Resistivity structure to about 25 km depth is defined from two-dimensional modeling of 29 magnetotelluric (MT) soundings (0.002–5 Hz) that traverse 280 km of the southwestern Colorado Plateau, transition zone, and Basin and Range provinces in Arizona. From the surface to 5 km depth, the MT model suggests structural relationships between low-resistivity sedimentary and volcanic rocks (50–300 ohm m) and high-resistivity granitic and gneissic basement (500–9000 ohm m). In the Basin and Range province, the MT model and a seismic reflection section show a generally consistent distribution of supracrustal rocks that have relatively low to moderate resistivity (MT) and relatively strong, locally coherent reflectivity. The supracrustal zone defined by these physical properties is inferred to be composed of upper plate rocks above a middle Tertiary detachment fault system which has been mapped in surrounding ranges. Some low-angle fault zones inferred from seismic reflections to extend into high resistivity basement below the supracrustal rocks are not resolved by the MT model. A low-resistivity zone with a conductance of 500 S or more is modeled in the crust at an average depth of about 15 km in the Basin and Range province and transition zone and may deepen below the southwestern part of the Colorado Plateau. In the Basin and Range province, the top of the low resistivity may correspond to a reflective layer with a 6-s two-way-travel time. This deep low-resistivity zone might be caused by a small fraction of connected hydrous solutions or silicic melts.
Suspended-sediment loads are often estimated from an empirical relation between suspended-sediment load (L) and streamflow (S). This relation is usually defined as a power function, L = aSh, and is referred to as a suspended-sediment rating curve. This function can be formulated as either a linear or non-linear model to find the solution of the rating-curve parameters (a and b). Formulation of the power function as a linear model requires a logarithmic transformation to linearize the function and a subsequent correction for transformation bias. Rating-curve parameter estimates for both the bias-corrected, transformed-linear or non-linear models can be obtained by the method of least squares.
\nEach model has distinct advantages and disadvantages. A unique solution of the parameters of the transformed-linear model may be obtained algebraically. These parameter estimates have some optimal properties when certain attainable conditions are met. However, the parameter estimates must be corrected for transformation bias when obtained this way. Parameter estimates obtained for the non-linear model do not require a correction for transformation bias. However, these estimates must be obtained by iterative methods which do not always converge to a solution. In addition, the residual errors of the non-linear model typically are not identically distributed throughout the range of streamflow values. This problem adversely affects the precision of the parameter estimates. Weighted non-linear least squares can be used to improve the parameter estimates for the non-linear model, but the weights must be approximated and their appropriate form may be difficult to determine.
\nA simulation study was done to evaluate: (1) the accuracy and precision of parameter estimates for the bias-corrected, transformed-linear and non-linear models obtained by the method of least squares; (2) the accuracy of mean suspended-sediment loads calculated by the flow-duration, rating-curve method using model parameters obtained by the alternative methods. Parameter estimates obtained by least squares for the bias-corrected, transformed-linear model were considerably more precise than those obtained for the non-linear or weighted non-linear model. The accuracy of parameter estimates obtained for the biascorrected, transformed-linear and weighted non-linear model was similar and was much greater than the accuracy obtained by non-linear least squares. The improved parameter estimates obtained by the biascorrected, transformed-linear or weighted non-linear model yield estimates of mean suspended-sediment load calculated by the flow-duration, rating-curve method that are more accurate and precise than those obtained for the non-linear model.
","language":"English","publisher":"Elsevier","doi":"10.1016/0022-1694(91)90057-O","issn":"00221694","usgsCitation":"Crawford, C.G., 1991, Estimation of suspended-sediment rating curves and mean suspended-sediment loads: Journal of Hydrology, v. 129, no. 1-4, p. 331-348, https://doi.org/10.1016/0022-1694(91)90057-O.","productDescription":"18 p.","startPage":"331","endPage":"348","onlineOnly":"N","additionalOnlineFiles":"N","costCenters":[{"id":346,"text":"Indiana Water Science Center","active":true,"usgs":true}],"links":[{"id":223633,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"129","issue":"1-4","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a0bb2e4b0c8380cd5282e","contributors":{"authors":[{"text":"Crawford, Charles G. 0000-0003-1653-7841 cgcrawfo@usgs.gov","orcid":"https://orcid.org/0000-0003-1653-7841","contributorId":1064,"corporation":false,"usgs":true,"family":"Crawford","given":"Charles","email":"cgcrawfo@usgs.gov","middleInitial":"G.","affiliations":[{"id":451,"text":"National Water Quality Assessment Program","active":true,"usgs":true},{"id":37947,"text":"Upper Midwest Water Science Center","active":true,"usgs":true}],"preferred":true,"id":369872,"contributorType":{"id":1,"text":"Authors"},"rank":1}]}} ,{"id":2000057,"text":"2000057 - 1991 - Walleye in Lake Erie and Lake St. Clair","interactions":[],"lastModifiedDate":"2012-02-02T00:14:56","indexId":"2000057","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":18,"text":"Report"},"publicationSubtype":{"id":3,"text":"Organization Series"},"seriesTitle":{"id":217,"text":"Special Publication","active":false,"publicationSubtype":{"id":3}},"seriesNumber":"91-1","title":"Walleye in Lake Erie and Lake St. Clair","docAbstract":"The history and current status of walleye (Stizostedion vitreum vitreum) stocks in Lake Erie and Lake St. Clair are reviewed in relation to their exploitation by commercial and recreational fishermen, environmental factors, rehabilitation efforts, and community dynamics. Management initiatives and stock recovery under these processes are outlined.\rAfter the collapse of the fishery in 1957, the highly productive walleye stock of western Lake Erie remained depressed through the 1960s, while the eastern basin stock remained stable. Closure of the fishery for walleye from 1970-73 because of mercury contamination provided an opportunity for the development of an international interagency management plan. With quota management, the walleye stock in western Lake Erie responded well to limited exploitation, steadily increased, and expanded its range. As population expanded, growth began to decline and was more apparent in the young-of-the-year (YOY) in the 1970s, and in older walleye in the late 1970s and 1980s.\rAt the turn of the century, commercial harvest of walleye in Lake St. Clair ranged from 12-127 tonnes annually. A relatively stable period from 1910-59 was followed by significantly increased harvests (100-150 t) in 1959-65. This increase was a result of increased commercial exploitation as well as an increased abundance of walleye. After the mercury contamination problem of 1970, angling effort and harvest was reduced but then gradually increased in Ontario waters from 37 t in 1973 to 62 t in 1988. The increased mean age of the stock during the early 1970s was due to a few strong year-classes (1970, 1972, and 1974) as well as a period of stable or reduced catch per unit effort. With the current mean age not reduced significantly, the stocks of walleye should continue to provide good yields.","largerWorkType":{"id":18,"text":"Report"},"largerWorkTitle":"Status of walleye in the Great Lakes: case studies prepared for the 1989 workshop","largerWorkSubtype":{"id":3,"text":"Organization Series"},"language":"English","publisher":"Great Lakes Fishery Commission","publisherLocation":"Ann Arbor, MI","usgsCitation":"Nepszy, S., Davies, D., Einhouse, D., Hatch, R., Isbell, G., MacLennan, D., and Muth, K., 1991, Walleye in Lake Erie and Lake St. Clair: Special Publication 91-1, p. 145-168.","productDescription":"p. 145-168","startPage":"145","endPage":"168","numberOfPages":"24","costCenters":[{"id":324,"text":"Great Lakes Science Center","active":true,"usgs":true}],"links":[{"id":198949,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"4f4e4a0ae4b07f02db5fb814","contributors":{"authors":[{"text":"Nepszy, S.J.","contributorId":96802,"corporation":false,"usgs":true,"family":"Nepszy","given":"S.J.","affiliations":[],"preferred":false,"id":325010,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Davies, D.H.","contributorId":102976,"corporation":false,"usgs":true,"family":"Davies","given":"D.H.","email":"","affiliations":[],"preferred":false,"id":325012,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Einhouse, D.","contributorId":61125,"corporation":false,"usgs":true,"family":"Einhouse","given":"D.","affiliations":[],"preferred":false,"id":325008,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Hatch, R.W.","contributorId":68008,"corporation":false,"usgs":true,"family":"Hatch","given":"R.W.","email":"","affiliations":[],"preferred":false,"id":325009,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Isbell, G.","contributorId":18477,"corporation":false,"usgs":true,"family":"Isbell","given":"G.","email":"","affiliations":[],"preferred":false,"id":325007,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"MacLennan, D.","contributorId":98012,"corporation":false,"usgs":true,"family":"MacLennan","given":"D.","email":"","affiliations":[],"preferred":false,"id":325011,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Muth, K.M.","contributorId":6968,"corporation":false,"usgs":true,"family":"Muth","given":"K.M.","email":"","affiliations":[],"preferred":false,"id":325006,"contributorType":{"id":1,"text":"Authors"},"rank":7}]}} ,{"id":70016946,"text":"70016946 - 1991 - In situ bacterial selenate reduction in the agricultural drainage systems of western Nevada","interactions":[],"lastModifiedDate":"2023-01-20T18:30:32.616173","indexId":"70016946","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":850,"text":"Applied and Environmental Microbiology","active":true,"publicationSubtype":{"id":10}},"title":"In situ bacterial selenate reduction in the agricultural drainage systems of western Nevada","docAbstract":"Dissimilatory in situ selenate reduction to elemental selenium in sediments from irrigated agricultural drainage regions of western Nevada was measured at ambient Se oxyanion concentrations. Selenate reduction was rapid, with turnover rate constants ranging from 0.04 to 1.8 h-1 at total Se concentrations in pore water of 13 to 455 nM. Estimates of removal rates of selenium oxyanions were 14, 38, and 155 μmol m-2 day-1 for South Lead Lake, Massie Slough, and Hunter Drain, respectively.
","language":"English","publisher":"American Society for Microbiology","doi":"10.1128/aem.57.2.615-617.1991","issn":"00992240","usgsCitation":"Oremland, R., Steinberg, N., Presser, T.S., and Miller, L., 1991, In situ bacterial selenate reduction in the agricultural drainage systems of western Nevada: Applied and Environmental Microbiology, v. 57, no. 2, p. 615-617, https://doi.org/10.1128/aem.57.2.615-617.1991.","productDescription":"3 p.","startPage":"615","endPage":"617","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":479696,"rank":2,"type":{"id":40,"text":"Open Access Publisher Index Page"},"url":"https://doi.org/10.1128/aem.57.2.615-617.1991","text":"Publisher Index Page"},{"id":225139,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"country":"United States","state":"Nevada","geographicExtents":"{\n \"type\": \"FeatureCollection\",\n \"features\": [\n {\n \"type\": \"Feature\",\n \"properties\": {},\n \"geometry\": {\n \"type\": \"Polygon\",\n \"coordinates\": [\n [\n [\n -116.60888671874999,\n 42.00032514831621\n ],\n [\n -119.970703125,\n 42.00032514831621\n ],\n [\n -120.05859375,\n 39.11301365149975\n ],\n [\n -117.00439453125,\n 36.86204269508728\n ],\n [\n -116.60888671874999,\n 42.00032514831621\n ]\n ]\n ]\n }\n }\n ]\n}","volume":"57","issue":"2","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a3999e4b0c8380cd6198f","contributors":{"authors":[{"text":"Oremland, R.S.","contributorId":97512,"corporation":false,"usgs":true,"family":"Oremland","given":"R.S.","email":"","affiliations":[],"preferred":false,"id":374944,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Steinberg, N.A.","contributorId":29573,"corporation":false,"usgs":true,"family":"Steinberg","given":"N.A.","email":"","affiliations":[],"preferred":false,"id":374941,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Presser, T. S.","contributorId":93875,"corporation":false,"usgs":true,"family":"Presser","given":"T.","email":"","middleInitial":"S.","affiliations":[],"preferred":false,"id":374943,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Miller, L.G.","contributorId":32522,"corporation":false,"usgs":true,"family":"Miller","given":"L.G.","email":"","affiliations":[],"preferred":false,"id":374942,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":2001485,"text":"2001485 - 1991 - Microwaves to remove skeletal bone from fish carcasses","interactions":[],"lastModifiedDate":"2012-02-02T00:15:00","indexId":"2001485","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":18,"text":"Report"},"publicationSubtype":{"id":1,"text":"Federal Government Series"},"seriesTitle":{"id":70,"text":"Research Information Bulletin","active":false,"publicationSubtype":{"id":1}},"seriesNumber":"22","title":"Microwaves to remove skeletal bone from fish carcasses","docAbstract":"No abstract available at this time","language":"English","publisher":"U.S. Fish and Wildlife Service","collaboration":"91-079/NF","usgsCitation":"Rottiers, D.V., 1991, Microwaves to remove skeletal bone from fish carcasses: Research Information Bulletin 22, 2 p.","productDescription":"2 p.","startPage":"0","endPage":"2","numberOfPages":"2","costCenters":[{"id":365,"text":"Leetown Science Center","active":true,"usgs":true}],"links":[{"id":199064,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"4f4e4a57e4b07f02db62e894","contributors":{"authors":[{"text":"Rottiers, D. V.","contributorId":49301,"corporation":false,"usgs":true,"family":"Rottiers","given":"D.","middleInitial":"V.","affiliations":[],"preferred":false,"id":325790,"contributorType":{"id":1,"text":"Authors"},"rank":1}]}} ,{"id":70015004,"text":"70015004 - 1991 - Satellite and earth science data management activities at the U.S. geological survey's EROS data center","interactions":[],"lastModifiedDate":"2012-03-12T17:18:58","indexId":"70015004","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":24,"text":"Conference Paper"},"publicationSubtype":{"id":19,"text":"Conference Paper"},"title":"Satellite and earth science data management activities at the U.S. geological survey's EROS data center","docAbstract":"The U.S. Geological Survey's Earth Resources Observation Systems (EROS) Data Center, the national archive for Landsat data, has 20 years of experience in acquiring, archiving, processing, and distributing Landsat and earth science data. The Center is expanding its satellite and earth science data management activities to support the U.S. Global Change Research Program and the National Aeronautics and Space Administration (NASA) Earth Observing System Program. The Center's current and future data management activities focus on land data and include: satellite and earth science data set acquisition, development and archiving; data set preservation, maintenance and conversion to more durable and accessible archive medium; development of an advanced Land Data Information System; development of enhanced data packaging and distribution mechanisms; and data processing, reprocessing, and product generation systems.","largerWorkTitle":"GIS/LIS 1991 ACSM-ASPRS Fall Convention","conferenceTitle":"1991 ACSM-ASPRS Fall Convention","conferenceDate":"28 October 1991 through 1 November 1991","conferenceLocation":"Atlanta, GA, USA","language":"English","publisher":"Publ by ASPRS","publisherLocation":"Bethesda, MD, United States","usgsCitation":"Carneggie, D.M., Metz, G.G., Draeger, W.C., and Thompson, R.J., 1991, Satellite and earth science data management activities at the U.S. geological survey's EROS data center, in GIS/LIS 1991 ACSM-ASPRS Fall Convention, Atlanta, GA, USA, 28 October 1991 through 1 November 1991.","costCenters":[],"links":[{"id":224343,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505b86cde4b08c986b316130","contributors":{"authors":[{"text":"Carneggie, David M.","contributorId":62758,"corporation":false,"usgs":true,"family":"Carneggie","given":"David","email":"","middleInitial":"M.","affiliations":[],"preferred":false,"id":369829,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Metz, Gary G.","contributorId":45466,"corporation":false,"usgs":true,"family":"Metz","given":"Gary","email":"","middleInitial":"G.","affiliations":[],"preferred":false,"id":369827,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Draeger, William C.","contributorId":46522,"corporation":false,"usgs":true,"family":"Draeger","given":"William","email":"","middleInitial":"C.","affiliations":[],"preferred":false,"id":369828,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Thompson, Ralph J.","contributorId":96837,"corporation":false,"usgs":true,"family":"Thompson","given":"Ralph","email":"","middleInitial":"J.","affiliations":[],"preferred":false,"id":369830,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70016902,"text":"70016902 - 1991 - High-frequency spectral falloff of earthquakes, fractal dimension of complex rupture, b value, and the scaling of strength on faults","interactions":[],"lastModifiedDate":"2024-04-26T11:10:38.916102","indexId":"70016902","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2312,"text":"Journal of Geophysical Research","active":true,"publicationSubtype":{"id":10}},"title":"High-frequency spectral falloff of earthquakes, fractal dimension of complex rupture, b value, and the scaling of strength on faults","docAbstract":"The high-frequency falloff ω−γ of earthquake displacement spectra and the b value of aftershock sequences are attributed to the character of spatially varying strength along fault zones. I assume that the high frequency energy of a main shock is produced by a self-similar distribution of subevents, where the number of subevents with radii greater than R is proportional to R−D, D being the fractal dimension. In this model, an earthquake is composed of a hierarchical set of smaller earthquakes. The static stress drop is parameterized to be proportional to Rη, and strength is assumed to be proportional to static stress drop. I find that a distribution of subevents with D = 2 and stress drop independent of seismic moment (η = 0) produces a main shock with an ω−2 falloff, if the subevent areas fill the rupture area of the main shock. By equating subevents to “islands” of high stress of a random, self-similar stress field on a fault, I relate D to the scaling of strength on a fault, such that D = 2 − η. Thus D = 2 corresponds to constant stress drop scaling (η = 0) and scale-invariant fault strength. A self-similar model of aftershock rupture zones on a fault is used to determine the relationship between the b value, the size distribution of aftershock rupture zones, and the scaling of strength on a fault. The b value for aftershock sequences on a fault is found to equal (3 − 1.5η)/(3 + η). Therefore this model indicates that the typically observed spectral falloffs of ω−2 and b values of 1 can be entirely caused by scale-invariant strength (η = 0) along fault zones.
A mathematical algorithm is developed to determine the depth-dependent profiles of specific storage and hydraulic conductivity resulting from overburden stress in horizontally isotropic artesian aquifers. Vertical variations in the void ratio of the aquifer matrix brought about by overburden stresses determine the pore-volume compressibility and matrix permeability at specific depths within the aquifers which, in turn, determine the depth-dependent profiles of specific storage and hydraulic conductivity. Time-drawdown curves are obtained for two sands subjected to different overburden stresses. For shallow artesian aquifers with low overburden stress and high aquifer matrix compressibility, noticeable vertical gradients in specific storage occur. These vertical gradients cause deviations from the classical time-drawdown curves defined by the Theis solution. These deviations are negligible for deep artesian aquifers.
","language":"English","publisher":"Elsevier","doi":"10.1016/0022-1694(91)90144-7","issn":"00221694","usgsCitation":"Sepulveda, N., and Zack, A.L., 1991, The effects of overburden stress on the specific storage and hydraulic conductivity of artesian aquifers: Journal of Hydrology, v. 128, no. 1-4, p. 305-321, https://doi.org/10.1016/0022-1694(91)90144-7.","productDescription":"17 p.","startPage":"305","endPage":"321","numberOfPages":"17","costCenters":[],"links":[{"id":223209,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"128","issue":"1-4","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505bab91e4b08c986b322f1d","contributors":{"authors":[{"text":"Sepulveda, N.","contributorId":56805,"corporation":false,"usgs":true,"family":"Sepulveda","given":"N.","email":"","affiliations":[],"preferred":false,"id":373250,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Zack, A. L.","contributorId":104911,"corporation":false,"usgs":true,"family":"Zack","given":"A.","email":"","middleInitial":"L.","affiliations":[],"preferred":false,"id":373251,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70016857,"text":"70016857 - 1991 - Melting and thermodynamic properties of pyrope (Mg3Al2Si3O12)","interactions":[],"lastModifiedDate":"2024-04-12T14:36:28.231218","indexId":"70016857","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1759,"text":"Geochimica et Cosmochimica Acta","active":true,"publicationSubtype":{"id":10}},"displayTitle":"Melting and thermodynamic properties of pyrope (Mg3Al2Si3O12)","title":"Melting and thermodynamic properties of pyrope (Mg3Al2Si3O12)","docAbstract":"The heat capacity of Mg3Al2Si3O12 glass has been measured from 10 to 1000 K by adiabatic and differential scanning calorimetry. The heat capacity of crystalline pyrope has been determined from drop-calorimetry measurements between 820 and 1300 K. From these and previously published results a consistent set of thermodynamic data is presented for pyrope and Mg3Al2Si3O12 glass and liquid for the interval 0–2000 K. The enthalpy of fusion at
The submarine Mahukona Volcano, west of the island of Hawaii, is located on the Loa loci line between Kahoolawe and Hualalai Volcanoes. The west rift zone ridge of the volcano extends across a drowned coral reef at about-1150 m and a major slope break at about-1340 m, both of which represent former shoreines. The summit of the volcano apparently reached to about 250 m above sea level (now at-1100 m depth) did was surmounted by a roughly circular caldera. A econd rift zone probably extended toward the east or sutheast, but is completely covered by younger lavas from the adjacent subaerial volcanoes. Samples were vecovered from nine dredges and four submersible lives. Using subsidence rates and the compositions of flows which drape the dated shoreline terraces, we infer that the voluminous phase of tholeiitic shield growth ended about 470 ka, but tholeiitic eruptions continued until at least 435 ka. Basalt, transitional between tholeiitic and alkalic basalt, erupted at the end of tholeiitic volcanism, but no postshield-alkalic stage volcanism occurred. The summit of the volcano apparently subcided below sea level between 435 and 365 ka. The tholeiitic lavas recovered are compositionally diverse.
Very rapid subduction of the Farallon plate under southwestern North America between 60 and 40 Ma was accompanied by a relatively low volume of magmatism throughout the southwestern United States and northern Mexico. Between 40 and 20 Ma, when subduction slowed significantly and in one area may have even stopped, magmatism became widespread and voluminous from Nevada and Utah to central Mexico. This correlation of rapid subduction with a relatively low volume of magmatism can be explained by the observation that subduction-related andesitic arc volcanism, often formed in a Laramide-style compressional regime, is relatively low volume compared to continental volcanism. The shallow roots of arc volcanic systems are clearly exposed in the porphyry copper deposits found in currently active arcs and common throughout southwestern North America between 60 and 50 Ma. By 43 Ma, worldwide plate motions changed, the Pacific plate began moving away from North America, and subduction of the Farallon plate slowed. By around 36 Ma, the easternmost part of the East Pacific Rise, which was located between the Pioneer and Murray fracture zones, approached the trench and the young, hot, buoyant lithosphere appears to have clogged part of the subduction zone. Uplift on land became widespread. Voluminous continental magmatism formed the Sierra Madre Occidental (SMO) of Mexico, one of the largest batholiths in the world, as well as volcanic centers now exposed in the San Juan Mountains of Colorado and the Rio Grande Rift of New Mexico. Vectors of motion of the Pacific plate relative to the North American plate determined by Stock and Molnar (1988) are consistent with formation of a transtensional environment along the plate boundary sufficient to create a 100- to 200-km-wide void just landward of the old volcanic arc. While the SMO batholith was forming within this void, the Monterey and Arguello microplates just offshore to the west were broken off from the Farallon plate and rotated so that the East Pacific Rise in this immediate area became nearly perpendicular to the trench and perpendicular to the vector of motion of the Pacific plate relative to North America. Formation of the SMO batholith was followed between 24 and 20 Ma by a major increase in the rate of subduction of the Guadalupe plate, a fragment of the former Farallon plate, and by increasing mylonitization, extension, and uplift in the metamorphic core complexes that extend northwestward through southern Arizona from the northern end of the SMO batholith. The plate margin underwent another major change between 12.5 and 10 Ma when subduction again stopped, strike slip faulting became dominant along the coast, the Basin and Range Province opened, and numerous tectonostratigraphic terranes in southern California underwent large rotations. By 3 Ma a large, new terrane had been severed from North America immediately west of the SMO batholith as the Gulf of California opened. These observations can be explained by a model for the weakening and ultimate falling apart of the uppermost part of the subducted oceanic plate in the 20–30 m.y. after the end of rapid subduction. As the plate falls apart, not only is compressional stress relieved, but significant backslip along the old subduction zone is also possible, perhaps bringing blueschists rapidly upward from 20- to 30-km depths.
A series of submerged coral reefs off northwestern Hawaii was formed during (largely glacial) intervals when the rate of local sea-level rise was less than the maximum upward growth rate of the reefs. Mass-spectrometric 234U/238U ages for samples from six such reefs range from 17 to 475 ka and indicate that this part of the Hawaiian Ridge has been subsiding at a roughly uniform rate of 2.6 mm/yr for the past 475 ka. The 234U/238U ages are in general agreement with model ages of reef drowning (based on estimates of paleo-sea-level stands derived from oxygen-isotope ratios of deep-sea sediments), but there are disagreements in detail. The high attainable precision (±10 ka or better on samples younger than ∼800 ka), large applicable age range, relative robustness against open-system behavior, and ease of analysis for this technique hold great promise for future applications of dating of 50-1000 ka coral.
","language":"English","publisher":"Geological Society of America","doi":"10.1130/0091-7613(1991)019<0171:CSROHD>2.3.CO;2","usgsCitation":"Ludwig, K., Szabo, B.J., Moore, J., and Simmons, K.R., 1991, Crustal subsidence rate off Hawaii determined from 234U/238U ages of drowned coral reefs: Geology, v. 19, no. 2, p. 171-174, https://doi.org/10.1130/0091-7613(1991)019<0171:CSROHD>2.3.CO;2.","productDescription":"4 p.","startPage":"171","endPage":"174","numberOfPages":"4","costCenters":[],"links":[{"id":225081,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"country":"United States","state":"Hawaii","geographicExtents":"{\n \"type\": \"FeatureCollection\",\n \"features\": [\n {\n \"type\": \"Feature\",\n \"properties\": {},\n \"geometry\": {\n \"type\": \"Polygon\",\n \"coordinates\": [\n [\n [\n -161.6748046875,\n 16.341225619207496\n ],\n [\n -152.9296875,\n 16.341225619207496\n ],\n [\n -152.9296875,\n 25.005972656239187\n ],\n [\n -161.6748046875,\n 25.005972656239187\n ],\n [\n -161.6748046875,\n 16.341225619207496\n ]\n ]\n ]\n }\n }\n ]\n}","volume":"19","issue":"2","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"5059fcf1e4b0c8380cd4e529","contributors":{"authors":[{"text":"Ludwig, K.R.","contributorId":97112,"corporation":false,"usgs":true,"family":"Ludwig","given":"K.R.","email":"","affiliations":[{"id":218,"text":"Denver Federal Center","active":false,"usgs":true}],"preferred":false,"id":374631,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Szabo, Barney J.","contributorId":6848,"corporation":false,"usgs":true,"family":"Szabo","given":"Barney","email":"","middleInitial":"J.","affiliations":[],"preferred":false,"id":374628,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Moore, J.G.","contributorId":67496,"corporation":false,"usgs":true,"family":"Moore","given":"J.G.","email":"","affiliations":[],"preferred":false,"id":374629,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Simmons, K. R.","contributorId":68771,"corporation":false,"usgs":true,"family":"Simmons","given":"K.","email":"","middleInitial":"R.","affiliations":[],"preferred":false,"id":374630,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70016436,"text":"70016436 - 1991 - An AEM-TEM study of weathering and diagenesis, Abert Lake, Oregon: II. Diagenetic modification of the sedimentary assemblage","interactions":[],"lastModifiedDate":"2024-04-12T14:59:40.538409","indexId":"70016436","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1759,"text":"Geochimica et Cosmochimica Acta","active":true,"publicationSubtype":{"id":10}},"title":"An AEM-TEM study of weathering and diagenesis, Abert Lake, Oregon: II. Diagenetic modification of the sedimentary assemblage","docAbstract":"This paper compares the mineralogy and chemistry of clay minerals in sediments from various depths and positions in Abert Lake and surrounding playa with those of the weathered materials entering the lake in order to reveal the nature and extent of post-depositional mineralogical modification.
Analytical electron microscope (AEM) data from individual clay particles reveal that each sample is comprised of a highly inhomogeneous smectite assemblage. The thin clay flakes (commonly less than 10 nm wide) display a complete range in octahedral sheet compositions from nearly dioctahedral to nearly trioctahedral. The very abundant Mg-rich lake smectites with an estimated composition K0.29(Al0.23-Mg2.16Fe0.30)Si3.80Al0.20O10(OH)2 are not formed by weathering. This confirms the importance of diagenetic Mg uptake. Lattice-fringe imaging failed to reveal distinct brucite-like or vermiculite-like layers, suggesting that interstratifications of this type are rare or absent. Siliceous coatings on clay particles (identified by silica excess in smectite analyses) seem to favor topotactic overgrowth of stevensite rather than addition of brucite-like layers to the dioctahedral nuclei. The growth of K-stevensite dilutes the Al content of the crystal, and thus the increasing diagenetic modification reduces rather than supplements its illite component.
Smectite compositions within individual samples were highly variable, yet source-related characteristics such as the abundance of Fe-rich smectite were apparent. Little evidence for systematic K or Mg enrichment with depth was identified in samples from depths of down to 16 feet below the sediment-water interface. The most magnesian assemblages are associated both with weathering sources of Mg-rich smectite and playa environments subjected to repeated wetting and drying cycles. Thus, the observations suggest that clay compositions primarily reflect changes in lake levels, brine composition, and source characteristics, rather than time and depth/compaction effects. Other diagenetic reactions in the sediment include recrystallization of Na-rich silica gel and diatom fragments. Abundant, submicron-sized, untwinned, euhedral crystals of K-feldspar are interpreted to be authigenic in origin.
","language":"English","publisher":"Elsevier","doi":"10.1016/0016-7037(91)90445-B","issn":"00167037","usgsCitation":"Banfield, J., Jones, B., and Veblen, D., 1991, An AEM-TEM study of weathering and diagenesis, Abert Lake, Oregon: II. Diagenetic modification of the sedimentary assemblage: Geochimica et Cosmochimica Acta, v. 55, no. 10, p. 2795-2810, https://doi.org/10.1016/0016-7037(91)90445-B.","productDescription":"16 p.","startPage":"2795","endPage":"2810","numberOfPages":"16","costCenters":[],"links":[{"id":479778,"rank":2,"type":{"id":40,"text":"Open Access Publisher Index Page"},"url":"https://doi.org/10.1016/0016-7037(91)90445-b","text":"Publisher Index Page"},{"id":223068,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"55","issue":"10","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"5059e9cde4b0c8380cd48480","contributors":{"authors":[{"text":"Banfield, J.F.","contributorId":48710,"corporation":false,"usgs":true,"family":"Banfield","given":"J.F.","email":"","affiliations":[],"preferred":false,"id":373507,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Jones, B.F.","contributorId":52156,"corporation":false,"usgs":true,"family":"Jones","given":"B.F.","email":"","affiliations":[],"preferred":false,"id":373508,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Veblen, D.R.","contributorId":25300,"corporation":false,"usgs":true,"family":"Veblen","given":"D.R.","email":"","affiliations":[],"preferred":false,"id":373506,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70016894,"text":"70016894 - 1991 - Tidal resuspension of sediments in northern Chesapeake Bay","interactions":[],"lastModifiedDate":"2024-09-20T11:15:59.536287","indexId":"70016894","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2667,"text":"Marine Geology","active":true,"publicationSubtype":{"id":10}},"title":"Tidal resuspension of sediments in northern Chesapeake Bay","docAbstract":"Tidal resuspension experiments were carried out on two occasions during the winter of 1988–1989 at a disposal site for hydraulically dredged sediments in northern Chesapeake Bay to determine the influence of tidal resuspension on erosion of recent deposits. The results indicate that normal tidal erosion depths were only a fraction of a millimeter per half tidal cycle and probably did not account for the majority of the apparent sediment loss. Erosion rate was found to be a linear function of the excess of estimated shear stress over a critical value, but both the constant of proportionality (M = 0.5 mg/cm2/h) and the critical shear stress (τc = 0.16 dynes/cm2 were much less than many previously reported results. The most likely explanation for these low values is that the thin layer of surface sediments involved in regular tidal resuspension had only a few hours at most to consolidate between resuspension events. Observed resuspended sediment concentrations (up to 35 mg/l above background levels) were much less than those reported for previous observations of tidal resuspension in the nearby channel, presumably due to greater stratification and lower tidal velocities at the disposal site. Salinity-induced stratification of the water column is estimated to have reduced shear stresses by up to 50% relative to the neutrally stratified case. Regular tidal resuspension of a thin layer of surface sediments is implicated as a potentially important aspect of the typical benthic environment of northern Chesapeake Bay, even if it is not the most important factor in massive sediment erosion and transport.
Mechanisms for electron transport to Fe(III) were investigated in GS-15, a novel anaerobic microorganism which can obtain energy for growth hy coupling the complete oxidation of organic acids or aromatic compounds to the reduction of Fe(III) to Fe(II). The results indicate that Fe(III) reduction proceeds through a type b cytochrome and a membrane-bound Fe(III) reductase which is distinct from the nitrate reductase.
","language":"English","publisher":"American Society for Microbiology","doi":"10.1128/aem.57.3.867-870.1991","issn":"00992240","usgsCitation":"Gorby, Y., and Lovley, D.R., 1991, Electron transport in the dissimilatory iron reducer, GS-15: Applied and Environmental Microbiology, v. 57, no. 3, p. 867-870, https://doi.org/10.1128/aem.57.3.867-870.1991.","productDescription":"4 p.","startPage":"867","endPage":"870","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":480418,"rank":2,"type":{"id":40,"text":"Open Access Publisher Index Page"},"url":"https://doi.org/10.1128/aem.57.3.867-870.1991","text":"Publisher Index Page"},{"id":224660,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"57","issue":"3","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a08a9e4b0c8380cd51bfd","contributors":{"authors":[{"text":"Gorby, Y.A.","contributorId":64815,"corporation":false,"usgs":true,"family":"Gorby","given":"Y.A.","affiliations":[],"preferred":false,"id":374679,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Lovley, Derek R.","contributorId":107852,"corporation":false,"usgs":true,"family":"Lovley","given":"Derek","middleInitial":"R.","affiliations":[],"preferred":false,"id":374680,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70016845,"text":"70016845 - 1991 - Shoreline deposits and diagenesis resulting from two Late Pleistocene highstands near +5 and +6 metres, Durban, South Africa","interactions":[],"lastModifiedDate":"2024-09-23T11:30:57.564741","indexId":"70016845","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2667,"text":"Marine Geology","active":true,"publicationSubtype":{"id":10}},"title":"Shoreline deposits and diagenesis resulting from two Late Pleistocene highstands near +5 and +6 metres, Durban, South Africa","docAbstract":"In exposures of Pleistocene rocks on the east coast of South Africa, eight sedimentary facies were distinguished on the basis of petrology, grain size, internal structures and field relationships. These are interpreted as deposits of surf zone, breaker zone, swash zone, backbeach, boulder beach and dune environments. Three phases of deposition and diagenesis are recognized. As a result of the stabilising effect of pre-existing coastal facies, the deposits from successive sea level stands are stacked vertically in a narrow coast-normal strip. Early cementation prevented erosion of the deposits during subsequent transgressions.
Deposition of subsequent facies took place on an existing coastal dune (Facies 1). A terrace was cut into this dune at a sea level 4.5 to 5 m above present. At this sea level, clastic shoreline sediments were deposited which make up the main sedimentary sequence exposed (Facies 2–7). The steep swash zone, coarse grain size, and comparison with modern conditions in the study area indicate clastic deposition on a high-energy, wave-dominated, microtidal coastline. Vertical stacking of progressively shallower water facies indicates progradation associated with slightly regressive conditions, prior to stranding of the succession above sea level. During a subsequent transgression to 5.5 or 6 m above present sea level, a second terrace was cut across the existing facies, which by then were partly lithified. A boulder beach (Facies 8) deposited on this terrace is indicative of high wave energy and a rocky coastline, formed by existing cemented coastal facies. Comparison with dated deposits from other parts of the South African coast suggest a Late Pleistocene age for Facies 2–8. Deposition was terminated by subsequent regression and continuing low sea levels during the remainder of the Pleistocene.
Cementation of the facies took place almost entirely by carbonate precipitation. The presence of isopachous fibrous cements suggests early cementation of Facies 1, 2, 3 and 4 under marine conditions, initially as aragonite which has since inverted to calcite. Facies 5, 6 and 7 are cemented only by equant calcite spar, evidence of cementation in the meteoric phreatic and vadose zones. Lowering of the water table during regression caused the remaining pore space in Facies 1, 2, 3 and 4 to be filled with equant calcite spar. Decementation in a 130 cm wide zone is attributed to water table shifts associated with the later transgression which deposited Facies 8.
The vertical stacking of the two depositional sequences may be attributed to rapid cementation of Facies 2, 3, 4, 5, 6 and 7 under humid, subtropical conditions. This lithified sequence then acted as a focus for deposition of coarse-grained shoreline facies (Facies 8) during the subsequent transgression.
A deep seismic-reflection profile in northern Lake Michigan, midcontinent North America, provides a cross section of the crust across the 1850 Ma Penokean orogen, in which an Early Proterozoic island-arc complex was deformed between two converging Archean continental masses. The island-arc crust is about 40 km thick and has a few kilometres of intensely reflective rocks near its base, above which it is variably reflective to transparent. The Archean terranes have thicker crust, as much as 50 km, the lower 20-25 km of which is strongly reflective. Abrupt offsets of Moho near terrane boundaries may have been preserved since accretion during the Penokean orogeny.