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At least 1,081 records · Page 60Linked to original sources
USGS2021

An assessment of the economic potential of lignite and leonardite resources in the Williston Basin, North Dakota

The Bureau of Land Management (BLM) requested assistance from the U.S. Geological Survey (USGS) to conduct an assessment study to identify areas that may have economic potential for the future extraction of lignite and leonardite resources in the Williston Basin in North Dakota. The study will be used by the BLM to assist with the preparation of a revised resource management plan for the Williston Basin, in accordance with BLM planning policies. The assessment of the economic potential of lignite resources required the establishment of criteria defining an economic lignite deposit. In consultation with the BLM, criteria were established to delineate drill holes that contained economic lignite beds. The criteria established are a minimum lignite bed thickness, a minimum cumulative lignite thickness, a maximum cumulative stripping ratio, and a maximum overburden. Likewise, an assessment of the economic potential of leonardite deposits required the establishment of criteria delineating drill holes that contained economic leonardite deposits. The criteria established are a minimum leonardite bed thickness, a minimum cumulative leonardite thickness, and a maximum overburden. The drill hole data utilized in this study were obtained from the National Coal Resources Data System database and from several coal companies. Data from more than 20,000 drill holes, both proprietary and nonproprietary, were used to compile areas of economic potential for lignite or leonardite. Areas delineated as having lignite or leonardite resources with economic potential, based on the established criteria, were present in 24 counties in the western portion of North Dakota. Areas of economic potential were delineated using a visual best-fit method without croplines. Areas defined as having economic potential for certain lignite beds or leonardite deposits may extend beyond known croplines in this study. Stratigraphically, the lignite and leonardite deposits in the Williston Basin in North Dakota are mostly found in the Paleocene Fort Union Formation. Thick (greater than 20 feet) and laterally extensive (greater than 5 square miles) lignite beds are present in the Fort Union Formation throughout the Sentinel Butte and Tongue River Members. Lignite beds are also present in the Ludlow Member of the Fort Union Formation, although they are not as numerous or thick as they are in the overlying Sentinel Butte and Tongue River Members. As a result of lateral facies changes and migrating fluvial channel complexes in the Fort Union Formation, lignite beds of varying thickness occupy different stratigraphic horizons vertically throughout the Williston Basin. The calculation of volumes for lignite and leonardite resources was not part of the scope of this study requested by the BLM, but a future study by the USGS may involve a comprehensive assessment of lignite resources and reserves in the Williston Basin. This future study could combine geologic data compiled in this study with geologic data from a previously unpublished 2019 assessment study by the USGS in the Williston Basin in eastern Montana. This future USGS study could also include the calculation of volumes for lignite resources and reserves, based on economic models derived using analogs from active mining operations in the Williston Basin and available spot market or contract coal prices.

North Dakota↗
USGS1952

The Permian phosphorite deposits of western United States

The Permian marine phosphorite deposits of the western United States were laid down in the Phosphoria formation and its partial stratigraphic equivalents over an area of about 135,000 square miles in Montana, Idaho, Wyoming, Utah, and Nevada. The deposits in the eastern part of the field lie on the western margin of the structurally simple North American craton. The rocks there consist of a few thin, locally glauconitic, nodular phosphorites, generally containing less than 30 percent P 2 0 5 , interbedded with nodular limestones, calcareous mudstones, and sandstones. Eastward these marine beds tongue out into continental redbeds. The deposits in the western part of the field are a part of the complexly folded Cordilleran miogeosyncline. The facies there are of a deeper-water type and include thick phosphorite layers containing as much as 35 percent P 2 0 5 b lack phosphatic mudstones, limestones, and well-bedded black cherts. The phosphorite deposits are composed chiefly of colloform carbonate-fluorapatite, quartz, and clay. In addition to phosphorus, they contain several minor elements that are of potential economic interest. The most important of these are fluorine, vanadium, chromium, nickel, rare earths, zinc, and uranium.

Open-File Report↗
USGS1953

Geology of the Plumtree area, Spruce Pine district, North Carolina

This report describes the results of study and geologic mapping (1:12,000) in the 70-square-mile Plumtree area in the northeastern part of the Spruce Pine pegmatite district, on the Blue Ridge upland in western North Carolina. The district has been the chief domestic source of feldspar and sheet mica. The mining belt just west of the Blue Ridge Front trends northeast and is 25 miles long and 10 miles wide. The center of the Plumtree area lies 10 miles northeast of Spruce Pine pegmatite district, on the Blue Ridge upland in western North Carolina. The district has been the chief domestic source of feldspar and sheet mica. The mining belt just west of the Blue Ridge Front trends northeast and is 25 miles long and 10 miles wide. The center of the Plumtree area lies 10 miles northeast of Spruce Pine and includes parts of Mitchell and Avery Counties shown on the portions of the 7.5-minute Spruce Pine, Linville Falls, Newland, North Carolina, and Carvers Gap, North Carolina and Tennessee quadrangle. The topography varies from rugged mountains to rounded or flat topped hills near the entrenched, meandering master streams. Old erosion surfaces are approximately 600,1,100, 1,500, and 2,500 feet above the present master stream level. The area is in late youth or early maturity after rejuvenation.. The regionally metamorphosed rocks of the amophibolite facies form three mappable units: mica gneiss, mica schist, and hornblende rock. These rocks, perhaps of Precambrian age, are intimately interlayered with thicknesses of the individual layers ranging from less than one inch to several tons of feet. Field relationships and chemical data suggest that the mica (Carolina-type) rocks were derived from sandstones, graywackes, and shales and that the hornblende-rich (Roan-type) layers were derived from impure carbonate rocks. The igneous rocks include alaskite and associated pegmatite of early Paleozoic age (?), dunite and associated soapstone of a prepegmatite age, and a few diabasic dikes of post-pegmatite age (Triassic?). The alaskite and pegmatite have similar bulk compositions, notably low in iron (0.3 percent). The major constituents in order of decreasing abundance are plagioclase, perthitic microcline, quartz, and muncovite. All of these minerals, as well as clay deposits derived from the weathering of alaskite under old terraces, have economic value. The zoned pegmatites contain fewer zones which are less complex mineralogically than those in the pegmatites of many other areas. These essentially unmetamorphosed bodies were intruded approximately at the peak of the regional metamorphism. Their emplacement was controlled by local structure and rock type. The source of this igneous material may have been the mobilized portions of the Cranberry gneiss which underlies the area. The dunite bodies were intruded early in the metamorphic cycle. The bodies are commonly zoned: from the wall rock inwards (1) talc-antrophyllite-serpentine fringe, (3) serpentinized dunite, (3) granular olivine core. Dunite, chromite, vermiculite, and anthophyllite are the major economic commodities. Extensive hydrothermal alteration of dunite bodies produced soapstone. The area is the northeast end of a southwest plunging synclinorium about 20 miles wide with the steeper limb on the northwest side. There are three structural zones: zone I on the northwest is characterized by the northeast-trending isoclinal folds with steep southeast dips; zone II on the southwest includes an area of rocks with low and variable dip; zone III is the complex central core. In the extreme northeast zones I and II have an indistinct boundary where they coalesce along the rim of the synclinorium. Six stratigraphic units are exposed totaling approximately 10,500 feet of metamorphic rocks. Small scale structural features include a foliation, and a lineation in the planes of the foliation. Minor folding reflects the trends of the major structures. There are randomly orient

Open-File Report↗
USGS1959

Steatitization of serpentinite bodies in north-central Vermont

The talc deposits of north-central Vermont are associated with bodies of ultramafic rock, chiefly serpentinite, that are enclosed by metamorphosed sedimentary and volcanic rocks of Cambrian and Ordovician age; these stratified rocks form an essentially homoclinal succession in the east limb of the Green Mountain anticlinorium. The rocks at the localities described here are in the greenschist facies, and show only slight variations in grade of metamorphism between localities. The talc deposits consist typically of a core of serpentinite surrounded by successive shells of talc-carbonate rock and of steatite, next to which the country rock is altered for several inches to chlorite rock (blackwall). The steatite zone is rather uniformly about 3 feet thick, but the talc-carbonate rock and serpentinite zones vary considerably in thickness and are locally very irregular.

Vermont↗
USGS1968

The Mt. Montro kyanite deposit, Grand Bassa County, Liberia

The Mt. Montro kyanite deposit, 14 miles north of Buchanan, Grand Bassa County, Liberia, is near the middle of a belt of kyanite-bearing gneisses and schists that is 9 miles long and 1 mile wide. The deposit, which seems to be the most persistent and the largest single body of kyanite rocks in the belt, is approximately 12, 600 feet long, as much as 480 feet in outcrop width, and from 25 to 350 feet thick. Kyanite-quartz-biotite-feldspar-garnet-muscovite gneiss, local interbeds of kyanite-mica schist, and lesser amounts of biotite-quartz gneiss, are the principal rocks in the deposit. Other rocks in the kyanite belt include garnet-biotite gneiss, undifferentiated quartzo-feldspathic gneiss, quartzite, and amphibolite. The rocks are the product of regional metamorphism to almandine amphibolite facies. The regional strike is northwest and dips are southwest. Kyanite crystals are as much as 3 inches long. The kyanite content ranges from 5. 8 to 46. 7 percent, but most rocks contain between 10 and 35 percent. Garnetiferous beds contain as much as 15 percent red garnets that range to half an inch in diameter. In general, the garnet-rich beds are found in the upper part of the deposit. he total reserves of the Mt. Montro kyanite deposit are estimated at about 10 million tons of kyanitic rock containing approximately 2.5 million tons of kyanite. These estimates include measured, indicated, and inferred reserves, calculated to depths of 25 to 100 feet, on the assumption that open-cut mining to those depths would be feasible. The largest part of the deposit underlies Mt. Montro and contains about 8 million tons of kyanitic rock containing nearly 1.9 million tons of kyanite. Residual soil overlying the deposit averages about 5 feet in thickness and is estimated to comprise slightly more than 400,000 cubic yards of material containing about 186,000 tons of kyanite. The proximity of the kyanite deposit to a paved highway, to port facilities at Buchanan, and to water, electrical power, and timber resources are considered favorable factors relevant to possible development.

Grand Bassa County↗
USGS1969

Recent surface movements in the Baldwin Hills, Los Angeles County, California

The Baldwin Hills are located in the northwest part of the densely populated Los Angeles basin. They comprise one of several groups of isolated hills that extend along the northwest-trending Newport-Inglewood zone of folds and faults, a structural lineament identified with a series of very productive oil fields. In addition to being the site of the Inglewood oil field, these hills are the site of surface deformation that has been monitored for over 35 years. This record of deformation, which includes differential subsidence, horizontal displacements, and surface rupturing, forms one of the best documented examples of oilfield-associated surface deformation yet recognized. The deformation is described in detail, analyzed as to cause(s), and finally attributed largely or essentially entirely to the exploitation of the spatially-associated Inglewood oil field. The Baldwin Hills are underlain by gently to moderately arched and conspicuously faulted Cenozoic sedimentary and volcanic rocks that overlie crystalline basement rocks at a depth of more than 10,000 feet. The Inglewood fault, a part of the northwest-trending Newport-Inglewood zone, diagonally transects the hills. Right-lateral displacements of 3,000-4,000 feet since middle or late Pliocene time and 1,500-2,000 feet during Quaternary time are indicated by offset structural and physio-graphic features; indications of vertical separations of up to about 200 feet during late Quaternary time occur locally. Evidence of continuing deformation includes recognized seismicity and regional elevation changes. The M5-5 1/2 Inglewood earthquake of 1920, the largest local earthquake of record, is believed to have originated immediately southeast of the Baldwin Hills; it was apparently unassociated with surficial fault displacements. Leveling in and around the west and central Los Angeles basin has shown that lowland stations have been consistently subsiding, whereas foothill stations commonly have been rising. Several seemingly persistent basins of differential subsidence and a zone of positive movement, roughly coincident with the Newport-Inglewood zone, have also been identified in the northwest part of the basin. A prominent, elliptically-shaped, northwest-trending subsidence bowl encompassing the northwest part of the Baldwin Hills, has been defined by repeated level circuits. Partial reconstruction of selected level circuits with respect to a common, relatively stable control point (Hollywood E-11), located on the edge of the subsidence bowl, has permitted evaluation of the subsidence since 1910 and 1911 at two points near the center of the bowl. Thus bench mark PBM 67 is estimated to have subsided approximately 4.324 feet between June 1910 and February 1963; and bench mark PBM 68 (the only bench mark within the subsidence bowl that was leveled prior to 1926 and has been repeatedly leveled since) subsided 3.846 feet between November 1911 and June 1962. Analysis of the available data indicates little if any elevation change at PBM 68 (or elsewhere throughout the Baldwin Hills-Inglewood area) associated with the Inglewood earthquake of 1920. Maximum subsidence of PBM 122 (which has remained very close to the center of subsidence since at . least 1950) between 1911 and 1963 is calculated to have been 5.67 feet. Horizontal displacements (with respect to a north-south base line about 3 miles east of the hills) of six triangulation points within the subsidence bowl have been measured for various periods between 1934 and 1963. Displacements have been generally toward the center of subsidence and almost precisely perpendicular to the immediately adjacent isobases of equal elevation change. Maximum movement has been recorded at triangulation point Baldwin Aux, which was displaced 2.21 feet between 1934 and 1961; horizontal displacements of three additional points ranged from 0.95 foot to 1.85 feet between 1936 and 1961. Displacements of 0.10-0.29 foot were recorded at all six monuments during the period 1961-1963. "Earth cracks" and surficial fault displacements were recognized in the Baldwin Hills at least as early as 1957. The cracks are relatively straight, generally continuous fractures confined to the structural block east of the Inglewood fault; they are concentrated in two areas centering on (1) the Baldwin Hills Reservoir and (2) the Stocker Street-LaBrea Avenue-Overhill Drive intersection. The cracks trend north to north-northeast and are nearly everywhere parallel to or coincident with minor faults and joints, and are generally orthogonal to radii emanating from the center of subsidence. Differential movement along the cracks has been almost entirely dip slip along steep to nearly vertical surfaces, and generally down-dropped toward the center of subsidence. Cumulative displacements have been as much as 6 or 7 inches. Rates of displacement have ranged widely, and the movement has generally occurred as creep or very small discrete jumps. A probable exception is the several inches of differential movement that is believed to have occurred along a crack through the floor of the Baldwin Hills Reservoir on or about December 14, 1963. The contemporary surface movements are attributable to one or more of the following phenomena: (1). exploitation of the Inglewood oil field; (2) changes in the ground-water regimen; (3) compaction of sedimentary materials in response to surface loading; (4) tectonic activity. The following considerations indicate that the differential subsidence is attributable largely or entirely to exploitation of the underlying Inglewood oil field: (1) the coincidence of the centers of the oil field, the producing structure, and the subsidence bowl; (2) the general correspondence between the pattern of subsidence and the outlines of the oil field; (3) the approximate coincidence between the initiation of production and the initiation of subsidence; (4) the generally linear relations between various measures of subsidence and liquid production from both the field as a whole and the exceptionally prolific Vickers zone in particular; (5) the sharp deceleration of subsidence in the eastern block of the field coincident with the initiation of full-scale water flooding there; (6) the many examples of oil fields In which both spatial and temporal associations between production and subsidence are recognized; (7) the many similarities of the subsidence-production relations in the Inglewood field to those in the Wilmington field, where the subsidence has been authoritatively attributed to oilfield operations; (8) the theoretical relation between subsidence or a tendency toward subsidence and increased effective pressure associated with underground fluid extraction. Consideration of six possible explanations for the increasing rather than decreasing or constant rate of subsidence with respect to reservoir fluid pressure decline suggests that measured or calculated down-hole reservoir fluid pressure decline is non-representative of average or real fluid pressure decline away from producing wells. The near-linear relations between net-liquid production and subsidence are explained through analogy with a tightly confined artesian system of infinite areal extent, where production must derive from liquid expansion and/or reservoir compaction. Test data from compaction studies in two other oil fields yield estimates of ultimate compaction of the Vickers zone resulting from a total loss of fluid pressure; these estimates range over an order of magnitude. The best estimate, based on these data and considerations of late Cenozoic history in the Baldwin Hills area, is about 10 feet. The centripetally-directed horizontal movements are considered attributable to exploitation of the Inglewood oil field on the basis of: (1) their well-defined symmetrical and geometrical association with the differential subsidence; (2) the similarities between these associations and those developed in and around other subsiding oil fields; and (3) the mechanical compatibility of these movements with subsidence induced by the extraction of subsurface materials. The earth cracks and surficial fault displacements are considered largely or entirely attributable to the exploitation of the Inglewood oil field on the basis of: (1) their spatial and temporal relations to both oil-field operations and the differential subsidence; (2) the similarities of these cracks and displacements to those generated in and around other oil fields and areas of subsurface materials extraction; and (3) surface strain patterns predicted from the measured vertical and horizontal surface movements. The cracks and displacements can i)e explained by an exploitation-based, elastic-rebound model which requires elastic compression of the sedimentary section in response to compaction-induced downdrag within those blocks around the periphery of the subsidence bowl. The measured displacements have been about one-quarter to one-half those predicted for a purely elastic system. Analysis of: (1) the history of ground-water extraction within and around the Baldwin Hills; and (2) subsidence associated with water-level declines in sediments comparable with those in the Baldwin Hills, indicate that the surface movements can be no more than incidentally attributed to changes in ground-water conditions. Similarly, analysis of the history of natural and artificial changes in surface loading indicate that these movements are generally unassociated with changes in surface loading conditions. Considerations of local geologic history and various tectonic associations indicate that it is very unlikely that the differential subsidence and horizontal movements are due to tectonic downwarping. There exists a far stronger prima facie argument for tectonic involvement in the earth cracking and associated fault displacements. This argument is disputed by; (1) the spatial and temporal relations of the earth cracks to, and their mechanical compatibility with, the nontectonic differential subsidence; (2) the absence of displacements on the Inglewood fault in conjunction with those along the conjugate earth cracks; (3) the probability that purely tectonic displaceMents would be characterized by oblique or strike slip; and (4) the absence of any clear temporal relation between crack growth and local seismicity, However, because as much as 10 percent of the local isobase gradient may be unexplained' by oil-field exploitation, a small fraction of this gradient, and thus the displacements among the southern group of cracks, may be attributable to tectonic activity. This fraction should have been insignificant in the presence of the strain pattern produced by nontectonic compaction of the underlying oil measures. Because nearly all of the observed and measured surface movements can be fully explained as the products of oil-field operations, yet can be no more than incidentally attributed to changes in ground-water conditions, surface loading, or tectonic activity, we conclude that these movements are attributable largely or essentially entirely to the exploitation of the Inglewood oil field.

California↗
USGS1969

Report on exploration of the Wadi Yiba copper prospect, Tihamat Ash Sham quadrangle, Kingdom of Saudi Arabia

The first phase of an exploration program at The Wadi Yiba copper prospect consisted of geologic mapping, prospecting, sampling, geophysical surveys, and diamond drilling. Copper mineralization is in a sedimentary rock sequence comprised mostly of siliceous, calcareous, and dolomitic rocks metamorphosed to the greenschist facies. The metasedimentary rocks are overlain and underlain by metavolcanic rocks. They are folded into a tight north-plunging syncline transected by two fault systems. Results from the exploration program indicate that a fault zone which sub-parallels the synclinal axis and cuts siliceous dolomite contains copper mineralization and small amounts of gold and silver. Copper and silver beaming pyroclastic rocks were found in the upper part of the metasedimentary rock sequence. Concentrations of copper mineralization seem to be restricted to particular rock units in the metasedimentary rock sequence. Primary sulfides have not been encountered in the drill holes to date and the results from one drill hole indicate secondary copper sulfide minerals to a vertical depth of 60 meters. Further exploration seems to be warranted and a program is proposed which includes the investigation of other mineral occurrences and geophysical anomalies in the region.

Open-File Report↗
USGS1971

The drainage and glacial history of the Still River Valley, southwestern Connecticut

The Still River is located in southwestern Connecticut. From its origin on the New York border, it passes through Danbury and flows northward to its junction with the Housatonic River in New Milford. Interpretation of the Still River's history is based on its surficial geology and bedrock topography. High bedrock surfaces to the south, east, and west of the river show that its preglacial direction was probably to the north. The Still River has developed along the easily eroded Inwood Marble as a subsequent tributary to the Housatonic. Pleistocene glaciation left a variety of deposits in the Still Valley. The oldest of these is the 'lower' till, of either Illinoian or Altonian age. This till unit is overlain in turn by the Woodfordian 'upper' till. The upper till has basal and ablation facies. Ice-contact deposits formed in the fringing stagnation zone of the last retreating ice sheet. As the glacier withdrew along the Still Valley, preglacial Lake Danbury was impounded against the highlands to the south. Glacial retreat opened progressively lower outlets for this lake. Its final stage was contained by a till (?) barrier at the Housatonic Gorge in New Milford. Filling of the lake by glacial outwash was soon followed by downcutting of the dam and establishment of the modern Housatonic and Still River channels.

Open-File Report↗
USGS1971

The Shublik Formation and adjacent strata in northeastern Alaska description, minor elements, depositional environments and diagenesis

The Shublik Formation (Middle and Late Triassic) is widespread in the surface and subsurface of northern Alaska. Four stratigraphic sections along about 70 miles of the front of the northeastern Brooks Range east of the Canning giver were examined and sampled in detail in 1968. These sections and six-step spectrographic and carbon analyses of the samples combined with other data to provide a preliminary local description of the highly organic unit and of the paleoenvironments. Thicknesses measured between the overlying Kingak Shale of Jurassic age and the underlying Sadlerochit Formation of Permian and Triassic age range from 400 to more than 800 feet but the 400 feet, obtained from the most completely exposed section, may be closer to the real thickness across the region. The sections consist of organic-rich, phosphatic, and fossiliferous muddy, silty, or carbonate rocks. The general sequence consists, from the bottom up, of a lower unit of phosphatic siltstone, a middle unit of phosphatic carbonate rocks, and an upper unit of shale and carbonate rocks near the Canning River and shale, carbonate rocks, and sandstone to the east. Although previously designated a basal member of the Kingak Shale (Jurassic), the upper unit is here included with the Shublik on the basis of its regional lithologic relation. The minor element compositions of the samples of the Shublik Formation are consistent with their carbonaceous and phosphatic natures in that relatively large amounts of copper, molybdenum, nickel, vanadium and rare earths are present. The predominantly sandy rocks of the underlying Sadlerochit Formation (Permian and Triassic) have low contents of most minor elements. The compositions of samples of Kingak Shale have a wide range not readily explicable by the nature of the rock: an efflorescent sulfate salt contains 1,500 ppm nickel and 1,500 ppm zinc and large amounts of other metals derived from weathering of pyrite and leaching of local shale. The only recorded occurrence of silver and 300 ppm lead in gouge along a shear plane may be the result of metals introduced from an extraneous source. The deposits reflect a marine environment that deepened somewhat following deposition of the Sadlerochit Formation and then shoaled during deposition of the upper limestone-siltstone unit. This apparently resulted from a moderate transgression and regression of the sea with respect to a northwest-trending line between Barrow and the Brooks Range at the International Boundary. Nearer shore facies appear eastward. The phosphate in nodules, fossil molds and oolites, appears to have formed diagenetically within the uncompacted sediment.

Open-File Report↗
USGS1973

Geohydrology and artificial-recharge potential of the Irvine area, Orange County, California

The Irvine area is in hydraulic continuity with the rest of the coastal plain in Orange County. Factors that distinguish the aquifer section of the Irvine area from that in other parts of the coastal plain are a low permeability, a high clay and silt content, and a thin alluvial sequence. Rapid facies change and the large percentage of silt and clay in the section locally result in confining conditions. The aquifer, most of which is included in the Fernando Formation, is as much as 1,300 feet thick beneath parts of the plain. The alluvium overlying the Fernando Formation averages about 200-250 feet in thickness and also contains significant amounts of silt and clay. Transmissivities range from 25,000 to 100,000 gallons per day per foot in the Irvine area, values which are much lower than those in the rest of the coastal plain in Orange County. Water levels have recovered as much as 60 feet from the low levels of the early 1950's. Water-level maps indicate that in the winter non-pumping season water tends to move toward upper Newport Bay and the rest of the coastal plain. During the summer pumping season a cone of depression develops, reversing the winter gradient. The average dissolved-solids content of the ground water is about 800 milligrams per liter. The most prevalent cations are sodium and calcium; the most prevalent anions are bicarbonate and sulfate. No long-term degradation of water quality has occurred, with the exception of a slight increase in dissolved solids. No areas in the Irvine area are suitable for the large-scale spreading of water for artificial recharge. Clay and silt predominate in the section beneath the Tustin plain, and in the foothill areas either bedrock is close to the surface or the alluvium is fine grained.

Open-File Report↗
USGS1973

Trioctahedral smectite in the Green River Formation, Duchesne County, Utah

Abundant trioctahedral smectite and smaller amounts of illite comprise a simple assemblage of clay minerals in a basin-edge sequence of lacustrine claystones and oil shales in the Eocene Green River Formation, southwest Uinta Basin, Duchesne County, Utah. Chlorite and mixed-layer clay are present in a few samples. The smectite is well crystallized and has a high expansible-layer content; its chemical composition is uncertain for lack of pure material, but available data suggest a Mg- and Fe-bearing species in the compositional range between saponite and lembergite. Although no significant differences were noted in the clay-mineral content of the claystones versus the oil shales, it was found that calcite strongly prefers oil shale whereas dolomite strongly favors claystone, suggesting that interstitial waters of the claystones during deposition and lithification were more saline than those of the oil shales. The trioctahedral smectite may be part of a basin edge-to-center series of clay-mineral facies--kaolinite to smectite to mica (illite).

Utah↗
USGS1973

Geology and mineral deposits of an area in the Departments of Antioquia and Caldas (Subzone IIB), Colombia

The Inventario Minero National (IMN), a four-year cooperative geologic mapping and mineral resources appraisal project, was accomplished under an agreement between the Republic of Colombia and the U. S. Agency for International Development from 1964 through 1969. Subzone IIB, consisting essentially of the east half of Zone comprises nearly 20,000 km2 principally in the Department of Antioquia but including also small parts of the Departments of Caldas and Tolima. The rocks in IIB range from Precambrian to Holocene. Precambrian feldspar-quartz gneiss occupies a mosaic of fault-bounded blocks intruded by igneous rocks between the Oto fault and the Rio Magdalena. Paleozoic rocks are extensive, and include lightly metamorphosed graptolite-bearing Ordovician shale at Cristalina, and a major suite of graphitic quartz-mica schist, feldspathic and aluminous gneiss, quartzite, marble, amphibolite, and other rocks. Syntectonic intrusive gneiss included many of the older rocks during a late Paleozoic(?) orogeny, which was accompanied by Abukuma-type metamorphosing from lowermost greenschist to upper amphibolite facies. A Jurassic diorite pluton bounded by faults cuts volcanic rocks of unknown age east of the Otu fault. Cretaceous rocks are major units. Middle Cretaceous carbonaceous shale, sandstone, graywacke, conglomerate, and volcanic rocks are locally prominent. The Antioquian batholith (quartz diorite) of Late Cretaceous age cuts the middle Cretaceous and older rocks. A belt of Tertiary nonmarine clastic sedimentary rocks crops out along the Magdalena Valley. Patches of Tertiary alluvium are locally preserved in the mountains. Quaternary alluvium, much of it auriferous, is widespread in modern stream valleys. Structurally IIB constitutes part of a vast complex synclinorium intruded concordantly by syntectonic catazonal or mesozonal felsic plutons, and by the later epizonal post-tectonic Antioquian batholith. Previously unrecognized major wrench faults are outstanding structural features of IIB. Some are traceable for several hundred kilometers and probably have displacements measurable in kilometers, although only the Palestina fault, with right-lateral displacement of 27.7 km, is accurately documented. Correlations of rocks mapped in IIB with those of outlying areas including neighboring IIA are discussed.

Open-File Report↗
USGS1973

Geology and mineral resources of central Antioquia Department (Zone IIA), Colombia

This report summarizes the geology of an area of some 6000 square kilometers in the northern part of the Central Cordillera of the Colombian Andes. The area, in north-central Department of Antioquia, was mapped between 1964 and 1968 as part of the Inventario Minero Nacional (IMN) project. Mineral resources are summarized within a larger area, designated as subzone ILK of IMN Zone If, which comprises almost 22,000 sq. kin, including the area mapped geologically by IMN and additional areas mapped by other agencies. The oldest formation is a micaceous paragneiss of early Paleozoic or possibly late Precambrian age. A thick geosynclinal sedimentary series accumulated during the Paleozoic Era and became regionally metamorphosed to greenschist (locally amphibolite) facies during the Permian or early Triassic; these schists and gneisses are designated collectively as the Valdivia Group. The Permian(?) orogenic episode included intrusion of concordant syntectonic plutons, mostly of tonalitic composition. Rocks of unequivocal Triassic or Jurassic age are not recognized. The Cretaceous is well represented by both igneous and sedimentary assemblages. Eugeosynclinal alpine ophiolites comprising submarine basalt flows and numerous intrusions of gabbro and serpentinite are prominent in the Lower Cretaceous, together with flysch composed of marine shale and lesser sandstone and conglomerate. The Upper Cretaceous is represented along the west border of the mapped area by submarine basalt flows and pyroclastic rocks, locally Interbedded with fine-grained clastic sedimentary beds, and lenses of dark laminated chert, at least part of which is radiolarian. The Late Cretaceous was marked by an orogenic event that profoundly folded and faulted all rocks and in the Central Cordillera caused low-grade metamorphism, the overprint of which is hardly observable in pre-Cretaceous rocks elsewhere. The Late Cretaceous orogeny culminated with discordant intrusion of the epizonal tonalitic Antioquian batholith. Displacement along the great Romeral wrench fault may have begun in the Cretaceous. Plutonism continued into the Cenozoic, exemplified by the hornblende-diorite Sabanalarga pluton. Intermontane basins were filled with molasse derived from the erosion of adjacent highlands; Tertiary sedimentation in marshy areas included organic carboniferous matter subsequently converted to lignite or subbituminous coal. The Sabanalarga fault system originated in the Late Tertiary; intermittent displacement continued on the older wrench faults such as the Romeral. Epeirogenic uplift, which probably began in the Pliocene and continued through the Pleistocene and Holocene, brought on renewed erosion which has sculptured the mountains into their present form. Mineral resources in subzone IIA are varied but not of outstanding importance. Gold and silver mining, significant in past centuries, is minor today. Ferruginous laterite on serpentinite once considered as a potential source of iron ore is not economically exploitable. IMN has explored nickeliferous laterite at the extreme northwest corner of subzone IIA; this is a potential resource, exploitable only after exhaustion of the larger and richer nickel laterite deposit at Cerro Matoso, farther to the north and outside the boundaries of Zone If. Known deposits of mercury, chromium, manganese, and copper are small, with limited economic potential. Nonmetallic resources include raw materials for cement, including portland cement. Saprolite clay is widely used in making common red brick and tile, still a dominant construction material in all but the most modern multistory buildings. Aggregate materials are varied and abundant. Kaolin of good quality near La Union is important as a ceramic raw mineral filler. Tertiary subbituminous coal beds are an important energy resource in western subzone IIA, and have a good potential for greater development. Deposits of sodic feldspar, talc, decorative stone, and silica a

Open-File Report↗
USGS1975

Reconnaissance engineering geology of the Ketchikan area, Alaska, with emphasis on evaluation of earthquake and other geologic hazards

The Alaska earthquake of March 27, 1964, dramatically emphasized the need for engineering geologic studies of urban areas in seismically active regions. A reconnaissance study of the Ketchikan area in southeastern Alaska is part of a program to evaluate earthquake and other geologic hazards in most of the larger Alaska coastal communities. These evaluations in the Ketchikan area should provide broad guidelines useful in city and land-use planning. Ketchikan, which had a population of approximately 7,000 in 1970, is built on the southwestern end of Revillagigedo Island along the northeastern coastline of Tongass Narrows. Altitudes reach 1,000 feet (305 m) within half a mile (0.8 km) of the coast and near-vertical cliffs characterize the terrain in places. The climate is predominantly marine. Average precipitation is approximately 152 inches (386 cm). The Ketchikan area was covered by glacier ice at least once and probably several times during the Pleistocene Epoch. The present topography, characterized by elongate lakes, U-shaped valleys, fiords, inlets, and passages, clearly reflects the effects of glaciation. The presence of emergent marine deposits, at least 300 feet (91 m) above sea level, shows that the land has been uplifted relative to sea level since the last deglaciation of the region. Bedrock is exposed or is near the surface throughout most of the mapped area. The bedrock consists chiefly of metamorphic rocks. In a few places these rocks have been intruded by igneous rocks. Exposed metamorphic rocks are mostly thinly foliated schists and phyllites, metamorphosed to greenschist facies. Foliation generally strikes northwest with moderate to steep dips to the northeast. Most of the rock is fairly competent and near-vertical cuts tend to be stable. The more indurated metamorphic rock can be used for riprap, but more durable blocks generally can be obtained from the igneous rock. The surficial deposits have been divided into the following map units on the basis of their time of deposition, mode of origin, and grain size: (1) undifferentiated drift (Qd), (2) elevated marine deposits (Qm), (3) stream alluvium (Qa), (4) fan-delta deposits (Qf), and (5) modern beach deposits (Qb). Manmade fill (f) also is mapped as a separate unit. Muskeg, colluvium, and offshore deposits are not included as map units but are discussed in the report under the heading "Surficial deposits (not shown on map)." The undifferentiated drift deposits consist mostly of till or other diamictons, generally less than 25 feet (7.6 m) thick. Exposed elevated marine deposits (Qm) generally consist of sand and gravel less than 5 feet (1.5 m) thick. Stream alluvium (Qa) is chiefly sand, gravel, cobbles, and boulders probably everywhere less than 15 feet (4.6 m) thick. Fan-delta deposits (Qf) consist mostly of loose sand, gravel, and boulders as much as 50 feet (15 m) thick. Modern beach deposits (Qb) are mostly loose sand and gravel generally less than 10 feet (3 m) thick. Two basically different types of manmade fill are present: (1) large fills along the waterfront, commonly 5 to 15 feet (1.5-4.6 m) thick, consisting of silt, sand, gravel, rock, and diverse other materials, and (2) fills, generally less than 10 feet (3 m) thick and consisting of sand, gravel, or crushed rock, placed inland from the waterfront and used as pads for buildings and parking areas. Fairly thick deposits of muskeg may be present in the southeastern part of the mapped area but have not been examined in the field. Colluvial deposits, locally 5 to 8 feet (1.5-2.4 m) thick, consist mostly of decomposing bedrock fragments. Offshore deposits are poorly known; near-shore loose sand and gravel rest on a sloping bedrock surface. Southeastern Alaska lies within the circum-Pacific seismic belt that rims the northern Pacific Basin and has been tectonically active since at least early Paleozoic time. Large-scale faulting has been common. The two most prominent fault systems in southeastern Alaska and surrounding regions are (1) the Denali fault system, and (2) the Fairweather-Queen Charlotte Islands fault system. Of the two, the Fairweather-Queen Charlotte Islands fault system is the more active and of most significance in relation to the Ketchikan area. Ketchikan lies within the northwest trend of the Gravina-Nutzotin belt of fault thrusting. The trends of at least some of the linear fiords near the mapped area are controlled by faults. However, it is not known whether a major fault extends up Tongass Narrows offshore from Ketchikan. Between 1899 and 1970, five earthquakes having magnitudes of 8 or greater occurred in or near southeastern Alaska or in adjacent offshore areas; three have occurred having magnitudes of between 7 and 8, at least eight with magnitudes of between 6 and 7, 15 with magnitudes of between 5 and 6, and about 140 have been recorded with magnitudes of less than 5 or of unassigned magnitudes. All of the earthquakes with magnitudes greater than 8, and a large proportion of the others, appear to be related to the Fair-weather-Queen Charlotte Islands fault system or to the connecting Chugach-St. Elias fault to the northwest. Within a 50-mile (80-km) radius of Ketchikan, epicenters of three earthquakes with magnitudes of 5 or less have been recorded. Within a radius of 100 miles (160 km), 10 epicenters have been recorded, two with magnitudes between 6 and 7 and eight with magnitudes of 5 or less. Although no instrumentally recorded earthquakes had epicenters in the mapped area, at least 32 earthquakes that had epicenters elsewhere were felt or possibly felt in Ketchikan. Most of these earthquakes probably had epicenters along the Queen Charlotte Islands fault. Ketchikan is tentatively assigned by me to seismic zone 2. This is a zone in which magnitudes of the largest expectable earthquake would range from 4.5 to 6.0 and where moderate damage could be expected. Large earthquakes of magnitude 8 or greater, however, can be expected to occur from time to time along the Queen Charlotte Islands fault. Ground motion from these earthquakes, although attenuated with distance, may still be sufficiently strong at Ketchikan to cause substantial damage. Possible future earthquake effects include: (1) land-level changes caused by local faulting or by large-scale regional deformation, (2) ground shaking, (3) compaction, (4) liquefaction, (5) subaerial and submarine sliding, (6) water-sediment ejection and ground fracturing, (7) reaction of sensitive and quick clays, and (8) effects of tsunamis, seiches, and other abnormal water waves. Although land-level changes due to local faulting are unlikely, large-scale regional deformation may cause uplift or subsidence in Ketchikan. Adverse effects would be confined mainly to the waterfront area. This area also would be most heavily damaged if Ketchikan were strongly shaken by an earthquake. Nonengineered, loose, manmade fills and fan-delta deposits in this area probably would be subject to the strongest shaking. These deposits probably also are most subject to compaction, liquefaction, sliding, and water-sediment ejection. Earthquake effects expectably would be considerably fewer and less severe for the part of Ketchikan upslope from the harbor area because bedrock is at or near the surface in large parts of the area. No sensitive clays have been identified but, if present, they probably are confined to the till and other diamicton deposits in the northeastern part of the mapped area. Tsunami waves are not expected to have a local generation source. Those arriving from a distant source, although potentially highly destructive, probably would be greatly attenuated before arriving at Ketchikan. Seiche waves may develop on lakes near the mapped area and possibly cause failure of earth-fill dams. Destructive waves generated by earthquake-induced local submarine sliding appear to be unlikely in the Ketchikan area. Geologic hazards in the area that are not caused by earthquakes are believed to be relatively minor. They include: (1) landsliding and subaqueous sliding, and (2) flooding. Only minor landsliding has occurred in the mapped area, but the potential for sliding may increase as the city expands and heavily timbered areas are cleared, with attendant accelerated erosion and mass wasting. The greatest potential for subaqueous sliding is along the shoreline, where fairly thick fan-delta deposits rest on a sloping bedrock surface. Periodic flooding has occurred on some creeks in the mapped area and can be expected to occur from time to time in the future. In order that more accurate evaluations of geologic hazards can be made in the future, several recommendations are made for additional studies.

Alaska↗
USGS1975

Sediments, structural framework, petroleum potential, environmental conditions, and operational considerations of the United States South Atlantic Outer Continental Shelf

The area designated for possible oil and gas lease sale in Bureau of Land Management memorandum 3310 #43 (722) and referred to therein as part of the United States South Atlantic Outer Continental Shelf (OCS) contains about 98,000 square kilometres of the continental margin seaward of the 3 mile offshore limit and within the 600 metre isobath. The designated area, offshore of North Carolina, South Carolina, Georgia, and Florida, encompasses parts of three physiographic provinces: the Continental Shelf, the Florida-Hatteras Slope, and the Blake Plateau. The structural framework of the U.3. South Atlantic region is dominated by the Southeast Georgia Embayment --an east-plunging depression recessed into the Atlantic Coastal Plain and shelf between Cape Fear, North Carolina and Jacksonville, Florida. The embayment is bounded to the north by the Cape Fear Arch and to southeast by the Peninsular Arch. Refraction data indicate a minor basement(?) ridge beneath the outer shelf between 30° and 32°N at 80°W. Drill hole data also suggest a gentle fold or accretionary structure (reef?) off the east coast of Florida. Several other structural features have been identified by refraction and reflection techniques and drilling. These are the Yamacraw Uplift, Burton High, Stone Arch, and the Suwannee Channel. Gravity and magnetic anomalies within the area probably result from emplacement of magma bodies along linear features representing fundamental crustal boundaries. Of these anomalies, the most prominent, is a segment of the East Coast Magnetic Anomaly which crosses the coast at Brunswick, Georgia. This anomaly has been interpreted as representing an ancient continental boundary where two formerly separate continental plates collided and were welded together. There may be as much as 5,000 m of sedimentary rocks in the Southeast Georgia Embayment out to the 600 m isobath. Basement rocks beneath the Southeast Georgia Embayment are expected to be similar to those exposed in the Appalachian Piedmont province. Triassic deposits are likely to exist beneath the inner Continental Shelf, and probably consist of nonmarine arkosic sandstones, shales, basalt flows, and diabase intrusions deposited in relatively narrow northeast-trending grabens. Jurassic marine carbonates in the Bahamas grade northward to carbonates, shales, sand, and arkose in North Carolina. Salt may be present in the basal Jurassic section in the Southeast Georgia Embayment. Up to 4,000 m of Jurassic-Lower Cretaceous rocks are expected out to the 600 m water depth. Lower Cretaceous rocks in southern Florida are shallow-water marine limestone and dolomites with beds of anhydrite. In coastal North Carolina the Lower Cretaceous is a marine section made up of shales, sand, and sandy limestone. The Upper Cretaceous is composed almost entirely of marine carbonates in southern Florida grading northward to nonmarine to marginal marine, sandstones and shales with minor amounts of carbonates. In general, Upper Cretaceous rocks will probably maintain a fairly constant thickness (600 m) on the Continental Shelf and grade downdip from terrigeneous sands and shales to more marine chalks, limestones, and dolomites. The Cenozoic rocks are predominantly shallow-water marine carbonates in Florida grading northward into a marginal marine to marine clastic facies composed of sands, marls, and limestones. The offshore Cenozoic section is expected to range in thickness from 600 to 1100 m.

Florida, Georgia, South Carolina↗
USGS1976

Regional appraisal of the Wilcox Group in Texas for subsurface storage of fluid wastes: Part 1: Geology

Sandy beds of the Wilcox Group in Texas are underlain and overlain by clays of the Midway and Claiborne Groups. The Wilcox is divided by a persistent shale wedge. Contrasting delta systems described as high-constructive and high-destructive exist in the divisions. Merged high constructive deltas characterize the lower, while the upper Wilcox was deposited as a high destructive system. Maximum sand development occurs downdip parallel to regional depositional strike in the delta facies. Further downdip, shales replace sands, and sediments are (abnormally high pressured) geopressured. The structure o5 the updip port[on is that of a stable shelf. Downdip, greatly thickened beds are cut by large faults. These faults and the resultant deposits are recognized as being the result of a previously unnamed phenomenon--here termed hydrothermal tectonism. This process is keyed to the thermal diagenesis of the clay mineral montmorillonite and resultant transfer of overburden pressure from the rock framework to the contained fluid.

Texas↗
USGS1976

Geology of the Deep Creek area, Washington, and its regional significance

This report, although primarily concerned with the stratigraphy and structure of a lead-zinc mining district in northern Stevens County, Washington, discusses and integrates the geology of the region about the Deep Creek area. Although the study centers in an area of about 200 square miles immediately south of the International Boundary, the regional background comes from: (1)the previously undescribed Northport quadrangle to the west, (2) published reports and reconnaissance of the Metaline quadrangle to the east, and (3) from published reports and maps of a 16 mile wide area that lies to the north adjacent to these three quadrangles in British Columbia. The report is divided into three parts: (1) descriptions of rocks and structures of the Deep Creek area, (2) descriptions of the regional setting of the Deep Creek area, and (3) an analysis and interpretation of the depositional and tectonic events that produced the geologic features exposed today. In the Deep Creek area surficial deposits of sand and gravel of glacial origin cover much of the consolidated rocks, which range in age from greenschist of the late Precambrlan to albite granite of the Eocene. Three broad divisions of depositional history are represented: (1) Precambrian, (2) lower Paleozoic and (3) upper Paleozoic; the record of the Mesozoic and Eocene is fragmentary. The lower Paleozoic division is the only fossil-controlled sequence; the age of the other two divisions were established by less direct methods. Both Precambrian and upper Paleozoic sequences are dominated by fine-grained detrital sediments, the Precambrian tending towards the alumina-rich and the upper Paleozoic tending towards the black shale facies with high silica. Neither sequence has more than trivial amounts of coarse clastics. Both include limestones, but in minor abundance. The lower Paleozoic sequence, on the other hand, represents a progressive change in deposition. The sequence began during the very late Precambrian with the deposition of clean quartz sand. This was followed by the accumulation of a comparatively thin limestone unit succeeded by a thick shale. The shale grades into a thick carbonate unit which in turn is overlain by black graptolitic slates (Ordovician). This general order of deposition holds for the Cambro-Ordovician throughout the area. Precambrian rocks indigenous to the Deep Creek area, have undergone at least six tectonic events of greatly different intensities. The first three of these events are epeirogentic, the fourth involves intense folding, the fifth, crossfolding, and the sixth, block faulting without folding. These events are dated with varying degrees of precision. The two epeirogentic events of the Precambrian, one gentle folding at the beginning of Windermere time and the other high angle faulting and volcanism in mid-Windermere time, did little to deform or metamorphose the rocks. The third event consists of uplift of northern Idaho and adjacent Montana and westward decollement thrusting of essentially unfolded lower Paleozoic rocks. The decollement faulting is inferred to explain anomalous rock distribution and cannot be accurately dated. It occurred sometime after the Devonian and before the Jurassic. A late Paleozoic age is favored.

British Columbia, Idaho, Washington↗
USGS1977

The biostratigraphy and paleoecology of the Gerster limestone (Upper Permian) in Nevada and Utah

The Gerster Limestone contains three minor lithofacies: the packstone, wackestone, and mixed facies, differentiated largely on the basis of the carbonate matrix and mud content of the rocks. Five biostratigraphic zones ranging in age from Roadian-Wordian to Wordian are, in ascending order, the Thamnosia, Kuvelousia, transition, Yakovlevia, and upper zones. The Gerster was probably deposted in a protected coastal basin separated from the Phosphoria Basin by a shallow marine positive area. The brachiopod fauna is divided into fifteen bioassociations. The fauna is part of a continental margin suite of faunas distributed from west Texas to the Canadian Arctic and belongs to the Tethyan-nonreef biogeographica[ province.

Open-File Report↗