An oxygen isotope model for interpreting carbonate diagenesis in nonmarine rocks (Green River Basin, Wyoming, USA)
W. W. Dickinson
1987, Chemical Geology (65) 103-116
A closed-system model is used for predicting the δ18O of formation waters in the deep portions of the northern Green River basin, Wyoming. δ18Ocalcite is calculated from this modeled water and compared with the δ18O of measured calcites to help interpret diagenesis in the basin.The modification of 18Owater, which may be caused...
Quaternary silicic pyroclastic deposits of Atitlán Caldera, Guatemala
William I. Rose Jr., Christopher G. Newhall, Theodore J. Bornhorst, Stephen Self
1987, Journal of Volcanology and Geothermal Research (33) 57-80
Atitlán caldera has been the site of several silicic eruptions within the last 150,000 years, following a period of basalt/andesite volcanism. The silicic volcanism began with 5–10 km3 of rhyodacites, erupted as plinian fall and pyroclastic flows, about 126,000 yr. B.P. At 85,000 yr. B.P. 270–280 km3 of compositionally distinct rhyolite was...
Aquatic ecoregions of the conterminous United States
J.M. Omernick
1987, Report
Ecoregions are based on perceived patterns of a combination of causal and integrative factors including land use, land surface form, potential natural vegetation, and soils (Omernik, 1987). This is a copy of the ecoregion coverage of Omernik (1987) with some item names modified. This is NOT the most recent...
The geomagnetic jerk of 1969 and the DGRFs
D. Thompson, J.C. Cain
1987, Physics of the Earth and Planetary Interiors (48) 386-388
Cubic spline fits to the DGRF/IGRF series indicate agreement with other analyses showing the 1969-1970 magnetic jerk in the h ??12 and g ??02 secular change coefficients, and agreement that the h ??11 term showed no sharp change. The variation of the g ??01 term is out of phase with...
Crescentic dunes on the inner continental shelf off northern California
D.A. Cacchione, M.E. Field, D.E. Drake, G. B. Tate
1987, Geology (15) 1134-1137
Large crescentic dunes that resemble barchans have been discovered within elongate scour depressions on the northern California inner continental shelf by using side-scan sonar. These dunes appear to be migrating obliquely to the regional shelf gradient; a preferred offshore direction of transport is...
GEOGRAPHIC ESTIMATION OF RUNOFF-MODEL PARAMETERS.
Arthur R. Schmidt, Linda S. Weiss, Kevin A. Oberg
1987, Conference Paper
The U. S. Geological Survey is developing techniques to estimate and evaluate unit-hydrograph and loss-rate parameter values for rainfall-runoff models using Geographic Information System (GIS) procedures. The data base includes basin, soil, and climatological characteristics that will be stored in a GIS, and unit-hydrograph and loss-rate parameters obtained from calibration...
Implications of the northwestwardly younger age of the volcanic rocks of west-central California: Alternative Interpretation
Richard G. Stanley
1987, GSA Bulletin (98) 612-614
Fox and others (1985) have made an important contribution to our understanding of iihe evolution of the Mendocino triple junction and the San Andreas transform. They have summarized a large amount of data on the ages and distribution of volcanic centers along the central California coast; their summary clearly shows...
A Pennsylvanian-age terrestrial storm deposit: using plant fossils to characterize the history and process of sediment accumulation
C. Wnuk, H.W. Pfefferkorn
1987, Journal of Sedimentary Petrology (57) 212-221
A thin black shale overlying the B-coal underclay (in the Middle Pennsylvanian post-Pottsville strata of the Bernice Basin) contains a compression flora composed of large, prostrate, unidirectionally oriented lycopod trunks and randomly oriented pteridosperm stems. Analyses of modern log accumulations indicate that unidirectional...
Stable isotope compositions of fossil mollusks from southern California: Evidence for a cool last interglacial ocean.
D.R. Muhs, T.K. Kyser
1987, Geology (15) 119-122
Stable isotope compositions have been determined for modern mullusks and fossil mollusks collected from uplifted marine terraces at three localities in southern California. By using a paleoclimatic model that decouples the temperature and ice-volume signals in ocean water, ocean-water temperatures off southern California...
Subsidence, crustal structure, and thermal evolution of Georges Bank basin
B. Ann Swift, D. S. Sawyer, J. A. Grow, Kim D. Klitgord
1987, American Association of Petroleum Geologists Bulletin (71) 702-718
A geophysical study of Georges Bank basin defines a deep crustal structure that is interpreted in terms of the basin's tectonic and thermal history. Gravity models along three basin cross sections delineate two zones of crustal thinning at the basement hinge zone and oceanic crustal margins. These two zones bound...
Multiple sources of alkanes in Quaternary oceanic sediment of Antarctica
Keith A. Kvenvolden, John B. Rapp, Margaret Golan-Bac, Frances D. Hostettler
1987, Organic Geochemistry (11) 291-302
Normal alkanes (n-C13n-C36), isoprenoid hydrocarbons (i-C15, i-C16, i-C18, i-C19, and i-C20) triterpanes (C27C32), and (C27C29) are present in low concentrations offshore Antarctica in near-surface, Quaternary sediment of the Wilkes Land continental margin and of the western Ross Sea. The distributions of these...
36Cl: A tracer in groundwater in the aquia formation of Southern Maryland
C.B. Purdy, A.C. Mignerey, G.R. Helz, D.D. Drummond, P.W. Kubik, D. Elmore, T. Hemmick
1987, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms (29) 372-375
The Aquia Formation (Paleocene) of Southern Maryland, a marine unit consisting predominantly of quartz sands, but containing 20-40% glauconite, represents one of the many productive, heavily pumped aquifers of the Southeastern Coastal Plain. An unusually high 36Cl activity ( ~ 15 ?? modem water) measured in an outcrop sample is...
Chalcopyrite disease in sphalerite: pathology and epidemiology.
P. B. Barton Jr., P. M. Bethke
1987, American Mineralogist (72) 451-467
This descriptive paper identifies three widely occurring textures designated as 'watermelon', 'dusting' and 'bimodal' that characterize the replacement of original Fe-bearing sphalerite by an aggregate of chalcopyrite and low-Fe sphalerite as an integral part of the mineralization process. Replacement probably predominates over alternative modes of origin for small chalcopyrite blebs...
A model of geomagnetic secular variation for 1980-1983
N.W. Peddie, A.K. Zunde
1987, Physics of the Earth and Planetary Interiors (48) 324-329
We developed an updated model of the secular variation of the main geomagnetic field during 1980 through 1983 based on annual mean values for that interval from 148 worldwide magnetic observatories. The model consists of a series of 80 spherical harmonics, up to and including those of degree and order...
Integration of channel and floodplain suites. I. Developmental sequence and lateral relations of alluvial paleosols.
T. M. Bown, M. J. Kraus
1987, Journal of Sedimentary Petrology (57) 587-601
The lower Eocene Willwood Formation of the Bighorn Basin, northwest Wyoming, consists of about 770 m of alluvial rocks that exhibit extensive mechanical and geochemical modifications resulting from Eocene pedogenesis. Willwood paleosols vary considerably in their relative degrees of maturity; maturity is defined...
Basin-ring spacing on the Moon, Mercury, and Mars
R.J. Pike, P. D. Spudis
1987, Earth, Moon and Planets (39) 129-194
Radial spacing between concentric rings of impact basins that lack central peaks is statistically similar and nonrandom on the Moon, Mercury, and Mars, both inside and outside the main ring. One spacing interval, (2.0 ?? 0.3)0.5D, or an integer multiple of it, dominates most basin rings. Three analytical approaches yield...
Langrangian model of nitrogen kinetics in the Chattahoochee River
H.E. Jobson
1987, Journal of Environmental Engineering (113) 223-242
A Lagrangian reference frame is used to solve the convection‐dispersion equation and interpret water‐quality data obtained from the Chattahoochee River. The model was calibrated using unsteady concentrations of organic nitrogen, ammonia, and nitrite plus nitrate obtained during June 1977 and verified using data obtained during August 1976. Reaction kinetics of...
Probability theory versus simulation of petroleum potential in play analysis
R. A. Crovelli
1987, Annals of Operations Research (8) 363-381
An analytic probabilistic methodology for resource appraisal of undiscovered oil and gas resources in play analysis is presented. This play-analysis methodology is a geostochastic system for petroleum resource appraisal in explored as well as frontier areas. An objective was to replace an existing Monte Carlo simulation method in order to...
Mid-Holocene climate in Northern Minnesota
R. M. Forester, L.D. Delorme, J.P. Bradbury
1987, Quaternary Research (28) 263-273
Study of Holocene ostracodes and diatoms from Elk Lake, in North-Central Minnesota, indicates that the local climate of the mid-Holocene can be subdivided into three intervals. Throughout interval 1 (ca. 7800 to 6700 yr B.P.), climate was colder and much drier than today. During intervals 2 and 3 (ca. 6700...
Maestrichtian benthic foraminifers from Ocean Point, North Slope, Alaska ( USA).
K. McDougall
1987, Journal of Foraminiferal Research (17) 344-366
Previous studies of fauna and flora from Ocean Point, Alaska, have suggested ages ranging from Campanian to early Eocene and that these assemblages are either highly endemic or commonplace. I demonstrate that the moderately abundant benthic foraminifers constitute early Maestrichtian boreal assemblages common to Canada and northern Europe. Paleoenvironmental analysis...
Natural-field and very low-frequency tipper profile interpretation of contacts
Victor F. Labson, Alex Becker
1987, Geophysics (52) 1697-1707
Anomalous vertical magnetic field (tipper) profiles acquired using natural or very low-frequency (VLF) radio transmitter sources can be interpreted simply and rapidly for a number of geologic settings. The relations between computed numerical models, and outcropping dipping and buried vertical contacts are presented here in a series of interpretation charts....
NONHOMOGENEOUS TERMS IN THE UNSTEADY FLOW EQUATIONS: MODELING ASPECTS.
Chintu Lai, Raymond W. Schaffranek, Robert A. Baltzer
1987, Conference Paper
A study is in progress to identify the relative significance, effects, and benefits attributable to the use of one-dimensional, unsteady, open-channel, flow-simulation models employing a variety of nonhomogeneous terms in their equation formulations. Nonhomogeneous terms being analyzed include those representing bed slope, frictional resistance, nonprismatic channel geometry, lateral flow, and...
Benthic foraminifera of the Panamanian Province: distribution and origins.
R.W. Crouch, C. W. Poag
1987, Journal of Foraminiferal Research (17) 153-176
Two hundred twenty-nine species of benthic foraminifera have been identified from 96 stations representing 33 localities on the eastern Pacific inner continental shelf, ranging from southern Peru to northern Baja California. Their distributions mark nearshore provincial boundaries that are nearly identical with those previously documented from the distribution of ostracodes...
Some effects of climate variability on hydrology in western North America
D. H. Peterson, D.R. Cayan, J. S. Dileo-Stevens, T.G. Ross
1987, Conference Paper, The influence of climate change and climatic variability on the hydrologic regime and water resources (Proceedings of the Vancouver Symposium, August 1987), IAHS Publication no. 168
The strong north-south gradient in precipitation along the West Coast makes this region an interesting laboratory for studying the influence of climate on runoff variability in general and riverine chemistry in particular. Interannual fluctuations in large-scale atmospheric circulation and associated precipitation and runoff can produce major disruptions in the "average"...
A model for trace metal sorption processes at the calcite surface: Adsorption of Cd2+ and subsequent solid solution formation
J.A. Davis, C. C. Fuller, A.D. Cook
1987, Geochimica et Cosmochimica Acta (51) 1477-1490
The rate of Cd2+ sorption by calcite was determined as a function of pH and Mg2+ in aqueous solutions saturated with respect to calcite but undersaturated with respect to CdCO3. The sorption is characterized by two reaction steps, with the first reaching completion within 24 hours. The second step proceeded...
