Problem Statement

Regions underlain by black shale, especially in arid terrains such as that of the Mancos Shale in Colorado and Utah, pose significant problems for land use managers. In many such instances, insufficient data exist for resource and land managers to formulate scientifically supportable policies for (1) the sustainable development of mineral and energy resources contained in black shale terrains and (2) the stewardship of black shale landscapes. In general, the major geologic processes responsible for the evolution of the landscapes and their associated resources are understood. However, there is a lack of detailed understanding that is required to quantify the processes or to create predictive models that can accurately take into account changes in land use, climate, national resource need, and a variety of other factors.Mancos Shale landscapes of the western United States, especially in the Upper Colorado River Basin, have become a focal point for the need for scientific information supporting sound land-use policies. This need has risen in prominence primarily because of (1) increased and changing demands for land use and (2) issues related to the bioavailability of selenium and the salinity of surface- and ground-water. Concurrently, there has been an increased awareness within the scientific community of a need to better understand processes leading to the concentration and dispersal of both economically important elements and environmentally sensitive elements (ESE) in black shale sequences.Black shale (organic-rich, generally dark-colored, fine-grained, sedimentary rock deposited in very low oxygen conditions) can be both a source of mineral wealth and a cause for environmental concern. The natural resources associated with black shale have some obvious and some not so obvious forms. Oil and gas are the most obvious of the resources that originate in black shale; some of the World’s largest mineral deposits (syngenetic and epigenetic) are hosted by black shale; black shale is the probable source of metals found in some deposits; a variety of industrial minerals, such as clay and phosphate, are derived from black shale; and in some environments black shale-derived soil provides necessary nutrients for specific crops and plant populations. In addition to their economic and ecologic value, some black shale sequences have potential for negative impacts. Many black shale sequences are non-point sources for potentially toxic elements, such as arsenic, selenium, chromium, and mercury. Additionally, some black shale-hosted ore deposits and associated waste rock can be point sources for a variety of toxicants. Slope stability and a variety of other engineering issues further contribute to the list of problems encountered in black shale landscapes. Dispersal or fixation of elements occurs through many mechanisms. Erosional processes are of greatest concern to Federal, State, and local governmental land managers of Mancos landscapes. There are insufficient data to permit the assessment (even in reliable qualitative terms) of the impact of changes in land use (for example, off-highway motor vehicle use, grazing, irrigation, etc.) or climate. Developing a quantitative understanding of landform evolution and the rates at which sediment and the ESE are released to surface waters, the atmosphere, and ground water is critical to understanding both natural and anthropogenic (human) impacts on black shale landscapes. Such an understanding will help in the determination of a “normal” baseline of sediment and chemical loading.Communicating scientific results to the end user and visualizing data as the results are generated is a challenging task, especially in consideration of our need to generate and interpret large arrays of complex data. The visualization process helps in the interpretation and is a powerful tool in communicating results to technical audiences as well as to non-specialists.

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Objectives

The broad objectives of this project are (1) to use science to help define some of the issues requiring the attention of science, resource, and land-use managers who deal with black shale terrains, (2) to provide applicable, scientifically valid information that can be used to formulate resource and land-use management policies for Mancos Shale landscapes, and (3) to assure that the information provided is transportable/applicable to black shale landscapes that are not specifically studied.

In some cases, conflicting scientific data and interpretation cause difficulties in determining when an issue is a problem or not. For instance, there is debate about the toxic affects of selenium on fish communities in the Upper Colorado River Basin. This project or a related one will help to resolve that issue and, through on-going discussion between managers and scientists, will help to differentiate between those issues that are truly problematic and those that are not. In the long-term, the project will contribute to the development of predictive models that can be used to evaluate black shale landscapes in terms of their economic resource potential and their environmental sensitivity.Short-term (5 year) objectives include:

1. Maintenance and extension of the communication between project scientists and personnel (both managers and scientists) of land management agencies, such as the BLM, Bureau of Reclamation (BOR), U.S. Fish and Wildlife Service (USFWS), and other stakeholders. Many of the proposed activities are the outgrowth and continuation of a BLM-USGS cooperative project, “Developing Coordinated Science Activities in Support of Land Management in the Mancos Shale Badlands of the Gunnison Gorge National Conservation Area.”
   
   
2. Development of a model describing the erosion of Mancos Shale. Several tasks will develop the data necessary to understand (a) the processes that result in the physical and chemical erosion of the Mancos Shale and (b) the affects of changes in land use on those erosional processes. This effort will also result in the cataloging of landforms developed on the Mancos Shale in the Gunnison Gorge National Conservation Area.
   
   
3. Documentation of the spatial distribution (background levels) of environmentally sensitive elements (ESE) and economically important elements in the Mancos Shale. The critical issues of metal and ESE sources, why elements are concentrated in some black shale sequences and not in others, the spatial and temporal distribution of elements (the geochemical framework), and the mineralogical residence of ESE will be addressed in this objective, which will provide much of the requisite data for the project’s modeling efforts.
   
   
4. Construction of a model describing pedogenesis of the Mancos Shale. This objective focuses on examining the quantitative movement of elements during the development of soil on the Mancos Shale, asking the questions of how and in what quantities are ESE and related elements concentrated or depleted in Mancos soils.
   
   
5. Comparison of the Mancos Shale with other black shale sequences. Understanding the genesis of black shale-hosted ore deposits and the distribution/bioavailability of potential toxicants is necessarily based on understanding the genesis of the multiple types of black shale.
   
   
6. Investigation of the selenium toxicity on fish populations in the Upper Colorado River Basin. Current selenium levels and historic levels in fish and river sediments will help to evaluate the modern and historic effects of selenium on the health of aquatic populations of the Colorado River and its tributaries.
   
   
7. Development of effective information transfer and visualization methodologies. Visualization of scientific information in a manner that permits the user to rapidly and effectively assimilate complex results will be used not only to communicate with stakeholders, but will also be used as a research tool for modeling landscape evolution.

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Relevance and Impact

Responsible stewardship of lands is a primary goal of many Federal, State, and local government agencies as well as non-government organizations and citizen groups. In western Colorado and eastern Utah, much of that land is underlain by the Cretaceous Mancos Shale. During the last few decades, land-use and water-quality issues related to Mancos Landscapes have risen in prominence in the West Slope area of Colorado and parts of eastern Utah. Many immediate issues of concern to land managers are related to specific toxicants such as selenium and salinity. Scientifically defensible information is required by land managers in order to formulate responsible land-use management policies. Responsible stewardship and assessment of mineral and energy resources is also a primary goal of many organizations, including the USGS. To those ends, understanding the processes responsible for the concentration/dispersion and spatial distribution of environmentally sensitive elements (ESE) and economically important elements in the Mancos Shale is imperative.Such an understanding will help the appropriate organizations formulate policy to alleviate problems that result in a variety of negative impacts, several of which are within the purview of legislative actions. Currently, the primary problem is the salinity of the Colorado River, which results in an annual cost of approximately 330 million dollars (U.S. Department of the Interior, 2001). Apparently more than half of the salt load originates in the Upper Colorado River Basin and a significant portion of that load can be related to Mancos Shale landscapes.

Selenium (Se), thought to originate from the Mancos Shale, has lead to non-compliance with the Clean Water Act of portions of the Uncompahgre River, and tributaries (originating in the Grand Valley) of the Colorado River, resulting in the mandate that Se loading be reduced. Additionally, the Se is suspected of being a contributing cause of reduced populations of several endangered native Colorado fish species. Improved understanding of metal and ESE sequestration in black shale sequences will help improve national and global assessments of mineral and energy resources. Large areas of the United States are underlain by black shale, some of which have been exploited for energy resources and to a limited extent for mineral resources. However, new concepts on the genesis of world-class, black shale-hosted mineral deposits, coupled with this project’s anticipated contribution to understanding metal sources and the processes responsible for metal sequestration will facilitate improved mineral resource assessments. Further, an increased understanding of ESE and other trace element dispersion processes and the resulting geochemical patterns will aid in mineral exploration, resource assessment, and environmental assessments of black shale landscapes.Much of this project’s work directly addresses the expressed needs of USGS science programs, data/information gaps and requests for input by the BLM, BOR, USFWS, the Colorado River Basin Salinity Control Program, and the Gunnison Basin Selenium Task Force.

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Strategy and Approach

There are several elements to our approach directed toward integrated systems analysis. Multiple systems (biologic, hydrologic, atmospheric, and geologic) combine to produce the landscapes that develop over black shale. Typically, studies examine only small parts of those multiple systems. We propose to look at the most critical elements of those systems and to examine processes that operate at the interfaces between the disciplines.These critical elements include:

1. A balance between programmatic science needs and stakeholder needs. In most cases, this will require compromises that may necessitate conducting research in a geologic area that is less than optimal and/or focusing research efforts on issues that would not be the highest priority in an efficient, highly focused, research effort. For instance, the Mancos Shale is not the ideal unit to study in order to understand ore-forming processes. However, it is of great interest to a variety of Federal agencies and non-governmental organizations (NGOs) because of the environmental problems caused by selenium and large quantities of salts that are mobilized from the shale. The information that we need to understand the weathering history and processes will also help us understand why economic concentrations of metals have apparently not formed in the Mancos. That will help us define a set of criteria that may classify Mancos-like shale units as having a low potential for hosting syngenetic mineral deposits. Further, our increased understanding of processes will be applicable to other black shale landscapes.
   
   
2. Create a multidisciplinary (cross-discipline, cross-program), multiagency, cooperative effort to understand a variety of landscapes (geochemical, botanical, etc) that develop on black shale. Many of the issues of concern to land management agencies and NGOs require cross-disciplinary studies that require Bureauwide cooperative work. Part of this project will be a continuation of the existing cooperative effort between the USGS and BLM in which we are jointly defining research goals that will be of immediate use to managers overseeing Mancos Shale landscapes. Some of the proposed research will be dependent on funding from other agencies. A portion of the project will be dedicated to developing those funding sources.
   
   
3. Implement a multiple scale approach ranging from global, through major basin, to microscopic. The global and continental context of the Cretaceous ocean and North American seaway will provide the large-scale framework for the Mancos Shale depositional system. Detailed study of features and processes present or operating in parts of the Gunnison Gorge National Conservation Area will provide the necessary background and opportunity to build process models that can be used to evaluate other black shale landscapes.
   
   
4. Compare and contrast two black shale sequences with different tectonic and depositional settings. Such comparisons will assist in distinguishing between processes that may be locally important as opposed to those that are more likely to be universal. The Cretaceous (with emphasis on the Mancos) of the western United States will make a good comparison to the metalliferous and ESE rich early Paleozoic shales of the western United States.
   
   
5. Develop models that can be used to (a) evaluate the mineral potential of black shale landscapes and (b) assess the environmental (natural and anthropogenic) issues that may be related to those landscapes. The models will be a mix of empirical and theoretical.
   

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