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At least 1,621 records · Page 90Linked to original sources
USGS1997

Ground Water Atlas of the United States: Segment 11, Delaware, Maryland, New Jersey, North Carolina, Pennsylvania, Virginia, West Virginia

Segment 11 consists of the States of Delaware, Maryland, New Jersey, North Carolina, West Virginia, and the Commonwealths of Pennsylvania and Virginia. All but West Virginia border on the Atlantic Ocean or tidewater. Pennsylvania also borders on Lake Erie. Small parts of northwestern and north-central Pennsylvania drain to Lake Erie and Lake Ontario; the rest of the segment drains either to the Atlantic Ocean or the Gulf of Mexico. Major rivers include the Hudson, the Delaware, the Susquehanna, the Potomac, the Rappahannock, the James, the Chowan, the Neuse, the Tar, the Cape Fear, and the Yadkin-Peedee, all of which drain into the Atlantic Ocean, and the Ohio and its tributaries, which drain to the Gulf of Mexico. Although rivers are important sources of water supply for many cities, such as Trenton, N.J.; Philadelphia and Pittsburgh, Pa.; Baltimore, Md.; Washington, D.C.; Richmond, Va.; and Raleigh, N.C., one-fourth of the population, particularly the people who live on the Coastal Plain, depends on ground water for supply. Such cities as Camden, N.J.; Dover, Del.; Salisbury and Annapolis, Md.; Parkersburg and Weirton, W.Va.; Norfolk, Va.; and New Bern and Kinston, N.C., use ground water as a source of public supply. All the water in Segment 11 originates as precipitation. Average annual precipitation ranges from less than 36 inches in parts of Pennsylvania, Maryland, Virginia, and West Virginia to more than 80 inches in parts of southwestern North Carolina (fig. 1). In general, precipitation is greatest in mountainous areas (because water tends to condense from moisture-laden air masses as the air passes over the higher altitudes) and near the coast, where water vapor that has been evaporated from the ocean is picked up by onshore winds and falls as precipitation when it reaches the shoreline. Some of the precipitation returns to the atmosphere by evapotranspiration (evaporation plus transpiration by plants), but much of it either flows overland into streams as direct runoff or enters streams as base flow (discharge from one or more aquifers). The distribution of average annual runoff (fig. 2) is similar to the distribution of precipitation; that is, runoff is generally greatest where precipitation is greatest. Runoff rates range from more than 50 inches per year in parts of western North Carolina to less than 12 inches in parts of North Carolina, Virginia, and West Virginia. Parts of the seven following physiographic provinces are in Segment 11: the Coastal Plain, the Piedmont, the Blue Ridge, the New England, the Valley and Ridge, the Appalachian Plateaus, and the Central Lowland. The provinces generally trend northeastward (fig. 3). The northeastern terminus of the Blue Ridge Province is in south-central Pennsylvania, and the southwestern part of the New England Province, the Reading Prong, ends in east-central Pennsylvania. The topography, lithology, and water-bearing characteristics of the rocks that underlie the Blue Ridge Province and the Reading Prong are similar. Accordingly, for purposes of this study, the hydrology of the Reading Prong is discussed with that of the Blue Ridge Province. The Coastal Plain Province is a lowland that borders the Atlantic Ocean. The Coastal Plain is as much as 140 miles wide in North Carolina but narrows northeastward to New Jersey where it terminates in Segment 11 at the south shore of Raritan Bay. Although it is generally a flat, seaward-sloping lowland, this province has areas of moderately steep local relief, and its surface locally reaches altitudes of 350 feet in the southwestern part of the North Carolina Coastal Plain. The Coastal Plain mostly is underlain by semiconsolidated to unconsolidated sediments that consist of silt, clay, and sand, with some gravel and lignite. Some consolidated beds of limestone and sandstone are present. The Coastal Plain sediments range in age from Jurassic to Holocene and dip gently toward the ocean. The boundary between the Coastal Plain and the Piedmont Provinces is called the Fall Line (fig. 3) because falls and rapids commonly form where streams cross the contact between the consolidated rocks of the Piedmont (fig. 4) and the soft, semiconsolidated to unconsolidated sediments of the Coastal Plain. The increase in stream gradient at the Fall Line provided favorable locations for mills and other installations that harnessed water power during the early years of the Industrial Revolution, and on most major rivers, the Fall Line coincides with the head of navigation. The Piedmont Province is an area of varied topography that ranges from lowlands to peaks and ridges of moderate altitude and relief. The metamorphic and igneous rocks of this province range in age from Precambrian to Paleozoic and have been sheared, fractured, and folded. Included in this province, however, are sedimentary basins that formed along rifts in the Earth's crust and contain shale, sandstone, and conglomerate of early Mesozoic age, interbedded locally with basaltic lava flows and minor coal beds. The sedimentary rocks and basalt flows are intruded in places by diabase dikes and sills. The mountain belt of the Blue Ridge Province forms the northwestern margin of the Piedmont in most of Segment 11. This belt consists mostly of igneous and high-rank metamorphic rocks but also includes low-rank metamorphic rocks of late Precambrian age and small areas of sedimentary rocks of Early Cambrian age along its western margin. In this report, the Reading Prong of the New England Province, which is an upland that extends from east of the Susquehanna River in Pennsylvania northeastward into New Jersey (fig. 3), is treated as part of the Blue Ridge Province. Part of the Reading Prong in Pennsylvania and New Jersey and a small part of the Piedmont Province in northeastern New Jersey have been glaciated. Glacial deposits completely or partly fill some of the valleys, and the eroding action of the glacial ice removed some of the rock from the ridges. Thus, the glaciated parts of the province have a smoother topography and less relief than other parts. The Valley and Ridge Province is characterized by layered sedimentary rock that has been complexly folded and locally thrust faulted. As the result of repeated cycles of uplift and erosion, resistant layers of well-cemented sandstone and conglomerate form elongate mountain ridges and less resistant, easily eroded layers of limestone, dolomite, and shale form valleys. The rocks of the province range in age from Cambrian to Pennsylvanian. Parts of this province from central Pennsylvania into New Jersey have been glaciated, and glacial deposits fill or partially fill some of the valleys. The Appalachian Plateaus Province is underlain by rocks that are continuous with those of the Valley and Ridge Province, but in the Appalachian Plateaus the layered rocks are nearly flat-lying or gently tilted and warped, rather than being intensively folded and faulted. The boundary between the two provinces is a prominent southeast-facing scarp called the Allegheny Front in most of the northern part of Segment 11 (fig_ 5) and the Cumberland Escarpment in the southern part. The scarp faces the Valley and Ridge Province, and throughout most of the segment, the eastern edge of the Appalachian Plateaus Province is higher than the ridges in the Valley and Ridge. Like parts of the Reading Prong and the Valley and Ridge Province, the northern part of the Appalachian Plateaus Province in Pennsylvania has been glaciated. In the glaciated section, the surface is mantled by glacial drift, and the valleys are partly filled with glacial deposits. The northwestern corner of Segment 11 contains a small part of the Central Lowland Province. This flat lowland is underlain by gently dipping sedimentary rocks, some of which are the same geologic formations as those of the Appalachian Plateaus Province. The two provinces are separated by a northwest- facing scarp. Because of the small area of the Central Lowland Province within the segment and the similarity of aquifer properties with those of the glaciated part of the Appalachian Plateaus Province, the two provinces are discussed together in this report.

Delaware, Maryland, New Jersey, North Carolina, Pe↗
USGS1982

Geologic map of the Wenatchee 1:100,000 Quadrangle, central Washington

The rocks and deposits within the Wenatchee quadrangle can be grouped into six generalized units: (1) Precambrian(?) Swakane Biotite Gneiss in the northeastern part of the quadrangle and the probable Jurassic low-grade metamorphic suite, mostly composed of the Easton Schist, in the southwestern part; (2) the Mesozoic Ingalls Tectonic Complex; (3) the Mesozoic Mount Stuart batholith; (4) lower and middle Tertiary nonmarine sedimentary and volcanic rocks; (5) Miocene basalt flows and interbedded epiclastic rocks constituting part of the Columbia River Basalt Group and interbedded silicic volcaniclastic rocks of the Ellensburg Formation; and (6) Pliocene to Holocene alluvium, glacial, flood, and mass-wastage deposits.

IMAP↗
USGS1993

Geologic map of the Palo Alto and part of the Redwood Point 7-1/2' quadrangles, San Mateo and Santa Clara Counties, California

The Palo Alto and southern part of the Redwood Point 7-1/2' quadrangles cover an area on the San Francisco peninsula between San Francisco Bay and the Santa Cruz Mountains. San Francisquito and Los Trancos Creeks, in the southeastern part of the map area, form the boundary between San Mateo and Santa Clara Counties. The area covered by the geologic map extends from tidal and marsh lands at the edge of the bay southward across a gently sloping alluvial plain to the foothills of the northern Santa Cruz Mountains. The foothills are separated from the main mass of the mountains by two northwest-striking faults, the San Andreas and Pilarcitos, that cross the southwest corner of the map area (fig. 1). The map and adjoining areas are here divided into three structural blocks juxtaposed along these faults, adopting the scheme of Nilsen and Brabb (1979): (1) the San Francisco Bay block lying east of the San Andreas Fault Zone; (2) the Pilarcitos block lying between the San Andreas and Pilarcitos Faults; and (3) the La Honda block that includes the main mass of the Santa Cruz Mountains lying west of the Pilarcitos Fault. The west boundary of the La Honda block is the Seal Cove-San Gregorio Fault. Pre-late Pleistocene Cenozoic rocks of the foothills have been compressed into northwest-striking folds, which have been overridden by Mesozoic rocks along southwest-dipping low-angle faults. Coarse- to fine-grained upper Pleistocene and Holocene alluvial and estuarine deposits, eroded from the foothills and composing the alluvial plain, are essentially undeformed. Most of the alluvial plain, including some parts of the marsh land that borders the bay, has been covered by residential and commercial developments, and virtually all of the remaining marsh land has been diked off and used as salt evaporating ponds. The map area includes parts of the municipalities of San Carlos, Redwood City, Atherton, Woodside, Portola Valley, Menlo Park, and East Palo Alto in San Mateo County; and Palo Alto, Stanford University, Los Altos, and Los Altos Hills in Santa Clara County (fig. 2). Much of the university land remains as undeveloped open space surrounded by densely urbanized lands. Geologic maps of all or part of the present map area have been prepared previously by Branner and others (1909), Thomas (1949), Dobbs and Forbes (1960), Dibblee (1966), Page and Tabor (1967), Pampeyan (1970a, 1970b), Beaulieu (1970), Helley and others (1979), and by numerous Stanford University students working on topical earth science problems. In addition, numerous engineering geologic studies have been conducted for site investigations relating to residential and commercial developments and, in particular, for construction of the Stanford Linear Accelerator Center (SLAC). The reports pertaining to SLAC are summarized in Skjei and others (1965) and more recently in a report by Earth Sciences Associates (1983). The interested reader is referred to Brabb and Pampeyan (1983), Brabb and others (1982), Wentworth and others (1985), Wieczorek and others (1985), Thomson and Evernden (1986), Brabb and Olson (1986), Youd and Perkins (1987), Perkins (1987), and Mark and Newman (1988) for information pertaining to geology, history, slope stability, seismic shaking, liquifaction potential, and faulting and seismicity in San Mateo County, some of which can be applied directly to northern Santa Clara County. Field work for the present geologic map was done in 1962-1964 and 1966 when SLAC and Interstate 280 were in early stages of construction. Only minor additions and revisions have been made since this mapping was first released (Pampeyan, 1970a; 1970b) as it was impractical to keep pace with accelerating urban development of the area. Geologic units of the flatlands area are largely adapted from Helley and Lajoie (1979).

California↗
USGS1999

Lithologic, age group, magnetopolarity, and geochemical maps of the Springerville Volcanic Field, east-central Arizona

The Springerville volcanic field is one of the many late Pliocene to Holocene, mostly basaltic, volcanic fields present near the Colorado Plateau margin (fig. 1, in pamphlet). The field overlies the lithospheric transition zone between the Colorado Plateau and the Basin and Range Province (Condit and others, 1989b). Establishing relations in time, space, and composition of the rocks of these plateau-margin fields offers the possibility to integrate more fully into a regional synthesis the detailed geochemistry of these fields now being examined (for example, Perry and others, 1987; Fitton and others, 1988; Menzies and others, 1991). The work also provides baseline information for understanding mantle properties and processes at different depths and locations. Because the Springerville field is the southernmost of the plateau-margin fields, and because it contains both tholeiitic and alkalic rocks (tables 1 and 2, in pamphlet), it is a particularly important location for establishing these patterns in time, space, and composition. Our four thematic maps of the Springerville field were compiled by using digital mapping techniques so that associated petrologic and chemical data could be conveniently included in a geographic information system for one of the plateau-margin fields. Parts of these maps have been included in Condit (1995), a stand-alone Macintosh2 computer program that takes advantage of their digital format.

Arizona↗
USGS1995

Geologic map of Newberry Volcano, Deschutes, Klamath, and Lake counties, Oregon

Newberry volcano, one of the largest Quaternary volcanoes in the conterminous United States, is a broad shieldlike landform with a summit caldera 7 km across. It comprises the products of thousands of eruptions, at least 25 of which occurred during the last 10,000 years (Holocene Epoch). Eruptions have occurred as recently as 1,300 years ago, but isotopic ages indicate that the volcano began its growth as early as 0.6 million years ago. Thus, its long history and recent activity indicate that Newberry volcano is likely to erupt in the future.

Oregon↗
USGS2006

Geologic map of the middle east rift geothermal subzone, Kīlauea Volcano, Hawaiʻi

Kīlauea is an active shield volcano in the southeastern part of the Island of Hawai'i. The middle east rift zone (MERZ) map includes about 27 square kilometers of the MERZ and shows the distribution of the products of 37 separate eruptions during late Holocene time. Lava flows erupted during 1983-96 have reached the mapped area. The subaerial part of the MERZ is 3-4 km wide and about 18 km long. It is a constructional ridge, 50-150 m above the adjoining terrain, marked by low spatter ramparts and cones as high as 60 m. Lava typically flowed either northeast or southeast, depending on vent location relative to the topographic crest of the rift zone. The MERZ receives more than 100 in. of rainfall annually and is covered by tropical rain forest. Vegetation begins to grow on lava a few months after its eruption. Relative heights of trees can be a guide to relative ages of underlying lava flows, but proximity to faults, presence of easily weathered cinders, and human activity also affect the rate of growth. The rocks have been grouped into five basic age groups. The framework for the ages assigned is provided by eight radiocarbon ages from previous mapping by the authors and a single date from the current mapping effort. The numerical ages are supplemented by observations of stratigraphic relations, degree of weathering, soil development, and vegetative cover.

Hawaii↗
USGS1999

Geologic map of the Sedan quadangle, Gallatin and Park Counties, Montana

This quadrangle lies 6.4 km (4 mi) northeast of Bozeman, Mont., in southwestern Montana. Metamorphic, sedimentary, and volcanic rocks of Precambrian to Tertiary age are exposed in the Bridger Range and southwestern margin of the Crazy Mountains Basin in a crustal cross section and a structural triangle zone. Surface geology records Precambrian extension, Late Paleocene east-vergent contraction, including backthrusts, and Holocene basin-range extension.

Montana↗
USGS1986

Geophysical maps of the Dos Cabezas Mountains Wilderness Study Area, Cochise County, Arizona

The Dos Cabezas Mountains Wilderness Study Area, Arizona, lies along part of the crest and northeast flank of the Dos Cabezas Mountains, Cochise County, near the southeast corner of Arizona (fig. 1). The U.S. Bureau of Land Management requested mineral surveys of about 11,921 acres of the approximately 15,000 acre wilderness study area. In this report "wilderness study area" refers to the 11,921 acres that were studied. The Dos Cabezas Mountains are in many ways a typical mountain range of the Basin-and-Range physiographic province. They are a northwest-trending block-faulted range separated from adjacent ranges by broad valleys. The range is about 22 mi long and 8 mi wide, and it reaches an elevation of 8,354 ft at Dos Cabezas Peaks, located about 2 mi west of the study area. The terrain of the area is rugged. Roadheads and trails provide adequate access for foot traverses. In the Dos Cabezas Mountains the Apache Pass fault zone is the major structural feature, barely skirting the southwest side of the study area. It extends several miles to the northwest and tens of miles to the southeast, across the Chiricahua Mountains beyond Apache Pass. It is typically made up of a pair of bounding faults and some anastomosing faults between them. The study area is underlain by a variety of sedimentary, igneous, and metamorphic rocks that provide only a fragmentary record of geologic events between Precambrian and Holocene times. A suite of metamorphic and igneous (primarily crystalline) rocks forms the basement terrain. Paleozoic and Mesozoic sedimentary rocks and also Paleozoic and Mesozoic volcanic rocks overlie the basement rocks but are extensively eroded away and may be covered. A pile of volcanic rocks of Late Cretaceous and Paleocene age caps the older rocks in much of the study area. Mid-Tertiary intrusive rocks underlie the eastern part of the study area as well as some very small, widely scattered additional localities. Quaternary gravel deposits occur in the major valleys and along the mountain front.

Arizona↗
USGS1987

Maps and seismic profiles showing geology of the inner continental shelf, Cape Ann, Massachusetts to New Hampshire

This interpretation of the geology of the Inner Continental Shelf from Cape Ann, Mass. to New Hampshire (fig. 1) is based on high-resolution seismic-reflection surveys conducted in 1979 and 1980 as part of a cooperative program between the Massachusetts Department of Public Works and the U.S. Geological Survey. Seismic data were collected aboard the RV Gilliss along 104 kilometers (km) of widely spaced trackline (fig. 2). These tracks trend subparallel to the coast. About 290 km cf trackline, spaced approximately 2 km apart and oriented roughly normal to the coast, were taken aboard the RV Asterias (fig. 2). Early studies in the western Gulf of Maine have outlined the general geology and geologic history of the region. Seismic-reflection data have defined the major stratigraphic units and unconformities (Oldale and Uchupi, 1970; Ballard and Uchupi, 1972; Oldale and others, 1973). Two long cores provided information on the glacial and postglacial sediments in the deep offshore basins (Tucholke and Hollister, 1973). Generalized bottom-sediment type and distribution were determined by Schlee and others (1973) and by Folger and others (1975). Investigations on land, which have provided information on the late Quaternary history of the offshore area, include descriptions of ice retreat and marine submergence (Bloom, 1963; Smith, 1982; Stone and Peper, 1982; Thompson, 1982). Radiocarbon dates from coastal marsh peats have established the middle to late Holocene sea-level-rise history (McIntire and Morgan, 1964; Keene, 1971). Submarine moraincs that recently were recognized off Cape Ann provide additional information on the nature and chronology of ice retreat (Oldale, 1985a). A submerged delta of the Merrimack River and a submerged barrier spit have been used to establish an early IIolocene lowstand of 588 level of about 50 meters (m) below present sea level (Oldale and others, 1983; Oldale, 1985b).

Massachusetts, New Hampshire↗
USGS1993

Logs of exploratory trenches through liquefaction features on late Quaternary terraces in the Obion River Valley, northwestern Tennessee

From December 1811 to February 1812, four large earthquakes (m b ≥7.0) occurred in the New Madrid (Missouri) Seismic Zone (NMSZ). These have been the largest historical earthquakes in eastern North America. Although this area has been the focus of considerable seismological research, estimates of the repeat time of large-magnitude seismic events remain poorly constrained. Past estimates were primarily based on earthquake-frequency statistics and on paleoseismology studies. Johnston and Nava (1985) compiled historical seismicity data covering about 180 years and instrumental data covering 10 years, and they concluded that the repeat time for large-magnitude events (m b ≥7.0) is between 500 and 1,100 yrs. However, this estimate is based on assumptions that the data set is representative of the seismicity of the region over the past 1,000 yrs, and that the relation between earthquake frequency and magnitude is constant (Johnston and Nava, 1985). Because these assumptions cannot be verified, this estimated recurrence interval of 550-1,100 hrs must be considered tentative (S. G. Wesnousky and L. M. Leffler, written commun., 1991). Investigation of exploratory trenches across the Reelfoot scarp in northwestern Tennessee documented the only unequivocal Holocene surface faulting in the upper Mississippi embayment (Russ and others, 1978; Russ, 1979). Fluvial sediment younger than about 2,250 yrs old is faulted, and the net vertical displacement is more than 3 m. Stratigraphic relations indicate at least two episodes of faulting occurred between about 2,250 yr B.P. and the 1811-12 events to estimate an average recurrence interval of less than 600 yrs for large-magnitude earthquakes in the NMSZ. However, inasmuch as Russ (1970) found no evidence for any historical offset on the Reelfoot scarp, the relation between the Reelfoot scarp and large paleoeartchquakes in the NMSZ has not been clearly established. The development of widespread liquefaction features suring the 1811-12 earthquake series (Obermeier, 1989, Obermeier and others, 1990) and the probably development of similar features during previous large-magnitude seismic events (m b ≥6.2, Nuttli, 1982) have been the basis for several attempts to document the history of paleoliquefaction. Haller and Crone (1986) found evidence of only one episode of sand-blow development in exploratory trenches in late Pleistocene alluvium in eastern Arkansas and concluded that this liquefaction event was probably associated with the 1811-12 earthquake series. Saucier (1989) reported evidence of three liquefaction events in the past approximately 1,000 yrs in an exploratory trench in eastern Arkansas. On the basis of the apparent absence of post-depositional erosion separating the three sand-blow deposits, Saucier (1989) concluded that they formed in a relatively short period of time, probably during the 1811-12 earthquake series. Similarly, Schweig and Marple (1991) found evidence of only recent (probably 1811-12) liquefaction in exploratory trenched on late Wisconsin braided-stream deposits in southeastern Missouri. Leffler and Wesnousky (1991) and Wesnousky and Leffler (written commun., 1991) examined tens of kilometers of recently excavated drainage ditches in late Wisconsin braided-stream deposits in eastern Arkansas and found no evidence for prehistorical liquefaction events during the last 10,000 yrs. In contrast, Saucier (1991) estimated an average recurrence interval about 470 yrs on the basis of historical ages of liquefaction in the NMSZ. The lack of similar evidence from other sites implies a prehistorical liquefaction-producing seismic event in southeastern Missouri that was considerably smaller than the 1811-12 earthquake series. The apparent absence of paleoliquefaction features in late Wisconsin fluvial deposits in the zone of most intense 1811-12 liquefaction indicates that the repeat time of large (m b ≥7.0) seismic events in the NMSZ is at least 10,000 yrs (Saucier, 1991; Wesnousky and Leffler, written commun., 1991). The present study was undertaken to verify this conclusion by documenting the record of liquefaction in late Wisconsin fluvial deposits along the Obion River, in northwestern Tennessee, This region was identified by Obermeier (1989) as an area deserving further study because of its proximity to the NMSZ and to areas of historical liquefaction.

Tennessee↗
USGS1994

Principal reference section for part of the Eocene Ghazij Formation, Gishtari Nala area, Mach coal field, Balochistan, Pakistan

The information presented on this sheet was collected as part of a joint U.S. Geological Survey-Geological Survey of Pakistan program sponsored by the U.S. Agency for International Development. As a project within this program, the coal-bearing Ghazij Formation (Eocene) was investigated in the northeastern part of Balochistan east and south of the provincial capital of Quetta. Strata exposed in this area range in age from Permian to Holocene and crop out as a belt of folded and thrusted rocks that form a southeast-facing orocline. In this region of Pakistan, the Ghazij can usually be divided into three parts. The lower part is the thickest (probably more than 1,000 m) and consists of gray-weathering calcareous mudrock (shale, mudstone, and impure claystone) and a few tabular bodies of fine-to medium-grained calcareous sandstone. The middle part (27-300 m) consists of gray-weathering calcareous mudrock and tabular to lenticular bodies of fine- to medium-grained calcareous sandstone; beds of carbonaceous shale and coal are common (in the Mach area, the middle part of the formation also contains numerous individual beds of muddy limestone). The upper part (as thick as 533 m) contains reddish-weathering calcareous mudrock that contains scattered lenticular bodies of fine-to medium-grained calcareous sandstone. Fossil plant debris is common in mudrock of the lower and middle parts of the Ghazij and bivalves and gastropods are common in the middle part of the formation; the upper part of the Ghazij is usually unfossiliferous. Underlying the Ghazij are the carbonate rocks of the Paleocene Dungan Formation (or its equivalent), and overlying the Ghazij are the mostly carbonate rocks of the Eocene Kirthar Formation (or its equivalent). Both contacts can be conformable or unconformable. All of the pre-Neogene rocks in Balochistan are greatly deformed by the collision of India and Asia. The Ghazij is especially susceptible to regional compressional tectonics because it contains large amounts of shale and is sandwiched between two thick carbonate units. As a result, bedding-plane faults and isoclinal folds are very common. As part of our study of the Ghazij Formation, five stratigraphic sections were measured: one near Pir Ismail Ziarat, one in the Sor Range, two in the vicinity of Mach, and one near Johan. Each area's section is published separately.

Balochistan↗
USGS1994

Principal reference section for part of the Eocene Ghazij Formation, Moghal Mine area, Mach coal field, Balochistan, Pakistan

The information presented on this sheet was collected as part of a joint U.S. Geological Survey-Geological Survey of Pakistan program sponsored by the U.S. Agency for International Development. As a project within this program, the coal-bearing Ghazij Formation (Eocene) was investigated in the northeastern part of Balochistan cast and south of the provincial capital of Quetta. Strata exposed in this area range in age from Permian to Holocene and crop out as a belt of folded and thrusted rocks that form a southeast-facing orocline. In this region of Pakistan, the Ghazij can usually be divided into three parts. The lower part is the thickest (probably more than 1,000 m) and consists of gray-weathering calcareous mudrock (shale, mudstone, and impure claystone) and a few tabular bodies of fine-to medium-grained calcareous sandstone. The middle part (27-300 m) consists of gray-weathering calcareous mudrock and tabular to lenticular bodies of fine-to medium-grained calcareous sandstone; beds of carbonaceous shale and coal are common. The upper part (as thick as 533 m) contains reddish-weathering calcareous mudrock that contains scattered lenticular bodies of fine- to medium-grained calcareous sandstone. Fossil plant debris is common in mudrock of the lower and middle parts of the Ghazij, and bivalves and gastropods are common in the middle part; the upper part of the Ghazij is usually unfossiliferous. This three-fold division of the Ghazij is less distinct in the Johan area. Here, the upper part of the formation is clearly identifiable, but rocks below it are poorly exposed and assigning a stratigraphic level that separates the middle and lower parts of the formation is problematic. Below the upper part of the formation is a thick sequence of greenish-gray calcareous mudrock that contains locally abundant plant debris and isolated bodies of brown-weathering sandstone. Rare carbonaceous shale and even rarer coal are present in the upper part of this sequence, and this interval of the formation might correspond to the middle part of the Ghazji exposed in areas to the north. We propose that, in the Johan area, those rocks below the upper part of the formation be referred to as the main body of the Ghazij (for example, main-body Ghazij). Underlying the Ghazij are the carbonate rocks of the Paleocene Dungan Formation (or its equivalent), and overlying the Ghazij are the mostly carbonate rocks of the Eocene Kirthar Formation (or its equivalent). Both contacts can be conformable or unconformable. All of the pre-Neogene rocks in Balochistan are greatly deformed by the collision of India and Asia. The Ghazij is especially susceptible to regional compressional tectonics because it contains a large amount of shale and is sandwiched between two thick carbonate units. As a result, bedding-plane faults and isoclinal folds are common. As part of our study of the Ghazij Formation, five stratigraphic sections were measured: one near Pir Ismail Ziarat, one in the Sor Range, two in the vicinity of Mach, and one near Johan. Each area's section is published separately.

Balochistan↗
USGS1994

Principal reference section for part of the Eocene Ghazij Formation, Sarawan River area, Johan coal field, Balochistan, Pakistan

The information presented on this sheet was collected as part of a joint U.S. Geological Survey-Geological Survey of Pakistan program sponsored by the U.S. Agency for International Development. As a project within this program, the coal-bearing Ghazij Formation (Eocene) was investigated in the northeastern part of Balochistan cast and south of the provincial capital of Quetta. Strata exposed in this area range in age from Permian to Holocene and crop out as a belt of folded and thrusted rocks that form a southeast-facing orocline. In this region of Pakistan, the Ghazij can usually be divided into three parts. The lower part is the thickest (probably more than 1,000 m) and consists of gray-weathering calcareous mudrock (shale, mudstone, and impure claystone) and a few tabular bodies of fine-to medium-grained calcareous sandstone. The middle part (27-300 m) consists of gray-weathering calcareous mudrock and tabular to lenticular bodies of fine-to medium-grained calcareous sandstone; beds of carbonaceous shale and coal are common. The upper part (as thick as 533 m) contains reddish-weathering calcareous mudrock that contains scattered lenticular bodies of fine- to medium-grained calcareous sandstone. Fossil plant debris is common in mudrock of the lower and middle parts of the Ghazij, and bivalves and gastropods are common in the middle part; the upper part of the Ghazij is usually unfossiliferous. This three-fold division of the Ghazij is less distinct in the Johan area. Here, the upper part of the formation is clearly identifiable, but rocks below it are poorly exposed and assigning a stratigraphic level that separates the middle and lower parts of the formation is problematic. Below the upper part of the formation is a thick sequence of greenish-gray calcareous mudrock that contains locally abundant plant debris and isolated bodies of brown-weathering sandstone. Rare carbonaceous shale and even rarer coal are present in the upper part of this sequence, and this interval of the formation might correspond to the middle part of the Ghazji exposed in areas to the north. We propose that, in the Johan area, those rocks below the upper part of the formation be referred to as the main body of the Ghazij (for example, main-body Ghazij). Underlying the Ghazij are the carbonate rocks of the Paleocene Dungan Formation (or its equivalent), and overlying the Ghazij are the mostly carbonate rocks of the Eocene Kirthar Formation (or its equivalent). Both contacts can be conformable or unconformable. All of the pre-Neogene rocks in Balochistan are greatly deformed by the collision of India and Asia. The Ghazij is especially susceptible to regional compressional tectonics because it contains a large amount of shale and is sandwiched between two thick carbonate units. As a result, bedding-plane faults and isoclinal folds are common. As part of our study of the Ghazij Formation, five stratigraphic sections were measured: one near Pir Ismail Ziarat, one in the Sor Range, two in the vicinity of Mach, and one near Johan. Each area's section is published separately.

Balochistan↗
USGS2000

Map of Distribution of Bottom Sediments on the Continental Shelf, Gulf of Alaska

Introduction The U.S. Geological Survey has a long history of exploring marine geology in the Gulf of Alaska. As part of a cooperative program with other federal and state agencies, the USGS is investigating the relations between ocean-floor geology and benthic marine biohabitats. This bottom sediment map, compiled from published literature will help marine biologists develop an understanding of sea-floor geology in relation to various biological habitats. The pattern of sea-floor sedimentation and bottom morphology in the Gulf of Alaska reflects a complex interplay of regional tectonism, glacial advances and retreats, oceanic and tidal currents, waves, storms, eustatic change, and gravity-driven processes. This map, based on numerous cruises during the period of 1970-1996, shows distribution of bottom sediments in areas of study on the continental shelf. The samples were collected with piston, box, and gravity corers, and grab samplers. The interpretations of sediment distribution are the products of sediment size analyses combined with interpretations of high-resolution seismic reflection profiles. The sea floor was separated into several areas as follows: Cook Inlet -- Hazards studies in this embayment emphasized sediment distribution, sediment dynamics, bedforms, shallow faults, and seafloor stability. Migrating mega-sandwaves, driven by strong tidal currents, influence seabed habitats and stability of the seafloor, especially near pipelines and drilling platforms. The coarseness of the bottom sediment reinforces the influence of the strong tidal currents on the seafloor habitats. Kodiak Shelf -- Tectonic framework studies demonstrate the development of an accretionary wedge as the Pacific Plate underthrusts the Alaskan landmass. Seismic data across the accretionary wedge reveal anomalies indicative of fluid/gas vent sites in this segment of the continental margin. Geologic hazards research shows that movement along numerous shallow faults poses a risk to sea floor structures. Sea-floor sediment on shallow banks is eroded by seasonal wave-generated currents. The winnowing action of the large storm waves results in concentrations of gravel over broad segments of the Kodiak shelf. Northeastern Gulf of Alaska -- Tectonic framework studies demonstrate that rocks of distant origin (Yakutat terrane) are currently attached to and moving with the Pacific Plate, as it collides with and is subducted beneath southern Alaska. This collision process has led to pronounced structural deformation of the continental margin and adjacent southern Alaska. Consequences include rapidly rising mountains and high fluvial and glacial sedimentation rates on the adjacent margin and ocean floor. The northeastern Gulf of Alaska shelf also has concentrations of winnowed (lag) gravel on Tarr Bank and on the outer shelf southeast of Yakutat Bay. Between Kayak Island and Yakutat Bay the outer shelf consists of pebbly mud (diamict). This diamict is a product of glacial marine sedimentation during the Pleistocene and is present today as a relict sediment. A prograding wedge of Holocene sediment consisting of nearshore sand grading seaward into clayey silt and silty clay covers the relict pebbly mud to mid-shelf and beyond. Shelf and slope channel systems transport glacially derived sediment across the continental margin into Surveyor Channel, an abyssal fan and channel system that reaches over 1,000 km to the Aleutian Trench.

Miscellaneous Field Studies Map↗
USGS2003

Geologic map of the Mound Spring quadrangle, Nye and Clark Counties, Nevada, and Inyo County, California

The Mound Spring quadrangle, the southwestern-most 7.5' quadrangle of the area of the Las Vegas 1:100,000-scale quadrangle, is entirely within the Pahrump Valley, spanning the Nevada/California State line. New geologic mapping of the predominantly Quaternary materials is combined with new studies of gravity and geochronology in this quadrangle. Eleven predominantly fine-grained units are delineated, including playa sediment, dune sand, and deposits associated with several cycles of past groundwater discharge and distal fan sedimentation. These units are intercalated with 5 predominantly coarse-grained alluvial-fan and wash gravel units mainly derived from the Spring Mountains. The gravel units are distinguished on the basis of soil development and associated surficial characteristics. Thermoluminescence and U-series geochronology constrain most of the units to the Holocene and late and middle Pleistocene. Deposits of late Pleistocene groundwater discharge in the northeast part of the quadrangle are associated with a down-to-the-southwest fault zone that is expressed by surface fault scarps and a steep gravity gradient. The gravity field also defines a northwest-trending uplift along the State line, in which the oldest sediments are poorly exposed. About 2 km to the northeast a prominent southwest-facing erosional escarpment is formed by resistant beds in middle Pleistocene fine-grained sediments that dip northeast away from the uplift. These sediments include cycles of groundwater discharge that were probably caused by upwelling of southwesterly groundwater flow that encountered the horst.

Miscellaneous Field Studies Map↗
USGS2001

Geologic map and map database of the Spreckels 7.5-minute Quadrangle, Monterey County, California

Introduction The Spreckels quadrangle lies at the north end of the Sierra de Salinas and extends from the Salinas Valley on the northeast across Los Laurelles Ridge south to Carmel Valley, an intermontane valley that separates the Santa Lucia Range from the Sierra de Salinas (fig. 1). The Toro Regional Park occupies the east-central part of the quadrangle, whereas the former Fort Ord Military Reservation covers the northwestern part of the area and is the probable locus of future development. Subdivisions largely occupy the older floodplain of Toro Creek and the adjacent foothills, with less dense development along the narrower canyons of Corral de Tierra and San Benancio Gulch to the south. The foothills southwest of the Salinas River are the site of active residential development. Geologically, the study area has a crystalline basement of Upper Cretaceous granitic rocks of the Salinian block and older metasedimentary rocks of the schist of the Sierra de Salinas of probable Cretaceous age. Resting nonconformably upon these basement rocks is a sedimentary section that ranges in age from middle Miocene to Holocene and has a composite thickness of as much as 1,200 m. One of the purposes of the present study was to investigate the apparent lateral variation of the middle to upper Miocene sections from the typical porcelaneous and diatomaceous Monterey Formation of the Monterey and Seaside quadrangles to the west (Clark and others, 1997) to a thick marine sandstone section in the eastern part of the Spreckels quadrangle. Liquefaction, which seriously affected the Spreckels area in the 1906 San Francisco earthquake (Lawson, 1908), and landsliding are the two major geological hazards of the area. The landslides consist mainly of older large slides in the southern and younger debris flows in the northern part of the quadrangle. This digital map database, compiled from previously published and unpublished data, and new mapping by the authors, represents the general distribution of bedrock and surficial deposits in the mapped area. Together with the accompanying text file (skmf.txt, skmf.pdf, or skmf.ps), it provides current information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:24,000 or smaller.

Miscellaneous Field Studies Map↗
USGS2002

Geologic map of the Storm King Mountain quadrangle, Garfield County, Colorado

New 1:24,000-scale geologic mapping in the Storm King Mountain 7.5' quadrangle, in support of the USGS Western Colorado I-70 Corridor Cooperative Geologic Mapping Project, provides new data on the structure on the south margin of the White River uplift and the Grand Hogback and on the nature, history, and distribution of surficial geologic units. Rocks ranging from Holocene to Proterozoic in age are shown on the map. The Canyon Creek Conglomerate, a unit presently known to only occur in this quadrangle, is interpreted to have been deposited in a very steep sided local basin formed by dissolution of Pennsylvanian evaporite late in Tertiary time. At the top of the Late Cretaceous Williams Fork Formation is a unit of sandstone, siltstone, and claystone from which Late Cretaceous palynomorphs were obtained in one locality. This interval has been mapped previously as Ohio Creek Conglomerate, but it does not fit the current interpretation of the origin of the Ohio Creek. Rocks previously mapped as Frontier Sandstone and Mowry Shale are here mapped as the lower member of the Mancos Shale and contain beds equivalent to the Juana Lopez Member of the Mancos Shale in northwestern New Mexico. The Pennsylvanian Eagle Valley Formation in this quadrangle grades into Eagle Valley Evaporite as mapped by Kirkham and others (1997) in the Glenwood Springs area. The Storm King Mountain quadrangle spans the south margin of the White River uplift and crosses the Grand Hogback monocline into the Piceance basin. Nearly flat lying Mississippian through Cambrian sedimentary rocks capping the White River uplift are bent into gentle south dips and broken by faults at the edge of the uplift. South of these faults the beds dip moderately to steeply to the south and are locally overturned. These dips are interrupted by a structural terrace on which are superposed numerous gentle minor folds and faults. This terrace has an east-west extent similar to that of the Canyon Creek Conglomerate to the north. We interpret that the terrace formed by movement of Eagle Evaporite from below in response to dissolution and diapirism in the area underlain by the conglomerate. A low-angle normal fault dipping gently north near the north margin of the quadrangle may have formed also in response to diapirism and dissolution in the area of the Canyon Creek Conglomerate. Along the east edge of the quadrangle Miocene basalt flows are offset by faults along bedding planes in underlying south-dipping Cretaceous rocks, probably because of diapiric movement of evaporite into the Cattle Creek anticline (Kirkham and Widmann, 1997). Steep topography and weak rocks combine to produce a variety of geologic hazards in the quadrangle.

Miscellaneous Field Studies Map↗
USGS2003

Ferricrete, manganocrete, and bog iron occurrences with selected sedge bogs and active iron bogs and springs in the upper Animas River watershed, San Juan County, Colorado

During 1996 to 2000, the Bureau of Land Management, National Park Service, Environmental Protection Agency, United States Department of Agriculture (USDA) Forest Service, and the U.S. Geological Survey (USGS) developed a coordinated strategy to (1) study the environmental effects of historical mining on Federal lands, and (2) remediate contaminated sites that have the greatest impact on water quality and ecosystem health. This dataset provides information that contributes to these overall objectives and is part of the USGS Abandoned Mine Lands Initiative. Data presented here represent ferricrete occurrences and selected iron bogs and springs in the upper Animas River watershed in San Juan County near Silverton, Colorado. Ferricretes (stratified iron and manganese oxyhydroxide-cemented sedimentary deposits) are one indicator of the geochemical baseline conditions as well as the effect that weathering of mineralized rocks had on water quality in the Animas River watershed prior to mining. Logs and wood fragments preserved in several ferricretes in the upper Animas River watershed, collected primarily along streams, yield radiocarbon ages of modern to 9,580 years B.P. (P.L. Verplanck, D.B. Yager, and S.E. Church, work in progress). The presence of ferricrete deposits along the current stream courses indicates that climate and physiography of the Animas River watershed have been relatively constant throughout the Holocene and that weathering processes have been ongoing for thousands of years prior to historical mining activities. Thus, by knowing where ferricrete is preserved in the watershed today, land-management agencies have an indication of (1) where metal precipitation from weathering of altered rocks has occurred in the past, and (2) where this process is ongoing and may confound remediation efforts. These data are included as two coverages-a ferricrete coverage and a bogs and springs coverage. The coverages are included in ArcInfo shapefile and ArcInfo interchange file format.

Colorado↗