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At least 1,243 records · Page 69Linked to original sources
USGS2010

The tidally averaged momentum balance in a partially and periodically stratified estuary

Observations of turbulent stresses and mean velocities over an entire spring–neap cycle are used to evaluate the dynamics of tidally averaged flows in a partially stratified estuarine channel. In a depth-averaged sense, the net flow in this channel is up estuary due to interaction of tidal forcing with the geometry of the larger basin. The depth-variable tidally averaged flow has the form of an estuarine exchange flow (downstream at the surface, upstream at depth) and varies in response to the neap–spring transition. The weakening of the tidally averaged exchange during the spring tides appears to be a result of decreased stratification on the tidal time scale rather than changes in bed stress. The dynamics of the estuarine exchange flow are defined by a balance between the vertical divergence of the tidally averaged turbulent stress and the tidally averaged pressure gradient in the lower water column. In the upper water column, tidal stresses are important contributors, particularly during the neap tides. The usefulness of an effective eddy viscosity in the tidally averaged momentum equation is explored, and it is seen that the effective eddy viscosity on the subtidal time scale would need to be negative to close the momentum balance. This is due to the dominant contribution of tidally varying turbulent momentum fluxes, which have no specific relation to the subtidal circulation. Using a water column model, the validity of an effective eddy viscosity is explored; for periodically stratified water columns, a negative effective viscosity is required.

Journal of Physical Oceanography↗
USGS2016

Fire in the Earth System: Bridging data and modeling research

Significant changes in wildfire occurrence, extent, and severity in areas such as western North America and Indonesia in 2015 have made the issue of fire increasingly salient in both the public and scientific spheres. Biomass combustion rapidly transforms land cover, smoke pours into the atmosphere, radiative heat from fires initiates dramatic pyrocumulus clouds, and the repeated ecological and atmospheric effects of fire can even impact regional and global climate. Furthermore, fires have a significant impact on human health, livelihoods, and social and economic systems. Modeling and databased methods to understand fire have rapidly coevolved over the past decade. Satellite and ground-based data about present-day fire are widely available for applications in research and fire management. Fire modeling has developed in part because of the evolution in vegetation and Earth system modeling efforts, but parameterizations and validation are largely focused on the present day because of the availability of satellite data. Charcoal deposits in sediment cores have emerged as a powerful method to evaluate trends in biomass burning extending back to the Last Glacial Maximum and beyond, and these records provide a context for present-day fire. The Global Charcoal Database version 3 compiled about 700 charcoal records and more than 1,000 records are expected for the future version 4. Together, these advances offer a pathway to explore how the strengths of fire data and fire modeling could address the weaknesses in the overall understanding of human-climate–fire linkages. A community of researchers studying fire in the Earth system with individual expertise that included paleoecology, paleoclimatology, modern ecology, archaeology, climate, and Earth system modeling, statistics, geography, biogeochemistry, and atmospheric science met at an intensive workshop in Massachusetts to explore new research directions and initiate new collaborations. Research themes, which emerged from the workshop participants via preworkshop surveys, focused on addressing the following questions: What are the climatic, ecological, and human drivers of fire regimes, both past and future? What is the role of humans in shaping historical fire regimes? How does fire ecology affect land cover changes, biodiversity, carbon storage, and human land uses? What are the historical fire trends and their impacts across biomes? Are their impacts local and/or regional? Are the fire trends in the last two decades unprecedented from a historical perspective? The workshop 1 aimed to develop testable hypotheses about fire, climate, vegetation, and human interactions by leveraging the confluence of proxy, observational, and model data related to decadal- to millennial-scale fire activity on our planet. New research directions focused on broad interdisciplinary approaches to highlight how knowledge about past fire activity could provide a more complete understanding of the predictive capacity of fire models and inform fire policy in the face of our changing climate.

Bulletin of the American Meteorological Society↗
USGS2013

The landfall and inland penetration of a flood-producing atmospheric river in Arizona. Part I: observed synoptic-scale, orographic, and hydrometeorological characteristics

Atmospheric rivers (ARs) are a dominant mechanism for generating intense wintertime precipitation along the U.S. West Coast. While studies over the past 10 years have explored the impact of ARs in, and west of, California’s Sierra Nevada and the Pacific Northwest’s Cascade Mountains, their influence on the weather across the intermountain west remains an open question. This study utilizes gridded atmospheric datasets, satellite imagery, rawinsonde soundings, a 449-MHz wind profiler and global positioning system (GPS) receiver, and operational hydrometeorological observing networks to explore the dynamics and inland impacts of a landfalling, flood-producing AR across Arizona in January 2010. Plan-view, cross-section, and back-trajectory analyses quantify the synoptic and mesoscale forcing that led to widespread precipitation across the state. The analyses show that a strong AR formed in the lower midlatitudes over the northeastern Pacific Ocean via frontogenetic processes and sea surface latent-heat fluxes but without tapping into the adjacent tropical water vapor reservoir to the south. The wind profiler, GPS, and rawinsonde observations document strong orographic forcing in a moist neutral environment within the AR that led to extreme, orographically enhanced precipitation. The AR was oriented nearly orthogonal to the Mogollon Rim, a major escarpment crossing much of central Arizona, and was positioned between the high mountain ranges of northern Mexico. High melting levels during the heaviest precipitation contributed to region-wide flooding, while the high-altitude snowpack increased substantially. The characteristics of the AR that impacted Arizona in January 2010, and the resulting heavy orographic precipitation, are comparable to those of landfalling ARs and their impacts along the west coasts of midlatitude continents.

Arizona↗
USGS2025

Sample Science Traceability Matrix (SSTM) for Perseverance’s Mars sample return collection

The Mars Sample Return (MSR) Campaign aims to retrieve a set of carefully selected and documented samples collected by NASA’s Perseverance rover in and around Jezero Crater on Mars and deliver this set to Earth for comprehensive laboratory analyses. To emphasize the immense scientific return of this unique collection, this work presents a Sample Science Traceability Matrix (SSTM), a systematic framework that aligns each sample with the MSR campaign’s defined science objectives, subobjectives, and critical research questions. The SSTM explicitly connects prioritized goals—including geologic history, astrobiology, planetary evolution, and human exploration science—to each of the individual samples gathered in and around Jezero Crater on Mars. This matrix offers a structured, quantitative method to assess each sample’s capacity to address key scientific questions, while highlighting synergies across the sample suite and showcasing the overall value of the collection. The SSTM provides a valuable tool for guiding future sample analyses and identifying the most impactful samples that could be collected in the future to complete the set collected by the Mars 2020 mission. It also supports the next phase of Mars sample science and informs strategies for future Mars exploration missions.

Astrobiology↗
USGS2015

Using near-real-time monitoring data from Pu'u 'Ō'ō vent at Kīlauea Volcano for training and educational purposes

Training non-scientists in the use of volcano-monitoring data is critical preparation in advance of a volcanic crisis, but it is currently unclear which methods are most effective for improving the content-knowledge of non-scientists to help bridge communications between volcano experts and non-experts. We measured knowledge gains for beginning-(introductory-level students) and novice-level learners (students with a basic understanding of geologic concepts) engaged in the Volcanoes Exploration Program: Pu‘u ‘Ō‘ō (VEPP) “Monday Morning Meeting at the Hawaiian Volcano Observatory” classroom activity that incorporates authentic Global Positioning System (GPS), tilt, seismic, and webcam data from the Pu‘u ‘Ō‘ō eruptive vent on Kīlauea Volcano, Hawai‘i (NAGT website, 2010), as a means of exploring methods for effectively advancing non-expert understanding of volcano monitoring. Learner groups consisted of students in introductory and upper-division college geology courses at two different institutions. Changes in their content knowledge and confidence in the use of data were assessed before and after the activity using multiple-choice and open-ended questions. Learning assessments demonstrated that students who took part in the exercise increased their understanding of volcano-monitoring practices and implications, with beginners reaching a novice stage, and novices reaching an advanced level (akin to students who have completed an upper-division university volcanology class). Additionally, participants gained stronger confidence in their ability to understand the data. These findings indicate that training modules like the VEPP: Monday Morning Meeting classroom activity that are designed to prepare non-experts for responding to volcanic activity and interacting with volcano scientists should introduce real monitoring data prior to proceeding with role-paying scenarios that are commonly used in such courses. The learning gains from the combined approach will help improve effective communications between volcano experts and non-experts during times of crisis, thereby reducing the potential for confusion and misinterpretation of data.

Hawaii↗
USGS2023

The Volcanic Hazard Maps Database: An initiative of the IAVCEI Commission on Volcanic Hazards and Risk

In this work we present the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Commission on Volcanic Hazards and Risk (CVHR) Volcanic Hazard Maps Database and the accompanying volcanichazardmaps.org website. Using input from a series of IAVCEI CVHR Working Group on Hazard Mapping workshops, we developed a classification scheme and terminology framework for categorizing, discussing, naming, and searching for hazard maps. ≥ The database and website aim to serve as a resource for the volcanology community to explore how different aspects of hazard map development and design have been addressed in different countries, for different hazard processes, and for different intended purposes and audiences. Additionally, they act as a tool for presenting hazard map options to stakeholder groups and serve as a learning resource that can be incorporated into educational materials and training courses. In this work, we present the database and website, discuss the classification scheme, explore the enormous diversity of hazard maps, and suggest ways that the database and website can be used by the volcanic hazard mapping community.

Journal of Applied Volcanology↗
USGS1969

The use of Schlumberger and equatorial soundings in groundwater investigations near El Paso, Texas

Electrical soundings using the symmetric AMNB Schlumberger and the bipole-dipole equatorial arrays were made along two profiles near El Paso, Texas, in support of a groundwater exploration program which included seismic refraction and gravity surveys. Electrode spacings (AB/2 or R) reaching 12,000 ft allowed exploration to depths of about 7000 ft. Geoelectrical information on the subsurface materials was augmented by sounding with the bilateral equatorial configuration and by transforming Schlumberger curves into dipole-polar sounding curves with formulas developed by Al'pin and by Tsekov. The bilateral equatorial sounding curves were found useful for detecting the direction of dip of highly resistive bedrocks whereas transformed sounding curves were used to evaluate the average longitudinal resistivity, and hence the depth, to the "electric basement." A few of the Schlumberger sounding curves were either clearly or subtly distorted by nonhorizontal geologic structures. The interpretation of these sounding curves illustrates the requirement for careful analysis in processing electrical prospecting data obtained over complex geologic conditions. The interpretation of a combined Schlumberger-equatorial sounding curve, which did not agree with the preliminary interpretation of seismic refraction data, was confirmed to be correct by data from a test well drilled to a depth of 4363 ft. The application of electrical sounding data in the El Paso area furnished valuable information on the depth to fresh-water-saltwater interfaces and on the depth to highly resistive impervious bedrocks.

Texas↗
USGS1977

Structure mapping on enhanced landsat images of Southern Brazil: Tectonic control of mineralization and speculations on metallogeny

Computer enhancement, particularly contrast-stretching, reveals a previously unnoticed east-west structural zone across a Landsat image of the southern Brazilian Precambrian shield. In this zone occur the only known economic or near-economic deposits of gold, tin, and copper. Such deposits are typically localized by small east-west structural elements. Non-economic copper occurrences elsewhere in the region appear to be related to major northeast- and northwest-trending lineaments mapped on Landsat images. Mineral exploration should be primarily directed at the main east-west lineament, but two other possible east-west zones might be worthwhile targets also. The major east-west lineament projects through a break in the continental shelf, across the Atlantic along a large transoceanic fracture zone and into the African continent along a mapped tectonic trend that goes through an area that produces copper, gold, and tin. Global geophysical data suggest that the mapped east-west trend in South America is a surface reflection of structures that developed in the tectosphere in Precambrian time and that have persisted until the present. © 1977 Society of Exploration Geophysicists.

Geophysics↗
USGS1987

Introduction to the Special Issue on remote sensing

In 1977, the first Special Issue on remote sensing published by Geophysics contained papers selected from two special sessions at the 45th Annual International SEG Meeting, October 12–16, 1975, in Denver, Colorado. That first Special Issue consisted of eight papers: four are primarily tutorial (image processing, spectral signatures in the visible and near infrared, microwave spectra of layered media, and factor analysis of gamma-ray spectrometry), two involve structural interpretations with implications for mineral exploration and seismicity, and two examine multispectral reflectance data for detecting hydrothermal alteration and for uranium exploration. Although these papers indicate the importance of physical properties and models in the interpretation of remote sensing data, the studies were constrained by the instruments that collected the data and by the availability of image-processing software. Circumstances have changed significantly in the intervening decade, as illustrated in recent review papers (Watson, 1985; Goetz et al., 1983) and demonstrated by the papers in this Special Issue.

Geophysics↗
USGS2009

Anomalous dispersion due to hydrocarbons: The secret of reservoir geophysics?

When P- and S-waves travel through porous sandstone saturated with hydrocarbons, a bit of magic happens to make the velocities of these waves more frequency-dependent (dispersive) than when the formation is saturated with brine. This article explores the utility of the anomalous dispersion in finding more oil and gas, as well as giving a possible explanation about the effect of hydrocarbons upon the capillary forces in the formation. ?? 2009 Society of Exploration Geophysicists.

Leading Edge (Tulsa, OK)↗
USGS2011

Rock formation characterization for CO2-EOR and carbon geosequestration; 3D seismic amplitude and coherency anomalies, Wellington Field, Kansas, USA

In this paper, we present a workflow for a Mississipian carbonates characterization case-study integrating post-stack seismic attributes, well-logs porosities, and seismic modeling to explore relating changes in small-scale "lithofacies" properties and/or sub-seismic resolution faulting to key amplitude and coherency 3D seismic attributes. The main objective of this study is to put emphasis on reservoir characterization that is both optimized for and subsequently benefiting from pilot tertiary CO2-EOR in preparation for future carbon geosequestration in a depleting reservoir and a deep saline aquifer. The extracted 3D seismic coherency attribute indicated anomalous features that can be interpreted as a lithofacies change or a sub-seismic resolution faulting. A 2D finite difference modeling has been undertaken to understand and potentially build discriminant attributes to map structural and/or lithofacies anomalies of interest especially when embarking upon CO2-EOR and/or carbon sequestration monitoring and management projects. ?? 2011 Society of Exploration Geophysicists.

SEG Technical Program Expanded Abstracts↗
USGS2013

Integrated geophysical imaging of a concealed mineral deposit: a case study of the world-class Pebble porphyry deposit in southwestern Alaska

We combined aeromagnetic, induced polarization, magnetotelluric, and gravity surveys as well as drillhole geologic, alteration, magnetic susceptibility, and density data for exploration and characterization of the Cu-Au-Mo Pebble porphyry deposit. This undeveloped deposit is almost completely concealed by postmineralization sedimentary and volcanic rocks, presenting an exploration challenge. Individual geophysical methods primarily assist regional characterization. Positive chargeability and conductivity anomalies are observed over a broad region surrounding the deposit, likely representing sulfide minerals that accumulated during multiple stages of hydrothermal alteration. The mineralized area occupies only a small part of the chargeability anomaly because sulfide precipitation was not unique to the deposit, and mafic rocks also exhibit strong chargeability. Conductivity anomalies similarly reflect widespread sulfides as well as water-saturated glacial sediments. Mineralogical and magnetic susceptibility data indicate magnetite destruction primarily within the Cu-Au-Mo mineralized area. The magnetic field does not show a corresponding anomaly low but the analytic signal does in areas where the deposit is not covered by postmineralization igneous rocks. The analytic signal shows similar lows over sedimentary rocks outside of the mineralized area, however, and cannot uniquely distinguish the deposit. We find that the intersection of positive chargeability anomalies with analytic signal lows, indicating elevated sulfide concentrations but low magnetite at shallow depths, roughly delineates the deposit where it is covered only by glacial sediments. Neither chargeability highs nor analytic signal lows are present where the deposit is covered by several hundred meters of sedimentary and volcanic rocks, but a 3D resistivity model derived from magnetotelluric data shows a corresponding zone of higher conductivity. Gravity data highlight geologic features within the deposit, including shallow diorite sills that locally contain higher-grade mineralization. The results thus show ways in which an integrated survey approach might be used to distinguish zones of potentially economic mineralization.

Alaska↗
USGS2015

Summer of Applied Geophysical Experience (SAGE): Training for our future geoscientists

Energy and natural resources are crucial to the sustainability of worldwide economies, security, and overall well-being. However, the future workforce in the energy and natural-resources sector is at risk, and meeting the challenges of this dwindling workforce requires well-educated geoscientists in exploration and applied geophysics and related geoscience and technology disciplines. Programs such as geophysical field courses that are supported by SEG and industry, in partnership with academic institutions and government laboratories, are important approaches to maintaining and enhancing expertise in exploration geophysics. One example of a geophysical field course devoted to educating our future workforce is the Summer of Applied Geophysical Experience (SAGE), a four-week program based in Santa Fe, New Mexico, designed to actively engage students in all phases of applied geophysical research. SAGE is a unique educational experience that combines teaching and research as a partnership among universities, industry, government agencies, and professional societies. SAGE teaches the principles and applications of refraction and reflection seismology, magnetics, gravity, GPS, heat flow, several electromagnetic (EM) methods, and ground-penetrating radar (GPR) in a field-based, hands-on setting. More than 850 students and qualified professionals have attended SAGE, many of whom have gone on to become leaders in academia, industry, and government. SAGE students are exposed to the exciting challenges that face earth scientists today, and they develop skills that are necessary to address the world's growing energy demands. Examples of SAGE research projects include mapping archaeological sites and tectonic structure and investigating water and geothermal resources in the Rio Grande rift.

Leading Edge (Tulsa, OK)↗
USGS2018

Defining blue carbon: The emergence of a climate context for coastal carbon dynamics

Blue Carbon Ecosystems (BCEs) are defined as coastal wetland ecosystems with manageable and atmospherically significant carbon stocks and fluxes. Policy and management opportunities have promoted the emergence of blue carbon as a concept and spurred scientific interest to reduce uncertainties in coastal carbon budgets. The four major BCEs are generally classified by their plant communities: tidal marshes, tidal freshwater forests, mangroves, and seagrass meadows.

Book chapter↗
USGS2005

Egret-Hibernia(!), a significant petroleum system, northern Grand Banks area, offshore eastern Canada

Egret-Hibernia(!) is a well-explored petroleum system (3.25 billion barrels oil equivalent [BOE]) located in the Jeanne d'Arc Basin on the Labrador - Newfoundland shelf. Rifting and sediment fill began in the Late Triassic. Egret source rock was deposited in the Late Jurassic at about 153 Ma. After this time, alternating reservoir rock and seal rock were deposited with some syndepositional faulting. By the end of the Early Cretaceous, faults and folds had formed numerous structural traps. For the next 100 m.y., overburden rock thermally matured the source rock when it reached almost 4 km (2.5 mi) burial depth. For 2 km (1.25 mi) below this depth, oil and gas were expelled, until the source was depleted. The expelled petroleum migrated updip to nearby faulted, anticlinal traps, where much of it migrated across faults and upsection to the Hibernia Formation (44% recoverable oil) and Avalon Formation (28%). Accumulation size decreased, and gas content increased from west to east, independent of trap size. These changes correspond to a decrease in source rock richness and quality from west to east. Almost all (96%) of the discovered petroleum resides in the Lower Cretaceous or older reservoir rock units. All accumulations found to date are normally pressured in structural traps. Fifty-two exploration wells found eighteen discoveries. Their size ranges from 1.2 to 0.01 billion BOE. Most discoveries were made between 1979 and 1991. The discovery cycle began with larger accumulations and progressed to smaller accumulations. The estimated sizes of the larger accumulations have grown since 1990. Estimated mean value for undiscovered hydrocarbons is 3.8 billion BOE, thereby raising the ultimate size of Egret-Hibernia(!) to 6.19 billion BOE. Copyright ?? 2005. The American Association of Petroleum Geologists. All rights reserved.

American Association of Petroleum Geologists Bulle↗
USGS2007

Total petroleum system assessment of undiscovered resources in the giant Barnett Shale continuous (unconventional) gas accumulation, Fort Worth Basin, Texas

Undiscovered natural gas having potential for additions to reserves in the Mississippian Barnett Shale of the Fort Worth Basin, north-central Texas, was assessed using the total petroleum system assessment unit concept and a cell-based methodology for continuous-type (Unconventional) resources. The Barnett-Paleozoic total petroleum system is defined in the Bend arch-Fort Worth Basin as encompassing the area in which the organic-rich Barnett is the primary source rock for oil and gas produced from Paleozoic carbonate and clastic reservoirs. Exploration, technology, and drilling in the Barnett Shale play have rapidly evolved in recent years, with about 3500 vertical and 1000 horizontal wells completed in the Barnett through 2005 and more than 85% of the them completed since 1999. Using framework geology and historical production data, assessment of the Barnett Shale was performed by the U.S. Geological Survey using vertical wells at the peak of vertical well completions and before a transition to completions with horizontal wells. The assessment was performed after (1) mapping critical geological and geochemical parameters to define assessment unit areas with future potential, (2) defining distributions of drainage area (cell size) and estimating ultimate recovery per cell, and (3) estimating future success rates. Two assessment units are defined and assessed for the Barnett Shale continuous gas accumulation, resulting in a total mean undiscovered volume having potential for additions to reserves of 26.2 TCFG. The greater Newark East fracture-barrier continuous Barnett Shale gas assessment unit represents a core-producing area where thick, organic-rich, siliceous Barnett Shale is within the thermal window for gas generation (Ro ??? 1.1%) and is overlain and underlain by impermeable limestone barriers (Pennsylvanian Marble Falls Limestone and Ordovician Viola Limestone, respectively) that serve to confine induced fractures during well completion to maximize gas recovery. The extended continuous Barnett Shale gas assessment unit, which had been less explored, defines a geographic area where Barnett Shale is (1) within the thermal window for gas generation, (2) greater than 100 ft (30 m) thick, and (3) where at least one impermeable limestone barrier is absent. Mean undiscovered gas having potential for additions to reserves in the greater Newark East assessment unit is estimated at 14.6 tcf, and in the less tested extended assessment unit, a mean resource is estimated at 11.6 TCFG. A third hypothetical basin-arch Barnett Shale oil assessment unit was defined but not assessed because of a lack of production data. Copyright ?? 2007. The American Association of Petroleum Geologists. All rights reserved.

American Association of Petroleum Geologists Bulle↗
USGS2003

Deformation and the timing of gas generation and migration in the eastern Brooks Range foothills, Arctic National Wildlife Refuge, Alaska

Along the southeast border of the 1002 Assessment Area in the Arctic National Wildlife Refuge, Alaska, an explicit link between gas generation and deformation in the Brooks Range fold and thrust belt is provided through petrographic, fluid inclusion, and stable isotope analyses of fracture cements integrated with zircon fission-track data. Predominantly quartz-cemented fractures, collected from thrusted Triassic and Jurassic rocks, contain crack-seal textures, healed microcracks, and curved crystals and fluid inclusion populations, which suggest that cement growth occurred before, during, and after deformation. Fluid inclusion homogenization temperatures (175–250 C) and temperature trends in fracture samples suggest that cements grew at 7–10 km depth during the transition from burial to uplift and during early uplift. CH 4 -rich (dry gas) inclusions in the Shublik Formation and Kingak Shale are consistent with inclusion entrapment at high thermal maturity for these source rocks. Pressure modeling of these CH 4 -rich inclusions suggests that pore fluids were overpressured during fracture cementation. Zircon fission-track data in the area record postdeposition denudation associated with early Brooks Range deformation at 64 3 Ma. With a closure temperature of 225–240 C, the zircon fission-track data overlap homogenization temperatures of coeval aqueous inclusions and inclusions containing dry gas in Kingak and Shublik fracture cements. This critical time-temperature relationship suggests that fracture cementation occurred during early Brooks Range deformation. Dry gas inclusions suggest that Shublik and Kingak source rocks had exceeded peak oil and gas generation temperatures at the time structural traps formed during early Brooks Range deformation. The timing of hydrocarbon generation with respect to deformation therefore represents an important exploration risk for gas exploration in this part of the Brooks Range fold and thrust belt. The persistence of gas high at thermal maturity levels suggests, however, that significant volumes of gas may have been generated.

Alaska↗
USGS2003

Petroleum system and production characteristics of the Muddy (J) Sandstone (Lower Cretaceous) Wattenberg continuous gas field, Denver basin, Colorado

Wattenberg field is a continuous-type gas accumulation. Estimated ultimate recovery from current wells is 1.27 tcf of gas from the Lower Cretaceous Muddy (J) Sandstone. Mean gas resources that have the potential to be added to these reserves in the next 30 yr are 1.09 tcf; this will be primarily through infill drilling to recover a greater percentage of gas in place and to drain areas that are isolated because of geologic compartmentalization. Greatest gas production from the Muddy (J) Sandstone in Wattenberg field occurs (1) from within the most permeable and thickest intervals of Fort Collins Member delta-front and nearshore-marine sandstones, (2) to a lesser extent from the Horsetooth Member valley-fill channel sandstones, (3) in association with a large thermal anomaly that is delineated by measured temperatures in wells and by vitrinite reflectance contours of 0.9% and greater, (4) in proximity to the bounding Mowry, Graneros, and Skull Creek shales that are the hydrocarbon source rocks and reservoir seals, and (5) between the Lafayette and Longmont right-lateral wrench fault zones (WFZs) with secondary faults that act as conduits in areas of the field. The axis of greatest gas production is north 25 to 35 degrees northeast, which parallels the basin axis. Recurrent movement along five right-lateral WFZs that crosscut Wattenberg field shifted the Denver basin axis to the northeast and influenced depositional and erosional patterns of the reservoir and seal intervals. Levels of thermal maturity within the Wattenberg field are anomalously high compared to other areas of the Denver basin. The Wattenberg field thermal anomaly may be due to upward movement of fluids along faults associated with probable igneous intrusions. Areas of anomalous high heat flow within the field correlate with an increased and variable gas-oil ratio. Debra Higley has 5 years experience in uranium exploration and 20 years as a petroleum geologist with the U.S. Geological Survey. Her research interests include and integrate reservoir characterization, thermal maturation studies, and petroleum resource assessment in basins in North and South America. She received a B.S. degree in geology from Mesa State College (Colorado) and an M.S. degree in geochemistry and Ph.D. in geology from the Colorado School of Mines.Dave Cox is vice president of Reservoir Engineering for Questa Engineering in Golden, Colorado. He has 25 years experience in the oil and gas industry, primarily in reservoir engineering and property evaluations, and has analyzed reservoirs in 31 states of the United States and 19 other countries. He is an expert in coalbed methane, tight gas reservoirs, and enhanced oil recovery. He has B.S. and M.S. degrees in petroleum engineering from the Colorado School of Mines. Robert Weimer has taught courses in stratigraphy, regional and field geology, and energy resource exploration and development for 43 years. He earned B.A. and M.A. degrees from the University of Wyoming and his Ph.D. from Stanford University. He has been a visiting professor at universities in Calgary, Canada; Adelaide, Australia; and Bandung, Indonesia. He is currently professor emeritus, Colorado School of Mines. Weimer has been honored for teaching excellence, blending basic and applied research, national and international continuing education, and service to scientific societies and to state and national boards.

Colorado↗