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S. E. Church

Publications and source records attributed to S. E. Church.

At least 19 recordsLinked to original sources
USGS2010

Quantifying restoration success and recovery in a metal-polluted stream: A 17-year assessment of physicochemical and biological responses

Evaluating the effectiveness of stream restoration is often challenging because of the lack of pre-treatment data, narrow focus on physicochemical measures and insufficient post-restoration monitoring. Even when these fundamental elements are present, quantifying restoration success is difficult because of the challenges associated with distinguishing treatment effects from seasonal variation, episodic events and long-term climatic changes.2. We report results of one of the most comprehensive and continuous records of physical, chemical and biological data available to assess restoration success for a stream ecosystem in North America. Over a 17 year period we measured seasonal and annual changes in metal concentrations, physicochemical characteristics, macroinvertebrate communities, and brown trout Salmo trutta populations in the Arkansas River, a metal-contaminated stream in Colorado, USA.3. Although we observed significant improvements in water quality after treatment, the effectiveness of restoration varied temporally, spatially and among biological response variables. The fastest recovery was observed at stations where restoration eliminated point sources of metal contamination. Recovery of macroinvertebrates was significantly delayed at some stations because of residual sediment contamination and because extreme seasonal and episodic variation in metal concentrations prevented recolonization by sensitive species. Synthesis and applications. Because recovery trajectories after the removal of a stressor are often complex or nonlinear, long-term studies are necessary to assess restoration success within the context of episodic events and changes in regional climate. The observed variation in recovery among chemical and biological endpoints highlights the importance of developing objective criteria to assess restoration success. Although the rapid response of macroinvertebrates to reduced metal concentrations is encouraging, we have previously demonstrated that benthic communities from the Arkansas River remained susceptible to other novel anthropogenic stressors. We suggest that the resistance or resilience of benthic macroinvertebrate communities to novel stressors may be effective indicators of restoration success that can account for the non-additive (e.g. synergistic) nature of compound perturbations. ?? 2010 The Authors. Journal compilation ?? 2010 British Ecological Society.

Journal of Applied Ecology↗
USGS2010

Lead isotope database of unpublished results from sulfide mineral occurrences — California, Idaho, Oregon, and Washington

The Pb isotope database for sulfide deposits and occurrences in the Western United States was funded by the Mineral Resources Program, U.S. Geological Survey (USGS). Reports on Pb isotope data from Alaska were published in Church and others (1987a) and Gaccetta and Church (1989). The primary objectives of the project were three-fold: * To utilize Pb isotope signatures, in conjunction with the regional mapping, to assess the relative ages and to categorize the types of deposits studied, * To relate the Pb isotope and trace-element geochemical signatures of specific deposits and occurrences to ore-forming processes, and * To use the Pb isotope data to correlate lithotectonic terranes within the northern Cordillera. The report by Church and others (1987b) shows how this fingerprinting methodology can be applied to trace the offset of lithostratigraphic terranes

California, Idaho, Oregon, Washington↗
USGS2009

Environmental effects of hydrothermal alteration and historical mining on water and sediment quality in Central Colorado

The U.S. Geological Survey conducted an environmental assessment of 198 catchments in a 54,000-km2 area of central Colorado, much of which is on Federal land. The Colorado Mineral Belt, a northeast-trending zone of historical base- and precious-metal mining, cuts diagonally across the study area. The investigation was intended to test the hypothesis that degraded water and sediment quality are restricted to catchments in which historical mining has occurred. Water, streambed sediment, and aquatic insects were collected from (1) catchments underlain by single lithogeochemical units, some of which were hydrothermally altered, that had not been prospected or mined; (2) catchments that contained evidence of prospecting, most of which contain hydrothermally altered rock, but no historical mining; and (3) catchments, all of which contain hydrothermally altered rock, where historical but now inactive mines occur. Geochemical data determined from catchments that did not contain hydrothermal alteration or historical mines met water quality criteria and sediment quality guidelines. Base-metal concentrations from these types of catchments showed small geochemical variations that reflect host lithology. Hydrothermal alteration and mineralization typically are associated with igneous rocks that have intruded older bedrock in a catchment. This alteration was regionally mapped and characterized primarily through the analysis of remote sensing data acquired by the ASTER satellite sensor. Base-metal concentrations among unaltered rock types showed small geochemical variations that reflect host lithology. Base-metal concentrations were elevated in sediment from catchments underlain by hydrothermally altered rock. Classification of catchments on the basis of mineral deposit types proved to be an efficient and accurate method for discriminating catchments that have degraded water and sediment quality. Only about 4.5 percent of the study area has been affected by historical mining, whereas a larger part of the study area is underlain by hydrothermally altered rock that has weathered to produce water and sediment with naturally elevated geochemical baselines.

Colorado↗
USGS2009

Aquatic ecosystems in Central Colorado are influenced by mineral forming processes and historical mining

Stream water and sediment toxicity to aquatic insects were quantified from central Colorado catchments to distinguish the effect of geologic processes which result in high background metals concentrations from historical mining. Our sampling design targeted small catchments underlain by rocks of a single lithology, which allowed the development of biological and geochemical baselines without the complication of multiple rock types exposed in the catchment. By accounting for geologic sources of metals to the environment, we were able to distinguish between the environmental effects caused by mining and the weathering of different mineralized areas. Elevated metal concentrations in water and sediment were not restricted to mined catchments. Impairment of aquatic communities also occurred in unmined catchments influenced by hydrothermal alteration. Hydrothermal alteration style, deposit type, and mining were important determinants of water and sediment quality and aquatic community structure. Weathering of unmined porphyry Cu-Mo occurrences resulted in water (median toxic unit (TU) = 108) and sediment quality (TU = 1.9) that exceeded concentrations thought to be safe for aquatic ecosystems (TU = 1). Metalsensitive aquatic insects were virtually absent from streams draining catchments with porphyry Cu-Mo occurrences (1.1 individuals/0.1 m2 ). However, water and sediment quality (TU = 0.1, 0.5 water and sediment, respectively) and presence of metalsensitive aquatic insects (204 individuals/0.1 m2 ) for unmined polymetallic vein occurrences were indistinguishable from that for unmined and unaltered streams (TU = 0.1, 0.5 water and sediment, respectively; 201 individuals/0.1 m2 ). In catchments with mined quartz-sericite-pyrite altered polymetallic vein deposits, water (TU = 8.4) and sediment quality (TU = 3.1) were degraded and more toxic to aquatic insects (36 individuals/0.1 m2 ) than water (TU = 0.4) and sediment quality (TU = 1.7) from mined propylitically altered polymetallic vein deposits. The sampling approach taken in this study distinguishes the effects of different mineral deposits on ecosystems and can be used to more accurately quantify the effect of mining on the environment.

Conference Paper↗
USGS2008

Central Colorado Assessment Project - Application of integrated geologic, geochemical, biologic, and mineral resource studies

Central Colorado is one of the fastest-growing regions in the Western United States. Population along the Front Range increased more than 30 percent between 1990 and 2000 (http://www.demographia.com/db-metro3newworld.htm) with some counties within the study area, such as Park County, experiencing greater than 100-percent growth (http://www.censusscope.org/us/s8/rank_popl_growth.html). This growth has caused tremendous demand for natural resources and has created challenging land-management issues related to the interface between wilderness and urban expansion. Management of this wilderness/urban interface will benefit from current digital geoscience information collected by the U.S. Geological Survey (USGS) Central Colorado Assessment Project that began in 2003. Approximately 20,800 square miles (53,800 km2) of land divided almost equally between the public and private sectors were part of the assessment. The study area includes much of the Colorado Mineral Belt, a northeast-trending zone that contains 30 economically significant metal deposits. Historically, the area provided much of Colorado's metal production. The only active gold and molybdenum mines in Colorado lie within the study area. Recently, metal and uranium exploration activity has increased sharply in response to record prices for metals and uranium. This further underscores the need for up-to-date geoscience information presented in compatible GIS databases to facilitate rapid land-management decisions. Cooperative studies by USDA Forest Service, National Park Service supported by the USGS Mineral Resources Program (MRP), and National Cooperative Geologic Mapping Programs (NCGMP) contributed to the mineral-resource assessment and included regional geologic mapping at the scale 1:100,000, collection and geochemical studies of stream sediments, surface water, and bedrock samples, macroinvertebrate and biofilm studies in the riparian environment, remote-sensing studies, and geochronology. Geoscience information available as GIS layers has improved understanding of the distribution of metallic, industrial, and aggregate resources, location of areas that have potential for their discovery or development, helped to understand the relation of tectonics, magmatism, and paleohydrology to the genesis of the metal deposits in the region, and provided insight on the geochemical and environmental effects that historical mining and natural, mineralized rock exposures have on surface water, ground water, and aquatic life.

Fact Sheet↗
USGS2005

Questa baseline and premining ground-water quality investigation. 8. Lake-sediment geochemical record from 1960 to 2002, Eagle Rock and Fawn Lakes, Taos County, New Mexico

Geochemical studies of lake sediment from Eagle Rock Lake and upper Fawn Lake were conducted to evaluate the effect of mining at the Molycorp Questa porphyry molybdenum deposit located immediately north of the Red River. Two cores were taken, one from each lake near the outlet where the sediment was thinnest, and they were sampled at 1-cm intervals to provide geochemical data at less than 1-year resolution. Samples from the core intervals were digested and analyzed for 34 elements using ICP–AES (inductively coupled plasma–atomic emission spectrometry). The activity of 137 Cs has been used to establish the beginning of sedimentation in the two lakes. Correlation of the geochemistry of heavy-mineral suites in the cores from both Fawn and Eagle Rock Lakes has been used to develop a sedimentation model to date the intervals sampled. The core from upper Fawn Lake, located upstream of the deposit, provided an annual sedimentary record of the geochemical baseline for material being transported in the Red River, whereas the core from Eagle Rock Lake, located downstream of the deposit, provided an annual record of the effect of mining at the Questa mine on the sediment in the Red River. Abrupt changes in the concentrations of many lithophile and deposit-related metals occur in the middle of the Eagle Rock Lake core, which we correlate with the major flood-of-record recorded at the Questa gage at Eagle Rock Lake in 1979. Sediment from the Red River collected at low flow in 2002 is a poor match for the geochemical data from the sediment core in Eagle Rock Lake. The change in sediment geochemistry in Eagle Rock Lake in the post-1979 interval is dramatic and requires that a new source of sediment be identified that has substantially different geochemistry from that in the pre-1979 core interval. Loss of mill tailings from pipeline breaks are most likely responsible for some of the spikes in trace-element concentrations in the Eagle Rock Lake core. Enrichment of Al 2 O 3 , Cu, and Zn occurred as a result of chemical precipitation of these metals from ground water upstream in the Red River. Comparisons of the geochemistry of the post-1979 sediment core with both mine wastes and with premining sediment from the vicinity of the Questa mine indicate that both are possible sources for this new component of sediment. Existing data have not resolved this enigma.

New Mexico↗
USGS2002

Water and sediment study of the Snake River watershed, Colorado, Oct. 9-12, 2001

The Snake River watershed, located upstream from Dillon Reservoir in the central mountains of Colorado, has been affected by historical base-metal mining. Trout stocked in the Snake River for recreational purposes do not survive through the winter. Sediment cores analyzed by previous investigators from the reservoir revealed elevated concentrations of base metals and mercury. We collected 36 surface water samples (filtered and unfiltered) and 38 streambed-sediment samples from streams in the Snake River watershed. Analyses of the sediment and water samples show that concentrations of several metals exceed aquatic life standards in one or both media. Ribbon maps showing dissolved concentrations of zinc, cadmium, copper, and manganese in water (0.45-micron filtered and corrected for the ameliorating effect of hardness), and copper, cadmium, and zinc in sediment indicate reaches where toxic effects on trout would be expected and stream reaches where toxicity standards for rainbow, brown, and brook trout are exceeded. Instantaneous loads for sulfate, strontium, iron, cadmium, copper, and zinc were calculated from 0.45-micron-filtered water concentrations and discharge measurements were made at each site. Sulfate and strontium behave conservatively, whereas copper, cadmium, and zinc are reactive. The dissolved copper load entering the reservoir is less than 20 percent of the value calculated from some upper reaches; copper is transferred to suspended and or streambed sediment by sorption to iron oxyhydroxides. Higher percentages of zinc and cadmium reach the reservoir in dissolved form; however, load calculations indicate that some of these metals are also precipitated out of solution. The most effective remediation activities should be concentrated on reducing the dissolved loads of zinc, cadmium, and copper in two reaches of lower Peru Creek between the confluence with the Snake River and Cinnamon Gulch. We analyzed all streambed sediment for mercury and selected streambed-sediment and reservoir core samples for lead isotope signatures. Results indicate that the mercury anomaly in the reservoir sediment was not from any known source in the Snake River, Blue River, or Tenmile Creek watersheds. Its source remains an enigma.

Colorado↗
USGS1999

Determination of pre-mining geochemical conditions and paleoecology in the Animas River Watershed, Colorado

Determination of the pre-mining geochemical baseline in bed sediments and the paleoecology in a watershed impacted by historical mining activity is of utmost importance in establishing watershed restoration goals. We have approached this problem in the Animas River watershed using geomorphologic mapping methods to identify old pre-mining sediments. A systematic evaluation of possible sites resulted in collection of a large number of samples of pre-mining sediments, overbank sediments, and fluvial tailings deposits from more than 50 sites throughout the watershed. Chemical analysis of individual stratigraphic layers has resulted in a chemical stratigraphy that can be tied to the historical record through geochronological and dendochronological studies at these sites. Preliminary analysis of geochemical data from more than 500 samples from this study, when coupled with both the historical and geochronological record, clearly show that there has been a major impact by historical mining activities on the geochemical record preserved in these fluvial bed sediments. Historical mining activity has resulted in a substantial increase in metals in the very fine sand to clay sized component of the bed sediment of the upper Animas River, and Cement and Mineral Creeks. Enrichment factors for metals in modern bed sediments, relative to the pre-mining sediments, range from a factor of 2 to 6 for arsenic, 4 to more than 10 for cadmium, 2 to more than 10 for lead, 2 to 5 for silver, and 2 to more than 15 for zinc. However, the pre-mining bed sediment geochemical baseline is high relative to crustal abundance levels of many orerelated metals and the watershed would readily be identified as a highly mineralized area suitable for mineral exploration if it had not been disturbed by historical mining activity. We infer from these data that the water chemistry in the streams was less acidic prior to historical mining activity in the watershed. Paleoentologic evidence does not indicate a healthy aquatic habitat in any of the stream reaches investigated above the confluence of the Animas River with Mineral Creek (fig. 1) prior to the impact of historical mining activity. The absence of paleoentologic remains is interpreted to reflect the poor preservation regime of the bed sediment materials sampled. The fluvial sediments sampled in this study represent higher energy environments than are conducive to the preservation of most aquatic organisms including fish remains. We interpret the sedimentological data to indicate that there has been substantial loss of riparian habitat in the upper Animas River above Howardsville as a result of historical mining activity.

Colorado↗
USGS1998

Evidence for Proterozoic and late Cretaceous-early Tertiary ore-forming events in the Coeur d'Alene district, Idaho and Montana

New 40 Ar/ 39 Ar age spectra on sericite and lead isotope data on tetrahedrite, siderite, galena, bournonite, and stibnite, together with previously published isotopic, geochemical, and geologic studies provide evidence for two major vein-forming events in the Coeur d'Alene district and surrounding areas of the Belt basin. The data suggest that the zinc- and lead-rich veins (e.g., Bunker Hill and Star-Morning mines) formed in the Proterozoic (1.0 Ga), whereas the silver-rich veins (e.g., Silver belt mines), antimony veins (e.g., U.S. Antimony mine), and gold-bearing quartz veins (Murry subdistrict) formed in Late Cretaceous to early Tetitary time.

Economic Geology↗