USGS Geological Research Activities with the U.S. Bureau of Land Management

Mancos Shale Landscape Studies

 

The Upper Colorado River Basin, a region underlain by black shale, poses a major challenge to land management agencies.  The issues include changing land use and the presence of potentially harmful concentrations of certain elements in the soils and water.  The USGS is conducting an interdisciplinary study, with multiple agency participation, of the Cretaceous Mancos Shale Landscapes.  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”, in which the two agencies are jointly defining research goals that will be of immediate use to managers overseeing the Mancos Shale landscapes.   

Black shale can be both a source of mineral wealth and a cause for environmental concern.  Oil and gas are the most obvious of the resources that originate in black shale; some of the world's largest mineral deposits are hosted by black shale; a variety of industrial minerals, such as clay and phosphate, are derived from black shale; and in certain environments, black shale derived soil provides necessary nutrients for specific crops and plant populations.  However, in addition to their economic and ecologic value, some black shale sequences are non-point sources for potentially toxic elements, such as arsenic, chromium, mercury, and selenium.

Portions of the Uncompahgre River (in the Gunnison Valley) and tributaries of the Colorado River in the Grand Valley have been identified with problems that are attributed to elevated concentrations of selenium and salinity of surface and ground water.  Selenium occurs naturally and is present in many sedimentary formations.  This element is required in trace amounts for human and animal health, but it can have adverse health problems for livestock, wildlife, and humans when ingested in higher-than-required concentrations.  The high selenium content in the region is known to have adversely affected fish and avian populations and the salinity has impacted agricultural lands, water delivery facilities, and water quality.  This region has become the focal point for the need for scientific information supporting sound land-use decisions.

The broad objectives of the Mancos Shale Landscapes project are 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
• Provide applicable, scientifically valid information that can be used to formulate resource and land-use management policies for Mancos Shale landscapes
• Assure that the information provided is applicable to black shale landscapes that are not specifically studied

This project addresses requests for information by BLM, Bureau of Reclamation, U.S. Fish & Wildlife Service, Natural Resources Conservation Service, the Colorado River Basin Salinity Control Program, and the Gunnison Basin Selenium Task Force.  The greatest concern for these land management agencies are erosional processes.  Development of a model describing the erosion of Mancos Shale will enable understanding of the processes that result in the physical and chemical erosion of the Mancos Shale and the affects of changes in land use on those erosional processes.

The USGS personnel have been working closely with BLM's Gunnison Gorge National Conservation Area and Uncompahgre Field office personnel for more than 2 years on various aspects of the project. 

The products from this research include datasets related to erosion rates, soil characteristics, run-off estimates, and geochemical analysis of rock and soil samples. The project is scheduled for completion in FY 2007.