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G.I. Smith

Publications and source records attributed to G.I. Smith.

18 recordsLinked to original sources
USGS2017

Is Obsidian Hydration Dating Affected by Relative Humidity?

Experiments carried out under temperatures and relative humidities that approximate ambient conditions show that the rate of hydration of obsidian is a function of the relative humidity, as well as of previously established variables of temperature and obsidian chemical composition. Measurements of the relative humidity of soil at 25 sites and at depths of between 0.01 and 2 m below ground show that in most soil environments, at depths below about 0.25 m, the relative humidity is constant at 100%. We have found that the thickness of the hydrated layer developed on obsidian outcrops exposed to the sun and to relative humidities of 30-90% is similar to that formed on other portions of the outcrop that were shielded from the sun and exposed to a relative humidity of approximately 100%. Surface samples of obsidian exposed to solar heating should hydrate more rapidly than samples buried in the ground. However, the effect of the lower mean relative humidity experiences by surface samples tends to compensate for the elevated temperature, which may explain why obsidian hydration ages of surface samples usually approximate those derived from buried samples.

Quaternary Research↗
USGS2017

Quaternary deposits in southwestern Afghanistan

Geologic evidence in the closed Seistan Basin of southwestern Afghanistan and adjacent parts of Iran and Pakistan indicates that a lake as much as 65,000 sq km in size occupied this closed depression during Pleistocene time. The deposits consist mostly of lacustrine silt and clay and have a maximum observed thickness of about 250 m. A layer of alluvial gravels overlies the sequence. The deposits are probably early or middle Pleistocene in age; they are old enough to have sustained nearly 300 m of erosion over large areas but are not faulted or detectably folded in the central part of the basin although they are upwarped along the west edge of the basin. Sand dunes cover extensive areas of the basin. Dune orientation shows that the strong surface winds enter the basin blowing toward the south-southeast and then are deflected to the east, apparently as a response to mountains bordering the basin on its south side. The Gawdezereh, a large deflation depression, may be a result of an augmented excavation ability of winds that oc urs where turbulence is created along a zone of deflection.

Quaternary Research↗
USGS2017

Paleohydrologic regimes in the southwestern Great Basin, 0-3.2 my ago, compared with other long records of "gobal" climate

Nine distinct paleohydrologic regimes in the southwestern Great Basin over the last 3.2 my are recorded by the lacustrine deposits in KM-3, a 930-m core from Searles Lake, California. These are characterized as being "wet," "intermediate," or "dry" (like today). Excepting the present incomplete regime, each lasted 0.12 to 0.76 my. Major regime changes 0.01, 0.13, 0.6, and 2.5 my ago appear to coincide with recognized changes in global ice-sheet histories as represented by 18O and other records from marine sediments, but comparable changes 0.3, 1.0, 1.3, and 2.0 my ago do not appear to coincide closely with comparable perturbations in ice-sheet histories. However, all regime boundaries (during the last 1.75 my) coincide closely in time with changes in sea-surface temperatures in the tropical Atlantic, and many coincide with other deep-sea and continental paleoclimatic boundaries.The average duration of these paleohydrologic regimes was about 0.4 my (standard deviation, 0.2 my or less, depending on assumptions), and it is suggested that the regime boundaries reflect times of change in global(?) sea-surface temperatures, possibly controlled in part by the Earth's 413,000-yr orbital eccentricity cycle. During the wettest and driest regimes in the Searles Lake area, lake levels were not sufficiently affected by the 23,000-, to 42,000-, or 100,000-yr climate cycles related to high-latitude ice-sheet fluctuations to produce changes in the lacustrine sediment character. During intermediate regimes, however, when lacustrine sedimentation in this area was more sensitive to climate, the sediments, in KM-3, record lake fluctuations with average frequencies near those of the ice sheets. This seems to indicate that the high-latitude ice-sheet fluctuations caused local climatic perturbations but did not dominate the hydrologic component of climate in this area. Other lacustrine deposits in the southwestern Great Basin of California and Nevada have ages comparable in part to those of the wet to intermediate regimes indicated by KM-3, and they may all be products of finite periods when lake expansion, alluvial fan growth, increased spring discharge, and fluvial deposition were promoted in this area by widespread wet climates. Glacier expansion in the Sierra Nevada may also have been primarily an expression of, and in phase with, these wet regimes. ?? 1984.

Quaternary Research↗
USGS2002

Stable isotope composition of waters in the Great Basin, United States 1. Air-mass trajectories

Isentropic trajectories, calculated using the NOAA/Climate Monitoring and Diagnostics Laboratory's isentropic transport model, were used to determine air-parcel origins and the influence of air mass trajectories on the isotopic composition of precipitation events that occurred between October 1991 and September 1993 at Cedar City, Utah, and Winnemucca, Nevada. Examination of trajectories that trace the position of air parcels backward in time for 10 days indicated five distinct regions of water vapor origin: (1) Gulf of Alaska and North Pacific, (2) central Pacific, (3) tropical Pacific, (4) Gulf of Mexico, and (5) continental land mass. Deuterium (??D) and oxygen-18 (??18O) analyses were made of precipitation representing 99% of all Cedar City events. Similar analyses were made on precipitation representing 66% of the precipitation falling at Winnemucca during the same period. The average isotopic composition of precipitation derived from each water vapor source was determined. More than half of the precipitation that fell at both sites during the study period originated in the tropical Pacific and traveled northeast to the Great Basin; only a small proportion traversed the Sierra Nevada. The isotopic composition of precipitation is determined by air-mass origin and its track to the collection station, mechanism of droplet formation, reequilibration within clouds, and evaporation during its passage from cloud to ground. The Rayleigh distillation model can explain the changes in isotopic composition of precipitation as an air mass is cooled pseudo-adiabatically during uplift. However, the complicated processes that take place in the rapidly convecting environment of cumulonimbus and other clouds that are common in the Great Basin, especially in summer, require modification of this model because raindrops that form in the lower portion of those clouds undergo isotopic change as they are elevated to upper levels of the clouds from where they eventually drop to the ground.

Journal of Geophysical Research D: Atmospheres↗
USGS2002

Stable isotope compositions of waters in the Great Basin, United States 3. Comparison of groundwaters with modern precipitation

Groundwater samples from wells and springs, scattered over most of the Great Basin province, were collected and analyzed for their isotopic makeup. They were augmented by previously published isotopic data on groundwaters from southeast California and by several hundred unpublished isotopic analyses. The ratio of 2H (deuterium, D) to 1H, in water samples from valleys in parts of California, Idaho, Nevada, Oregon, and Utah, are here compared with the winter, summer, and annual isotopic compositions of precipitation falling in or near the sampled areas. The main goal of this study was to identify basins where the groundwaters have isotopic compositions that are "lighter" (depleted in the heavier isotope, D) relative to modern winter precipitation. Where these basins do not adjoin substantially higher terrain, we consider those light groundwaters to be of Pleistocene age and thus more than 10,000 years old. Where the groundwater is 10 to 19??? lighter than local winter precipitation, we consider it to be possibly an indication of Pleistocene water; where the ??D makeup is >20??? lighter, we consider it to be probably Pleistocene water. More than 80 sites underlain by waters of possible or probable Pleistocene age were identified.

Journal of Geophysical Research D: Atmospheres↗
USGS1994

Deuterium content of water from wells and perennial springs, southeastern California

The areal distribution of the concentrations of the stable isotopes deuterium and oxygen-18 in ground water in southeastern California is depicted and evaluated in this report. The deuterium content of about 300 ground-water samples and the oxygen-18 content of 101 of these samples are presented. Thirty-two of the samples were collected by the U.S. Geological Survey in 1977–78 as part of a study to determine the mineral and brine potential of playa lakes in selected basins in southeastern California. Most of the remaining samples were collected during the winters and springs of 1981 and 1982 as part of the Climate Change Program of the Geological Survey. Selected additional samples were collected through 1986. Stable-isotope data from three previous studies also have been included. These data are for 19 samples from the Coso thermal area east of the southern Sierra Nevada (Fournier and Thompson, 1980, tables 1,2), 5 samples from areas in Nevada just east of Death Valley (Winograd and Friedman, 1972, table 1), and 9 samples from the Imperial Valley (Coplen, 1971, table 1). Also presented for comparison are weighted averages of deuterium content of recent precipitation collected for this report at 32 stations over the 7-year period from April 1982 to April 1989 (Irving Friedman and G.I. Smith, U.S. Geological Survey, written commun., 1989).

Hydrologic Atlas↗
USGS1991

Anomalous folds associated with the east-central part of the Garlock Fault, southeast California

The east-central part of the left-lateral Garlock fault, in southeast California, is associated with three broad folds that trend and plunge northeast. The folds, which lie north, south, and astride the fault, postdate deposition of alluvial gravels that at one time formed a continuous northwest-sloping fan; the gravels rest conformably on lake beds that contain the Lava Creek B ash bed (0.62 Ma). The anticline, named after Christmas Canyon, has vertical relief of as much as 100 m. Topographic profiles suggest that the gravels exposed along the synclinal troughs to its southeast (Pilot Knob Valley syncline) and northwest (Teagle Wash syncline) lie at about the same elevations as they did when part of the originally active fan, implying that the synclines are passive results of the anticline development. If so, the original slope of the middle Pleistocene alluvial sediment sheet was about 0.6° northwest. The age and dimensional controls allow calculation of the rates of tilting and horizontal shortening. Corrected tilting rates vary from about 2.5° to 4.7°/m.y.; the total shortening of about 7.5 m developed at a minimum rate of 12.5 m/m.y.

California↗
USGS1990

Chronology of expansion and contraction of four great Basin lake systems during the past 35,000 years

During the past 35,000 years, Lake Bonneville, Lake Russell, and Lake Searles underwent a major period of lake-level change. The lakes were at moderate levels or dry at the beginning of the period and seem to have achieved highstands between about 15,000 and 13,500 yr B.P. The rise of Lake Lahontan was gradual but not continuous, in part because of topographic constraints (intrabasin spill). Lake Lahontan also had an oscillation in lake level at 15,500 yr B.P. Radiocarbon-age estimations for materials that were deposited in the lake basins indicate that Lake Bonneville rose more or less gradually from 32,000 yr B.P., and had major oscillations in level between 23,000 and 21,000 yr B.P. and between 15,250 and 14,500 yr B.P. Lake Russell and Lake Searles had several major oscillations in lake level between 35,000 and 14,000 yr B.P. The timing and exact magnitude of the oscillations are difficult to decipher but both lakes may have achieved multiple highstand states. All four lakes may have had nearly synchronous recessions between about 14,000 and 13,500 yr B.P. After the recessions, the lakes seem to have temporarily stabilized or experienced a minor increase in size between about 11,500 and 10,000 yr B.P. These data provide circumstantial evidence that the Younger Dryas Event affected climate on at least a hemispheric scale. During the Holocene, the four lakes remained at low levels, and small oscillations in lake level occurred. An important aspect of the lake-level data is the accompanying expansion of lake-surface area at the time of the last highstand. Lake Bonneville and Lake Lahontan had surface areas about 10 times larger than their mean-historical reconstructed areas whereas Lake Russell and Lake Searles had surface areas about 5 times larger than their mean-historical reconstructed areas. Differences in the records of effective wetness may have been due to the locations of the basins relative to the position of the jetstream, or they may have resulted from lake/atmosphere feedback processes.

California, Idaho, Nevada, Oregon↗
USGS1987

Studies of Quaternary saline lakes-III. Mineral, chemical, and isotopic evidence of salt solution and crystallization processes in Owens Lake, California, 1969-1971

As a consequence of the 1969–1970 flooding of normally dry Owens Lake, a 2.4-m-deep lake formed and 20% of the 2-m-thick salt bed dissolved in it. Its desiccation began August 1969, and salts started crystallizing September 1970, ending August 1971. Mineralogic, brine-composition, and stable-isotope data plus field observations showed that while the evolving brine composition established the general crystallization timetable and range of primary and secondary mineral assemblages, it was the daily, monthly, and seasonal temperature changes that controlled the details of timing and mineralogy during this depositional process. Deuterium analyses of lake brine, interstitial brine, and hydrated saline phases helped confirm the sequence of mineral crystallizations and transformations, and they documented the sources and temperatures of waters involved in the reactions. Salts first crystallized as floating rafts on the lake surface. Natron and mirabilite, salts whose solubilities decrease greatly with lowering temperatures, crystallized late at night in winter, when surface-water temperatures reached their minima; trona, nahcolite, burkeite, and halite, salts with solubilities less sensitive to temperature, crystallized during the afternoon in summer, when surface salinities reached their maxima. However, different temperatures were generally associated with crystallization (at the surface) and accumulation (on the lake floor) because short-term temperature changes were transmitted to surface and bottom waters at different rates. Consequently, even when solubilities were exceeded at the surface, salts were preserved or not as a function of bottom-water temperatures. Halite, a nearly temperature-insensitive salt, was always preserved. Monitoring the lake-brine chemistry and mineralogy of the accumulating salts shows: (1) An estimated 0.9 × 10 6 tons of CO 2 was released to the atmosphere or consumed by the lake's biomass prior to most salt crystallization. (2) After deposition, some salts reacted in situ to form other minerals in less than one month, and all salts (except halite) decomposed or recrystallized at least once in response to seasons. (3) Warming in early 1971 caused solution of all the mirabilite and some of the natron deposited a few months earlier, a deepening of the lake (though the lake-surface lowered), and an increase in dissolved solids. (4) Phase and solubility-index data suggest that at the close of desiccation, Na 2 CO 3 ·7H 2 O, never reported as a mineral, could have been the next phase to crystallize.

Geochimica et Cosmochimica Acta↗
USGS1984

Late quaternary sediments, minerals, and inferred geochemical history of Didwana Lake, Thar Desert, India

Variations in clastic sediment texture, mineralogy of both evaporites formed at the surface and precipitates formed below the lake floor, and the relative chemical activities of the major dissolved components of the chemical precipitates, have allowed reconstruction of the history of salinity and water-level changes in Didwana Lake, Thar Desert, India. Hypersaline conditions prevailed at about the Last Glacial Maximum, with little evidence of clastic sediments entering the lake. Between ca. 13,000 and 6000 B.P. the lake level fluctuated widely, the lake alternately hypersaline and fresh, and clastic sediments were delivered to the lake at a low rate. Deep-water conditions occurred ca. 6000 B.P. and clastic influx increased abruptly. The water level dropped towards 4000 B.P. when the lake dried briefly. Since 4000 B.P. the lake has been ephemeral with a lowered rate of sedimentation and mildly saline conditions rather like those of today. This sequence of changes documented in the lake parallels changes in vegetation recorded in published pollen diagrams from both the Thar and the Arabian Sea. Correlation of the various lines of evidence suggests that the climate of the Last Glacial Maximum at Didwana was dry and windy with a weak monsoon circulation. The monsoon was re-established between ca. 13,000 and a little before 6000 B.P., and, when winter rainfall increased ca. 6000 B.P., the lake filled to its maximum depth.

Didwana Lake, Thar Deser↗
USGS1983

Chlorine-36 dating of saline sediments: Preliminary results from Searles Lake, California

Measurements have been made of the ratios of chlorine-36 to chlorine in five halite samples from Searles Lake sediments, previously dated by carbon-14, thorium-230, and magnetostratigraphic techniques. The ages calculated from the chlorine ratios are generally concordant with those from the other methods, implying the constancy of the chlorine input ratio over the last million years.

California↗
USGS1980

Palaeomagnetic polarity in a 930-m core from Searles valley, California

Palaeomagnetic polarity to the base of the Mammoth subchron (3.15 Myr) has been determined in a core of lacustrine sediments from ancient Searles Lake. The magnetostratigraphy provides a chronological framework for palynological, tephrochronological and palaeoecological studies of the core. Five zones of inclination are found that are not in the polarity time scale of Mankinen and Dalrymple. Three of the zones may correlate with K-Ar-dated lava flows of that polarity elsewhere, and the other two may be new discoveries. ?? 1980 Nature Publishing Group.

Nature↗
USGS1976

Studies of quaternary saline lakes-II. Isotopic and compositional changes during desiccation of the brines in Owens Lake, California, 1969-1971

Owens Lake is an alkaline salt lake in a closed basin in southeast California. It is normally nearly dry, but in early 1969, an abnormal runoff from the Sierra Nevada flooded it to a maximum depth of 2·4 m. By late summer of 1971, the lake was again nearly dry and the dissolved salts recrystallized. Changes in the chemistry, pH, and deuterium content were monitored during desiccation. During flooding, salts (mostly trona, halite, and burkeite) dissolved slowly from the lake floor. Their concentration in the lake waters increased as evaporation removed water and salts again crystallized, but winter temperatures caused precipitation of some salts and the following summer warming caused their solution, resulting in seasonal variations in the concentration patterns of some ions. The pH values (9·4–10·4) changed with time but showed no detectable diurnal pattern. The deuterium concentration increased during evaporation and appeared to be in equilibrium with vapor leaving the lake according to the Rayleigh equation. The effective α(D/H in liquid/D/H in vapor) decreased as salinity increased; the earliest measured value was 1·069 [as total dissolved solids (TDS) of lake waters changed from 136,200 to 250,400 mg/1]and the last value (calc.) was 1·025 (as TDS changed from 450,000 to 470,300 mg/1). Deuterium exchange with the atmosphere was apparently small except during late desiccation stages when the isotopic contrast became great. Eventually, atmospheric exchange, combined with decreasing α and lake size and increasing salinity, stopped further deuterium concentration in the lake. The maximum contrast between atmospheric vapor and lake deuterium contents was about 110%.

Geochimica et Cosmochimica Acta↗
USGS1972

Studies of quaternary saline lakes-I. Hydrogen isotope fractionation in saline minerals

Borax, gaylussite, nahcolite and trona were synthesized in aqueous solution at temperatures ranging from 8° to 35°C. Except for borax, deuterium was always depleted in these hydrated minerals relative to the solutions from which they were crystallized. In borax, no significant fractionation was found. The fractionation factor of D H "> DH for the trona-water system exhibited a marked temperature dependence. By combining the deuterium contents of trona and the solution from which trona was crystallized, the following thermometer scale was obtained: In ( D H ) trona ( D H )water = 1.420 × 10 4 T 2 + 23.56 T "> (DH) trona(DH)water =1.420 × 104T2+23.56T (1) An attempt to establish a geothermometer based on C 13 C 12 "> C13C12 fractionation between carbonate minerals and carbonate ions in aqueous solution was not successful.

Geochimica et Cosmochimica Acta↗
USGS1972

Deuterium content of snow as an index to winter climate in the Sierra Nevada area

The winter of 1968-69 produced two to three times the amount of precipitation in the Sierra Nevada area, California and Nevada, as the winter of 1969-70. The deuterium content in snow cores collected at the end of each winter at the same sites, which represents the total snowfall of each interval, shows a depletion in 1968-69 of approximately 20 per mil. The higher snowfall in 1968-69 and the depletion of deuterium can be explained by an uncommonly strong westward flow of cold air over and down the western slopes of the Sierras, which interacted with an eastward flow of moist Pacific air that overrode and mixed with the cold air; this resulted in precipitation that occurred in greater than normal amounts and at a lower than normal temperature. Pluvial periods of the Pleistocene may have had the same shift in air-mass trajectory as the wet 1968-69 year. Snow cores collected in the normal 1970-71 winter have deuterium concentrations that resemble those of the normal 1969-70 winter. Small and nonsystematic differences in samples from these two normal winters are due to variations in climatic character as well as to factors inherent in the sampling sites.

California, Nevada↗
USGS1970

Deuterium content of snow cores from Sierra Nevada area

The relative deuterium content was measured on 37 snow cores collected in April 1969 in the Sierra Nevada. The deuterium content varies inversely with altitude of collection (approximately 40 per mil per 1000 meters) but is unrelated to latitude. The altitude relationship is particularly well defined west of the crest of the range but is not well defined east of the crest. However, samples from east of the crest tend to be depleted by about 10 to 15 per mil relative to samples collected at the same elevation west of the crest. We propose that the deuterium content of snow cores, collected so as to include the total winter's precipitation, can be used as a climatic indicator to compare the climate of one winter with that of another.

California, Nevada↗