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Trace of Main Displacement Surface (Bedrock/Basin Fill Contact) of Pirate Fault Zone, West Flank of Santa Catalina Mountains, Pima and Pinal Counties, Arizona

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Author
Dickinson, William R.
Issue Date
1994-12-01
Keywords
Arizona Geological Survey Contributed Maps
Tertiary
Pinal County
Arizona
Pima County
Santa Catalina Mountains
map
Geology
Pirate Fault

Metadata
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Citation
Dickinson, William R., 1994, Trace of Main Displacement Surface (Bedrock/Basin Fill Contact) of Pirate Fault Zone, West Flank of Santa Catalina Mountains, Pima and Pinal Counties, Arizona: Arizona Geological Survey Contributed Map CM-94-G, map scale 1:24,000, 10 p. and 1 map sheet.
Publisher
Arizona Geological Survey (Tucson, AZ)
Description
The Pirate fault is a basin-range normal fault that separates footwall bedrock of the Santa Catalina Mountains on the east from downfaulted Neogene basin fill underlying Oro Valley, which forms a sedimented corridor to the west between the Santa Catalina and Tortolita Mountains (Pearthree and others, 1988). According to both McCullough (1963) and Budden (1975), this basin-margin, range-front structure was first termed the Pirate fault by Wallace (1954), although his own thesis makes no explicit claim for originating the nomenclature. The trend of the fault is northeasterly at the foot of Pusch Ridge near Tucson, but swings to nearly due north along the range front north of Catalina State Park. In detail, the structure is a complex fault zone, with brecciation and complex fracturing of varying intensity present for 100-200 m into footwall bedrock (Davis and others, 1994). By contrast, offset basin fill forming the hanging wall is little deformed, at least at exposed horizons. The contact between faulted basin fill and variably deformed bedrock is a thin gouge seam, only 1-5 cm thick, that dips consistently at angles of 50-55 degrees beneath Oro Valley. This contact is here inferred to be the main displacement surface of the Pirate fault zone, and its trace is the feature plotted along the trend of the fault. Adjacent to the gouge seam in the footwall is a cohesive sheet of compact fault breccia, composed of crushed bedrock and typically 4 m thick (Davis and others, 1994).
URI
http://hdl.handle.net/10150/630693
Additional Links
https://library.azgs.arizona.edu/
Language
en
Series/Report no.
CM-94-G
Rights
Arizona Geological Survey. All rights reserved.
Collection Information
Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu.
North Bounding Coordinate
32.6
South Bounding Coordinate
32.35
West Bounding Coordinate
-110.95
East Bounding Coordinate
-110.85
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