bluuebunny/crossref_metadata_2025 huggingface dataset:
Late Cenozoic volcanism in the St. George basin, Utah
Authors: Hamblin W. Kenneth
Published: November 2007

One of the most spectacular features in the St. George basin is the series of late Cenozoic basaltic flows that were extruded near the base of the Pine Valley Mountains and flowed southward into the ancestral drainage of the Virgin River. These flows are now preserved as south-trending inverted valleys up to 400 ft(120 m) high which stand in bold contrast to the brilliant red and white east-west trending cliffs and slopes formed on the older Mesozoic rocks. The arid climate and sparse vegetation result in excellent exposures of the striking red, white, and black rocks of Utah’s “color country” and provide scenic emphasis for what is one of the most impressive examples of topographic inversion in North America.
Late Cretaceus Mesaverde Group outcrops at Rifle Gap, Piceance Creek Basin, northwestern Colorado
Authors: Lorenzo J. C. , Rutledge A. K.
Published: November 2007

Rifle Gap is accessible by paved road, and, except for the three southernmost flatirons, all the outcrops described here are on public land administered by the Bureau of Land Management(BLM). Permission for access to the private land is obtained from the residence just west of the southern entrance to the gap. From 1–70, take the Rifle exit (Exit 90) and drive north on Colorado 13(take Railroad Avenue through the town of Rifle) to the junction with Colorado 325. Turn right and drive about 4.1 mi (6.6 km), through Rifle Gap, to the Rifle Gap Reservoir dam. This is the stratigraphic base of the section described below.

The area of Rifle Gap is included in the adjacent corners of the Rifle, Rifle Falls, Silt, and Horse Mountain 7½-minute Quadrangles. Figure 1, a simplified topographic map, is updated to include the dam and reservoir. The approximate locations of the sandstone lenses visible from the road are plotted (Fig. 1). Though much of the section can be seen from the road, better views are afforded by scrambling up the valley slopes toview the opposite side with binoculars. The east side of the gap can be reached on foot by crossing Rifle Creek at the bridge just below the spillway to the dam.
Granite-tectonics of the Pikes Peak intrusive center of Pikes Peak composite batholith, Colorado
Authors: Hutchinson Robert M.
Published: November 2007

The site lies within Pike National Forest and doesnot require permission to enter. The only formal requirement is the toll charged at the entrance to the Pikes Peak toll road, which goes all the way to the summit of the peak, elevation 14,110 ft (4,300 m). The hard-bottom dirt road is kept in excellent condition. Twowheel drive vehicles can make the climb, but vehicles with carburetors tuned to low elevations may have trouble reaching the summit. Depending on snow conditions, the toll road is generally open from May 1 to October 31. The Pikes Peak toll road is reached by driving west on U.S. 24 from Colorado Springs to the small town of Cascade, 12 mi (19 km) away (Figs. 1 and 2).A leisurely trip of a single day should be sufficient to observe the geological relationships of the intrusive center.
The geology of Summer Coon volcano near Del Norte, Colorado
Authors: Noblett Jeffrey B. , Loeffler Bruce M.
Published: November 2007

The Summer Coon volcano is located about 6 mi (9.6km) north of Del Norte, Colorado, on the western edge of the San Luis Valley (Fig. 1). The intrusive core and northern half of the volcano can be found on the Twin Mountains and Twin Mountains SE 7¼-minute quadr lies in the Indian Head and Del Norte 7¼-minute quadrangles. To reach the area of the volcanic core, take orado 112 from Del Norte to County Road 33; travel north n 33 about 6.2 mi (9.9 km); turn left on Road A32 (Forest Service road 660), marked by a small sign to "Natural Arch,” and drive into the volcano.

The volcano lies almost entirely within the Rio Grande National Forest and is accessible by dirt roads, which are usually graded for passenger cars. Some areas, especially those that are near the Natural Arch and off the main road, should only be attempted during periods of clement weather or with four-wheel drive. The main road lies close to some of the radiating dikes and to good outcrops of extrusive material; it passes within 0.5 mi (0.8 km) of the heart of the intrusive complex. The round-trip time (from Del Norte) is ahalf-day minimum.
Monument Valley, Arizona and Utah
Authors: Blakey Ronald C. , Baars Donald L.
Published: November 2007

Standing astride the Utah-Arizona border with bronzed shafts of sandstone, the buttes and pinnacles of Monument Valley rise above the high desert floor of the central Colorado Plateau. The valley is tucked into the apex of the southern end of the Monument Upwarp, a large asymmetrical anticline bounded on its southern and eastern margins by the Comb Ridge monocline (Fig. 1). As recently as 35 years ago, no paved roads served the remote region, today three U.S. highways (U.S. 160 running east-west, and U.S. 163 and U.S. 191 running north-south), provide access to the region. But the best way to see Monument Valley is via the back roads that provide access to some spectacular backcountry.

Monument Valley is located within the Navajo Indian Reservation. Travel on paved and main dirt roads is generally unrestricted. However, travel in some areas is restricted and a permit is required for rock collecting or extensive geological study. Inquiries should be addressed Navajo Nation, Window Rock, Arizona 86515.

Monument Valley and vicinity is covered by geologic maps of various scales 1:62,500 (Witkind and Thaden, 1963), 1:96,000 (Baker, 1936), 1:250,000 (U.S.G.S. Iseries, 345, 629, 744, 1003), and 1:500,000(Geological Maps of Utah and Arizona). Witkind and Thaden (1963) have provided the most comprehensive geological report of the region.
Capulin Mountain Volcano and the Raton-Clayton Volcanic Field, northeastern New Mexico
Authors: Stormer John C.
Published: November 2007

The Raton-Clayton Volcanic Field is located on the High Plains of northeastern New Mexico. The field extends for more than 85 mi (137 km) from near Trinidad, Colorado, southeastward through Raton, New Mexico, to Clayton, New Mexico. U.S. 64/87 runs along the axis of the field, and most of the important features can easily be seen from this highway. This is one of the best routes from Texas and Oklahoma to Denver and other cities in Colorado. Capulin Mountain and a few other points can easily be visited while traveling this route without significantly extending the trip. All of the locations described here are on paved highways, accessible with almost any type of vehicle. Most of the land in this area is private or leased state land so that permission must be obtained for collecting and travel off the highways.

Capulin Mountain, a large cinder cone with associated lava flows, is near the center of the volcanic field. The Capulin Mountain National Monument encompasses the cone and 775 surrounding acres (314 ha). The entrance is on New Mexico 325, 3mi (4.8 km) north of the town of Capulin which is on U.S. 64/87, 54 mi (87 km) west of Clayton and 30 mi (48 km) east of Raton. The monument is open all year from 8:00 a.m. to 4:30 p.m. (later during the summer). There is a road spiraling up the cone to the rim of the crater about 1, 000 ft (300 m) above the base. The trail around
Quaternary basalt fields of west-central New Mexico
Authors: Elston Wolfgang E. , Wohletz Kenneth H.
Published: November 2007

The U.S. Geological Survey was only five years old when its director, John Wesley Powell, approved Captain Clarence Dutton’s plan for one field season on Mount Taylor and the Zuni Plateau (Fig. 1). Dutton’s description of west-central New Mexico, published in 1885 as part of the U.S. Geological Survey’s 6th Annual Report, has become a geologic classic, not only for its lucid literary style but also because it laid the foundation of basic geologic concepts. In his account of erosion and uplift, the reader can discern the germ of ideas that would lead Dutton within four years, to the principle of isostasy. In a discussion of mountain building, he contrasted compressional fold belts, such as the Alps and Appalachians, with mountains of western interior North America, in which vertical uplift and rifting had been the principal forces. Finally, he pondered the significance of the great volcanic fields that nearly encircle the Colorado Plateau.

In the Mount Taylor-Zuni area, Dutton recorded a history of volcanism from late Tertiary to late prehistoric time. Basalt predominates; the youngest lavas issued from cones that are still well preserved, and the lava flowed down modern valleys. Older lavas cap mesas (in general, the higher the mesa, the older the cap; see Fig. 2), 2), and many of their vents have been reduced to volcanic necks. There are dozens of small basalt volcanoes in various stages of preservation as well as one large central volcano (Mt. Taylor, elevation 11,389 ft; 3472 m)
Geology of the Butte mining district, Montana
Authors: Zeihen Lester G. , Berg Richard B. , McClernan Henry G.
Published: November 2007

The Butte mining district is in Silver Bow County in southwestern Montana at the intersection of 1-15 and 1-90. The district proper lies north and west of these highways, and most of it is within the business and residential areas of Butte. Because city streets provide access to all of the stops, they are easily accessible by automobile or on foot as shown in Figure 1. The sites described lie on private land and direct access is not practical to most of them; however, because of their large size they can be easily viewed from the public right of way. A pair of binoculars is useful in viewing some of these features. Unfortunately, the best exposures of veins are in the underground workings no longer accessible or in open pits to which access is prohibited.
The Jefferson River Canyon area, southwestern Montana
Authors: Schmidt Christopher , Aram Richard , Hawley David
Published: November 2007

The Jefferson River Canyon area is on an important structural boundary between the Cordilleran thrust belt and the Rocky Mountain foreland (Fig. 1). The features described here reflect the tectonic history of that boundary from late Precambrian through late Cenozoic time. The area is in Jefferson and Madison counties. Most of the features described may be observed along U.S. 10 through the canyon and along the access road to the Lewis and Clark Caverns State Park (Fig. 2). Stops of particular interest discussed in the text are numbered and indexed in Figure 2 with mileages indicated from LaHood Park (bar, restaurant, and sometime gas station and motel) and/or from the intersection of U.S. 10 and the state park access road. The area is located in the center of the Jefferson Island 15-minute Quadrangle.

Many of the features that can be seen across the Jefferson River from U.S. 10 (south side of river) are currently accessible via the abandoned track bed of the Chicago, Milwaukee, St. Paul, and Pacific Railroad. The track bed is easily traversed by most vehicles and may be accessed on the west from County Road 359 at Jefferson Island and on the east from Montana 287 at Sappington. The access route at Jefferson Island is privately owned and the owner (Vernon Shaw of Cardwell) should be contacted for permission.
Upper Ordovician Maquoketa Formation in the Graf Area, eastern Iowa
Authors: Witzke Brian J. , Glenister Brian F.
Published: November 2007

James Hall (1858) was the first to recognize that a shaledominatedinterval, the Hudson River Group, separates the Galena Limestone (Middle-Upper Ordovician) from the overlying Niagara Limestone (Silurian) in eastern Iowa. Hall’s primary exposure of these rocks was located in the Little Maquoketa River Valley near present-day Graf, Iowa. There he observed“orthoceratite beds, ” graptolitic shales, and an abundance of “extremelysmall” fossils. Charles White (1870) named this sequenceof bluish and brownish shales the Maquoketa Shales after “typicallocalities on the Little Maquoketa River about twelve mileswestward from Dubuque” (i.e., near Graf). Joseph James (1890) described a railroad cut exposed in 1886 near the Graf station, which he termed the “typical locality of the shales in Iowa.” Thissame section is accessible today, but has been expanded to thenorthwest by subsequent road construction. Additional descriptions of the Graf section are givn by Calvin and Bain (1900), Thomas (1914), and Tasch (1955).

The Graf section (S½NW¼SW¼Sec.29, T.89N., R.lE., DubuqueCounty) is recognized as the type locality of the Upper Ordovician Maquoketa Formation, although the bulk of the Maquoketa Shale sequence in the area is represented by covered slopes. Access to this section is most convenient from the southon gravel roads that begin 0.5 mi (0, 8 km) west of the intersection of Old U.S. 20 and County Road Y21 (Figs. 1, 2). The Maquoketa Formation throughout the outcrop belt of northeast Iowa is expressed geomorphically as covered slopes to rollingsurfaces
Roadcuts in the St.Francois Mountains, Missouri
Authors: Kisvarsanyi Eva B. , Hebrank Arthur W.
Published: November 2007

This composite site features roadcuts along U.S.67 and Missouri 72 in the eastern St.Francois Mountains, in Madison County, Missouri (Fig. 1).

STOP 1 (NW¼SW¼NE¼Sec.35, T.34N., R.6E.), along U.S.67 is 14.8 mi (23.7 km) south of the junction, west of Farmington, of U.S.67 and Missouri W. It is located on the Fredericktown 7½-minute Quadrangle. Roadcuts at this stop display a basalt-dike swarm in the Precambrian Slabtown Granite.

STOP 2 (NE¼SE¼NW¼Sec.11, T.33N., R.6E.) is along Missouri 72; from STOP 1, proceed 2.7 mi (4.3 km) south on U.S.67, then 1.8 mi (2.9 km) west on Missouri 72 (Fig. 1). Roadcuts at this locality expose the nonconformable contact between Precambrian and Paleozoic rocks in a spectacular manner.

STOP 3 (NE¼NE¼NE¼Sec.9, T.33N., R.6E.) is 1.7 mi (2.7km) west of STOP 2, along Missouri 72 (Fig. 1). It is located on the Rhodes Mountain 7½-minute Quadrangle. This site displays horizontally bedded, channel-fill sediments within basal boulder conglomerate mantling the Precambrian surface.
Johnson Shut-ins
Authors: Hebrank Arthur W. , Kisvarsanyi Eva B.
Published: November 2007

Johnson Shut-ins State Park, W½Sec.16 and NW¼Sec.21, T.33N., R.2E., Reynolds County, Missouri; Johnson Shut-ins7¼-minute Quadrangle. Entrance to the park is from Missouri N(Fig. 1), 13.2 mi (21 km) southwest of its junction with Missouri 21, north of Ironton, Missouri, and 6.2 mi (10 km) northeast of its junction with Missouri 21–49–72, west of Lesterville, Missouri.From the parking lot, walk east on well-marked (paved) trailabout 1800 ft (540 m) to the shut-ins overlook(Fig. 2).The site is on public land.Note State parkrules prohibit defacing or collecting rocks.
Baraboo Quartzite at Skillett Creek, Wisconsin
Authors: Brown B. A.
Published: November 2007

The exposure is on the east side of U.S. 12, 0.3 mi (0.5 km) south of the junction with Wisconsin 159, SW¼, NW¼, Sec. 15, T.–11N., R.6E., North Freedom 7½-minute Quadrangle (Fig. 1). Caution: Traffic on U.S.12 is heavy, and there is a blind curve just north of the outcrop.
Middle Silurian paleoecology; The Raber Fossil Beds, Chippewa County, Michigan
Authors: Milstein Randall L.
Published: November 2007

The Raber Fossil Beds are in Sec.32, 33, 34, T.43N., R.3 E., and to the general public for their unusual scenic appeal. Collectand Sec.3–5, 8–11, T.42N., R.3E., Chippewa County, Michigan; ing of fossil specimens on tate-owned land is discouraged. Pres-Goetzville, Michigan, 7½-minute Quadrangle. The RaberFossil ently, theRaber area is under review as a potential protected Beds are located roughly 1 mi (2 km) south and southeast of the Natural Area. Within such a Natural Area the collecting of specvillage of Raber, on the St. Marys River (Fig.1).

The area is accessible from two points. A trail from near the Privately-owned land surrounding the state property offers Bernard Farm leads in a southeasterly direction 0.5 mi (0.8 km) many tine collecting areas. Permission must be gained from land to the base of a low rock escarpment and follows this escarpment owners prior to entryon their property. for an additional 0.5 mi (0.8 km) where the trail branches and Visitors to the Raber site should prepare themselves adecontinues to the top of the ridge. A second point of access is by quately for hiking through rough, often uneven wooded terrain. means of a road extending directly east of Goetzville which is From early spring to late autumn, biting insects can be passable for approximately 0.5 (0.8 km) into the area. Other bush bothersome. trails into the area are not readily passable by automobiles.

The majority of land in which the Raber Fossil Beds exist is Raber area contains the ruins
Mackinac Island State Park, Michigan
Authors: Milstein Randall L.
Published: November 2007

Mackinac Island State Park, T.40N., R.3W., Mackinac County, Michigan; Cheboygan, Michigan, U.S.G.S. 30 × 60 minute series. Mackinac Island is located 3 mi (5 km) east of St. Ignace, Michigan, in the Straits of Mackinac (Fig. 1). Access to the Island from St. Ignace is provided by Arnold Transit or Star Lines from mid-April to late-December. From Mackinaw City, service is provided by Arnold Transit or Shepler’s Mackinaw Island Ferry from mid-May to mid-October. Service is at least hourly during the summer months. Air charter service is provided by Great Lakes Charters, St. Ignace, or Michigan Airways, Pellston. From December to mid-April, transportation is by Air Charter Service only from the Mackinac County Airport, St. Ignace. No motorized vehicles are permitted on Mackinac Island. On the Island, transportation is available in the form of rental bicycles, horses and horse drawn carriages.
Fort Wayne, Indiana
Authors: Sunderman Jack A.
Published: November 2007

The geology displayed in and around the city of Fort Wayne, Indiana, is interesting and critically important for at least two reasons: (1) a large quarry near the city exposes an unusual variety of Paleozoic strata, some facies of which are not exposed at any other place; and (2) the city is situated at the junction of several Pleistocene glacial features of regional significance (Fig.1).

The largest and most spectacular quarry in northeastern Indiana is the Ardmore Avenue Quarry of May Stone and Sand, Inc., located along Ardmore Avenue in the NE¼Sec.29, T30N., R.12E. on the southwest edge of Fort Wayne (Figs.1), 2). This quarry is one of the two largest and deepest crushed-stone quarries in Indiana, measuring more than 2,000 ft (610 m) across in a northeast-southwest direction and about 271 ft (82 m) deep during the fall of 1983 (Fig.3). The quarry is readily accessible for public viewing from a stand provided by the company on the north side of the quarry. Thisstand allows such an instructive and spectacular view of the quarry that it has become the focal point for most field trips to the area. Those desiring to enter the quarry should direct their inquiries to the Ardmore Avenue office of May Stone and Sand, Inc.

The Ardmore Avenue Quarry is also the focal point for the study of Pleistocene features in this area because of the excellent exposures of a complex Pleistocene section at the top of
The Falls of the Ohio River, Indiana and Kentucky
Authors: Rexroad Carl B. , Powell Richard L.
Published: November 2007

The Falls of the Ohio River is internationally renowned for the profusion of corals and other fossils found in the Devonian beds at this site. Indeed, the earliest paper on its corals was published in Belgium by Rafinesque and Clifford in 1820. Subsequently, about 75 papers have described some 600 fossil species fromthe falls, Other studies have addressed the geomorphology of the area, including in particular the origin and history of the Ohio River and of the falls. The Falls of the Ohio is also important in understanding the Devonian history of southern Indiana and adjacent Kentucky.

In reality a series of rapids, the Falls ofthe Ohio encompassed a stretch of the Ohio River about 2 mi (3.2 km) long between Louisville, Kentucky, onthe south bank of the river, and New Albany, Clarksville, and Jeffersonville, Indiana, on the northern bank (Fig. 1). “In these rapids, the river has a descentof twenty-two and a half feet, … but in no case, has it a perpendicular fall of more than three. At high water, an acceleration of current, not usual to other parts of the river, is all that is perceived; but at low water, it cannot be passed by loaded boats, without great risk and danger” (Lapham, 1828). Therefore, the Falls Cities owe their initial growth and development to the fact that during times of low water, boats following this major artery of westward expansion either had to off-load and portageor had to wait for high water.
The Cuyahoga Valley National Recreation Area, Ohio
Authors: Hannibal Joseph T. , Feldmann Rodney M.
Published: November 2007

The Cuyahoga Valley National Recreation Area is located along the Cuyahoga River Valley between Cleveland and Akron, Ohio (Fig. 1). Major interstate highways, including I–77, 1–80, and I–271, as well as several Ohio state routes, pass near, or The Cuyahoga Valley National Recreation Area contains through, the National Recreation Area. The sites discussed are excellentexposures of several of northeastern Ohio’s classic and located within three parks that are part of the National Recrea-well-studied Paleozoic rock units. In Brecksville Metropark rockstion Area. Although one candrive to each of the three sites, final The Cuyahoga Valley National Recreation Area is located access requires some hiking, primarily along park trails.
Flint Ridge, Ohio
Authors: Carlson Ernest H.
Published: November 2007

Abstarct

Flint Ridge is located in southeastern Licking and western Muskingum counties in east-central Ohio (Fig. 1). Geologicalninterest centers on Flint Ridge State Memorial and a roadcut exposure nearby (Fig. 1, 2). This area can be reached easily from Brownsville by taking 1-70 to the Brownsville exit, if traveling east, or to the Gratiot exit and continuing west on U.S. 40 for 1.9 mi (3 km), if traveling west (Figs. 1), 2). The memorial is situated 3 mi (5 km) north of Brownsville where Licking County Road 668 intersects Flint Ridge Road (Licking County Road 312). Access to the backbone of the ridge is provided by Flint Ridge Road, which runs east and west from the memorial.

The memorial includes a museum (built over a prehistoric Indian quarry), a trail that winds through old flint workings, picnic facilities, and a parking area, It is open from April through October, but closed Mondays. The roadcut exposure is reached by walking 0.2 mi (0.3 km) north of the memorial along Licking County Road 668. No parking is available here, and due to the sharp curve and traffic along the road, caution must be observed at all times. Exposures of flint can also be observed on two tracts of private land if appropriate arrangements are made. The owners are Clayton Mason, in Licking County, 0.9 mi (1.5 km) east of the memorial on Flint Ridge Road, and John Nethers, in western Muskingun County on
Igneous geology of the Wichita Mountains, southwestern Oklahoma
Authors: Gilbert M. C. , Powell B. N.
Published: November 2007

The Wichita Mountains extend for about 65 mi (105 km) northwest from Lawton, Oklahoma (Fig. 1). Four sites are described here: 27—Quartz Mountain State Park in the western part of the Wichita Mountains, near Oklahoma 44A; 28—The Tom Steed Reservoir area, along U.S. 183 in the central Wichita Mountains; 29—French Lake, south of Oklahoma 49; and 30—the Mt. Scott area, north of Oklahoma 49 in the eastern Wichita Mountains. Specific directions to each site are given with the site descriptions.
Great Salt Plains and hourglass selenite crystals, Salt Fork of the Arkansas River, northwest Oklahoma
Authors: Johnson Kenneth S.
Published: November 2007

The Great Salt Plains comprise about 25 mi2 (64 km2) of flat, barren land, naturally encrusted with salt (halite), along the Salt Fork of the Arkansas River (Fig. 1). The salt plains, which also embrace the area where unique hourglass selenite crystals are currently growing, are almost entirely enclosed within the Great Salt Plains National Wildlife Refuge. Located in central Alfalfa County, Oklahoma, the land is about 4 mi (6.4 km) east of Cherokee and just northwest of Jet. Free access by car or bus is permitted at all times during the year to the salt flats in the vicinity of the observation tower on the west (site 1, Fig. 1) and to the dam and state park area in the east (including picnic and camping facilities and cabins). Also, free access by car or bus to the selenite crystal area (site 2, Fig. 1) is permitted through only one gate, which is unlocked from 8 A.M. until 5 P.M. only on Saturdays, Sundays, and holidays from April 1 to October 15 each year. The crystal area is about 1 mi (1.6 km) northeast of this gate and can be reached safely by driving along the specified road across the salt flats. Access to other parts of the Great Salt Plains is restricted by fences; quicksand, at scattered locations on the salt flats, makes trespass in nonauthorized areas hazardous. The area is covered by four 7½-minute quadrangle maps: Cherokee S, Cherokee N, Jet, and Manchester SW. For information concerning the
Shelf to slope facies of the Wapanucka Formation (lower-Middle Pennsylvanian), frontal Ouachita Mountains, Oklahoma
Authors: Grayson Robert C. , Sutherland Patrick K.
Published: November 2007

Two transects examine shelf-to-slope facies relations of the Wapanucka Formation in southeastern Oklahoma near the towns of Pittsburg and Hartshorne (Fig. 1). Detailed directions to several localities along each transect are given in the text.
Depositional and deformational characteristics of the Atoka Formation, Arkoma Basin, and Ouachita frontal thrust belt, Oklahoma
Authors: Houseknecht David W. , Underwood Michael B.
Published: November 2007

Sedimentary facies and structure of the Atoka Formation of the Arkoma basin and Ouachita frontal thrust belt are illustrated by a north-south transect in LeFlore County, Oklahoma.

Locality 1 (94°29—32’W.; 35°12—30"N.; Hackett Quadrangle) is a roadcut on Oklahoma 112, 1.5 mi (2.4 km) south of the village of Pocola (Fig. 1). The Atoka Formation crops out along the Backbone anticline, which is the expression of a thrust fault that ramps to the surface just north of this exposure. The exposed strata are correlative with the ‘Alma’ sandstone of subsurface terminology; in this part of the basin, the Alma is located about 2,650 ft (800 m) below the top and 4,650 ft (1,400 m) above the base of the Atoka Formation. The strata dip 45° to the south.

Locality 2 (94°38—06’W.; 34°49—36’N.; Hodgen Quadrangle) is a roadcut on U.S. 270/59, 1.1 mi (1.8 km) south of the village of Hodgen (Fig. 1). This north-dipping Atoka section is exposed just south of the Choctaw thrust fault (south of the Choctaw fault, the Atoka has been renamed the Lynn Mountain Formation in certain recent publications).

Locality 3 (94°37—37’W.; 34°44—46—N.; Big Cedar Quadrangle) is a roadcut on U.S. 270/59 just south of the village of Stapp. These strata have traditionally been placed within the Johns Valley Shale (Seely, 1963; Hart, 1963), but recent mapping indicates that the turbidites and debris-flow deposits are simply one of several facies associations within the Lynn Mountain Formation (Poole, 1985; McDonald, 1986). The section is slightly overturned to the
Basal sandstone of the Oil Creek Formation in the quarry of the Pennsylvania Glass Sand Corporation, Johnston County, Oklahoma
Authors: McPherson J. G. , Denisen R. E. , Kirkland D. W. , Summers D. M.
Published: November 2007

The basal sandstone of the Oil Creek Formation is well exposed in a quarry located 5 mi (8 km) north northwest of the small town of Mill Creek in Johnston County, Oklahoma (Sec.14, T.1S., R4E.) (Figs. 1 and 2). The quarry is owned by the Pennsylvania Glass Sand Corporation and is about 0.5 mi (0.8 km) west of Oklahoma 7, which passes through Mill Creek and connects with I-35 about 20 mi (32 km) to the west.
Middle Ordovician strata of the Arbuckle and Ouachita Mountains, Oklahoma; Contrasting Lithofacies and biofacies deposited in southern Oklahoma Aulacogen and Ouachita Geosyncline
Authors: Finney Stanley C.
Published: November 2007

Middle Ordovician strata of the Arbuckle and Ouachita Mountains record markedly different depositional settings (Figs. 1, 2). Three localities in the Arbuckles and one in the Ouachitas demonstrate both the vertical sequences of Lithofacies within each area and the contrasts in Lithofacies and biofacies between the two areas.

Localities 1 through 3 (Fig. 1) are in the Arbuckle Mountain region. Locality 1 (Fig. 3) is in the northeastern part of the Arbuckles. It consists of a roadcut exposure along the west side of Oklahoma 99, about 3.5 mi (5.6 km) south of Fittstown, SW¼Sec.12, T.1N., R.6E., Pontotoc County. It is readily accessible and requires no permission to visit. Locality 2 (Fig. 3) is a long roadcut along the west side of the southbound lanes of I-35 on the south flank of the Arbuckle Mountains. It is in the SW¼Sec.25, T.2S., R1E., Carter County, is readily accessible, and requires no permission to visit. Locality 3 (Fig. 3) is at the north end of Criner Hills. It is a small quarry situated in the SW¼SE¼- Sec.9, T.5S., R.1E., Carter County, readily accessible from I-35 and U.S. 70 by well-maintained gravel roads. The quarry is on private land. Permission for access can be obtained from the landowner, Ronald Burns of Ardmore, Oklahoma (405- 657-8262).

Locality 4 (Figs. 1,3) is at the western edge of the Ouachita Mountains. It is the Stringtown Quarry at the north end of Black Knob Ridge, directly north of the town of Stringtown, and situated in the center of
I-35 Roadcuts; Geology of Paleozoic strata in the Arbuckle Mountains of southern Oklahoma
Authors: Fay Robert O.
Published: November 2007

The field-trip site consists of excellent exposures of Paleozoic strata in roadcuts along I-35 through the Arbuckle Mountains of south-central Oklahoma (Figs. 1 and 2). The exposures extend from 11 to 18 mi (18 to 29 km) north of the city of Ardmore, and are in parts of Murray and Carter Counties. Access to the roadcuts is open at all times, but extreme caution must be exercised because the exposures are along the right-of-way of a major 4-lane divided highway. Parking should be on the far right side of the shoulder, and one should not walk upon or cross the highway. If a large group is to examine the exposures, it would be best to park vehicles in the scenic turnouts and hike along the highway shoulders to examine the roadcuts.
Lithostratigraphy and depositional environments of the Springer and lower Golf Course Formations, Ardmore Basin, Oklahoma
Authors: Meek Frederick B. , Elmore R. Douglas , Sutherland Patrick K.
Published: November 2007

The two lower members of the Springer Formation are well exposed in the vicinity of City Lake, located northwest of Ardmore, Oklahoma. The upper member of the Springer Formation and the lower member of the Golf Course Formation are well exposed along Phillips Creek, northwest of Springer, Oklahoma (Fig. 1). Detailed directions to these localities are given in the text.
Geology of the Buffalo River Valley in the vicinity of U.S. 65, Arkansas Ozarks
Authors: Craig William W.
Published: November 2007

U.S. 65 is a major north-south artery across Arkansas. In north-central Arkansas it traverses the Ozark Plateau Province, which represents a stable Paleozoic platform located on the southwest flank of the Ozark Dome and north of the Ouachita trough. In Searcy County the highway crosses the deeply incised valley of the Buffalo River (Fig. 1) about two-thirds of the distance from Harrison to Marshall.
Post-St. Peter Ordovician strata in the vicinity of Allison, Stone County, Arkansas
Authors: Craig William W. , Deliz Michael J.
Published: November 2007

Exposed at Allison are the Ordovician St. Peter Sandstone, Joachim Dolomite, Plattin, Kimmswick, and Fernvale Limestones, and Cason Shale, as well as the Mississippian Boone Formation. A geologic map of the vicinity of Allison is in McFarland and others (1979). The Allison section, along with related exposures, is included in Craig and others (1984). The outcrop consists of two obvious, closely spaced roadcuts, referred to by local geologists as Allison South and Allison West (Fig. 1). Allison South is on Arkansas 9, approximately 4 mi (6 km) north of Mountain View. Allison West is on Arkansas 14, approximately 0.5 mi (0.8 km) west of its junction with Arkansas 9, between the small community of Allison and the entrance to Blanchard Spring Caverns. The roadcuts are in Sec. 14 and 10, T.15N., R.11W. of the Sylamore and Fifty Six 7½-minute Quadrangles, respectively.

Both Allison localities are easily accessible. Neither Arkansas 9 nor 14 is heavily traveled. Ample shoulder space makes these locations ideal for relatively large groups. Parking at Allison South is better on the shoulder west of the highway. A turnout opposite Allison West allows convenient parking there. Allison South provides a nearly complete exposure from uppermost St. Peter Sandstone through Plattin Limestone. Higher rocks are better viewed at Allison West, which exhibits a complete section from uppermost Plattin into the lower part of the Boone Formation.
Crowley’s Ridge, Arkansas
Authors: Guccione M. J. , Prior W. L. , Rutledge E. M.
Published: November 2007

Crowley’s Ridge is an erosional remnant of unconsolidated Tertiary clay, silt, sand, and lignite capped by Pliocene- Pleistocene gravel, sand, and clay, and middle-to-late Pleistocene loess (Haley, 1976). Located in eastern Arkansas and southeast Missouri, Crowley’s Ridge is no more than 11 mi (18 km) wide, but it extends for 186 mi (300 km) from Campbell, Missouri, to Helena, Arkansas (Fig. 1). The ridge stands 100 to 200 ft (30 to 60 m) higher than the adjoining Eastern and Western Lowlands.

Crowley’s Ridge was a divide formed during the Pleistocene, as ancestors of the Mississippi River to the west and the Ohio River to the east of the Ridge eroded Coastal Plain sediments (Call, 189 1; Fisk, 1944) (Fig. 2). At that time the two rivers joined near Simmesport, Louisiana, 404 mi (650 km) south of where they join today. Abundant glacial outwash and a rising sea level contributed to the aggravation of the ancestral Mississippi and Ohio Rivers, causing a decrease in their gradients. This decrease in gradient and tectonic activity along the New Madrid seismic zone may have caused the eastward shift of the Mississippi River, culminating in the cutting of the present channel through the divide at Thebes Gap. Today the Mississippi River joins the Ohio River near Cairo, Illinois, and flows on the east side of the ridge.
Atokan stratigraphy of the Cherry Bend area, north western Arkansas
Authors: Harris Gary D. , Ramsey Dean A. , Zachry Doy L.
Published: November 2007

The Cherry Bend area is astride Arkansas 23 approximately 5 mi (8 km) south of Brashears, Arkansas (Fig. 1, inset), and is immediately north of the east-trending Cass Fault-Monocline System of the northern margin of the Arkoma Basin. Access to the various stops in the Cherry Bend area is from well-maintained forest service roads, and from Arkansas 23, as well as from the Ozark Highland Trail that transects the area from west to east (Fig. 1). The area is contained entirely within the Cass 7½-minute Quadrangle.
I-430 bypass, Little Rock, Arkansas
Authors: McFarland J. D.
Published: November 2007

The 1-430 bypass around the west end of Little Rock, Arkansas, offers a unique section of Paleozoic age rocks demonstrating the various facies and structural styles in the eastern Ouachita Mountains (Stone and McFarland, 198 1). The sections are easy to reach; just drive to Little Rock, Arkansas, on the interstate system and follow the signs to 1-430. The site descriptions are arranged from north to south, starting about 0.8 mi (1.3 km) south of the 1-430 bridge over the Arkansas River.
Igneous rocks at Granite Mountain and Magnet Cove, Arkansas
Authors: Howard J. Michael , Steele Kenneth F.
Published: November 2007

The Granite Mountain area (Fig. 1) is located to the south of Little Rock, Arkansas, just south of the interchange between U.S. 65/167 and 1-30/630. The exposures at Magnet Cove are located along or near Arkansas 51 west of 1-30, about 40 miles southwest of Little Rock.
The Crouse Limestone in north-central Kansas; Lateral changes and paleoecological analysis
Authors: West R. R. , Twiss P. C.
Published: November 2007

Exposures of the Crouse Limestone along 1-70 south and east of Manhattan, Kansas (Fig. 1), illustrate the stratigraphy, structural geology, palaeoecology, and cyclic sedimentation in the Permian rocks of eastern Kansas. This text provides details of four exposures (between mileposts 319 and 305) that emphasize the interrelationships among these four areas of geology.
Ogallala and post-Ogallala sediments of the Southern High Plains, Blanco Canyon and Mt. Blanco, Texas
Authors: Dolliver Paul N. , Holliday Vance T.
Published: November 2007

Blanco Canyon and Mount Blanco are located along the eastern Caprock Escarpment of the Southern High Plains (Llano Estacado) in the Texas Panhandle near Crosbyton, Texas. The Blanco Canyon exposures are along U.S. 82 where it crosses lower Blanco Canyon east of Crosbyton (Fig. 1). Within a distance of 5.5 mi (8.9 km), the highway descends from the High Plains through the Bridwell and Couch Formations (Ogallala Group) to Triassic red beds before climbing back onto the High Plains surface. The route passes near the Bridwell and Couch type sections and is flanked by several excellent roadside exposures. Outcrops at four Blanco Canyon localities are discussed in this chapter. Collectively, they document the buildup and subsequent dissection of the Southern High Plains since late Miocene time.

Mt. Blanco can be reached by traveling north from Crosbyton on Farm Road 651 across the High Plains surface (Backwater Draw Formation). At 7.8 mi (12.5 km) the road descends into Blanco Canyon. Below the escarpment the highway crosses the mouth of Crawfish Creek, a major reentrant of Blanco Canyon. As the road descends the side of the canyon, the white beds of the Blanco Formation are apparent to the left and right just below the reddish sands of the Backwater Draw Formation. After descending into the canyon, turn left (west) on Farm Road 193 and drive 0.7 mi (1.1 km) to Mt. Blanco, which is the conical erosional remnant on the south side of the road.
Middle and Upper Pennsylvanian (Atokan-Missourian) strata in the Colorado River Valley of Central Texas
Authors: Grayson Robert C. , Trite E. L. “Jack”
Published: November 2007

The Middle and Upper Pennsylvanian stratigraphic sequence of Central Texas is exposed in a triangular shaped region that is bisected by the Colorado River (Fig. 1). This succession of strata (Fig. 2) is illustrated in this double-site guide. Site 78 begins in San Saba County near Bend, Texas, where exposures of the Marble Falls Limestone, Smithwick Shale, and lower “Strawn” Group are available for study. Three additional localities in San Saba and Mills counties permit special emphasis on the depositional character of the lower “Strawn” Group. The upper Strawn Group, Site 79, is seen along a transect across the outcrop belt in San Saba and McCulloch Counties. Single localities at opposite ends of the outcrop belt in San Saba and Brown Counties (Fig. 1) further document the various lithologies and stratigraphic relationships of the upper unit.
Beattie Limestone (Lower Permian) of eastern Kansas
Authors: Twiss Page C.
Published: November 2007

The Beattie cyclothem (site 8) is exposed on the north side of a road cut about 325 ft (100 m) west of milepost 317 on 1-70 in the center of NE¼, Sec.26, T.11S., R.8E., Riley County, Kansas (Fig. 1). If traveling eastward, continue to exit 318, pass under 1-70, and return to the road cut (Kansas law prohibits pedestrians from crossing divided highways). Vehicles should be parked off the pavement, and passengers should exit vehicles on the north side. Keep as far as possible from the traffic lane while examining the rocks.

The Cottonwood Limestone Member of the Beattie Limestone (site 9) is exposed on the north side of a road cut at milepost 272 on U.S. 54 about 0.3 mi (0.5 km) east of the Butler County line. The outcrop is near the north edge of SE¼, SW¼, Sec.3, T.26S., R.8E., Greenwood County, Kansas (Fig. 2). Vehicles should be parked on the south side of the highway where the old road enters the present highway.
The middle Comanchean section of Central Texas
Authors: Amsbury David L.
Published: November 2007

The text describes outcrops of Comanchean strata around Lake Travis on the Colorado River between Austin and Marble Falls in central Texas (Fig. 1). The exposures selected are readily accessible and can provide a good understanding of the vertical sequence of Upper Aptian through Middle Albian rock types. Appreciation of the three-dimensional relationships will require study of the listed publications. Many good exposures occur on private property within the region, but most are not indicated in the guide. The geologist in central Texas is well advised to refrain from crossing any fences for any reason without prior permission from the landowner (and land manager, if appropriate).
The lower Tertiary of the Texas Gulf Coast
Authors: Yancey Thomas E. , Yancey Elizabeth S.
Published: November 2007

The lower Tertiary section in the western Gulf Coast is most complete and best exposed in the bluffs of the Brazes River Valley (Figs. 1 and 2), and has received the most study of any area in the state. The low rolling hills of this region provide limited outcrops, so most good exposures are confined to high banks along the Brazes River. Strata dip toward the Gulf of Mexico at uniformly low dips, and exposures gradually shift upsection as one travels downriver. The regular progression upsection continues to the area of Navasota and Hempstead, where Quaternary sediments of the flat-lying coastal plain lap onto the youngest (Miocene age) of the more steeply dipping Tertiary formations. The Brazes Valley was one of the more heavily traveled routes by settlers and explorers, and the Stone City locality (site of the King’s Highway [El Camino Real or Old Spanish Road—OSR] crossing of the Brazes River) was the source of material for the first study of Texas fossils.
Precambrian and Paleozoic stratigraphy; Franklin Mountains, west Texas
Authors: LeMone David V.
Published: November 2007

The Franklin Mountains are located in far West Texas (ElPaso County) and southernmost central New Mexico (Dons Ana County). The range, when including the North Franklin Mountains (north of Anthony Gap), is 23 mi (38 km) long and less than 5 mi (8 km) wide (Fig. 1). It consists of a linear series of north–south-trending, westward-tilted fault blocks, which are bounded on the east and west by major normal faults. Gravity slides are common throughout the range. The mountains are reasonable examples of the basin-and-range structural and physiographic type. The structure is distinctly different from the thrusted (autochthon and three allochthons) Cretaceus sequence of the northern Chihuahuatrough of the Sierra de Juarez to the south in Mexico. The Texas lineament, the major structural feature separating these disparate northern and southern structural styles, if it exists, would pass through downtown El Paso. Access to the area is by 1-10. Three localities are suggested for examination (Fig. 1). Localities 1 and 2 are on paved, public thoroughfares. Locality 3 (Vinton Canyon) maybe reached from 1-10 at Westway, approximately 3 mi (4.8 km) south of the Texas-New Mexico line, byproceeding eastward on a dirt track toward the mountains. A high-clearance vehicle is required.
The southern Guadalupe Mountains, Texas; Permian stratigraphy and Great Plains/Basin and Range structural transition
Authors: McKnight Cleavy L.
Published: November 2007

The Guadalupe Mountains, easternmost of the block-faulted ranges of the Basin and Range at this latitude, expose a classic section of Permian shelf and basin carbonates and elastics (King, 1942, 1948). In a series of panoramic views and roadcuts the southern Guadalupe Mountains in Culberson and Hudspeth counties, Texas, display both the Permian stratigraphic transition of shelf elastics and evaporates to shelf-margin carbonate buildups to basinal elastics and the modern physiographic/structural transition from the relatively undisturbed, flat-lying sedimentary strata of the Great Plains to the tilted and block-faulted rocks of the Basin and Range. The exposures are all located along U.S. 62-180. Stop 1 is located 43 mi (69 km) southwest of Carlsbad, New Mexico; Stop 4, the final locality, is located 37 mi (59 km) farther west, or 96 mi (154 km) east of El Paso, Texas. The immediate field area is shown in Figure 1. The regional geography is shown on the Van Horn, Texas (1975), and Carlsbad, New Mexico (1972), 10 x 2° topographic sheets; geographic place names not shown in Figure 1 may be found on these two maps. The route traverses the South Rector Canyon (1973), Independence Spring (1973), Guadalupe Peak (1973), Guadalupe Pass (1973), Patterson Hills (1973), and Linda Lake South (provisional, 1984) 7½-minute Quadrangles, all in Texas.
Lower Cretaceous of western Trans-Pecos Texas
Authors: Amsbury David L. , Reaser Donald F.
Published: November 2007

The area is accessible from 1-10, U.S. 90, and (from Big Bend National Park) Texas 170. Outcrops of Lower Cretaceous rocks occur along public roads near Kent; south of Sierra Blanca in the Quitman Mountains; southwest of Marfa and north of the Chinati Mountains; and south of Shafter (Fig. 1).
The Davis Mountains volcanic field, west Texas
Authors: Parker Don F.
Published: November 2007

The Davis Mountains are located south of the junction of 1-10 and 1-20 and northwest of Alpine, predominantly in Jeff Davis County, southwestern Texas. The 14 field localities described here are keyed to the schematic cross sections of Figure 1. The field localities vary from roadcut exposures to hillside exposures to scenic panoramas; all were chosen to elucidate important features of Davis Mountains geology. A brief description of the location, the rock units involved, and chief references are given for each locality. K-Ar ages on Figure 1 were recalculated from Parker and McDowell (1979), using new standard decay constants (Steiger and Jager, 1977).
Dikes in Big Bend National Park; Petrologic and tectonic significance
Authors: Price Jonathan G. , Henry Christopher D.
Published: November 2007

Dikes in Big Bend National Park illustrate the petrologic variety and tectonic setting of Tertiary magmatism in Trans-Pecos Texas. Most igneous activity occurred between two major episodes in the tectonic history of western North America: (1) Late Cretaceus to early Eocene Laramide compression and (2) late Oligocene to recent Basin and Range extension. Volumetrically minor magmatism occurred during the initial stage of Basin and Range extension and perhaps during the final stage of Laramide deformation.

The general geology of the park, including aspects of stratigraphy, structure, petrology, and geomorphology, is best described in the treatise by Maxwell and others ( 1967). The 1:62,500-scale geologic map in Maxwell and others’ (1967) volume is also available at many stores in the Big Bend region as part of a nontechnical geologic guide to Big Bend by Maxwell (1968). The 1:250,000-scale geologic map by Barnes (1979) covers the southern part of the Trans–Pecos region. A field trip guidebook by Maxwell and Dietrich (1972) complements these publications. More recent studies have added considerably to our understanding of the tectonics, volcanic stratigraphy, and petrology of the region. Research results are summarized in guidebooks edited by Dickerson and Hoffer (1980), Dickerson and Muehlberger (1985), and Price and others (1986). In addition, details of the tectonic and magmatic history of the Trans–Pecos region are provided by Henry and Price (1984, 1985, 1986), Price and Henry (1984), and Price and others (1987).

This chapter describes localities for examining dikes in Big Bend National Park (Fig. 1). These dikes represent