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At least 343 records · Page 19Linked to original sources

USGS2001

Use of Landsat MSS and TM imagery to improve reconnaissance geologic mapping in the Ruby quadrangle, west-central Alaska: A section in Geological studies in Alaska by the U.S. Geological Survey, 1999

By using Multispectral Scanner (MSS) and Thematic Mapper (TM) satellite images, the spatial relation of units JMtu (mafic, ultramafic, and sedimentary rocks, undivided) and PzZrqs (pelitic and quartzitic schist) of Wilson and others (1998) from the northeastern portion of the Ruby 1:250,000-scale quadrangle geologic map was further defined. The MSS image was first analyzed using spectral signatures to separate and highlight pixels associated only with the units of interest. This approach was ineffective at separating the units from areas of the image with similar spectral signatures, but it did show that unit JMtu and associated areas consistently had a high brightness value, while unit PzZrqs and associated areas consistently had a low brightness value. Consequently, a new approach was developed using spectral enhancement to emphasize the differences between these high- and low- brightness areas. Once the TM image was obtained, the spectral signature separation and spectral enhancement approaches were again tested, but the results were similar to those found using the MSS image. By using the results from the spectral enhancement of the MSS image in combination with current ground-truth data, the locations of units JMtu and PzZrqs in the Ruby quadrangle were reinterpreted.

Alaska↗

USGS2019

Geologic map of the Ferncliff and Louisa quadrangles, Louisa, Fluvanna, and Goochland Counties, Virginia

The area encompassed by the geologic map of the Ferncliff and Louisa, Va., 7.5-minute quadrangles includes the hypothetical surface projection of the Quail fault, which is the subsurface fault that was responsible for the 2011 magnitude 5.8 (M5.8) Mineral, Va., earthquake. The mapping shows that the Quail fault appears to have reactivated the Harris Creek fault, a Paleozoic fault that has been mapped and named in the study area and marks the boundary between the Ellisville pluton neck and Chopawamsic Formation. The Harris Creek fault was also reactivated in the early Mesozoic. Another result of the mapping is a well-defined, southwest to northeast, narrow zone of metagraywacke and ultramafic rocks (both part of the informal Shores complex) that marks the closure of a small ocean basin and the accretion of the 468- to 460-Ma (mega-annum) Ordovician Chopawamsic volcanic arc (part of the Carolina terrane) onto Laurentia. The accretion zone is truncated by the Ordovician-Silurian (444 Ma) Ellisville pluton; the 444-Ma age of the pluton therefore represents the minimum age of the accretion zone and indicates likely closure of the ocean basin during the Taconic orogeny. Across the map area, the metamorphic grade ranges from lower-greenschist facies in the northwest to amphibolite facies in the southeast. 40 Ar/ 39 Ar age-dating across this metamorphic gradient indicates that Taconic metamorphism was overprinted by late-Paleozoic Alleghanian metamorphism that was accompanied by refolding and faulting of Taconic structures. Quaternary terraces mapped along the South Anna River record a long history of incision and downcutting. A continuing question is how much of this downcutting was a result of neotectonic uplift in the central Virginia seismic zone. This report consists of a single geologic map sheet and an online geographic information systems database that includes bedrock geologic unit contacts and polygons, surficial geologic polygons, faults, and structural geologic information.

Virginia↗

USGS2016

Preliminary geologic mapping of Cretaceous and Tertiary formations in the eastern part of the Little Snake River coal field, Carbon County, Wyoming

In the 1970s and 1980s, C.S. Venable Barclay conducted geologic mapping of areas primarily underlain by Cretaceous coals in the eastern part of the Little Snake River coal field (LSR) in Carbon County, southwest Wyoming. With some exceptions, most of the mapping data were never published. Subsequently, after his retirement from the U.S. Geological Survey (USGS), his field maps and field notebooks were archived in the USGS Field Records. Due to a pending USGS coal assessment of the Little Snake River coal field area and planned geological mapping to be conducted by the Wyoming State Geological Survey, Barclay’s mapping data needed to be published to support these efforts. Subsequently, geologic maps were scanned and georeferenced into a geographic information system, and project and field notes were scanned into Portable Document Format (PDF) files. Data for seventeen 7½-minute quadrangles are presented in this report. This publication is solely intended to compile the mapping data as it was last worked on by Barclay and provides no interpretation or modification of his work.

Wyoming↗

USGS2014

Lidar-revised geologic map of the Poverty Bay 7.5' quadrangle, King and Pierce Counties, Washington

For this map, we interpreted a 6-ft-resolution lidar digital elevation model combined with the geology depicted on the Geologic Map of the Poverty Bay 7.5' Quadrangle, King and Pierce Counties, Washington (Booth and others, 2004b). The authors of the 2004 map described, interpreted, and located the geology on the 1:24,000-scale topographic map of the Poverty Bay 7.5' quadrangle. The topographic map, published in 1997 but compiled in 1957, includes planimetry derived from 1990 imagery and 20-ft contours, nominal horizontal resolution of 40 ft (12 m), and nominal vertical accuracy of 10 ft (3 m). Similar to many surficial geologic maps, much of the geology in Booth and others (2004b) was interpreted from landforms portrayed on the topographic map. In 2003, the Puget Sound Lidar Consortium obtained a lidar-derived digital elevation model (DEM) for the Puget Sound region including all of the Poverty Bay 7.5' quadrangle. For a brief description of lidar (LIght Detection And Ranging) and this data acquisition program, see Haugerud and others (2003). This new DEM has a horizontal resolution and accuracy of 6 ft (2 m) and vertical accuracy of approximately 1 ft (0.3 m). The greater resolution and accuracy of the lidar DEM have facilitated a new interpretation of the geology, especially the distribution and relative age of some surficial deposits.

Washington↗

USGS2015

Geologic maps of the eastern Alaska Range, Alaska (1:63,360 scale)

This report provides a description of map units for a suite of 44 inch-to-mile (1:63,360-scale) geologic quadrangle maps of the eastern Alaska Range. This report also contains a geologic and tectonic summary and a comprehensive list of references pertaining to geologic mapping and specialized studies of the region. In addition to the geologic maps of the eastern Alaska Range, this package includes a list of map units and an explanation of map symbols and abbreviations. The geologic maps display detailed surficial and bedrock geology, structural and stratigraphic data, portrayal of the active Denali fault that bisects the core of the east–west-trending range, and portrayal of other young faults along the north and south flanks of the range.

Alaska↗

USGS2006

Geologic map of the Western Grove quadrangle, northwestern Arkansas

This map summarizes the geology of the Western Grove 7.5-minute quadrangle in northern Arkansas that is located on the southern flank of the Ozark dome, a late Paleozoic regional uplift. The exposed bedrock of this map area comprises approximately 1,000 ft of Ordovician and Mississippian carbonate and clastic sedimentary rocks that have been mildly folded and broken by faults. A segment of the Buffalo River loops through the southern part of the quadrangle, and the river and adjacent lands form part of Buffalo National River, a park administered by the U.S. National Park Service. This geologic map provides information to better understand the natural resources of the Buffalo River watershed, particularly its karst hydrogeologic framework.

Scientific Investigations Map↗

USGS2007

Geologic map of the State of Hawai`i

The State's geology is presented on eight full-color map sheets, one for each of the major islands. These map sheets, the illustrative meat of the publication, can be downloaded in pdf format, ready to print. Map scale is 1:100,000 for most of the islands, so that each map is about 27 inches by 36 inches. The Island of Hawai`i, largest of the islands, is depicted at a smaller scale, 1:250,000, so that it, too, can be shown on 36-inch-wide paper. The new publication isn't limited strictly to its map depictions. Twenty years have passed since David Clague and Brent Dalrymple published a comprehensive report that summarized the geology of all the islands, and it has been even longer since the last edition of Gordon Macdonald's book, Islands in the Sea, was revised. Therefore the new statewide geologic map includes an 83-page explanatory pamphlet that revisits many of the concepts that have evolved in our geologic understanding of the eight main islands. The pamphlet includes simplified page-size geologic maps for each island, summaries of all the radiometric ages that have been gathered since about 1960, generalized depictions of geochemical analyses for each volcano's eruptive stages, and discussion of some outstanding topics that remain controversial or deserving of additional research. The pamphlet also contains a complete description of map units, which enumerates the characteristics for each of the state's many stratigraphic formations shown on the map sheets. Since the late 1980s, the audience for geologic maps has grown as desktop computers and map-based software have become increasingly powerful. Those who prefer the convenience and access offered by Geographic Information Systems (GIS) can also feast on this publication. An electronic database, suitable for most GIS software applications, is available for downloading. The GIS database is in an Earth projection widely employed throughout the State of Hawai`i, using the North American datum of 1983 and the Universal Transverse Mercator system projection to zone 4. 'This digital statewide map allows engineers, consultants, and scientists from many different fields to take advantage of the geologic database,' said John Sinton, a geology professor at the University of Hawai`i, whose new mapping of the Wai`anae Range (West O`ahu) appears on the map. Indeed, when a testing version was first made available, most requests came from biologists, archaeologists, and soil scientists interested in applying the map's GIS database to their ongoing investigations. Another area newly depicted on the map, in addition to the Wai`anae Range, is Haleakala volcano, East Maui. So too for the active lava flows of Kilauea volcano, Island of Hawai`i, where the landscape has continued to evolve in the ten years since publication of the Big Island's revised geologic map. For the other islands, much of the map is compiled from mapping published in the 1930-1960s. This reliance stems partly from shortage of funding to undertake entirely new mapping but is warranted by the exemplary mapping of those early experts. The boundaries of all map units are digitized to show correctly on modern topographic maps.

Hawaii↗

USGS1998

Bedrock geologic map of the Yucca Mountain area, Nye County, Nevada

Yucca Mountain, Nye County, Nevada, has been identified as a potential site for underground storage of high-level radioactive nuclear waste. Detailed bedrock geologic maps form an integral part of the site characterization program by providing the fundamental framework for research into the geologic hazards and hydrologic behavior of the mountain. This bedrock geologic map provides the geologic framework and structural setting for the area in and adjacent to the site of the potential repository. The study area comprises the northern and central parts of Yucca Mountain, located on the southern flank of the Timber Mountain-Oasis Valley caldera complex, which was the source for many of the volcanic units in the area. The Timber Mountain-Oasis Valley caldera complex is part of the Miocene southwestern Nevada volcanic field, which is within the Walker Lane belt. This tectonic belt is a northwest-striking megastructure lying between the more active Inyo-Mono and Basin-and-Range subsections of the southwestern Great Basin. Excluding Quaternary surficial deposits, the map area is underlain by Miocene volcanic rocks, principally ash-flow tuffs with lesser amounts of lava flows. These volcanic units include the Crater Flat Group, the Calico Hills Formation, the Paintbrush Group, and the Timber Mountain Group, as well as minor basaltic dikes. The tuffs and lava flows are predominantly rhyolite with lesser amounts of latite and range in age from 13.4 to 11.6 Ma. The 10-Ma basaltic dikes intruded along a few fault traces in the north-central part of the study area. Fault types in the area can be classified as block bounding, relay structures, strike slip, and intrablock. The block-bounding faults separate the 1- to 4-km-wide, east-dipping structural blocks and exhibit hundreds of meters of displacement. The relay structures are northwest-striking normal fault zones that kinematically link the block-bounding faults. The strike-slip faults are steep, northwest-striking dextral faults located in the northern part of Yucca Mountain. The intrablock faults are modest faults of limited offset (tens of meters) and trace length (less than 7 km) that accommodated intrablock deformation. The concept of structural domains provides a useful tool in delineating and describing variations in structural style. Domains are defined across the study area on the basis of the relative amount of internal faulting, style of deformation, and stratal dips. In general, there is a systematic north to south increase in extensional deformation as recorded in the amount of offset along the block-bounding faults as well as an increase in the intrablock faulting. The rocks in the map area had a protracted history of Tertiary extension. Rocks of the Paintbrush Group cover much of the area and obscure evidence for older tectonism. An earlier history of Tertiary extension can be inferred, however, because the Timber Mountain-Oasis Valley caldera complex lies within and cuts an older north-trending rift (the Kawich-Greenwater rift}. Evidence for deformation during eruption of the Paintbrush Group is locally present as growth structures. Post-Paintbrush Group, pre-Timber Mountain Group extension occurred along the block-bounding faults. The basal contact of the 11.6-Ma Rainier Mesa Tuff of the Timber Mountain Group provides a key time horizon throughout the area. Other workers have shown that west of the study area in northern Crater Flat the basal angular unconformity is as much as 20° between the Rainier Mesa and underlying Paintbrush Group rocks. In the westernmost part of the study area the unconformity is smaller (less than 10°), whereas in the central and eastern parts of the map area the contact is essentially conformable. In the central part of the map the Rainier Mesa Tuff laps over fault splays within the Solitario Canyon fault zone. However, displacement did occur on the block-bounding faults after deposition of the Rainier Mesa Tuff inasmuch as it is locally caught up in the hanging-wall deformation of the block-bounding faults. Therefore, the regional Tertiary to Recent extension was protracted, occurring prior to and after the eruption of the tuffs exposed at Yucca Mountain.

Nevada↗

USGS2008

Geologic map of Mount St. Helens, Washington prior to the 1980 eruption

It is rare that a geologic map exists for a volcano prior to such a catastrophic modification as that produced by the eruption of Mount St. Helens in 1980. As such, this map provides an important historical record of the volcano prior to that eruption. The map has not been reviewed or checked for conformity to USGS editorial standards or stratigraphic nomenclature, and it has not been digitized. This version of the map is unchanged from that submitted to the USGS for publication shortly after the 1980 eruption of Mount St. Helens and includes unresolved inconsistencies with the subsequently published work of Crandell (1987) and Mullineaux (1996). Nevertheless, it is the most accurate available depiction of the pre-1980 edifice and is published here for comparison with more recent geologic mapping and historical perspectives.

Open-File Report↗

USGS2003

Spatial digital database for the geologic map of Nevada

This report publishes a geologic digital spatial database (NVGEO) for the geologic map of Nevada by Stewart and Carlson (1978a) which was originally printed on a single sheet of paper at a scale of 1:500,000 (and later reprinted on two sheets in 1991). The spatial digital database (GIS) provided in this report supersedes earlier digital editions by Turner and Bawiec (1991) and Raines and others (1996).

Open-File Report↗

USGS1987

Preliminary geologic map of the Mount Katmai Quadrangle and portions of the Afognak and Naknek quadrangles, Alaska

This geologic map is the first in a series of maps dealing with geology and mineral resources of the Mt. Katmai area, Alaska. This map series is the result of the U.S. Geological Survey's Alaska Mineral Resources Assessment Program (AMRAP). Subsequent maps in this series will treat fossils, geochronology, detailed Quaternary deposits (both unconsolidated and volcanic), and mineral resources.

Alaska↗

USGS1999

Digital Geologic Map of the Wallace 1:100,000 Quadrangle, Idaho

The geology of the Wallace 1:100,000 quadrangle, Idaho was compiled by Reed S. Lewis in 1997 primarily from published materials including 1983 data from Foster, Harrison's unpublished mapping done from 1975 to 1985, Hietenan's 1963, 1967, 1968, and 1984 mapping, Hobbs and others 1965 mapping, and Vance's 1981 mapping, supplemented by eight weeks of field mapping by Reed S. Lewis, Russell F. Burmester, and Mark D. McFaddan in 1997 and 1998. This geologic map information was inked onto a 1:100,000-scale greenline mylar of the topographic base map for input into a geographic information system (GIS). The resulting digital geologic map GIS can be queried in many ways to produce a variety of geologic maps. Digital base map data files (topography, roads, towns, rivers and lakes, etc.) are not included: they may be obtained from a variety of commercial and government sources. This database is not meant to be used or displayed at any scale larger than 1:100,000 (e.g., 1:62,500 or 1:24,000). The map area is located in north Idaho. The primary sources of map data are shown in figure 2 and additional sources are shown in figure 3. This open-file report describes the geologic map units, the methods used to convert the geologic map data into a digital format, the Arc/Info GIS file structures and relationships, and explains how to download the digital files from the U.S. Geological Survey public access World Wide Web site on the Internet. Mapping and compilation was completed by the Idaho Geological Survey under contract with the U.S. Geological Survey (USGS) office in Spokane, Washington. The authors would like to acknowledge the help of the following field assistants: Josh Goodman, Yvonne Issak, Jeremy Johnson and Kevin Myer. Don Winston provided help with our ongoing study of Belt stratigraphy, and Tom Frost assisted with logistical problems and sample collection. Manuscript reviews by Steve Box, Tom Frost, and Brian White are greatly appreciated. We wish to thank Karen S. Bolm of the USGS for reviewing the digital files.

Open-File Report↗

USGS2007

Geologic map of Wupatki National Monument and vicinity, Coconino County, Northern Arizona

Introduction The geologic map of Wupatki National Monument is a cooperative effort between the U.S. Geological Survey, the National Park Service, and the Navajo Nation to provide geologic information for resource management officials of the National Park Service, U.S. Forest Service, Navajo Indian Reservation (herein the Navajo Nation), and visitor information services at Wupatki National Monument, Arizona. Funding for the map was provided in part by the Water Rights Branch of the Water Resources Division of the National Park Service. Field work on the Navajo Nation was conducted under a permit from the Navajo Nation Minerals Department. Any persons wishing to conduct geologic investigations on the Navajo Nation must first apply for, and receive, a permit from the Navajo Nation Minerals Department, P.O. Box 1910, Window Rock, Arizona 86515, telephone (928)-871-6587. Wupatki National Monument lies within the USGS 1:24,000-scale Wupatki NE, Wupatki SE, Wupatki SW, Gray Mountain, East of SP Mountain, and Campbell Francis Wash quadrangles in northern Arizona. The map is bounded approximately by longitudes 111? 16' to 111? 32' 30' W. and latitudes 35? 30' to 35? 37' 40' N. The map area is in Coconino County on the southern part of the Colorado Plateaus geologic province (herein Colorado Plateau). The map area is locally subdivided into three physiographic parts, the Coconino Plateau, the Little Colorado River Valley, and the San Francisco Volcanic Field as defined by Billingsley and others (1997) [fig. 1]. Elevations range from 4,220 ft (1,286 m) at the Little Colorado River near the northeast corner of the map area to about 6,100 ft (1,859 m) at the southwest corner of the map area. The small community of Gray Mountain is about 16 mi (26 km) northwest of Wupatki National Monument Visitor Center, and Flagstaff, Arizona, the nearest metropolitan area, is about 24 mi (38 km) southwest of the Visitor Center (fig. 1). U.S. Highway 89 provides access to the west entrance of Wupatki National Monument. A paved Coconino County road provides a loop from Wupatki National Monument south to Sunset Crater National Monument and back to U.S. Highway 89 about 10 mi (16 km) north of Flagstaff, Arizona. Access to Coconino National Forest is via dirt roads maintained by the National Forest Service. Several unimproved dirt roads on Babbitt Ranch lands provide limited access to remote areas north of Wupatki National Monument. Travel is mostly restricted to paved roads within Wupatki National Monument, and a dirt road that crosses the Little Colorado River provides access to the Navajo Nation area east and northeast of the Little Colorado River. The Little Colorado River crossing is not bridged and can be impassable when the river is flowing. Four-wheel-drive vehicles are recommended but not necessary for travel in remote parts of the Navajo Nation. Extra food and water are highly recommended for travel in this sandy area. Land ownership north of Wupatki National Monument forms a checkerboard pattern between private and State land. Coconino National Forest manages lands south of Wupatki National Monument and the National Park Service manages Wupatki National Monument. The Leupp and Tolani Lake Chapters of the Navajo Nation manage the area northeast and east of the Little Colorado River (see land management boundaries on map). The geologic map of Wupatki National Monument provides updated geologic framework information for this part of the Colorado Plateau. The geologic information supports Federal, State, and private land managers when conducting geologic, biologic, and hydrologic investigations and will support future and ongoing geologic and associated scientific investigations of all disciplines within the Wupatki National Monument area.

Arizona↗

USGS2015

Geologic map of the Patagonia Mountains, Santa Cruz County, Arizona

The Patagonia Mountains contain two large porphyry Cu-Mo systems each with separate associated hypogene and supergene zones, two high-grade Cu-Mo breccia pipes, one large epithermal Ag-Pb-Zn-Mn deposit, and numerous additional areas of base- and precious-metal mineralization all zoned around a Laramide-age composite batholith of intermediate composition. Compilations and new work by Vikre and others (2014) have identified as many as eight separate intrusive phases of the batholith and five separate hydrothermal events spanning at least 16 m.y., in addition to a supergene enrichment event of middle Tertiary age. The geologic map presents a spatial context for this important new information that is intended to support further work in this highly mineralized region. Several spatial databases provide data for the geologic map of the Patagonia Mountains in Arizona. The data can be viewed and queried in ArcGIS 10, a geographic information system; a geologic map is also available in PDF format. All products are available online only.

Arizona↗

USGS2014

Geologic map of the eastern quarter of the Flagstaff 30’ x 60’ quadrangle, Coconino County, northern Arizona

The eastern quarter of the Flagstaff 30′ x 60′ quadrangle includes eight USGS 1:24,000-scale quadrangles in Coconino County, northern Arizona (fig. 1, map sheet): Anderson Canyon, Babbitt Wash, Canyon Diablo, Grand Falls, Grand Falls SE, Grand Falls SW, Grand Falls NE, and Meteor Crater. The map is bounded by lat 35° to 35°30′ N. and long 111° to 111°15′ W. and is on the southern part of the Colorado Plateaus geologic province (herein Colorado Plateau). Elevations range from 4,320 ft (1,317 m) at the Little Colorado River in the northwest corner of the map area to about 6,832 ft (2,082 m) at the southwest corner of the map. This geologic map provides an updated geologic framework for the eastern quarter of the Flagstaff 30′ x 60′ quadrangle and is adjacent to two other recent geologic maps, the Cameron and Winslow 30′ x 60′ quadrangles (Billingsley and others, 2007, 2013). This geologic map is the product of a cooperative effort between the U.S. Geological Survey (USGS) and the Navajo Nation. It provides geologic information for resource management officials of the U.S. Forest Service, the Arizona Game and Fish Department, and the Navajo Nation Reservation (herein the Navajo Nation). Funding for the map was provided by the USGS geologic mapping program, Reston, Virginia. Field work on the Navajo Nation was conducted under a permit from the Navajo Nation Minerals Department. Any persons wishing to conduct geologic investigations on the Navajo Nation must first apply for, and receive, a permit from the Navajo Nation Minerals Department, P.O. Box 1910, Window Rock, Arizona 86515, telephone (928) 871-6587.

Arizona↗

USGS2020

Geologic map of the northern Harrat Rahat volcanic field, Kingdom of Saudi Arabia

Harrat Rahat, in the west-central part of the Kingdom of Saudi Arabia, is the largest of 15 Cenozoic harrats (Arabic for “volcanic field”) distributed on the Arabian plate. It extends more than 300 km north-south and 50 to 75 km east-west, and it covers an area of approximately 20,000 km 2 , has a volume of approximately 2,000 km 3 , and encompasses more than 900 observable vents. Volcanism commenced around 10 Ma and has continued into historic time, the most recent eruption occurring in 1256 C.E. Volcanic products are dominated by alkali basalt and hawaiite lava flows, with subordinate mugearite lava flows, as well as benmoreite and trachyte lava flows, domes, and pyroclastic flows. This geologic map distinguishes 239 eruptive units that cover an area of 3,340 km 2 in northern Harrat Rahat and the adjacent city of Al-Madinah. Results are presented as a geologic map of the study area at 1:75,000 scale and of smaller regions of particular interest at 1:25,000 scale, along with interpretive text. Most units are basaltic lava flows that erupted from the broadly north-northwest-trending main vent axis that constructed the topographic crest of the volcanic field. This 300- to 400-m-high vent axis, which has a width of 6 to 10 km, lies in the eastern one-third of northern Harrat Rahat. Basalt and hawaiite lava flows can extend as far as 27 km from their vents, but most are 10 to 15 km long. Evolved products such as mugearites, benmoreites, and trachytes are less extensive; the trachytic pyroclastic flows extend as far as 9 km from their source vents, although most only reach 4 to 6 km. Vents of the evolved products are restricted to the main vent axis or its flanks. No volcanic rocks older than 1.2 Ma are exposed in the map area, and about 90 percent of the exposed volcanic rocks erupted during the past 570 thousand years. As depicted on the geologic maps, eruption ages and field relations define 12 eruptive stages for northern Harrat Rahat for the past 1.2 million years. Other important geochronological findings include (1) several late Pleistocene lava flows near Al-Madinah, which previously were interpreted as Holocene from archeological evidence; (2) the eruption age of a cluster of cinder cones and small lava flows in the western outskirts of Al-Madinah (previously ascribed to an eruption in 641 C.E.) is actually 13.3±1.9 ka, close to the Pleistocene-Holocene boundary; and (3) only two Holocene eruptions have been identified in the map area, those of the historically described basalt of Al Labah in 1256 C.E. and the dome and pyroclastic flows of the trachyte of Um Rgaibah at 4.2±5.2 ka.

Scientific Investigations Map↗

USGS1994

Quaternary Geologic Map of the Lake Nipigon 4 Degrees x 6 Degrees Quadrangle, United States and Canada

The Quaternary Geologic Map of the Lake Nipigon 4 degree x 6 degree Quadrangle was mapped as part of the Quaternary Geologic Atlas of the United States. The atlas was begun as an effort to depict the areal distribution of surficial geologic deposits and other materials that accumulated or formed during the past 2+ million years, the period that includes all activities of the human species. These materials are at the surface of the earth. They make up the 'ground' on which we walk, the 'dirt' in which we dig foundations, and the 'soil' in which we grow crops. Most of our human activity is related in one way or another to these surface materials that are referred to collectively by many geologists as regolith, the mantle of fragmental and generally unconsolidated material that overlies the bedrock foundation of the continent. The maps were compiled at 1:1,000,000 scale. This map is a product of collaboration of the Ontario Geological Survey, the University of Michigan, and the U.S. Geological Survey, and is designed for both scientific and practical purposes. It was prepared in two stages. First, separate maps and map explanations were prepared by the compilers. Second, the maps were combined, integrated, and supplemented by the editor. Map unit symbols were revised to a uniform system of classification and the map unit descriptions were prepared by the editor from information received from the compilers and from additional sources listed under Sources of Information. Diagrams accompanying the map were prepared by the editor. For scientific purposes, the map differentiates Quaternary surficial deposits on the basis of lithology or composition, texture or particle size, structure, genesis, stratigraphic relationships, engineering geologic properties, and relative age, as shown on the correlation diagram and indicated in the map unit descriptions. Deposits of some constructional landforms, such as kame moraine deposits, are distinguished as map units. Deposits of erosional landforms, such as outwash terraces, are not distinguished, although glaciofluvial, ice-contact, and lacustrine deposits that are mapped may be terraced. As a Quaternary geologic map it serves as a base from which a variety of maps relating Quaternary geologic history can be derived. For practical purposes, the map is a surficial materials map. Materials are distinguished on the basis of lithology or composition, texture or particle size, and other physical, chemical, and engineering characteristics. It is not a map of soils that are recognized and classified in pedology or agronomy. Rather, it is a generalized map of soils as recognized in engineering geology, or of substrata or parent materials in which pedologic or agronomic soils are formed. As a materials map it serves as a base from which a variety of maps for use in planning engineering, land use, or land management projects can be derived.

IMAP↗

USGS2001

Geologic map and database of the Roseburg 30' x 60' quadrangle, Douglas and Coos Counties, Oregon

The Roseburg 30' x 60' Quadrangle covers the southeastern margin of the Oregon Coast Range and its tectonic boundary with Mesozoic terranes of the Klamath Mountains (see figures 1 and 2 in pamphlet, also shown on map sheet). The geologic framework of the Roseburg area was established by the pioneering work of Diller (1898), Wells and Peck, (1961) and Ewart Baldwin (1974) and his students (see figure 3 in pamphlet, also shown on map sheet). Baldwin and his students focussed on the history of the Eocene Tyee basin, where the sediments lap across the tectonic boundary with the Mesozoic terranes and record the accretion of the Coast Range basement to the continent. Others have examined the sedimentary fill of the Tyee basin in detail, recognizing the deep marine turbidite facies of the Tyee Formation (Snavely and others, 1964) and proposing several models for the Eocene evolution of the forearc basin (Heller and Ryberg, 1983; Chan and Dott, 1983; Heller and Dickinson, 1985; Molenaar, 1985; see Ryu and others, 1992 for a comprehensive summary). Along the eastern margin of the quadrangle, both the Tyee basin and the Klamath terranes are overlain by Eocene volcanic rocks of the Western Cascade arc (Walker and MacLeod, 1991). The thick Eocene sedimentary sequence of the Tyee basin has significant oil and gas potential (Armentrout and Suek, 1985; Gautier and others, 1993; Ryu and others, 1996). Although 13 deep test wells have been drilled in the Roseburg quadrangle (see figure 2 and table 1 in pamphlet, also shown on map sheet), exploration to date has been hampered by an incomplete understanding of the basinï¿½s tectonic setting and evolution. In response, the Oregon Department of Geology and Mineral Industries (DOGAMI) initiated a five year assessment of the oil and gas potential of the Tyee basin. This map is a product of a cooperative effort by the U. S. Geological Survey, Oregon State University, and DOGAMI to systematically map the sedimentary facies and structure of the Tyee basin. New geologic mapping of twenty-eight 7.5' quadrangles is summarized on the map (see figure 3, also shown on map sheet), and the digital database contains geologic information suitable for both 1:100K and 1:24K scale analysis. DOGAMI has published a compilation and synthesis of previous mapping (Niem and Niem, 1990), a basin-wide sequence stratigraphic model and correlations (Ryu and others, 1992), and a report on the oil and gas potential (Ryu and others, 1996). Readers interested in the oil and gas potential of the Roseburg quadrangle should use the map in combination with Ryu and others (1996) to address specific stratigraphic units and structural plays. Stratigraphic terminology for the Tyee basin adopts the type sections, formation names, and framework of Ryu and others (1992, 1996), which were developed concurrently with the mapping and are recognized throughout the basin. For detailed discussion of nomenclature, type sections, lithology, thickness and distribution, age, contact relationships, and depositional environment of stratigraphic units, the reader is referred to Ryu and others (1992). In this report we focus on the spatial, temporal, and structural relationships between units revealed by geologic mapping. Map unit ages (see figure 4 in pamphlet, also shown on map sheeet) are adjusted slightly from Ryu and others (1992, 1996) to fit new coccolith age determinations (D. Bukry, cited in pamphlet), paleomagnetic polarity data (Simpson, 1977 and new data cited in pamphlet), and the time scale of Berggren and others (1995).

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