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The Holocene and Pleistocene vegetation history of the Grand Canyon

The Grand Canyon from a helicopter over the Colorado River (75 k jpg image).

Principal Investigator:
Kenneth L. Cole, USGS Colorado Plateau Research Station

Summary:
The ice age (Pleistocene) vegetation of the Grand Canyon has been determined through the analysis of plant fossils preserved in caves and fossil packrat middens. The past zonation of vegetation along the Colorado River form the Gulf of California to the state of Colorado has been reconstructed from these fossil deposits During the ice ages, plants escaped colder climates by  growing at then-wetter sites about 2500 feet lower than they do today.    Only the most extremly arid deserts, those now with less than 4 inches of rain per year, supported desert during the ice ages.  Most North American deserts were occupied by woodlands of juniper and/or pinyon pine. 

Figure showing the elevational zonation of plants over the last 30,000 years along the Colorado River. Light blue dots are packrat midden records. (175 k gif image)

About ten thousand year ago, the ice ages ended and the Holocene era began.  The vegetation history and development of modern plant communities during the Holocene are not yet well understood because of the large changes occurring as the climate warmed and plant species migrated upward and northward toward their modern distributions.   This project is now reconstructing the Holocene history of vegetation in the Grand Canyon and elsewhere on the southern Colorado Plateau.  Knowledge of the past vegetational response to major warming is required to estimate the future response of vegetation to global warming.

Comparative photos of a Grand Canyon research site today and a reconstructed image of how it looked during the ice age (200 k jpg image)

 

Photo of Novinger Butte in Grand Canyon

Outcrops of Tapeats Sandstone and Redwall Limestone in the Nankoweap Basin where fossil packrat middens are abundant. (100 k jpg image)  

 

Photo of arid desert near Yuma, Arizona

Picacho Peak, California.   Hyperarid areas such as this along the lower Colorado River supported desert throughout the ice ages.   The foreground of this 1978 scene is now a leaching field from a gold mine. (126 k jpg image)

Publications:
Cole, K. L. 1982. Late Quaternary zonation of vegetation in the eastern Grand Canyon. Science 217:1142-45. Cover Photo (220k), Solution sculpture in the Redwall limestone.

Cole, K. L. 1985. Past rates of change, species richness, and a model of Vegetational Inertia in the Grand Canyon, Arizona. American Naturalist 125:289-303.

Cole, K. L. 1986. The lower Colorado Valley: A Pleistocene Desert. Quaternary Research 25:392-400. (Abstract)

Cole, K. L. 1990. Reconstruction of past desert vegetation along the Colorado River using packrat middens. Palaeogeography, Palaeoclimatology, and Palaeoecology 76:349-66. (Abstract)

Other Grand Canyon Sites:

Ken Cole's home page

Colorado Plateau Research Station home