Geology of the central Roan Plateau area, northwestern Colorado
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Bulletin↗
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Geologic map of the Roan Plateau area, northwestern Colorado
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IMAP↗
Geologic Map of the Abiquiu Quadrangle, Rio Arriba County, New Mexico
The Abiquiu 1:24,000-scale quadrangle is located along the Colorado Plateau-Rio Grande rift margin in north-central New Mexico. The map area lies within the Abiquiu embayment, an early (pre-Miocene) extensional basin of the Rio Grande rift. Rocks exposed include continental Paleozoic and Mesozoic rocks of the Colorado Plateau and Cenozoic basin-fill deposits and volcanic rocks of the Rio Grande rift. Paleozoic units include the Late Pennsylvanian to Early Permian Cutler Group, undivided. Mesozoic units are Upper Triassic Chinle Group, undivided, middle Jurassic Entrada Sandstone, and Todilto Limestone Member of the Wanakah Formation. Mesozoic rocks are folded in some areas and overlain disconformably by Cenozoic rocks. Cenozoic sedimentary rocks are composed of the Eocene El Rito Formation, Oligocene Ritito Conglomerate, Oligocene-Miocene Abiquiu Formation, and Miocene Chama-El Rito and Ojo Caliente Sandstone Members of the Tesuque Formation of the Santa Fe Group. Volcanic rocks include the Lobato Basalt, the El Alto Basalt, and dacite of the Tschicoma Formation. Quaternary deposits consist of inset ancestral axial and tributary Rio Chama deposits and Holocene floodplain alluvium, fan and pediment alluvium, and landslide colluvium.
Scientific Investigations Map↗
Variation and plasticity and their interaction with urbanization in Guadalupe Bass populations on and off the Edwards Plateau
The Colorado River Basin in Texas has experienced major alterations to its hydrologic regime due to changing land and water use patterns. These anthropogenic influences on hydrologic variability have had major implications for riparian and aquatic ecosystems and the species dependent upon them. However, impacts are often assessed at a limited temporal and spatial scale, tending to focus on relatively short and discrete periods or portions of a river basin. It is not clear how basin-wide alterations occurring over decades affect species. Guadalupe Bass Micropterus treculii are endemic to central Texas and are typically associated with shallow runs and riffles in small streams. However, Guadalupe Bass are found throughout the Colorado River Basin, including the mainstem portion of the lower river downstream of the city of Austin where they support a popular fishery. Because Guadalupe Bass exist across a wide range of stream orders within the basin, it is unclear whether populations respond similarly to anthropogenic disturbances or to conservation and restoration activities. Therefore, our objectives were to: Assess the effects of urbanization and hydrology on the population structure and dynamics of Guadalupe Bass. Evaluate the effects of environmental gradients on ecomorphological variation in Guadalupe Bass populations across multiple spatial scales. Describe the life history, habitat use, and behavior of the Guadalupe Bass population in the lower Colorado River and compare it to populations in more “typical” habitats. Results contribute to an understanding of the response of Guadalupe Bass to anthropogenic disturbances, including increased urbanization in central Texas and further assist in the conservation of the species. The ability of the population to not only persist, but flourish downstream of a heavily populated urban area presented a unique opportunity to investigate a native species response to anthropogenic disturbance. This research revealed differences in Guadalupe Bass habitat associations and movements, contrasts in age and growth, and morphological variation across a gradient of disturbance throughout the Colorado River Basin. Results of this work provide information on the potential effects of human population growth and increased water withdrawals on Guadalupe Bass populations. Additionally, this work adds to an understanding of the unique Guadalupe Bass population found in the lower Colorado River and how it differs from upstream tributary populations. Gathering additional population-level information facilitates conservation actions critical to preserving preferred habitat and promoting growth rates for Guadalupe Bass in streams of different sizes and flow conditions while highlighting interpopulation differences that may warrant consideration for stocking programs and other management strategies. Key findings of this study were: The similarity in response of growth rates to streamflow throughout the Colorado Basin suggests phenotypic plasticity in this trait rather than population-specific adaptations. Reductions in streamflows in the Colorado River Basin, whether due to increased frequency of drought or increased anthropogenic water withdrawal, will likely result in lower Guadalupe Bass growth rates with the potential to impact the structure of populations. Growth and recruitment showed a positive correlation with increased baseflows and mean monthly flows; however, continued assessment is necessary to determine a true relationship. We documented morphological divergence among Guadalupe Bass populations in response to spatial and temporal environmental variation. These ecomorphological differences among populations provide insight into the ability of Guadalupe Bass to respond to the differing in-stream habitat and flow conditions between small ‘typical’ tributary systems and the mainstem Colorado River. Morphological variation may be a population-level adaptation that potentially needs to be taken into consideration when choosing broodstock to maximize stocking success within a system. Understanding the morphological differences between Guadalupe Bass populations in response to local conditions could improve the success of restoration and supplemental stocking programs, especially in the ever-changing landscape of central Texas. We established a baseline for understanding the morphological response of Guadalupe Bass to increased population growth and the threats posed by increased water withdrawals and impervious surface. The mainstem population of Guadalupe Bass was generally more mobile, and more responsive to changes in streamflow, than tributary populations. The observed differences could influence the response of Guadalupe Bass populations to conservation and management actions, such as habitat restoration efforts. Continued monitoring of recruitment and angler exploitation may be beneficial to identify any changes that could negatively impact the population. Conservation initiatives solely focused on physical instream or riparian habitat are unlikely to be as beneficial to Guadalupe Bass as those focused on restoring or maintaining adequate streamflow
Cooperator Science Series↗
CRevolution 2—Origin and evolution of the Colorado River system, workshop abstracts
A 2010 Colorado River symposium, held in Flagstaff, Arizona, involved 70 participants who engaged in intense debate about the origin and evolution of the Colorado River system. This symposium, built upon two previous decadal scientific meetings, focused on forging scientific consensus, where possible, while articulating continued controversies regarding the Cenozoic evolution of the Colorado River System and the landscapes of the Colorado Plateau-Rocky Mountain region that it drains. New developments involved hypotheses that Neogene mantle flow is driving plateau tilting and differential uplift and new and controversial hypotheses for the pre-6 Ma presence and evolution of ancestral rivers that may be important in the history and birth of the present Colorado River. There is a consensus that plateau tilt and uplift models must be tested with multidisciplinary studies involving differential incision studies and additional geochronology and thermochronology to determine the relative importance of tectonic and geomorphic forces that shape the spectacular landscapes of the Colorado Plateau, Arizona and region. In addition to the scientific goals, the meeting participants emphasized the iconic status of Grand Canyon for geosciences and the importance of good communication between the research community, the geoscience education/interpretation community, the public, and the media. Building on a century-long tradition, this region still provides a globally important natural laboratory for studies of the interactions of erosion and tectonism in shaping the landscape of elevated plateaus.
Colorado River System↗
Geologic map of the Citadel Plateau Quadrangle, Moffat County, Colorado
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IMAP↗
Simulation of groundwater withdrawal scenarios for the Redwall-Muav and Coconino Aquifer Systems of northern and central Arizona
The Northern Arizona Regional Groundwater Flow Model was used to estimate the hydrologic changes, including water-level change and groundwater discharge to streams and springs, that may result from future changes in groundwater withdrawals in and near the Coconino Plateau Water Advisory Council study area, Coconino and Navajo Counties, Arizona. Three future groundwater withdrawal scenarios for tribal and nontribal uses were developed by the Coconino Plateau Water Advisory Council and were simulated for the period representing the years from 2006 through 2105. Scenario 1 assumes no major changes in groundwater use except for increased demand based on population projections. Scenario 2 assumes that a pipeline will provide a source of surface water from Lake Powell to areas near Cameron and Moenkopi that would replace local groundwater withdrawals. Scenario 3 assumes that the pipeline extends to the Flagstaff and Williams areas, and would replace groundwater demands for water in the area. The Coconino Plateau Water Advisory Council withdrawal scenarios primarily influence water levels and groundwater discharge in the Coconino Plateau basin, near the western margin of the Little Colorado River Plateau basin, and the Verde Valley subbasin. Simulated effects of the withdrawal scenarios are superimposed on effects of previous variations in groundwater withdrawals and artificial and incidental recharge. Pre-scenario variations include changes in water-levels in wells; groundwater storage; discharge to streams and springs; and evapotranspiration by plants that use groundwater. Future variations in groundwater discharge and water-levels in wells will continue to occur as a result of both the past and any future changes. Water-level variations resulting from post-2005 stresses, including groundwater withdrawals and incidental and artificial recharge, in the area of the withdrawal scenarios are primarily localized and superimposed on the regional changes caused by variations in stresses that occurred since the beginning of the initial stresses in the early 1900s through 2005. Withdrawal scenario 1 produced a broad region on the Coconino Plateau where water-levels declined 3–5 feet by 2105, and local areas with water-level declines of 100 feet or more where groundwater withdrawals are concentrated, near the City of Flagstaff Woody Mountain and Lake Mary well fields, and the towns of Tusayan, Williams, and Moenkopi. Water-level rises of 100 feet or more were simulated at areas of incidental recharge near wastewater treatment facilities near Flagstaff, Tusayan, Grand Canyon South Rim, Williams, and Munds Park. Simulated water-level change from 2006 through 2105 for scenarios 2 and 3 is mostly different from water-level change simulated for scenario 1 at the local level. For scenarios 2 and 3, water levels near Cameron in 2105 where 1–3 feet higher than simulated for scenario 1. Water levels at Moenkopi are more than 100 feet higher due to the elimination of a proposed withdrawal well that was simulated in scenario 1. Scenario 3 eliminates more groundwater withdrawals in the Flagstaff and Williams areas, simulates 1–3 feet less water-level decline than scenario 1 across much of the Coconino Plateau, and water levels that are as much as 50 feet higher than simulated by scenario 1 near withdrawal wells in the Williams and Flagstaff areas. Scenario 1 simulated the most change in groundwater discharge for the Little Colorado River below Cameron and for Oak Creek above Page Springs where declines in discharge of about 1.3 and 0.9 cubic feet per second (ft 3 /s), respectively, were simulated. Other simulated changes in discharge through 2105 in scenario 1 are losses of less than 0.4 ft 3 /s at the Upper Verde River, losses of less than 0.3 ft 3 /s at Havasu Creek and at Colorado River below Havasu Creek, losses of less than 0.1 ft 3 /s at Clear Creek, and increases in flow at the south rim springs and Chevelon Creek of less than 0.1 and 0.3 ft 3 /s, respectively. Simulated changes in discharge for scenarios 2 and 3 are less than for scenario 1 because of lower rates of groundwater withdrawal. Scenario 3 resulted in greater groundwater discharge than scenarios 1 and 2 at all major groundwater discharge features from 2006 through 2105 except for Clear and Chevelon Creeks, where the same groundwater discharge was simulated by each of the three scenarios. Changes in groundwater discharge are expected to occur after 2105 to all major surface features that discharge from the Redwall-Muav and Coconino aquifers because change in aquifer storage was occurring at the end of the simulation in 2105. The accuracy of simulated changes resulting from the Coconino Plateau Water Advisory Council groundwater withdrawal scenarios is dependent on the persistence of several hydrologic assumptions that are inherent in the Northern Arizona Regional Groundwater Flow Model including, but not limited to, the reasonably accurate simulation of (1) transmissivity distributions, (2) distributions of vertical hydraulic properties, (3) distributions of spatial rates of withdrawal and incidental recharge, (4) aquifer extents, and (5) hydrologic barriers and conduits.
Arizona↗
Regional groundwater-flow model of the Redwall-Muav, Coconino, and alluvial basin aquifer systems of northern and central Arizona
A numerical flow model (MODFLOW) of the groundwater flow system in the primary aquifers in northern Arizona was developed to simulate interactions between the aquifers, perennial streams, and springs for predevelopment and transient conditions during 1910 through 2005. Simulated aquifers include the Redwall-Muav, Coconino, and basin-fill aquifers. Perennial stream reaches and springs that derive base flow from the aquifers were simulated, including the Colorado River, Little Colorado River, Salt River, Verde River, and perennial reaches of tributary streams. Simulated major springs include Blue Spring, Del Rio Springs, Havasu Springs, Verde River headwater springs, several springs that discharge adjacent to major Verde River tributaries, and many springs that discharge to the Colorado River. Estimates of aquifer hydraulic properties and groundwater budgets were developed from published reports and groundwater-flow models. Spatial extents of aquifers and confining units were developed from geologic data, geophysical models, a groundwater-flow model for the Prescott Active Management Area, drill logs, geologic logs, and geophysical logs. Spatial and temporal distributions of natural recharge were developed by using a water-balance model that estimates recharge from direct infiltration. Additional natural recharge from ephemeral channel infiltration was simulated in alluvial basins. Recharge at wastewater treatment facilities and incidental recharge at agricultural fields and golf courses were also simulated. Estimates of predevelopment rates of groundwater discharge to streams, springs, and evapotranspiration by phreatophytes were derived from previous reports and on the basis of streamflow records at gages. Annual estimates of groundwater withdrawals for agriculture, municipal, industrial, and domestic uses were developed from several sources, including reported withdrawals for nonexempt wells, estimated crop requirements for agricultural wells, and estimated per capita water use for exempt wells. Accuracy of the simulated groundwater-flow system was evaluated by using observational control from water levels in wells, estimates of base flow from streamflow records, and estimates of spring discharge. Major results from the simulations include the importance of variations in recharge rates throughout the study area and recharge along ephemeral and losing stream reaches in alluvial basins. Insights about the groundwater-flow systems in individual basins include the hydrologic influence of geologic structures in some areas and that stream-aquifer interactions along the lower part of the Little Colorado River are an effective control on water level distributions throughout the Little Colorado River Plateau basin. Better information on several aspects of the groundwater flow system are needed to reduce uncertainty of the simulated system. Many areas lack documentation of the response of the groundwater system to changes in withdrawals and recharge. Data needed to define groundwater flow between vertically adjacent water-bearing units is lacking in many areas. Distributions of recharge along losing stream reaches are poorly defined. Extents of aquifers and alluvial lithologies are poorly defined in parts of the Big Chino and Verde Valley sub-basins. Aquifer storage properties are poorly defined throughout most of the study area. Little data exist to define the hydrologic importance of geologic structures such as faults and fractures. Discharge of regional groundwater flow to the Verde River is difficult to identify in the Verde Valley sub-basin because of unknown contributions from deep percolation of excess surface water irrigation.
Scientific Investigations Report↗
Interagency Work Group attempts to save razorback sucker in Lake Mohave
No abstract available.
Lake Mohave↗
Aeromagnetic map of the Powderhorn wilderness study area and Cannibal Plateau Roadless Area, Gunnison and Hinsdale counties, Colorado
The Powderhorn Wilderness Study Area (51,000 acres or 20,640 hectares) and the contiguous Cannibal Plateau Roadless Area (29,500 acres or 11,959 hectares) are on the Gunnison County-Hinsdale County boundary, approximately 50mi (80 km) southwest of Gunnison and a few miles east of Lake City, Colo. Part of the area has been known as the Powderhorn Primitive Area. The mineral resource potential of the study area has been assessed by the U.S. Geological Survey and the U.S. Bureau of Mines; this assessment involved, besides the geologic study and economic appraisal (Sharp and others, 1983), a geophysical survey (this report) by the Geological Survey, and a geochemical survey (Sharp and Lane, 1983) by the Geological Survey and the Bureau of Mines.
Colorado↗
The San Franciscan volcanic field, Arizona
LOCATION OF AREA The San Franciscan volcanic field, which takes its name from San Francisco Mountain, the largest volcano of the group, covers about 3,000 square miles in the north-central part of Arizona, as shown by the shaded space on the index map forming figure 1. The center of the field lies about 50 miles south of the Grand Canyon of the Colorado and the southern boundary is in part coterminous with that of the San Francisco Plateau, which forms the southwestern division of the great Colorado Plateau. The region is easily reached, for the main line of the Atchison, Topeka, & Santa Fe Railway traverses it from east to west for more than 60 miles. Flagstaff, a town of 1,500 inhabitants 10 miles south of the summit of San Francisco Mountain, is on the railroad, amid a branch line runs from Williams, 34 miles farther west, to the Grand Canyon. All the more important points of interest in the field may be reached without difficulty by wagon, and outfits may be obtained at Flagstaff. OUTLINE OF THE REPORT This report deals primarily with the volcanic phenomena of the region as determined in the field and laboratory. Chapter I contains a brief description of the geography of the field and Chapter II is devoted largely to the sedimentary formations and structure. The rest of the report Chapters III to VI—treats entirely of the various features of the volcanoes and igneous rocks, both individually and collectively. Detailed descriptions of the volcanoes and lava fields are given in Chapter III; the volcanic history of the region and its correlation with the general history of the surrounding country are presented in Chapter IV. These two chapters will presumably suffice for the general reader who may desire to become acquainted with the broader volcanic features of the region. Chapter V (Petrography) is devoted entirely to the detailed description of the individual igneous rocks of the region, as represented by a selected set of type specimens. In Chapter VI (Petrology) is presented a discussion of the igneous rocks considered collectively—that is, as a series of genetically related members. These last two chapters will be more especially interesting to petrologists, although there is considerable matter in the last chapter which may also be of interest to the general reader. EXTENT OF FIELD WORK The field work on which the report is based was carried on during the summers of 1901 to 1903, a portion of the time, however, being occupied by side trips to the Grand Canyon of the Colorado, the Verde Valley, and the Moqui Buttes. It was the original intention to study only San Francisco Mountain, but scattered observations made during the first summer at other localities, especially at Elden Mountain and Kendrick Peak, seemed to indicate that the region would repay wider study. The work was accordingly extended so as to embrace all the large cones that lie in the vicinity of San Francisco Mountain and some 2,000 square miles of the surrounding plateau country. The more detailed work was confined to the large cones and the laccoliths, as they presented the greatest variety of phenomena within the smallest space. Reconnaissance work was carried on in the surrounding country more especially for the purpose of determining the limits of the widespread basalt flows, their relation to the underlying sedimentary formations, and the character of those formations.
Arizona↗
Geochemical map of the Powderhorn Wilderness study and Cannibal Plateau Roadless Area, Gunnison and Hinsdale counties, Colorado
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Miscellaneous Field Studies Map↗
A multi-proxy record of hydroclimate, vegetation, fire, and post-settlement impacts for a subalpine plateau, Central Rocky Mountains U.S.A
Apparent changes in vegetation distribution, fire, and other disturbance regimes throughout western North America have prompted investigations of the relative importance of human activities and climate change as potential causal mechanisms. Assessing the effects of Euro-American settlement is difficult because climate changes occur on multi-decadal to centennial time scales and require longer time perspectives than historic observations can provide. Here, we report vegetation and environmental changes over the past ~13,000 years as recorded in a sediment record from Bison Lake, a subalpine lake on a high plateau in northwestern Colorado. Results are based on multiple independent proxies, which include pollen, charcoal, and elemental geochemistry, and are compared with previously reported interpretations of hydroclimatic changes from oxygen isotope ratios. The pollen data indicate a slowly changing vegetation sequence from sagebrush steppe during the late glacial to coniferous forest through the late Holocene. The most dramatic vegetation changes of the Holocene occurred during the ‘Medieval Climate Anomaly’ (MCA) and ‘Little Ice Age’ (LIA) with rapid replacement of conifer forest by grassland followed by an equally rapid return to conifer forest. Late Holocene vegetation responses are mirrored by changes in fire, lake biological productivity, and watershed erosion. These combined records indicate that subsequent disturbance related to Euro-American settlement, although perhaps significant, had acted upon a landscape that was already responding to MCA-LIA hydroclimatic change. Results document both rapid and long-term subalpine grassland ecosystem dynamics driven by agents of change that can be anticipated in the future and simulated by ecosystem models.
The Holocene↗
Guadalupe Bass flow-ecology relationships; with emphasis on the impact of flow on recruitment
Guadalupe Bass Micropterus treculii is an economically and ecologically important black bass species endemic to the Edwards Plateau ecoregion and the lower portions of the Colorado River in central Texas. It is considered a fluvial specialist and as such, there are concerns that the increasing demands being placed upon the water resources of central Texas by growing human populations have the potential to negatively impact Guadalupe Bass populations. Therefore, this study assessed the relationship between Guadalupe Bass growth, feeding ecology, and streamflow. Sagittal otoliths were removed from Guadalupe Bass collected from throughout their range during 2015-2017 and used to estimate the age and back-calculate the growth trajectory of each individual. Additionally, young-of-year (YOY) Guadalupe Bass were collected every 10-14 days from two second-order streams, the North Llano River and South Llano River, in the Colorado Basin on the Edwards Plateau. Stomach contents of these individuals were identified and the effect of streamflow on the occurrence of the taxa comprising the stomach contents assessed. Guadalupe Bass growth was greater in the Colorado and Guadalupe River basins, independent of stream order, and tended to increase with increasing stream order within a basin. Growth was higher in higher stream orders and during years with stable and lower spring and summer monthly median flows, lower minimum and maximum flows, slower rise and fall rates, and higher baseflows. Growth was not influenced by years with higher monthly median flows in winter. These results would seem to contradict previous research, but more likely represent a fuller picture of how Guadalupe Bass respond to flow conditions. The disagreement between the current study and past studies seem to be attributable, at least in part, to the fact that previous studies were conducted during a period of extensive drought, while the current study was conducted during relatively wet conditions. Taken together with previous studies, the current study suggests that Guadalupe Bass growth is sensitive to flow conditions and is lower in years with flow conditions that fall outside a basin- and stream order-specific optimal range for the species. A total of 21 unique taxonomic groups were recovered from the stomachs of YOY Guadalupe Bass collected from the North Llano River and South Llano River. Aquatic insects, especially larval mayflies (Ephemeroptera), damselflies (Odanata: Zygoptera), and caddisflies (Trichoptera), were the most frequently encountered taxa. While there was no difference between the two rivers in stomach content composition, there was a strong longitudinal gradient in both systems with aquatic insects predominating at upstream sample sites and fishes being more common at downstream sites. Stream discharge during the 24 hours prior to collection did not have any influence on the probability of a taxa being found in Guadalupe Bass stomachs. The results of this study support efforts to manage Guadalupe Bass populations at a sub-watershed scale and suggests that populations occupying the same stream order within a basin are likely to have similar responses to annual flow conditions. In addition, these results indicate that the lower Colorado River population may inhabit a unique set of conditions that has supported the development of a trophy Guadalupe Bass fishery. Further, this study highlights the need to incorporate a sufficient range of annual flow conditions to ensure that the influence of stream flow on fish growth is adequately assessed. While interannual variation in growth rates seem to be capable of serving as a proxy for recruitment and year-class strength, long-term monitoring of recruitment paired with assessment of growth is necessary to further clarify the relationship between population density, flow regime, recruitment and growth and allow the construction of predictive models.
Texas↗