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612 records · Page 34Linked to original sources
USGS1981

Preliminary hydrologic evaluation of the North Horn Mountain coal-resource area, Utah

North Horn Mountain is part of a deeply dissected plateau in central Utah which is characterized by deep, narrow, steep-walled canyons with local relief of more than 1,000 feet. Geologic units exposed in the North Horn Mountain area range in age from Late Cretaceous to Holocene and contain two mineable seams of Cretaceous coal. The area is in the drainage basin of the San Rafael River, in the Colorado River Basin. Runoff from the mountain is ephemeral. This runoff to the San Rafael River is by way of Cottonwood and Perron Creeks and represents less than 10 percent of their average annual runoff. Probable peak discharges (100-year flood) for the ephemeral streams draining North Horn Mountain are estimated to range from 200 to 380 cubic feet per second. The chemical quality of surface water in the area is good. The water is generally of a calcium magnesium bicarbonate type with average dissolved solids less than 500 milligrams per liter. Annual sediment yield in most of the area ranges from 0.1 to 0.2 acre-foot per square mile but locally is as high as 1.0 acre-foot per square mile. Most of the sediment is eroded during cloudbursts. Most of the ground water above the coal on North Horn Mountain probably is in perched aquifers. These aquifers support the flow of small seeps and springs. In some areas, the regional water table appears to extend upward into the coal. The principal source of recharge is precipitation that probably moves to aquifers along faults, joints, or fractures. This movement is apparently quite rapid. The dissolved-solids concentrations of ground water in the North Horn Mountain area range from less than 500 to about 1,000 milligrams per liter. Coal mining on North Horn Mountain should have minor "effects on the quantity and quality of surface water. The maximum predicted decrease in the annual flow of Ferron and Cottonwood Creeks is less than U percent. The sediment loads of affected streams could be significantly increased if construction were to take place during the summer cloudburst season. Subsidence, which usually follows underground coal mining, could create rock fractures through which a perched aquifer might be drained, thus depleting the flow of seeps or springs fed by that aquifer. It is considered unlikely that the mining will adversely affect the chemical quality of the ground water.

Utah↗
USGS1999

Physiographic rim of the Grand Canyon, Arizona: A digital database

This Open-File report is a digital physiographic map database. This pamphlet serves to introduce and describe the digital data. There is no paper map included in the Open-File report. The report does include, however, PostScript and PDF format plot files, each containing an image of the map. For those interested in a paper plot of information contained in the database or in obtaining the PostScript plot files, please see the section entitled "For Those Who Don't Use Digital Geologic Map Databases" below. This physiographic map of the Grand Canyon is modified from previous versions by Billingsley and Hendricks (1989), and Billingsley and others (1997). The boundary is drawn approximately along the topographic rim of the Grand Canyon and its tributary canyons between Lees Ferry and Lake Mead (shown in red). Several isolated small mesas, buttes, and plateaus are within this area, which overall encompasses about 2,600 square miles. The Grand Canyon lies within the southwestern part of the Colorado Plateaus of northern Arizona between Lees Ferry, Colorado River Mile 0, and Lake Mead, Colorado River Mile 277. The Colorado River is the corridor for raft trips through the Grand Canyon. Limestone rocks of the Kaibab Formation form most of the north and south rims of the Grand Canyon, and a few volcanic rocks form the north rim of parts of the Uinkaret and Shivwits Plateaus. Limestones of the Redwall Limestone and lower Supai Group form the rim of the Hualapai Plateau area, and Limestones of Devonian and Cambrian age form the boundary rim near the mouth of Grand Canyon at the Lake Mead. The natural physiographic boundary of the Grand Canyon is roughly the area a visitor would first view any part of the Grand Canyon and its tributaries.

Arizona↗
USGS1988

High-resolution 40Ar 39Ar chronology of Oligocene volcanic rocks, San Juan Mountains, Colorado

The central San Juan caldera complex consists of seven calderas from which eight major ash-flow tuffs were erupted during a period of intense volcanic activity that lasted for approximately 2 m.y. about 26–28 Ma. The analytical precision of conventional K-Ar dating in this time interval is not sufficient to unambiguously resolve this complex history. However, 40 Ar 39 Ar "> 40 Ar 39 Ar incremental-heating experiments provide data for a high-resolution chronology that is consistent with stratigraphie relations. Weighted-mean age-spectrum plateau ages of biotite and sanidine are the most precise with standard deviations ranging from 0.08 to 0.21 m.y. The pooled estimate of standard deviation for the plateau ages of 12 minerals is about 0.5 percent or about 125,000 to 135,000 years. Age measurements on coexisting minerals from one tuff and on two samples of each of two other tuffs indicate that a precision in the age of a tuff of better than 100,000 years can be achieved at 27 Ma. New data indicate that the San Luis caldera is the youngest caldera in the central complex, not the Creede caldera as previously thought.

Geochimica et Cosmochimica Acta↗
USGS2012

Wyoming Basin Ecoregion: Chapter 25 in Status and trends of land change in the Western United States--1973 to 2000

The Wyoming Basin Ecoregion (Omernik 1987; U.S. Environmental Protection Agency, 1999) covers approximately 128,914 km 2 (49,774 mi 2 ) in Wyoming and parts of northwestern Colorado, northeastern Utah, southeastern Idaho, and southern Montana (fig. 1). The ecoregion is bounded on the east by the Northwestern Great Plains Ecoregion; on the south and east by the Southern Rockies Ecoregion; on the south by the Colorado Plateaus Ecoregion; on the south and west by the Wasatch and Uinta Mountains Ecoregion; and on the north by the Middle Rockies Ecoregion and parts of the Montana Valley and Foothill Prairies Ecoregion (fig. 1). The ecoregion generally consists of broad intermountain basins dominated by arid grasslands and shrublands, as well as isolated hills and low mountains that merge to the south into a dissected plateau.

Colorado;Idaho;Montana;Utah;Wyoming↗
USGS2016

Variability in rainfall at monitoring stations and derivation of a long-term rainfall intensity record in the Grand Canyon Region, Arizona, USA

In this study, we examine rainfall datasets of varying temporal length, resolution, and spatial distribution to characterize rainfall depth, intensity, and seasonality for monitoring stations along the Colorado River within Marble and Grand Canyons. We identify maximum separation distances between stations at which rainfall measurements might be most useful for inferring rainfall characteristics at other locations. We demonstrate a method for applying relations between daily rainfall depth and intensity, from short-term high-resolution data to lower-resolution longer-term data, to synthesize a long-term record of daily rainfall intensity from 1950–2012. We consider the implications of our spatio-temporal characterization of rainfall for understanding local landscape change in sedimentary deposits and archaeological sites, and for better characterizing past and present rainfall and its potential role in overland flow erosion within the canyons. We find that rainfall measured at stations within the river corridor is spatially correlated at separation distances of tens of kilometers, and is not correlated at the large elevation differences that separate stations along the Colorado River from stations above the canyon rim. These results provide guidance for reasonable separation distances at which rainfall measurements at stations within the Grand Canyon region might be used to infer rainfall at other nearby locations along the river. Like other rugged landscapes, spatial variability between rainfall measured at monitoring stations appears to be influenced by canyon and rim physiography and elevation, with preliminary results suggesting the highest elevation landform in the region, the Kaibab Plateau, may function as an important orographic influence. Stations at specific locations within the canyons and along the river, such as in southern (lower) Marble Canyon and eastern (upper) Grand Canyon, appear to have strong potential to receive high-intensity rainfall that can generate runoff which may erode alluvium. The characterization of past and present rainfall variability in this study will be useful for future studies that evaluate more spatially continuous datasets in order to better understand the rainfall dynamics within this, and potentially other, deep canyons.

Arizona↗
USGS1952

Glaciation and drainage changes in the fish Lake Plateau, Utah

The Fish Lake Plateau , nearly centrally located among the High Plateaus of Utah , exhibits glacial and other geomorphic features of regional significance. The plateau is divided into two areas by Fish Lake and the wide valley of Sevenmile Creek. The Fish Lake trough is a structural basin; Sevenmile Valley may be largely erosional. Volcanic rocks of Tertiary age underlie most of the plateau ; early Tertiary sedimentary rocks are also present. Glaciated canyons with well-developed cirques are especially prominent along the east-facing sides of the Fish Lake trough and Sevenmile Valley. Ice-eroded features occur over much of the plateau top. Near the mouths of several of the glaciated canyons are two conspicuous sets of moraines. The older set is more extensive and less rugged than the younger and occurs at somewhat lower elevations. Two substages of glaciation thus recognized are correlated with Wisconsin I and II of Ray; probable correlatives of Wisconsin III, IV, and V are represented by moraines which are younger than these two sets. Fish Lake drains north into Fremont River, a tributary of the Colorado River. An abandoned southern outlet and waterfall, the latter at a higher elevation than the present elevation of the original northern bedrock divide, indicate drainage reversal. Evidence is presented which suggests that this reversal was pre-glacial and probably the result of fault-block tilting.

Utah↗
USGS2018

Fish Lake limnology and watershed aqueous geochemistry, Fish Lake Plateau, Utah

Fish Lake is located at 2696 m elevation on the Fish Lake Plateau with a bedrock geology of Oligocene to Pliocene age volcanics and Cretaceous to Eocene age sedimentary rocks. Lake bathymetry indicates a maximum depth of ~27 m and volume of 2.31 x 108 m3. The lake is dimictic with summer water column temperature declines of 13˚C between 7 to 15 m depth, whereas in spring and fall water column is isothermal. Numerous surface streams flow into the lake and there is one surface outflow stream, Lake Creek, which drains to the northeast into Johnson Valley Reservoir and the Fremont River, which is a tributary of the upper Colorado River. Surface inflow streams and spring waters are generally dilute and ionic compositions are consistent with bedrock geology. Spring and creek water oxygen and hydrogen stable isotope compositions indicate snowmelt is the predominant water source to the lake. High evaporative enrichment is indicated by lake water stable oxygen and hydrogen compositions and conservative ions, which suggest evaporative water loss equal or greater than inflow. The ionic and isotope data combined with preliminary discharge measurements provide a preliminary estimated lake-water residence time between approximately 15 and 30 years, although groundwater flux is currently unknown. Dissolved silica concentrations decline by two orders of magnitude between inflowing waters and summer lake waters, indicating substantial uptake by freshwater diatoms and high biological productivity. During summer, epilimnion pH values of 8.7 contribute to slight oversaturation with respect to calcite/aragonite, which suggests that precipitates could form in minor concentration. Below the thermocline pH is near neutral and carbonate mineral dissolution within the water column is likely.

Utah↗
USGS2020

Precipitation, temperature, groundwater-level elevation, streamflow, and potential flood storage trends within the Brazos, Colorado, Big Cypress, Guadalupe, Neches, Sulphur, and Trinity River basins in Texas through 2017

The U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers (USACE), analyzed streamflow trends and streamflow-related variables through 2017 in seven important water-supply basins to provide information that can help water managers with the USACE and river authorities make future water management decisions. The primary purpose of this report is to document trends in long-term streamflow data at 114 selected USGS streamflow-gaging stations and 36 simulated reservoir-inflow stations in 7 river basins primarily in Texas: Brazos, Colorado, Big Cypress, Guadalupe, Neches, Sulphur, and Trinity. In this report, trends were considered statistically significant if their p -values were less than or equal to 0.05 ( p -value ≤0.05). Streamflow data selected for temporal trend analyses included annual minimum streamflow, annual peak streamflow, and streamflow volume. Precipitation, air temperature, and groundwater-level-elevation data were analyzed for trends that may help to explain changes observed in the streamflow statistics. Basins were divided into sections along county lines for precipitation analyses. Streamflow volumes were analyzed for associations with potential flood storage. The potential flood storage, defined as the difference between maximum storage and normal storage, was computed for each dam from the National Inventory of Dams database and accumulated over time based on the completion date of the dam. Precipitation and air temperature trends were analyzed for each of the eight climate divisions (High Plains, Trans-Pecos, Low Rolling Hills, Edwards Plateau, North Central Texas, South Central Texas, East Texas, and Upper Coast). Results of precipitation trend analyses indicated moderate upward trends in the Upper Coast and East Texas Climate Divisions analyzed on an annual time step from 1900 through 2017. These two climate divisions are in the eastern and southeastern parts of the State, and they receive more mean annual precipitation (45.88 and 46.09 inches, respectively) than the other climate divisions. The results of air temperature analyses indicated upward trends in annual mean air temperature within all climate divisions, with a mean slope of 0.02 degree Fahrenheit per year, or 1 degree every 50 years. Within the Brazos River Basin, results of precipitation trend analyses on an annual time step indicated that precipitation amounts are most likely increasing in the lower and middle sections of the basin. Downward trends in annual streamflow and in the ratio of streamflow volume to precipitation volume were indicated at 7 of the 15 stations in the upper sections of the basin. The lower sections of the basin had mostly downward trends in annual minimum streamflow, whereas upward trends in annual minimum streamflow were indicated in the upper sections of the basin. Downward trends in annual peak streamflow were indicated at many of the stations in the upper sections of the basin. At the same seven stations in the upper sections of the basin where there were downward trends in annual streamflow, there were also downward trends in the ratio of streamflow volume to precipitation volume. The data from the same seven stations indicated negative associations between potential flood storage volume and annual streamflow volume and downward trends in the ratio of annual streamflow volume to potential flood storage volume. With the known addition of 13,006,394 acre-feet of potential flood storage between 1900 and 2010 in the subbasins analyzed, streamflow volumes have decreased in the upper sections of the Brazos River Basin. Within the Colorado River Basin, results of precipitation trend analyses on an annual time step indicated no trends in the basin. Downward trends in annual streamflow were indicated at 16 stations in the upper sections of the basin, whereas no trends in annual streamflow were indicated in the lower section of the basin. In the lower section of the basin, one station that was operated as a continuous streamflow-gaging station through 2017 had a downward trend in annual minimum streamflow, and another station (operated through 2007) had an upward trend in annual minimum streamflow. In the upper sections of the basin, data from seven stations indicated upward trends in annual minimum streamflow, and data from six stations indicated downward trends. Data from 18 stations in the upper sections of the basin indicated downward trends in annual peak streamflow. Thirteen of the 16 stations in the upper sections of the basin with data that indicated downward trends in annual streamflow also have data that indicated downward trends in the ratio of streamflow volume to precipitation volume. Data from the same 13 stations indicated negative associations between potential flood storage volume and annual streamflow volume and downward trends in the ratio of annual streamflow volume to potential flood storage volume. With the known addition of 7,193,147 acre-feet of potential flood storage between 1891 and 2014 in the subbasins analyzed, streamflow volumes have decreased in the upper sections of the Colorado River Basin. Within the Big Cypress Basin, results of precipitation trend analyses on annual, seasonal, and monthly time steps indicated almost no trends in the basin as defined in this report. However, the annual precipitation p -value only slightly exceeded the p -value threshold for a statistically significant trend. Given the upward trend in precipitation in the East Texas Climate Division, which includes the Big Cypress Basin, and the low p -value for annual precipitation within the basin, precipitation in the basin may be increasing over time. Two annual streamflow trends, one upward and one downward, were in the upper parts of the basin. Data from USGS streamflow-gaging station 07346000 Big Cypress Bayou near Jefferson, Texas, indicated an upward trend in annual minimum streamflow and a downward trend in annual peak streamflow. The station is immediately downstream from Lake O’ the Pines; presumably, minimums have increased because of regulated releases, and annual peaks have decreased because of storage from the lake for flood control. Despite the known addition of 2,737,154 acre-feet of potential flood storage between 1898 and 2011 in the subbasins analyzed, there have not been widespread reductions in streamflow volumes in the Big Cypress Basin, except for within the drainage area for the farthest upstream station on the main stem downstream from Mount Pleasant, Texas. Within the Guadalupe River Basin, results of precipitation trend analyses on an annual time step indicated an upward trend in the lower section of the basin, but no trends in annual streamflow were indicated in the lower section of the basin. In the upper section of the basin, data from 1 of the 13 stations indicated an upward trend in annual streamflow. Data from 6 of the 13 stations in the upper section of the basin indicated a trend in annual minimum streamflow with 4 upward and 2 downward trends. Data from 2 of the 13 stations in the upper section of the basin indicated downward trends in annual peak streamflow. Despite the known addition of 2,016,534 acre-feet of potential flood storage between 1849 and 2013 in the subbasins analyzed, streamflow volumes have not decreased in the Guadalupe River Basin. Within the Neches River Basin, results of precipitation trend analyses on an annual time step indicated upward trends in the basin. None of the data from stations analyzed in the Neches River Basin indicated annual trends in streamflow despite upward trends in annual precipitation within the basin. Data from 9 of the 19 stations analyzed in the basin indicated upward trends in annual minimum streamflow. Data from one of the simulated-inflow stations indicated a downward trend in annual minimum streamflow into Sam Rayburn Reservoir. Data from two stations indicated downward trends in annual peak streamflow, and data from one small subbasin indicated an upward trend in annual peak streamflow. Despite the known addition of 4,839,609 acre-feet of potential flood storage between 1888 and 2008 in the subbasins analyzed, there have not been widespread reductions in streamflow volumes in the Neches River Basin. Within the Sulphur River Basin, results of precipitation trend analyses on an annual time step indicated a moderate upward trend within the basin. Data from only one of the stations, the simulated inflow to Jim Chapman Lake, indicated an annual upward trend in streamflow despite an upward trend in annual precipitation throughout the basin. Data from three of the six stations in the Sulphur River Basin indicated upward trends in annual minimum streamflow, and data from one of the six stations indicated a downward trend in annual peak streamflow. Despite the known addition of 6,933,361 acre-feet of potential flood storage between 1904 and 2006 in the subbasins analyzed, streamflow volumes have not decreased in the Sulphur River Basin. Within the Trinity River Basin, results of precipitation trend analyses on an annual time step indicated upward trends in most sections of the basin. Data from 8 of the 36 stations analyzed for trends in annual streamflow indicated upward trends, and all 8 stations are in the upper sections of the basin. None of the data from stations in the lower sections of the basin indicated trends in annual streamflow. Data from 16 of the 36 stations indicated upward trends in annual minimum streamflow. Upward trends in annual minimum streamflow could be the result of managed reservoir releases in combination with wastewater treatment plant releases in the large Dallas-Fort Worth metroplex in the upper sections of the basin. All the trends in annual peak streamflow were in the sections of the basin that include the Dallas-Fort Worth metroplex. Data from two stations, one USGS streamflow-gaging station and one simulated-inflow station, indicated upward trends in annual peak streamflow, and data from one streamflow-gaging station indicated a downward trend in annual peak streamflow. Of the basins included in this study, the Trinity River Basin has the second largest amount of potential flood storage of 8,947,349 acre-feet from dams added between 1890 and 2013. Eleven stations in the Trinity River Basin had positive associations between potential flood storage volume and annual streamflow volume, indicating that annual streamflow increases as potential flood storage increases. Data from 7 of the 11 stations also indicated upward trends in annual streamflow. The positive associations may be the result of increases in minimum streamflow, which could be the result of any combination of managed reservoir releases, wastewater treatment plant releases, or increased runoff from urbanized areas, particularly in the urbanized area of the Dallas-Fort Worth metroplex.

Texas↗
USGS2003

Hazard mitigation related to water and sediment fluxes in the Yellow River basin, China, based on comparable basins of the United States

The Yellow River, north-central China, and comparative rivers of the western United States, the Rio Grande and the Colorado River, derive much of their flows from melting snow at high elevations, but derive most of their se diment loads from semiarid central parts of the basins. The three rivers are regulated by larg e reservoirs that store water and sediment, causing downstream channel scour and, farthe r downstream, flood hazard owing to re- deposition of sediment. Potential approaches to reducing continui ng bed aggradation and increasing flood hazard along the lower Yellow Ri ver include flow augmentation, retirement of irrigation that decreases flows and increas es erosion, and re-routing of the middle Yellow River to bypass large sediment i nputs of the Loess Plateau.

Yellow River Basin↗
USGS2018

Geologic map of the San Antonio Mountain area, northern New Mexico and southern Colorado

The geologic map of the San Antonio Mountain area in northern New Mexico and southern Colorado is located along the west-central part of the San Luis Valley. The San Luis Valley is the geomorphic expression of the San Luis Basin, an extensional basin associated with the northern Rio Grande rift. Deposits within the map area record volcanic, sedimentary, and tectonic processes over the last ~33 million years. Oldest exposed deposits include Oligocene volcanic rocks associated with the southeast San Juan Mountains locus of volcanism within the Southern Rocky Mountains volcanic field. Overlying deposits of the Southern Rocky Mountains volcanic field are volcaniclastic sedimentary rocks interbedded with predominantly basaltic lava flows of Oligocene to Miocene age. Basalt to rhyolite volcanic rocks of the Pliocene to Pleistocene Taos Plateau volcanic field unconformably overlie Oligocene to Miocene volcanic and sedimentary deposits. Superposed on the Tertiary deposits are Pleistocene to Holocene alluvial and colluvial deposits. North- to northwest-trending faults displace rocks within the map area. Magnitude of deformation is broadly correlative with age of the deposits inasmuch as Oligocene to Miocene rocks display a greater degree of fault displacement and east tilting than Pliocene volcanic rocks. Within the map area, faults displace Oligocene to Miocene deposits 10–30 meters with generally down-to-west offset, and the units dip eastward 3–7 degrees. Pliocene volcanic rocks exhibit shallower eastward dips inferred primarily from the slope of upper lava flow surfaces that dip eastward from 1–3 degrees and lava flows are generally displaced less than 5 meters.

Colorado, New Mexico↗
USGS2000

Evolution of the Creede Caldera and its relation to mineralization in the Creede mining district, Colorado

At 25 Ma a major epithermal silver and base metal deposit formed in rhyolitic welded tuff near Creede, Colorado. Nearly 24000 metric tons of silver, appreciable lead, and small amounts of zinc, copper, and gold, have been produced from large, crustified veins under Bachelor and Bulldog Mountains north and northwest of Creede. Prior geologic, hydrologic, and stable-isotope studies showed that ore deposition was associated with the mixing and boiling of waters from diverse sources and suggester that a critical part of the ore-forming fluid may have originated within the ancient lake and sediments of the lacustrine Creede Formation that filled the Creede caldera. Two drill holes that sampled the heretofore hidden lower half of the Creede Formation are the focus of this book. The Creede caldera formed at 26.9 Ma within a high constructional plateau of silicic ashflows that covered and were sporadically interlayed with, intermediate lavas and lahars from large stratovolcanoes. The Creede caldera lake had an inflow evaporation balance that did not permit rapid filling to create a brim-full deep lake. Thus salts were evaporatively concentrated; but, with the exception of possible gypsum, no evaporite minerals preserved. Cool springs deposited travertine as mounds and contributed to limestone interlaminations within the sediment. The lake bottom was anoxic, and bacterial reduction of sulfate led to extreme sulfur isotopic fractionation in diagenetic pyrite. The caldera gradually resurged, converting the initial equant lake into an arcuate moat. Resurgent doming, alluvial fans, lacustrine sediments, ashfalls, and lava domes displaced water, lifted the lake so that it overlapped what later became the southern edge of the mineralized are, and eventually filled the basin. At 25.1 Ma an unseen pluton intruded beneath the northen part of the Creede district and created a convecting olume that drew in brine from the Creede caldera fill, meteotic water from highlands to the north, and possibly a fluid carrying radiogenic lead. These waters mixed and boiled as they approached the surface and moved southward, deposited a zoned epithermal deposit a few hundred meters below the paleosurface, and finally discharged into the top of the Creede Formation. The sulfide in the ores was the igneous derivation, but the sulfate was a mixture of biogenic sulfur from the Creede Formation, oxidized igneous sulfide, and thermochemically reduced and partially oxygen exchanged sulfate. The studies of the Creede caldera provide key observational and conceptual elements for the generalized model of the Creede ore deposit. The relation of the Creed ore deposit to a brine reservoir has broad significance because other brine accumulations (as in the Great Basin, the Green River Basin, or the playas of the Altiplano offer similar setting and exploration opportunities.

Colorado↗
USGS2019

Middle Pleistocene formation of the Rio Grande Gorge, San Luis Valley, south-central Colorado and north-central New Mexico, USA: Process, timing, and downstream implications

The Rio Grande is the fourth longest river in North America extending over 3,000 km from the Rocky Mountains to the Gulf of Mexico. The Pleistocene evolution of this river from individual subbasins into a coalesced fluvial system has been long debated. Herein, we constrain the middle Pleistocene evolution of the northernmost and largest Rio Grande basin, the San Luis basin, and the timing of incision of the Rio Grande Gorge, based on new geologic mapping, 3 He surface exposure dating, and U-series dating on pedogenic carbonates. 3 He dating of shoreline deposits of closed basin Lake Alamosa and fluvially scoured bedrock along the Rio Grande gorge rim indicate the San Luis basin was connected with southerly Rio Grande basins and progressively incised since ∼400 ka. Waning tectonic activity, coupled with the hydrologic response to intensified middle Pleistocene glaciation, drove southward spillover of Lake Alamosa ∼400 ka, expanding the river's drainage basin by nearly 24,000 km 2 , and adding recharge areas in the high-altitude, glaciated San Juan, Tusas, and Sangre de Cristo Mountains. Geologic barriers to streamflow on the Taos Plateau were breached and basin tributary drainages were integrated and inset into their present canyons ∼250-200 ka, with approximately 120 m of incision during ∼400-200 ka. Previous work demonstrates that southerly streamflow through basins south of the SLB terminated into a large, rift-related bolson complex until the middle Pleistocene, and most axial Rio Grande river incision has occurred since 630 ka. We propose that middle Pleistocene integration of the SLB was the major geomorphic event that eroded Plio-Pleistocene tectonic and volcanic barriers and re-established flow of the Rio Grande from the Rocky Mountains to the Gulf of Mexico.

Colorado, New Mexico↗
USGS2001

Late Cenozoic regional collapse due to evaporite flow and Dissolution in the Carbondale Collapse Center, West-Central Colorado

Dissolution and flow of Pennsylvanian evaporitic rocks in west-central Colorado created the Carbondale Collapse Center, a 450 mi2 structural depression with about 4,000 ft of vertical collapse during the late Cenozoic. This paper describes evidence of collapse in the lower Roaring Fork River valley. Both the lateral extent and amount of vertical collapse is constrained by deformed upper Cenozoic volcanic rocks that have been correlated using field mapping, 40Ar/39Ar geochronology, geochemistry, and paleomagnetism. The Carbondale Collapse Center is one of at least two contiguous areas that have experienced major evaporite tectonism during the late Cenozoic. Historic sinkholes, deformed Holocene deposits, and modern high-salinity loads in the rivers and thermal springs indicate the collapse process continues today. Flow of evaporitic rocks is an important element in the collapse process, and during initial stages of collapse it was probably the primary causative mechanism. Dissolution, however, is the ultimate means by which evaporite is removed from the collapse area. As the Roaring Fork River began to rapidly down-cut through a broad volcanic plateau during the late Miocene, the underlying evaporite beds were subjected to differential overburden pressures. The evaporitic rocks flowed from beneath the upland areas where overburden pressures remained high, toward the Roaring Fork River Valley where the pressures were much lower. Along the valley the evaporitic rocks rose upward, sometimes as diapirs, forming or enhancing a valley anticline in bedrock and locally upwarping Pleistocene terraces. Wherever the evaporites encountered relatively fresh ground water, they were dissolved, forming underground voids into which overlying bedrock and surficial deposits subsided. The saline ground water eventually discharged to streams and rivers through thermal springs and by seepage into alluvial aquifers.

Mountain Geologist↗
USGS2014

U.S. Geological Survey Karst Interest Group Proceedings, Carlsbad, New Mexico, April 29-May 2, 2014

Karst aquifer systems are present throughout parts of the United States and some of its territories, and have developed in carbonate rocks (primarily limestone and dolomite) that span an interval of time encompassing more than 550 million years. The depositional environments, diagenetic processes, post-depositional tectonic events, and geochemical weathering processes that form karst aquifers are varied and complex, and involve biological, chemical, and physical changes. These factors, combined with the diverse climatic regimes under which karst development in these rocks has taken place, result in the unique dual- or triple-porosity nature of karst aquifers. These complex hydrogeologic systems typically represent challenging and unique conditions to scientists attempting to study groundwater flow and contaminant transport in these terrains. The dissolution of carbonate rocks and the subsequent development of distinct and beautiful landscapes, caverns, and springs has resulted in the most exceptional karst areas of the United States being designated as national or state parks; commercial caverns and known privately owned caves number in the tens of thousands. Both public and private properties provide access for scientists to study the flow of groundwater in situ. Likewise, the range and complexity of landforms and groundwater flow systems associated with karst terrains are enormous, perhaps more than for any other aquifer type. Karst aquifers and landscapes that form in tropical areas, such as the cockpit karst along the north coast of Puerto Rico, differ greatly from karst landforms in more arid climates, such as the Edwards Plateau in west-central Texas or the Guadalupe Mountains near Carlsbad, New Mexico, where hypogenic processes have played a major role in speleogenesis. Many of these public and private lands also contain unique flora and fauna associated with these karst hydrogeologic systems. As a result, numerous federal, state, and local agencies have a strong interest in the study of karst terrains. Many of the major springs and aquifers in the United States have developed in carbonate rocks, such as the Floridan aquifer system in Florida and parts of Alabama, Georgia, and South Carolina; the Ozark Plateaus aquifer system in parts of Arkansas, Kansas, Missouri, and Oklahoma; and the Edwards-Trinity aquifer system in west-central Texas. These aquifers, and the springs that discharge from them, serve as major water-supply sources and as unique ecological habitats. Competition for the water resources of karst aquifers is common, and urban development and the lack of attenuation of contaminants in karst areas can impact the ecosystem and water quality of these aquifers. The concept for developing a platform for interaction among scientists within the U.S. Geological Survey (USGS) working on karst-related studies evolved from the November 1999 National Ground-Water Meeting of the USGS. As a result, the Karst Interest Group (KIG) was formed in 2000. The KIG is a loose-knit, grass-roots organization of USGS and non-USGS scientists and researchers devoted to fostering better communication among scientists working on, or interested in, karst science. The primary mission of the KIG is to encourage and support interdisciplinary collaboration and technology transfer among scientists working in karst areas. Additionally, the KIG encourages collaborative studies between the different mission areas of the USGS as well as other federal and state agencies, and with researchers from academia and institutes. The KIG also encourages younger scientists by participation of students in the poster and oral sessions. To accomplish its mission, the KIG has organized a series of workshops that are held near nationally important karst areas. To date (2014) six KIG workshops, including the workshop documented in this report, have been held. The workshops typically include oral and poster sessions on selected karst-related topics and research, as well as field trips to local karst features. Proceedings of the workshops are published by the USGS and are available online at http://water.usgs.gov/ogw/karst/kig . The first KIG workshop was held in St. Petersburg, Florida, February 13–16, 2001, in the vicinity of the large springs and other karst features of the Floridan aquifer system. The second KIG workshop was held August 20–22, 2002, in Shepherdstown, West Virginia, in proximity to the carbonate aquifers of the northern Shenandoah Valley and highlighted an invited presentation on karst literature by the late Barry F. Beck of P.E. LaMoreaux and Associates. The third KIG workshop was held September 12–15, 2005, in Rapid City, South Dakota, nearby to karst features in evaporites and limestones of the Madison Group in the Black Hills of South Dakota, including Wind Cave National Park and Jewel Cave National Monument. The workshop also included a featured presentation by Thomas Casadevall, Central Region Director, USGS, on the status of earth science at the USGS and evening trips to Jewel Cave led by Mike Wiles, National Park Service (NPS) and Wind Cave led by Rod Horrocks, NPS. The fourth KIG workshop was held May 27–29, 2008, and hosted by the Hoffman Environmental Research Institute and Center for Cave and Karst Studies at Western Kentucky University in Bowling Green, Kentucky, near Mammoth Cave National Park and karst features of the Chester Upland and Pennyroyal Plateau. The workshop featured a late-night field trip into Mammoth Cave with Rickard Toomey and Rick Olsen, NPS. The fifth workshop was held April 26–29, 2011, and was a joint meeting of the USGS KIG and University of Arkansas HydroDays, hosted by the Department of Geosciences at the University of Arkansas in Fayetteville. The workshop featured an outstanding field trip to the unique karst terrain along the Buffalo National River of the southern Ozarks and a keynote presentation on paleokarst in the United States by Art and Peggy Palmer. This sixth and current 2014 KIG workshop is hosted by the National Cave and Karst Research Institute (NCKRI) in Carlsbad, New Mexico, with Director of NCKRI, George Veni, serving as co-chair of the workshop with Eve Kuniansky, USGS. The session planning committee for this sixth workshop includes Van Brahana, USGS retired and University of Arkansas Professor Emeritus; Tom Byl, USGS and Tennessee State University; Zelda Bailey, former Director of NCKRI and retired Director, National Institute of Standards and Technology, Boulder Laboratory, Colorado; Patrick Tucci, USGS retired; and Mike Bradley, Allan Clark, Geoff Delin, Daniel Doctor, James Kaufmann, Eve Kuniansky, Randy Orndorff, Larry Spangler, and Dave Weary of the USGS. The karst hydrology field trip on Thursday will be led by Lewis Land (NCKRI karst hydrologist) and the optional Friday field trip on the geology of Carlsbad Caverns National Park will be led by George Veni. The keynote speaker is Dr. Penelope Boston, Director of Cave and Karst Studies at New Mexico Tech, Socorro, and Academic Director at NCKRI, who will address the future of karst research. Additionally, there is a featured presentation “Irish karst and its management,” by Caoimhe Hickey, The Geological Survey of Ireland, preceding a panel discussion on “Collaboration During Times of Limited Resources.” The extended abstracts of USGS authors were peer reviewed and approved for publication by the U.S. Geological Survey. Articles submitted by university researchers and other federal and state agencies did not go through the formal USGS peer review and approval process, and therefore may not adhere to our editorial standards or stratigraphic nomenclature and is not research conducted or data collected by the USGS. However, all articles had at a minimum of two peer reviews, and all articles were edited for consistency of appearance in the published Proceedings. The use of trade, firm or product names in any article is for descriptive purposes only and does not imply endorsement by the U.S. Government. The USGS, Office of Groundwater, provides technical support for the Karst Interest Group website and public availability of the Proceedings from these workshops, and the USGS Groundwater Resources Program funds the publication costs. Finally, the cover illustration is the work of Ann Tihansky, USGS, used since the first KIG workshop in 2000.

Scientific Investigations Report↗
USGS2002

Characterization of selenium in the lower Gunnison River basin, Colorado, 1988-2000

Selenium concentrations in certain water bodies in the lower Gunnison River Basin, including the lower Gunnison River and lower Uncompahgre River, have exceeded the Colorado water-quality standard of 5 micrograms per liter for selenium. A task force was formed in 1998 that consists of various government agencies, private irrigation companies, and local residents to address the selenium concerns in the lower Gunnison River Basin. The task force, working with the National Irrigation Water Quality Program, needed more detailed information on selenium loading in the basin to develop viable alternatives for remediating selenium in the lower Gunnison River Basin. In 1999-2000, the U.S. Geological Survey collected selenium data for tributaries of the Gunnison River downstream from the North Fork of the Gunnison and in the North Fork Basin. The largest selenium load in a tributary stream was in the Uncompahgre River, which accounted for about 38 percent of the selenium load in the Gunnison River at Whitewater. The North Fork of the Gunnison River accounted for about 7 percent of the selenium load in the Gunnison River. Two tributaries east of Delta, Sunflower Drain and Bonafide Ditch, consist primarily of irrigation return flows and were other major selenium sources to the Gunnison River. Some tributaries in the lower North Fork Basin had selenium concentrations exceeding 5 micrograms per liter. Except for several streams draining the Uncompahgre Plateau, many tributaries to the Gunnison River downstream from the North Fork had selenium concentrations exceeding 5 micrograms per liter. Except during occasional rain and snowmelt events, selenium loading from nonirrigated desert areas was minimal. Detailed characterization studies were done in 1999-2000 on Cedar Creek and Loutzenhizer Arroyo, which contribute the largest tributary selenium loads to the Uncompahgre River. Selenium concentrations in Cedar Creek downstream from Miguel Road ranged from 12 to 28 micrograms per liter in November 1999. Montrose Arroyo was the largest selenium source to Cedar Creek. On an annual basis, about 20 percent of the selenium load in Cedar Creek originates in the basin upstream from Miguel Road. Selenium concentrations in Loutzenhizer Arroyo ranged from 157 to 347 micrograms per liter in February 2000. A significant increase in selenium concentrations occurred in the stream reach between the Selig Canal and Falcon Road (LZU7). Although selenium concentrations in the west tributary of Loutzenhizer Arroyo were lower than in the main stem, the west tributary contributed about 41 percent of the selenium load. Downstream from the confluence with the west tributary to the mouth, selenium concentrations in the arroyo gradually decreased, and the increase in selenium load in the lower reach was small.

Water-Resources Investigations Report↗
USGS2013

Geophysical constraints on Rio Grande rift structure in the central San Luis Basin, Colorado and New Mexico

Interpretation of gravity, aeromagnetic, and magnetotelluric (MT) data reveals patterns of rifting, rift-sediment thicknesses, distribution of pre-rift volcanic and sedimentary rocks, and distribution of syn-rift volcanic rocks in the central San Luis Basin, one of the northernmost major basins that make up the Rio Grande rift. Rift-sediment thicknesses for the central San Luis Basin determined from a three-dimensional gravity inversion indicate that syn-rift Santa Fe Group sediments have a maximum thickness of ~2 km in the Sanchez graben near the eastern margin of the basin along the central Sangre de Cristo fault zone, and reach nearly 1 km within the Monte Vista graben near the western basin margin along the San Juan Mountains. In between, Santa Fe Group thickness is negligible under the San Luis Hills and estimated to reach ~1.1 km under the Costilla Plains (although no independent thickness constraints exist, and a range of thicknesses of 600 m to 2 km is geophysically reasonable). From combined geophysical and geologic considerations, pre-rift, dominantly sedimentary rocks appear to increase in thickness from none in the Sanchez graben on the east to perhaps 800 m under the San Luis Hills on the west. The pre-rift rocks are most likely early Tertiary in age, but the presence of Mesozoic and Paleozoic sedimentary rocks cannot be ruled out. Geophysical data provide new evidence that an isolated exposure of Proterozoic rocks on San Pedro Mesa is rooted in the Precambrian basement. This narrow, north-south–trending basement high has ~2 km of positive relief with respect to the base of the Sanchez graben, and separates the graben from the structural depression beneath the Costilla Plains. A structural high composed of pre-rift rocks, long inferred to extend from under the San Luis Hills to the Taos Plateau, is confirmed and found to be denser than previously believed, with little or no overlying Santa Fe Group sediments. Major faults in the study area are delineated by geophysical data and models; these faults include significant vertical offsets (≥1 km) of Precambrian rocks along the central and southern zones of the Sangre de Cristo fault system. Other faults with similarly large offsets of the Santa Fe Group include a fault bounding the western margin of San Pedro Mesa, and other faults that bound the Monte Vista graben in an area previously assumed to be a simple hinge zone at the western edge of the San Luis Basin. A major north-south–trending structure with expression in gravity and MT data occurs at the boundary between the Costilla Plains and the San Luis Hills structural high. Although it has been interpreted as a down-to-the-east normal fault or fault zone, our modeling suggests that it also is likely related to pre-rift tectonics. Aeromagnetic anomalies over much of the area are interpreted to mainly reflect variations of remanent magnetic polarity and burial depth of the 5.3–3.7 Ma Servilleta Basalt of the Taos Plateau volcanic field. Magnetic-source depth estimates are interpreted to indicate patterns of subsidence following eruption of the basalt, with maximum subsidence in the Sanchez graben.

Colorado, New Mexico↗
USGS1978

Blue Ribbon Lineament, an east-trending structural zone within the Pioche mineral belt of southwestern Utah and eastern Nevada

The Blue Ribbon lineament is an east-west structural zone that is about 25 kilometers wide and passes through the Pioche mineral belt at about 38°10' N. It is best known in Utah, where it is at least 190 km long, and extends from the southern Sevier Plateau in the High Plateaus westward and across southern Mountain Home (Needle) Range in the Great Basin. It probably continues westward an additional 170 km into Nevada, where it connects with the eastern end of the 230-km Warm Springs lineament. The Blue Ribbon lineament is defined by range terminations and east-trending valleys, alinement of eruptive centers of middle Miocene (20 million years) to Pliocene(?) (5-1.8 m.y.) alkalic rhyolite, alinement of areas of middle Miocene to Pliocene mineralized rocks (mostly fluorine, uranium, tungsten) and hydrothermally altered rocks, east-trending magnetic highs and interruptions of magnetic anomalies, and east-striking basin-range faults of late Tertiary and Quaternary age. Mountains south of the lineament are topographically and structurally lower than those to the north. North-striking Quaternary basin-range faults, the Thermo hot springs area, several warm springs and former hot springs, and numerous dacitic to andesitic volcanic centers of early to middle Miocene age (26-20 m.y.) occur along the lineament. The Blue Ribbon lineament is believed to be a deep crustal fault zone dating from at least middle Miocene time and possibly much earlier. It thus developed generally coincident with northerly trending classical basin-range faults. Its fracture system was an important, long-lived conduit for mineralizing fluids, and it should be an attractive target for minerals exploration in the future. The lineament could be due to an east-trending warp in the subducting mantle plate, or it could be part of a past or present intracontinental transform fault that locally gets younger eastward and dies out eastward in the western Colorado Plateaus province.

Utah↗
USGS2010

Protocols for geologic hazards response by the Yellowstone Volcano Observatory to activity within the Yellowstone Volcanic System

Executive Summary The Yellowstone Plateau hosts an active volcanic system, with subterranean magma (molten rock), boiling, pressurized waters, and a variety of active faults with significant earthquake hazards. Within the next few decades, light-to-moderate earthquakes and steam explosions are certain to occur. Volcanic eruptions are less likely, but are ultimately inevitable in this active volcanic region. This document summarizes protocols, policies, and tools to be used by the Yellowstone Volcano Observatory (YVO) during earthquakes, hydrothermal explosions, or any geologic activity that could lead to a volcanic eruption. Yellowstone National Park is home to Yellowstone Caldera, the largest volcanic system by volume in the United States, as well as a vigorous hydrothermal system composed of pressurized subsurface boiling waters and active faults capable of generating substantial seismicity. The region is subject to hazards spanning a wide range of intensities, magnitudes, likelihood of occurrence, and geographic extent of impact. These hazards include small and comparatively common hydrothermal explosions, occasional strong earthquakes, rare relatively non-explosive lava flows, and very rare large explosive volcanic eruptions. Addressing the broad style of potential hazards and the vast spatial and temporal scales over which these hazards can occur requires a general plan that outlines the Yellowstone Volcano Observatory (YVO) response to a hazardous or potentially hazardous geological event or unrest (defined as departure from normal activity levels). The U.S. Geological Survey (USGS) Volcano Science Center (VSC) Response Plan for Significant Volcanic Events in the United States (Moran and others, 2024) forms the basis of any response by YVO but will be modified to suit the specific characteristics of the observatory, which operates as a consortium of nine federal, state, and academic institutions. Decisions on declaring an event response or “activity with potential” (defined as unrest that is not immediately hazardous but that may evolve into a hazardous event), as well as any changes in Volcano Alert Level and Aviation Color Code or the release of formal Information Statements, will be made by the USGS via the YVO Scientist-in-Charge (SIC) in consultation with the leads of the YVO member agencies. The YVO response to hazardous or potentially hazardous geological activity in or around Yellowstone National Park will focus on the collection and analysis of data relevant to the location and style of the activity. Those data will be interpreted within the existing geological framework for the region to develop probabilistic assessments of potential outcomes. These interpretations and assessments will be used to support decision making by emergency management officials including Yellowstone National Park managers or within the National Incident Management System if an Incident Command System (ICS) is activated. YVO will also convene a communications group open to each member agency to ensure consistent internal and external messaging and that the public is kept informed of the unrest through formal notifications, social media posts, online content, traditional media interviews, and community meetings. This response plan will be evaluated and updated as needed by the observatory and will be available through the YVO and USGS public websites. Responses to volcanic eruptions and responses outside of the Yellowstone region, but within the YVO area of responsibility (including Arizona, Utah, New Mexico, and Colorado), will follow the U.S. Geological Survey Volcano Science Center Response Plan for Significant Volcanic Events in the United States (Moran and others, 2024).

Idaho, Montana, Wyoming↗