Soils, time, and primate paleoenvironments
Thomas M. Bown, M. J. Kraus
1993, Evolutionary Anthropology (2) 11-21
Soils are the skin of the earth. From both poles to the equator, wherever rocks or sediment are exposed at the surface, soils are forming through the physical and chemical action of climate and living organisms. The physical attributes (color, texture, thickness) and chemical makeup of soils vary considerably, depending...
Ground water discharge and the related nutrient and trace metal fluxes into Quincy Bay, Massachusetts
L.J. Poppe, A.M. Moffett
1993, Environmental Monitoring and Assessment (25) 15-27
Measurement of the rate and direction of ground water flow beneath Wollaston Beach, Quincy, Massachusetts by use of a heat-pulsing flowmeter shows a mean velocity in the bulk sediment of 40 cm d−1. The estimated total discharge of ground water into Quincy Bay during October 1990 was 1324–2177 m3 d−1, a...
Reconnaissance guidelines for gold exploration in Central Alaska
T.D. Light, S. H. Moll, S. W. Bie, G. K. Lee
1993, Journal of Geochemical Exploration (47) 89-108
Distribution of more than 300 gold-bearing samples from the Livengood (Tolovana) and parts of the Fairbanks and Rampart mining districts in central Alaska, USA, indicate that the concentration of gold in placers is spatially related both to structural features and to Late Cretaceous and (or) Tertiary felsic plutons. The regional...
The role of acoustic emission in the study of rock fracture
D. Lockner
1993, International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts (30) 883-899
The development of faults and shear fracture systems over a broad range of temperature and pressure and for a variety of rock types involves the growth and interaction of microcracks. Acoustic emission (AE), which is produced by rapid microcrack growth, is a ubiquitous phenomenon associated with brittle fracture and has...
Diatom zonation in southern Oregon tidal marshes relative to vascular plants, foraminifera, and sea level
A.R. Nelson, K. Kashima
1993, Journal of Coastal Research (9) 673-697
Diatom assemblages across estuarine marshes show a three-part vertical ecologic zonation of the intertidal zone similar to zonations of foraminiferal and vascular plant assemblages. Gradual changes in the compositions of all three types of assemblages reflect gradational zone boundaries, 5-40m wide. Modern mudflat, low marsh, and high marsh zones can...
Ikaite precipitation by mixing of shoreline springs and lake water, Mono Lake, California, USA
J. L. Bischoff, S. Stine, R.J. Rosenbauer, J.A. Fitzpatrick, Thomas W. Stafford Jr.
1993, Geochimica et Cosmochimica Acta (57) 3855-3865
Metastable ikaite (CaCO3·6H2O) forms abundantly during winter months along the south shoreline of Mono Lake where shoreline springs mix with lake water. Ikaite precipitates because of its decreased solubility at low temperature and because of orthophosphate-ion inhibition of calcite and aragonite. During the spring some of the ikaite is transformed...
Prediction by regression and intrarange data scatter in surface-process studies
T.J. Toy, W. R. Osterkamp, K.G. Renard
1993, Environmental Geology (22) 121-128
Modeling is a major component of contemporary earth science, and regression analysis occupies a central position in the parameterization, calibration, and validation of geomorphic and hydrologic models. Although this methodology can be used in many ways, we are primarily concerned with the prediction of values for one variable from another...
Three-dimensional simulations of ground motions in the San Bernardino Valley, California, for hypothetical earthquakes on the San Andreas Fault
A. Frankel
1993, Bulletin of the Seismological Society of America (83) 1020-1041
Three-dimensional finite difference simulations of elastic waves in the San Bernardino Valley were performed for two hypothetical earthquakes on the San Andreas fault: a point source with moment magnitude M5 and an extended rupture with M6.5. A method is presented for incorporating a source with arbitrary focal mechanism in the...
Loma Prieta response of an eccentrically braced tall building
M. Çelebi
1993, Conference Paper, Structural Engineering in Natural Hazards Mitigation
Acceleration response records obtained during the October 17, 1989 Loma Prieta earthquake [Ms = 7.1] from the 47-story, eccentrically braced Embarcadero Building (No. 4) [EMB], located in San Francisco, California, are studied. The predominant response modes of the building and the associated dynamic characteristics are determined by spectral analyses and...
The Cape Mendocino, California, earthquakes of April 1992: Subduction at the triple junction
D. Oppenheimer, G. Beroza, G. Carver, L. Dengler, Jerry P. Eaton, L. Gee, F. Gonzalez, A. Jayko, W.H. Li, M. Lisowski, M. Magee, G. Marshall, M. Murray, R. McPherson, B. Romanowicz, K. Satake, R. Simpson, P. Somerville, R. Stein, D. Valentine
1993, Science (261) 433-438
The 25 April 1992 magnitude 7.1 Cape Mendocino thrust earthquake demonstrated that the North America—Gorda plate boundary is seismogenic and illustrated hazards that could result from much larger earthquakes forecast for the Cascadia region. The shock occurred just north of the Mendocino Triple Junction and caused strong ground motion and...
Three-dimensional simulations of ground motions in sedimentary basins
Arthur Frankel
1993, Conference Paper, Structural Engineering in Natural Hazards Mitigation
This report describes work being done at the U.S. Geological Survey on 3-D simulations of earthquake ground motions in sedimentary basins. The ultimate goal of this research is to predict strong ground motions in sedimentary basins for expected large earthquakes. This report emphasizes the inadequacy of using flat-layered models for...
Monazite paragenesis and U-Pb systematics in rocks of the eastern Mojave Desert, California, U.S.A.: implications for thermochronometry
J.A. Kingsbury, C. F. Miller, J. L. Wooden, T.M. Harrison
1993, Chemical Geology (110) 147-167
Studies of the paragenesis and U-Pb systematics of monazite in rocks from the eastern Mojave Desert, California, corroborate its potential usefulness as a prograde thermochronometer and in dating granite inheritance. Unmetamorphosed Latham Shale and its equivalents at grades ranging from greenschist to upper amphibolite facies are virtually identical in composition....
Delayed Postglacial Uplift and Synglacial Sea Levels in Coastal Central New England
C. Koteff, Robinson Jr., R. Goldsmith, W.B. Thompson
1993, Quaternary Research (40) 46-54
The postglacial uplift pattern indicated by elevations of ice-marginal glaciomarine deltas in coastal New England, deposited between approximately 15,000 and 14,000 yr B.P. during ice retreat from northeastern Massachusetts into southwestern Maine, is very similar to that previously recorded for glaciolacustrine deltas of similar age from inland areas of New...
Seismic responses of two adjacent buildings. I. Data and analyses
Mehmet Çelebi
1993, Journal of Structural Engineering (119) 2461-2476
In this two-part paper, responses of two, adjacent, seven-story buildings in Norwalk, California, to the Whittier-Narrows, Calif, earthquake of Oct. 1, 1987 are studied. Building A, instrumented according to code recommendations, and building B, extensively instrumented, are offset by 16.3 m from one another. The data set includes motions from...
Interface dissolution control of the 14C profile in marine sediment
R.S. Keir, R. L. Michel
1993, Geochimica et Cosmochimica Acta (57) 3563-3573
The process of carbonate dissolution at the sediment-water interface has two possible endmember boundary conditions. Either the carbonate particles dissolve mostly before they are incorporated into the sediment by bioturbation (interface dissolution), or the vertical mixing is rapid relative to their extermination rate (homogeneous dissolution). In this study, a detailed...
Multiphase inclusions in plagioclase from anorthosites in the Stillwater Complex, Montana: implications for the origin of the anorthosites
P. J. Loferski, R.J. Arculus
1993, Contributions to Mineralogy and Petrology (114) 63-78
Multiphase inclusions, consisting of clinopyroxene+ilmenite+apatite, occur within cumulus plagioclase grains from anorthosites in the Stillwater Complex, Montana, and in other rocks from the Middle Banded series of the intrusion. The textures and constant modal mineralogy of the inclusions indicate that they were incorporated in the plagioclase as liquid droplets that...
Seismic reflection profiling across Tertiary extensional structures in the eastern Amargosa Desert, southern Nevada, Basin and Range province
T.M. Brocher, M. D. Carr, K. F. Fox Jr., P. E. Hart
1993, Geological Society of America Bulletin (105) 30-46
Outcrops, shallow well control, and coincident geophysical surveys are used to interpret a seismic reflection profile in the Amargosa Desert, within the Basin and Range province, of southern Nevada. The east-west-trending, 27-km-long seismic line crosses all or parts of three Tertiary subbasins, revealing...
The Point Lookout Sandstone: a tale of two cores, or petrology, diagenesis, and reservoir properties of Point Lookout Sandstone, Southern Ute Indian Reservation, San Juan Basin, Colorado
C. W. Keighin, R. S. Zech, R.W. Dunbar
1993, Mountain Geologist (30) 5-16
The Point Lookout sandstones are quartz-rich, fine to very-fine grained, and contain moderately variable quantities of potassium feldspar (2 to 20 modal percent) and lithic fragments (9 to 20 modal percent). Locally, sandstone is tightly cemented by carbonate cement; clays are not important as cementing agents, although they significantly reduce...
The Solubility and Stabilization of Ikaite (CaCO3·6H2O) from 0° to 25°C: Environmental and Paleoclimatic Implications for Thinolite Tufa
James L. Bischoff, John A. Fitzpatrick, Robert J. Rosenbauer
1993, Journal of Geology (101) 21-33
We determined the solubility of ikaite from 0° to 25°C to model its saturation state in natural waters and test the hypothesis that it is the precursor of the calcite pseudomorphs in thinolite tufa of Quaternary Lake Lahontan. Reversible solubility at buffered...
Gas buildup in Lake Nyos, Cameroon: The recharge process and its consequences
William C. Evans, G.W. Kling, M. L. Tuttle, G. Tanyileke, L. D. White
1993, Applied Geochemistry (8) 207-221
The gases dissolved in Lake Nyos, Cameroon, were quantified recently (December 1989 and September 1990) by two independent techniques: in-situ measurements using a newly designed probe and laboratory analyses of samples collected in pre-evacuated stainless steel cylinders. The highest concentrations of CO2 and CH4 were...
An episode of reinflation of the Long Valley Caldera, eastern California: 1989-1991
J. Langbein, D.P. Hill, T.N. Parker, S.K. Wilkinson
1993, Journal of Geophysical Research (98) 15851-15870
Following the episodes of inflation of the resurgent dome associated with the May 1980 earthquake sequence (four M 6 earthquakes) and the January 1983 earthquake swarm (two M 5.2 events), 7 years of frequently repeated two-color geodimeter measurements spanning the Long Valley caldera document gradually decreasing extensional strain rates...
Heat flow from four new research drill holes in the Western Cascades, Oregon, U.S.A.
S. E. Ingebritsen, M. A. Scholl, D. R. Sherrod
1993, Geothermics (22) 151-163
Conceptual models of the thermal structure of the Oregon Cascade Range propose either (1) a narrow zone of magmatic heat sources, flanked by shallow heat-flow anomalies caused by lateral ground-water flow; or (2) a wide zone of magmatic heat sources, with localized, generally negligible ground-water effects. The proposed narrow heat...
Climatic impact on isovolumetric weathering of a coarse-grained schist in the northern Piedmont Province of the central Atlantic states
E.T. Cleaves
1993, Geomorphology (8) 191-198
The possible impact of periglacial climates on the rate of chemical weathering of a coarse-grained plagioclase-muscovite-quartz schist has been determined for a small watershed near Baltimore, Maryland. The isovolumetric chemical weathering model formulated from the geochemical mass balance study of the watershed...
Alternative solution model for the ternary carbonate system CaCO3 - MgCO3 - FeCO3 - I. A ternary Bragg-Williams ordering model
P.L. McSwiggen
1993, Physics and Chemistry of Minerals (20) 33-41
The minerals of the ternary carbonate system CaCO3 - MgCO3 - FeCO3 represent a complex series of solid solutions and ordering states. An understanding of those complexities requires a solution model that can both duplicate the subsolidus phase relationships and generate correct values for the activities. Such a solution model...
Alternative solution model for the ternary carbonate system CaCO3 - MgCO3 - FeCO3 - II. Calibration of a combined ordering model and mixing model
P.L. McSwiggen
1993, Physics and Chemistry of Minerals (20) 42-55
Earlier attempts at solution models for the ternary carbonate system have been unable to adequately accommodate the cation ordering which occurs in some of the carbonate phases. The carbonate solution model of this study combines a Margules type of interaction model with a Bragg-Williams type of ordering model. The ordering...
