including recovery of those ecosystems to anthropogenic disturbance, in the eastern Mojave Desert and other arid and semi-arid environments.

California↗