Book Review: Ancient Landscapes of the Colorado Plateau

Title: Book Review: Ancient Landscapes of the Colorado Plateau, by Ron Blakey and Wayne Ranney. Grand Canyon, AZ: Grand Canyon Association, 2008

Reviewed by: Mark Longman

Publication: The Outcrop, June 2009, p. 13, 23, 25

Many geologists have used the beautiful paleogeographic maps created by Ron Blakey, a professor at Northern Arizona University, over the past 20 years and available for free over the Internet at links available at http://jan.ucc.nau.edu/-rcb7/RCB.html. They are works of art created after hours of careful geologic research that capture in amazing detail images from times long past when seas, dunes, rivers, and floodplains now long gone covered the Rocky Mountain landscape. Sediments deposited in these highly variable environments have now converted to diverse and often colorful lithologies that offer some of the most amazing scenery in the country as well as a wealth of natural resources.

Through much of the 1990s and into the early 2000s, Ron struggled to compile his maps into book form so that readers could have at their fingertips a comprehensive record of the paleogeographic evolution of the Colorado Plateau and southern Rocky Mountain region. Unfortunately for Ron, the construction of the maps proved far easier than preparing the text that would bind the maps together into an unfolding saga of the area’s complex geologic history. Fortunately for Ron, one of his former students, Wayne Ranney, had turned a passion for geology that began in Ron’s courses at NAU into a career as a geologic interpreter, professional writer, and educator at Coconino Community College in Flagstaff. Ron welcomed the help when Wayne suggested a collaborative effort to get Ron’s book published. Together, Ron and Wayne have turned out what is one of the finest, most comprehensive, easily readable and beautifully illustrated geologic histories of the Rocky Mountain region since RMAG published its “Big Red Book,” the Geologic Atlas of the Rocky Mountain Region, in 1972.

Ancient Landscapes begins with a foreword by William R. Dickinson and prefaces by the authors explaining how the book came to fruition. It then has chapters on the Proterozoic and each era of the Phanerozoic that contain 70 global and regional paleogeographic maps for time periods ranging from 1,750 million years ago to 100 million years into the future. Global maps contain faint outlines of the states and provinces in North America that facilitate orientation. Regional maps center on the Four Corners area of the Colorado Plateau and contain both state and county outlines that provide clues to the meticulous research and level of detail that Ron put into creating his maps. The discussion of these maps is rounded out with beautiful outcrop photos, other geologic features (fossils, etc.), and schematic cross-sections on which the various formations of a particular area are clearly labeled.

Of course, Ron is the first to admit that creating the maps is complicated by the complex rock record with major eroded intervals, deeply buried sections far removed from our sight, and the vagaries of rivers and shorelines that migrated long distances through the brief span of time represented in each map. Still, based on my 25+ years of working with rocks in the Rocky Mountain region, I found Ron’s maps to be amazingly consistent with my own interpretations made in areas ranging from the Paradox Basin to southern Wyoming.

The strongest part of the book deals with the Jurassic and Cretaceous periods because rocks of these ages are so superbly exposed on the Colorado Plateau and have been a focus of research by both Ron and Wayne. Parts of these periods are represented by maps showing the paleogeographic changes every 5 million years. These maps clearly reveal how quickly things changed regionally through time. Encroachment of both the Jurassic sea into Utah and the Cretaceous Western Interior Seaway onto the Colorado Plateau are particularly well illustrated along with their adjacent sedimentary facies. Insightful text ties these maps into context and is surprisingly free of complex geologic jargon so it should be easily understood even by non-geologists.

The book concludes with chapters on the geologic evolution of the Colorado River system in the late Cenozoic, which has been a focus of Ranney’s research over the past decade, and the significance of the Grand Staircase, a section of rock exposed from the bottom of the Grand Canyon to the rim of Bryce Canyon that ranges in age from the Lower Proterozoic (1750 million years old) to the Upper Cenozoic (<1 million years ago) over a straight-line distance of <100 miles. This “Grand Staircase” was named by Clarence Dutton in the early 1880s and remains one of the best exposed and most complete stratigraphic columns in the world, lacking only rocks of Ordovician and Silurian age. The final chapter of the book is entitled: “Where to see the Rocks” and provides brief geologic descriptions of the most spectacular geologic outcrops on the Colorado Plateau including the many national parks (Zion, Bryce, Canyonlands, and Arches to name a few) and National Monuments (Canyon de Chelly, Colorado, etc.) in the area.

Following the text is an appendix that explains in some detail how Ron created his paleogeographic maps, a glossary of key geologic terms, an adequate but far from comprehensive reference list, and an index that makes it easy to find specific items referred to in the text. For those interested in better understanding the geologic history of the Colorado Plateau, there is no finer reference than this beautifully illustrated masterpiece created by Ron and Wayne. They deserve high praise for thoroughly integrating so many diverse and detailed geologic studies into an elegant and easily understood story of one of the world’s great geologic treasure troves.

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