Laboratory experiments employing radiotracer methodology were conducted to determine the assimilation efficiencies from ingested natural seston, the influx rates from the dissolved phase and the efflux rates of 6 trace elements (Ag, Am, Cd, Co, Se and Zn) in the mussel Mytilus edulis. A kinetic model was then employed to predict trace element concentration in mussel tissues in 2 locations for which mussel and environmental data are well described: South San Francisco Bay (California, USA) and Long Island Sound (New York, USA). Assimilation efficiencies from natural seston ranged from 5 to 18% for Ag, 0.6 to 1% for Am, 8 to 20% for Cd, 12 to 16% for Co, 28 to 34% for Se, and 32 to 41% for Zn. Differences in chlorophyll a concentration in ingested natural seston did not have significant impact on the assimilation of Am, Co, Se and Zn. The influx rate of elements from the dissolved phase increased with the dissolved concentration, conforming to Freundlich adsorption isotherms. The calculated dissolved uptake rate constant was greatest for Ag, followed by Zn > Am = Cd > Co > Se. The estimated absorption efficiency from the dissolved phase was 1.53% for Ag, 0.34% for Am, 0.31% for Cd, 0.11% for Co, 0.03% for Se and 0.89% for Zn. Salinity had an inverse effect on the influx rate from the dissolved phase and dissolved organic carbon concentration had no significant effect on trace element uptake. The calculated efflux rate constants for all elements ranged from 1.0 to 3.0% d-1. The route of trace element uptake (food vs dissolved) and the duration of exposure to dissolved trace elements (12 h vs 6 d) did not significantly influence trace element efflux rates. A model which used the experimentally determined influx and efflux rates for each of the trace elements, following exposure from ingested food and from water, predicted concentrations of Ag, Cd, Se and Zn in mussels that were directly comparable to actual tissue concentrations independently measured in the 2 reference sites in national monitoring programs. Sensitivity analysis indicated that the total suspended solids load, which can affect mussel feeding activity, assimilation, and trace element concentration in the dissolved and particulate phases, can significantly influence metal bioaccumulation for particle-reactive elements such as Ag and Am. For all metals, concentrations in mussels are proportionately related to total metal load in the water column and their assimilation efficiency from ingested particles. Further, the model predicted that over 96% of Se in mussels is obtained from ingested food, under conditions typical of coastal waters. For Ag, Am, Cd, Co and Zn, the relative contribution from the dissolved phase decreases significantly with increasing trace element partition coefficients for suspended particles and the assimilation efficiency in mussels of ingested trace elements; values range between 33 and 67% for Ag, 5 and 17% for Am, 47 and 82% for Cd, 4 and 30% for Co, and 17 and 51% for Zn.
","language":"English","publisher":"Inter-Research","doi":"10.3354/meps140091","issn":"01718630","usgsCitation":"Wang, W., Fisher, N., and Luoma, S., 1996, Kinetic determinations of trace element bioaccumulation in the mussel Mytilus edulis: Marine Ecology Progress Series, v. 140, no. 1-3, p. 91-113, https://doi.org/10.3354/meps140091.","productDescription":"23 p.","startPage":"91","endPage":"113","onlineOnly":"N","additionalOnlineFiles":"N","costCenters":[{"id":552,"text":"San Francisco Bay-Delta","active":false,"usgs":true},{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true},{"id":5079,"text":"Pacific Regional Director's Office","active":true,"usgs":true}],"links":[{"id":479129,"rank":1,"type":{"id":40,"text":"Open Access Publisher Index Page"},"url":"https://doi.org/10.3354/meps140091","text":"Publisher Index Page"},{"id":227586,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":265991,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.3354/meps140091"}],"volume":"140","issue":"1-3","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a40a5e4b0c8380cd64f19","contributors":{"authors":[{"text":"Wang, W.-X.","contributorId":90477,"corporation":false,"usgs":true,"family":"Wang","given":"W.-X.","email":"","affiliations":[],"preferred":false,"id":378614,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Fisher, N.S.","contributorId":67668,"corporation":false,"usgs":true,"family":"Fisher","given":"N.S.","email":"","affiliations":[],"preferred":false,"id":378612,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Luoma, S. N.","contributorId":86353,"corporation":false,"usgs":true,"family":"Luoma","given":"S. N.","affiliations":[],"preferred":false,"id":378613,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70018164,"text":"70018164 - 1996 - Chronology for fluctuations in late Pleistocene Sierra Nevada glaciers and lakes","interactions":[],"lastModifiedDate":"2012-03-12T17:19:27","indexId":"70018164","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":3338,"text":"Science","active":true,"publicationSubtype":{"id":10}},"title":"Chronology for fluctuations in late Pleistocene Sierra Nevada glaciers and lakes","docAbstract":"Mountain glaciers, because of their small size, are usually close to equilibrium with the local climate and thus should provide a test of whether temperature oscillations in Greenland late in the last glacial period are part of global-scale climate variability or are restricted to the North Atlantic region. Correlation of cosmogenic chlorine-36 dates on Sierra Nevada moraines with a continuous radiocarbon-dated sediment record from nearby Owens Lake shows that Sierra Nevada glacial advances were associated with Heinrich events 5, 3, 2, and 1.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Science","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1126/science.274.5288.749","issn":"00368075","usgsCitation":"Phillips, F.M., Zreda, M., Benson, L.V., Plummer, M., Elmore, D., and Sharma, P., 1996, Chronology for fluctuations in late Pleistocene Sierra Nevada glaciers and lakes: Science, v. 274, no. 5288, p. 749-751, https://doi.org/10.1126/science.274.5288.749.","startPage":"749","endPage":"751","numberOfPages":"3","costCenters":[],"links":[{"id":227455,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":205923,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1126/science.274.5288.749"}],"volume":"274","issue":"5288","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"5059f5f5e4b0c8380cd4c4f8","contributors":{"authors":[{"text":"Phillips, F. M.","contributorId":24493,"corporation":false,"usgs":true,"family":"Phillips","given":"F.","email":"","middleInitial":"M.","affiliations":[],"preferred":false,"id":378735,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Zreda, M.G.","contributorId":64393,"corporation":false,"usgs":true,"family":"Zreda","given":"M.G.","email":"","affiliations":[],"preferred":false,"id":378737,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Benson, L. V.","contributorId":50159,"corporation":false,"usgs":true,"family":"Benson","given":"L.","email":"","middleInitial":"V.","affiliations":[],"preferred":false,"id":378736,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Plummer, M.A.","contributorId":80025,"corporation":false,"usgs":true,"family":"Plummer","given":"M.A.","email":"","affiliations":[],"preferred":false,"id":378738,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Elmore, D.","contributorId":83268,"corporation":false,"usgs":true,"family":"Elmore","given":"D.","email":"","affiliations":[],"preferred":false,"id":378739,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Sharma, Prakash","contributorId":107435,"corporation":false,"usgs":true,"family":"Sharma","given":"Prakash","email":"","affiliations":[],"preferred":false,"id":378740,"contributorType":{"id":1,"text":"Authors"},"rank":6}]}} ,{"id":70018505,"text":"70018505 - 1996 - Testing and validating environmental models","interactions":[],"lastModifiedDate":"2012-03-12T17:19:25","indexId":"70018505","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":3352,"text":"Science of the Total Environment","active":true,"publicationSubtype":{"id":10}},"title":"Testing and validating environmental models","docAbstract":"Generally accepted standards for testing and validating ecosystem models would benefit both modellers and model users. Universally applicable test procedures are difficult to prescribe, given the diversity of modelling approaches and the many uses for models. However, the generally accepted scientific principles of documentation and disclosure provide a useful framework for devising general standards for model evaluation. Adequately documenting model tests requires explicit performance criteria, and explicit benchmarks against which model performance is compared. A model's validity, reliability, and accuracy can be most meaningfully judged by explicit comparison against the available alternatives. In contrast, current practice is often characterized by vague, subjective claims that model predictions show 'acceptable' agreement with data; such claims provide little basis for choosing among alternative models. Strict model tests (those that invalid models are unlikely to pass) are the only ones capable of convincing rational skeptics that a model is probably valid. However, 'false positive' rates as low as 10% can substantially erode the power of validation tests, making them insufficiently strict to convince rational skeptics. Validation tests are often undermined by excessive parameter calibration and overuse of ad hoc model features. Tests are often also divorced from the conditions under which a model will be used, particularly when it is designed to forecast beyond the range of historical experience. In such situations, data from laboratory and field manipulation experiments can provide particularly effective tests, because one can create experimental conditions quite different from historical data, and because experimental data can provide a more precisely defined 'target' for the model to hit. We present a simple demonstration showing that the two most common methods for comparing model predictions to environmental time series (plotting model time series against data time series, and plotting predicted versus observed values) have little diagnostic power. We propose that it may be more useful to statistically extract the relationships of primary interest from the time series, and test the model directly against them.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Science of the Total Environment","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1016/0048-9697(95)04971-1","issn":"00489697","usgsCitation":"Kirchner, J., Hooper, R.P., Kendall, C., Neal, C., and Leavesley, G., 1996, Testing and validating environmental models: Science of the Total Environment, v. 183, no. 1-2, p. 33-47, https://doi.org/10.1016/0048-9697(95)04971-1.","startPage":"33","endPage":"47","numberOfPages":"15","costCenters":[],"links":[{"id":205884,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1016/0048-9697(95)04971-1"},{"id":227301,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"183","issue":"1-2","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505ba5bfe4b08c986b320c4c","contributors":{"authors":[{"text":"Kirchner, J.W.","contributorId":45846,"corporation":false,"usgs":true,"family":"Kirchner","given":"J.W.","email":"","affiliations":[],"preferred":false,"id":379853,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Hooper, R. P.","contributorId":26321,"corporation":false,"usgs":true,"family":"Hooper","given":"R.","email":"","middleInitial":"P.","affiliations":[],"preferred":false,"id":379851,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Kendall, C. 0000-0002-0247-3405","orcid":"https://orcid.org/0000-0002-0247-3405","contributorId":35050,"corporation":false,"usgs":true,"family":"Kendall","given":"C.","affiliations":[],"preferred":false,"id":379852,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Neal, C.","contributorId":89269,"corporation":false,"usgs":true,"family":"Neal","given":"C.","email":"","affiliations":[],"preferred":false,"id":379854,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Leavesley, G.","contributorId":90483,"corporation":false,"usgs":true,"family":"Leavesley","given":"G.","email":"","affiliations":[],"preferred":false,"id":379855,"contributorType":{"id":1,"text":"Authors"},"rank":5}]}} ,{"id":70018206,"text":"70018206 - 1996 - Reduction of aqueous transition metal species on the surfaces of Fe(II)-containing oxides","interactions":[],"lastModifiedDate":"2019-02-14T07:22:03","indexId":"70018206","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","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":"Reduction of aqueous transition metal species on the surfaces of Fe(II)-containing oxides","docAbstract":"Experimental studies demonstrate that structural Fe(II) in magnetite and ilmenite heterogeneously reduce aqueous ferric, cupric, vanadate, and chromate ions at the oxide surfaces over a pH range of 1–7 at 25°C. For an aqueous transition metal m, such reactions are
and
where z is the valance state and n is the charge transfer number. The half cell potential range for solid state oxidation [Fe(II)] → [Fe(III)] is −0.34 to −0.65 V, making structural Fe(II) a stronger reducing agent than aqueous Fe2+ (−0.77 V). Reduction rates for aqueous metal species are linear with time (up to 36 h), decrease with pH, and have rate constants between 0.1 and 3.3 × 10−10 mol m−2s−1. Iron is released to solution both from the above reactions and from dissolution of the oxide surface. In the presence of chromate, Fe2+ is oxidized homogeneously in solution to Fe3+.
X-ray photoelectron spectroscopy (XPS) denotes a Fe(III) oxide surface containing reduced Cr(III) and V(IV) species. Magnetite and ilmenite electrode potentials are insensitive to increases in divalent transition metals including Zn(II), Co(II), Mn(II), and Ni(II) and reduced V(IV) and Cr(III) but exhibit a log-linear concentration-potential response to Fe(III) and Cu(II). Complex positive electrode responses occur with increasing Cr(VI) and V(V) concentrations. Potential dynamic scans indicate that the high oxidation potential of dichromate is capable of suppressing the cathodic reductive dissolution of magnetite. Oxide electrode potentials are determined by the Fe(II)/Fe(III) composition of the oxide surface and respond to aqueous ion potentials which accelerate this oxidation process.
Natural magnetite sands weathered under anoxic conditions are electrochemically reactive as demonstrated by rapid chromate reduction and the release of aqueous Fe(III) to experimental solution. In contrast, magnetite weathered under oxidizing vadose conditions show minimum reactivity toward chromate ions. The ability of Fe(II) oxides to reduce transition metals in soils and groundwaters will be strongly dependent on the redox environment.
","language":"English","publisher":"Elsevier","doi":"10.1016/0016-7037(96)00213-X","issn":"00167037","usgsCitation":"White, A.F., and Peterson, M.L., 1996, Reduction of aqueous transition metal species on the surfaces of Fe(II)-containing oxides: Geochimica et Cosmochimica Acta, v. 60, no. 20, p. 3799-3814, https://doi.org/10.1016/0016-7037(96)00213-X.","productDescription":"16 p.","startPage":"3799","endPage":"3814","costCenters":[{"id":589,"text":"Toxic Substances Hydrology Program","active":true,"usgs":true}],"links":[{"id":227456,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":205924,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1016/0016-7037(96)00213-X"}],"volume":"60","issue":"20","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"50e4a3d9e4b0e8fec6cdb9d6","contributors":{"authors":[{"text":"White, A. F.","contributorId":36546,"corporation":false,"usgs":true,"family":"White","given":"A.","email":"","middleInitial":"F.","affiliations":[],"preferred":false,"id":378873,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Peterson, M. L.","contributorId":49930,"corporation":false,"usgs":false,"family":"Peterson","given":"M.","email":"","middleInitial":"L.","affiliations":[],"preferred":false,"id":378874,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70017682,"text":"70017682 - 1996 - Loess stratigraphy of the Lower Mississippi Valley","interactions":[],"lastModifiedDate":"2023-12-16T13:31:52.283109","indexId":"70017682","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1517,"text":"Engineering Geology","active":true,"publicationSubtype":{"id":10}},"title":"Loess stratigraphy of the Lower Mississippi Valley","docAbstract":"Loesses of the Lower Mississippi Valley (LMV) are world-famous. Sir Charles Lyell (1847), Hilgard (1860), Stafford (1869), Call (1891) and Mabry (1898), thought the LMV loess was a single water deposit although \"double submergence\" was noted by Call (1891) and Salisbury (1891). Shimek (1902) and Emerson (1918) recognized LMV loess as a wind deposit which came from the valley. Although wind-deposited loess gained wide acceptance, Russell (1944a) published his controversial theory of \"loessification\" which entailed weathering of backswamp deposits, downslope movement and recharge by carbonates to form loess. Wascher et al. (1947) identified three LMV loesses, mapped distributions and strongly supported eolian deposition. Leighton and Willman (1950), identified four loesses and supported eolian deposition as did Krinitzsky and Turnbull (1967) and Snowden and Priddy (1968), but Krinitzsky and Turnbull questioned the deepest loess. Daniels and Young (1968) and Touchet and Daniels (1970) studied the distribution of loesses in south-central Louisiana. West et al. (1980) and Rutledge et al. (1985) studied the source areas and wind directions which deposited the loesses on and adjoining Crowley's Ridge. B.J. Miller and co-workers (Miller et al., 1985, 1986, Miller and Alford, 1985) proposed that the Loveland Silt was Early Wisconsin rather than Illinoian age and advanced the name Sicily Island loess. They proposed the underlying loess was Illinoian and advanced the name Crowley's Ridge. We termed the loesses, from the surface downward, Peoria Loess, Roxana Silt, Loveland/Sicily Island loess, Crowley's Ridge Loess and Marianna loess. Researchers agree that the surfical Peoria Loess is Late Wisconsin and the Roxana Silt is Late to Middle Wisconsin, but little agreement exists on the age of the older loesses. Pye and Johnson (1988) proposed Early Wisconsin for the Loveland/Sicily Island. McKay and Follmer (1985) suggested this loess correlated with a loess under Illinoian till. Clark et al. (1989) agreed on Crowley's Ridge, but suggested the Loveland/Sicily Island loess on Sicily Island was older. Mirecki and Miller (1994) and Millard and Maat (1994) suggested an Illinoian age for the Loveland/Sicily Island loess. Miller and co-workers suggested, as did Pye and Johnson (1988), an Illinoian age for the Crowley's Ridge loess. McKay and Follmer (1985) suggested it correlated with a loess under \"Kansan\" till. Stratigraphy indicates the Marianna is the older of the five loesses. Researchers identified loess on both the east and west side of the LMV as well as on higher terraces within the valley. Many researchers assumed unaltered loesses were commonly yellowish brown, and silts or silt loams (West et al., 1980; Miller et al., 1986). The nonclay fraction of unweathered LMV loesses was dominated by quartz followed by carbonates, mainly dolomites, followed by feldspars, and micas. Clays were dominated by montmorillonite followed by micaceous minerals, kaolinite and vermiculite (Miller et al., 1986). Soils in the Crowley's Ridge loess are most developed, followed by the soils in the Loveland/Sicily Island which are more developed than the modern soils in the Peoria Loess. Soils in the Roxana and Marianna loesses are least developed and the Farmdale Soil of the Roxana is the weaker of the two (Miller et al., 1986). There is certainly overlapping range in the degree of soil development in the various loesses.","language":"English","publisher":"Elsevier","doi":"10.1016/S0013-7952(96)00012-9","issn":"00137952","usgsCitation":"Rutledge, E., Guccione, M.J., Markewich, H.W., Wysocki, D., and Ward, L., 1996, Loess stratigraphy of the Lower Mississippi Valley: Engineering Geology, v. 45, no. 1-4, p. 167-183, https://doi.org/10.1016/S0013-7952(96)00012-9.","productDescription":"17 p.","startPage":"167","endPage":"183","numberOfPages":"17","costCenters":[],"links":[{"id":228767,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"country":"United States","geographicExtents":"{\n \"type\": \"FeatureCollection\",\n \"features\": [\n {\n \"type\": \"Feature\",\n \"properties\": {},\n \"geometry\": {\n \"coordinates\": [\n [\n [\n -92.02102543648246,\n 37.9878733964605\n ],\n [\n -92.02102543648246,\n 29.066182142377983\n ],\n [\n -88.24172856148272,\n 29.066182142377983\n ],\n [\n -88.24172856148272,\n 37.9878733964605\n ],\n [\n -92.02102543648246,\n 37.9878733964605\n ]\n ]\n ],\n \"type\": \"Polygon\"\n }\n }\n ]\n}","volume":"45","issue":"1-4","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a493de4b0c8380cd6844f","contributors":{"authors":[{"text":"Rutledge, E.M.","contributorId":47819,"corporation":false,"usgs":true,"family":"Rutledge","given":"E.M.","email":"","affiliations":[],"preferred":false,"id":377256,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Guccione, Margaret J.","contributorId":24935,"corporation":false,"usgs":false,"family":"Guccione","given":"Margaret","email":"","middleInitial":"J.","affiliations":[],"preferred":false,"id":377254,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Markewich, H. W.","contributorId":31426,"corporation":false,"usgs":true,"family":"Markewich","given":"H.","email":"","middleInitial":"W.","affiliations":[],"preferred":false,"id":377255,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Wysocki, D.A.","contributorId":11678,"corporation":false,"usgs":true,"family":"Wysocki","given":"D.A.","email":"","affiliations":[],"preferred":false,"id":377253,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Ward, L.B.","contributorId":97942,"corporation":false,"usgs":true,"family":"Ward","given":"L.B.","email":"","affiliations":[],"preferred":false,"id":377257,"contributorType":{"id":1,"text":"Authors"},"rank":5}]}} ,{"id":70018999,"text":"70018999 - 1996 - Late Cretaceous remagnetization of Proterozoic mafic dikes, southern Highland Mountains, southwestern Montana: A paleomagnetic and 40Ar/39Ar study","interactions":[],"lastModifiedDate":"2023-12-22T12:12:41.025052","indexId":"70018999","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1786,"text":"Geological Society of America Bulletin","active":true,"publicationSubtype":{"id":10}},"title":"Late Cretaceous remagnetization of Proterozoic mafic dikes, southern Highland Mountains, southwestern Montana: A paleomagnetic and 40Ar/39Ar study","docAbstract":"Paleomagnetic results from Early Proterozoic metabasite sills and Middle Proterozoic diabase dikes from the southern Highland Mountains of southwestern Montana give well-defined, dual-polarity magnetizations that are statistically identical to those from a small Late Cretaceous pluton that cuts the dikes. The concordance of paleomagnetic directions from rocks of three widely separated ages indicates that the Proterozoic rocks were remagnetized, probably during Late Cretaceous time. Paleomagnetic, rock magnetic, and petrographic observations from the metabasite and diabase samples indicate that remanence is carried primarily by low-Ti magnetite. Combining virtual geomagnetic poles from metabasite sills, diabase dikes, and the Late Cretaceous pluton, we obtain a paleomagnetic pole at 85.5°N, 310.7°E (K = 19.9, A95 = 9.1°, N = 14 sites) that is similar to a reference pole from the 74 Ma Adel Mountain Volcanics of western Montana. Biotite and hornblende 40Ar/39Ar isotopic dates from host basement gneiss and a hornblende from a remagnetized metabasite sill yield ages of ca. 1800 Ma; these dates probably record cooling of the southern Highland Mountains following high-grade metamorphism at 1.9–1.8 Ga. The gneiss and metabasite age spectra show virtually no evidence of disturbance, indicating that the basement rocks were never heated to temperatures sufficient to cause even partial resetting of their argon systems. Thus, the overprint magnetization of the Highland Mountains rocks is not a thermoremanent magnetization acquired during conductive cooling of nearby Late Cretaceous plutons. Remagnetization of the metabasite sills and diabase dikes was probably caused by localized thermochemical and thermoviscous effects during circulation of Late Cretaceous hydrothermal fluids related to epithermal mineralization. The absence of significant disturbance to the 40Ar/39Ar age spectrum from the remagnetized metabasite hornblende indicates that some secondary magnetizations may go unrecognized and undated, even if 40Ar/39Ar dating is applied.
The surface of 243 Ida is dominated by the effects of impacts. No complex crater morphologies are observed. A complete range of crater degradation states is present, which also reveals optical maturation of the surface (darkening and reddening of materials with increasing exposure age). Regions of bright material associated with the freshest craters might be ballistically emplaced deposits or the result of seismic disturbance of loosely-bound surface materials. Diameter/depth ratios for fresh craters on Ida are ∼1:6.5, similar to Gaspra results, but greater than the 1:5 ratios common on other rocky bodies. Contributing causes include rim degradation by whole-body “ringing,” relatively thin ejecta blankets around crater rims, or an extended strength gradient in near-surface materials due to low gravitational self-packing. Grooves probably represent expressions in surface debris of reactivated fractures in the deeper interior. Isolated positive relief features as large as 150 m are probably ejecta blocks related to large impacts. Evidence for the presence of debris on the surface includes resolved ejecta blocks, mass-wasting scars, contrasts in color and albedo of fresh crater materials, and albedo streaks oriented down local slopes. Color data indicate relatively uniform calcium abundance in pyroxenes and constant pyroxene/olivine ratio. A large, relatively blue unit across the northern polar area is probably related to regolith processes involving ejecta from Azzurra rather than representing internal compositional heterogeneity. A small number of bluer, brighter craters are randomly distributed across the surface, unlike on Gaspra where these features are concentrated along ridges. This implies that debris on Ida is less mobile and/or consistently thicker than on Gaspra. Estimates of the average depth of mobile materials derived from chute depths (20–60 m), grooves (≥30 m), and shallowing of the largest degraded craters (20–50 m minimum, ∼100 m maximum) suggest a thickness of potentially mobile materials of ∼50 m, and a typical thickness for the debris layer of 50–100 m.
","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Icarus","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","publisher":"Academic Press","doi":"10.1006/icar.1996.0041","issn":"00191035","usgsCitation":"Sullivan, R., Greeley, R., Pappalardo, R., Asphaug, E., Moore, J.N., Morrison, D., Belton, M.J., Carr, M., Chapman, C.R., Geissler, P.E., Greenberg, R., Granahan, J., Head, J.W., Kirk, R.L., McEwen, A., Lee, P., Thomas, P., and Veverka, J., 1996, Geology of 243 Ida: Icarus, v. 120, no. 1, p. 119-139, https://doi.org/10.1006/icar.1996.0041.","productDescription":"21 p.","startPage":"119","endPage":"139","numberOfPages":"21","costCenters":[{"id":131,"text":"Astrogeology Science Center","active":true,"usgs":true}],"links":[{"id":479128,"rank":1,"type":{"id":40,"text":"Open Access Publisher Index Page"},"url":"https://doi.org/10.1006/icar.1996.0041","text":"Publisher Index Page"},{"id":227028,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"otherGeospatial":"243 Ida","volume":"120","issue":"1","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a2480e4b0c8380cd58149","contributors":{"authors":[{"text":"Sullivan, R.","contributorId":63134,"corporation":false,"usgs":true,"family":"Sullivan","given":"R.","affiliations":[],"preferred":false,"id":379636,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Greeley, R.","contributorId":6538,"corporation":false,"usgs":true,"family":"Greeley","given":"R.","email":"","affiliations":[],"preferred":false,"id":379628,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Pappalardo, R.","contributorId":84924,"corporation":false,"usgs":true,"family":"Pappalardo","given":"R.","affiliations":[],"preferred":false,"id":379641,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Asphaug, E.","contributorId":103421,"corporation":false,"usgs":true,"family":"Asphaug","given":"E.","affiliations":[],"preferred":false,"id":379643,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Moore, Johnnie N.","contributorId":13668,"corporation":false,"usgs":true,"family":"Moore","given":"Johnnie","email":"","middleInitial":"N.","affiliations":[],"preferred":false,"id":379630,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Morrison, D.","contributorId":98015,"corporation":false,"usgs":true,"family":"Morrison","given":"D.","email":"","affiliations":[],"preferred":false,"id":379642,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Belton, M. J. S.","contributorId":79223,"corporation":false,"usgs":true,"family":"Belton","given":"M.","email":"","middleInitial":"J. S.","affiliations":[],"preferred":false,"id":379639,"contributorType":{"id":1,"text":"Authors"},"rank":7},{"text":"Carr, M.","contributorId":105845,"corporation":false,"usgs":true,"family":"Carr","given":"M.","affiliations":[],"preferred":false,"id":379644,"contributorType":{"id":1,"text":"Authors"},"rank":8},{"text":"Chapman, C. R.","contributorId":12984,"corporation":false,"usgs":true,"family":"Chapman","given":"C.","email":"","middleInitial":"R.","affiliations":[],"preferred":false,"id":379629,"contributorType":{"id":1,"text":"Authors"},"rank":9},{"text":"Geissler, Paul E. pgeissler@usgs.gov","contributorId":2811,"corporation":false,"usgs":true,"family":"Geissler","given":"Paul","email":"pgeissler@usgs.gov","middleInitial":"E.","affiliations":[{"id":131,"text":"Astrogeology Science Center","active":true,"usgs":true}],"preferred":true,"id":379634,"contributorType":{"id":1,"text":"Authors"},"rank":10},{"text":"Greenberg, R.","contributorId":26778,"corporation":false,"usgs":true,"family":"Greenberg","given":"R.","email":"","affiliations":[],"preferred":false,"id":379631,"contributorType":{"id":1,"text":"Authors"},"rank":11},{"text":"Granahan, J.","contributorId":82073,"corporation":false,"usgs":true,"family":"Granahan","given":"J.","affiliations":[],"preferred":false,"id":379640,"contributorType":{"id":1,"text":"Authors"},"rank":12},{"text":"Head, J. W. III","contributorId":106267,"corporation":false,"usgs":true,"family":"Head","given":"J.","suffix":"III","email":"","middleInitial":"W.","affiliations":[],"preferred":false,"id":379645,"contributorType":{"id":1,"text":"Authors"},"rank":13},{"text":"Kirk, Randolph L. 0000-0003-0842-9226 rkirk@usgs.gov","orcid":"https://orcid.org/0000-0003-0842-9226","contributorId":2765,"corporation":false,"usgs":true,"family":"Kirk","given":"Randolph","email":"rkirk@usgs.gov","middleInitial":"L.","affiliations":[{"id":131,"text":"Astrogeology Science Center","active":true,"usgs":true}],"preferred":true,"id":379637,"contributorType":{"id":1,"text":"Authors"},"rank":14},{"text":"McEwen, A.","contributorId":39105,"corporation":false,"usgs":true,"family":"McEwen","given":"A.","affiliations":[],"preferred":false,"id":379633,"contributorType":{"id":1,"text":"Authors"},"rank":15},{"text":"Lee, P.","contributorId":47101,"corporation":false,"usgs":true,"family":"Lee","given":"P.","email":"","affiliations":[],"preferred":false,"id":379635,"contributorType":{"id":1,"text":"Authors"},"rank":16},{"text":"Thomas, P.C.","contributorId":32690,"corporation":false,"usgs":true,"family":"Thomas","given":"P.C.","affiliations":[],"preferred":false,"id":379632,"contributorType":{"id":1,"text":"Authors"},"rank":17},{"text":"Veverka, J.","contributorId":71689,"corporation":false,"usgs":true,"family":"Veverka","given":"J.","email":"","affiliations":[],"preferred":false,"id":379638,"contributorType":{"id":1,"text":"Authors"},"rank":18}]}} ,{"id":70018506,"text":"70018506 - 1996 - Three-dimensional P and S wave velocity structure of Redoubt Volcano, Alaska","interactions":[],"lastModifiedDate":"2019-03-15T10:43:20","indexId":"70018506","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2314,"text":"Journal of Geophysical Research B: Solid Earth","active":true,"publicationSubtype":{"id":10}},"title":"Three-dimensional P and S wave velocity structure of Redoubt Volcano, Alaska","docAbstract":"The three‐dimensional P and S wave structure of Redoubt Volcano, Alaska, and the underlying crust to depths of 7–8 km is determined from 6219 P wave and 4008 S wave first‐arrival times recorded by a 30‐station seismograph network deployed on and around the volcano. First‐arrival times are calculated using a finite‐difference technique, which allows for flexible parameterization of the slowness model and easy inclusion of topography and source‐receiver geometry. The three‐dimensional P wave velocity structure and hypocenters are determined simultaneously, while the three‐dimensional Swave velocity model is determined using the relocated seismicity and an initial S wave velocity model derived from the P wave velocity model assuming an average Vp/Vs ratio of 1.78. Convergence is steady with approximately 73% and 52% reduction in P and Swave arrival time RMS, respectively, after 10 iterations. The most prominent feature observed in the three‐dimensional velocity models derived for both P and S waves is a relative low‐velocity, near‐vertical, pipelike structure approximately 1 km in diameter that extends from 1 to 6 km beneath sea level. This feature aligns axially with the bulk of seismicity and is interpreted as a highly fractured and altered zone encompassing a magma conduit. The velocity structure beneath the north flank of the volcano between depths of 1 and 6 km is characterized by large lateral velocity variations. High velocities within this region are interpreted as remnant dikes and sills and low velocities as regions along which magma migrates. No large low‐velocity body suggestive of a magma chamber is resolved in the upper 7–8 km of the crust.
","language":"English","publisher":"AGU","doi":"10.1029/95JB03046","issn":"01480227","usgsCitation":"Benz, H., Chouet, B., Dawson, P., Lahr, J., Page, R., and Hole, J., 1996, Three-dimensional P and S wave velocity structure of Redoubt Volcano, Alaska: Journal of Geophysical Research B: Solid Earth, v. 101, no. 4, p. 8111-8128, https://doi.org/10.1029/95JB03046.","productDescription":"18 p.","startPage":"8111","endPage":"8128","costCenters":[{"id":615,"text":"Volcano Hazards Program","active":true,"usgs":true}],"links":[{"id":227302,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"101","issue":"4","noUsgsAuthors":false,"publicationDate":"1996-04-10","publicationStatus":"PW","scienceBaseUri":"505bb31de4b08c986b325bb1","contributors":{"authors":[{"text":"Benz, H.M.","contributorId":21594,"corporation":false,"usgs":true,"family":"Benz","given":"H.M.","email":"","affiliations":[],"preferred":false,"id":379856,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Chouet, B. A.","contributorId":31813,"corporation":false,"usgs":true,"family":"Chouet","given":"B. A.","affiliations":[],"preferred":false,"id":379857,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Dawson, P.B.","contributorId":75934,"corporation":false,"usgs":true,"family":"Dawson","given":"P.B.","email":"","affiliations":[],"preferred":false,"id":379860,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Lahr, J.C.","contributorId":34892,"corporation":false,"usgs":true,"family":"Lahr","given":"J.C.","email":"","affiliations":[],"preferred":false,"id":379858,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Page, R.A.","contributorId":40197,"corporation":false,"usgs":true,"family":"Page","given":"R.A.","email":"","affiliations":[],"preferred":false,"id":379859,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Hole, J.A.","contributorId":103422,"corporation":false,"usgs":true,"family":"Hole","given":"J.A.","email":"","affiliations":[],"preferred":false,"id":379861,"contributorType":{"id":1,"text":"Authors"},"rank":6}]}} ,{"id":70018196,"text":"70018196 - 1996 - The Flinn-Engdahl Regionalisation Scheme: The 1995 revision","interactions":[],"lastModifiedDate":"2012-03-12T17:19:22","indexId":"70018196","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":3071,"text":"Physics of the Earth and Planetary Interiors","active":true,"publicationSubtype":{"id":10}},"title":"The Flinn-Engdahl Regionalisation Scheme: The 1995 revision","docAbstract":"The Flinn-Engdahl Regionalisation Scheme, also known as the F-E Code, has been used by seismologists for many years to identify and specify regions of the Earth. The Working Group on Regionalisation of the International Association of Seismology and Physics of the Earth's Interior (IASPEI) Commission on Practice has the task of defining a new standard for the regionalisation of the Earth. In the meantime, it was agreed that a revision of the F-E Code would be appropriate. This paper presents the 1995 revision and supersedes the F-E Code standard published in 1974.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Physics of the Earth and Planetary Interiors","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1016/0031-9201(96)03141-X","issn":"00319201","usgsCitation":"Young, J., Presgrave, B., Aichele, H., Wiens, D., and Flinn, E., 1996, The Flinn-Engdahl Regionalisation Scheme: The 1995 revision: Physics of the Earth and Planetary Interiors, v. 96, no. 4, p. 223-297, https://doi.org/10.1016/0031-9201(96)03141-X.","startPage":"223","endPage":"297","numberOfPages":"75","costCenters":[],"links":[{"id":205882,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1016/0031-9201(96)03141-X"},{"id":227279,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"96","issue":"4","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505ba72ee4b08c986b3213f3","contributors":{"authors":[{"text":"Young, J.B.","contributorId":72944,"corporation":false,"usgs":true,"family":"Young","given":"J.B.","email":"","affiliations":[],"preferred":false,"id":378845,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Presgrave, B.W.","contributorId":103298,"corporation":false,"usgs":true,"family":"Presgrave","given":"B.W.","email":"","affiliations":[],"preferred":false,"id":378847,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Aichele, H.","contributorId":44304,"corporation":false,"usgs":true,"family":"Aichele","given":"H.","email":"","affiliations":[],"preferred":false,"id":378844,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Wiens, D.A.","contributorId":94802,"corporation":false,"usgs":true,"family":"Wiens","given":"D.A.","email":"","affiliations":[],"preferred":false,"id":378846,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Flinn, E.A.","contributorId":23290,"corporation":false,"usgs":true,"family":"Flinn","given":"E.A.","email":"","affiliations":[],"preferred":false,"id":378843,"contributorType":{"id":1,"text":"Authors"},"rank":5}]}} ,{"id":1014916,"text":"1014916 - 1996 - Gas-phase axial dispersion in a spray tower","interactions":[],"lastModifiedDate":"2023-08-09T15:21:12.2933","indexId":"1014916","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":852,"text":"Aquacultural Engineering","active":true,"publicationSubtype":{"id":10}},"title":"Gas-phase axial dispersion in a spray tower","docAbstract":"Gas-phase axial dispersion (mixing of the composition of the gas phase along the longitudinal axis) was characterized in an enclosed spray tower for purposes of establishing reactor type for the solute-solvent pair oxygen and water. Test condition variables were spray tower height (TH), 1·52, 2·03 and 2·54 m; hydraulic loading (HL), 44·2, 66·3 and 88·4 kg/m2s; the ratio of volumetric oxygen injection to water flow rate (G/L), 1·0, 2·5 and 5·0%; the ratio of volumetric bulk tower gas recirculation flow rate to water flow rate (BG/L), 0, 500 and 700%; and bulk tower gas recirculation direction, counter-current to and co-current to the water flow. Gas composition measurements (% O2) made across the long axis of the tower under steady-state conditions provided 1020 independent observations and 240 gas composition profiles. Factors showing a significant effect (P < 0·05) on gas composition were TH, HL, G/L and BG/L. Sample location as a percentage of TH did not have a significant effect on gas composition and accordingly profile slopes were not different from zero (P > 0·05). Profile data indicate a completely mixed gas phase within the tower. The dispersion observed was attributed to the lack of a significant pressure drop along the axis of the reaction vessel, forces due to nozzle operation, and to bulk tower gas recirculation.
","language":"English","publisher":"Elsevier","doi":"10.1016/0144-8609(95)00001-U","usgsCitation":"Vinci, B.J., Watten, B.J., and Timmons, M., 1996, Gas-phase axial dispersion in a spray tower: Aquacultural Engineering, v. 15, no. 1, p. 1-11, https://doi.org/10.1016/0144-8609(95)00001-U.","productDescription":"11 p.","startPage":"1","endPage":"11","numberOfPages":"11","costCenters":[{"id":365,"text":"Leetown Science Center","active":true,"usgs":true}],"links":[{"id":479097,"rank":2,"type":{"id":40,"text":"Open Access Publisher Index Page"},"url":"https://doi.org/10.1016/0144-8609(95)00001-u","text":"Publisher Index Page"},{"id":130705,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"15","issue":"1","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"4f4e4b28e4b07f02db6b1295","contributors":{"authors":[{"text":"Vinci, Brian J.","contributorId":71890,"corporation":false,"usgs":true,"family":"Vinci","given":"Brian","email":"","middleInitial":"J.","affiliations":[],"preferred":false,"id":321528,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Watten, Barnaby J. 0000-0002-2227-8623 bwatten@usgs.gov","orcid":"https://orcid.org/0000-0002-2227-8623","contributorId":2002,"corporation":false,"usgs":true,"family":"Watten","given":"Barnaby","email":"bwatten@usgs.gov","middleInitial":"J.","affiliations":[{"id":365,"text":"Leetown Science Center","active":true,"usgs":true}],"preferred":true,"id":321527,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Timmons, Michael","contributorId":239537,"corporation":false,"usgs":false,"family":"Timmons","given":"Michael","email":"","affiliations":[],"preferred":false,"id":321529,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70017697,"text":"70017697 - 1996 - Loess studies in central United States: Evolution of concepts","interactions":[],"lastModifiedDate":"2023-12-16T13:30:10.560695","indexId":"70017697","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1517,"text":"Engineering Geology","active":true,"publicationSubtype":{"id":10}},"title":"Loess studies in central United States: Evolution of concepts","docAbstract":"Few words in the realm of earth science have caused more debate than \"loess\". It is a common term that was first used as a name of a silt deposit before it was defined in a scientific sense. Because this \"loose\" deposit is easily distinguished from other more coherent deposits, it was recognized as a matter of practical concern and later became the object of much scientific scrutiny. Loess was first recognized along the Rhine Valley in Germany in the 1830s and was first noted in the United States in 1846 along the lower Mississippi River where it later became the center of attention. The use of the name eventually spread around the world, but its use has not been consistently applied. Over the years some interpretations and stratigraphic correlations have been validated, but others have been hotly contested on conceptual grounds and semantic issues. The concept of loess evolved into a complex issue as loess and loess-like deposits were discovered in different parts of the US. The evolution of concepts in the central US developed in four indefinite stages: the eras of (1) discovery and development of hypotheses, (2) conditional acceptance of the eolian origin of loess, (3) \"bandwagon\" popularity of loess research, and (4) analytical inquiry on the nature of loess. Toward the end of the first era around 1900, the popular opinion on the meaning of the term loess shifted from a lithological sense of loose silt to a lithogenetic sense of eolian silt. However, the dual use of the term fostered a lingering skepticism during the second era that ended in 1944 with an explosion of interest that lasted for more than a decade. In 1944, R.J. Russell proposed and H.N. Fisk defended a new non-eolian, property-based, concept of loess. The eolian advocates reacted with surprise and enthusiasm. Each side used constrained arguments to show their view of the problem, but did not examine the fundamental problem, which was not in the proofs of their hypothesis, but in the definition of the term. Between 1944 and about 1950, the debates about loess reached a maximum level of complexity. The main semantic problem was submersed in peripheral arguments about physical properties and genetic interpretations. The scholarly treatment of the subject by Fisk and Russell stimulated quality responses from a diversity of earth scientists interested in academic and applied studies, particularly geo-history, pedology, soil mechanics and stratigraphy. The long-lasting popularity of loess studies during the bandwagon era lasted to about 1970. By that time, the analytical and technical interests had attracted the mainstream into the fourth era with a focus beyond the old arguments. Although Fisk and Russell found themselves defending an unpopular theory, they stimulated a scientific interest in the late Quaternary history of the Mississippi Valley that may never be exceeded.","language":"English","publisher":"Elsevier","doi":"10.1016/S0013-7952(96)00018-X","issn":"00137952","usgsCitation":"Follmer, L., 1996, Loess studies in central United States: Evolution of concepts: Engineering Geology, v. 45, no. 1-4, p. 287-304, https://doi.org/10.1016/S0013-7952(96)00018-X.","productDescription":"18 p.","startPage":"287","endPage":"304","numberOfPages":"18","costCenters":[],"links":[{"id":229038,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"45","issue":"1-4","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a493de4b0c8380cd68455","contributors":{"authors":[{"text":"Follmer, L.R.","contributorId":19294,"corporation":false,"usgs":true,"family":"Follmer","given":"L.R.","email":"","affiliations":[],"preferred":false,"id":377297,"contributorType":{"id":1,"text":"Authors"},"rank":1}]}} ,{"id":70017698,"text":"70017698 - 1996 - Shallow velocity structure and Poisson's ratio at the Tarzana, California, strong-motion accelerometer site","interactions":[],"lastModifiedDate":"2023-10-24T00:53:08.181259","indexId":"70017698","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1135,"text":"Bulletin of the Seismological Society of America","onlineIssn":"1943-3573","printIssn":"0037-1106","active":true,"publicationSubtype":{"id":10}},"title":"Shallow velocity structure and Poisson's ratio at the Tarzana, California, strong-motion accelerometer site","docAbstract":"The 17 January 1994, Northridge, California, earthquake produced strong ground shaking at the Cedar Hills Nursery (referred to here as the Tarzana site) within the city of Tarzana, California, approximately 6 km from the epicenter of the mainshock. Although the Tarzana site is on a hill and is a rock site, accelerations of approximately 1.78 g horizontally and 1.2 g vertically at the Tarzana site are among the highest ever instrumentally recorded for an earthquake. To investigate possible site effects at the Tarzana site, we used explosive-source seismic refraction data to determine the shallow (<70 m) P-and S-wave velocity structure. Our seismic velocity models for the Tarzana site indicate that the local velocity structure may have contributed significantly to the observed shaking. P-wave velocities range from 0.9 to 1.65 km/sec, and S-wave velocities range from 0.20 and 0.6 km/sec for the upper 70 m. We also found evidence for a local S-wave low-velocity zone (LVZ) beneath the top of the hill. The LVZ underlies a CDMG strong-motion recording site at depths between 25 and 60 m below ground surface (BGS). Our velocity model is consistent with the near-surface (<30 m) P- and S-wave velocities and Poisson's ratios measured in a nearby (<30 m) borehole. High Poisson's ratios (0.477 to 0.494) and S-wave attenuation within the LVZ suggest that the LVZ may be composed of highly saturated shales of the Modelo Formation. Because the lateral dimensions of the LVZ approximately correspond to the areas of strongest shaking, we suggest that the highly saturated zone may have contributed to localized strong shaking. Rock sites are generally considered to be ideal locations for site response in urban areas; however, localized, highly saturated rock sites may be a hazard in urban areas that requires further investigation.