Correlation of the Rockland ash bed,a 400,000-year-old stratigraphic marker in northern California and western Nevada,and implications for middle Pleistocene paleogeography of central California

Outcrops of an ash bed at several localities in northern California and western Nevada belong to a single air-fall ash layer, the informally named Rockland ash bed, dated at about 400,000 yr B.P. The informal Rockland pumice tuff breccia, a thick, coarse, compound tephra deposit southwest of Lassen Peak in northeastern California, is the near-source equivalent of the Rockland ash bed. Relations between initial thickness of the Rockland ash bed and distances to eruptive source suggest that the eruption was at least as great as that of the Mazama ash from Crater Lake, Oregon. Identification of the Rockland tephra allows temporal correlation of associated middle Pleistocene strata of diverse facies in separate depositional basins. Specifically, marine, littoral, estuarine, and fluvial strata of the Hookton and type Merced formations correlate with fluvial strata of the Santa Clara Formation and unnamed alluvium of Willits Valley and the Hollister area, in northwestern and west-central California, and with lacustrine beds of Mohawk Valley, fluvial deposits of the Red Bluff Formation of the eastern Sacramento Valley, and fluvial and glaciofluvial deposits of Fales Hot Spring, Carson City, and Washoe Valley areas in northeastern California and western Nevada. Stratigraphic relations of the Rockland ash bed and older tephra layers in the Great Valley and near San Francisco suggest that the southern Great Valley emerged above sea level about 2 my ago, that its southerly outlet to the ocean was closed sometime after about 2 my ago, and that drainage from the Great Valley to the ocean was established near the present, northerly outlet in the vicinity of San Francisco Bay about 0.6 my ago.     

Possible ecological and environmental significance of the predominance of even-carbon number C20-C30n-alkanes

Even-carbon number C₂₂-C₂₈n-alkanes, are present in higher concentrations than their C₂₁-C₂₉ odd-carbon number homologs in an organic-rich rock of Mississippian (ca. 310 × 10⁶-yr-old) age, which contains algae-like remnants. Environmental indicators associated with this organic-rich rock permitted environmental comparison with ancient and modern environments that contain n-alkanes which exhibit similar distributions. The results of these comparisons suggest that even-carbon number n-alkanes are preferentially produced in highly saline, carbonate environments where aerobic and anaerobic bacteria have subsisted on the remains of blue-green algae.     

Use of oxygen isotope ratios in correlation of tuffs,East Rudolf Basin,northern Kenya

Oxygen isotope determinations were made using CoF₃ to extract oxygen from 27 volcanic glass samples from the East Rudolf Basin, northern Kenya. Results show that the older tuffs are progressively enriched in¹⁸O and that this index can be used in the correlation of volcanic ash units. This method could not distinguish individual samples from the youngest units studied because their ranges of δ¹⁸O overlap. The δ¹⁸O values for the shards in the Tulu Bor Tuff, the KBS Tuff, the Koobi Fora Tuff and the Chari Tuff range from 14.5 to 16.4, from 8.9 to 9.5, from 6.6 to 7.0 and from 7.0 to 7.2, respectively, in decreasing age. Determinations from pumice cobbles are consistently higher than the above values.     

Consumer spatial choice strategies: A comparative study of some alternative behavioural spatial shopping models

The purpose of this paper is to outline a conceptual model of consumer spatial decision making and choice behaviour and to investigate the use of various combination rules of consumer's evaluations of attributes of shopping centres to predict spatial choice behaviour.The research findings indicate that the linear combination rules perform as well as the multiplicative rules and that both types of rules perform quite acceptably. The paper concludes by discussing some implications for future research on spatial decision making and choice.     

Analysis of the long-term precipitation series at Athens,Greece

In this paper, the characteristics of the long-term precipitation series at Athens (1858–1985) have been statistically analyzed. This study covers both the history and the analysis of the data. The ten-year mean amounts, the monthly and annual amounts averaged over the intervals 1858–1890, 1891–1985, 1951–1980, 1858–1985, the mean number of hours of precipitation and the precipitation intensity are given. The analysis of long-term time series of climatic data (in particular precipitation) is a useful tool for the study of past climate. Different statistical techniques are used in order to depict monthly, seasonal and annual variations, as well as trends, periodicities and recurrence intervals of the amount, intensity and number of precipitation days. The analysis reveals many interesting characteristics. These characteristics of the precipitation regime are extended to a time scale from seasonal variation to a semi-secular trend. The study of such long-term series may be helpful not only in practical applications of rainfall, but also for explaining the possible physical or anthropogenic mechanisms of climatic fluctuations and tendencies. The series of precipitation at Athens is one of the longest in south-eastern Europe.     

Recycling in the metals industry

In 1990, scrap was a major feedstock component of U.S. metals production. Steel scrap represented 56% of raw steel production, old lead scrap was 66% of total lead production, and purchased aluminum scrap represented 37% of total production. Copper scrap makes up 44% of total U.S. copper consumption annually. Although some recycling operations, such as past (but now obsolete) lead-acid battery breaking and the use of high salt fluxes on aluminum drosses have created environmental problems, the recovery of obsolete autos, cast or extruded products, appliances, lead-acid batteries, beverage containers, and drosses represents major environmental benefits in terms of reduced litter, landfill wastes, and energy savings. Evolving technologies, marketing concepts, and regulations promise even higher levels of recycling in the future. The cumulative amounts of aluminum, copper, lead, and ferrous scrap that would have had to be absorbed by our environment as discards during the period 1965–1990 had they not been recycled totaled more than 2.2 billion tons, just for the four metal groups. Concurrently, huge energy savings were realized and environmental benefits achieved through reduced emissions associated with generating that energy.Correspondence should be directed to: Earle B. Amey, U.S. Geological Survey, National Center 983, Reston, Virginia 20192.     

Influence of HCl/HF treatment on organic matter in aquifer sediments: A Rock-Eval pyrolysis study

Rock–Eval pyrolysis is increasingly used for the routine characterization of natural organic matter in soils and sediments. In this work the bulk composition of sedimentary organic matter (SOM) in sandy aquifer sediments is studied, as well as purified samples (isolation of SOM) by HCl/HF treatment. This treatment is necessary to avoid detection limit problems for samples with low SOM contents, but the results presented here indicate that this treatment influences the organic geochemistry of the aquifer sediment samples. The FID and CO₂/CO pyrograms show a shift of 10–40 °C of the major peak to a lower temperature. Organic matter alteration or removal of components containing O-bearing groups may explain this. It is also suggested that destruction of the mineral matrix may lead to the reduced retention of the material. For the change of the CO₂/CO pyrograms of the RC fraction only organic matter alteration seems to be likely. Concentrated organic matter samples may also accelerate the release of exothermic energy and influence the pyrograms. Results indicate that the organic matter concentration in the sample influences the measured total organic matter (TOM) content and the T_max of the FID pyrogram, while the sample loading (absolute organic matter amount) up to 80 mg in the Rock–Eval apparatus does not. The FID pyrograms can be deconvoluted into four subpeaks, which allows comparison of samples at various depths. Rock–Eval pyrolysis may only be routinely applied to characterize SOM in aquifer sediments when such systematic and analytical phenomena are taken into account.     

Three-dimensional geostatistical inversion of flowmeter and pumping test data

We jointly invert field data of flowmeter and multiple pumping tests in fully screened wells to estimate hydraulic conductivity using a geostatistical method. We use the steady-state drawdowns of pumping tests and the discharge profiles of flowmeter tests as our data in the inference. The discharge profiles need not be converted to absolute hydraulic conductivities. Consequently, we do not need measurements of depth-averaged hydraulic conductivity at well locations. The flowmeter profiles contain information about relative vertical distributions of hydraulic conductivity, while drawdown measurements of pumping tests provide information about horizontal fluctuation of the depth-averaged hydraulic conductivity. We apply the method to data obtained at the Krauthausen test site of the Forschungszentrum Jülich, Germany. The resulting estimate of our joint three-dimensional (3D) geostatistical inversion shows an improved 3D structure in comparison to the inversion of pumping test data only.