Geologic and Hydrogeologic 

Framework of the Española Basin -­

Proceedings of the 4th Annual 

Española Basin Workshop, Santa Fe, 

New Mexico, March 1-3, 2005 

Kevin C. McKinney, editor 

Any use of trade, product, or firm names in this publication is for descriptive purposes only 

and does not imply endorsement by the U.S. Government. 

Open-File Report 2005-1130 

U.S. Department of Interior 

U.S. Geological Survey 
INTRODUCTION by HUDSON, Mark R..........................................................................5

BASIC WATER DATA 

AN UPDATE ON THE SURFICIAL WATER RESOURCES IN THE LOS ALAMOS AREA, 

NEW MEXICO by DALE, Michael, GRANZOW, Kim, ENGLERT, Dave, YANICAK, Steve, FORDSCHMID, Ralph, LONGMIRE, Patrick, and COUNCE, Dale....................................................6 

HYDROGEOLOGIC STUDY OF EL DORADO UTILITIES LIMESTONE PRODUCTION 

WELLS, CANADA DE LOS ALAMOS GRANT, SANTA FE COUNTY, NEW MEXICO by 

FROST Jack P., JOHNSON Michael S., and DUNCAN 

Don........................................................................................................................7 

AN UPDATE OF HYDROGEOLOGIC CONDITIONS IN THE SOUTHERN ESPAÑOLA BASIN

by JOHNSON, Peggy S. and KONING, Daniel J...................................................................8 

WATER QUALITY AND WATER CHEMISTRY 

OCCURRENCE OF ELEVATED ARSENIC AND FLUORIDE CONCENTRATIONS IN THE 

ESPAÑOLA BASIN by FINCH, Steven T. ........................................................................11 

CONTAMINANT CONCENTRATIONS IN WATER AND BRYOPHYTES FOUND IN FOUR 

SPRINGS LOCATED ALONG THE UPPER RIO GRANDE, NEW MEXICO by FORD-SCHMID, 

Ralph, DALE, Michael, ENGLERT, Dave, and GRANZOW, Kim.............................................12 

NATURAL URANIUM IN GROUND WATER IN THE ESPANOLA BASIN by MCQUILLAN, 

Dennis, LONGMIRE, Patrick, JOHNSON, Peggy, KULIS, Jerzy, MARTINEZ, Fernando, COUNCE, 

Dale, and KEATING, Elizabeth......................................................................................13 

RESULTS FROM WATER QUALITY ANALYSES OF DOMESTIC WELLS IN THE 

POJOAQUE, NAMBE, AND TESUQUE WATERSHEDS, NEW MEXICO by WUST, Stephen L., 

LONGMIRE, Patrick, and COUNCE, Dale.........................................................................14 

WATER BALANCE AND STREAM/AQUIFER INTERACTION 

GROUNDWATER PATHWAYS ASSESSMENT: UNCERTAINTY ANALYSIS OF 

CONTANINANT TRANSPORT FROM MORTANDAD CANYON by BIRDSELL, Kay H., 

VESSELINOV, Velimir V., DAVIS, Paul A., HOLLIS, Diana, NEWMAN, 

Brent......................................................................................................................15 

ASSESSING GROUND-WATER RECHARGE THROUGH THE PAJARITO FAULT ZONE, 

UPPER PAJARITO CANYON, LOS ALAMOS, NEW MEXICO by DALE, Michael, GOFF, Fraser, 

GRANZOW, Kim, LONGMIRE, Patrick, and COUNCE, Dale.................................................16 

2
AN INVESTIGATION OF RECHARGE TO THE ESPAÑOLA BASIN UTILIZING NOBLE 

GASES, GROUNDWATER AGES, AND TEMPERATURE DATA by MANNING, Andrew, 

KEATING, Elizabeth, CAINE, Jonathan Saul, LANDIS, Gary..................................................17 

VALUE OF USGS WATER SUPPLY PAPER 1525 TO CURRENT ESPANOLA BASIN 

GEOHYDROLOGY STUDIES by SPIEGEL, Zane............................................................18 

DATA INTEGRATION AND HYDROGEOLOGIC MODEL TESTING 

GROUNDWATER TEMPERATURES AND HEAT FLOW IN THE ESPAÑOLA BASIN by 

Keating, Elizabeth, Zyvoloski, George, Manning, Andrew......................................................19

AN UPDATE ON THE CITY OF SANTA FE’S REGIONAL GROUNDWATER FLOW MODEL 

by MCCURRY, Gordon N.1

, MCCLUSKEY, Mark J.2, BORCHERT, Claudia..............................20

THREE-DIMENSIONAL HYDROGEOLOGICAL ARCHITECTURE 

LATERAL DISPLACEMENT VARIATION AND FAULT INTERACTION ON THE PAJARITO 

PLATEAU, RIO GRANDE RIFT, NEW MEXICO by LEWIS, Claudia J., GARDNER, Jamie N., 

LAVINE, Alexis, and RENEAU, Steven L., and SCHULTZ, Emily S.........................................21 

HYDROGEOLOGIC CROSS SECTIONS OF THE ESTANCIA GROUNDWATER BASIN, 

CENTRAL NEW MEXICO by HAWLEY, John W............................................................22

INTRABASINAL ARCHITECTURE OF THE SOUTHERN ẼSPANOLA BASIN by KONING, 

Daniel, J., READ, Adam, S., GRAUCH, (Tien) V.J.S. , and MINOR, Scott A................................23 

TEXTURAL AND THICKNESS VARIABILITY Of THE ANCHA FORMATION IN THE 

SANTA FE EMBAYMENT, RIO GRANDE RIFT, NORTH-CENTRAL NEW MEXICO by

KONING, Daniel J., JOHNSON, 

Peggy.....................................................................................................................24

PRELIMINARY ELECTRICAL RESISTIVITY MODEL ACROSS THE LA BAJADA 

CONSTRICTION FOR HYDROGEOLOGIC FRAMEWORK STUDIES IN THE ESPAÑOLA 

AND SANTO DOMINGO BASINS, NEW MEXICO by RODRIGUEZ, Brian D. and WILLIAMS, 

Jackie M..................................................................................................................25 

INSAR OBSERVED GROUND SUBSIDENCE NEAR BUCKMAN WELL FIELD, NEW 

MEXICO by THOMSEN, Davis; FIALKO, Yuri.................................................................26 

GEOLOGIC FRAMEWORK 

A DATABASE Of GEOCHEMICAL, PETROGRAPHIC, MINERALOGIC, AND 

GEOCHRONOLOGICAL ANALYSIS FOR THE JEMEZ VOLCANIC FIELD TO SUPPORT 

THE 3-D GEOLOGIC MODEL Of THE PAJARITO PLATEAU by Warren, R. G., Cole, G. L. , 

Broxton, D. E., Kluk, E. C., Chipera, S. J., WoldeGabriel, G., Vaniman, D. T. , Snow, M. G. (deceased), 

and Goff, F...............................................................................................................27 

3
ORIGIN OF A BASALT-TO-TRACHYANDESITE/DACITE SUITE IN THE JEMEZ 

VOLCANIC FIELD BY UPPER CRUSTAL CONTAMINATION by BALDRIDGE, W. Scott, 

and WARREN, Richard ..............................................................................................28 

COUNTERCLOCKWISE DECLINATION ANOMALY IN PALEOMAGNETISM OF THE 

PLIOCENE CERROS DEL RIO VOLCANIC FIELD, NEW MEXICO – AN EXPRESSION OF 

LATE RIO GRANDE RIFT DISTRIBUTED SHEAR? by HUDSON, Mark R., THOMPSON, R.A., 

BARBÁ, K.E., MINOR, S.A., and WARREN, R.G. ..............................................................29

GEOLOGIC FEATURES OF THE ABIQUIU QUADRANGLE, RIO ARRIBA COUNTY, NEW 

MEXICO by MALDONADO, Florian, VAN SISTINE, P., and MAESTAS, J. R ...........................30 

LITHOLOGIC CHARACTERISTICS AND AGE RELATIONSHIPS OF THE ANCHA 

FORMATION DEPICTED ON THE GEOLOGIC MAP OF THE AGUA FRIA QUADRANGLE, 

SANTA FE COUNTY, NEW MEXICO by SHROBA, Ralph, R., THOMPSON, R. A., MINOR, S.A., 

GRAUCH, (Tien) V.J.S., and BRANDT, T.R. ......................................................................31 

BASALT OF R9: THE AREALLY MOST EXTENSIVE COGNITIC SERIES Of FLOWS 

WITHIN THE CERROS DEL RIO VOLCANIC FIELD, NEW MEXICO by Warren, 

Richard G. ...............................................................................................................32 

REFERENCES.........................................................................................................33

4
INTRODUCTION 

By Mark R Hudson 

This report presents abstracts of technical studies that pertain to the hydrogeologic framework of the 

Española basin, a major subbasin of the Cenozoic Rio Grande rift. Sediments and interbedded volcanic 

rocks that fill the Española basin comprise an aquifer system that is an important source of water for 

many residents of the basin, including people in the cities of Santa Fe, Española, and Los Alamos as well 

as Native Americans in eleven Pueblos. 

The abstracts describe results of technical studies that were presented either as poster exhibits or oral 

presentations at the forth-annual Española basin workshop, held March 1-2 of 2005 in Santa Fe, New 

Mexico. The principal goal of this workshop was to share information about ongoing studies. 

The Española basin workshop was hosted by the Española basin technical advisory group (EBTAG) 

and sponsored by the U.S. Geological Survey, the New Mexico Bureau of Geology and Mineral 

Resources, and both the Water Research Technical Assistance Office and the Groundwater Protection 

Program of Los Alamos National Laboratory. Abstracts in this report have been grouped into six 

information themes: Basic Water Data, Water Quality and Water Chemistry, Water Balance and 

Stream/Aquifer Interaction, Data Integration and Hydrologic Model Testing, Three-Dimensional 

Hydrogeological Architecture, and Geologic Framework. 

Abstracts in this report submitted by U.S. Geological Survey authors have had their technical content 

peer reviewed before they were included in the report. Technical reviews were not required for abstracts 

submitted by authors outside the USGS, although many did receive peer reviews within their originating 

agencies. Taken together, the abstracts in this report provide a view of the current status of hydrogeologic 

research within the Española basin. 

5
AN UPDATE ON THE SURFICIAL WATER RESOURCES IN THE LOS ALAMOS AREA, 

NEW MEXICO 

DALE, Michael1

, GRANZOW, Kim1, ENGLERT, Dave2, YANICAK, Steve1, FORD-SCHMID, Ralph2, 

LONGMIRE, Patrick3

, and COUNCE, Dale3

1

 NMED DOE Oversight Bureau, 134 State Road 4, Suite A, White Rock, NM 87544, mdale@lanl.gov 

2

 NMED DOE Oversight Bureau, 2905 Rodeo Park Dr East, Bldg. 1, Santa Fe, NM 87505 

3 Los Alamos National Laboratory, MS D469, Los Alamos, NM 87544 

A more complete and accurate understanding of the hydrologic conditions in the Los Alamos area is 

critical to the management and protection of water. During the mid 1990’s, New Mexico Environment 

Department’s Department of Energy Oversight Bureau (the Bureau) recognized that there was not an 

adequate inventory and characterization of local springs and surface-water resources in the Los Alamos 

area. To fill the information gaps, the Bureau identified surficial water resources within the area 

extending from Guaje Canyon to Frijoles Canyon, an area of about 365 square kilometers. The Bureau 

fulfilled its objective by performing field reconnaissance activities during the period 1994 through 2004. 

The survey resulted in the discovery of 89 previously undocumented perennial and ephemeral springs. 

Perennial surface-water flow from both newly discovered and previously identified springs was 

documented and monitored during the study to determine changes in flow rates and stream conditions 

(e.g., length of flow) in response to wet and dry periods. The Bureau collected information and data at 

these water sources including digitally corrected location coordinates via GPS; estimated and measured 

flow rates; geologic discharge units; field parameters such as pH, specific conductance, and in some cases 

major- and minor-hydrochemical constituents; natural and anthropogenic radionuclides such as tritium 

and uranium; and the stable isotopes δD and δ18O. Springs in the study area discharge from shallow, 

intermediate, and deep (regional) aquifers composed of sedimentary and volcanic rock units. The 

shallow-perched springs (perennial) primarily reside in the western portion of the Pajarito Plateau and the 

Sierra de los Valles, and tend to be Na-Ca-HCO3 and Ca-Mg-Na-HCO3 type waters with total dissolved 

solids ranging from approximately 40 to 250 mg/L, depending on the absence or presence of man-induced 

contamination. Spring discharge from intermediate- and regional-depth aquifers tend to be Ca-Na-HCO3 

and Na-Ca-HCO3 type water, and range from approximately 70 to 250 mg/L in total dissolved solids. 

Ground-water ages vary within each aquifer; however, the youthful (<50 years) waters tend to be shallow 

versus older waters occurring at greater depths. Estimated recharge or area of precipitation elevations, as 

indicated by stable-isotope data, for the shallow-perched and intermediate/regional springs range from 

about 2,300 to 2,900 m and 2,100 to 2,400 m respectively. It is estimated that the combined flow of all 

identified perennially flowing shallow-perched springs supply 1.12E+6 cubic meters per year of 

discharge, while the intermediate and regional springs release about 1.04E+6 cubic meters per year. 

6
HYDROGEOLOGIC STUDY OF EL DORADO UTILITIES LIMESTONE PRODUCTION 

WELLS, CANADA DE LOS ALAMOS GRANT, SANTA FE COUNTY, NEW MEXICO 

FROST Jack P.1

;JOHNSON Michael S.2; DUNCAN Don3

1

Hydrology Bureau, N.M. Office of the State Engineer, jfrost@ose.state.nm.us 

2

Hydrology Bureau, N.M. Office of the State Engineer; mjohnson@ose.state.nm.us

3

BlueWater Environmental Consulting, LLC; bluewater@zianet.com

Eldorado at Santa Fe and associated subdivisions have built-out to over 2600 homes in the last 30 years. Prior 

to suburban style development, the area was ranch land with a handful of windmill wells and little perennial 

streamflow. The New Mexico Office of the State Engineer (OSE) recently studied production wells within the 

El Dorado Utilities, Inc. service area. This report describes the hydrogeology and well production from 

bedrock limestone wells developed since 1996. Believed to produce from the Pennsylvanian Madera 

Formation, 3 limestone wells have been developed, and their proximity and hydrographs indicate they 

produce from a common aquifer. 

Eldorado occupies the piedmont plain adjoining the mountain front of the Sangre de Cristo 

Mountains, south of Santa Fe. Beneath the Piedmont sedimentary cover, pre-Tertiary strata dip 10 to 15 

degrees west, shingling off the Sangre de Cristo Mountains. The reservoir is bounded along strike by wells 

that possess modest limestone reservoir qualities, and wells that show the limestone is absent by erosion. 

Updip to the east the limestone onlaps fractured granite bedrock and truncates by erosion. Down dip into the 

Espanola embayment the strata have not been tested. 

Limestone thickness ranges from 0 to 180 feet within less than one mile along strike. Reports by 

drillers and El Dorado Utilities’ geologist indicate the limestone is intensely weathered and fractured. A 

geophysical well log of the discovery well illustrates the productive qualities and shows the porosity 

concentrated near the top of the section. Pumping 250 gpm, total available drawdown in the best well was 

estimated by the EDU consultant at less than 70 feet. Three wells have produced over 2000 acre feet since 

early 1997 and provided more than half of the Utility’s demand in 2003. Average water level decline rates in 

individual wells range from 12% to 21% per year and indicate that at current production rates the available 

water column could be consumed within 10 years. Well yields will diminish before available drawdown 

limits are reached. The Utility recently applied to the OSE for a supplemental well in the same reservoir. A 

customer owned Water and Sanitation District is in the process of purchasing the privately owned utility. 

7
AN UPDATE OF HYDROGEOLOGIC CONDITIONS IN THE SOUTHERN ESPAÑOLA BASIN 

JOHNSON, Peggy S., and KONING, Daniel J. 

N.M. Bureau of Geology and Mineral Resources, 801 Leroy Pl., Socorro, NM 87801 

peggy@gis.nmt.edu

Results of hydrogeologic studies by the New Mexico Bureau of Geology, the New Mexico Office of the 

State Engineer, and Santa Fe County provide an update of hydrologic conditions, water level changes, and 

hydrogeologic properties in the Santa Fe embayment of the southern Espanola Basin. Data collection has 

two aspects: 1) the compilation and collection of water level and aquifer test data; 2) geologic mapping of 

faults and other structures in addition to the gross texture and composition of the basin fill. The geologic 

mapping has been compiled at a scale of 1:50,000 and includes the Tesuque and Ancha Formations of the 

Santa Fe Group, from which the City of Santa Fe obtains most of its groundwater. Results will provide 

improvements to groundwater flow models for water rights administration and well field assessments. 

Interpretation of water level data demonstrates trends in water level changes and defines zones of 

influence surrounding large pumping centers. Combining detailed mapping of faults, USGS aeromagnetic 

data, and expanded water level measurements improves understanding of geologic controls on 

groundwater flow and well-field drawdown. The San Isidro fault and associated fault splays that deform 

ancestral Santa Fe River sediments in the Tesuque Formation west of the City appear to compartmentalize 

drawdowns from the City of Santa Fe well field and produce a strong hydraulic gradient across the fault. 

The gradient anomaly associated with the fault does not appear to extend north into finer-grained facies of 

the Tesuque Formation, but does extend south for a short distance, affecting water levels in coarsegrained Tesuque and Ancha wells. An elliptical shaped zone of influence surrounding the City well field 

may also result from west-dipping beds that concentrate drawdown along strike in a north-south trend. 

Water-level declines associated with the pumping center appear to extend north to Tano Road and south 

beyond Arroyo Hondo. 

A hydrogeologic model, constructed using lithosome-based geologic mapping and aquifer (pump) 

tests, relates aquifer properties to spatial trends in gross basin fill texture and depositional facies. 

Percentile plots of hydraulic conductivity (derived from aquifer tests), sorted by lithosome and textural 

units, provide unit-specific conductivity values to about one order of magnitude. Units dominated by 

small-scale heterogeneity show the greatest range in hydraulic conductivity, up to 2 orders of magnitude. 

Units dominated by relatively coarse-grained, homogeneous channel deposits indicate hydraulic 

conductivities ranging over less than one-half order of magnitude. Increased variability appears to be 

imprinted on some units due to secondary factors such as increased cementation and either fracturing or 

grain-size reduction associated with faults. The total range in conductivity values for Tesuque and Ancha 

Formation sediments is estimated at 0.04 to 160 ft/d. 

Products of this collaborative study include a series of geologic and hydrologic maps, a database 

of well, water level, and aquifer test data from both historic compilations and new data collection, and a 

new water-level monitoring network for the greater Santa Fe area. 

8
OCCURRENCE OF ELEVATED ARSENIC AND FLUORIDE CONCENTRATIONS IN THE 

ESPAÑOLA BASIN 

FINCH, Steven T. 

John Shomaker & Associates, Inc., 2703-B Broadbent Parkway NE, Albuquerque, New Mexico 87107, 

sfinch@shomaker.com

Naturally occurring elevated concentrations of fluoride and arsenic in the Española Basin are associated 

with specific stratigraphic intervals and geochemical environments of the Tesuque Formation. Discretezone sample water-quality data have recently been obtained from well drilling projects in the Santa Fe 

Well Field, Buckman Well Field, Pojoaque area, Española area, and at Chimayo. Distributions of waterquality data were compared with sedimentary sequences, mapped stratigraphy, and structural features to 

identify geochemical flow paths in the Tesuque Formation aquifer. 

Dissolved concentrations of fluoride in the Tesuque aquifer are commonly related to alkaline 

water (pH >9.0, carbonate >50 mg/L). Elevated fluoride is likely controlled by adsorption by kaolinite 

and anion exchange processes. Desorption of fluoride from kaolinite occurs when the pH is greater than 

7.5. Deep test holes in Española and Chimayo have produced alkaline water elevated in both fluoride (5 

to 8 mg/L) and arsenic (0.01 to 0.05 mg/L). 

Elevated arsenic concentrations in the Santa Fe area appear to be associated with sediment 

composition (source) rather than a certain geochemical environment. Radionuclides most commonly 

occur in the Tesuque aquifer system along the flank of the Sangre de Cristo Mountains, which is likely 

related to alluvial slope deposits. Elevated arsenic appears to be associated with occurrence of 

radionuclides, which would support the association with sediment composition. 

9
CONTAMINANT CONCENTRATIONS IN WATER AND BRYOPHYTES FOUND IN FOUR 

SPRINGS LOCATED ALONG THE UPPER RIO GRANDE, NEW MEXICO 

FORD-SCHMID, Ralph1

, DALE, Michael1, ENGLERT, Dave2, and GRANZOW, Kim1

1

NMED DOE Oversight Bureau, 134 State Road 4, Suite A, White Rock, NM 87544, mdale@lanl.gov 

2

NMED DOE Oversight Bureau, 2905 Rodeo Park Dr East, Bldg. 1, Santa Fe, NM 87505 

In November 2003, The RadioActivist Campaign (TRAC) published a report identifying detectable 137Cs 

in water and bryophytes (aquatic mosses) from Spring 4A. Spring 4A is located downgradient of Los 

Alamos National Laboratory (LANL) near the Rio Grande in White Rock Canyon. The report states that 

the detected 137Cs was of LANL origin and was the first confirmed detection of LANL radioactivity 

entering the Rio Grande from a ground-water pathway. In 2004, the New Mexico Environment 

Department’s Department of Energy Oversight Bureau collected and analyzed samples of bryophytes and 

water from Springs 4A and 4C (a nearby spring), and two springs (Big Spring and Hemingway Spring) 

located 70 km and 125 km upstream on the Rio Grande. Springs 4A and 4C show anthropogenic 

impact/influence such as elevated levels of tritium, chloride, nitrate, and perchlorate. While this indicates 

that some fraction of recharge to the springs is of a young age (<50 years) and possibly from past LANL 

discharges, we could not confirm the TRAC detections of 137Cs in water or bryophytes at Springs 4A or 

4C using the best analytical technology available to NMED. 

Springs 4A and 4C discharge from the upper portion of the regional aquifer or from deep perched 

intermediate units beneath the Pajarito Plateau. As noted earlier, Springs 4A and 4C show anthropogenic 

impacts indicating some portion of recharge that is of a shallow/youthful source. The two upstream 

springs discharge from Rio Grande basin sediments and are tritium-free indicating very old water (>100 

years), and are used here to represent background conditions. 

Spring samples were analyzed for 137Cs, tritium, perchlorate, 90Sr, 238Pu, 239/240Pu, major anions, 

and dissolved and total metals. Bryophytes were dried for low-level perchlorate analysis, and reduced to 

ash for analysis for 137Cs and other gamma-emitting radionuclides, 90Sr, 238Pu, 239/240Pu, and total metals. 

Spring samples were purged through a series of filters to determine if colloidal or dissolved 137Cs was 

detectable in the spring waters. Approximately 100 liters of water were filtered through 0.45 and 0.2 μ 

cellulose filters followed by a 3M Empore TM Cesium Rad Disk. The 0.2 filters were digested and 

analyzed to determine if detectable levels of greater than 0.2 μ (and less than 0.45 μ) colloidal bound 

137Cs were present in the water. The Cesium Rad Disks (0.1 μ) were used to extract cesium present in the 

dissolved and/or colloidal <0.2 μ but >0.1 μ fraction. These methods reduced 137Cs detection limits by 

two orders of magnitude for water and bryophytes. 

137Cs and 90Sr were not detected in the spring waters or bryophytes. Perchlorate was not detected 

in bryophytes but was detected in all four spring-water samples. The uranium isotopes 234, 235, and 238 

were detected in all bryophytes and water samples, with the exception that 235U was not detected at 

Springs 4A and 4C water. 239/240Pu was not detected in spring waters but was detected in all bryophyte 

samples. 238Pu may have been detected in both bryophyte and water at Spring 4C but was not detected in 

any other spring or bryophyte sample. Concentrations of gamma emitters detected in bryophytes were 

generally low and near detection limits. When concentrations of metals or radionuclides in both water 

and bryophyte tissue were greater than detection limits, bioconcentration factors are provided. 

10
NATURAL URANIUM IN GROUND WATER IN THE ESPANOLA BASIN 

MCQUILLAN, Dennis1

, LONGMIRE, Patrick2a, JOHNSON, Peggy3, KULIS, Jerzy1, MARTINEZ, 

Fernando1

, COUNCE, Dale2a, and KEATING, Elizabeth2b

1

N.M. Environment Department, PO Box 26110, Santa Fe, NM, 87502, 

dennis_mcquillan@nmenv.state.nm.us

2

Los Alamos National Laboratory, MS D4692a, MS T0032b, Los Alamos, NM 87545 

3

N.M. Bureau of Geology and Mineral Resources, 801 Leroy Pl., Socorro, NM 87801 

Small, laterally discontinuous, roll-front uranium deposits occur in the Tesuque Formation in the 

Espanola Basin. They consist of grain coatings of carnotite and other uranyl minerals that precipitated, 

from uranyl carbonates in ground water, onto carbonaceous sandstone, siltstone, and conglomerate. 

Potential sources of uranium origination include devitrification of volcanic ash, and weathering of 

crystalline Precambrian rocks in the Sangre de Cristo Mountains. Numerous volcanic ash layers occur 

within the Tesuque Formation in this area, and some have been devitrified to clay minerals including 

smectite. Devitrification can occur when volcanic ash (glass) reacts with ground water, and can release 

metals including uranium(VI) into solution. 

Uranium in excess of the drinking-water standard of 

30 μg/L has been detected in approximately 50% of 

the wells tested in the area east of the Rio Grande, 

extending from northern Santa Fe into Espanola. 

Concentrations range from less than 1 μg/L to a 

maximum of 1820 μg/L. Isotopic signatures are 

consistent with natural uranium, not depleted or 

enriched by anthropogenic processes. At least 27 

wells serving 19 public water systems, and 209 

private domestic wells, produce water with 

excessive uranium. Some area residents have 

installed anion exchange and reverse osmosis 

treatment units to decrease uranium in their water 

supply. Anion exchange units installed on two wells 

serving a mobile home park decrease uranium from 

~100 μg/L to less than 5 μg/L. The units use 

proprietary resins to exchange uranyl carbonates 

with chloride, and are regenerated with potassium 

chloride brine. Disposal of waste generated by 

drinking-water treatment systems is an emerging 

issue. We anticipate that the amount of treatment 

waste will increase in 2007 as public water systems 

will be required to comply with the drinking-water standard. In this region, treatment waste is presently 

discharged to on-site septic systems. 

Uranium 

>30 μG/L IN 

~50% OF 

High levels of indoor radon, a uranium decay byproduct, also are widespread in this region. EPA’s 

recommended action level for indoor radon is 4 pCi/L. Concentrations in excess of 20 pCi/L have been 

measured in buildings in the area. 

11
RESULTS FROM WATER QUALITY ANALYSES OF DOMESTIC WELLS IN THE 

POJOAQUE, NAMBE, AND TESUQUE WATERSHEDS, NEW MEXICO 

WUST, Stephen L.1

, LONGMIRE, Patrick2, and COUNCE, Dale3

1

Santa Fe County, 205 Montezuma Ave., Santa Fe, NM 87501, swust@co.santa-fe.nm.us

2

Los Alamos National Laboratory, EES-6 Mail Stop D469, Los Alamos, NM 87545, plongmire@lanl.gov

3

Los Alamos National Laboratory, EES-6 Mail Stop D469, Los Alamos, NM 87545, counce@lanl.gov 

A joint study was conducted to analyze water quality in domestic wells within the Rio Pojoaque, Rio 

Nambe, and Rio Tesuque watersheds. The study was part of a larger evaluation of the need for a regional 

waste water treatment plant. Samples were brought in by the well owners, as part of the New Mexico 

Environment Department (NMED) water fair program. Field parameters including pH, temperature, and 

specific conductance were recorded and a split sample was collected by Los Alamos National Laboratory 

for laboratory analyses for trace elements, trace metals, and general chemistry. Field testing for fluoride, 

iron, nitrate, and sulfate also were conducted by NMED. Wells were located using aerial 

photography/GIS, for later spatial analysis. 

The results showed little nitrate contamination (expected from septic tanks), but widespread 

elevated concentrations of naturally occurring uranium. Uranium concentrations reflected both 

groundwater and chemical (oxidation-reduction) gradients, with higher concentrations nearer the 

mountain-front recharge zone of the Sangre de Cristo Mountains. Groundwater is oxidizing with respect 

to sulfur and uranium based on measured concentrations within the watersheds. Calcium, sodium, and 

bicarbonate are the dominant major ions. Low nitrate concentrations may be due to a combination of 

septic tank and well spacing, depth to groundwater, groundwater mixing, and aqueous and soil 

geochemistry. 

Results suggest residents should become educated on treatment options for their drinking water, 

either through individual treatment units or the development of a community water system. While the 

analytical results demonstrate no immediate need for a regional wastewater treatment plant, one should be 

considered by community planning groups to prevent potential future contamination. 

12
GROUNDWATER PATHWAYS ASSESSMENT: UNCERTAINTY ANALYSIS OF 

CONTAMINANT TRANSPORT FROM MORTANDAD CANYON 

BIRDSELL, Kay H.1

, VESSELINOV, Velimir V.2, DAVIS, Paul A.3, HOLLIS, Diana4, NEWMAN, 

Brent5

1

Hydrology, Geochemistry, and Geology Group, MS T003, Earth and Environmental Sciences Division, 

Los Alamos National Laboratory, Los Alamos NM 87545, khb@lanl.gov

2

Hydrology, Geochemistry, and Geology Group, MS T003, Earth and Environmental Sciences Division, 

Los Alamos National Laboratory, Los Alamos NM 87545. vvv@lanl.gov 

3

EnviroLogic, Inc., Cedar Crest, NM 87008 

4

Classification, MS F674, Security and Safeguards Division, Los Alamos National Laboratory, Los 

Alamos NM 87545 

5

Atmospheric, Climate and Environmental Dynamics Group, MS J495 

Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos NM 8754 

We present an uncertainty analysis of model simulations related to subsurface contaminant transport from 

the Mortandad Canyon within the Los Alamos National Laboratory. We describe how uncertainties are 

quantified and propagated through a series of coupled models and then used to predict likely future 

concentrations at municipal wells. Uncertainties in the contaminant source, infiltration distribution, and 

transport through the unsaturated and saturated zones are analyzed using a series of alternative conceptual 

models and stochastic model parameters. Alternative conceptual models and uncertain model parameters 

are defined to encompass a large range of possible uncertainties associated with potential groundwater 

flow and transport based on existing data and expert knowledge about the system. In all, eight alternative 

conceptual models having up to 38 uncertain model parameters are analyzed. For each conceptual model 

and related stochastic parameter realization, we simulate contaminant transport from the contaminant 

outfall to water-supply wells over the next 1000 years. Specifically, the groundwater transport of the 

nonsorbing species perchlorate, nitrate and tritium, which were released as surface water from the 

radioactive liquid-waste treatment facility, is predicted. We also make probabilistic predictions of 

contaminant concentrations that could be observed in new monitoring wells that will be drilled in the 

Mortandad Canyon in 2005. 

13
ASSESSING GROUND-WATER RECHARGE THROUGH THE PAJARITO FAULT ZONE, 

UPPER PAJARITO CANYON, LOS ALAMOS, NEW MEXICO 

DALE, Michael1

, GOFF, Fraser2, GRANZOW, Kim1, LONGMIRE, Patrick3, and COUNCE, Dale3 

1

NMED DOE Oversight Bureau, 134 State Road 4, Suite A, White Rock, NM 87544, mdale@lanl.gov 

2

Earth and Planetary Sciences Dept., University of New Mexico, Albuquerque, NM 87131 

3

Los Alamos National Laboratory, EES Division, MS D469, Los Alamos, NM 87545 

Physical processes of ground-water recharge to aquifers beneath the Los Alamos region are not well 

understood. In particular, there is limited knowledge concerning the role of the Pajarito fault zone as a 

ground-water recharge mechanism (conduit and/or barrier). The present conceptual hydrogeologic model 

for the Pajarito fault zone is incomplete because of the paucity of data. The New Mexico Environment 

Department’s Department of Energy Oversight Bureau (the Bureau) has initiated a study to determine if 

surface water loss in the upper reach of Pajarito Canyon is occurring within the Pajarito fault zone. 

Hydrologic, hydrochemical, and isotopic constituents (δD, δ18O, and 3

H) are being analyzed for samples 

collected at the fault expression (PA-10.6) and from downgradient springs. General hydrologic conditions 

include a perennial surface-water reach that flows west to east for approximately 2.4 km upstream of the 

Pajarito fault zone. This reach is supplied by seep and spring discharges at an elevation of about 2,740 m. 

Under baseflow conditions, the reach abruptly terminates at PA-10.6 at an elevation of 2,470 m. 

Approximately 1.9 km downstream of PA-10.6, three perennial springs discharge from horizontal 

fractures and/or surge beds at an elevation of about 2,330 m. Various rock units of the upper Bandelier 

Tuff crop out at PA-10.6 and the springs. From 1997 through 2001, periodic bucket-and-stopwatch-flow 

measurements were made at PA-10.6 and below the springs. Recharge and discharge (water balance) 

measurements were nearly equivalent. Isotopic data collected in 1999 suggest that two of the three 

aforementioned springs (Homestead and Starmer Springs) are chemically and isotopically similar to the 

PA-10.6 waters. Some chemical differences were noted, however, including elevated concentrations of 

Cl, SO4, and Na, which may be attributed to salt-laden-runoff infiltration along State Road 501. The third 

spring (Bulldog Spring) contains elevated concentrations of 3

H and major ions, and is slightly enriched in 

δD and δ18O compared to water at PA-10.6, suggesting a different recharge source. Solutes produced 

from the Cerro Grande fire in May 2000 introduced chemical tracers that showed a direct link between 

water at PA-10.6 and the downgradient springs. Subsequent summer-monsoon flooding in the upper reach 

of Pajarito Canyon impacted water quality at PA-10.6. Hydrochemical changes at PA-10.6 included an 

approximate four-fold increase in dissolved HCO3, SO4, Ca, K, Mg, Mn, Sr, and total dissolved solids. In 

less than one month, these tracers were observed at Homestead and Starmer Springs. Slight 

hydrochemical changes observed at Bulldog Spring indicated that some connection in ground-water flow 

was established. Lower concentrations of these tracers were also measured during the summers of 2001 

and 2003. During 2005, Los Alamos National Laboratory investigators and the Bureau will finalize this 

project by collecting and analyzing additional samples for 3

H, 4He, Ar, Ne, δD, δ18O, and major ions to 

better define the hydraulic connectivity between waters at PA-10.6 and the springs. These findings will 

provide additional insights to the role of the Pajarito fault zone controlling ground-water recharge in the 

study area. 

14
AN INVESTIGATION OF RECHARGE TO THE ESPAÑOLA BASIN UTILIZING NOBLE 

GASES, GROUNDWATER AGES, AND TEMPERATURE DATA 

MANNING, Andrew1

, KEATING, Elizabeth2, CAINE, Jonathan Saul3, LANDIS, Gary4

1

U.S. Geological Survey, P.O. Box 25046, MS 964, Denver, CO 80225, amanning@usgs.gov 

2

MS T003, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, 

NM 87545, ekeating@lanl.gov 

3

U.S. Geological Survey, P.O. Box 25046, MS 964, Denver, CO 80225 

4

U.S. Geological Survey, P.O. Box 25046, MS 963, Denver, CO 80225 

Like most intermountain basins in the western U.S., recharge to the Española Basin in northern New 

Mexico is uncertain. The recharge component with the greatest uncertainty is subsurface inflow from 

adjacent mountains (mountain-block recharge, or MBR). Existing numerical models suggest that MBR 

constitutes a large fraction of recharge, particularly on the eastern side of the basin where about half of 

the estimated recharge is MBR from the Sangre de Cristo Mountains. In contrast, recent data from the 

Colorado Front Range, which receives more annual precipitation and is composed of similar Precambrian 

metamorphic crystalline rocks, indicate no significant MBR to the adjacent Denver Basin, calling into 

question the high MBR estimates for the Sangre de Criso Mountains. 

Noble gas, groundwater age, and temperature data are being collected from water wells in the 

Española Basin in an attempt to independently estimate MBR and improve constraints on recharge to the 

basin. Noble gases will be used to determine recharge temperature, a reliable indicator of recharge 

elevation. Groundwater ages will be determined using 3

H/3He and 14C methods in an attempt to discern 

groundwater-age gradients, which are a direct function of total recharge. Groundwater temperature, a 

potential indicator of total fluid flux, will also be measured where possible. These data will then be used 

in conjunction with an existing 3-D, finite element, coupled heat and fluid transport model, to improve 

constraints on recharge and better understand geological controls on mountain-block fluid circulation. 

Preliminary samples have been collected from wells along a roughly E-W transect across the basin. 

Initial analyses of the sensitivity of the temperature, recharge temperature, and age distributions to 

variations in MBR have also been performed. Most of the data will be collected in 2005 and then 

interpreted and reported in 2006. 

15
VALUE OF USGS WATER SUPPLY PAPER 1525 TO CURRENT ESPAÑOLA BASIN 

GEOHYDROLOGY STUDIES 

SPIEGEL, Zane 

POB 1541, Santa Fe NM 87504, ecimino@cybermesa.com 

An intensive multidisciplinary field study of geology and hydrology of the Santa Fe, NM area was 

initiated in July 1951 by staff of divisions of the USGS and NMIMT, in cooperation with the NM Office 

of the State Engineer (NMOSE). Most of the detailed geological fieldwork was done in 1951-2 by 

NMBMMR staff (B. Baldwin, F. Kottlowski, and W. Bundy). Ground-water data were collected and 

interpreted as a method of "hydro-geophysical" exploration by USGS staff Z. Spiegel, E. Barrows, and T. 

Gerber, followed by traditional subsurface geophysical exploration (NMIMT geophysicists H. Winkler 

and others). Spiegel and Baldwin were principal authors and editors. The report was released to open-file 

in 1958 and printed in 1963 as USGS WSP 1525. 

The most valuable features of the report and subsequent updates and augmentation, especially to 

the authors, their colleagues, and students were, (1) recognition of differences in structure and lithofacies 

of sheets of surficial beds (Ancha Formation and overlying stream-related terrace deposits) 

unconformable on older westerly-dipping beds (Tesuque Formation). Lithofacies sequence of the Tesuque 

Formation suggests progressive inversion by erosion and local re-deposition of pre-existing strata (middle 

to early Tertiary age; Paleozoic and Precambrian-age rocks) to the south-east and east; (2) mapping of the 

base of the more permeable Ancha Formation that filled ancestral erosion valleys eroded across 

underlying less-permeable beds; (3) aiding interpretation of 3D ground-water flow patterns in sequences 

of monoclinal strata partially or fully incised by superposed streams or buried valleys, and (4) solution of 

the generally accepted inflow / outflow equation for the portion of the study area that contributed to a 

zone of measurable spring flow and readily estimated evapotranspiration, which resulted in a long-term 

annual average of about 1/2 inch of natural recharge to an area of 114 sq. miles (average altitude 6300 

feet, average precipitation 13 inches) due to surface runoff of heavy storms into swales and arroyos. 

The co-operative agreement was weakened by restrictions (1) by NMBMMR, geologic mapping 

of only four 7.S-min. quadrangles, and (2) by the State Engineer, that water rights matters should not be 

discussed. The first restriction was offset in part by (a) Baldwin's reconnaissance west of the Turquoise 

Hill quadrangle and later work on igneous rocks of that area with M. Sun (NMBMMR); (b) general 

reconnaissance to the north with colleagues, including a field conference with Luna Leopold, T. Galusha, 

and others; and (c) study by Spiegel of geohydrology west of the Rio Grande (1949), traverses of arroyos 

and ridges between Tesuque and Nambe, on foot and horse, 195258. These observations, plus data from 

ongoing USGS studies in those areas, helped extension of water-level contours in PI. 7 of WSP 1525 to 

areas north of the area of detailed study. The second restriction was offset in part by discussion in WSP 

1525 of general ground-water principles; local data on ground-water recharge and natural and artificial 

aquifer discharge; effects of wells on water levels, springs, and streams; aquifer testing; and a simple 

method of extension of well life. In addition, in 1956-7, 1962-3, and from 1974 to the present, Spiegel 

prepared and had published (or released to open file) numerous reports with basic data and concepts that 

augmented the restricted published report. These reports are readily available in Santa Fe. 

16
GROUNDWATER TEMPERATURES AND HEAT FLOW IN THE ESPAÑOLA BASIN 

Keating, Elizabeth1

, Zyvoloski, George1, Manning, Andrew2

1

MS T003 Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, 

NM 87545. ekeating@lanl.gov 

2

U.S. Geological Survey, P.O. Box 25046, MS 73, Denver, CO, 80225, amanning@usgs.gov 

Although groundwater temperatures have been used primarily to determine geothermal gradients, they 

can also be used to infer aspects of the groundwater flow system. In the Espanola Basin, we are using a 

combination of temperature data and basin-scale coupled heat-flow and groundwater flow modeling to 

address questions concerning large-scale recharge fluxes and deep upwelling of thermal waters. Better 

understanding of recharge fluxes is pertinent to water supply calculations; understanding upwelling of 

thermal waters is pertinent to water quality issues such as elevated uranium, fluoride, and arsenic. We 

present temperature data and preliminary simulation results that will provide a starting point for more 

detailed analyses using new noble gas data (Manning et al., 2005). 

Using a limited dataset of eight wells in the basin, we estimate the average thermal gradient to be 

20o

C/km. By calibrating a model of heat flow in the basin assuming conduction only (no groundwater 

flow), we were able to match temperature gradients in the wells reasonably well, although the simulated 

gradient was significantly higher than the measured gradient in one well (SF-2, near the Rio Grande). 

By adding groundwater flow to the simulations, temperatures in the upper portion of the aquifer were 

significantly reduced, suggesting that the impact of cooler recharge water may be measurable even in the 

center portion of the basin, far from recharge areas. This effect improved the match between measured 

and simulated temperatures in the SF-2 well. These preliminary results suggest that conduction, although 

an important mechanism for heat flow in the basin, does not completely dominate measured gradients and 

thus temperature profiles may be a useful tool for understanding recharge fluxes. Future work will test 

alternative conceptual models of recharge distribution and determine whether temperature data can be 

used quantitatively to distinguish between them. 

Andrew H. Manning, Elizabeth H. Keating, Jonathan Saul Caine, and Gary P. Landis, 2005, An 

Investigation of Recharge to the Española Basin Utilizing Noble Gases, Groundwater Ages, and 

Temperature Data, 4th Annual Española Basin workshop, Santa Fe, NM. 

17
AN UPDATE ON THE CITY OF SANTA FE’S REGIONAL GROUNDWATER FLOW MODEL 

MCCURRY, Gordon N.1

, MCCLUSKEY, Mark J.2, BORCHERT, Claudia3

1

CDM, 1331 17th Street, Suite 1200, Denver, CO 80202, mccurryg@cdm.com; 

2

CDM, 1331 17th Street, Suite 1200, Denver, CO 80202, mccluskeymj@cdm.com; 

3

City of Santa Fe Water Division, 801 W. San Mateo Rd Santa Fe, NM 87505 

The City of Santa Fe has continued to develop its groundwater flow model of the region to assist the City 

in evaluating water resources alternatives. Its existing model covers the area presented in the McAdaWasiolek (1988) and Frenzel (1995) models. Refinements were made by the City to the Frenzel (1995) 

model to increase grid density in a region extending outward from its Buckman Wellfield and to include a 

9th model layer to represent the alluvial aquifer beneath the Rio Grande, Rio Pojoaque and Tesuque 

Creek. The existing City model also updated annual pumping from existing municipal and private wells 

through the year 2000, simulated the rivers with the Stream package of MODFLOW, and underwent and 

extensive model calibration in the vicinity of the Buckman Wellfield. 

Recent updates to the City’s numerical groundwater flow model include expanding the model 

boundaries to the west, east and south to incorporate Galisteo Creek, refining the density of the model 

grid in the region incorporating the Santa Fe River, and refining the model layering to incorporate recent 

geophysical and geologic mapping undertaken by the USGS and the NMBMGR. The updated City 

model has also included aquifer pumping test and water level data compiled by the NMBMGR. These 

data have been used to revise the aquifer hydraulic conductivity distributions for the Tesuque Aquifer and 

to create a detailed set of water level observations used in model calibration. In addition, the City model 

has transitioned to a monthly time step for recent years to provide a more rigorous calibration that takes 

into account seasonal and short-term variations in pumping and streamflow. 

18
LATERAL DISPLACEMENT VARIATION AND FAULT INTERACTION ON THE PAJARITO 

PLATEAU, RIO GRANDE RIFT, NEW MEXICO 

LEWIS, Claudia J., GARDNER, Jamie N., LAVINE, Alexis, and RENEAU, Steven L., and SCHULTZ, 

Emily S. 

Earth and Environmental Science Division, Los Alamos National Laboratory, Los Alamos NM 87544, 

clewis@lanl.gov

We propose a geometric model of the Pajarito fault (PF) system using displacement-length profiles to 

answer questions about the fault system’s geometry. In areas of detailed mapping, we measured 

stratigraphic throw on displaced contacts of subunits of the Tshirege Member of the Bandelier Tuff (Qbt). 

As scarp height has been shown to be a reasonable approximation of stratigraphic separation in this area 

(Gardner et al., 2001), beyond the limits of detailed mapping we measured throw on the displaced top of 

the Bandelier Tuff using a LIDAR 4-ft grid (Carey and Cole, 2001). In areas of substantial distributed 

deformation, we estimated total throw by integrating the effects of tilt of bedding, folding, and small 

offset faults. 

At the surface, the Pajarito fault is not a single shear surface but a complex zone of deformation 

with considerable lateral variation in structural style. Near Cochiti Canyon, total throw on two main 

down-east normal faults splays is more than 120 m on Bandelier Tuff. Maximum throw occurs near 

Frijoles Canyon on two splays with >200 m total displacement. At Water Canyon, the PF zone is a faulted 

monocline with >120 m throw, a prominent basal graben, and hanging wall bedding that dips toward the 

fault. At Cañon de Valle, the basal graben is well-expressed but no monocline is present. From Pajarito 

Canyon to Rendija Canyon, down-east displacement is accommodated by monoclinal folding and smalloffset distributed normal faulting with ~35 m maximum throw on any single mapped fault. In the vicinity 

of the town of Los Alamos, the Rendija Canyon fault (RCF) and Guaje Mountain fault (GMF) are 

subparallel to and partially overlap the trace of the PF, accounting for a combined 75 m down-west throw. 

Between Rendija and Chupaderos Canyons, no discrete PF has been mapped. At Chupaderos Canyon, 

polarity changes to the down-east Santa Clara segment of the PF, continuing past Santa Clara Canyon as a 

single normal fault with >100 m down-east throw on Qbt. 

Pronounced displacement gradients occur on the PF, RCF, and GMF where they overlap. This is 

also the location of an early Pleistocene fan complex and the Diamond Drive graben. The distributed 

nature of faulting in this sector, compared to the southern sector of the PF, suggests linkage between the 

PF and the RCF-GMF and that faulting at the surface has not yet completely localized onto a main PF. 

In aggregate, the Pajarito fault system is composed of a principal fault plane with branched 

secondary fault planes at the vertical termination (ground surface) and en echelon secondary fault planes 

at the lateral terminations (e.g., Marchal et al., 2003). Total length is >46 km. Previous paleoseismic 

investigations indicate that different fault traces along the PF system have ruptured at different times. This 

may be a function of the distributed nature of faulting associated with upward propagation of the PF. 

19
HYDROGEOLOGIC CROSS SECTIONS OF THE ESTANCIA GROUNDWATER BASIN, 

CENTRAL NEW MEXICO 

HAWLEY, John W. 

Hawley Geomatters, P.O. Box 4370, Albuquerque, NM 87196-4370 hgeomatters@qwest.net

Ongoing investigations of the hydrogeologic framework of the Estancia groundwater basin (EGWB), and 

its brackish-water resources and aquifer-recharge mechanisms require a much more detailed conceptual 

and physical models of basinwide hydrogeology than have heretofore been developed. This poster 

presentation includes a set of nine new hydrogeologic cross-basin sections that illustrate the major 

stratigraphic and tectonic elements of the topographically closed and geohydrologically undrained

EGWB between its northernmost edge (35° 12.5' N) and the southern basin area east of Mountainair (34° 

32.5' N). Each section ends at the divide between the eastern Estancia Basin watershed and the Pecos 

River (surface/subsurface) drainage basin. Base-line elevation is Mean Sea Level, original map scale is 

1:100,000, and vertical exaggeration for hydrostratigraphic emphasis is 10x. However, draft sections were 

also prepared at 1:1 scale to make sure that structural inferences and interpretations were reasonable 

approximations of “conceptual and spatial reality.” Sections and base maps are now available in Adobe 

Illustrator® format; and they should be regarded as “works-in-progress” that are available for peer review 

and subject to revision as more subsurface geologic and geophysical baseline information is acquired. 

Primary information sources for this hydrogeologic-model update include: 1) NM Bureau of Mines 

[Geology] & Mineral Resources and Univ. of Texas-El Paso geologic and geophysical investigations of 

deep-subsurface conditions (Broadhead,1997, NMBMMR Bull. 157; Barrow and Keller,1994, GSA Spec. 

Paper 291; Foster and Stipp,1961, NMBMMR Circ. 57); 2) NMBMMR hydrogeologic studies ( Smith, 

1957, Ground Water Rpt. 5; Titus, 1973, Open-file Report 69); and 3) unpublished data compiled for 

NMBM&MR engineering and environmental-geology programs in the EGWB area (O-F Rpts. 245 and 

258). 

Hydrogeologic-framework interpretations illustrated in the cross sections confirm Broadhead’s 

(1997) observation that the thin alluvial and lacustrine deposits (<100 m—late Neogene) of the central 

Estancia topographic basin conceal three interconnected, but distinct structural subbasins (Galisteo, West 

Estancia, and Perro). The latter are bounded by complex shear and dip-slip fault zones primarily produced 

by late Paleozoic and Neogene compressional and extensional tectonism. Major aquifer systems comprise 

upper Pennsylvanian carbonate rocks and gypsiferous carbonate and clastic sequences of Permian to 

Triassic age. The deep Perro (Ancestral Rocky Mountain-ARM) subbasin, beneath Laguna del Perro and 

adjacent playa-lake depressions of the south-central Estancia Basin, is the target area for R&D activities 

related to brackish-groundwater development and “concentrate” disposal. Primary mechanisms for ARM

and Laramide structural-subbasin formation are still being debated (e.g. dextral vs. sinistral shear; see 

1999 reviews by Pazzaglia et al., Woodward et al., and Karlstrom et al. in NMGS Guidebook 50); but the 

fracture and dissolution porosity/permeability associated with subbasin-bounding deformation zones are 

clearly the major factors influencing groundwater flow and quality in bedrock-aquifer systems throughout 

the Estancia groundwater basin. 

20
INTRABASINAL ARCHITECTURE OF THE SOUTHERN ẼSPANOLA BASIN 

KONING, Daniel, J.1

, READ, Adam, S., GRAUCH, (Tien) V.J.S. 3, and MINOR, Scott A. 4

1

New Mexico Bureau of Geology and Mineral Resources, 801 Leroy Place, Socorro, NM, 87801, 

dkoning@nmt.edu

2

New Mexico Bureau of Geology and Mineral Resources, 801 Leroy Place, Socorro, NM, 87801, 

adamread@gis.nmt.edu

3

U.S. Geological Survey, MS 964, Federal center, Denver CO, 80225, tien@usgs.gov

4

U.S. Geological Survey, MS 980, Federal center, Denver CO, 80225, sminor@usgs.gov 

Recent geologic mapping, examination of well cuttings, high-resolution aeromagnetic data, and other 

available geophysical data have refined our understanding of the general structure within the southern 

Española Basin. Our focus for this presentation is on the intrabasinal faults and folds within the basin, 

many of which coincide with aeromagnetic lineaments. In places, these intrabasinal faults appear to 

profoundly influence groundwater flow and aquifer compartmentalization (Johnson et al., 2004). 

North of the Santa Fe River, the general structure is that of a west-tilted half-graben, bounded on the 

west by the Pajarito fault zone near Los Alamos. Within the half-graben are numerous extension-related 

structures of interest. Midway across the basin, northwest of Tesuque Pueblo, there is a significant westfacing monocline with an interpreted 1000-1500 m of structural relief. This monocline is cut by 

numerous faults of variable displacement, and continues to the north into what Kelley (1978) referred to 

as the Barrancos monocline and to the south as a series of typically west-down, en echelon and 

anastomosing faults. We propose calling this structure the Barrancos fault system because it is 

continuous with the Barrancos monocline to the north. Faults bound the eastern margin of the basin as 

well, but appear to have relatively minor offset during rift tectonic activity. In addition to the Barrancos 

fault system, numerous west- and east-down faults are present basinward from the mountain front. Westdown faults are locally coincident with west-facing monoclines. 

The area south of the Tesuque–Santa Fe drainage divide is generally referred to as the Santa Fe 

embayment. Here, the general geologic structure is that of a north-northeast-plunging syncline. The 

eastern limb of the syncline is cut by normal faults of unknown offset. Many of these faults have been 

mapped at the surface but some are inferred entirely from the aeromagnetic data. In many cases, 

aeromagnetically inferred faults coincide with mapped fault segments. This reflects a convergent 

evolution of both field mapping and interpretation of the aeromagnetic data during our collaboration on 

this project. In some cases the aeromagnetically interpreted structures are offset from the mapped faults. 

This discordance is likely due either to a higher contrast of magnetic properties at depth (perhaps 

indicating subsurface fault geometry) or due to multiple fault strands that were unrecognized on the 

surface. 

21
TEXTURAL AND THICKNESS VARIABILITY Of THE ANCHA FORMATION IN THE 

SANTA FE EMBAYMENT, RIO GRANDE RIFT, NORTH-CENTRAL NEW MEXICO 

KONING, Daniel J., JOHNSON, Peggy 

N.M. Bureau of Geology & Mineral Resources, 801 Leroy Place, Socorro, NM 87801; 

dkoning@nmt.edu, peggy@gis.nmt.edu

The Ancha Formation consists of arkosic sand, silty sand, gravel, and mud that was deposited in the Santa 

Fe embayment during Pliocene and early Pleistocene time. Reaching a thickness of ~90 m, the Ancha 

Formation unconformably overlies the Tesuque Formation. The lower part of the Ancha Formation is 

locally saturated and forms an important aquifer for the greater Santa Fe area. We assess the spatial 

variability of the gross texture of the Ancha Formation and how this variability may influence 

hydrogeologic properties of this thin but important aquifer. Also, we present structural contour maps 

showing our best estimate of the elevation of the Ancha Formation basal contact, and use these maps to 

discuss the thickness variability of this unit and the three-dimensional shape of its lower contact. 

The Ancha Formation was deposited by two different depositional systems. South of approximately 

Interstate 25 and north of the Santa Fe River, this formation was deposited by relatively small drainages 

on an alluvial slope along the southwestern flank of the Sangre de Cristo Mts. Here, sediment is 

characterized by poorly to moderately sorted, silty or muddy sand (mostly very fine- to medium-grained 

sand with subordinate coarse- to very coarse-grained sand) that contains scattered pebbles. This finer 

grained sediment, referred to as extra-channel sediment, is interbedded with various proportions of 

channel deposits that are composed of medium- to very coarse-grained sand and gravel. The overall 

texture of these alluvial-slope deposits (estimated by the proportion of the coarse channels relative to 

extra-channel sediment) becomes finer away from the mountain front. Saturated alluvial slope sediment 

is found only in the western part of the embayment, where the Ancha Formation is finer-grained and 

probably less permeable than correlative deposits near the mountain front. North of the Santa Fe River, 

the alluvial-slope sediment is relatively thin (18-25 m) and generally unsaturated. 

Alluvium deposited by the ancestral Santa Fe River, the second depositional system of the Ancha 

Formation, is generally coarser than the alluvial slope sediment in the central and western parts of the 

embayment. Gravel is generally clast-supported, poorly sorted, and contains 50-70% pebbles and 30-50% 

cobbles. This unit contains relatively minor, discontinuous beds of floodplain sediment (silty or clayey 

very fine to fine sand). Based on available pumping test data, in the western part of the embayment this 

unit has higher hydraulic conductivity and yield values compared to laterally adjacent alluvial slope 

deposits. 

Our interpretation of the base of the Ancha Formation using well data suggests that it is irregular, 

having a relief of up to ~40 m with significant paleovalleys. The Ancha Formation appears to thicken 

westward across a broad fault zone in the eastern part of the embayment. Cross-sections indicate that the 

slope of the basal Ancha Formation contact flattens west of La Cienega. This flattening may be due to 

increased discharge to the ancestral Santa Fe River from springs near La Ciengea, or it may be the result 

of eastward tectonic tilting of the footwall of the La Bajada fault. Stratigraphic relations suggest that 

local base level changes associated with the emplacement of the Cerros del Rio basalt field could have 

contributed to much of the aggradation of the Ancha Formation. However, 19-25 m of Ancha Formation 

ancestral Santa Fe River deposits lay beneath the basalt flows at the western edge of the Caja del Rio 

Plateau. This indicates that aggradation of the Ancha Formation commenced before emplacement of these 

basalts at ~3 Ma. The lack of deformation of the Ancha Formation and correlation to other weakly 

deformed Plio-Pleistocene deposits in the northern Rio Grande rift suggests that climatic influences might 

have played a role in the aggradation of this unit. 

22
PRELIMINARY ELECTRICAL RESISTIVITY MODEL ACROSS THE LA BAJADA 

CONSTRICTION FOR HYDROGEOLOGIC FRAMEWORK STUDIES IN THE ESPAÑOLA 

AND SANTO DOMINGO BASINS, NEW MEXICO 

RODRIGUEZ, Brian D. and WILLIAMS, Jackie M. 

U.S. Geological Survey, Box 25046, MS 964, Denver, Colorado 80225 

brod@usgs.gov

Geophysical methods that detect variations in subsurface lithology and structure are important for 

understanding controls on groundwater within the La Bajada constriction, the critical area of transition 

between the Española basin on the north and the Santo Domingo basin on the south. The magnetotelluric 

(MT) method is a deep-sensing geophysical method designed to map changes in electrical resistivity with 

depth that are related to these subsurface variations. The resistivity of geologic units is largely dependent 

upon their fluid content, porosity, fracturing, and conductive mineral content. Sixteen MT stations were 

collected from 2002 to 2004 to help understand the subsurface within the La Bajada constriction, along a 

northwest to southeast profile from the Pajarito fault on the northwest to the La Bajada fault on the 

southeast. Across the constriction, MT soundings have provided additional constraints on the relative 

position of basement and thickness of Paleozoic-Mesozoic and Tertiary sedimentary rocks, based on 

resistivities expected from certain geologic units. For example, moderately low resistivities (10 to 50 

ohm-m) are expected for saturated Tertiary sediments that have low clay content, whereas very low 

resistivities (1 to 5 ohm-m) are expected for Mesozoic shales. High resistivities are expected for 

near-surface Tertiary basalt, andesite and rhyolite volcanic rocks (100 to 5,000 ohm-m) and for buried 

Paleozoic carbonates (200 to 500 ohm-m). In the footwall of the Pajarito fault zone, we model less than 

1-km thickness of moderately low resistivities we interpret to be Tertiary sediments underlain by a few 

hundred meters of very low resistivity Mesozoic shales. Southeast of the Pajarito fault zone, the inferred 

Paleozoic-Mesozoic boundary is down-dropped to the southeast over 1 km to a depth of about 2 km 

beneath Dome Road well, where interpreted Tertiary sediments are about 1.5-km thick and inferred 

Mesozoic shales are about 0.7-km thick. Southeast of Cochiti fault, interpreted Mesozoic shales are about 

1.5-km thick, while inferred Tertiary sediments are only about 0.1-km thick. Southeast of an unknown 

fault, southeast of Cochiti fault, interpreted Tertiary sediments are about 0.5-km thick and inferred 

Mesozoic shales are about 0.7-km thick, increasing to over 1-km thickness over the Cerrillos uplift. 

Southeast of another unknown fault, near the Cerrillos uplift, interpreted Mesozoic shales are less than 

1-km thick, while inferred Tertiary sediments are less than 0.5-km thick, but thickening to the southeast; 

the La Bajada constriction appears to be bounded by this unknown fault on the southeast side and by the 

Pajarito fault on the northwest side. The Mesozoic shales on the northwest side of the Cerrillos uplift have 

an apparent northwest dip, while the shales on the southeast side have an inferred southeast dip. Two 

more inferred unknown faults appear on the northwest side of the profile where interpreted Tertiary 

sediments are about 0.5-km thick, but no significant thickness of Mesozoic shales was detected. 

23
INSAR OBSERVED GROUND SUBSIDENCE NEAR BUCKMAN WELL FIELD, NEW 

MEXICO 

THOMSEN, Davis; FIALKO, Yuri, 

IGPP Scripps Institution of Oceanography, UCSD, MC 0225 9500 Gilman Dr. San Diego CA 92093-

0225, dthomsen@ucsd.edu 

Interferometric Synthetic Aperture Radar (InSAR) measurements of surface deformation at the Buckman 

well field near Los Alamos, New Mexico over a time period of 1993-2000 show localized ground 

subsidence over an area of 25km2 with a maximum line of sight displacement rate of 1.5cm/yr. Based on 

the spatial correlation of the ground subsidence anomaly and the Buckman well field, we infer that this 

subsidence is a result of water withdrawal from the underlying aquifer. In 2001, a half-mile fissure with 

nearly twenty centimeters of offset developed on the periphery of the observed deformation anomaly. 

This fissure formation episode is coincident with increasing water withdrawal from the well field. 

However, deformation rates inferred from satellite interferometry do not show an increase over the time 

period before failure (1997-2000), compared to the deformation rates observed in the earlier epochs 

(1993-1997). We interpret these observations as indicating an anelastic response of the upper crustal 

rocks prior to yielding caused by the water withdrawal and concomitant ground compaction. 

In order to characterize the depth and geometry of the deformation source, we employ two 

methods: 1) we simulate the source as a distribution of point sources the inferred production depths of 

individual wells and 2) we approximate the source by a prolate pressurized ellipsoid (Yang et al. 1988). 

Both models assume that the host rock deformation is elastic. Although the interpretation of surface 

deformation data is non-unique, we are able to provide constraints on the source geometry for the 

deformation signal. 

We first model the deformation signal as a superposition of point sources in an elastic halfspace 

(Mogi 1958). The location of individual sources corresponds to the locations of individual wells and the 

depth is placed at a typical well depth of 500m. Additionally, the strength of each source is assumed to be 

proportional to the relative volumetric rate of water withdrawal. A scale factor for pressure was chosen 

such that the amplitude of the deformation signal is similar to the observed one. This model fails to 

explain the observations. Indeed, deformation that is occurring at the highest observed rates is north of 

the northernmost well location. These results imply that there is subsurface source continuity and 

pressure drop extends to an area greater than the well field itself. 

In another set of models, we solve for the surface expression of a contracting prolate spheroid 

(Yang et al. 1988). The spatial shape of the deformation signal is accommodated in a more satisfactory 

fashion using this approach. We find that the spheroid best fitting the observed deformation field has a 

major axis of 5km and a minor axis of 1km and is at a depth of 1.1km. The model spheroid is in 

approximately the same north-south orientation as the canyon (alluvium) and is dipping at an angle of 7o. 

This prolate source model successfully explains the main signatures of the observed deformation field. 

This model also suggests source continuity to the west of the Rio Grande, implying that there is little 

connectivity between the river and aquifer. 

24
A DATABASE OF GEOCHEMICAL, PETROGRAPHIC, MINERALOGIC, AND 

GEOCHRONOLOGICAL ANALYSIS FOR THE JEMEZ VOLCANIC FIELD TO SUPPORT 

THE 3-D GEOLOGIC MODEL Of THE PAJARITO PLATEAU 

WARREN, R. G. 1, Cole, G. L. 2, BROXTON, D. E. 2, KLUK, E. C. 2, CHIPERA, S. J. 2, 

WOLDEGABRIEL, G. 2, VANIMAN, D. T. 2

, SNOW, M. G. (deceased) 2, and GOFF, F. 2

1

Group EES-11, MS F665, rgw@lanl.gov, 

2

Group EES-6, MS D462), Los Alamos National Laboratory, Los Alamos, NM, 87545 

Within the south-central part of the Pajarito Plateau, the Laboratory occupies about 2% of the 5000 square 

kilometer Jemez volcanic field (JVF). Cole et al. (2005) have constructed a 3-D geologic model to 

provide a computational framework for assessment of contaminant migration from sources within the 

Laboratory. We have integrated geological information used to support this 3-D geologic model into a 

large relational database. The ~3500 geochemical, petrographic, mineralogic, and geochronological 

analyses collected from the JVF presently within the database have been applied during a period of 10 

years to create, develop, and refine this 3-D model of volcanic and sedimentary rocks. These data are 

partly published within literature cited by the database. 

The database complies with protocols of Structured Query Language (SQL), allowing construction of 

relationships among these data, from micrometer-diameter spots chemically analyzed by microprobe 

within individual mineral grains, to stratigraphic identities for rock columns within drill holes and outcrop 

that exceed 1 km thickness in some cases. The database establishes rules for the proper relationships 

among the different types of data by defining a hierarchy for primary keys beginning with a location ID, 

through sample and split ID, and ending with replicate ID. These rules and examples for their application 

are published by Warren et al. (2003), available online at http://queeg.ngdc.noaa.gov/seg/geochem/swnvf 

for the southwestern Nevada volcanic field (SWNVF). The database for the SWNVF, which has an area 

twice as large as the JVF, has a structure identical to that for the JVF, and so provides a convenient source 

of comparative information. 

The database is particularly robust in petrographic analyses, utilizing new techniques devised by Warren 

et al. (2003) that apply detailed documentation to provide precise and accurate analyses for minor and 

trace constituents. Petrographic analyses also include qualitative (descriptive) analyses obtained when 

support is unavailable for detailed analyses. Petrographic analyses can be related to whole-rock chemical 

analyses, whole-rock mineral analyses, and mineral identification and chemistry via electron microprobe 

analysis. Whole rock chemical analyses were obtained mostly by X-ray fluorescence (XRF), many with 

FeII/FeIII via titration (WC), and by neutron activation analysis (NAA). Most whole-rock mineral 

analyses employed quantitative X-ray diffraction (QXRD) analysis. In addition to mineral chemical 

analyses, electron microprobe analyses provide qualitative analyses within the database that confirm or 

correct mineral analyses documented during petrographic analysis. 

We developed the database to facilitate application of extensive and varied types of information to 

geologic problems within the Laboratory portion of the Pajarito Plateau. We hope that the great volume 

of complex, interrelated data and data types within this data set will also encourage use for comparisons 

with other geologic datasets. We also hope that non-petrographers, non-geologists, or others will apply 

these data to test and develop geological or hydrogeologic models, statistical methods, data mining 

techniques, exploratory data analysis, and visualization techniques. 

25
ORIGIN OF A BASALT-TO-TRACHYANDESITE/DACITE SUITE IN THE JEMEZ 

VOLCANIC FIELD BY UPPER CRUSTAL CONTAMINATION 

BALDRIDGE, W. Scott, and WARREN, Richard G. 

Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New 

Mexico, 87545, sbaldridge@lanl.gov and rgw@lanl.gov 

Magmatic compositions in large, long-líved volcanic fields typically evolve through a variety of 

petrogenetic processes. Determining their relative roles may be difficult because (1) multiple processes 

may act simultaneously at a single volcano, (2) different processes may produce similar compositional 

results, and (3) individual processes may differ significantly at different volcanoes. To isolate the major 

processes and avoid the complex overprinting of multiple processes in the main Jemez volcanic field 

(JVF), we obtained whole-rock major- and trace element compositions and mineral compositions from a 

small basalt-to-trachyandesite/dacite volcanic field (Cerros del Rio, CDR) adjacent to the main JVF. 

Lavas of the CDR field were erupted during development of the middle to upper crustal magma chamber 

(4-1 Ma) that resulted in formation of Toledo and Valles calderas at 1.6 Ma and 1.2 Ma respectively, but 

were not affected by mixing with the main chamber. 

The mafic end members of this suite typically range from basanite/alkali olivine basalt to 

hawaiite (SiO2 ~ 44-52%; Na2O+K2O ~ 4.2-6.3%), likely derived from an ocean-island-basalt (OIB)-

modified lithospheric source (McMillan, 1998). Compositions range to trachyandesite and dacite (SiO2 ~ 

65-67%; Na2O+K2O ~ 6.9-7.2%) (classification of Le Bas et al., 1986). Trace elements (e.g., Th, Zr) are 

not well correlated with major elements. Phenocrysts range from olivine and plagioclase in the least 

evolved lavas to high- and low-Ca pyroxene and sodic plagioclase in the intermediate to silicic members. 

Primitive members of this series contain gabbroic xenoliths and evolved members are typified by 

quartzofeldspathic xenoliths and by xenocrysts of quartz and feldspar, which we infer were derived from 

middle to upper crust. Using only whole-rock compositions observed in the CDR, we can model the 

major-element compositional range assuming removal of observed phenocryst phases coupled with 

addition of observed xenolithic/xenocrystic material. Modeling of trace elements, assuming world-wide 

average values (Rudnick and Gao, 2004), is not compatible with a significant lower crustal component in 

these magmas. 

We conclude that the simplest model for the origin of this basalt-to-trachandesite/dacite suite is 

fractional crystallization of OIB-modified basalt combined with significant assimilation of middle to 

upper crustal rocks. Although we cannot rule out more complicated models involving partial fusion of 

lower crust and mixing of magmas, we do not think they are necessary or likely. 

26
COUNTERCLOCKWISE DECLINATION ANOMALY IN PALEOMAGNETISM OF THE 

PLIOCENE CERROS DEL RIO VOLCANIC FIELD, NEW MEXICO - AN EXPRESSION OF 

LATE RIO GRANDE RIFT DISTRIBUTED SHEAR? 

HUDSON, M.R. 1, THOMPSON, R.A. 1, BARBA, K.E. 1, MINOR, S.A. 1, and WARREN, R.G.2

1

U.S. Geological Survey, MS 980, Denver, CO 80225, mhudson@usgs.gov 

2

Los Alamos National Laboratory, ESS-11/MS F665, Los Alamos, NM, 87545 

Distributed strike-slip shear is difficult to detect, particularly where shear is accommodated by verticalaxis rotation of fault blocks. Declination anomalies in paleomagnetic data have become the principal 

evidence used to detect such rotations. 

The >700 sq km Cerros del Rio volcanic field (CdRVF) in northern New Mexico lies within the Rio 

Grande rift and overlaps the boundary between Espanola and Santa Domingo basins. The CdRVF 

comprises mostly flat-lying lava and pyroclastic deposits erupted from multiple basaltic to dacitic 

volcanic centers between 2.7 Ma and 1.1 Ma. We have sampled CdRVF units for paleomagnetic analysis 

at 51 sites distributed over the field. Extensive alternating-field demagnetization was required to isolate 

primary magnetization in many of these sites due to overprints from past lightning strikes. A mean 

direction of 49 sites is D = 346.3, I = 51.5, a95 = 4.5, k = 22. These data should average geomagnetic 

secular variation; they are distributed subequally between Gauss-chron normal-polarity sites and younger 

mostly reversed-polarity sites of the Matuyama chron and they sample units erupted from at least 12 

volcanic centers. Compared to an expected direction calculated from a 0-Ma pole of Besse and Courtillot 

(2002, 2003), the CdRVF mean direction has a significantly counterclockwise (CCW) declination (-9.0° 

+/- 6.3°), whereas the inclination is slightly shallow (4.2° +/- 3.6°). The CCW declination anomaly 

confirms earlier findings by Brown and Golombek (1986) based on fewer paleomagnetic data; they 

attributed the declination anomaly to CCW rotation of the entire Española basin. Alternatively, CCW 

rotation may be linked to local shear developed as interaction increased between faults of the Espanola 

and Santo Domingo basins during known, late-stage narrowing of Rio Grande rifting. 

 

27
GEOLOGIC FEATURES OF THE ABIQUIU QUADRANGLE, RIO ARRIBA COUNTY, NEW 

MEXICO 

MALDONADO, Florian, VAN SISTINE, Paco, and MAESTAS, James, R. 

U. S. Geological Survey, P.O. 25046, MS 980, Denver, Colorado 80225 fmaldona@usgs.gov

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 occurs within the Abiquiu embayment, an early extensional 

basin of the Rio Grande rift. Rocks exposed include continental Mesozoic rocks of the Colorado Plateau, 

Cenozoic basin-fill deposits, and volcanic rocks. Mesozoic units are Triassic Chinle Formation, Jurassic 

Entrada Sandstone, and Todilto Limestone Member of the Wanakah Formation. Cenozoic rocks are the 

Eocene El Rito Formation, Oligocene-Miocene Abiquiu Formation (upper and lower members), and 

Miocene Chama-El Rito and Ojo Caliente Sandstone Members of the Tesuque Formation of the Santa Fe 

Group. The upper member of the Abiquiu Formation has been dated at ~27-23 Ma (Peters, 1999; Peters 

and McIntosh, 2000) using the 40Ar/39Ar method. Volcanic rocks include the Lobato Basalt (~10-8 Ma; 

Bachman and Mehnert, 1978; Manley and Mehnert, 1981), El Alto Basalt (~3 Ma; Manley and Mehnert, 

1981; Baldridge and others, 1980), and intermediate lavas of the Tschicoma Formation (~7-2 Ma; 

Gardener and Golf, 1984). Quaternary deposits consist of inset ancestral axial and tributary Rio Chama 

deposits, Holocene floodplain alluvium, fan and pediment alluvium, and landslide colluvium. Axial 

terrace benches are found approximately 30 to 115 m above the present Rio Chama floodplain. One set 

of terraces at about 115 m height is as old as 640 ka, based on the presence of the Lava Creek B ash east 

of the map area. Delineation of terrace alluvium was modified from Gonzalez (1993) and Gonzalez and 

Dethier (1993). 

Tributary gravels beneath the Lobato and El Alto Basalts contain clasts of a fluvial system that 

probably represent several ancestral Rio Chama courses. Tops of these gravels are about 580 m and 395 

m, respectively, above the modern Rio Chama. Clasts consist mostly of subrounded to well-rounded 

Paleozoic quartzite and granite, Tertiary volcanics, and traces of Pedernal Chert Member of the Abiquiu 

Formation. Gravels containing quartzite and Pedernal chert also are present under the Sierra Negra (~5 

Ma; Baldridge and others, 1980) and Black Mesa (Servilleta Basalt flow) (~4-3 Ma; Manley, 1976; 

Laughlin and others, 1993) lavas located northeast and east of the map area, respectively. 

The Cañones fault zone separates the Abiquiu embayment from the Colorado Plateau. Time of 

development of the embayment is constrained by the presences of two basalts on the Colorado Plateau 

with centers in the embayment. The Lobato Basalt (10-8 Ma) is displaced across the Cañones fault and 

the El Alto Basalt (~3 Ma) is not (Maldonado, 2004). 

28
LITHOLOGIC CHARACTERISTICS AND AGE RELATIONSHIPS OF THE ANCHA 

FORMATION DEPICTED ON THE GEOLOGIC MAP OF THE AGUA FRIA QUADRANGLE, 

SANTA FE COUNTY, NEW MEXICO 

SHROBA, Ralph, R., THOMPSON, Ren, A., MINOR, Scott, A., GRAUCH, (Tien) V.J.S., and 

BRANDT, Theodore, R. 

US Geological Survey, MS 980, PO Box 25046, Denver Federal Center, Denver, CO 80225-0046. 

rshroba@usgs.gov 

Recent 1:24,000-scale geologic mapping of the Agua Fria 7.5-minute quadrangle near Santa Fe indicates 

that the Ancha Formation (Spiegel and Baldwin, 1963) consists mostly of loose to weakly consolidated, 

stream-deposited, slightly pebbly sand to slightly cobbly, pebble gravel. The Ancha locally consists of 

sandy silt, silty very fine to medium sand, and pebbly sandstone that is weakly cemented by calcium 

carbonate. These sediments form thin (about 0.3-4 m) lenses and lenticular beds that are rich in 

Precambrian granite clasts and feldspar. The Ancha commonly is mantled by thin sheetwash deposits and 

is poorly exposed. Westward-flowing streams originating in the nearby Sangre de Cristo Range, graded to 

the Rio Grande, deposited the Ancha on northwest- to southwest-dipping Miocene sediments of the 

Tesuque Formation. The Ancha thins from south to north across the quadrangle. The Ancha is about 60 m 

thick near the southern boundary of the quadrangle, but thins to about 3–6 m in the northern part of the 

quadrangle where it forms pediment deposits. These pediment deposits project westward beneath the base 

of hydromagmatic deposits at the base of basaltic lava flows of the Cerros del Rio volcanic field (CdRvf). 

Elsewhere deposition of the Ancha Formation predates, was contemporaneous with, and postdates lava 

flows and related deposits of the CdRvf. The upper 30 m or more of the Ancha in the western part of the 

quadrangle contain varying amounts of predominately reworked basaltic tephra about 0.5–10 mm in 

diameter. The tephra was produced by hydromagmatic explosions contemporaneous with the eruption of 

extensive early phase (2.6–2.7 Ma) basaltic lavas of the CdRvf. Reworked rhyolitic pumice (1.5-1.6 Ma) 

erupted from the nearby Jemez Mountains is locally present in the upper part of the Ancha. Buried soils 

in the Ancha have thin, eroded, clay-enriched (Bt) horizons and stage I to III, carbonate-enriched (Btk, 

Bk, and K) horizons about 15–60 cm thick. These soils record depositional hiatuses of at least a few 

thousand to several tens of thousands of years. Geomorphic relationships near the Agua Fria quadrangle 

suggest as much as ~ 10-15 m of incision of the Ancha Formation by the Santa Fe River since about 2.6–

2.7 Ma. 

29
BASALT OF R9: THE AREALLY MOST EXTENSIVE COGNITIC SERIES Of FLOWS 

WITHIN THE CERROS DEL RIO VOLCANIC FIELD, NEW MEXICO 

WARREN, Richard G. 

Group EES-11, MS F665, Los Alamos National Laboratory, Los Alamos, NM, 87545, rgw@lanl.gov 

Drilling to define the regional aquifer within the south-central part of the Pajarito Plateau and collection 

and analysis of numerous samples from outcrop have established a wide aerial distribution for a cogenetic 

series of basalt flows here named basalt of R9. The flows are at least 12 km long north to south, and 9 km 

wide, and therefore the most areally extensive cogenetic flows within the Cerros del Rio volcanic field. 

These flows provide age dates by 39Ar/40Ar of 2.4 Ma and they are reversely magnetized within the 

Matuyama I geomagnetic chron of the Pliocene epoch. Extensive chemical and petrographic analyses 

define four very closely similar flow groups within basalt of R9: from base to top these are lower and 

upper hawaiite and lower and upper tholeiite. The upper flows for each chemical type have modest 

contents of plagioclase phenocrysts, averaging 5.4% in the hawaiite and 6.3% in the tholeiite, whereas the 

lower flows are very poorly plagioclase-phyric, averaging 0.6% and 0.7%. Olivine phenocrysts are 

common within basalt of R9 but clinopyroxene is generally absent and probably xenocrystic when 

present. The lower tholeiite generally exhibits a very distinctive ophitic texture in thin section and is the

areally most extensive flow group. Most regional wells provide all four groups but hawaiite has not been 

positively identified in outcrop.

The datum for basalt of R9 provides excellent control throughout an extensive region to assess 

structural activity that might affect groundwater flow within this portion of the Rio Grande Rift, on its 

final leg before reaching the Rio Grande. Three km NNW from its eruptive center, exposed immediately 

northwest from White Rock, the top forms a strikingly flat surface that covers 20 km2. These flat data 

constrain structural tilting within this structural block to <0.2 degrees and faulting to <15 m offset during 

the past 2.4 million years, allowing calculation of the primary depositional dip for overlying Tshirege 

Tuff. The top is 50-100 m lower west of this flat, unfaulted block. These lower elevations for the top of 

basalt of R9 are associated with higher elevations for the base of the unit, so do not represent flow down 

into a pre-existing paleovalley, but more likely reflect post-2.4 Ma faulting. 

The base of the unit shows generally consistent elevations except within a central paleovalley, 

where elevations are up to 160 m lower than those within adjacent holes that penetrate the rim. The 

paleovalley may have narrow exits both north and south, and could be entirely erosional, but it might 

instead represent a structural basin, or result from a combination of structure and erosion. Within this 

paleovalley are river gravels, sediments interpreted as slope deposits, and older mafic units of the Cerros 

del Rio that occur immediately beneath basalt of R9; these substrata indicate that the paleovalley defines 

an ancestral course of the Rio Grande. The hawaiite filled this paleovalley, enabling the overlying 

tholeiite to flood the region, redirecting the Rio into its present course between Los Alamos and Ancho 

Canyons. The total depth of this paleovalley is unknown, but the axis may well extend below the regional 

water table, possibly influencing groundwater flow eastward through this feature. 

30
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33