USGS Science⌕ Search

Geology topics

M. L. Tuttle

Publications and source records attributed to M. L. Tuttle.

16 recordsLinked to original sources
USGS1999

Environmental issues associated with fossil fuel resources; an evaluation of research opportunities for the U.S. Geological Survey's Energy Resources Program

Fossil fuel consumption in the United States has nearly tripled within the last 50 years (fig. 1), and is expected to continue increasing. As our knowledge and awareness of environmental consequences related to fossil fuel extraction and use grow, we as a nation, face the challenge of balancing our energy requirements with a desire for environmentally cleaner fuel. To help meet this challenge, the Energy Resources Program (ERP) of the Geologic Division (GD), U.S. Geological Survey (USGS) sponsored three internal workshops and a World Wide Web (WWW) workshop. The primary goal of these workshops was to identify those environmental issues that are related to fossil fuels, are national in scope, and are within the purview of the USGS as an earth-science government agency. Those issues so identified will be prioritized according to ERP's future research plan and according to the extent they provide an environmental framework for ERP's petroleum and coal assessments. The purpose of this paper is to provide the results of the internal and WWW workshops as proposed topics of research for future ERP work, delineate studies to answer the questions related to each proposed research area, and link the studies to the seven science goals of the Geologic Division. The information provided herein will be used in preparing the USGS Geologic Division's FY2000 prospectus and ERP's next five-year strategic plan. Acknowledgements. The authors wish to acknowledge information on ERP environmental projects provided by Les Magoon, Paul Lillis, Keith Kvenvolden, Tom Lorenson, and Bob Rosenbauer. Peter Schweitzer was instrumental in providing the software for the WWW workshop, Cheryl Adkisson for constructing the workshop web pages, and Laura Friedrich for constructing the web pages summarizing the internal workshops. Stan Mroczkowski, Jim Otton, Donna Read, and Dorothy Tanti provided notes of or logistical assistance for the internal workshops. This report reflects the collective input of numerous USGS managers and scientists their participation in the workshops is greatly appreciated.

Open-File Report↗
USGS1994

Six years of change in Lake Nyos, Cameroon, yield clues to the past and cautions for the future

The catastrophic release of gas from Lake Nyos, Cameroon, in 1986 caused substantial but incomplete mixing of the stratified water column. The post-release evolution of water-column structure has been monitored through April 1992. Changes began immediately after the event as rainfall and inflow brought dilute fluid into the surface layer. Inflow and surface mixing have gradually deepened the chemocline. The Total Dissolved Solids (TDS) values in the upper 40 m of the water column have dropped from a few hundred mg/kg just after the release to <100 mg/kg. The chemocline is presently strongest at 50 m depth; 5 m below this, the TDS = 570 mg/kg. From 55 to 150 m depth is a gentle gradient in which TDS reaches 920 mg/kg. Little change in water-column chemistry has occurred in this depth interval since the release. Between 150 m depth and lake bottom at 210 m depth, a strong secondary chemocline has formed. Temperature, CO 2 concentration ([CO 2 ]), and TDS have all increased in the deepest layer in response to recharge by warm, mineralized water, reaching values of 25.0°C, 320 mmol/kg, and 1800 mg/kg, respectively, 1 m above lake bottom. Considering all these changes in part as a “recovery” process, it is possible to construct a model of the pre-release water column. The data indicate that the pre-release chemocline was at least 50 m deep. Above the chemocline was a dilute layer containing a seasonal thermocline; below the chemocline was probably a gradient zone(s) with correlated increases in TDS and [CO 2 ] and a secondary chemocline near lake bottom. Maximum values of TDS and [CO 2 ] calculated for pre-release bottom water are 2400 mg/kg and 430 mmol/kg, respectively, based on tritium data. From this pre-release structure, a model of the gas release is proposed that is consistent with available chemical and observational data. An important feature of the model is that disruption of the pre-existing stratification was much more extensive than previously proposed, and even the deepest water layers were involved in the event. This model is not intended to limit possible gas release mechanisms, and thus complete re-establishment of pre-1986 water-column conditions is not a prerequisite for a future release. Spontaneous instability could occur at lake bottom in <20 yr if dissolved gas pressures continue to increase in this zone by 0.5–1 bar/yr as they have for the last 6 yr.

Lake Nyos↗
USGS1993

The analysis of forms of sulfur in ancient sediments and sedimentary rocks: comments and cautions

Assumptions commonly made during analysis of the amount of monosulfides [acid-volatile sulfides (AVS)] and disulfides in modern sediments, may not be valid for ancient sedimentary rocks. It is known that ferric iron can oxidize H2S during AVS analysis unless a reducing agent such as stannous chloride is added to the treatment. In addition, some monosulfides such as greigite and pyrrhotite require heat during the AVS analysis in order to dissolve completely. However, the use of heat and/or stannous chloride in the AVS treatment may partially dissolve disulfides and it is generally recommended that stannous chloride not be used in the AVS treatment for modern sediments. Most of the monosulfides are assumed to be recovered as AVS without the addition of stannous chloride. This study investigates the recovery of monosulfides during sulfur speciation analysis with application to ancient sedimentary rocks. Sulfur in samples containing naturally occurring greigite and mackinawite or pyrite was measured using variations of a common sulfur-speciation scheme. The sulfur-speciation scheme analyzes for monosulfide sulfur, disulfide sulfur, elemental sulfur, inorganic sulfate and organically bound sulfur. The effects of heat, stannous chloride and ferric iron on the amounts of acid-volatile sulfide and disulfide recovered during treatment for AVS were investigated. Isotopic compositions of the recovered sulfur species along with yields from an extended sulfur-speciation scheme were used to quantify the effects. Hot 6 N HCl AVS treatment recovers > 60% of the monosulfides as AVS in samples containing pure greigite and mackinawite. The remaining monosulfide sulfur is recovered in a subsequent elemental sulfur extraction. Hot 6 N HCl plus stannous chloride recovers 100% of the monosulfides as AVS. The addition of ferric iron to pure greigite and mackinawite samples during AVS treatment without stannous chloride decreased the amount of monosulfides recovered as AVS and, if present in great enough concentration, oxidized some of the AVS to a form not recovered in later treatments. The hot stannous chloride AVS treatments dissolve <5% of well-crystallized pyrite in this study. The amount of pyrite dissolved depends on grain size and crystallinity. Greigite in ancient sedimentary rocks was quantitatively recovered as AVS only with hot 6 N HCl plus stannous chloride. Hot 6 N HCl AVS treatment of these rocks did not detect any monosulfides in most samples. A subsequent elemental sulfur extraction did not completely recover the oxidized monosulfides. Therefore, the use of stannous chloride plus heat is recommended in the AVS treatment of ancient sedimentary rocks if monosulfides are present and of interest. All assumptions about the amount of monosulfides and disulfides recovered with the sulfur-speciation scheme used should be verified by extended sulfur-speciation and/or isotopic analysis of the species recovered. ?? 1993.

Chemical Geology↗
USGS1989

The evolution of thermal structure and water chemistry in Lake Nyos

We collected a time series of physical and chemical data to gain a better understanding of the dynamics of Lake Nyos. Measurements of water and gas chemistry, and temperature made during January, March, and May 1987 are compared to data taken in September 1986 just after the initial CO2 gas release. There is no pattern of change in overall heat content of the lake, although heat input to bottom waters (185-208 m) has occurred at a rate of 1600 mW m-2. This increase in heat content translates to a change from 23.38 to 24.12??C at 200 m and can be explained by geothermal heat flow and addition of thermal spring water. Concentrations of Ca2+, Mg2+, Na+, K+, Fe2+ and alkalinity have increased only in bottom waters. In situ lake processes such as sulfate and iron reduction are unable to account for the changes in alkalinity. Observed chemical changes are consistent with a scenario where slightly thermal soda water is being input to the bottom of the lake. Measurements of pCO2 at depth ranged from 18 to 28% of saturation and exhibited horizontal variability. Overall recharge of CO2 in bottom waters is negligible. Mainly because of increasing ion concentrations in bottom water, total stability of the water column increased 33% from 48,800 J m-2 in September 1986 to 64,700 J m-2 in May 1987. As long as CO2 concentrations remain the same, this level of stability is higher than could be disrupted by common limnologic or meteorologic processes. There is thermal and chemical evidence that a buildup of dissolved iron and CO2 in bottom waters must have preceded the August 1986 gas release. In addition, a survey of all crater lakes in Cameroon indicates that only Lakes Nyos and Monoun contain high concentrations of dissolved iron and CO2. Thus there is a low probability of any other Cameroonian lake releasing a substantial volume of CO2. ?? 1989.

Journal of Volcanology and Geothermal Research↗
USGS1988

The potential for catastrophic dam failure at Lake Nyos maar, Cameroon

The upper 40 m of Lake Nyos is bounded on the north by a narrow dam of poorly consolidated pyroclastic rocks, emplaced during the eruptive formation of the Lake Nyos maar a few hundred years ago. This 50-m-wide natural dam is structurally weak and is being eroded at an uncertain, but geologically alarming, rate. The eventual failure of the dam could cause a major flood (estimated peak discharge, 17000 m3/s) that would have a tragic impact on downstream areas as far as Nigeria, 108 km away. This serious hazard could be eliminated by lowering the lake level, either by controlled removal of the dam or by construction of a 680-m-long drainage tunnel about 65 m below the present lake surface. Either strategy would also lessen the lethal effects of future massive CO2 gas releases, such as the one that occurred in August 1986. ?? 1988 Springer-Verlag.

Bulletin of Volcanology↗
USGS1986

An analytical scheme for determining forms of sulphur in oil shales and associated rocks

An analytical scheme for determining various forms of sulphur in oil shales and associated rocks is presented. Acid-soluble sulphate, sulphur contained in monosulphide and in disulphide minerals, and organically-bound sulphur are all quantitatively recovered as separate fractions. Finely-ground oil-shale samples are treated in an inert atmosphere with 6 M hydrochloric acid to dissolve the acid-soluble sulphate minerals and form H 2 S from the decomposition of monosulphide minerals. The acid-soluble sulphate is precipitated as barium sulphate and the H 2 S is collected and weighed as silver sulphide. Disulphide minerals in the solid residue from the acid treatment are reduced by an acidified Cr(II) solution in an inert atmosphere, releasing the sulphide as H 2 S. The H 2 S is collected as silver sulphide. An Eschka fusion oxidizes and solubilizes all sulphur remaining within the Cr(II)-treated residue. This sulphate represents organically-bound sulphur and is collected as barium sulphate. The analytical procedures have been verified by using 57 Fe Mössbauer spectroscopy. Good agreement between the chemical and Mössbauer data substantiated the sequential removal of the forms of sulphur and also demonstrated the ability of Mössbauer spectroscopy to determine the absolute quantities of iron present in specific minerals.

Talanta↗
USGS1986

Geochemical variability of soils and biogeochemical variability of plants in the Piceance Basin, Colorado

Geochemical baselines for native soils and biogeochemical baselines for plants in the Piceance basin provide data that can be used to assess geochemical and biogeochemical effects of oil-shale development, monitor changes in the geochemical and biogeochemical environment during development, and assess the degree of success of rehabilitation of native materials after development. Baseline values for 52 properties in native soils, 15 properties in big sagebrush, and 13 properties in western wheatgrass were established. Our Study revealed statistically significant regional variations of the following properties across the basin: in soil&-aluminum, cobalt, copper, iron, manganese, sodium, nickel, phosphorus, lead, scandium, titanium, vanadium, zinc, organic and total carbon, pH, clay, dolomite, sodium feldspar, and DTPA-extractable calcium, cadmium, iron, potassium, manganese, nickel, phosphorus, yttrium, and zinc; in big sagebrush-barium, calcium, copper, magnesium, molybdenum, sodium, strontium, zinc, and ash; and in western wheatgrass-boron, barium, calcium, magnesium, manganese, molybdenum, strontium, zinc, and ash. These variations show up as north-south trends across the basin, or they reflect differences in elevation, hydrology, and soil parent material. Baseline values for properties that do not have statistically significant regional variations can be represented by geometric means and deviations calculated from all values within the basin. Chemical and mineralogical analyses of soil and chemical analyses of western wheatgrass samples from Colorado State University's experimental revegetation plot at Anvil Points provide data useful in assessing potential effects on soil and plant properties when largescale revegetation operations begin. The concentrations of certain properties are related to the presence of topsoil over spent shale in the lysimeters. In soils, calcium, fluorine, lithium, magnesium, sodium, phosphorus, strontium, carbonate and total carbon, and DTPA-extractable boron, copper, iron, magnesium, and nickel have lower concentrations in topsoil than in the spent oil shale; whereas, silicon, titanium, ytterbium, clay, quartz, and DTPA-extractable potassium have greater concentrations in the topsoil than in the spent oil shale. In western wheatgrass, molybdenum has a lower concentration in grasses growing on the topsoil than in grasses on the spent oil shale; whereas, barium, calcium, manganese, strontium, zinc, and ash have greater concentrations in grasses growing on the topsoil than on the spent oil shale. When compared to baseline values, soils in the revegetation plot are significantly higher in concentrations of lead, zinc, organic and total carbon, and DTP A-extractable cadmium, iron, manganese, nickel, phosphorus, and zinc. Whereas, western wheatgrass grown within the revegetation plot has concentrations which fall within the baseline values established in the regional study. The equations used in predicting concentrations of elements in plants from native and altered sites are cumbersome because of the large number of variables required to adequately predict expected concentrations and are of limited use because many explained only a small proportion of the total variation.

Professional Paper↗
USGS1983

Major and trace elements in Mahogany zone oil shale in two cores from the Green River Formation, piceance basin, Colorado

The Parachute Creek Member of the lacustrine Green River Formation contains thick sequences of rich oil-shale. The richest sequence and the richest oil-shale bed occurring in the member are called the Mahogany zone and the Mahogany bed, respectively, and were deposited in ancient Lake Uinta. The name "Mahogany" is derived from the red-brown color imparted to the rock by its rich-kerogen content. Geochemical abundance and distribution of eight major and 18 trace elements were determined in the Mahogany zone sampled from two cores, U. S. Geological Survey core hole CR-2 and U. S. Bureau of Mines core hole O1-A (Figure 1). The oil shale from core hole CR-2 was deposited nearer the margin of Lake Uinta than oil shale from core hole O1-A. The major- and trace-element chemistry of the Mahogany zone from each of these two cores is compared using elemental abundances and Q-mode factor modeling. The results of chemical analyses of 44 CR-2 Mahogany samples and 76 O1-A Mahogany samples are summarized in Figure 2. The average geochemical abundances for shale (1) and black shale (2) are also plotted on Figure 2 for comparison. The elemental abundances in the samples from the two cores are similar for the majority of elements. Differences at the 95% probability level are higher concentrations of Ca, Cu, La, Ni, Sc and Zr in the samples from core hole CR-2 compared to samples from core hole O1-A and higher concentrations of As and Sr in samples from core hole O1-A compared to samples from core hole CR-2. These differences presumably reflect slight differences in depositional conditions or source material at the two sites. The Mahogany oil shale from the two cores has lower concentrations of most trace metals and higher concentrations of carbonate-related elements (Ca, Mg, Sr and Na) compared to the average shale and black shale. During deposition of the Mahogany oil shale, large quantities of carbonates were precipitated resulting in the enrichment of carbonate-related elements and dilution of most trace elements as pointed out in several previous studies. Q-mode factor modeling is a statistical method used to group samples on the basis of compositional similarities. Factor end-member samples are chosen by the model. All other sample compositions are represented by varying proportions of the factor end-members and grouped as to their highest proportion. The compositional similarities defined by the Q-mode model are helpful in understanding processes controlling multi-element distributions. The models for each core are essentially identical. A four-factor model explains 70% of the variance in the CR-2 data and 64% of the O1-A data (the average correlation coefficients are 0. 84 and 0. 80, respectively). Increasing the number of factors above 4 results in the addition of unique instead of common factors. Table I groups the elements based on high factor-loading scores (the amount of influence each element has in defining the model factors). Similar elemental associations are found in both cores. Elemental abundances are plotted as a function of core depth using a five-point weighted moving average of the original data to smooth the curve (Figure 3 and 4). The plots are grouped according to the four factors defined by the Q-mode models and show similar distributions for elements within the same factor. Factor 1 samples are rich in most trace metals. High oil yield and the presence of illite characterize the end-member samples for this factor (3, 4) suggesting that adsorption of metals onto clay particles or organic matter is controlling the distribution of the metals. Precipitation of some metals as sulfides is possible (5). Factor 2 samples are high in elements commonly associated with minerals of detrital or volcanogenic origin. Altered tuff beds and lenses are prevalent within the Mahogany zone. The CR-2 end-member samples for this factor contain analcime (3) which is an alteration product within the tuff beds of the Green River Formation. Th

Conference Paper↗