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Grand Canyon geological mapping
(This material a duplicate of this article, which is PROD)



Grand Canyon geological mapping fulfills formal requests from the National Park Service, Bureau of Land Management, and US Forest Service This project addresses a critical resource management question in the Grand Canyon Region: how might increased ground water development adjacent to the Grand Canyon affect the surface and spring flows? Faults, fractures, and rock layers strongly influence the flow paths of groundwater. Geologic mapping helps hydrologists to identify the structural features, or geologic framework, controlling that flow. Additionally, threatened or endangered plant and animal species are a concern that pertain to water issues.

Overview
In the last few years, predictions of severe water shortages in northern Arizona and water rights issues led the National Park Service to identify ground-water investigations in and near Grand Canyon National Park as a high priority for USGS research. Additionally, these investigations are being used by the Bureau of Land Management, and U.S. Forest Service.

Springs and seeps discharging from the Redwall - Muav aquifer along the south rim of the Grand Canyon support wildlife and riparian zones. Because water is also a vital component of human activities, the cities of Flagstaff, Williams, and Tusayan, and private entities like Canyon Forest Village are, or have been, considering pumping ground-water from the regional aquifer. The National Park Service has asked USGS for help in assessing whether increased ground-water development adjacent to the Grand Canyon might affect surfaces and spring flows. The members of this project are mapping the rock units and geologic structure of the Grand Canyon region. These physical features underpin the regional groundwater flow system. The geologic mapping investigations are part of an interdisciplinary USGS effort to develop a better understanding of ground-water flow in the region.

Endangered plant and animal species
A secondary, but nevertheless important, management concern on the Colorado Plateau is the identification of the areas with highest probability that support threatened or endangered plant and animal species. One success of this project so far has been the realization by NPS, USFS, and USGS biologists that the habitats of some rare, threatened, or endangered species, such as the Mexican spotted owl and rare cacti, have geologic controls that can be used to predict species distribution. Project geospatial databases are being combined with biological data for predictive purposes.

Current and proposed investigations
To address the area of greatest need for geologic framework related to regional water management issues, the USGS began new mapping along the south rim of the Grand Canyon. The mapping was requested to provide critical structural information for analysis of geologic controls on groundwater movement and spring discharge. Recharge and discharge areas of the regional aquifer are known to be concentrated along faults and fractures. Geologic mapping of 32 7.5 (1:24,000) minute quadrangles within the Valle 30' x 60' (1:100,000) quadrangle along the south rim of the Grand Canyon is largely completed and GIS production has begun. The proposed new geologic map of the Cameron 30' x 60' (1:100,000) quadrangle is southeast of the Grand Canyon quadrangle and east of the Valle quadrangle.

Grand Canyon maps
The geologic mapping in the Grand Canyon region fulfills formal requests from the National Park Service, Bureau of Land Management, and US Forest Service. Thus far, project members have produced three new digital geologic maps of the Grand Canyon area: the Grand Canyon 30' x 60' quadrangle, Arizona (Billingsley and Hampton, 2000), Mount Trumbull 30' x 60' quadrangle, Arizona (Billingsley and Wellmeyer, in press), and Peach Springs 30' x 60' quadrangle, Arizona (GIS work in progress). Together they encompass about 6,000 square miles of the Grand Canyon and vicinity.

Pipe Spring National Monument
Pipe Spring National Monument, in the northernmost part of central Arizona, is an oasis in an arid landscape. Its springs have played a part in the history of the American Indians, early explorers, and Mormon pioneers. The Monument lies within the boundaries of the Kaibab Indian Reservation.

National Park Service News Release on March 27, 2002 states, "Over the past forty years, spring flow from the main spring (Pipe Spring) gradually diminished, and in the summer of 1999, the spring beneath Winsor Castle stopped producing water. Two other water-producing features on the Monument continued to flow.... The decline in spring flow has resulted in a series of hydrological research projects aimed at increased understanding of the Pipe Spring groundwater aquifer".

Groundwater flow
The geologic framework of the region strongly controls groundwater flow. As part of a National Park Service and USGS partnership, USGS scientists are mapping the bedrock, surficial, and structural geology of the Monument and its environs. Four 7.5-minute (1:24,000) quadrangles comprise the mapping area: Pipe Valley, Pipe Spring, Moccasin, and Kaibab quadrangles. They will be mapped to USGS standards with emphasis on the local character of the Navajo Sandstone and Kayenta Formation, their contact, and the structures associated with the Sevier fault system. The geologic mapping and compilation will take three years, beginning in Fiscal Year 2003. This task represents one piece of an interdisciplinary USGS effort to develop a better three-dimensional understanding of the pathways for groundwater movement to the springs, and the vulnerability of the springs to groundwater extractions. The geologic mapping complements proposed high resolution seismic profiling of features below the surface such as fracture zones, jointing, and water tables.

Tassi and Pakoon Springs
The NPS and BLM have been concerned for some time that increasing groundwater development near the communities of Mesquite, Nev., and St. George, Utah, could potentially affect the quantity and quality of groundwater discharging from Tassi and Pakoon Springs. To address this concern the NPS requested that the U.S. Geological Survey (USGS) conduct a technical evaluation of existing water-quality/chemical data, hydrologic data, and geologic maps to identify any gaps that would hinder defining the regional hydrogeology in relation to the flows at Tassi and Pakoon Springs.

Tassi Spring supports the rare endemic Grand Wash Spring snail, and the riparian area provides habitat for a diverse bird population and a protective haven for local mammals in the Mojave Desert. Pakoon Springs can potentially provide an oasis of high biologic diversity and productivity in the surrounding landscape of the arid desert. After the closure of the Pakoon Springs Ranch the springs, riparian areas, and agricultural fields had been overrun by nonnative, invasive floral and faunal species. Then, from approximately 2002 to 2011, the BLM, with help from Grand Canyon Wildlands Council and others, removed all the structures and restored the landscape to approximate conditions that likely existed before the establishment of the ranch.

Geologic map of Lake Mead
Lake Mead, on the Colorado River in the states of Nevada and Arizona, was formed by the Hoover Dam. Field mapping and digital compilation are complete for the Lake Mead (30x60-minute, 1:100,000) quadrangle. A preliminary version of the Lake Mead National Recreation Area geologic map was produced a few years ago; this task will allow updating with new mapping that was undertaken for the 1:100,000-scale map. In addition, USGS geologists will work with the Lake Mead Recreational Area Resource personnel to customize the map database to work with an Arc View interface called Geographical Information Systems (GIS) Theme Manager (see below). The NPS Geologic Resources Division uses GIS Theme Manager to display and manipulate digital information, including geology, and is encouraging resource units at different NPS units to incorporate Theme Manager into their daily activities.

GIS Theme Manager
The NPS Theme Manager was developed to provide GIS administrators a method of organizing, managing and presenting large amounts of GIS data to users of ArcGIS. It is intended as an alternative to the "file based" ArcCatalog method of data management. Theme Manager uses an MS Access Database to connect together datasets, linked documents, symbology, and display settings in a hierarchical structure while not affecting the underlying data storage structure. Theme Manager is a standalone application that can be launched from an ArcMap toolbar or from the Windows Start Menu. Themes (aka data layers) are organized hierarchical structures called lists, for quick and easy browsing and access. Users can create theme lists to use or share with others, or access theme lists developed by data managers. Theme Manager was developed by Greg Daniels of the Alaska Regional Office of the National Park Service.