The separation and characterization of complex mixtures of polychlorinated biphenyls (PCBs) is approached from the perspective of a problem in chemometrics. A technique for quantitative determination of PCB congeners is described as well as an enrichment technique designed to isolate only those congener residues which induce mixed aryl hydrocarbon hydroxylase enzyme activity. A congener-specific procedure is utilized for the determination of PCBs in whichn-alkyl trichloroacetates are used as retention index marker compounds. Retention indices are reproducible in the range of ±0.05 to ±0.7 depending on the specific congener. A laboratory data base system developed to aid in the editing and quantitation of data generated from capillary gas chromatography was employed to quantitate chromatographic data. Data base management was provided by computer programs written in VAX-DSM (Digital Standard MUMPS) for the VAX-DEC (Digital Equipment Corp.) family of computers.
In the chemometric evaluation of these complex chromatographic profiles, data are viewed from a single analysis as a point in multi-dimensional space. Principal Components Analysis was used to obtain a representation of the data in a lower dimensional space. Two-and three-dimensional proections based on sample scores from the principal components models were used to visualize the behavior of Aroclor® mixtures. These models can be used to determine if new sample profiles may be represented by Aroclor profiles. Concentrations of individual congeners of a given chlorine substitution may be summed to form homologue concentration. However, the use of homologue concentrations in classification studies with environmental samples can lead to erroneous conclusions about sample similarity. Chemometric applications are discussed for evaluation of Aroclor mixture analysis and compositional description of environmental residues of PCBs in eggs of Forster's terns (Sterna fosteri) collected from colonies near Lake Poygan and Green Bay, Wisconsin. The application of chemometrics is extended to the comparison of: a) Aroclors and PCB-containing environmental samples; to b) fractions of Aroclors and of environmental samples that have been enriched in congeners which induce mixed aryl hydrocarbon hydroxylase enzyme activity.
","language":"English","publisher":"Springer","doi":"10.1007/BF01055903","usgsCitation":"Schwartz, T.R., and Stalling, D.L., 1991, Chemometric comparison of polychlorinated biphenyl residues and toxicologically active polychlorinated biphenyl congeners in the eggs of Forster's Terns (Sterna fosteri): Archives of Environmental Contamination and Toxicology, v. 20, no. 2, p. 183-199, https://doi.org/10.1007/BF01055903.","productDescription":"17 p.","startPage":"183","endPage":"199","costCenters":[{"id":192,"text":"Columbia Environmental Research Center","active":true,"usgs":true},{"id":531,"text":"Patuxent Wildlife Research Center","active":true,"usgs":true}],"links":[{"id":330745,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"20","issue":"2","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"581d9e2ee4b0dee4cc90cbfb","contributors":{"authors":[{"text":"Schwartz, Ted R.","contributorId":36510,"corporation":false,"usgs":true,"family":"Schwartz","given":"Ted","email":"","middleInitial":"R.","affiliations":[],"preferred":false,"id":653061,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Stalling, David L.","contributorId":176670,"corporation":false,"usgs":false,"family":"Stalling","given":"David","email":"","middleInitial":"L.","affiliations":[],"preferred":false,"id":653062,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70178560,"text":"70178560 - 1991 - Improved selenium recovery from tissue with modified sample decomposition","interactions":[],"lastModifiedDate":"2024-05-14T15:24:10.729771","indexId":"70178560","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2533,"text":"Journal of the Association of Official Analytical Chemists","active":true,"publicationSubtype":{"id":10}},"title":"Improved selenium recovery from tissue with modified sample decomposition","docAbstract":"The present paper describes a simple modification of a recently reported decomposition method for determination of selenium in biological tissue by hydride generation atomic absorption. The modified method yielded slightly higher selenium recoveries (3-4%) for selected reference tissues and fish tissue spiked with selenomethionine. Radiotracer experiments indicated that the addition of a small volume of hydrochloric acid to the wet digestate mixture reduced slight losses of selenium as the sample initially went to dryness before ashing. With the modified method, selenium spiked as selenomethionine behaved more like the selenium in reference tissues than did the inorganic spike forms when this digestion modification was used.
","language":"English","publisher":"Association of Official Analytical Chemists","doi":"10.1093/jaoac/74.3.570","usgsCitation":"Brumbaugh, W.G., and Walther, M., 1991, Improved selenium recovery from tissue with modified sample decomposition: Journal of the Association of Official Analytical Chemists, v. 74, no. 3, p. 570-571, https://doi.org/10.1093/jaoac/74.3.570.","productDescription":"2 p.","startPage":"570","endPage":"571","costCenters":[{"id":192,"text":"Columbia Environmental Research Center","active":true,"usgs":true}],"links":[{"id":331244,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"74","issue":"3","noUsgsAuthors":false,"publicationDate":"2020-01-14","publicationStatus":"PW","scienceBaseUri":"583d5036e4b0d9329c80c5a9","contributors":{"authors":[{"text":"Brumbaugh, W. G.","contributorId":121189,"corporation":false,"usgs":true,"family":"Brumbaugh","given":"W.","email":"","middleInitial":"G.","affiliations":[],"preferred":false,"id":654360,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Walther, M.J.","contributorId":107941,"corporation":false,"usgs":true,"family":"Walther","given":"M.J.","email":"","affiliations":[],"preferred":false,"id":654361,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70180731,"text":"70180731 - 1991 - A sigmoid model to predict gastric evacuation rates of smallmouth bass Micropterus dolomieui fed juvenile salmon","interactions":[],"lastModifiedDate":"2017-02-01T13:02:33","indexId":"70180731","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1169,"text":"Canadian Journal of Fisheries and Aquatic Sciences","active":true,"publicationSubtype":{"id":10}},"title":"A sigmoid model to predict gastric evacuation rates of smallmouth bass Micropterus dolomieui fed juvenile salmon","docAbstract":"Laboratory experiments were conducted to examine the effects of water temperature, predator size, prey size, and prey number on gastric evacuation of smallmouth bass (Micropterus dolomieui) fed juvenile salmon. The smallmouth bass were allowed to feed voluntarily after 24–48 h of starvation and stomachs were pumped at intervals of 1–4 h until 90% of the stomach contents were evacuated (E90). Evacuation approximated an S-shaped curve over time, and a sigmoid model was developed to predict evacuation at varying water temperatures, total meal weights, predator sizes, and prey number. The rate of evacuation increased with increasing water temperature, meal weight, or predator size. The E90 increased with larger meal weights but decreased with increasing temperature or predator size. E90 ranged between 4 and 95 h, depending upon conditions. E90 was slower than those estimated previously for another predator of salmon, the stomachless northern squawfish (Ptychocheilus oregonensis).
","language":"English","publisher":"NRC Research Press","doi":"10.1139/f91-109","usgsCitation":"Rogers, J.B., and Burley, C.C., 1991, A sigmoid model to predict gastric evacuation rates of smallmouth bass Micropterus dolomieui fed juvenile salmon: Canadian Journal of Fisheries and Aquatic Sciences, v. 48, no. 5, p. 933-937, https://doi.org/10.1139/f91-109.","productDescription":"5 p. ","startPage":"933","endPage":"937","costCenters":[{"id":654,"text":"Western Fisheries Research Center","active":true,"usgs":true}],"links":[{"id":334544,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"48","issue":"5","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"58a03784e4b099f50d3e0512","contributors":{"authors":[{"text":"Rogers, Jean Beyer","contributorId":179018,"corporation":false,"usgs":false,"family":"Rogers","given":"Jean","email":"","middleInitial":"Beyer","affiliations":[],"preferred":false,"id":662181,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Burley, Craig C.","contributorId":179019,"corporation":false,"usgs":false,"family":"Burley","given":"Craig","email":"","middleInitial":"C.","affiliations":[],"preferred":false,"id":662182,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70180736,"text":"70180736 - 1991 - Heterosis and outbreeding depression: A multi-locus model and an application to salmon production","interactions":[],"lastModifiedDate":"2017-02-01T13:58:27","indexId":"70180736","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1661,"text":"Fisheries Research","active":true,"publicationSubtype":{"id":10}},"title":"Heterosis and outbreeding depression: A multi-locus model and an application to salmon production","docAbstract":"Both artificial propagation and efforts to preserve or augment natural populations sometimes involve, wittingly or unwittingly, the mixing of different gene pools. The advantages of such mixing vis-à-vis the alleviation of inbreeding depression are well known. Acknowledged, but less well understood, are the complications posed by outbreeding depression. This paper derives a simple model of outbreeding depression and demonstrates that it is reasonably possible to predict the generation-to-generation fitness course of hybrids derived from parents from different origins. Genetic difference, or distance between parental types, is defined by the drop in fitness experienced by one type reared at the site to which the other is locally adapted. For situations where decisions involving stock mixing must be made in the absence of complete information, a sensitivity analysis-based conflict resolution method (the Good-Bad-Ugly model) is described.
","language":"English","publisher":"Elsevier","doi":"10.1016/0165-7836(91)90095-W","usgsCitation":"Emlen, J.M., 1991, Heterosis and outbreeding depression: A multi-locus model and an application to salmon production: Fisheries Research, v. 12, no. 3, p. 187-212, https://doi.org/10.1016/0165-7836(91)90095-W.","productDescription":"31 p. ","startPage":"187","endPage":"212","costCenters":[{"id":654,"text":"Western Fisheries Research Center","active":true,"usgs":true}],"links":[{"id":334552,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"12","issue":"3","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"58a03784e4b099f50d3e050e","contributors":{"authors":[{"text":"Emlen, John M.","contributorId":168812,"corporation":false,"usgs":true,"family":"Emlen","given":"John","email":"","middleInitial":"M.","affiliations":[{"id":654,"text":"Western Fisheries Research Center","active":true,"usgs":true}],"preferred":false,"id":662192,"contributorType":{"id":1,"text":"Authors"},"rank":1}]}} ,{"id":70180739,"text":"70180739 - 1991 - Physiological response of largemouth bass to angling stress","interactions":[],"lastModifiedDate":"2017-02-02T10:11:19","indexId":"70180739","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":3624,"text":"Transactions of the American Fisheries Society","active":true,"publicationSubtype":{"id":10}},"title":"Physiological response of largemouth bass to angling stress","docAbstract":"The physiological effects of catch-and-release fishing on largemouth bass Micropterus salmoides from Lake Powell and Mantua Reservoir, Utah, were evaluated, and an estimate of the time needed for recovery from hooking stress was obtained. Fatigue in Lake Powell fish, as indicated by elevated blood lactate, was directly proportional to hooking time (1–5 min) and water temperature, but recovery from the hyperlacticemia was relatively rapid (about 24 h). Hyperglycemia, an indicator of stress hormone production, did not occur in largemouth bass hooked and played for 1–5 min in the coldest water (11–13°C), was moderate in fish hooked and played at l6–20°C, and was severe in fish played for 5 min at 28–30°C. Fish held for recovery in live cages suffered further hyperglycemia, presumably because of the stress of confinement. Ionoregulation, as indicated by relatively stable plasma chloride values, was not immediately affected in largemouth bass caught at water temperatures of 11–13°C or 28–30°C, but an unusual hyperchloremia developed in fish hooked and played at 16–20°C. During recovery, the expected progressive hypochloremia developed. Plasma osmolality was somewhat affected by hooking at all water temperatures tested, but recovery was almost complete within about 8 h. Mantua Reservoir fish were hooked and played only at water temperatures of 23–26°C. The hyperlacticemia and hyperglycemia that occurred were generally more severe than in the Lake Powell fish hooked and played at either 16–20°C or 28–30°C. However, effects on plasma chloride and osmolality were similar to those occurring in Lake Powell fish.
","language":"English","publisher":"Taylor & Francis","doi":"10.1577/1548-8659(1991)120<0629:PROLBT>2.3.CO;2","usgsCitation":"Gustaveson, A.W., Wydoski, R.S., and Wedemeyer, G.A., 1991, Physiological response of largemouth bass to angling stress: Transactions of the American Fisheries Society, v. 120, no. 5, p. 629-636, https://doi.org/10.1577/1548-8659(1991)120<0629:PROLBT>2.3.CO;2.","productDescription":"8 p. ","startPage":"629","endPage":"636","costCenters":[{"id":654,"text":"Western Fisheries Research Center","active":true,"usgs":true}],"links":[{"id":334580,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"120","issue":"5","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"58945336e4b0fa1e59b8680f","contributors":{"authors":[{"text":"Gustaveson, A. Wayne","contributorId":179022,"corporation":false,"usgs":false,"family":"Gustaveson","given":"A.","email":"","middleInitial":"Wayne","affiliations":[],"preferred":false,"id":662229,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Wydoski, Richard S.","contributorId":81856,"corporation":false,"usgs":true,"family":"Wydoski","given":"Richard","email":"","middleInitial":"S.","affiliations":[],"preferred":false,"id":662230,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Wedemeyer, Gary A.","contributorId":30668,"corporation":false,"usgs":true,"family":"Wedemeyer","given":"Gary","email":"","middleInitial":"A.","affiliations":[],"preferred":false,"id":662231,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70180935,"text":"70180935 - 1991 - A line transect model for aerial surveys","interactions":[],"lastModifiedDate":"2017-02-08T15:11:48","indexId":"70180935","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1039,"text":"Biometrics","active":true,"publicationSubtype":{"id":10}},"title":"A line transect model for aerial surveys","docAbstract":"We employ a line transect method to estimate the density of the common and Pacific loon in the Yukon Flats National Wildlife Refuge from aerial survey data. Line transect methods have the advantage of automatically taking into account “visibility bias” due to detectability difference of animals at different distances from the transect line. However, line transect methods must overcome two difficulties when applied to inaccurate recording of sighting distances due to high travel speeds, so that in fact only a few reliable distance class counts are available. We propose a unimodal detection function that provides an estimate of the effective area lost due to the blind strip, under the assumption that a line of perfect detection exists parallel to the transect line. The unimodal detection function can also be applied when a blind strip is absent, and in certain instances when the maximum probability of detection is less than 100%. A simple bootstrap procedure to estimate standard error is illustrated. Finally, we present results from a small set of Monte Carlo experiments.
","language":"English","publisher":"Wiley","doi":"10.2307/2532661","usgsCitation":"Quang, P.X., and Lanctot, R.B., 1991, A line transect model for aerial surveys: Biometrics, v. 47, no. 3, p. 1089-1102, https://doi.org/10.2307/2532661.","productDescription":"14 p.","startPage":"1089","endPage":"1102","costCenters":[{"id":114,"text":"Alaska Science Center","active":true,"usgs":true}],"links":[{"id":335066,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"country":"United States","state":"Alaska","otherGeospatial":"Yukon Flats National Wildlife Refuge","volume":"47","issue":"3","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"589c3c50e4b0efcedb74111d","contributors":{"authors":[{"text":"Quang, Pham Xuan","contributorId":179137,"corporation":false,"usgs":false,"family":"Quang","given":"Pham","email":"","middleInitial":"Xuan","affiliations":[{"id":7211,"text":"University of Alaska, Fairbanks","active":true,"usgs":false}],"preferred":false,"id":662905,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Lanctot, Richard B.","contributorId":31894,"corporation":false,"usgs":true,"family":"Lanctot","given":"Richard","email":"","middleInitial":"B.","affiliations":[{"id":6987,"text":"U.S. Fish and Wildlife Sevice","active":true,"usgs":false},{"id":7029,"text":"Queen's University, Kingston, Ontario, Canada","active":true,"usgs":false},{"id":17786,"text":"Carleton University","active":true,"usgs":false},{"id":135,"text":"Biological Resources Division","active":false,"usgs":true}],"preferred":false,"id":662906,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70016636,"text":"70016636 - 1991 - Uncertainty in climate change and drought","interactions":[],"lastModifiedDate":"2012-03-12T17:18:47","indexId":"70016636","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":24,"text":"Conference Paper"},"publicationSubtype":{"id":19,"text":"Conference Paper"},"title":"Uncertainty in climate change and drought","docAbstract":"A series of projections of climate change were applied to a watershed model of the Delaware River basin to identify sources of uncertainty in predicting effects of climate change on drought in the basin as defined by New York City reservoir contents. The watershed model is a calibrated, monthly time-step water-balance model that incorporates the operation of reservoirs and diversion canals, and accounts for all inflows to and outflows from the basin at several key nodes. The model assesses the effects of projected climate change on reservoir contents by calculating the frequency with which the basin enters drought conditions under a range of climate-change conditions. Two primary sources of uncertainty that affect predictions of drought frequency in the Delaware River basin were considered: (1) uncertainty in the amount of change in mean air temperature and precipitation, and (2) uncertainty in the effects of natural climate variability on future temperature and precipitation. Model results indicate that changes in drought frequency in the Delaware River basin are highly sensitive to changes in mean precipitation; therefore, the uncertainty associated with predictions of future precipitation has a large effect on the prediction of future drought frequency in the basin.","largerWorkTitle":"Proceedings - National Conference on Hydraulic Engineering","conferenceTitle":"Proceedings of the 1991 National Conference on Hydraulic Engineering","conferenceDate":"29 July 1991 through 2 August 1991","conferenceLocation":"Nashville, TN, USA","language":"English","publisher":"Publ by ASCE","publisherLocation":"New York, NY, United States","isbn":"0872628167","usgsCitation":"McCabe, G., Wolock, D.M., Tasker, G.D., and Ayers, M.A., 1991, Uncertainty in climate change and drought, in Proceedings - National Conference on Hydraulic Engineering, Nashville, TN, USA, 29 July 1991 through 2 August 1991, p. 1-6.","startPage":"1","endPage":"6","numberOfPages":"6","costCenters":[],"links":[{"id":225219,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505bbc23e4b08c986b328a5f","contributors":{"editors":[{"text":"Shane Richard M.","contributorId":128320,"corporation":true,"usgs":false,"organization":"Shane Richard M.","id":536337,"contributorType":{"id":2,"text":"Editors"},"rank":1}],"authors":[{"text":"McCabe, Gregory J. 0000-0002-9258-2997 gmccabe@usgs.gov","orcid":"https://orcid.org/0000-0002-9258-2997","contributorId":1453,"corporation":false,"usgs":true,"family":"McCabe","given":"Gregory J.","email":"gmccabe@usgs.gov","affiliations":[{"id":218,"text":"Denver Federal Center","active":false,"usgs":true}],"preferred":false,"id":374092,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Wolock, David M. 0000-0002-6209-938X dwolock@usgs.gov","orcid":"https://orcid.org/0000-0002-6209-938X","contributorId":540,"corporation":false,"usgs":true,"family":"Wolock","given":"David","email":"dwolock@usgs.gov","middleInitial":"M.","affiliations":[{"id":27111,"text":"National Water Quality Program","active":true,"usgs":true},{"id":503,"text":"Office of Water Quality","active":true,"usgs":true},{"id":451,"text":"National Water Quality Assessment Program","active":true,"usgs":true},{"id":37778,"text":"WMA - Integrated Modeling and Prediction Division","active":true,"usgs":true},{"id":353,"text":"Kansas Water Science Center","active":false,"usgs":true}],"preferred":true,"id":374091,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Tasker, Gary D.","contributorId":95035,"corporation":false,"usgs":true,"family":"Tasker","given":"Gary","email":"","middleInitial":"D.","affiliations":[],"preferred":false,"id":374094,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Ayers, Mark A.","contributorId":84730,"corporation":false,"usgs":true,"family":"Ayers","given":"Mark","email":"","middleInitial":"A.","affiliations":[],"preferred":false,"id":374093,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70175276,"text":"70175276 - 1991 - Interfacing data analysis and numerical modeling for tidal hydrodynamic phenomena","interactions":[],"lastModifiedDate":"2018-10-02T09:21:21","indexId":"70175276","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":5,"text":"Book chapter"},"publicationSubtype":{"id":24,"text":"Book Chapter"},"title":"Interfacing data analysis and numerical modeling for tidal hydrodynamic phenomena","docAbstract":"No abstract available.
","largerWorkType":{"id":4,"text":"Book"},"largerWorkTitle":"Tidal Hydrodynamics","largerWorkSubtype":{"id":15,"text":"Monograph"},"language":"English","publisher":"John Wiley","usgsCitation":"Cheng, R.T., Burau, J., and Gartner, J.W., 1991, Interfacing data analysis and numerical modeling for tidal hydrodynamic phenomena, chap. of Tidal Hydrodynamics, p. 201-219.","productDescription":"19 p.","startPage":"201","endPage":"219","onlineOnly":"N","additionalOnlineFiles":"N","costCenters":[{"id":154,"text":"California Water Science Center","active":true,"usgs":true},{"id":552,"text":"San Francisco Bay-Delta","active":false,"usgs":true},{"id":5079,"text":"Pacific Regional Director's Office","active":true,"usgs":true}],"links":[{"id":326071,"rank":1,"type":{"id":15,"text":"Index Page"},"url":"https://www.wiley.com/WileyCDA/WileyTitle/productCd-0471514985.html"},{"id":326072,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"57a315c5e4b006cb45558ae8","contributors":{"editors":[{"text":"Parker, B. B.","contributorId":173438,"corporation":false,"usgs":false,"family":"Parker","given":"B.","email":"","middleInitial":"B.","affiliations":[],"preferred":false,"id":644661,"contributorType":{"id":2,"text":"Editors"},"rank":1}],"authors":[{"text":"Cheng, R. T.","contributorId":23138,"corporation":false,"usgs":false,"family":"Cheng","given":"R.","email":"","middleInitial":"T.","affiliations":[],"preferred":false,"id":644658,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Burau, J.R. 0000-0002-5196-5035","orcid":"https://orcid.org/0000-0002-5196-5035","contributorId":7307,"corporation":false,"usgs":true,"family":"Burau","given":"J.R.","affiliations":[],"preferred":false,"id":644659,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Gartner, J. W.","contributorId":81903,"corporation":false,"usgs":false,"family":"Gartner","given":"J.","email":"","middleInitial":"W.","affiliations":[],"preferred":false,"id":644660,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70176684,"text":"70176684 - 1991 - Comment on “Flow and tracer transport in a single fracture: A stochastic model and its relation to some field observations” by L. Moreno et al.","interactions":[],"lastModifiedDate":"2018-02-27T11:54:49","indexId":"70176684","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":3722,"text":"Water Resources Research","onlineIssn":"1944-7973","printIssn":"0043-1397","active":true,"publicationSubtype":{"id":10}},"title":"Comment on “Flow and tracer transport in a single fracture: A stochastic model and its relation to some field observations” by L. Moreno et al.","docAbstract":"Moreno et al. [1988] (hereinafter referred to as MT) used a particle-tracking scheme to investigate the physics of solute movement in a variable-aperture planar fracture. The spatially heterogeneous fluid velocity was assumed to be the only mechanism of solute movement; local or pore scale dispersion and molecular diffusion were assumed to be negligible. The particle-tracking scheme used by MT consisted of routing particles from node to node in a finite difference grid. In this scheme, the direction of an individual particle is randomly selected and the probability associated with the particle movement in a given direction is proportional to the fluid flux in that direction. The same method was used by Desbarats [1990] to investigate advective transport in aquifers composed of two porous media of different hydraulic conductivities.
","language":"English","publisher":"American Geophysical Union","doi":"10.1029/90WR02310","usgsCitation":"Goode, D., and Shapiro, A.M., 1991, Comment on “Flow and tracer transport in a single fracture: A stochastic model and its relation to some field observations” by L. Moreno et al.: Water Resources Research, v. 27, no. 1, p. 129-131, https://doi.org/10.1029/90WR02310.","productDescription":"3 p.","startPage":"129","endPage":"131","costCenters":[{"id":532,"text":"Pennsylvania Water Science Center","active":true,"usgs":true}],"links":[{"id":480422,"rank":0,"type":{"id":40,"text":"Open Access Publisher Index Page"},"url":"https://doi.org/10.1029/90wr02310","text":"Publisher Index Page"},{"id":329005,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"27","issue":"1","noUsgsAuthors":false,"publicationDate":"2008-01-08","publicationStatus":"PW","scienceBaseUri":"57feb876e4b0824b2d155b11","contributors":{"authors":[{"text":"Goode, Daniel J. 0000-0002-8527-2456 djgoode@usgs.gov","orcid":"https://orcid.org/0000-0002-8527-2456","contributorId":2433,"corporation":false,"usgs":true,"family":"Goode","given":"Daniel J.","email":"djgoode@usgs.gov","affiliations":[{"id":532,"text":"Pennsylvania Water Science Center","active":true,"usgs":true}],"preferred":false,"id":649701,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Shapiro, Allen M. 0000-0002-6425-9607 ashapiro@usgs.gov","orcid":"https://orcid.org/0000-0002-6425-9607","contributorId":2164,"corporation":false,"usgs":true,"family":"Shapiro","given":"Allen","email":"ashapiro@usgs.gov","middleInitial":"M.","affiliations":[{"id":37277,"text":"WMA - Earth System Processes Division","active":true,"usgs":true},{"id":436,"text":"National Research Program - Eastern Branch","active":true,"usgs":true}],"preferred":true,"id":649702,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70016347,"text":"70016347 - 1991 - Observations constraining near-source ground motion estimated from locally recorded seismograms","interactions":[],"lastModifiedDate":"2024-04-30T23:32:48.322212","indexId":"70016347","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":"Observations constraining near-source ground motion estimated from locally recorded seismograms","docAbstract":"To estimate the seismic hazard to underground facilities or operations in the environs of a mining-induced tremor or a natural earthquake, it is useful to be able to relate locally recorded seismic waveforms to peak ground velocity and slip at the causative fault. For this purpose, far-field S wave pulses are analyzed to define the faulting slip D and near-fault peak ground velocity D/2 that give rise to the most significant ground motion. This most intense region of faulting, an assumed circular asperity, has radius r within a broader source zone of radius r0, which is traditionally calculated from the corner frequency of the S wave spectrum. In developing relationships between peak far-field velocity v and peak acceleration a, and the source processes of the asperity, D and D, as well as its radius r, the key model assumption is that r = kβ/ω, where ω is the angular frequency of the sinusoidal velocity pulse of maximum amplitude, β is the sheaf wave speed, and k is a constant. Observations in deep-level gold mines of fault slip and slip velocity as well as laboratory observations of slip rate as a function of stress drop for stick-slip failure support a choice of about k = 2.34, the value commonly used for estimating r0 using the Brune model. In particular, observations of fault slip up to 410 mm for mining-induced tremors in the moment magnitude range 4–5 are consistent with D = 8.1 Rv/β, where R is hypocentral distance. Moreover, estimates based on underground damage of near-fault ground velocities ranging up to 3.5 m/s are in accord with D/2 = 1.28(β/μ)ρRa, where μ is the modulus of rigidity and ρ is the density. Alternatively, the average slip velocity 〈D〉 can be expressed in terms of the stress drop Δσa of the asperity as 〈D〉 = 0.51 β Δσa/μ, and the agreement of this relationship with measurements made during stick-slip failure in the laboratory is good. To the extent that seismic slip exterior to the asperity is a consequence of preevent suppression of slip due to the asperity, the broader-scale(r0) slip can be related to that of the asperity. Just as the asperity radius r can be estimated from r = 2.34 βv/a, an alternative estimate for r0 is given by r0 = ρRaM0/[75.8ρμ(Rv)2], the results of which are generally in good agreement with estimates based on the spectral corner frequency method.
Basaltic rocks of the Cima volcanic field in the southern Basin and Range province contain abundant gabbro, pyroxenite, and peridotite xenoliths. Composite xenoliths containing two or more rock types show that upper-mantle spinel peridotite was enriched by multiple dike intrusions in at least three episodes; the mantle was further enriched by intergranular and shear-zone melt infiltration in at least two episodes. The oldest dikes, now metamorphosed, are Cr-diopside websterite. Dikes of intermediate age are most abundant at Cima and consist of igneous-textured websterite and two-pyroxene gabbro and microgabbro of tholeiitic or calcalkalic parentage. The youngest dikes are igneous-textured clinopyroxenite, gabbro, and olivine microgabbro of alkalic parentage. The dikes in peridotite are interpreted as parts of a system of conduits through which tholeiitic (or calcalkalic) and alkalic magmas fed lower-crustal intrusions, which are represented by abundant xenoliths of the same igneous rock types as observed in the dikes. Mineral assemblages of dikes in peridotite indicate that an enriched uppermost mantle zone no thicker than 15 km could have been sampled. Because of their high densities, the gabbros and pyroxenites can occupy the zone immediately above the present Moho (modeled on seismic data as 10-13 km thick, with Vp 6.8 km/s) only if their seismic velocities are reduced by the joints, partial melts, and fluid inclusions that occur in them. Alternatively, these xenoliths may have been derived entirely from beneath the Moho, in which case the Moho is not the local crust-mantle boundary.
","language":"English","publisher":"Oxford Academic","doi":"10.1093/petrology/32.1.169","issn":"00223530","usgsCitation":"Wilshire, H.G., McGuire, A.V., Noller, J., and Turrin, B.D., 1991, Petrology of lower crustal and upper mantle xenoliths from the Cima Volcanic Field, California: Journal of Petrology, v. 32, no. 1, p. 169-200, https://doi.org/10.1093/petrology/32.1.169.","productDescription":"32 p.","startPage":"169","endPage":"200","numberOfPages":"32","costCenters":[],"links":[{"id":224840,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"32","issue":"1","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a7834e4b0c8380cd78673","contributors":{"authors":[{"text":"Wilshire, H. G.","contributorId":36125,"corporation":false,"usgs":false,"family":"Wilshire","given":"H.","middleInitial":"G.","affiliations":[],"preferred":false,"id":374032,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"McGuire, A. V. 0000-0003-4646-0750 ffadm@usgs.gov","orcid":"https://orcid.org/0000-0003-4646-0750","contributorId":50928,"corporation":false,"usgs":false,"family":"McGuire","given":"A.","email":"ffadm@usgs.gov","middleInitial":"V.","affiliations":[],"preferred":false,"id":374034,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Noller, J.S.","contributorId":49837,"corporation":false,"usgs":true,"family":"Noller","given":"J.S.","affiliations":[],"preferred":false,"id":374033,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Turrin, B. D.","contributorId":32548,"corporation":false,"usgs":true,"family":"Turrin","given":"B.","middleInitial":"D.","affiliations":[],"preferred":false,"id":374031,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70197521,"text":"70197521 - 1991 - Neogene rotations and quasicontinuous deformation of the Pacific Northwest continental margin","interactions":[],"lastModifiedDate":"2018-06-08T16:00:22","indexId":"70197521","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1796,"text":"Geology","active":true,"publicationSubtype":{"id":10}},"title":"Neogene rotations and quasicontinuous deformation of the Pacific Northwest continental margin","docAbstract":"Paleomagnetically determined rotations about vertical axes of 15 to 12 Ma flows of the Miocene Columbia River Basalt Group of Oregon and Washington decrease smoothly with distance from the plate margin, consistent with a simple physical model for continental deformation that assumes the lithosphere behaves as a thin layer of fluid. The average rate of northward translation of the continental margin since 15 Ma calculated from the rotations, using this model, is about 15 mm/yr, which suggests that much of the tangential motion between the Juan de Fuca and North American plates since middle Miocene time has been taken up by deformation of North America. The fluid-like character of the large-scale deformation implies that the brittle upper crust follows the motions of the deeper parts of the lithosphere.
","language":"English","publisher":"Geological Survey of America","doi":"10.1130/0091-7613(1991)019<0978:NRAQDO>2.3.CO;2","usgsCitation":"England, P., and Wells, R., 1991, Neogene rotations and quasicontinuous deformation of the Pacific Northwest continental margin: Geology, v. 19, no. 10, p. 978-981, https://doi.org/10.1130/0091-7613(1991)019<0978:NRAQDO>2.3.CO;2.","productDescription":"4 p.","startPage":"978","endPage":"981","costCenters":[{"id":312,"text":"Geology, Minerals, Energy, and Geophysics Science Center","active":true,"usgs":true}],"links":[{"id":354867,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"19","issue":"10","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"5c112478e4b034bf6a81dfb4","contributors":{"authors":[{"text":"England, Philip","contributorId":205498,"corporation":false,"usgs":false,"family":"England","given":"Philip","email":"","affiliations":[],"preferred":false,"id":737536,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Wells, Ray E. 0000-0002-7796-0160 rwells@usgs.gov","orcid":"https://orcid.org/0000-0002-7796-0160","contributorId":2692,"corporation":false,"usgs":true,"family":"Wells","given":"Ray E.","email":"rwells@usgs.gov","affiliations":[{"id":312,"text":"Geology, Minerals, Energy, and Geophysics Science Center","active":true,"usgs":true}],"preferred":false,"id":737537,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70014976,"text":"70014976 - 1991 - Large-scale distribution of metal contamination in the fine-grained sediments of the Clark Fork River, Montana, U.S.A.","interactions":[],"lastModifiedDate":"2023-02-15T12:16:58.288062","indexId":"70014976","displayToPublicDate":"1991-01-01T00:00:00","publicationYear":"1991","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":835,"text":"Applied Geochemistry","active":true,"publicationSubtype":{"id":10}},"title":"Large-scale distribution of metal contamination in the fine-grained sediments of the Clark Fork River, Montana, U.S.A.","docAbstract":"Historic discharges from the mining and smelting complex at the head-waters of the Clark Fork River have resulted in elevated Ag, Cd, Cu, Pb and Zn concentrations in the <60 μm fraction of both bed and flood-plain sediments of the river. Processes affecting the trends in longitudinal distributions of these metals were investigated by repeated sampling over a 380 km river reach between August 1986 and July 1989. At the most upstream site, bed-sediment metal concentrations were enriched 18–115 times above least enriched tributaries, depending on the metal. All metals decreased exponentially with distance downstream away from mining. The exponential model predicts that elevated metal concentrations should occur over 550 km downstream, in Lake Pend Oreille. Longitudinal trends, obvious on a scale of hundreds of kilometers, were obscured by small-scale spatial variability when shorter stretches of the river were considered. Longitudinal dispersion appeared to be controlled largely by physical dilution with less-contaminated sediments.
Evidence suggests that erosion of contaminated flood-plains contributes to metal contamination in the bed sediments. Tributary input appeared to have little influence on the large-scale, downstream distribution of metals; however, it did contribute to local variability in bed-sediment metal concentrations. Association of metals with specific mineral grains, as well as variability in total organic C and Fe concentration, appeared also to contribute to variability.
Some year-to-year variability in bed-sediment metal concentrations was observed, however, trends in longitudinal dispersion were not significantly different between at least two of the years sampled.
","language":"English","publisher":"Elsevier","doi":"10.1016/0883-2927(91)90064-V","issn":"08832927","usgsCitation":"Axtmann, E., and Luoma, S., 1991, Large-scale distribution of metal contamination in the fine-grained sediments of the Clark Fork River, Montana, U.S.A.: Applied Geochemistry, v. 6, no. 1, p. 75-88, https://doi.org/10.1016/0883-2927(91)90064-V.","productDescription":"14 p.","startPage":"75","endPage":"88","numberOfPages":"14","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":223905,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"country":"United 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\"}}]}","volume":"6","issue":"1","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a4495e4b0c8380cd66c16","contributors":{"authors":[{"text":"Axtmann, E.V.","contributorId":30652,"corporation":false,"usgs":true,"family":"Axtmann","given":"E.V.","email":"","affiliations":[],"preferred":false,"id":369756,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Luoma, S. N.","contributorId":86353,"corporation":false,"usgs":true,"family":"Luoma","given":"S. N.","affiliations":[],"preferred":false,"id":369757,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70014973,"text":"70014973 - 1991 - Magnetic susceptibility and relation to initial 87Sr/86Sr for granitoids of the central Sierra Nevada, California","interactions":[],"lastModifiedDate":"2024-05-02T00:07:54.706781","indexId":"70014973","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":"Magnetic susceptibility and relation to initial 87Sr/86Sr for granitoids of the central Sierra Nevada, California","docAbstract":"Measurement of the magnetic susceptibility of more than 6000 samples of granitic rock from the Mariposa 1° by 2° quadrangle, which crosses the central part of the Sierra Nevada batholith between 37° and 38°N latitude, shows that magnetic susceptibility values are above 10−2 SI units in the east and central parts of the batholith and drop abruptly to less than 10−3 SI units in the western foothills. In a narrow transitional zone, intermediate values (10−3 to 10−2) prevail. Magnetic susceptibility appears to decrease slightly westward within the zones of both high and low values. Magnetic susceptibility in plutonic rocks is chiefly a function of the abundance of magnetite, which depends, in turn, on the total iron content of the rocks and their oxidation ratio. Lower magnetic susceptibilities of felsic members of Sierran intrusive suites and of some felsic rock units relative to adjacent mafic rock units commonly reflect differences in total iron content, but the differences of magnetic susceptibility that define the regional pattern generally are much larger and are determined chiefly by the oxidation ratios of the rocks. The relatively unaltered condition of the samples and restriction of δ18O to the range of +7 to +10.3‰ indicate that neither hydrothermal fluids nor subsolidus alteration were important in modifying oxidation ratios. Correlations of magnetic susceptibility with initial 87Sr/86Sr suggest that oxidation ratios have been inherited from the source regions for the magmas from which the rocks crystallized. Reduction of Fe3+ to Fe2+ by organic carbon or other reducing substances may also have affected magnetic susceptibility.
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":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.
Integrated geologic, geochemical, fluid-inclusion, and stableisotope studies of the gold deposits in the Jerritt Canyon district, Nevada, provide evidence that gold deposition was a consequence of both fluid mixing and sulfidization of host-rock iron. Chemical-reaction-path models of these ore-depositional processes confirm that the combination of fluid mixing, including simultaneous cooling, dilution, and oxidation of the ore fluid, and wall-rock reaction, with sulfidization of reactive iron in the host rock, explains the disseminated nature and small size of the gold and the alteration zonation, mineralogy, and geochemistry observed at Jerritt Canyon and at many other sediment-hosted disseminated gold deposits.
The Priestley-Taylor equation, a simplification of the Penman equation, was used to allow calculations of evapotranspiration under conditions where soil water supply limits evapotranspiration. The Priestley-Taylor coefficient, α, was calculated to incorporate an exponential decrease in evapotranspiration as soil water content decreases. The method is appropriate for use when detailed meteorological measurements are not available. The data required to determine the parameter for the α coefficient are net radiation, soil heat flux, average air temperature, and soil water content. These values can be obtained from measurements or models.
The dataset used in this report pertains to a partially vegetated clearcut forest site in southwest Oregon with soil depths ranging from 0.48 to 0.70 m and weathered bedrock below that. Evapotranspiration was estimated using the Bowen ratio method, and the calculated Priestley-Taylor coefficient was fitted to these estimates by nonlinear regression. The calculated Priestley-Taylor coefficient (α′) was found to be approximately 0.9 when the soil was near field capacity (0.225 cm3 cm−3). It was not until soil water content was less than 0.14 cm3 cm−3 that soil water supply limited evapotranspiration. The soil reached a final residual water content near 0.05 cm3 cm−3 at the end of the growing season.
","language":"English","publisher":"Elsevier","doi":"10.1016/0168-1923(91)90094-7","issn":"01681923","usgsCitation":"Flint, A.L., and Childs, S., 1991, Use of the Priestley-Taylor evaporation equation for soil water limited conditions in a small forest clearcut: Agricultural and Forest Meteorology, v. 56, no. 3-4, p. 247-260, https://doi.org/10.1016/0168-1923(91)90094-7.","productDescription":"14 p.","startPage":"247","endPage":"260","costCenters":[{"id":154,"text":"California Water Science Center","active":true,"usgs":true}],"links":[{"id":222856,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"56","issue":"3-4","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505bbf9be4b08c986b329c64","contributors":{"authors":[{"text":"Flint, Alan L. 0000-0002-5118-751X aflint@usgs.gov","orcid":"https://orcid.org/0000-0002-5118-751X","contributorId":1492,"corporation":false,"usgs":true,"family":"Flint","given":"Alan","email":"aflint@usgs.gov","middleInitial":"L.","affiliations":[{"id":154,"text":"California Water Science Center","active":true,"usgs":true},{"id":657,"text":"Western Geographic Science Center","active":true,"usgs":true}],"preferred":true,"id":373856,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Childs, S.W.","contributorId":26449,"corporation":false,"usgs":true,"family":"Childs","given":"S.W.","email":"","affiliations":[],"preferred":false,"id":373855,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70016538,"text":"70016538 - 1991 - Seismicity and detection/location threshold in the southern Great Basin seismic network","interactions":[],"lastModifiedDate":"2024-04-26T11:30:11.373037","indexId":"70016538","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":"Seismicity and detection/location threshold in the southern Great Basin seismic network","docAbstract":"A spatially varying model of the detection/location capabilities of the Southern Great Basin seismic network (SGBSN) has been derived that is based on simple empirical relations and statistics. This permits use of almost all the catalog data gathered; instead of ignoring data that are below the threshold of completeness, a spatially varying threshold model is developed so that subregions having lower completeness levels than the network as a whole can be outlined and the completeness level of each sub-region determined. Such a model is required to unambiguously identify regions that are aseismic due to natural processes rather than to limited detection and/or location capabilities. Accounting for spatial variations in detection/location threshold is also important for studies in which magnitude-frequency distributions are interpreted in terms of source scaling properties. The characteristics of the spatial distribution of earthquakes, where earthquake clusters and aseismic regions locate, appear to be stable at all magnitude levels so that inferences about where strain is being accommodated will be the same whether numbers of earthquakes or strain estimated from seismic moments are examined. For the southern Great Basin region these principal characteristics include clusters at the northern end of the Furnace Creek fault and in the Pahranagat Shear Zone, and a relatively large number of earthquakes in the northern and southeastern portions of the Nevada Test Site. These clusters cover regions much larger than the surface projections of any of the mapped faults. The extent to which seismicity is induced by nuclear testing is unclear. The predominantly aseismic regions include the area west of the Death Valley/Furnace Creek fault system and an almost complete absence of events at Yucca Mountain. Finally, a considerable number of isolated events in the SGBSN catalog cannot be correlated with mapped faults.
From a large collection of Jurassic continental tholeiites cropping out in Europe and Africa, we selected 90 samples for paleointensity determinations. The samples were carefully selected to avoid any secondary magnetizations, especially viscous magnetization. Use of the Thellier method reveals that magnetic property changes due to heating begin often at quite low temperatures but fortunately without modifying noticeably their natural remanent magnetization-thermoremanent magnetization ratio. Twenty-eight well-clustered paleointensity estimates were obtained from two European dikes that were emplaced during Early Jurassic time: the Kerforne dike at Brenterc'h in Brittany (northwestern France) and the Messejana dike on the Iberian Peninsula (Spain and Portugal). Virtual dipole moments calculated from both magmatic units are similar and only about one-third of present-day values. These new data lend support to the recently postulated low dipole moment of the Mesozoic geomagnetic field.
We present a new compilation of the structural and stratigraphic evolution of the Tharsis region of Mars that incorporates recent advances in understanding its stratigraphy, and we introduce a lithospheric deformation model that can account for the observations. The first period in the formation of Tharsis occurred in Late Noachian/Early Hesperian time with the deposition of volcanic plains materials throughout the surrounding highlands (e.g., Lunae Planum) and on the Tharsis rise (which includes the giant volcanoes and surrounding, elevated lava fields). Extensive radial normal faulting occurred on the rise, locally extending outward at Valles Marineris and Tempe Terra, and concentric wrinkle ridges formed along the edge of the rise. This regional deformation appears to have been modulated by a global compressional stress field due to rapid planetary cooling and contraction. The second period occurred during the Late Hesperian/Amazonian with Tharsis volcanism centered on the rise and radial extensional deformation that extended from the center of the rise for thousands of kilometers. We propose a model in which the lithosphere beneath Tharsis consists of a thin elastic crustal cap on the rise that is mechanically detached from the strong upper mantle by a volcanically thickened, hot, weak lower crust. These layers merge into a single cooler, strong lithospheric layer around the edges of the rise. This model is capable of generating large extensional hoop stresses throughout much of the western hemisphere, in agreement with observations. The tectonic interpretation of the stresses predicted by this model requires the reconciliation of extensional strain within narrow grabens and compressional strain within wrinkle ridges with (1) processes in the deeper lithosphere, (2) the sparsity of strike-slip faults, and (3) other global or locally important stress fields. Stresses predicted by global models affect the entire thickness of the lithosphere, and they can be reconciled with narrow, closely spaced grabens that accommodate large amounts of extensional strain in the upper few kilometers of the lithosphere if the grabens are underlain and kinematically linked with dikes or other tension cracks, such as hydrofractures. Deeper levels of the lithosphere can accommodate this strain by elastic expansion if grabens are spaced far apart (many tens to hundreds of kilometers). Mechanical considerations suggest that deformation on faults beneath wrinkle ridges could extend through a significant thickness of the brittle crust. A number of factors, including stresses generated by the addition of overburden, intrusion of dikes, weakness of geologic materials under extension, and the laterally constrained nature of a single lithospheric plate, may have inhibited the formation of strike-slip faults on Mars. Stresses generated from the removal of overburden could have augmented planetwide wrinkle ridge formation during the Late Noachian/Early Hesperian and in Kasei Valles and western Chryse Planitia during the Early Amazonian. The nonuniform distribution of tectonic features around Tharsis can be understood in terms of the concentration of regional stresses and strain near weaker volcanotectonic centers.