The Mount Baker 30- by 60-minute quadrangle encompasses rocks and structures that represent the essence of the geology of the North Cascade Range . The quadrangle is mostly rugged and remote and includes much of the North Cascade National Park and several dedicated wilderness areas managed by the U.S. Forest Service. Geologic exploration has been slow and difficult. In 1858 George Gibbs (1874) ascended the Skagit River part way to begin the geographic and geologic exploration of the North Cascades. In 1901, Reginald Daly (1912) surveyed the 49th parallel along the Canadian side of the border, and George Smith and Frank Calkins (1904) surveyed the United States' side. Daly's exhaustive report was the first attempt to synthesize what has become an extremely complicated geologic story.

Modern geologic work began almost a half a century later when, in 1948, Peter Misch began his intensive study of the North Cascade Range (Misch, 1952, 1966). His insights set the stage for all later work in the North Cascades. Considerable progress in understanding the North Cascades in light of modern plate tectonic theory has been made by E.H. Brown and his students. We have used much of their detailed geologic mapping. Although our tectonic reference frame has changed much with the recognition of plate tectonics and exotic terranes, Misch's observations prove to be remarkably accurate.

Our work in the Mount Baker quadrangle began in 1983 as part of a project to map and compile the geology of the Wenatchee and Concrete 1 X 2 degree quadrangles at 1:100,000 scale, work that we began in 1975. We have mapped in cooperation with the Division of Geology and Earth Resources, Washington Department of Natural Resources. We have also benefited by the cooperation and helpfulness of the National Park Service and the U.S. Forest Service.

Acknowledgments

Many people have helped with field work in the difficult terrain of the Mount Baker quadrangle: Michael Ort (1984 1985), Patrick Goldstrand (1985), Carolyn Ortenburger (1985 1986), Janet Slate and Robert Fillmore (1986), Kathleen Duggan (1987 1988), Scott Spees (1987), Eric Roth (1988), Kris Alvarez (1990 1991), Tom Grundy (1990), Carmello Ferlito, David Maher and Jim Montgomery (1991), Chad Nelsen, Cathryn Dwyre, and Rob Osborn (1992). Keith Howard constructively reviewed the manuscript. Many employees of North Cascades National Park and the Mount Baker Ranger District of the U.S. Forest Service have been helpful, in particular Craig Holmquist, Kevin Kennedy, Jerry Lee, and Bill Lester; Jon Reidel has been particularly helpful. We are thankful that superb and ultimately cooperative helicopter pilots and their crews exist; thank you Tony and Sue Reese for our success and our safety.

We have discussed the geology of the map area with many. In particular we have enjoyed extended and sometimes heated discussions with Derick Booth, Mark Brandon, Darrel Cowan, Joe Dragovich, Bob Miller, the late Peter Misch, Jim Monger, John Reidel, John Stacy, Jeff Tepper, and Joe Vance. Darrel Cowan, Derek Booth, and Bob Miller made many helpful suggestions for improvement of map and text.

R.W. Tabor produced the Mount Baker digital geologic map with GIS technology using Alacarte (Wentworth and Fitzgibbon, 1991). Many computer and(or) GIS experts helped, especially Tracey Felger, Todd Fitzgibbon, Patricia Helton, Eric Lehmer, Bob Mark, Chad Nelson, Geoff Phelps, and Pahdy McCarthy. Many thanks to Carl Wentworth, who, no matter how busy, always answered questions about Alacarte.