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Geologic Map of Organ Pipe Cactus Natl Monument

Organ Pipe Cactus National Monument: Geologic Resource Report

The U.S. National Park Service just released a comprehensive ‘Geologic Resources Inventory Report’ for Organ Pipe Cactus National Monument, Arizona. USA. The 104-page report by Katie KellerLynn (Colorado State University) includes 32 figures and 3 tables, and links to GIS database(s) of geologic mapping of the monument.

Organ Pipe Cactus National Monument (~ 517 sq. miles) is located in the Basin and Range Province of southwestern Arizona, adjacent to the U.S.-Mexico frontier. In 1937, President Franklin D. Roosevelt issued a Presidential Proclamation establishing the monument in order to preserve a pristine section of the Sonoran Desert Habitat. Ninety-Five percent of the monument is set aside as ‘wilderness’ area. The rugged monument landscape accommodates six mountain ranges: Bates Mountains, Cipriano Hills, Quitobaquito Hills, Puerto Blanco Mountains, Diablo Mountains, and Ajo Range, and parts of four others, Growler Mountains, Sonoyta Mountains, Sierra de Santa Rosa, and Gunsight Hills.

From the Executive Summary, “the monument is a geologic place. Some of the oldest rocks in Arizona are preserved just north of the monument; these rocks record 1.7 billion years of geologic time. The monument’s bedrock and other geologic features record about 200 million years of Earth’s history, including building of the North American continent, rising of the Rocky Mountains, stretching of the Basin and Range, eruption of the Ajo volcanic field, and filling of valleys, referred to as “basins,” with sediment.”

Select Chapter Headings
   •    Geologic Heritage   p. 5 - 20
   •    Geologic History, Features, and Processes   p. 21 - 52
   •    Geologic Resource Management Issues   p. 53 - 66
   •    Guidance for Resource Management   p. 67 – 76.

“Geologic Reconnaissance at Organ Pipe Cactus National Monument, Arizona” by Skinner, Haxel, and Umhoefer (2008), is the chief geologic map used in evaluating the geologic setting of the monument. To view/download the geospatial database, geologic map legend, lithologic descriptions, and correlation diagram of Organ Pipe Cactus National Monument


Background.  National Park Service’s objective with their ‘Resources Inventory’ reports: “… to fulfill the mission of the National Park Service (NPS) requires an accurate inventory of the geologic features of a park unit, but park managers may not have the necessary information, geologic expertise, or means to complete such an undertaking; therefore, the Geologic Resources Inventory (GRI) provides information and resources to help park managers make decisions for visitor safety, planning and protection of infrastructure, and preservation of natural and cultural resources.”

Citation: KellerLynn, K. 2022. Organ Pipe Cactus National Monument: Geologic resources inventory report. Natural Resource Report NPS/NRSS/GRD/NRR—2022/2399. National Park Service, Fort Collins, Colorado.

Skinner, L. A., G. Haxel, and P. J. Umhoefer, 2008, Geological reconnaissance at Organ Pipe Cactus National Monument, Arizona (scale 1:24,000). Unpublished digital data. Northern Arizona University, Flagstaff, Arizona.