Geology topics

Pamela M. Cossette

Publications and source records attributed to Pamela M. Cossette.

15 recordsLinked to original sources

USGS2023

Preliminary geologic map of the Southern Santa Rosa Mountains and Borrego Badlands, San Diego County, Southern California

This investigation delineates the geologic framework of an area of 75 square kilometers (km 2 ) located west of the Salton Sea in southern California (fig. 1, on sheet 1). The study area encompasses the south flank of the Santa Rosa Mountains and the eastern part of the Borrego Badlands (sheet 1). In this study area, regionally important stratigraphic and structural elements collectively inform the late Cenozoic geologic evolution of the Anza-Borrego sector of the Salton Trough province. Critical stratigraphic and structural elements in the map area include the following: The well exposed sequence of late Cenozoic, nonmarine sedimentary rocks that filled the Anza-Borrego subbasin (fig. 1) of the Salton Trough; A tectonic boundary that—in the southern Santa Rosa Mountains—separates the sedimentary strata from underlying crystalline rocks of Peninsular Ranges type. This tectonic boundary, named the West Salton Detachment Fault System by Axen and Fletcher (1998), is projected to underlie all late Cenozoic sedimentary strata in the Anza-Borrego subbasin of the Salton Trough; A variety of transpressional, transtensional, and strike-slip structures that have deformed the late Cenozoic sedimentary strata and collectively guided syntectonic and posttectonic depositional events within the Anza-Borrego subbasin of the Salton Trough; and The southeasternmost surface expression of the Clark Fault, a major strand of the dextral San Jacinto Fault Zone. Geologic mapping and analysis for this investigation focused on clarifying geologic relations among these four stratigraphic and structural aspects in the map area.

California↗

USGS2023

Surficial geologic map of the Owlshead Mountains 30' x 60' quadrangle, Inyo and San Bernardino Counties, California

The surficial geologic map of the Owlshead Mountains 30' x 60' quadrangle depicts the distribution and characteristics of surficial-deposit materials and neotectonic deformation for an area of approximately 5,000 square kilometers (km 2 ) located in the western Basin and Range Province of eastern California. The map represents a new compilation of the surficial geology that encompasses deposits within the late Pliocene to Quaternary. The map is based primarily on new mapping conducted between 2001 and 2009. Map compilation was supported by field observations distributed across the map area, combined with reference to several published and unpublished mapping sources that mostly emphasized neotectonic deformation. The surficial-deposit units included in the map follow a classification scheme that systematically denotes depositional process, relative age, and any secondary sedimentologic or morphologic characteristics. Identification, correlation, and age estimation of map units are based primarily on the relative degree of development of certain time-dependent characteristics such as surface morphology, including local dissection and surface preservation, surface clast modification, and degree of soil development; these characteristics are implicitly incorporated into unit designations. The map represents a detailed and regionally uniform synthesis of the late Neogene geology for this large area that provides a framework applicable to many interpretative studies, such as regional patterns of deposition and dissection; surface drainage development and evolution; and the distribution, style, and timing of neotectonic deformation.

California↗

USGS2021

Mineral resource inventory of North Dakota

Aside from construction aggregate materials, the value of nonfuel mineral commodities that have been produced in North Dakota is small, although there is potential for the existence of several mineral resource deposit types which are not economically viable at this time. In this report, we present a mineral resource inventory of the State of North Dakota, developed by the U.S. Geological Survey at the request the Bureau of Land Management. To set the stage for that inventory, we briefly outline the long and complex geologic history of North Dakota that extends back more than 3 billion years. Using several existing databases, we summarize the distribution of known mineral commodities and the results of commodity exploration over time. Using all available data, we discuss the potential for economic occurrences of 13 commodities in North Dakota, including some listed as Critical Minerals.

North Dakota↗

USGS2018

Geologic map and database of the Chocolate Mountain Aerial Gunnery Range, Riverside and Imperial Counties, California

The northwest-trending Chocolate Mountains are situated along the northeastern margin of the southern Salton Trough. The Chocolate Mountain Aerial Gunnery Range occupies most of the 75-km-long part of the Chocolate Mountains that lies between Salt Creek to the north and California State Highway 78 to the south. Mapping studies in the Chocolate Mountains within the gunnery range are few and this study was conducted in cooperation with the U.S. Navy (Naval Facilities Engineering Command Southwest, San Diego, California) and U.S. Marine Corps (Range Management Department, Marine Corps Air Station, Yuma, Arizona). Crystalline basement rocks in the Chocolate Mountains range in age from early Proterozoic to middle Cenozoic. Early and middle Proterozoic metamorphosed sedimentary and plutonic rocks include sillimanite-biotite-quartz feldspar gneiss, layered biotite-quartz-feldspar gneiss, biotite-quartz-feldspar augen gneiss, and largely undeformed late Proterozoic anorthosite and syenite. These rock types, which crop out as dispersed domains in the Chocolate Mountains, are remnants—along with more extensive domains observed in the Eastern Transverse Ranges to the north and in the San Gabriel Mountains to the northwest—of an originally more continuous assemblage that has been dextrally displaced along strands of the San Andreas Fault System.

California↗

USGS2016

Geology and mineral resources of the Sheldon-Hart Mountain National Wildlife Refuge Complex (Oregon and Nevada), the Southeastern Oregon and North-Central Nevada, and the Southern Idaho and Northern Nevada (and Utah) Sagebrush Focal Areas: Chapter B in Mineral resources of the Sagebrush Focal Areas of Idaho, Montana, Nevada, Oregon, Utah, and Wyoming

Summary The U.S. Department of the Interior has proposed to withdraw approximately 10 million acres of Federal lands from mineral entry (subject to valid existing rights) from 12 million acres of lands defined as Sagebrush Focal Areas (SFAs) in Idaho, Montana, Nevada, Oregon, Utah, and Wyoming (for further discussion on the lands involved see Scientific Investigations Report 2016–5089–A). The purpose of the proposed action is to protect the greater sage-grouse ( Centrocercus urophasianus ) and its habitat from potential adverse effects of locatable mineral exploration and mining. The U.S. Geological Survey Sagebrush Mineral-Resource Assessment (SaMiRA) project was initiated in November 2015 and supported by the Bureau of Land Management to (1) assess locatable mineral-resource potential and (2) to describe leasable and salable mineral resources for the seven SFAs and Nevada additions. This chapter summarizes the current status of locatable, leasable, and salable mineral commodities and assesses the potential of selected locatable minerals in lands proposed for withdrawal that span the Nevada, Oregon, Idaho, and Utah borders. In this report, the four study areas evaluated were (1) the Sheldon-Hart Mountain National Wildlife Refuge Complex SFA in Washoe County, Nevada, and Harney and Lake Counties, Oregon; (2) the Southeastern Oregon and North-Central Nevada SFA in Humboldt County, Nevada, and Harney and Malheur Counties, Oregon; (3) the Southern Idaho and Northern Nevada SFA in Cassia, Owyhee, and Twin Falls Counties, Idaho, Elko County, Nevada, and Box Elder County, Utah; and (4) the Nevada additions in Humboldt and Elko Counties, Nevada.

Idaho, Nevada, Oregon, Utah↗

USGS2016

Geologic history of the Blackbird Co-Cu district in the Lemhi subbasin of the Belt-Purcell Basin

The Blackbird cobalt-copper (Co-Cu) district in the Salmon River Mountains of east-central Idaho occupies the central part of the Idaho cobalt belt—a northwest-elongate, 55-km-long belt of Co-Cu occurrences, hosted in grayish siliciclastic metasedimentary strata of the Lemhi subbasin (of the Mesoproterozoic Belt-Purcell Basin). The Blackbird district contains at least eight stratabound ore zones and many discordant lodes, mostly in the upper part of the banded siltite unit of the Apple Creek Formation of Yellow Lake, which generally consists of interbedded siltite and argillite. In the Blackbird mine area, argillite beds in six stratigraphic intervals are altered to biotitite containing over 75 vol% of greenish hydrothermal biotite, which is preferentially mineralized. Past production and currently estimated resources of the Blackbird district total ~17 Mt of ore, averaging 0.74% Co, 1.4% Cu, and 1.0 ppm Au (not including downdip projections of ore zones that are open downward). A compilation of relative-age relationships and isotopic age determinations indicates that most cobalt mineralization occurred in Mesoproterozoic time, whereas most copper mineralization occurred in Cretaceous time. Mesoproterozoic cobaltite mineralization accompanied and followed dynamothermal metamorphism and bimodal plutonism during the Middle Mesoproterozoic East Kootenay orogeny (ca. 1379–1325 Ma), and also accompanied Grenvilleage (Late Mesoproterozoic) thermal metamorphism (ca. 1200–1000 Ma). Stratabound cobaltite-biotite ore zones typically contain cobaltite 1 in a matrix of biotitite ± tourmaline ± minor xenotime (ca. 1370–1320 Ma) ± minor chalcopyrite ± sparse allanite ± sparse microscopic native gold in cobaltite. Such cobaltite-biotite lodes are locally folded into tight F 2 folds with axial-planar S 2 cleavage and schistosity. Discordant replacement-style lodes of cobaltite 2 -biotite ore ± xenotime 2 (ca. 1320–1270 Ma) commonly follow S 2 fractures and fabrics. Discordant quartz-biotite and quartz-tourmaline breccias, and veins contain cobaltite 3 ± xenotime 3 (ca. 1058–990 Ma). Mesoproterozoic cobaltite deposition was followed by: (1) within-plate plutonism (530–485 Ma) and emplacement of mafic dikes (which cut cobaltite lodes but are cut by quartz-Fe-Cu-sulfide veins); (2) garnet-grade metamorphism (ca. 151–93 Ma); (3) Fe-Cu-sulfide mineralization (ca. 110–92 Ma); and (4) minor quartz ± Au-Ag ± Bi mineralization (ca. 92–83 Ma). Cretaceous Fe-Cu-sulfide vein, breccia, and replacement-style deposits contain various combinations of chalcopyrite ± pyrrhotite ± pyrite ± cobaltian arsenopyrite (not cobaltite) ± arsenopyrite ± quartz ± siderite ± monazite (ca. 144–88 Ma but mostly 110–92 Ma) ± xenotime (104–93 Ma). Highly radiogenic Pb (in these sulfides) and Sr (in siderite) indicate that these elements resided in Mesoproterozoic source rocks until they were mobilized after ca. 100 Ma. Fe-Cu-sulfide veins, breccias, and replacement deposits appear relatively undeformed and generally lack metamorphic fabrics. Composite Co-Cu-Au ore contains early cobaltite-biotite lodes, cut by Fe-Cu-sulfide veins and breccias, or overprinted by Fe-Cu-sulfide replacement-style deposits, and locally cut by quartz veinlets ± Au-Ag ± Bi minerals.

Idaho↗

USGS2015

Geology of Joshua Tree National Park geodatabase

The database in this Open-File Report describes the geology of Joshua Tree National Park and was completed in support of the National Cooperative Geologic Mapping Program of the U.S. Geological Survey (USGS) and in cooperation with the National Park Service (NPS). The geologic observations and interpretations represented in the database are relevant to both the ongoing scientific interests of the USGS in southern California and the management requirements of NPS, specifically of Joshua Tree National Park (JOTR). Joshua Tree National Park is situated within the eastern part of California’s Transverse Ranges province and straddles the transition between the Mojave and Sonoran deserts. The geologically diverse terrain that underlies JOTR reveals a rich and varied geologic evolution, one that spans nearly two billion years of Earth history. The Park’s landscape is the current expression of this evolution, its varied landforms reflecting the differing origins of underlying rock types and their differing responses to subsequent geologic events. Crystalline basement in the Park consists of Proterozoic plutonic and metamorphic rocks intruded by a composite Mesozoic batholith of Triassic through Late Cretaceous plutons arrayed in northwest-trending lithodemic belts. The basement was exhumed during the Cenozoic and underwent differential deep weathering beneath a low-relief erosion surface, with the deepest weathering profiles forming on quartz-rich, biotite-bearing granitoid rocks. Disruption of the basement terrain by faults of the San Andreas system began ca. 20 Ma and the JOTR sinistral domain, preceded by basalt eruptions, began perhaps as early as ca. 7 Ma, but no later than 5 Ma. Uplift of the mountain blocks during this interval led to erosional stripping of the thick zones of weathered quartz-rich granitoid rocks to form etchplains dotted by bouldery tors—the iconic landscape of the Park. The stripped debris filled basins along the fault zones. Mountain ranges and basins in the Park exhibit an east-west physiographic grain controlled by left-lateral fault zones that form a sinistral domain within the broad zone of dextral shear along the transform boundary between the North American and Pacific plates. Geologic and geophysical evidence reveal that movement on the sinistral faults zones has resulted in left steps along the zones, resulting in the development of sub-basins beneath Pinto Basin and Shavers and Chuckwalla Valleys. The sinistral fault zones connect the Mojave Desert dextral faults of the Eastern California Shear Zone to the north and east with the Coachella Valley strands of the southern San Andreas Fault Zone to the west. Quaternary surficial deposits accumulated in alluvial washes and playas and lakes along the valley floors; in alluvial fans, washes, and sheet wash aprons along piedmonts flanking the mountain ranges; and in eolian dunes and sand sheets that span the transition from valley floor to piedmont slope. Sequences of Quaternary pediments are planed into piedmonts flanking valley-floor and upland basins, each pediment in turn overlain by successively younger residual and alluvial surficial deposits.

California↗

USGS2014

Porphyry copper assessment of eastern Australia

The U.S. Geological Survey (USGS) conducts national and global assessments of resources (mineral, energy, water, and biologic) to provide science in support of decision making. Mineral resource assessments provide syntheses of available information about where mineral deposits are known and suspected to occur in the Earth’s crust and which commodities may be present, together with estimates of amounts of resources that may be present in undiscovered deposits. The USGS collaborated with geologists of the Geological Survey of New South Wales and Geoscience Australia (formerly the Australian Geological Survey Organisation) on an assessment of Phanerozoic-age porphyry copper resources in Australia. Porphyry copper deposits contain about 11 percent of the identified copper resources in Australia. This study addresses resources of known porphyry copper deposits and expected resources of undiscovered porphyry copper deposits in eastern Australia. A three-part form of assessment was used for estimation of undiscovered resources. Using this method, four tracts were delineated that are permissive for porphyry copper deposits. A probabilistic estimate of the expected number of deposits in each tract was prepared on the basis of existing information about geology, geochemistry, geophysics, exploration history, and mineral occurrences. Monte Carlo simulation was used to combine the estimated number of deposits with an appropriate model of grade and tonnage for porphyry copper deposits to provide a probabilistic estimate of metal content and total tonnage for undiscovered deposits. The Delamerian permissive tract comprises igneous rocks of Cambrian age in the Delamerian Orogen, which borders the western margin of the Tasmanides. The Delamerian tract contains no known porphyry copper deposits, but the Adelaide sub-tract, one of three sub-tracts that compose the Delamerian tract, contains four porphyry copper prospects. The Adelaide sub-tract is estimated to contain 2.5±2.2 undiscovered deposits in an area of about 50,700 square kilometers. The Macquarie permissive tract comprises volcanic, volcaniclastic, and minor exposed intrusive igneous rocks of the Macquarie Arc. The nine known deposits in this tract are now estimated to contain a total of about 13.5 million metric tons of copper and 1,700 metric tons of gold. This tract is estimated to contain 6.9±3.5 undiscovered deposits for a total of about 16 deposits in an area of about 41,500 square kilometers. The Yeoval permissive tract includes subequal areas of permissive volcanic and intrusive rocks of Silurian to Devonian age exposed in and around the Cowra-Buchan Rift System, which overlaps the previously accreted Macquarie Arc. The Yeoval tract contains one porphyry copper deposit and several porphyry copper prospects. This tract is estimated to contain 1.3±0.75 undiscovered porphyry copper deposits, for a total of about 2 expected deposits in an area of about 53,200 square kilometers. The East Tasmanide permissive tract includes a semi-continuous belt of plutonic and subordinate volcanic rocks along the eastern margins of Queensland and northeastern New South Wales. The East Tasmanide tract contains 14 known porphyry copper deposits and many porphyry copper prospects, which are all in the Central sub-tract. This sub-tract is expected to contain 4.8±3.3 undiscovered porphyry copper deposits, for a total of about 19 deposits in an area of about 291,000 square kilometers. This assessment estimates that 15 undiscovered deposits contain an arithmetic mean of ~21 million metric tons or more of copper in four tracts, in addition to the 24 known porphyry copper deposits that contain identified resources of ~16 million metric tons of copper. In addition to copper, the mean expected amount of undiscovered byproduct gold predicted by the simulation is ~1,500 metric tons. The probability associated with these arithmetic means is on the order of 30 percent. Median expected amounts of metals predicted by the simulations may be ~50 percent lower than mean estimates.

Scientific Investigations Report↗

USGS2014

Assessment of undiscovered sandstone copper deposits of the Kodar-Udokan area, Russia

Mineral resource assessments integrate and synthesize available information as a basis for estimating the location, quality, and quantity of undiscovered mineral resources. This probabilistic mineral resource assessment of undiscovered sandstone copper deposits within Paleoproterozoic metasedimentary rocks of the Kodar-Udokan area in Russia is a contribution to a global assessment led by the U.S. Geological Survey (USGS). The purposes of this study are to (1) delineate permissive areas (tracts) to indicate where undiscovered sandstone-hosted copper deposits may occur within 2 km of the surface, (2) provide a database of known sandstone copper deposits and significant prospects, (3) estimate numbers of undiscovered deposits within these permissive tracts at several levels of confidence, and (4) provide probabilistic estimates of amounts of copper (Cu) and mineralized rock that could be contained in undiscovered deposits within each tract. The workshop for the assessment, held in October 2009, used a three-part form of mineral resource assessment as described by Singer (1993) and Singer and Menzie (2010). Permissive tracts were delineated by estimating the volume of rock that contains the stratigraphic section ranging from the Chitkanda to the Sakukan Formations of the Udokan Complex to a depth of 2 km and then projecting this rock volume to the surface. The six permissive tracts delineated in this assessment occur in several domains, referred to as troughs in Russian literature, which represent remnants of a much larger basin that likely covered the Kodar-Udokan region. Tracts range in size from about 100 km 2 to 800 km 2 . The mapped distributions of rocks as shown on 1:200,000-scale geologic maps, supplemented in some areas by prospect mapping and drilling, were used to delineate the tracts. In this study area, data are insufficient to constrain the original basin geometry or the structural or stratigraphic traps that would have localized copper mineralization. Some alteration is described, and the types of sandstone cements vary; however, no patterns are known that provide evidence for regional flow paths of metal-bearing brines that could localize deposits. This probabilistic assessment indicates that a significant amount of undiscovered copper is associated with sediment-hosted stratabound copper deposits in the Kodar-Udokan Trough. In the assessment, a mean of 21 undiscovered deposits is estimated to occur within the Kodar-Udokan area. There are two known deposits in the area that contain drill-identified resources of 19.6 million metric tons of copper. Using Monte Carlo simulation, probabilistic estimates of the numbers of undiscovered sandstone copper deposits for these tracts were combined with tonnage and grade distributions of sandstone copper deposits to forecast an arithmetic mean of 20.6 million metric tons of undiscovered copper. Significant value can be expected from associated metals, particularly silver.

Scientific Investigations Report↗

USGS2014

Sandstone copper assessment of the Teniz Basin, Kazakhstan

The U.S. Geological Survey (USGS) conducts national and global resource assessments (mineral, energy, water, and biological) to provide data and scientific analyses to support decision making. Three-part mineral resource assessments result in informed, unbiased, quantitative, and probabilistic estimates of undiscovered mineral resources and deposits. In particular, mineral assessment results inform decisions concerning land-use and mineral-resource development. A probabilistic mineral resource assessment of the sandstone subtype of sediment-hosted stratabound copper deposits in the Teniz Basin, Kazakhstan, was undertaken by the USGS. The Teniz Basin is located in Akmola Oblast, central and western Kazakhstan. With an areal extent of almost 78,000 km 2 , the basin contains many sediment-hosted stratabound copper prospects, none of which are well described, and the majority of which may belong to the sandstone subtype of sediment-hosted copper deposits. There are no known locations within the Teniz Basin currently mined for copper. Within the basin, however, map units permissive for the sandstone subtype of sediment-hosted stratabound copper deposits include (from oldest to youngest): the Middle Carboniferous Kiery Suite; the Middle to Upper Carboniferous Vladimirov Suite (a stratigraphic equivalent of the Dzhezkazgan Suite, Chu-Sarysu Basin); and the Upper Carboniferous or lowest Permian Kayraktin Suite. The multicolored sedimentary rocks of the Vladimirov Suite, in which 14 potentially ore-bearing horizons of gray beds have been recorded, have the greatest potential for undiscovered, sandstone subtype, sediment-hosted stratabound copper deposits. A quantitative mineral resource assessment has been completed that (1) delineates one 49,714 km 2 tract permissive for undiscovered, sandstone subtype, sediment-hosted stratabound copper deposits, and (2) provides probabilistic estimates of numbers of undiscovered deposits and probable amounts of copper resource contained in those deposits. The permissive tract delineated in this assessment encompasses no previously known sandstone subtype, sediment-hosted stratabound copper deposits. However, this assessment estimates (with 30 percent probability) that a mean of nine undiscovered sandstone subtype copper deposits may be present in the Teniz Basin and could contain a mean total of 8.9 million metric tons of copper and 7,500 metric tons of silver.

Teniz Basin↗

USGS2012

Sandstone copper assessment of the Chu-Sarysu Basin, Central Kazakhstan: Chapter E in Global mineral resource assessment

Mineral resource assessments represent a synthesis of available information to estimate the location, quality, and quantity of undiscovered mineral resources in the upper part of the Earth’s crust. This report presents a probabilistic mineral resource assessment of undiscovered sandstone copper deposits within the late Paleozoic Chu-Sarysu Basin in central Kazakhstan by the U.S. Geological Survey as a contribution to a global assessment of mineral resources. The purposes of this study are to: (1) provide a database of known sandstone copper deposits and significant prospects in this area, (2) delineate permissive areas (tracts) for undiscovered sandstone copper deposits within 2 km of the surface at a scale of 1:1,000,000, (3) estimate numbers of undiscovered deposits within these permissive tracts at several levels of confidence, and (4) provide probabilistic estimates of amounts of copper (Cu), silver (Ag), and mineralized rock that could be contained in undiscovered deposits within each tract. The assessment uses the three-part form of mineral resource assessment based on mineral deposit models (Singer, 1993; Singer and Menzie, 2010). Delineation of permissive tracts for resources is based on the distribution of a Carboniferous oxidized nonmarine clastic (red bed) stratigraphic sequence that lies between overlying Permian and underlying Devonian evaporite-bearing sequences. Subsurface information on the extent and depth of this red bed sequence and structural features that divide the basin into sub-basins was used to define four permissive tracts. Structure contour maps, mineral occurrence databases, drill hole lithologic logs, geophysical maps, soil geochemical maps, locations of producing gas fields, and evidence for former gas accumulations were considered in conjunction with descriptive deposit models and grade and tonnage models to guide the assessment team’s estimates of undiscovered deposits in each tract. The four permissive tracts are structural sub-basins of the Chu-Sarysu Basin and range in size from 750 to 65,000 km². Probabilistic estimates of numbers of undiscovered sandstone copper deposits were made for the four tracts by a group of experts. Using these probabilistic estimates, Monte Carlo simulation was used to estimate the amount of metal contained within each tract. The results of the simulation serve as the basis for estimates of the metal endowment. The team estimates that 26 undiscovered deposits occur within the Chu-Sarysu Basin, and that these deposits contain an arithmetic mean of at least 21.5 million metric tons (Mt) of copper and 21,900 metric tons (t) of silver. The undiscovered deposits are in addition to the 7 known deposits that contain identified resources of 27.6 Mt of copper. Sixty percent of the estimated mean undiscovered copper resources are associated with the two permissive tracts that contain the identified resources; the remaining estimated resources are associated with the two tracts that have no known deposits. For the three tracts that contain 95 percent of the estimated undiscovered copper resources, the probability that each tract contains its estimated mean or more is about 40 percent. For the tract with 5 percent of the estimated undiscovered cop-per resources, the probability that it contains that amount or more is 25 percent.

Chu-Sarysu Basin↗

USGS2008

Geologic Map of the Eastern Three-Quarters of the Cuyama 30' x 60' Quadrangle, California

The map area encompasses a large part of the western Transverse Ranges and southern Coast Ranges of southern California. The San Andreas fault (SAF) cuts the northern part of the map. The area south of the SAF, about 80 percent of the map area, encompasses several distinct tectonic blocks bounded by major thrust or reverse faults, including the Santa Ynez fault, Big Pine fault (and structurally continuous Pine Mountain fault), Tule Creek fault, Nacimiento fault, Ozena fault, Munson Creek fault, Morales fault, and Frazier Mountain Thrust System. Movement on these faults is as old as Miocene and some faults may still be active. In addition, the Paleocene Sawmill Mountain Thrust south of the SAF and the Pastoria Thrust north of the SAF place Cretaceous and older crystalline rocks above Pelona Schist (south of the SAF) and Rand Schist (north of the SAF). South of the SAF, each tectonic block contains a unique stratigraphy, reflecting either large-scale movement on bounding faults or different depositional environments within each block. On Mount Pinos and Frazier Mountain, intrusive and metamorphic rocks as old as Mesoproterozoic, but including voluminous Cretaceous granitoid rocks, underlie or are thrust above non-marine sedimentary rocks as old as Miocene. Elsewhere, marine and non-marine sedimentary rocks are as old as Cretaceous, dominated by thick sequences of both Eocene and Cretaceous marine shales and sandstones. Middle Miocene to early Oligocene volcanic rocks crop out in the Caliente Hills (part of Caliente Formation) and south of Mount Pinos (part of the Plush Ranch Formation). Fault-bounded windows of Jurassic Franciscan Complex ophiolitic rocks are evident in the southwest corner of the area. North of the SAF, marine and non-marine sedimentary rocks as old as Eocene and Miocene volcanic rocks overlie a crystalline basement complex. Basement rocks include Cretaceous intrusive rocks that range from monzogranite to diorite, and Jurassic to late Paleozoic intrusive and metamorphic rocks. The Jurassic to late Paleozoic intrusive rocks include diorite, gabbro, and ultramafic rocks, and the metasedimentary rocks include marble, quartzite, schist, and gneiss.

Scientific Investigations Map↗

USGS2004

Preliminary geologic map of the Big Bear City 7.5' Quadrangle, San Bernardino County, California

This data set maps and describes the geology of the Big Bear City 7.5' quadrangle, San Bernardino County, California. Created using Environmental Systems Research Institute's ARC/INFO software, the data base consists of the following items: (1) a rock-unit coverage and attribute tables (polygon and arc) containing geologic contacts, units and rock-unit labels as annotation which are also included in a separate annotation coverage, bbc_anno (2) a point coverage containing structural point data and (3) a coverage containing fold axes. In addition, the data set includes the following graphic and text products: (1) A PostScript graphic plot-file containing the geologic map, topography, cultural data, a Correlation of Map Units (CMU) diagram, a Description of Map Units (DMU), an index map, a regional geologic and structure map, and an explanation for point and line symbols; (2) PDF files of the Readme (including the metadata file as an appendix), and a screen graphic of the plot produced by the PostScript plot file. The geologic map describes a geologically complex area on the north side of the San Bernardino Mountains. Bedrock units in the Big Bear City quadrangle are dominated by (1) large Cretaceous granitic bodies ranging in composition from monzogranite to gabbro, (2) metamorphosed sedimentary rocks ranging in age from late Paleozoic to late Proterozoic, and (3) Middle Proterozoic gneiss. These rocks are complexly deformed by normal, reverse, and thrust faults, and in places are tightly folded. The geologic map database contains original U.S. Geological Survey data generated by detailed field observation and by interpretation of aerial photographs. The map data was compiled on base-stable cronoflex copies of the Big Bear City 7.5' topographic map, transferred to a scribe-guide and subsequently digitized. Lines, points, and polygons were edited at the USGS using standard ARC/INFO commands. Digitizing and editing artifacts significant enough to display at a scale of 1:24,000 were corrected. Within the database, geologic contacts are represented as lines (arcs), geologic units as polygons, and site-specific data as points. Polygon, arc, and point attribute tables (.pat, .aat, and .pat, respectively) uniquely identify each geologic datum.

Open-File Report↗

USGS2003

Geologic map and digital database of the Redlands 7.5' quadrangle, San Bernardino and Riverside Counties, California

This geologic database of the Redlands 7.5' quadrangle was prepared by the Southern California Areal Mapping Project (SCAMP), a regional geologic-mapping project sponsored jointly by the U.S. Geological Survey and the California Geological Survey. The database was developed as a contribution to the National Cooperative Geologic Mapping Program's National Geologic Map Database, and is intended to provide a general geologic setting of the Redlands quadrangle. The database and map provide information about earth materials and geologic structures, including faults and folds that have developed in the quadrangle due to complexities in the San Andreas Fault system. The Redlands 7.5' quadrangle contains earth materials and structures that provide insight into the late Cenozoic geologic evolution of the southern California Inland Empire region. Important stratigraphic and structural elements include (1) the modern trace of the San Andreas and San Jacinto faults and (2) late Tertiary and Quaternary sedimentary materials and geologic structures that formed during the last million years or so and that record complex geologic interactions within the San Andreas Fault system. These materials and the structures that deform them provide the geologic framework for investigations of earthquake hazards and ground-water recharge and subsurface flow. Geologic information contained in the Redlands database is general-purpose data that is applicable to land-related investigations in the earth and biological sciences. The term "general-purpose" means that all geologic-feature classes have minimal information content adequate to characterize their general geologic characteristics and to interpret their general geologic history. However, no single feature class has enough information to definitively characterize its properties and origin. For this reason the database cannot be used for site-specific geologic evaluations, although it can be used to plan and guide investigations at the site-specific level. This summary pamphlet discusses major categories of surficial materials in the Redlands quadrangle, and provides a conceptual framework and basis for how geologicmap units containing such materials are recognized and correlated.

California↗

USGS2002

Geologic map and digital database of the San Bernardino Wash 7.5 minute quadrangle, Riverside County, California

The geologic map and digital database of the San Bernardino Wash quadrangle are products of a regional geologic mapping effort undertaken in the eastern Transverse Ranges in and around Joshua Tree National Park. This investigation, part of the Southern California Areal Mapping Project (SCAMP), is conducted in cooperation with the California Geologic Survey and the National Park Service. In line with the goals of the National Cooperative Geologic Mapping Program (NCGMP), mapping of the San Bernardino Wash and other quadrangles has been directed toward generating a multipurpose digital geologic map database that is applicable to land-related investigations in the earth and biological sciences. This mapping is conducted to further understanding of bedrock geology and surficial processes in the region and to document evidence for seismotectonic activity in the eastern Transverse Ranges. It is also intended to serve as a base layer suitable for ecosystem and mineral resource assessment and for building a hydrogeologic framework for Pinto Basin. Initial investigations span Pinto Basin from the Hexie and Eagle Mountains northward into the Pinto Mountains (see fig. 1). Quadrangles mapped include the Conejo Well 7.5-minute quadrangle (Powell, 2001a), the Porcupine Wash 7.5-minute quadrangle (Powell, 2001b), the Pinto Mountain 7.5-minute quadrangle (Powell, 2002), and the San Bernardino Wash 7.5-minute quadrangle. Parts of the San Bernardino Wash quadrangle had been mapped previously at a variety of scales (Weir, and Bader, 1963; Hope, 1966, 1969; Jennings, 1967; Powell, 1981, 1993).

California↗