Geologic map of McDowell Mountains, central Arizona

/ 23 May 2018 / 0 Comments

The 1:12,000 scale geologic map of the McDowell Mountains in south-central Arizona, Maricopa County, represents more than 10 years of work by Steve Skotnicki - see figure 1 below. The map area is 184 square kilometers and consists of 13 major groupings of rock units, including 86 individual map units. Most of the rocks are Early and Middle Proterozoic metamorphic rocks. Two Middle Proterozoic thrust faults cut the rocks and juxtapose a 10-km-thick sequence of quartzites and ash-flow tuffs on top of a 2-km-thick sequence of fine-grained and coarse-grained quartzites at the northwest end of the mountain range. The metamorphic rocks have been intruded by at least three different granites, the largest of which is the ca. 1425 million-year old Carefree granite to the north.

The newly released tablet/laptop map version includes: a correlation of geologic map units; two cross sections; and two dozen photographs of geologic units and features that outcrop there.

New Tablet or Laptop map version: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1890

Smart phone map version (2016) http://tinyurl.com/GeoMap-McdowellMtns

The map was originally hand-drawn by Steve. With support from McDowell Sonoran Conservancy (MSC) and some oversight by Arizona Geological Survey, the map was digitized by MSC volunteers between 2016 and 2017. Map digitization by Bobby Alpert, Marjorie Gillis, Dan Gruber, Con Englehorn, Franco Farina, Jim Frier, Tom Hartley, Ralph Lipfert, John McEnroe, Peggy McNamara, and Brian Munson; Technical oversight by Dan Gruber, Melanie Tluczek, and Brian Gootee. The map consists of 3,199 individual mapped polygons separated by a total of 2,221 km of contact lines separating all geologic map units. There are 15 different types of orientation points totaling 2,983 individual data points. Brian Gootee created the final layout for this map.