Todd Dallegge | University of Northern Colorado (original) (raw)

Papers by Todd Dallegge

Maximum magnitude Closest distance to rupture 9X-9% 75 km 8 40-50 km 7-7X >40 km 7X? 40 km 7? 40 ... more Maximum magnitude Closest distance to rupture 9X-9% 75 km 8 40-50 km 7-7X >40 km 7X? 40 km 7? 40 km 7X-7% 40 km 7 % 60 km 6 130 km 7 % 40 km Average return period 600-800 yr unknown unknown > 10,000 yr ? unknown 1,000 yr ? unknown unknown unknown

at Austin where he has been active in coalbed methane research for more than 10 years. His curren... more at Austin where he has been active in coalbed methane research for more than 10 years. His current coalbed methane research interests include the application of integrated hydrogeologic exploration techniques and Microbially Enhanced Coalbed Methane (MECoM pronunced "mee-com"). Andrew has published numerous coalbed methane research papers and abstracts, taught short courses nationally and internationally, and is fortunate to have received several best paper awards for his research efforts.

Thesis (Ph.D.) University of Alaska Fairbanks, 2002The 40Ar/39Ar dating method is a useful tool i... more Thesis (Ph.D.) University of Alaska Fairbanks, 2002The 40Ar/39Ar dating method is a useful tool in addressing problems concerning stratigraphic distribution of rock units. This tool is used where previously K-Ar-dated units are problematic, and where further chronostratigraphic control is needed for lavas of the Central Plateau Member (CPM) of the Plateau Rhyolite in Yellowstone National Park and volcanic ash dispersed in the sedimentary units of the Kenai Group in Cook Inlet Basin. Sanidine 40Ar/39Ar ages for CPM rhyolite lavas indicate that xenocrysts, excess argon, and incomplete degassing affected the K-Ar age interpretations. With the 40Ar/39Ar dating method these effects are removed, revealing four apparent eruptive episodes at approximately 135, 122, 107, and 90 ka. The 40Ar/ 39Ar eruption ages are 10's ky younger than U-Th ages from zircon indicating significant residence time of the CPM magma chamber prior to eruption. 40Ar/39Ar dating using multiple analytical runs and...

The Mountain Geologist, 2003

The Journal of Geology, 2001

Water samples from the Colorado River and its tributaries provide a present‐day 87Sr/86Sr profile... more Water samples from the Colorado River and its tributaries provide a present‐day 87Sr/86Sr profile of the Colorado River system from Moab, Utah, down to the Gulf of California. 87Sr/86Sr values around 0.7097 are prevalent above the Grand Canyon, and values of 0.7103 or higher are observed below the Grand Canyon. 87Sr/86Sr values close to the seawater ratio of 0.70917 are seen near the Colorado River delta. All tributaries except the Green River contribute Sr that is lower in 87Sr/86Sr than the main Colorado. The cause of the increase in 87Sr/86Sr through the Grand Canyon and Lake Mead area has not been found. Samples of carbonate and gypsum from the lower lacustrine member of the mid‐Miocene to Pliocene Bidahochi Formation in northern Arizona yield average 87Sr/86Sr of 0.70972. This agrees quite well with weighted averages of present‐day Colorado system rivers that flow into the area, which can be computed at 0.70972 or 0.70984, depending on assumptions. This correspondence argues that the present‐day rivers serve as a model for similar rivers that contributed to Bidahochi Formation deposition. Samples from middle and upper members of the Bidahochi Formation, younger than ∼6 Ma, do not fit this pattern so well. The Sr isotopic ratios of the Miocene Bidahochi Formation, the mainly Pliocene Bouse Formation, and the Pliocene Imperial Formation generally correspond well with the present‐day Colorado River system and the marine influence at its delta. This suggests a strong link between the ancestral Colorado drainage and all these Neogene deposits.

Canadian Journal of Earth Sciences, 2004

Thirty-seven tephra beds, primarily from coal partings in the Sterling and Beluga formations, wer... more Thirty-seven tephra beds, primarily from coal partings in the Sterling and Beluga formations, were successfully dated by the 40Ar/39Ar method providing a new and revised understanding of the chronostratigraphy of late Tertiary strata within Cook Inlet Basin. Meticulous sample preparation, multiple analyses, and statistical evaluation of the data were required for these low-K, plagioclase- and hornblende-bearing tephras. Dating of subsurface core material provides the first subsurface-to-outcrop tie in Cook Inlet between well 212-24 in the Beluga River Unit and deposits in the Clam Gulch, Diamond Creek, and Fox Creek areas. The new 40Ar/39Ar chronostratigraphic framework place the age of upper part of the Kenai Group strata between 4.6 and 9.4 Ma and support the 8-Ma interpretation of the boundary between the Homerian and Clamgulchian paleobotanical stages. The 49-Ma age from core data in Pioneer Unit suggests the Tyonek Formation is older than previously thought or that these units ...

Aapg Bulletin, 2003

Cook Inlet Basin of south-central Alaska is a forearc basin containing voluminous Tertiary coal d... more Cook Inlet Basin of south-central Alaska is a forearc basin containing voluminous Tertiary coal deposits with sufficient methane content to suggest a major coalbed gas resource. Coals ranging in thickness from 2 to 50 ft (0.6 to 15 m) and in gas content from 50 to 250 scf/ton (1.6 to 7.8 cm2/g) occur in Miocene-Oligocene fluvial deposits of the Kenai Group. These coals have been identified as the probable source of more than 8 tcf gas that has been produced from conventional sandstone reservoirs in the basin. Cook Inlet coals can be divided into two main groups: (1) those of bituminous rank in the Tyonek Formation that contain mainly thermogenic methane and are confined to the northeastern part of the basin (Matanuska Valley) and to deep levels elsewhere; and (2) subbituminous coals at shallow depths (<5000 ft [1524 m]) in the Tyonek and overlying Beluga formations, which contain mainly biogenic methane and cover most of the central and southern basin. Based on core and corrected cuttings-desorption analyses, gas contents average 230 scf/ton (7.2 cm2/g) for bituminous coals and 80 scf/ton (2.5 cm2/g) for subbituminous coals. Isotherms constructed for samples of both coal ranks suggest that bituminous coals are saturated with respect to methane, whereas subbituminous coals at shallow depths along the eroded west-central basin margin are locally unsaturated. A preliminary estimate of 140 tcf gas in place is derived for the basin.

Bulletin of Canadian Petroleum Geology, 2006

Cuttings samples of sub-bituminous humic coals from the Oligocene to Pliocene Tyonek Formation, C... more Cuttings samples of sub-bituminous humic coals from the Oligocene to Pliocene Tyonek Formation, Cook Inlet Basin, Alaska show secondary gas emissions whose geochemistry is consistent with renewed microbial methanogenesis during canister desorption. The renewed methanogenesis was noted after initial desorption measurements had ceased and a canister had an air and desorbed gas mixture backflow into the canister during a measurement. About a week after this event, a secondary emission of gas began and continued for over two years. The desorbed gas volume reached a new maximum, increasing the total from 3.3 to 4.9 litres, some 48% above the pre-contamination total volume. The gases released during desorption show a shift in the isotopic signature over time of methane from δ 13 C CH4 of-53.60 ‰ and δD CH4 of-312.60 ‰ at the first day to δ 13 C CH4 of-57.06 ‰ and δD CH4 of-375.80 ‰ after 809 days, when the experiment was arbitrarily stopped and the canister opened to study the coal. These isotopic data, interpreted using a Bernard Diagram, indicate a shift from a mixed thermogenic and biogenic source typical of natural gases in the coals and conventional gas reservoirs of the Cook Inlet Basin to a likely biogenic acetate-fermentation methane source. However, the appearance of CO 2 during the renewed gas emissions with a δ 13 C CO2 of +26.08 to +21.72 ‰, interpreted using the carbon isotope fractions found for acetate fermentation and CO 2 reduction between CO 2 and CH 4 by Jenden and Kaplan (1986), indicates a biogenic CO 2-reduction pathway may also be operative during renewed gas emission. Adding nutrients to the coal cuttings and canister water and culturing the microbial consortia under anaerobic conditions led to additional methane-rich gas generation in the laboratory. After this anaerobic culturing, ultraviolet microscopy showed that canister water contained common, fluorescent, rod-like microbes comparable to Methanobacterium sp. Scanning electron microscope investigations of the coal matrix showed several morphological types of microbes, including rod, cocci and spherical forms attached to the coal surface. These microbes apparently represent at least a portion of the microbial consortia needed to depolymerize coal, as well as to generate the observed secondary methane emission from the canister. The introduction of 48% more methane from secondary sources has a major impact on coal-bed methane resource assessments and also in determining the true, in-situ degree of methane saturation in coal-beds using isotherms. Canister and isotherm measurements that show "supersaturation" of methane may actually be the result of additional gases generated during secondary methanogenesis.

40Ar/39Ar dating of the Central Plateau Member lavas of the Yellowstone Plateau volcanic field is... more 40Ar/39Ar dating of the Central Plateau Member lavas of the Yellowstone Plateau volcanic field is used to evaluate discordant dates in the existing K-Ar dataset. The 40Ar/39Ar method identifies several sources of anomalous behavior; xenocrystic contamination, excess argon, and argon loss that influence assessments of the eruption ages. Single crystal dating, multiple sample runs, and statistical evaluation of the multiple analyses are used to assign eruption ages for the following lavas; 87±12 ka (Pitchstone Plateau), 90±10 ka (Grants Pass), 94±21 ka (West Yellowstone), 108±7 ka (Gibbon River), 106±7 ka (Solfatara), 122±5 ka (Hayden Valley), and 135±11 ka (Summit Lake). The resulting interpreted eruptive ages provide a better understanding of stratigraphic relations, magma residence times, and eruptive histories. Interpretation of the West Yellowstone eruptive age suggests that about half the volume from CPM lavas erupted from a combination of this flow with the Grants Pass and Pitc...

Open-File Report, 1999

General Map of Armenia 2. Base map of the Shirak area 3 General stratigraphic column of Cretaceou... more General Map of Armenia 2. Base map of the Shirak area 3 General stratigraphic column of Cretaceous rocks 4a. Jajur thrust fault picture 4b. Jajur open pit mine