The McDowell Mountains are a northwest-southeast trending range
composed of 1.4 Ga (Giga-annum, or 1400 million years old) granitoid
rocks located at the northern, eastern, and southern portions of the
mountains. The range occupies a significant portion of northeastern
Scottsdale, Arizona.The central portion of the range is composed of
Proterozoic quartzites and metavolcanic rocks generally thought to be
part of the Alder Group, a package of rocks 1.70-1.71 Ga old. The
youngest rocks in the McDowell Mountains consist of Tertiary volcanics
and conglomerates.The mountains were formed as part of the Basin and
Range extensional event which took place in central Arizona between 5
and 20 million years ago. The uplift and erosion of the mountains has
led to the formation of extensive alluvial fans along the northeastern
and southwestern faces which have been the focus of intense development
over the past few years.
Previous work in the McDowell Mountains has focused primarily on
the environmental geology of the range, with the majority of the work
performed by Emeritus Professor of Geology Troy Pewe and several of his
students here at ASU.
Selected References
Christenson, G.E. (1976) Environmental geology of the
McDowell Mountains area, Maricopa County, Arizona: Part I. Unpublished
MS Thesis, Arizona State University, Tempe, AZ.
Welsch, D.G. (1977) Environmental geology of the McDowell Mountains area,
Maricopa County, Arizona: Part II. Unpublished MS Thesis, Arizona State
University, Tempe, AZ.
The NASA-ASU-City of Scottsdale research consortium has
allowed a great wealth of remotely sensed data to be collected for the
McDowell Mountains and surrounding areas. The available datasets include
visible and near-infrared (Landsat, NS001, ATLAS), thermal infrared
(TIMS, ATLAS), and radar (SIR-C, AIRSAR) that have a variety of ground
resolutions ranging from 3 to 30 meters.
Each of these datasets can provide information about specific aspects of the
surficial and bedrock geology of a region such as surficial particle sizes,
rock composition, vegetation and soil types, and slopes depending on the wavelength
region covered. The research of geology graduate student Will
Stefanov focuses on the combined use of these different datasets to address
applied field geology problems in the McDowell Mountains. A significant amount
of time is spent in the field to ground truth images and to collect rock and
soil samples for spectral analysis in the laboratory. Observations of field
relations and laboratory spectra are used to further refine image processing
techniques in an iterative fashion.
Another expected result of research performed in the above areas is the determination of the best combinations of data and image processing techniques toobtain such information as bedrock lithology, soil types and distribution, vegetation distributions, etc. This information could then be used to produce a sensing and processing package for use by land use planners, city managers, conservationists, and environmental managers that could be integrated with a GIS (Geographic Information System)
.
An integral part of the ongoing (and proposed) geologic research in the McDowell Mountains is the extraction of useful information from the various datasets available at ASU. Part of the research effort is concerned with evaluating different processing schemes to determine which are most useful for a given field problem. Common image processing techniques include various image stretches, construction of band ratios, principal component analyses, and the construction of false-color images using different band combinations. Processed images can then be fused together, and other datasets (like topographic maps, digital elevation models, and GIS information) can be added to maximize the information displayed. Commercially available software packages, such as ERMapper® and ArcInfo®, are used for image processing tasks in the Thermal Emission Spectrometer Laboratory at ASU.