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U.S. Geological Survey Map I-2592 (in press)

by R.W. Tabor, D. B. Booth J. A. Vance, and A. B. Ford

Generalized geologic map of the Sauk River Quadrangle modified from Open-File Report 88-692.
Click here for enlarged version with explanation(68K).

Thumbnail of generalized geololgic map of the Sauk River quadrangle


When I.C. Russell (1900) visited Cascade Pass in 1898, he began a geologic exploration which would blossom only after three-quarters of a century of growing geologic theory. The region encompassed by the Sauk River quadrangle is so structurally complex that when Misch (1952) and his students began their monumental studies of the North Cascades in 1948, the available geologic tools and theories were barely adequate to start deciphering the history. Subsequently, Bryant (1955), Danner (1957), Jones (1959), Vance (1957a), Ford (1959), and Tabor (1961) sketched the fundamental outlines of the geology of the Sauk River quadrangle.

Our work in this quadrangle began in 1978 and has continued through 1985. It is part of a major USGS goal to compile and map the entire Concrete 1 X 2 degree quadrangle at 1:100,000 scale.

Our field work was greatly facilitated by the assistance of Steven L. Garwin, Patrick Goldstrand, Kathleen Ort, Vicki Pease, Carolyn Ortenburger, Ron A. Sonnevil, Fred Zankowsky, and the late Carl Huie. We thank Michael Swanson, Fred Zankowsky, and especially Carolyn Ortenburger for office and laboratory services. Paleontologists who helped immensely by identifying deformed, commonly recrystallized, (and usually uninspiring) fossils are Charles Blome, William Elder, Anita Harris, David L. Jones, Jack. W. Miller, and Kate Schindler. Chuck Blome has been particularly helpful.

We thank John Whetten, Bob Zartman, and John Stacey and his staff for unpublished U- Pb isotopic analyses. Dennis Sorg provided clean mineral separates for K-Ar ages: Carolyn Ortenburger and Michael Ort extracted and analyzed most of the argon. P. Klock, S. Neil, T. Frigs, L. Espos, S. MacPherson, and M. Taylor analyzed the potassium. We have had fruitful discussions on the geology of the area and the North Cascades in general with Ned Brown, Bob Miller, the late Peter Misch, Greg Reller, Dave Silverberg, and John Whetten.

Most of our helicopter support was in the capable hands of Anthony Reese. We also thank the late Jack Johnson for his flying skill. U. S. Forest Service personnel at Darrington and Verlot have been helpful in many ways; we especially thank Howard Barstow, Janet DeRoco, and Fred Schaub.

Kathleen Duggan digitized the field map with aid of computer program GS-MAP.

Generalized geologic map of the Sauk River Quadrangle.
Click here for enlarged version with explanation(68K).

Thumbnail of generalized geololgic map of the Sauk River quadrangle

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