Geology and Paleontology of Red Rock Canyon
(by David P.Whistler)

Red Rock Canyon is a natural geologic classroom where the rocks in the picturesque cliffs offer a glimpse into a rich and diverse past history. Miles and miles of deeply eroded rock exposures in an arid setting, with little vegetation to obscure the view, yield an unparalleled opportunity to delve deeper into this history.

Discovery of fossils early in the last century, and on-going collecting by Natural History Museum parties over the past 50+ years, has yielded the richest record of this ancient plant and animal life in western North America. Coordinated studies by geologists, paleontologists, geophysicists, and evolutionary biologists have made the rocks and fossils in this area a standard of comparison for similar-aged occurrences throughout North America.

The rocks in the Red Rock Canyon area reveal some of the 500 million-year history of this part of North America. Of greatest interest to the Natural History Museum paleontologists is a nearly mile-thick succession of fossiliferous rocks that geologists call the Dove Spring Formation. These deposits are composed of stream sediments, lake clays, lava flows, and volcanic ashes that were laid down layer by layer in an ancient valley that long ago disappeared. Pressure from successive overlying layers turned the sediments into stone. Pollen, leaves and wood from ancient plants, and the bones of ancient animals were trapped in these sediments and became the fossils we study today. Earthquake movement along a nearby earthquake fault subsequently elevated and tilted the entire area that was once a valley. As uplift slowly progressed, erosion continuously stripped away the hardened deposits. More resistant beds produced the cliffs and badlands that are today found in Red Rock Canyon.

Geologic studies reveal sources in the eastern Mojave Desert for the ancient lava flows in the Dove Spring Formation and sources for volcanic ashes as far away as Yellowstone. Geophysical age-dating studies, using naturally occurring radioactive isotopes trapped in the volcanic beds, determine an age range for the fossil-bearing deposits from 12.5 to 7.5 million years ago. Studies of the alternating magnetic polarity preserved in the sediments and linking of volcanic ash deposits to sources of known age provide independent confirmation of this age range.

Paleontologists have already recognized more than 100 different extinct plants and animals among the thousands of recovered fossils from the Dove Spring Formation. Pending studies of fossil pollen will greatly enrich knowledge of the ancient plants. Ongoing studies regularly recognize new animals. Studies of naturally occurring carbon isotopes preserved in the teeth of fossil horses and microscopic studies of cell structure preserved in petrified stems have revealed the earliest spread of sub-tropical, arid adapted grasses. Precise geologic mapping coupled with geophysical age dating permits paleontologists to determine age differences between each fossil discovery. This information allows precise tracing of evolutionary changes within groups of fossil animals over millions of years. Comparisons of fossils from the Dove Spring Formation with animals as far away as Asia have traced ancient migrations between the continents. Comparisons of fossil plant and animal assemblages with similar modern associations yield reconstructions of ancient environments. Studies of radioactive isotopes in the ancient soils preserved in the Dove Spring Formation will provide independent confirmation of these paleoecologic interpretations. Together, these trace the changing past environments that were one of the most likely forces for evolutionary change.

The scientific studies in Red Rock Canyon by Natural History Museum professional staff and scientific associates have revealed a wonderful picture of rich and diverse life far different than anything one could encounter in the world today. New findings regularly emerge. Come join us in this great adventure and learn how each new discovery adds to the ever-expanding knowledge of a long-ago disappeared world.

For further reading and reference see Field guide by David P. Whistler